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Sample records for aerosol assisted chemical

  1. Development of aerosol assisted chemical vapor deposition for thin film fabrication

    Science.gov (United States)

    Maulana, Dwindra Wilham; Marthatika, Dian; Panatarani, Camellia; Mindara, Jajat Yuda; Joni, I. Made

    2016-02-01

    Chemical vapor deposition (CVD) is widely used to grow a thin film applied in many industrial applications. This paper report the development of an aerosol assisted chemical vapor deposition (AACVD) which is one of the CVD methods. Newly developed AACVD system consists of a chamber of pyrex glass, two wire-heating elements placed to cover pyrex glass, a substrate holder, and an aerosol generator using an air brush sprayer. The temperature control system was developed to prevent condensation on the chamber walls. The control performances such as the overshoot and settling time were obtained from of the developed temperature controller. Wire-heating elements were controlled at certain setting value to heat the injected aerosol to form a thin film in the substrate. The performance of as-developed AACVD system tested to form a thin film where aerosol was sprayed into the chamber with a flow rate of 7 liters/minutes, and vary in temperatures and concentrations of precursor. The temperature control system have an overshoot around 25 °C from the desired set point temperature, very small temperature ripple 2 °C and a settling time of 20 minutes. As-developed AACVD successfully fabricated a ZnO thin film with thickness of below 1 µm. The performances of system on formation of thin films influenced by the generally controlled process such as values of setting temperature and concentration where the aerosol flow rate was fixed. Higher temperature was applied, the more uniform ZnO thin films were produced. In addition, temperature of the substrate also affected on surface roughness of the obtained films, while concentration of ZnO precursor determined the thickness of produce films. It is concluded that newly simple AACVD can be applied to produce a thin film.

  2. Microstructural, chemical and textural characterization of ZnO nanorods synthesized by aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Fuentes-Cobas, L.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C. [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico); Pérez-García, S.A. [Centro de Investigación en Materiales Avanzados, S.C., Unidad Monterrey, Apodaca, Nuevo León 66600 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico)

    2014-12-15

    ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO{sub 2} covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO{sub 2} phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO{sub 2} buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°. - Highlights: • Uniform and pure single-crystal ZnO nanorods were obtained by AACVD technique. • Longitudinal and transversal axis parallel to the [001] and [110] directions, respectively. • Texture was determined by 2D synchrotron diffraction and electron microscopy analysis. • Nanorods have its [001] direction distributed close to the normal of the substrate. • Angular spread about the preferred orientation is 20° ± 2°.

  3. Aerosol assisted chemical vapour deposition of germanium thin films using organogermanium carboxylates as precursors and formation of germania films

    Indian Academy of Sciences (India)

    Alpa Y Shah; Amey Wadawale; Vijaykumar S Sagoria; Vimal K Jain; C A Betty; S Bhattacharya

    2012-06-01

    Diethyl germanium bis-picolinate, [Et2Ge(O2CC5H4N)2], and trimethyl germanium quinaldate, [Me3Ge(O2CC9H6N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO2. Both Ge and GeO2 films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current–voltage (–) characterization.

  4. Chemical aerosol Raman detector

    Science.gov (United States)

    Aggarwal, R. L.; Farrar, L. W.; Di Cecca, S.; Amin, M.; Perkins, B. G.; Clark, M. L.; Jeys, T. H.; Sickenberger, D. W.; D'Amico, F. M.; Emmons, E. D.; Christesen, S. D.; Kreis, R. J.; Kilper, G. K.

    2017-03-01

    A sensitive chemical aerosol Raman detector (CARD) has been developed for the trace detection and identification of chemical particles in the ambient atmosphere. CARD includes an improved aerosol concentrator with a concentration factor of about 40 and a CCD camera for improved detection sensitivity. Aerosolized isovanillin, which is relatively safe, has been used to characterize the performance of the CARD. The limit of detection (SNR = 10) for isovanillin in 15 s has been determined to be 1.6 pg/cm3, which corresponds to 6.3 × 109 molecules/cm3 or 0.26 ppb. While less sensitive, CARD can also detect gases. This paper provides a more detailed description of the CARD hardware and detection algorithm than has previously been published.

  5. Aerosol-assisted chemical vapor deposition of tungsten oxide films and nanorods from oxo tungsten(VI) fluoroalkoxide precursors.

    Science.gov (United States)

    Kim, Hankook; Bonsu, Richard O; O'Donohue, Christopher; Korotkov, Roman Y; McElwee-White, Lisa; Anderson, Timothy J

    2015-02-04

    Aerosol-assisted chemical vapor deposition (AACVD) of WOx was demonstrated using the oxo tungsten(VI) fluoroalkoxide single-source precursors, WO[OCCH3(CF3)2]4 and WO[OC(CH3)2CF3]4. Substoichiometric amorphous tungsten oxide thin films were grown on indium tin oxide (ITO) substrates in nitrogen at low deposition temperature (100-250 °C). At growth temperatures above 300 °C, the W18O49 monoclinic crystalline phase was observed. The surface morphology and roughness, visible light transmittance, electrical conductivity, and work function of the tungsten oxide materials are reported. The solvent and carrier gas minimally affected surface morphology and composition at low deposition temperature; however, material crystallinity varied with solvent choice at higher temperatures. The work function of the tungsten oxide thin films grown between 150 and 250 °C was determined to be in the range 5.0 to 5.7 eV, according to ultraviolet photoelectron spectroscopy (UPS).

  6. Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition

    Science.gov (United States)

    Sathasivam, Sanjayan; Bhachu, Davinder S.; Lu, Yao; Chadwick, Nicholas; Althabaiti, Shaeel A.; Alyoubi, Abdulrahman O.; Basahel, Sulaiman N.; Carmalt, Claire J.; Parkin, Ivan P.

    2015-06-01

    Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm3/V.s) and concentration (×1019 cm-3). XPS indicated the presence of both W6+ and W4+ in the TiO2 matrix, with the substitutional doping of W4+ inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2.

  7. Effect of surfactants on the morphology of FeSe films fabricated from a single source precursor by aerosol assisted chemical vapour deposition

    Indian Academy of Sciences (India)

    Raja Azadar Hussain; Amin Badshah; Naghma Haider; Malik Dilshad Khan; Bhajan Lal

    2015-03-01

    This article presents the fabrication of FeSe thin films from a single source precursor namely (1-(2-fluorobenzoyl)-3-(4-ferrocenyl-3-methylphenyl)selenourea (MeP2F)) by aerosol assisted chemical vapour deposition (AACVD). All the films were prepared via similar experimental conditions (temperature, flow rate, concentration, solvent system and reactor type) except the use of three different concentrations of two different surfactants i.e., triton and span. Seven thin films were characterized with PXRD, SEM, AFM, EDS and EDS mapping. The mechanism of the interaction of surfactant with MeP2F was determined with cyclic voltammetry (CV) and UV-Vis spectroscopy.

  8. Surface morphological and photoelectrochemical studies of ZnS thin films developed from single source precursors by aerosol assisted chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ehsan, Muhammad Ali [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Peiris, T.A. Nirmal; Wijayantha, K.G. Upul [Department of Chemistry, Loughborough University, Loughborough, LE11 3TU (United Kingdom); Khaledi, Hamid [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Ming, Huang Nay [Faculty of Science, Department of Physics, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Misran, Misni; Arifin, Zainudin [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)

    2013-07-01

    Zinc sulphide (ZnS) thin films have been deposited on fluorine-doped tin oxide-coated conducting glass substrates at 375, 425 and 475 °C temperatures from single source adduct precursors [Zn(S{sub 2}CNCy{sub 2}){sub 2}(py)] (1) [where, Cy = cyclohexyl, py = pyridine] and [Zn{S_2CN(CH_2Ph)(Me)}{sub 2}(py)] (2) [where, Ph = Phenyl, Me = Methyl] using aerosol assisted chemical vapour deposition (AACVD). The precursor complexes have been characterized by microanalysis, infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray single crystal and thermogravimetric analysis. Thermal analysis showed that both precursors (1) and (2) undergo thermal decomposition at 375 °C to produce ZnS residues. The deposited ZnS films have been characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. Scanning electron microscopic studies indicated that the surface morphology of ZnS films strongly depends on the nature of the precursor and the deposition temperature, regardless of marginal variation in thermal stability of the precursors. Direct band gap energies of 3.36 and 3.40 eV have been estimated from the ultraviolet–visible spectroscopy for the ZnS films fabricated from precursors (1) and (2), respectively. The current–voltage characteristics recorded under air mass 1.5 illumination confirmed that the deposited ZnS thin films are photoactive under anodic bias conditions. Furthermore, the photoelectrochemical (PEC) results indicate that these synthesised single source precursors are suitable for obtaining ZnS thin films by AACVD method. The ZnS thin film electrode prepared in this study are very promising for solar energy conversion and optoelectronic applications. The PEC properties of ZnS electrodes prepared from (2) are superior to that of the ZnS electrode prepared from precursor (1). - Highlights: • Synthesis and characterization of zinc dithiocarbamate pyridine adducts. • ZnS photo electrodes have been fabricated using aerosol-assisted

  9. Deposition of cobalt and nickel sulfide thin films from thio- and alkylthio-urea complexes as precursors via the aerosol assisted chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mgabi, L.P.; Dladla, B.S. [Department of Chemistry, University of Zululand, Private bag X1001 KwaDlangezwa, 3880 (South Africa); Malik, M.A. [School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Garje, Shivram S. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India); Akhtar, J. [Nanoscience and Materials Synthesis Lab, Department of Physics, COMSATS, Institute of Information Technology (CIIT), Chak shahzad, Islamabad (Pakistan); Revaprasadu, N., E-mail: RevaprasaduN@unizulu.ac.za [Department of Chemistry, University of Zululand, Private bag X1001 KwaDlangezwa, 3880 (South Africa)

    2014-08-01

    We report the synthesis of Co(II) and Ni(II) thiourea and alkylthiourea complexes by reacting the metal salts (CoCl{sub 2} and NiCl{sub 2}) with the thiourea, phenylthiourea and dicyclohexylthiourea ligands in a 1:2 ratio. The complexes, [CoCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (I), [CoCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2} (II) and [CoCI{sub 2}(SC(NHC{sub 6}H{sub 11}){sub 2}){sub 2}] (III), [NiCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (IV), [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) and [NiCl{sub 2}(SC(NHC{sub 6}H{sub 11}){sub 2}){sub 2}] (VI) were characterized by C, H, N analysis and Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that all complexes undergo a two step decomposition process except for [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) which decomposes in a single step. The complexes were used as single-source precursors for the deposition of cobalt sulfide and nickel sulfide thin films by aerosol assisted chemical vapor deposition at temperatures between 350 an 500 °C. The crystallinity of the films was determined by X-ray diffraction and their morphology was determined by scanning electron microscopy. The morphology of the cobalt sulfide thin films varies from randomly oriented platelets, to granulated spheres and cubes as the precursor and deposition conditions are changed. For nickel sulfide, the [NiCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (IV) complex gave rods whereas the [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) produced spherical particles. - Highlights: • We report the synthesis of Co(II) and Ni(II) thiourea and alkylthiourea complexes. • C, H, N analysis and Fourier transform infrared spectroscopy characterization • NiS and CoS thin films deposited by aerosol assisted chemical vapor deposition • X-ray diffraction characterization of the phase of the films • Film morphology determined by scanning electron microscopy.

  10. Modeling heterogeneous chemical processes on aerosol surface

    Institute of Scientific and Technical Information of China (English)

    Junjun Deng; Tijian Wang; Li Liu; Fei Jiang

    2010-01-01

    To explore the possible impact of heterogeneous chemical processes on atmospheric trace components,a coupled box model including gas-phase chemical processes,aerosol thermodynamic equilibrium processes,and heterogeneous chemical processes on the surface of dust,black carbon(BC)and sea salt is set up to simulate the effects of heterogeneous chemistry on the aerosol surface,and analyze the primary factors affecting the heterogeneous processes.Results indicate that heterogeneous chemical processes on the aerosol surface in the atmosphere will affect the concentrations of trace gases such as H2O2,HO2,O3,NO2,NO3,HNO3 and SO2,and aerosols such as SO42-,NO3-and NH4+.Sensitivity tests suggest that the magnitude of the impact of heterogeneous processes strongly depends on aerosol concentration and the surface uptake coefficients used in the box model.However,the impact of temperature on heterogeneous chemical processes is considerably less.The"renoxification"of HNO3 will affect the components of the troposphere such as nitrogen oxide and ozone.

  11. Study of Aerosol Chemical Composition Based on Aerosol Optical Properties

    Science.gov (United States)

    Berry, Austin; Aryal, Rudra

    2015-03-01

    We investigated the variation of aerosol absorption optical properties obtained from the CIMEL Sun-Photometer measurements over three years (2012-2014) at three AERONET sites GSFC; MD Science_Center and Tudor Hill, Bermuda. These sites were chosen based on the availability of data and locations that can receive different types of aerosols from land and ocean. These absorption properties, mainly the aerosol absorption angstrom exponent, were analyzed to examine the corresponding aerosol chemical composition. We observed that the retrieved absorption angstrom exponents over the two sites, GSFC and MD Science Center, are near 1 (the theoretical value for black carbon) and with low single scattering albedo values during summer seasons indicating presence of black carbon. Strong variability of aerosol absorption properties were observed over Tudor Hill and will be analyzed based on the air mass embedded from ocean side and land side. We will also present the seasonal variability of these properties based on long-range air mass sources at these three sites. Brent Holben, NASA GSFC, AERONET, Jon Rodriguez.

  12. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

    Science.gov (United States)

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-06-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs.

  13. Aerosol-assisted plasma deposition of hydrophobic polycations makes surfaces highly antimicrobial.

    Science.gov (United States)

    Liu, Harris; Kim, Yoojeong; Mello, Kerrianne; Lovaasen, John; Shah, Apoorva; Rice, Norman; Yim, Jacqueline H; Pappas, Daphne; Klibanov, Alexander M

    2014-02-01

    The currently used multistep chemical synthesis for making surfaces antimicrobial by attaching to them hydrophobic polycations is replaced herein by an aerosol-assisted plasma deposition procedure. To this end, N,N-hexyl,methyl-PEI (HMPEI) is directly plasma-coated onto a glass surface. The resultant immobilized HMPEI coating has been thoroughly characterized and shown to be robust, bactericidal against Escherichia coli, and virucidal against human influenza virus.

  14. Chemically Assisted Photocatalytic Oxidation System

    Science.gov (United States)

    Andino, Jean; Wu, Chang-Yu; Mazyck, David; Teixeira, Arthur A.

    2009-01-01

    The chemically assisted photocatalytic oxidation system (CAPOS) has been proposed for destroying microorganisms and organic chemicals that may be suspended in the air or present on surfaces of an air-handling system that ventilates an indoor environment. The CAPOS would comprise an upstream and a downstream stage that would implement a tandem combination of two partly redundant treatments. In the upstream stage, the air stream and, optionally, surfaces of the air-handling system would be treated with ozone, which would be generated from oxygen in the air by means of an electrical discharge or ultraviolet light. In the second stage, the air laden with ozone and oxidation products from the first stage would be made to flow in contact with a silica-titania photocatalyst exposed to ultraviolet light in the presence of water vapor. Hydroxyl radicals generated by the photocatalytic action would react with both carbon containing chemicals and microorganisms to eventually produce water and carbon dioxide, and ozone from the first stage would be photocatalytically degraded to O2. The net products of the two-stage treatment would be H2O, CO2, and O2.

  15. New trajectory-driven aerosol and chemical process model Chemical and Aerosol Lagrangian Model (CALM

    Directory of Open Access Journals (Sweden)

    P. Tunved

    2010-11-01

    Full Text Available A new Chemical and Aerosol Lagrangian Model (CALM has been developed and tested. The model incorporates all central aerosol dynamical processes, from nucleation, condensation, coagulation and deposition to cloud formation and in-cloud processing. The model is tested and evaluated against observations performed at the SMEAR II station located at Hyytiälä (61° 51' N, 24° 17' E over a time period of two years, 2000–2001. The model shows good agreement with measurements throughout most of the year, but fails in reproducing the aerosol properties during the winter season, resulting in poor agreement between model and measurements especially during December–January. Nevertheless, through the rest of the year both trends and magnitude of modal concentrations show good agreement with observation, as do the monthly average size distribution properties. The model is also shown to capture individual nucleation events to a certain degree. This indicates that nucleation largely is controlled by the availability of nucleating material (as prescribed by the [H2SO4], availability of condensing material (in this model 15% of primary reactions of monoterpenes (MT are assumed to produce low volatile species and the properties of the size distribution (more specifically, the condensation sink. This is further demonstrated by the fact that the model captures the annual trend in nuclei mode concentration. The model is also used, alongside sensitivity tests, to examine which processes dominate the aerosol size distribution physical properties. It is shown, in agreement with previous studies, that nucleation governs the number concentration during transport from clean areas. It is also shown that primary number emissions almost exclusively govern the CN concentration when air from Central Europe is advected north over Scandinavia. We also show that biogenic emissions have a large influence on the amount of potential CCN observed

  16. Physical and Chemical Characterization of Carbonaceous Aerosols in Korea

    Science.gov (United States)

    Choung, S.; Jin, J. S.; Hwang, G. S.; Jang, K. S.; Han, W. S.; OH, J.; Kwon, Y.

    2014-12-01

    Atmospheric aerosols have been recently paid attention more in environmental research due to their negative effects on air quality, public health, and climate change. The aerosols contain approximately >20-50% carbonaceous components such as organic carbon (OC) and black carbon (BC) (or elemental carbon [EC]) derived from organic compounds, biomass burning, and incomplete combustion of fossil fuels. The physical, chemical, and biological properties of atmospheric aerosols are strongly dependent on the carbonaceous components. In particular, the BC could significantly affect the regional air quality in the northeastern Asia, because China is one of the foremost BC emission country in the world. Previous studies have mainly focused on the quantification and source identification for carbonaceous aerosols. However, understanding of physical and chemical properties for the carbonaceous aerosols related to environmental contamination and toxicity was still incomplete due to analytical difficulties. This study is addressed to evaluate the contribution of carbonaceous aerosols to air pollution through the surface, mass spectroscopic, and electron microscopic analyses, and determination of chemical composition and structure using the air particulate matter (PM2.5 and >PM2.5) samples.

  17. Microwave-assisted Chemical Transformations

    Science.gov (United States)

    In recent years, there has been a considerable interest in developing sustainable chemistries utilizing green chemistry principles. Since the first published report in 1986 by Gedye and Giguere on microwave assisted synthesis in household microwave ovens, the use of microwaves as...

  18. Superhydrophobic polymer films via aerosol assisted deposition - Taking a leaf out of nature's book

    Energy Technology Data Exchange (ETDEWEB)

    Crick, Colin R. [Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ (United Kingdom); Parkin, Ivan P., E-mail: i.p.parkin@ucl.ac.u [Materials Chemistry Research Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ (United Kingdom)

    2010-05-31

    Aerosol assisted deposition of three sets of polymer films based on commercially available resins was achieved on various substrates. The films were characterised using a range of methods, including water contact and slip angle to determine water repellent properties. The aerosol assisted deposition inside the chemical vapour deposition reactor was unique in generating a highly rough superhydrophobic surface with water contact angles up to 170{sup o}. During the deposition process, two of the polymers were cured resulting in the development of high surface morphology. It was observed that the polymer that did not cure did not develop such a rough surface resulting in a lower water contact angle ({approx} 99{sup o}). The superhydrophobic films had a Cassie-Baxter type wetting with water failing to penetrate the surface porosity, water spraying on the surface would bounce off. These films had exceptionally low slide angles of ca 1-2{sup o} from the horizontal.

  19. Microbiology and atmospheric processes: chemical interactions of primary biological aerosols

    Directory of Open Access Journals (Sweden)

    L. Deguillaume

    2008-07-01

    Full Text Available This paper discusses the influence of primary biological aerosols (PBA on atmospheric chemistry and vice versa through microbiological and chemical properties and processes. Several studies have shown that PBA represent a significant fraction of air particulate matter and hence affect the microstructure and water uptake of aerosol particles. Moreover, airborne micro-organisms, namely fungal spores and bacteria, can transform chemical constituents of the atmosphere by metabolic activity. Recent studies have emphasized the viability of bacteria and metabolic degradation of organic substances in cloud water. On the other hand, the viability and metabolic activity of airborne micro-organisms depend strongly on physical and chemical atmospheric parameters such as temperature, pressure, radiation, pH value and nutrient concentrations. In spite of recent advances, however, our knowledge of the microbiological and chemical interactions of PBA in the atmosphere is rather limited. Further targeted investigations combining laboratory experiments, field measurements, and modelling studies will be required to characterize the chemical feedbacks, microbiological activities at the air/snow/water interface supplied to the atmosphere.

  20. Bioaerosol detection by aerosol TOF-mass spectrometry: Application of matrix assisted laser desorption/ionisation

    NARCIS (Netherlands)

    Wuijckhuijse, A.L. van; Stowers, M.A.; Kientz, Ch.E.; Marijnissen, J.C.M.; Scarlett, B.

    2000-01-01

    In previous publications the use of an aerosol time of flight mass spectrometer was reported for the on-line measurements of aerosols (Weiss 1997, Kievit 1995). The apparatus is capable of measuring the size as well as the chemical composition, by the use of Laser Desorption/Ionisation (LDI), of an

  1. Hygroscopic, Morphological, and Chemical Properties of Agricultural Aerosols

    Science.gov (United States)

    Hiranuma, N.; Brooks, S. D.; Cheek, L.; Thornton, D. C.; Auvermann, B. W.; Littleton, R.

    2007-12-01

    Agricultural fugitive dust is a significant source of localized air pollution in the semi-arid southern Great Plains. In the Texas Panhandle, daily episodes of ground-level fugitive dust emissions from the cattle feedlots are routinely observed in conjunction with increased cattle activity in the late afternoons and early evenings. We conducted a field study to characterize size-selected agricultural aerosols with respect to hygroscopic, morphological, and chemical properties and to attempt to identify any correlations between these properties. To explore the hygroscopic nature of agricultural particles, we have collected size-resolved aerosol samples using a cascade impactor system at a cattle feedlot in the Texas Panhandle and have used the Environmental Scanning Electron Microscope (ESEM) to determine the water uptake by individual particles in those samples as a function of relative humidity. To characterize the size distribution of agricultural aerosols as a function of time, A GRIMM aerosol spectrometer and Sequential Mobility Particle Sizer and Counter (SMPS) measurements were simultaneously performed in an overall size range of 11 nm to 20 µm diameters at a cattle feedlot. Complementary determination of the elemental composition of individual particles was performed using Energy Dispersive X-ray Spectroscopy (EDS). In addition to the EDS analysis, an ammonia scrubber was used to collect ammonia and ammonium in the gas and particulate phases, respectively. The concentration of these species was quantified offline via UV spectrophotometry at 640 nanometers. The results of this study will provide important particulate emission data from a feedyard, needed to improve our understanding of the role of agricultural particulates in local and regional air quality.

  2. Modeling regional secondary organic aerosol using the Master Chemical Mechanism

    Science.gov (United States)

    Li, Jingyi; Cleveland, Meredith; Ziemba, Luke D.; Griffin, Robert J.; Barsanti, Kelley C.; Pankow, James F.; Ying, Qi

    2015-02-01

    A modified near-explicit Master Chemical Mechanism (MCM, version 3.2) with 5727 species and 16,930 reactions and an equilibrium partitioning module was incorporated into the Community Air Quality Model (CMAQ) to predict the regional concentrations of secondary organic aerosol (SOA) from volatile organic compounds (VOCs) in the eastern United States (US). In addition to the semi-volatile SOA from equilibrium partitioning, reactive surface uptake processes were used to simulate SOA formation due to isoprene epoxydiol, glyoxal and methylglyoxal. The CMAQ-MCM-SOA model was applied to simulate SOA formation during a two-week episode from August 28 to September 7, 2006. The southeastern US has the highest SOA, with a maximum episode-averaged concentration of ∼12 μg m-3. Primary organic aerosol (POA) and SOA concentrations predicted by CMAQ-MCM-SOA agree well with AMS-derived hydrocarbon-like organic aerosol (HOA) and oxygenated organic aerosol (OOA) urban concentrations at the Moody Tower at the University of Houston. Predicted molecular properties of SOA (O/C, H/C, N/C and OM/OC ratios) at the site are similar to those reported in other urban areas, and O/C values agree with measured O/C at the same site. Isoprene epoxydiol is predicted to be the largest contributor to total SOA concentration in the southeast US, followed by methylglyoxal and glyoxal. The semi-volatile SOA components are dominated by products from β-caryophyllene oxidation, but the major species and their concentrations are sensitive to errors in saturation vapor pressure estimation. A uniform decrease of saturation vapor pressure by a factor of 100 for all condensable compounds can lead to a 150% increase in total SOA. A sensitivity simulation with UNIFAC-calculated activity coefficients (ignoring phase separation and water molecule partitioning into the organic phase) led to a 10% change in the predicted semi-volatile SOA concentrations.

  3. Application of matrix-assisted laser desorption/ionization to on-line aerosol time-of-flight mass spectrometry

    NARCIS (Netherlands)

    Stowers, M.A.; Wuijckhuijse, A.L. van; Marijnissen, J.C.M.; Scarlett, B.; Baar, B.L.M. van; Kientz, Ch.E.

    2000-01-01

    Matrix-assisted laser desorption/ionization (MALDI) mass spectra were obtained from single biological aerosol particles using an aerosol time-of- flight mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an evaporation/condensation flow cell that allowed the aerosol to be coated wi

  4. Characterization of aerosol chemical composition with aerosol mass spectrometry in Central Europe: an overview

    Directory of Open Access Journals (Sweden)

    V. A. Lanz

    2010-11-01

    Full Text Available Real-time measurements of non-refractory submicron aerosols (NR-PM1 were conducted within the greater Alpine region (Switzerland, Germany, Austria, France and Liechtenstein during several week-long field campaigns in 2002–2009. This region represents one of the most important economic and recreational spaces in Europe. A large variety of sites was covered including urban backgrounds, motorways, rural, remote, and high-alpine stations, and also mobile on-road measurements were performed. Inorganic and organic aerosol (OA fractions were determined by means of aerosol mass spectrometry (AMS. The data originating from 13 different field campaigns and the combined data have been utilized for providing an improved temporal and spatial data coverage.

    The average mass concentration of NR-PM1 for the different campaigns typically ranged between 10 and 30 μg m−3. Overall, the organic portion was most abundant, ranging from 36% to 81% of NR-PM1. Other main constituents comprised ammonium (5–15%, nitrate (8–36%, sulfate (3–26%, and chloride (0–5%. These latter anions were, on average, fully neutralized by ammonium. As a major result, time of the year (winter vs. summer and location of the site (Alpine valleys vs. Plateau could largely explain the variability in aerosol chemical composition for the different campaigns and were found to be better descriptors for aerosol composition than the type of site (urban, rural etc.. Thus, a reassessment of classifications of measurements sites might be considered in the future, possibly also for other regions of the world.

    The OA data was further analyzed using positive matrix factorization (PMF and the multi-linear engine ME (factor analysis separating the total OA into its underlying components, such as oxygenated (mostly secondary organic aerosol (OOA, hydrocarbon-like and freshly emitted organic aerosol (HOA, as well as OA from biomass

  5. Chemical markers for sea salt in IMPROVE aerosol data

    Science.gov (United States)

    White, Warren H.

    The Interagency Monitoring of PROtected Visual Environments (IMPROVE) network monitors chemically speciated fine-particle concentrations at about 170 rural or remote sites in the United States, including several in coastal settings. Sea salt is a major component of marine aerosols, and can have significant optical effects on both global and local scales. Sodium is the most commonly employed chemical marker for sea salt, but the ion is not a target of IMPROVE's routine chromatography and the element is poorly detected by IMPROVE's routine X-ray fluorescence analysis. This paper examines data from six coastal sites where sea salt is abundant, to identify more reliable signatures of fresh sea salt in routine IMPROVE data. The chloride ion measurement, by ion chromatography on a Nylon filter sampling behind a carbonate denuder, appears to represent the total concentration of this reactive species at the selected sites. It is shown to be a good predictor of conserved sea salt markers such as non-crustal strontium, calcium and potassium, as well as the portion of gravimetric mass not explained by terrestrial fractions. These conclusions may not extend to other locations where sea salt is a smaller and more aged fraction of the aerosol mix.

  6. Chemical characterization of springtime submicrometer aerosol in Po Valley, Italy

    Directory of Open Access Journals (Sweden)

    S. Saarikoski

    2012-09-01

    Full Text Available The chemistry of submicron particles was investigated at San Pietro Capofiume (SPC measurement station in the Po Valley, Italy, in spring 2008. The measurements were performed by using both off-line and on-line instruments. Organic carbon (OC and elemental carbon, organic acids and biomass burning tracers were measured off-line by using a 24-h PM1 filter sampling. More detailed particle chemistry was achieved by using a Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS and analyzing the data by positive matrix factorization (PMF. Oxalic acid had the highest concentrations of organic acids (campaign-average 97.4 ng m−3 followed by methane sulfonic, formic, malonic, and malic acids. Samples were also analyzed for glyoxylic, succinic, azelaic and maleic acids. In total, the nine acids composed 1.9 and 3.8% of OC and water-soluble OC, respectively (average, in terms of carbon atoms. Levoglucosan concentration varied from 17.7 to 495 ng m−3 with the concentration decreasing in the course of the campaign most likely due to the reduced use of domestic heating with wood. Six factors were found for organic aerosol (OA at SPC by PMF: hydrocarbon-like OA (HOA, biomass burning OA (BBOA, nitrogen-containing OA (N-OA and three different oxygenated OAs (OOA-a, OOA-b and OOA-c. Most of the OA mass was composed of OOA-a, HOA and OOA-c (26, 24 and 22%, respectively followed by OOA-b (13%, BBOA (8% and N-OA (7%. As expected, OOAs were the most oxygenated factors with organic matter:organic carbon (OM : OC ratios ranging from 1.9 to 2.2. The diurnal variability of the aerosol chemical composition was greatly affected by the boundary layer meteorology. Specifically, the effect of the nocturnal layer break-up in morning hours was most evident for nitrate and N-OA indicating that these compounds originated mainly from the local sources in the Po Valley. For sulfate and OOA-a the concentration did not

  7. Chemical characterization of springtime submicrometer aerosol in Po Valley, Italy

    Directory of Open Access Journals (Sweden)

    S. Saarikoski

    2012-03-01

    Full Text Available The chemistry of submicron particles was investigated at San Pietro Capofiume (SPC measurement station in the Po Valley, Italy, in spring 2008. The measurements were performed by using both off-line and on-line instruments. Organic carbon (OC and elemental carbon, organic acids and biomass burning tracers were measured off-line by using a 24-h PM1 filter sampling. More detailed particle chemistry was achieved by using an Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS and analyzing the data by positive matrix factorization (PMF. Oxalic acid had the highest concentrations of organic acids (campaign-average 97.4 ng m−3 followed by methane sulfonic, formic, malonic, and malic acids. Samples were also analyzed for glyoxylic, succinic, azelaic and maleic acids. In total, the nine acids composed 1.9 and 3.8% of OC and water-soluble OC, respectively (average, in terms of carbon atoms. Levoglucosan concentration varied from 17.7 to 495 ng m−3 with the concentration decreasing in the course of the campaign most likely due to the reduced use of domestic heating with wood. Six factors were found for organic aerosol (OA at SPC by PMF: hydrocarbon-like OA (HOA, biomass burning OA (BBOA, nitrogen-containing OA (N-OA and three different oxygenated OAs (OOA-a, OOA-b and OOA-c. Most of the OA mass was composed of OOA-a, HOA and OOA-c (26, 24 and 22%, respectively followed by OOA-b (13%, BBOA (8% and N-OA (7%. As expected, OOAs were the most oxygenated factors with organic matter:organic carbon (OM:OC ratios ranging from 1.9 to 2.2. The diurnal variability of the aerosol chemical composition was greatly affected by the boundary layer meteorology. Specifically, the effect of the nocturnal layer break-up in morning hours was most evident for nitrate and N-OA indicating that these compounds originated mainly from the local sources in the Po Valley. For sulfate and OOA-a the concentration did not

  8. Aerosol chemical composition at Cabauw, the Netherlands as observed in two intensive periods in May 2008 and March 2009

    NARCIS (Netherlands)

    Mensah, A.A.; Holzinger, R.; Otjes, R.; Trimborn, A.; Mentel, T.F.; Brink, H. ten; Henzing, B.; Kiendler-Scharr, A.

    2012-01-01

    Observations of aerosol chemical composition in Cabauw, the Netherlands, are presented for two intensive measurement periods in May 2008 and March 2009. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and is compared to observations from aerosol si

  9. Aerosol assisted fabrication of two dimensional ZnO island arrays and honeycomb patterns with identical lattice structures

    Directory of Open Access Journals (Sweden)

    Mitsuhiro Numata

    2010-11-01

    Full Text Available Two dimensional island arrays and honeycomb patterns consisting of ZnO nanocrystal clusters were fabricated on predefined TiO2 seed patterns prepared by vacuum free, aerosol assisted wet-chemical synthesis. The TiO2 seed patterns were prepared by applying an aerosol of a water soluble titanium complex on hexagonally close-packed polystyrene bead arrays for different lengths of time. Scanning electron microscopy revealed that a dot array grows into a honeycomb shape as increasing amounts of the precursor were deposited. ZnO nucleation on substrates with a dot array and honeycomb patterns resulted in the formation of two discrete patterns with contrasting fill fractions of the materials.

  10. Microbiology and atmospheric processes: chemical interactions of Primary Biological Aerosols

    Science.gov (United States)

    Deguillaume, L.; Leriche, M.; Amato, P.; Ariya, P. A.; Delort, A.-M.; Pöschl, U.; Chaumerliac, N.; Bauer, H.; Flossmann, A. I.; Morris, C. E.

    2008-02-01

    This paper discusses the influence of bioaerosols on atmospheric chemistry and vice versa through microbiological and chemical properties and processes. Several studies have shown that biological matter represents a significant fraction of air particulate matter and hence affects the microstructure and water uptake of aerosol particles. Moreover, airborne micro-organisms can transform chemical constituents of the atmosphere by metabolic activity. Recent studies have emphasized the viability of bacteria and metabolic degradation of organic substances in cloud water. On the other hand, the viability and metabolic activity of airborne micro-organisms depend strongly on physical and chemical atmospheric parameters such as temperature, pressure, radiation, pH value and nutrient concentrations. In spite of recent advances, however, our knowledge of the microbiological and chemical interactions of primary biological particles in the atmosphere is rather limited. Further targeted investigations combining laboratory experiments, field measurements, and modelling studies will be required to characterize the chemical feedbacks, microbiological activities at the air/snow/water interface supplied to the atmosphere.

  11. Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean-potential impacts

    NARCIS (Netherlands)

    Astitha, M.; Kallos, G.; Spyrou, C.; O'Hirok, W.; Lelieveld, J.; Denier Gon, H.A.C. van der

    2010-01-01

    Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size dis

  12. Chemically aged and mixed aerosols over the Central Atlantic Ocean - Potential impacts

    NARCIS (Netherlands)

    Astitha, M.; Kallos, G.; Spyrou, C.; O'Hirok, W.; Lelieveld, J.; Denier Gon, H.A.C. van der

    2010-01-01

    Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size dis

  13. Simulation of aerosol chemical compositions in the Western Mediterranean Sea

    Science.gov (United States)

    Chrit, Mounir; Kata Sartelet, Karine; Sciare, Jean; Marchand, Nicolas; Pey, Jorge; Sellegri, Karine

    2016-04-01

    This work aims at evaluating the chemical transport model (CTM) Polair3d of the air-quality modelling platform Polyphemus during the ChArMex summer campaigns of 2013, using ground-based measurements performed at ERSA (Cape Corsica, France), and at determining the processes controlling organic aerosol concentrations at ERSA. Simulations are compared to measurements for concentrations of both organic and inorganic species, as well as the ratio of biogenic versus anthropogenic particles, and organic aerosol properties (oxidation state). For inorganics, the concentrations of sulphate, sodium, chloride, ammonium and nitrate are compared to measurements. Non-sea-salt sulphate and ammonium concentrations are well reproduced by the model. However, because of the geographic location of the measurement station at Cape Corsica which undergoes strong wind velocities and sea effects, sea-salt sulphate, sodium, chloride and nitrate concentrations are strongly influenced by the parameterizations used for sea-salt emissions. Different parameterizations are compared and a parameterization is chosen after comparison to sodium measurements. For organics, the concentrations are well modelled when compared to experimental values. Anthropogenic particles are influenced by emission of semi-volatile organic compounds (SVOC). Measurements allow us to refine the estimation of those emissions, which are currently missing in emission inventories. Although concentrations of biogenic particles are well simulated, the organic chemical compounds are not enough oxidised in the model. The observed oxidation state of organics shows that the oligomerisation of pinonaldehyde was over-estimated in Polyphemus. To improve the oxidation property of organics, the formation of extremely low volatile organic compounds from autoxidation of monoterpenes is added to Polyphemus, using recently published data from chamber experiments. These chemical compounds are highly oxygenated and are formed rapidly, as first

  14. Hygroscopic and chemical characterisation of Po Valley aerosol

    Science.gov (United States)

    Bialek, J.; Dall Osto, M.; Vaattovaara, P.; Decesari, S.; Ovadnevaite, J.; Laaksonen, A.; O'Dowd, C.

    2014-02-01

    Continental summer-time aerosol in the Italian Po Valley was characterised in terms of hygroscopic properties and the influence of chemical composition therein. Additionally, the ethanol affinity of particles was analysed. The campaign-average minima in hygroscopic growth factors (HGFs, at 90% relative humidity) occurred just before and during sunrise from 03:00 to 06:00 LT (all data are reported in the local time), but, more generally, the hygroscopicity during the whole night is very low, particularly in the smaller particle sizes. The average HGFs recorded during the low HGF period were in a range from 1.18 (for the smallest, 35nm particles) to 1.38 (for the largest, 165 nm particles). During the day, the HGF gradually increased to achieve maximum values in the early afternoon hours 12:00-15:00, reaching 1.32 for 35 nm particles and 1.46 for 165 nm particles. Two contrasting case scenarios were encountered during the measurement period: Case 1 was associated with westerly air flow moving at a moderate pace and Case 2 was associated with more stagnant, slower moving air from the north-easterly sector. Case 1 exhibited weak diurnal temporal patterns, with no distinct maximum or minimum in HGF or chemical composition, and was associated with moderate non-refractory aerosol mass concentrations (for 50% size cut at 1 μ) of the order of 4.5 μg m-3. For Case 1, organics contributed typically 50% of the mass. Case 2 was characterised by >9.5 μg m-3 total non-refractory mass (organic mass concentrations. Specifically, the concentrations of nitrate peaked at night-time, along with the concentrations of hydrocarbon-like organic aerosol (HOA) and of semi-volatile oxygenated organic aerosol (SV-OOA). In general, organic growth factors (OGFs) followed a trend which was opposed to HGF and also to the total organic mass as measured by the aerosol mass spectrometer. The analysis of the HGF probability distribution function (PDF) reveals an existence of a predominant "more

  15. Secondary organic aerosols. Chemical aging, hygroscopicity, and cloud droplet activation

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, Angela

    2011-07-06

    Atmospheric aerosols have an important impact on the radiation balance, and thus, on the climate of the Earth. Aerosol particles scatter and absorb incoming solar and terrestrial radiation. Apart from this direct effect, aerosol particles act as cloud condensation nuclei (CCN), thereby greatly influencing the microphysics of clouds. Secondary organic aerosols (SOA) are an important fraction of the total aerosol mass. In many environments these organic compounds are mainly products of the oxidation of biogenic volatile organic compounds (VOC). In this study the hygroscopic growth and CCN activation of biogenic SOA were investigated which was formed by the oxidation of VOC with O{sub 3} and photochemically formed OH radicals under low NO{sub x} conditions. For this purpose, a complex mixture of VOC emitted by boreal tree species as gas-phase precursors was used in the Juelich Plant Atmosphere Chamber (JPAC). In long-term studies in the atmosphere simulation chamber SAPHIR {alpha}-pinene or a defined mixture of {alpha}-pinene, {beta}-pinene, limonene, ocimene, {delta}-3-carene served as precursors. Initial precursor concentrations between 40 and 1000 ppbC were investigated. The observed SOA particles were slightly hygroscopic with an average hygroscopicity parameter {kappa}(CCN) = 0.10 {+-} 0.02 and {kappa}(90%RH) = 0.05 {+-} 0.01. Closure between hygroscopic growth and CCN activation data could be achieved allowing either surface tension reduction, limited solubility, or non-ideality of the solution in the droplet. The SOA solutions in equilibrium with RH <95% are possible highly non-ideal. Therefore the organic-water interaction were investigated by applying the UNIFAC model. Calculations for surrogate compounds exhibited the same strong concentration (i.e. RH) dependence of {kappa} at sub-saturation. The growth curves could be fitted and CCN activation predicted by assuming a binary mixture of water and one hypothetical organic compound. The occurrence of

  16. Chemical and Spatial Microscopy of Individual Organic Aerosols

    Science.gov (United States)

    Tivanski, Alexei V.; Hopkins, Rebecca J.; Gilles, Mary K.

    2008-03-01

    Carbonaceous particles originating from biomass burning can account for a large fraction of organic aerosols in a local environment. Presently, their composition, physical, and chemical properties as well as their environmental effects are largely unknown. A distinct type of biomass burn particles, called ``tar balls'', have been observed in a number of field campaigns, both in fresh and aged smoke. They are characterized by their spherical morphology, high carbon content and ability to efficiently scatter and absorb light. Here, a combination of scanning transmission x-ray microscopy and near edge x-ray absorption fine structure spectroscopy is used to determine the shape, structure and size-dependent chemical composition of 150 individual tar ball particles ranging in size from 0.15 to 1.2 μm. Oxygen is present primarily as carboxylic carbonyls and oxygen-substituted alkyl functional groups. The observed chemical composition is distinctly different from black carbon and more closely resembles high molecular weight humic-like substances. A detailed examination of the carbonyl intensity as a function of particle size reveals the presence of a thin oxygenated interface layer on the tar balls, indicative of atmospheric processing of biomass burn particles.

  17. Aerosol assisted depositions of polymers using an atomiser delivery system.

    Science.gov (United States)

    Crick, Colin R; Clausen-Thue, Victoria; Parkin, Ivan P

    2011-09-01

    The hydrophobicity, robustness and anti-microbial properties of Sylgard 184 polymer films deposited via AACVD were optimised by using aerosol droplets from an atomiser delivery system, polymer coating substrates and the swell encapsulation of methylene blue. By using an atomiser deposition system (average droplet size 0.35 microm) rather than a misting aerosol system (45 microm) lead to a surface with smaller surface features, which improved hydrophobicity (water contact angle 165 degrees) in addition to increasing the films transparency from ca 10 to 65%. Pre-treating the substrates with the same Sylgard 184 elastomer lead to a highly consistent surface hydrophobicity and an increase in average water contact angle measured (169 degrees). This paper shows the first example of dye incorporation in a CVD derived polymer film-these films have potential as antimicrobial surfaces.

  18. Aerosol-Assisted Self-Assembly of Mesostructured Spherical Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Brinker, C.J.; Fan,; H.; Lu, Y.; Rieker, T.; Stump, A.; Ward, T.L.

    1999-03-23

    Nanostructured particles exhibiting well-defined pore sizes and pore connectivities (1-, 2-, or 3-dimensional) are of interest for catalysis, chromatography, controlled release, low dielectric constant fillers, and custom-designed pigments and optical hosts. During the last several years considerable progress has been made on controlling the macroscopic forms of mesoporous silicas prepared by surfactant and block copolymer liquid crystalline templating procedures. Typically interfacial phenomena are used to control the macroscopic form (particles, fibers, or films), while self-assembly of amphiphilic surfactants or polymers is used to control the mesostructure. To date, although a variety of spherical or nearly-spherical particles have been prepared, their extent of order is limited as is the range of attainable mesostructures. They report a rapid, aerosol process that results in solid, completely ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures. The process relies on evaporation-induced interfacial self-assembly (EISA) confined to a spherical aerosol droplet. The process is simple and generalizable to a variety of materials combinations. Additionally, it can be modified to provide the first aerosol route to the formation of ordered mesostructured films.

  19. Atmospheric aerosol compositions in China: spatial/temporal variability, chemical signature, regional haze distribution and comparisons with global aerosols

    Directory of Open Access Journals (Sweden)

    X. Y. Zhang

    2012-01-01

    Full Text Available From 2006 to 2007, the daily concentrations of major inorganic water-soluble constituents, mineral aerosol, organic carbon (OC and elemental carbon (EC in ambient PM10 samples were investigated from 16 urban, rural and remote sites in various regions of China, and were compared with global aerosol measurements. A large difference between urban and rural chemical species was found, normally with 1.5 to 2.5 factors higher in urban than in rural sites. Optically-scattering aerosols, such as sulfate (~16%, OC (~15%, nitrate (~7%, ammonium (~5% and mineral aerosol (~35% in most circumstance, are majorities of the total aerosols, indicating a dominant scattering feature of aerosols in China. Of the total OC, ~55%–60% can be attributed to the formation of the secondary organic carbon (SOC. The absorbing aerosol EC only accounts for ~3.5% of the total PM10. Seasonally, maximum concentrations of most aerosol species were found in winter while mineral aerosol peaks in spring. In addition to the regular seasonal maximum, secondary peaks were found for sulfate and ammonium in summer and for OC and EC in May and June. This can be considered as a typical seasonal pattern in various aerosol components in China. Aerosol acidity was normally neutral in most of urban areas, but becomes some acidic in rural areas. Based on the surface visibility observations from 681 meteorological stations in China between 1957 and 2005, four major haze areas are identified with similar visibility changes, namely, (1 Hua Bei Plain in N. China, and the Guanzhong Plain; (2 E. China with the main body in the Yangtze River Delta area; (3 S. China with most areas of Guangdong and the Pearl River Delta area; (4 The Si Chuan Basin in S.W. China. The degradation of visibility in these areas is linked with the emission changes and high PM concentrations. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric

  20. Chemical characterization and physico-chemical properties of aerosols at Villum Research Station, Greenland during spring 2015

    Science.gov (United States)

    Glasius, M.; Iversen, L. S.; Svendsen, S. B.; Hansen, A. M. K.; Nielsen, I. E.; Nøjgaard, J. K.; Zhang, H.; Goldstein, A. H.; Skov, H.; Massling, A.; Bilde, M.

    2015-12-01

    The effects of aerosols on the radiation balance and climate are of special concern in Arctic areas, which have experienced warming at twice the rate of the global average. As future scenarios include increased emissions of air pollution, including sulfate aerosols, from ship traffic and oil exploration in the Arctic, there is an urgent need to obtain the fundamental scientific knowledge to accurately assess the consequences of pollutants to environment and climate. In this work, we studied the chemistry of aerosols at the new Villum Research Station (81°36' N, 16°40' W) in north-east Greenland during the "inauguration campaign" in spring 2015. The chemical composition of sub-micrometer Arctic aerosols was investigated using a Soot Particle Time-of-Flight Aerosol Mass Spectrometer (SP-ToF-AMS). Aerosol samples were also collected on filters using both a high-volume sampler and a low-volume sampler equipped with a denuder for organic gases. Chemical analyses of filter samples include determination of inorganic anions and cations using ion-chromatography, and analysis of carboxylic acids and organosulfates of anthropogenic and biogenic origin using ultrahigh-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Previous studies found that organosulfates constitute a surprisingly high fraction of organic aerosols during the Arctic Haze period in winter and spring. Investigation of organic molecular tracers provides useful information on aerosol sources and atmospheric processes. The physico-chemical properties of Arctic aerosols are also under investigation. These measurements include particle number size distribution, water activity and surface tension of aerosol samples in order to deduct information on their hygroscopicity and cloud-forming potential. The results of this study are relevant to understanding aerosol sources and processes as well as climate effects in the Arctic, especially during the Arctic haze

  1. The online chemical analysis of single particles using aerosol beams and time of flight mass spectroscopy

    NARCIS (Netherlands)

    Kievit, O.; Weiss, M.; Verheijen, P.J.T.; Marijnissen, J.C.M.; Scarlett, B.

    This paper describes an on-line instrument, capable of measuring the size and chemical composition of single aerosol particles. Possible applications include monitoring aerosol reactors and studying atmospheric chemistry. The main conclusion is that a working prototype has been built and tested. It

  2. Estimation of aerosol water and chemical composition from AERONET at Cabauw, the Netherlands

    Directory of Open Access Journals (Sweden)

    A. J. van Beelen

    2013-06-01

    Full Text Available Remote sensing of aerosols provides important information on the atmospheric aerosol abundance. However, due to the hygroscopic nature of aerosol particles observed aerosol optical properties are influenced by atmospheric humidity, and the measurements do not unambiguously characterize the aerosol dry mass and composition which complicates the comparison with aerosol models. In this study we derive aerosol water and chemical composition by a modeling approach that combines individual measurements of remotely sensed aerosol properties (e.g. optical thickness, single scattering albedo, refractive index and size distribution from an AERONET (Aerosol Robotic Network sun-photometer with radiosonde measurements of relative humidity. The model simulates water uptake by aerosols based on the chemical composition and size distribution. A minimization method is used to calculate aerosol composition and concentration, which are then compared to in situ measurements from the Intensive Measurement Campaign At the Cabauw Tower (IMPACT, May 2008, the Netherlands. Computed concentrations show reasonable agreement with surface observations and follow the day-to-day variability in observations. Total dry mass (33 ± 12 μg m−3 and black carbon concentrations (0.7 ± 0.3 μg m−3 are generally accurately computed. The uncertainty in the AERONET (real refractive index (0.025–0.05 introduces larger uncertainty in the modeled aerosol composition (e.g. sulfates, ammonium nitrate or organic matter and leads to an uncertainty of 0.1–0.25 in aerosol water volume fraction. Water volume fraction is highly variable depending on composition, up to >0.5 at 70–80% and <0.1 at 40% relative humidity.

  3. Chemical composition of aerosols in winter/spring in Beijing

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In 1999 aerosol samples were collected by cascade at Meteorological Tower in Beijing. The 12 group aerosol samples obtained were analyzed using PIXE method, which resulted in 20 elemental concentrations and size distribution of elemental concentrations. From the observation, the elemental concentrations,size distribution of elemental concentrations and their variations are analyzed. It shows that concentrations of the most elements in aerosols increase greatly compared with those in the past except that the concentrations of V, K, Sr, and the source of aerosols has changed greatly in the past decade. Fine mode aerosols increase more rapidly in the past decade, which may be due to the contribution of coal combustion and automobile exhaust. Pb content in aerosol is much higher than that at the beginning of 1980s, and has a decreasing trend in recent years because of using non-leaded gasoline.

  4. Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean – potential impacts

    Directory of Open Access Journals (Sweden)

    M. Astitha

    2010-07-01

    Full Text Available Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates, natural (desert dust, sea salt and chemically aged (sulphate and nitrate on dust aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, indicating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols shows that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud, and by entrainment. The sodium (sea salt related aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region.

  5. Chemically aged and mixed aerosols over the Central Atlantic Ocean – potential impacts

    Directory of Open Access Journals (Sweden)

    H. A. C. Denier van der Gon

    2010-02-01

    Full Text Available Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates, natural (desert dust, sea salt and chemically aged (sulphate and nitrate on dust aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, designating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols indicates that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud and entrainment. The sodium (sea salt related aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region.

  6. Chemically aged and mixed aerosols over the Central Atlantic Ocean - potential impacts

    Science.gov (United States)

    Astitha, M.; Kallos, G.; Spyrou, C.; O'Hirok, W.; Lelieveld, J.; Denier van der Gon, H. A. C.

    2010-02-01

    Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates), natural (desert dust, sea salt) and chemically aged (sulphate and nitrate on dust) aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode) are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, designating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols indicates that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud and entrainment). The sodium (sea salt related) aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region.

  7. Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean - potential impacts

    Science.gov (United States)

    Astitha, M.; Kallos, G.; Spyrou, C.; O'Hirok, W.; Lelieveld, J.; Denier van der Gon, H. A. C.

    2010-07-01

    Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates), natural (desert dust, sea salt) and chemically aged (sulphate and nitrate on dust) aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode) are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, indicating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols shows that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud, and by entrainment). The sodium (sea salt related) aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region.

  8. Chemical and Physical Properties of the Remote Marine Aerosol by Gravimetric and Electron Microscopic Methods.

    Science.gov (United States)

    McInnes, Lynn Mari

    The chemical and physical properties of the individual submicrometer particles in the remote marine boundary layer (MBL) atmosphere are important parameters used to study atmospheric processes. Particles in this size range influence the total number concentration of particles, the number concentration of cloud condensation nuclei, and the total light scattering. As the aerosol evolves by physical and chemical mechanisms, the aerosol properties will also change. It is therefore important to measure the changing aerosol properties as a function of individual particle size within the meteorologically important time periods. Individual particle analysis using electron microscopy (EM) techniques coupled with X ray analysis can provide chemical, morphological, and particle size information on samples collected for only a few minutes. It is also possible to determine the ambient particle size distribution and relative abundances from the EM analysis using correction techniques. Measurements obtained from aerosol particles collected from the remote (MBL) during the Pacific Sulfur Stratus Investigation (PSI-3) and Cloud and Aerosol Chemistry Experiment (CACHE-1) at Cheeka Peak in the spring of 1991 and 1993 are presented along with results obtained from aerosol particles collected during the Marine Aerosol and Gas Exchange (MAGE) Experiment in the Equatorial Pacific and Radiatively Important Trace Species (RITS) Experiment in the spring of 1992 and 1993. Measurements of relative abundance of sea-salt, sulfate, and carbon-containing particles are presented as well as their chemistry. In particular the chemical reactions involving sea-salt particles are discussed in relation to the measurements of chloride depletion and sulfur enriched reported for individual particles. To supplement the few available measurements of the total submicrometer aerosol mass, samples were also collected for gravimetric analysis. Comparisons of the gravimetric mass to the total aerosol mass

  9. Activation of "synthetic ambient" aerosols - Relation to chemical composition of particles <100 nm

    Science.gov (United States)

    Burkart, J.; Hitzenberger, R.; Reischl, G.; Bauer, H.; Leder, K.; Puxbaum, H.

    2012-07-01

    Cloud condensation nuclei (CCN) are an important fraction of atmospheric aerosols because of their role in cloud formation. Experimental studies focus either on direct field measurements of complex ambient aerosols or laboratory investigations on well defined aerosols produced from single substances or substance mixtures. In this study, we focussed on the ultrafine aerosol because in terms of number concentration, the majority of the CCN are expected to have sizes in this range. A field study was performed from July 2007 to October 2008 to investigate the activation behaviour of the atmospheric aerosol in Vienna (Burkart et al., 2011). Filter samples of the aerosol aerosol in a nebulizer. Chemical analyses of the ultrafine water soluble material were also performed. The CCN properties of the "synthetic ambient" aerosol were obtained using the University of Vienna CCN counter (Giebl et al., 2002; Dusek et al., 2006b) at a nominal supersaturation (SS) of 0.5%. Activation diameters dact ranged from 54.5 nm to 66 nm, were larger than dact of typical single inorganic salts and showed no seasonal pattern in contrast to the fraction of water soluble organic carbon (WSOC), which ranged from 44% in spring to 15% in winter. The average hygroscopicity parameter κ (Petters and Kreidenweis, 2007) obtained from the activation curves ranged from 0.20 to 0.30 (average 0.24), which was significantly lower than κchem calculated from the chemical composition (0.43 ± 0.07).

  10. REPRESENTING AEROSOL DYNAMICS AND PROPERTIES IN CHEMICAL TRANSPORT MODELS BY THE METHOD OF MOMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    SCHWARTZ, S.E.; MCGRAW, R.; BENKOVITZ, C.M.; WRIGHT, D.L.

    2001-04-01

    Atmospheric aerosols, suspensions of solid or liquid particles, are an important multi-phase system. Aerosols scatter and absorb shortwave (solar) radiation, affecting climate (Charlson et al., 1992; Schwartz, 1996) and visibility; nucleate cloud droplet formation, modifying the reflectivity of clouds (Twomey et al., 1984; Schwartz and Slingo, 1996) as well as contributing to composition of cloudwater and to wet deposition (Seinfeld and Pandis, 1998); and affect human health through inhalation (NRC, 1998). Existing and prospective air quality regulations impose standards on concentrations of atmospheric aerosols to protect human health and welfare (EPA, 1998). Chemical transport and transformation models representing the loading and geographical distribution of aerosols and precursor gases are needed to permit development of effective and efficient strategies for meeting air quality standards, and for examining aerosol effects on climate retrospectively and prospectively for different emissions scenarios. Important aerosol properties and processes depend on their size distribution: light scattering, cloud nucleating properties, dry deposition, and penetration into airways of lungs. The evolution of the mass loading itself depends on particle size because of the size dependence of growth and removal processes. For these reasons it is increasingly recognized that chemical transport and transformation models must represent not just the mass loading of atmospheric particulate matter but also the aerosol microphysical properties and the evolution of these properties if aerosols are to be accurately represented in these models. If the size distribution of the aerosol is known, a given property can be evaluated as the integral of the appropriate kernel function over the size distribution. This has motivated the approach of determining aerosol size distribution, and of explicitly representing this distribution and its evolution in chemical transport models.

  11. Chemical composition of atmospheric aerosols between Moscow and Vladivostok

    Directory of Open Access Journals (Sweden)

    S. Kuokka

    2007-05-01

    Full Text Available The TROICA-9 expedition (Trans-Siberian Observations Into the Chemistry of the Atmosphere was carried out at the Trans-Siberian railway between Moscow and Vladivostok in October 2005. Measurements of aerosol physical and chemical properties were made from an observatory carriage connected to a passenger train. Black carbon (BC concentrations in fine particles (PM2.5, aerodynamic diameter <2.5 μm were measured with an aethalometer using a five-minute time resolution. Concentrations of inorganic ions and some organic compounds (Cl, NO3, SO42−, Na+, NH4+, K+, Ca2+, Mg2+, oxalate and methane sulphonate were measured continuously by using an on-line system with a 15-min time resolution. In addition, particle volume size distributions were determined for particles in the diameter range 3–850 nm using a 10-min. time resolution. The continuous measurements were completed with 24-h. PM2.5 filter samples which were stored in a refrigerator and later analyzed in chemical laboratory. The analyses included mass concentrations of PM2.5, ions, monosaccharide anhydrides (levoglucosan, galactosan and mannosan and trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, V and Zn. The mass concentrations of PM2.5 varied in the range of 4.3–34.8 μg m−3 with an average of 21.6 μg m−3. Fine particle mass consisted mainly of BC (average 27.6%, SO42− (13.0%, NH4+ (4.1%, and NO3 (1.4%. One of the major constituents was obviously also organic carbon which was not determined. The contribution of BC was high compared with other studies made in Europe and Asia. High concentrations of ions, BC and particle volume were observed between Moscow and roughly 4000 km east of it, as well as close to

  12. Physico-chemical properties of aerosols in Sao Paulo, Brazil and mechanisms of secondary organic aerosol formation.

    Science.gov (United States)

    Artaxo, Paulo; Ferreira de Brito, Joel; Varanda Rizzo, Luciana; Luiza Godoy, Maria; Godoy, Jose Marcus

    2013-04-01

    Megacities emissions are increasingly becoming a global issue, where emissions from the transportation sector play an increasingly important role. Sao Paulo is a megacity with a population of about 18 million people, 7 million cars and large-scale industrial emissions. As a result of the vehicular and industrial emissions, the air quality in Sao Paulo is bellow WMO standards for aerosol particles and ozone. Many uncertainties are found on gas- and particulate matter vehicular emission factors and their following atmospheric processes, e.g. secondary organic aerosol formation. Due to the uniqueness of the vehicular fuel in Brazil, largely based on ethanol use, such characterization currently holds further uncertainties. To improve the understanding of the role of this unique emission characteristics, we are running a source apportionment study in Sao Paulo focused on the mechanisms of organic aerosol formation. One of the goals of this study is a quantitative aerosol source apportionment focused on vehicular emissions, including ethanol and gasohol (both fuels used by light-duty vehicles). This study comprises four sampling sites with continuous measurements for one year, where trace elements and organic aerosol are being measured for PM2.5 and PM10 along with real-time NOx, O3, PM10 and CO measurements. Aerosol optical properties and size distribution are being measured on a rotation basis between sampling stations. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to measure in real time VOCs and aerosol composition, respectively. Trace elements were measured using XRF and OC/EC analysis was determined with a Sunset OC/EC instrument. A TSI Nephelometer with 3 wavelengths measure light scattering and a MAAP measure black carbon. Results show aerosol number concentrations ranging between 10,000 and 35,000 cm-3, mostly concentrated in the nucleation and Aitken modes, with a peak in size at 80

  13. Theoretical and experimental analysis of the aerosol assisted CVD synthesis of magnetite hollow nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Monárrez-Cordero, B.E.; Amézaga-Madrid, P., E-mail: patricia.amezaga@cimav.edu.mx; Hernández-Salcedo, P.G.; Antúnez-Flores, W.; Leyva-Porras, C.; Miki-Yoshida, M.

    2014-12-05

    Highlights: • High purity mesoporous hollow magnetite nanoparticles were synthesized by AACVD. • Microstructural characteristics strongly depends on the synthesis conditions. • Activation energy of −159 kJ mol{sup −1} was obtained from thermogravimetric analyses of FeCl{sub 2.} • Simulation of concentration distribution of reactants and products was realized. • Simulated and experimental magnetite production rate agreed around 2 × 10{sup −5} mol h{sup −1}. - Abstract: Nowadays, mesoporous magnetite nanoparticles are an important class of new nanomaterials which occupy a valuable position in materials science. Owing to their several advantages over bulk magnetite and particularly with respect to higher adsorption capacity, there is a growing interest towards the use of these materials for the adsorptive removal of a variety of contaminants, including organic dyes from wastewater. Through aerosol assisted chemical vapor deposition (AACVD) technique is possible to synthesize spherical hollow nanoparticles with external diameter from 50 to 500 nm, composed of a shell of crystallites smaller than 30 nm. In the AACVD method, the structural morphology of resultant nanoparticles strongly depends on the starting precursors and operating conditions. Some advantages of this technique are the high production rate, continuous operation, use of relatively simple equipment, easy doping and the possibility to scale the process industrially. Therefore, in order to understand the formation of magnetite nanoparticles by AACVD, theoretical simulations were performed on two important steps of the synthesis: (i) temperature and carrier gas flow distribution inside of tubular reactor, and (ii) the distribution of molar concentration of the precursor in the synthesis process. Reaction kinetics of the precursor was studied to determine Arrhenius parameters. Activation energy and pre-exponential factor were calculated experimentally from thermal analysis, these values

  14. Aerosol Optical Properties Measured Onboard the Ronald H. Brown During ACE Asia as a Function of Aerosol Chemical Composition and Source Region

    Science.gov (United States)

    Quinn, P. K.; Coffman, D. J.; Bates, T. S.; Welton, E. J.; Covert, D. S.; Miller, T. L.; Johnson, J. E.; Maria, S.; Russell, L.; Arimoto, R.

    2004-01-01

    During the ACE Asia intensive field campaign conducted in the spring of 2001 aerosol properties were measured onboard the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180 deg backscatter were measured. Aerosol within the ACE Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Angstrom exponents, optical depth, and vertical profiles of aerosol extinction. All results except aerosol optical depth and the vertical profiles of aerosol extinction are reported at a relative humidity of 55 +/- 5%. An over-determined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By taking into account non-sphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE Asia aerosol. Mass scattering efficiencies of non-sea salt sulfate aerosol, sea salt, submicron particulate organic

  15. Airborne studies of aerosol emissions from savanna fires in southern Africa: 2. Aerosol chemical composition

    Science.gov (United States)

    Andreae, M. O.; Andreae, T. W.; Annegarn, H.; Beer, J.; Cachier, H.; Le Canut, P.; Elbert, W.; Maenhaut, W.; Salma, I.; Wienhold, F. G.; Zenker, T.

    1998-12-01

    We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than ˜1-2 μm and a Teflon second filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser-optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO2 and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10-30% of the aerosol mass. K+ and NH4+ were the dominant cationic species in the smoke of most fires, while Cl- and SO42- were the most important anions. The aerosols were unusually rich in Cl-, probably due to the high Cl content of the semiarid vegetation. Comparison of the element budget of the fuel before and after the fires shows that the fraction of the elements released during combustion is highly variable between elements. In the case of the halogen elements, almost the entire amount released during the fire is present in the aerosol phase, while in the case of C, N, and S, only a small proportion ends up as particulate matter. This suggests that the latter elements are present predominantly as gaseous species in the fresh fire plumes studied here.

  16. CCN frequency distributions and aerosol chemical composition from long-term observations at European ACTRIS supersites

    Science.gov (United States)

    Decesari, Stefano; Rinaldi, Matteo; Schmale, Julia Yvonne; Gysel, Martin; Fröhlich, Roman; Poulain, Laurent; Henning, Silvia; Stratmann, Frank; Facchini, Maria Cristina

    2016-04-01

    Cloud droplet number concentration is regulated by the availability of aerosol acting as cloud condensation nuclei (CCN). Predicting the air concentrations of CCN involves knowledge of all physical and chemical processes that contribute to shape the particle size distribution and determine aerosol hygroscopicity. The relevance of specific atmospheric processes (e.g., nucleation, coagulation, condensation of secondary organic and inorganic aerosol, etc.) is time- and site-dependent, therefore the availability of long-term, time-resolved aerosol observations at locations representative of diverse environments is strategic for the validation of state-of-the-art chemical transport models suited to predict CCN concentrations. We focused on long-term (year-long) datasets of CCN and of aerosol composition data including black carbon, and inorganic as well as organic compounds from the Aerosol Chemical Speciation Monitor (ACSM) at selected ACTRIS supersites (http://www.actris.eu/). We discuss here the joint frequency distribution of CCN levels and of aerosol chemical components concentrations for two stations: an alpine site (Jungfraujoch, CH) and a central European rural site (Melpitz, DE). The CCN frequency distributions at Jungfraujoch are broad and generally correlated with the distributions of the concentrations of aerosol chemical components (e.g., high CCN concentrations are most frequently found for high organic matter or black carbon concentrations, and vice versa), which can be explained as an effect of the strong seasonality in the aerosol characteristics at the mountain site. The CCN frequency distributions in Melpitz show a much weaker overlap with the distributions of BC concentrations or other chemical compounds. However, especially at high CCN concentration levels, a statistical correlation with organic matter (OM) concentration can be observed. For instance, the number of CCN (with particle diameter between 20 and 250 nm) at a supersaturation of 0.7% is

  17. Quantum Chemical Calculations Resolved Identification of Methylnitrocatechols in Atmospheric Aerosols.

    Science.gov (United States)

    Frka, Sanja; Šala, Martin; Kroflič, Ana; Huš, Matej; Čusak, Alen; Grgić, Irena

    2016-06-01

    Methylnitrocatechols (MNCs) are secondary organic aerosol (SOA) tracers and major contributors to atmospheric brown carbon; however, their formation and aging processes in atmospheric waters are unknown. To investigate the importance of aqueous-phase electrophilic substitution of 3-methylcatechol with nitronium ion (NO2(+)), we performed quantum calculations of their favorable pathways. The calculations predicted the formation of 3-methyl-5-nitrocatechol (3M5NC), 3-methyl-4-nitrocatechol (3M4NC), and a negligible amount of 3-methyl-6-nitrocatechol (3M6NC). MNCs in atmospheric PM2 samples were further inspected by LC/(-)ESI-MS/MS using commercial as well as de novo synthesized authentic standards. We detected 3M5NC and, for the first time, 3M4NC. In contrast to previous reports, 3M6NC was not observed. Agreement between calculated and observed 3M5NC/3M4NC ratios cannot unambiguously confirm the electrophilic mechanism as the exclusive formation pathway of MNCs in aerosol water. However, the examined nitration by NO2(+) is supported by (1) the absence of 3M6NC in the ambient aerosols analyzed and (2) the constant 3M5NC/3M4NC ratio in field aerosol samples, which indicates their common formation pathway. The magnitude of error one could make by incorrectly identifying 3M4NC as 3M6NC in ambient aerosols was also assessed, suggesting the importance of evaluating the literature regarding MNCs with special care.

  18. Spatial variation of chemical composition and sources of submicron aerosol in Zurich: factor analysis of mobile aerosol mass spectrometer data

    Directory of Open Access Journals (Sweden)

    C. Mohr

    2011-04-01

    Full Text Available Mobile measurements of PM1 (PM with an aerodynamic diameter D<1 μm chemical composition using a quadrupole aerosol mass spectrometer and a multi-angle absorption photometer were performed using the PSI mobile laboratory during winter 2007/2008 and December 2008 in the metropolitan area of Zurich, Switzerland. Positive matrix factorization (PMF applied to the organic fraction of PM1 yielded 3 factors: Hydrocarbon-like organic aerosol (HOA related to traffic emissions; organic aerosol from wood burning for domestic heating purposes (WBOA; and oxygenated organic aerosol (OOA, assigned to secondary organic aerosol formed by oxidation of volatile precursors. The spatial variation of the chemical composition of PM1 shows a uniform distribution throughout the city: for primary emissions, road traffic is important along major roads (varying between 7 and 14% of PM1 for different sites within the city, but overall, domestic wood burning is more important for the organic aerosol concentrations in Zurich during winter time (varying between 8–15% of PM1 for different sites within the city. OOA makes up the largest fraction of organic aerosol (44% on average. A new method, based on simultaneous on-road mobile and stationary background measurements and using the ratio of on-road sulfate to stationary sulfate to correct for small-scale dynamic effects, allows for the separation of PM1 emitted or produced locally and the PM1 from the regional background. It could be shown that especially during thermal inversions over the Swiss plateau, regional background concentrations contribute substantially to particulate number concentrations (60% on average as well as to the concentrations of PM1 components (on average 60% for black carbon and HOA, over 97% for WBOA and OOA, and more than 94% for the measured inorganic components in downtown Zurich. The results emphasize, on

  19. Aerosolization, Chemical Characterization, Hygroscopicity and Ice Formation of Marine Biogenic Particles

    Science.gov (United States)

    Alpert, P. A.; Radway, J.; Kilthau, W.; Bothe, D.; Knopf, D. A.; Aller, J. Y.

    2013-12-01

    The oceans cover the majority of the earth's surface, host nearly half the total global primary productivity and are a major source of atmospheric aerosol particles. However, effects of biological activity on sea spray generation and composition, and subsequent cloud formation are not well understood. Our goal is to elucidate these effects which will be particularly important over nutrient rich seas, where microorganisms can reach concentrations of 10^9 per mL and along with transparent exopolymer particles (TEP) can become aerosolized. Here we report the results of mesocosm experiments in which bubbles were generated by two methods, either recirculating impinging water jets or glass frits, in natural or artificial seawater containing bacteria and unialgal cultures of three representative phytoplankton species, Thalassiosira pseudonana, Emiliania huxleyi, and Nannochloris atomus. Over time we followed the size distribution of aerosolized particles as well as their hygroscopicity, heterogeneous ice nucleation potential, and individual physical-chemical characteristics. Numbers of cells and the mass of dissolved and particulate organic carbon (DOC, POC), TEP (which includes polysaccharide-containing microgels and nanogels >0.4 μm in diameter) were determined in the bulk water, the surface microlayer, and aerosolized material. Aerosolized particles were also impacted onto substrates for ice nucleation and water uptake experiments, elemental analysis using computer controlled scanning electron microscopy and energy dispersive analysis of X-rays (CCSEM/EDX), and determination of carbon bonding with scanning transmission X-ray microscopy and near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Regardless of bubble generation method, the overall concentration of aerosol particles, TEP, POC and DOC increased as concentrations of bacterial and phytoplankton cells increased, stabilized, and subsequently declined. Particles air. Our results provide improved

  20. Observation operator for the assimilation of aerosol type resolving satellite measurements into a chemical transport model

    Directory of Open Access Journals (Sweden)

    M. Schroedter-Homscheidt

    2010-11-01

    Full Text Available Modelling of aerosol particles with chemical transport models is still based mainly on static emission databases while episodic emissions cannot be treated sufficiently. To overcome this situation, a coupling of chemical mass concentration modelling with satellite-based measurements relying on physical and optical principles has been developed. This study deals with the observation operator for a component-wise assimilation of satellite measurements. It treats aerosol particles classified into water soluble, water insoluble, soot, sea salt and mineral dust containing aerosol particles in the atmospheric boundary layer as separately assimilated aerosol components. It builds on a mapping of aerosol classes used both in observation and model space taking their optical and chemical properties into account. Refractive indices for primary organic carbon particles, anthropogenic particles, and secondary organic species have been defined based on a literature review. Together with a treatment of different size distributions in observations and model state, this allows transforming the background from mass concentrations into aerosol optical depths. A two-dimensional, variational assimilation is applied for component-wise aerosol optical depths. Error covariance matrices are defined based on a validation against AERONET sun photometer measurements. Analysis fields are assessed threefold: (1 through validation against AERONET especially in Saharan dust outbreak situations, (2 through comparison with the British Black Smoke and Sulphur Dioxide Network for soot-containing particles, and (3 through comparison with measurements of the water soluble components SO4, NH4, and NO3 conducted by the EMEP (European Monitoring and Evaluation Programme network. Separately, for the water soluble, the soot and the mineral dust aerosol components a bias reduction and subsequent a root mean square error reduction is observed in the

  1. Sensitive chemical compass assisted by quantum criticality

    Science.gov (United States)

    Cai, C. Y.; Ai, Qing; Quan, H. T.; Sun, C. P.

    2012-02-01

    A radical-pair-based chemical reaction might be used by birds for navigation via the geomagnetic direction. The inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could respond to a weak magnetic field and be sensitive to the direction of such a field; this then results in different photopigments to be sensed by the avian eyes. Here, we propose a quantum bionic setup, inspired by the avian compass, as an ultrasensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of detection of weak magnetic fields.

  2. Sensitive Chemical Compass Assisted by Quantum Criticality

    CERN Document Server

    Cai, C Y; Quan, H T; Sun, C P

    2011-01-01

    The radical-pair-based chemical reaction could be used by birds for the navigation via the geomagnetic direction. An inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could response to the weak magnetic field and be sensitive to the direction of such a field and then results in different photopigments in the avian eyes to be sensed. Here, we propose a quantum bionic setup for the ultra-sensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via the recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of the detection of the weak magnetic field.

  3. Chemical composition, main sources and temporal variability of PM1 aerosols in southern African grassland

    Science.gov (United States)

    Tiitta, P.; Vakkari, V.; Josipovic, M.; Croteau, P.; Beukes, J. P.; van Zyl, P. G.; Venter, A. D.; Jaars, K.; Pienaar, J. J.; Ng, N. L.; Canagaratna, M. R.; Jayne, J. T.; Kerminen, V.-M.; Kulmala, M.; Laaksonen, A.; Worsnop, D. R.; Laakso, L.

    2013-06-01

    Southern Africa is a significant source region of atmospheric pollution, yet long-term data on pollutant concentrations and properties from this region are rather limited. A recently established atmospheric measurement station in South Africa, Welgegund, is strategically situated to capture regional background emissions, as well as emissions from the major source regions in the interior of South Africa. We measured non-refractive submicron aerosols (NR-PM1) and black carbon over a one year period in Welgegund, and investigated the seasonal and diurnal patterns of aerosol concentration levels, chemical composition, acidity and oxidation level. Based on air mass back trajectories, four distinct source regions were determined for NR-PM1. Supporting data utilized in our analysis included particle number size distributions, aerosol absorption, trace gas concentrations, meteorological variables and the flux of carbon dioxide. The dominant submicron aerosol constituent during the dry season was organic aerosol, reflecting high contribution from savannah fires and other combustion sources. Organic aerosol concentrations were lower during the wet season, presumably due to wet deposition as well as reduced emissions from combustion sources. Sulfate concentrations were usually high and exceeded organic aerosol concentrations when air-masses were transported over regions containing major point sources. Sulfate and nitrate concentrations peaked when air masses passed over the industrial Highveld (iHV) area. In contrast, concentrations were much lower when air masses passed over the cleaner background (BG) areas. Air masses associated with the anti-cyclonic recirculation (ACBIC) source region contained largely aged OA. Positive Matrix Factorization (PMF) analysis of aerosol mass spectra was used to characterize the organic aerosol (OA) properties. The factors identified were oxidized organic aerosols (OOA) and biomass burning organic aerosols (BBOA) in the dry season and low

  4. Size distribution measurements and chemical analysis of aerosol components

    Energy Technology Data Exchange (ETDEWEB)

    Pakkanen, T.A.

    1995-12-31

    The principal aims of this work were to improve the existing methods for size distribution measurements and to draw conclusions about atmospheric and in-stack aerosol chemistry and physics by utilizing size distributions of various aerosol components measured. A sample dissolution with dilute nitric acid in an ultrasonic bath and subsequent graphite furnace atomic absorption spectrometric analysis was found to result in low blank values and good recoveries for several elements in atmospheric fine particle size fractions below 2 {mu}m of equivalent aerodynamic particle diameter (EAD). Furthermore, it turned out that a substantial amount of analyses associated with insoluble material could be recovered since suspensions were formed. The size distribution measurements of in-stack combustion aerosols indicated two modal size distributions for most components measured. The existence of the fine particle mode suggests that a substantial fraction of such elements with two modal size distributions may vaporize and nucleate during the combustion process. In southern Norway, size distributions of atmospheric aerosol components usually exhibited one or two fine particle modes and one or two coarse particle modes. Atmospheric relative humidity values higher than 80% resulted in significant increase of the mass median diameters of the droplet mode. Important local and/or regional sources of As, Br, I, K, Mn, Pb, Sb, Si and Zn were found to exist in southern Norway. The existence of these sources was reflected in the corresponding size distributions determined, and was utilized in the development of a source identification method based on size distribution data. On the Finnish south coast, atmospheric coarse particle nitrate was found to be formed mostly through an atmospheric reaction of nitric acid with existing coarse particle sea salt but reactions and/or adsorption of nitric acid with soil derived particles also occurred. Chloride was depleted when acidic species reacted

  5. Estimation of aerosol water and chemical composition from AERONET at Cabauw, the Netherlands, Atmos. Chem. Phys. Discuss., 13, ,

    NARCIS (Netherlands)

    Beelen, A.J. van; Roelofs, G.J.H.; Hasekamp, O.P.; Henzing, J.S.; Röckmann, T.

    2013-01-01

    This study is of our particular interest as the quality of our chemical transport model Lotos-Euros can be improved by our understanding of the aerosol-light interaction. In this study we derive aerosol water and chemical composition by a modeling approach that combines in situ measured and remotely

  6. Effects of Chemical Aging on the Heterogeneous Freezing of Organic Aerosols

    Science.gov (United States)

    Collier, K.; Brooks, S. D.

    2014-12-01

    Organic aerosols are emitted into the atmosphere from a variety of sources and display a wide range of effectiveness in promoting the nucleation of ice in clouds. Soot and polycyclic aromatic hydrocarbons (PAHS) arise from incomplete combustion and other pollutant sources. Hydrocarbon compounds in diesel motor oil and other fuel blends include compounds such as octacosane (a straight saturated alkane), squalane (a branched saturated alkane) and squalene (an unsaturated branched alkene). At temperatures above -36°C, the formation of ice crystals in the atmosphere is facilitated by heterogeneous freezing processes in which atmospheric aerosols act as ice nuclei (IN). The variability in ability of organic particles to facilitate heterogeneous ice nucleation causes major uncertainties in predictions of aerosol effects on climate. Further, atmospheric aerosol composition and ice nucleation ability can be altered via chemical aging and reactions with atmospheric oxidants such as ozone. In this study, we take a closer look at the role of chemical oxidation on the efficiency of specific IN during contact freezing laboratory experiments. The freezing temperatures of droplets in contact with representative organic aerosols are determined through the use of an optical microscope apparatus equipped with a cooling stage and a digital camera. Chemical changes at the surface of aerosols due to ozone exposure are characterized using Raman Microspectroscopy and Fourier Transform Infrared Spectroscopy with Horizontal Attenuated Total Reflectance. Our results indicate that oxidation of certain atmospheric organics (soot and PAHS) enhances their ice nucleation ability. In this presentation, results of heterogeneous nucleation on various types of organic aerosols will be presented, and the role of structure in promoting freezing will be discussed.

  7. Production Mechanism, Number Concentration, Size Distribution, Chemical Composition, and Optical Properties of Sea Spray Aerosols Workshop, Summer 2012

    Energy Technology Data Exchange (ETDEWEB)

    Meskhidze, Nicholas [NCSU

    2013-10-21

    The objective of this workshop was to address the most urgent open science questions for improved quantification of sea spray aerosol-radiation-climate interactions. Sea spray emission and its influence on global climate remains one of the most uncertain components of the aerosol-radiation-climate problem, but has received less attention than other aerosol processes (e.g. production of terrestrial secondary organic aerosols). Thus, the special emphasis was placed on the production flux of sea spray aerosol particles, their number concentration and chemical composition and properties.

  8. The application of thermal methods for determining chemical composition of carbonaceous aerosols: a review.

    Science.gov (United States)

    Chow, Judith C; Yu, Jian Zhen; Watson, John G; Ho, Steven Sai Hang; Bohannan, Theresa L; Hays, Michael D; Fung, Kochy K

    2007-09-01

    Thermal methods of various forms have been used to quantify carbonaceous materials. Thermal/optical carbon analysis provides measurements of organic and elemental carbon concentrations as well as fractions evolving at specific temperatures in ambient and source aerosols. Detection of thermally desorbed organic compounds with thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) identifies and quantifies over 100 individual organic compounds in particulate matter (PM) samples. The resulting mass spectra contain information that is consistent among, but different between, source emissions even in the absence of association with specific organic compounds. TD-GC/MS is a demonstrated alternative to solvent extraction for many organic compounds and can be applied to samples from existing networks. It is amenable to field-deployable instruments capable of measuring organic aerosol composition in near real-time. In this review, thermal stability of organic compounds is related to chemical structures, providing a basis for understanding thermochemical properties of carbonaceous aerosols. Recent advances in thermal methods applied to determine aerosol chemical compositions are summarized and their potential for uncovering aerosol chemistry are evaluated. Current limitations and future research needs of the thermal methods are included.

  9. Modelling of primary aerosols in the chemical transport model MOCAGE: development and evaluation of aerosol physical parameterizations

    Science.gov (United States)

    Sič, B.; El Amraoui, L.; Marécal, V.; Josse, B.; Arteta, J.; Guth, J.; Joly, M.; Hamer, P. D.

    2015-02-01

    This paper deals with recent improvements to the global chemical transport model of Météo-France MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle) that consists of updates to different aerosol parameterizations. MOCAGE only contains primary aerosol species: desert dust, sea salt, black carbon, organic carbon, and also volcanic ash in the case of large volcanic eruptions. We introduced important changes to the aerosol parameterization concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant source function is introduced for sea salt aerosols. Wet deposition is modified toward a more physically realistic representation by introducing re-evaporation of falling rain and snowfall scavenging and by changing the in-cloud scavenging scheme along with calculations of precipitation cloud cover and rain properties. The sedimentation scheme update includes changes regarding the stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI), the ground (AERONET, EMEP), and a model inter-comparison project (AeroCom) are compared with MOCAGE simulations and show that the introduced changes brought a significant improvement on aerosol representation, properties and global distribution. Emitted quantities of desert dust and sea salt, as well their lifetimes, moved closer towards values of AeroCom estimates and the multi-model average. When comparing the model simulations with MODIS aerosol optical depth (AOD) observations over the oceans, the updated model configuration shows a decrease in the modified normalized mean bias (MNMB; from 0.42 to 0.10) and a better correlation (from 0.06 to 0.32) in terms of the geographical distribution and the temporal variability. The updates corrected a strong positive MNMB in the sea salt representation at high latitudes (from 0.65 to 0.16), and a negative MNMB in the desert

  10. Modelling of primary aerosols in the chemical transport model MOCAGE: development and evaluation of aerosol physical parameterizations

    Directory of Open Access Journals (Sweden)

    B. Sič

    2015-02-01

    Full Text Available This paper deals with recent improvements to the global chemical transport model of Météo-France MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle that consists of updates to different aerosol parameterizations. MOCAGE only contains primary aerosol species: desert dust, sea salt, black carbon, organic carbon, and also volcanic ash in the case of large volcanic eruptions. We introduced important changes to the aerosol parameterization concerning emissions, wet deposition and sedimentation. For the emissions, size distribution and wind calculations are modified for desert dust aerosols, and a surface sea temperature dependant source function is introduced for sea salt aerosols. Wet deposition is modified toward a more physically realistic representation by introducing re-evaporation of falling rain and snowfall scavenging and by changing the in-cloud scavenging scheme along with calculations of precipitation cloud cover and rain properties. The sedimentation scheme update includes changes regarding the stability and viscosity calculations. Independent data from satellites (MODIS, SEVIRI, the ground (AERONET, EMEP, and a model inter-comparison project (AeroCom are compared with MOCAGE simulations and show that the introduced changes brought a significant improvement on aerosol representation, properties and global distribution. Emitted quantities of desert dust and sea salt, as well their lifetimes, moved closer towards values of AeroCom estimates and the multi-model average. When comparing the model simulations with MODIS aerosol optical depth (AOD observations over the oceans, the updated model configuration shows a decrease in the modified normalized mean bias (MNMB; from 0.42 to 0.10 and a better correlation (from 0.06 to 0.32 in terms of the geographical distribution and the temporal variability. The updates corrected a strong positive MNMB in the sea salt representation at high latitudes (from 0.65 to 0.16, and a negative MNMB in

  11. Chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx

    Directory of Open Access Journals (Sweden)

    J. Kazil

    2011-02-01

    Full Text Available Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN. Potential sources include wind-driven production of sea salt particles from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate aerosol sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We introduce the new features of the model and conduct simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx. The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell wall updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation proceeds efficiently. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number

  12. Decadal trends in aerosol chemical composition at Barrow, Alaska: 1976–2008

    Directory of Open Access Journals (Sweden)

    G. E. Shaw

    2009-11-01

    Full Text Available Aerosol measurements at Barrow, Alaska during the past 30 years have identified the long range transport of pollution associated with Arctic Haze as well as ocean-derived aerosols of more local origin. Here, we focus on measurements of aerosol chemical composition to assess (1 trends in Arctic Haze aerosol and implications for source regions, (2 the interaction between pollution-derived and ocean-derived aerosols and the resulting impacts on the chemistry of the Arctic boundary layer, and (3 the response of aerosols to a changing climate. Aerosol chemical composition measured at Barrow, AK during the Arctic haze season is compared for the years 1976–1977 and 1997–2008. Based on these two data sets, concentrations of non-sea salt (nss sulfate (SO4= and non-crustal (nc vanadium (V have decreased by about 60% over this 30 year period. Consistency in the ratios of nss SO4=/ncV and nc manganese (Mn/ncV between the two data sets indicates that, although emissions have decreased in the source regions, the source regions have remained the same over this time period. The measurements from 1997–2008 indicate that, during the haze season, the nss SO4= aerosol at Barrow is becoming less neutralized by ammonium (NH4+ yielding an increasing sea salt aerosol chloride (Cl deficit. The expected consequence is an increase in the release of Cl atoms to the atmosphere and a change in the lifetime of volatile organic compounds (VOCs including methane. In addition, summertime concentrations of biogenically-derived methanesulfonate (MSA and nss SO4= are increasing at a rate of 12 and 8% per year, respectively. Further research is required to assess the environmental factors behind the increasing concentrations of biogenic aerosol.

  13. Decadal trends in aerosol chemical composition at Barrow, AK: 1976–2008

    Directory of Open Access Journals (Sweden)

    P. K. Quinn

    2009-09-01

    Full Text Available Aerosol measurements at Barrow, AK during the past 30 years have identified the long range transport of pollution associated with Arctic Haze as well as ocean-derived aerosols of more local origin. Here, we focus on measurements of aerosol chemical composition to assess 1 trends in Arctic Haze aerosol and implications for source regions, 2 the interaction between pollution-derived and ocean-derived aerosols and the resulting impacts on the chemistry of the Arctic boundary layer, and 3 the response of aerosols to a changing climate. Aerosol chemical composition measured at Barrow, AK during the Arctic haze season is compared for the years 1976–1977 and 1997–2008. Based on these two data sets, concentrations of non-sea salt (nss sulfate (SO4= and non-crustal (nc vanadium (V have decreased by about 60% over this 30 year period. Consistency in the ratios of nss SO4=/ncV and nc manganese (Mn/ncV between the two data sets indicates that, although emissions have decreased in the source regions, the source regions have remained the same over this time period. The measurements from 1997–2008 indicate that, during the haze season, the nss SO4= aerosol at Barrow is becoming less neutralized by ammonium (NH4+ yielding an increasing sea salt aerosol chloride (Cl deficit. The expected consequence is an increase in the release of Cl atoms to the atmosphere and a change in the lifetime of volatile organic compounds (VOCs including methane. In addition, summertime concentrations of biogenically-derived methanesulfonate (MSA and nss SO4= are increasing at a rate of 12 and 8% per year, respectively. Further research is required to assess the environmental factors behind the increasing concentrations of biogenic aerosol.

  14. Measurements of Sea Salt Aerosols in the Marine Boundary Layer and Free Troposphere: Vertical Transport and Chemical Transformation

    Science.gov (United States)

    Hudson, P. K.; Murphy, D. M.; Cziczo, D. J.; Thomson, D. S.

    2002-12-01

    During the Intercontinental Transport and Chemical Transformation (ITCT) mission (Monterey, CA, spring 2002) nearly 400,000 positive and negative mass spectra of single atmospheric aerosols were acquired using the PALMS (Particle Analysis by Laser Mass Spectrometry) instrument. The primary focus of the mission was to investigate the composition of air masses along the western coast of the United States. Of particular interest to the mission was to study the influence of anthropogenic emissions from Asia on aerosol composition. To accomplish these goals, the WP-3 aircraft, equipped with a suite of instruments including PALMS, covered a large spatial area flying from 0 - 8000 m altitude covering most of the western coastline from Canada to southern California including flights over the San Francisco and Los Angeles metropolitan areas. The in situ measurements of single particle aerosol mass spectra by PALMS allow for good spatial and vertical resolution of the aerosol composition. By observing the changes in aerosol composition as a function of altitude, the vertical transport of sea salt aerosols over marine and urban environments is examined. Using measurements of other chemical tracers along with the aerosol composition, the chemical processing of these aerosols during transport both vertically and inland can be discerned. These results add insight into the transport and chemical evolution of sea salt aerosol.

  15. Chemical composition of aerosol in the atmospheric surface layer of the East Antarctica coastal zone

    Directory of Open Access Journals (Sweden)

    L. P. Golobokova

    2016-01-01

    Full Text Available Chemical composition of aerosol in the ground layer of the coastal zone in East Antarctica is analyzed in the article. The aerosol samples were taken in 2006–2015 during seasonal works of the Russian Antarctic Expeditions (RAE, namely, these were 52nd–53rd, 55th, and 58th–60th expeditions. Samples were taken in the 200‑km band of the sea-shore zone along routes of the research vessels (REV «Akademik Fedorov» and «Akademik Treshnikov» as well as on territories of the Russian stations Molodezhnaya and Mirny. Although the results obtained did show the wide range of the aerosol concentrations and a certain variability of their chemical composition, some common features of the variability were revealed. Thus, during the period from 2006 to 2014 a decrease of average values of the sums were noted. Spatially, a tendency of decreasing of the ion concentrations was found in the direction from the station Novolazarevskaya to the Molodezhnaya one, but the concentrations increased from the Molodezhnaya to the station Mirny. The sum of ions of the aerosol in the above mentioned coastal zone was, on the average, equal to 2.44 μg/m3, and it was larger than that on the territory of the Antarctic stations Molodezhnaya (0,29 μg/m3 and Mirny (0,50 ág / m3. The main part to the sum of the aerosol ions on the Antarctic stations was contributed by Na+, Ca2+, Cl−, SO4 2−. The main ions in aerosol composition in the coastal zone are ions Na+ and Cl−. The dominant contribution of the sea salt and SO4 2− can be traced in not only the composition of atmospheric aerosols, but also in the chemical composition of the fresh snow in the coastal areas of East Antarctica: at the Indian station Maitri, on the Larsemann Hills, and in a boring located in 55.3 km from the station Progress (K = 1.4÷6.1. It was noted that values of the coefficient of enrichment K of these ions decreases as someone moves from a shore to inland. Estimation of

  16. Fabrication of bimetallic nanostructures via aerosol-assisted electroless silver deposition for catalytic CO conversion.

    Science.gov (United States)

    Byeon, Jeong Hoon; Kim, Jang-Woo

    2014-03-12

    Bimetallic nanostructures were fabricated via aerosol-assisted electroless silver deposition for catalytic CO conversion. An ambient spark discharge was employed to produce nanocatalysts, and the particles were directly deposited on a polytetrafluoroethylene substrate for initiating silver deposition to form Pd-Ag, Pt-Ag, Au-Ag bimetallic nanostructures as well as a pure Ag nanostructure. Kinetics and morphological evolutions in the silver deposition with different nanocatalysts were comparatively studied. The Pt catalyst displayed the highest catalytic activity for electroless silver deposition, followed by the order Pd > Au > Ag. Another catalytic activity of the fabricated bimetallic structures in the carbon monoxide conversion was further evaluated at low-temperature conditions. The bimetallic systems showed significantly higher catalytic activity than that from a pure Ag system.

  17. Chemical analysis of plasma-assisted antimicrobial treatment on cotton

    Science.gov (United States)

    Kan, C. W.; Lam, Y. L.; Yuen, C. W. M.; Luximon, A.; Lau, K. W.; Chen, K. S.

    2013-06-01

    This paper explores the use of plasma treatment as a pretreatment process to assist the application of antimicrobial process on cotton fabric with good functional effect. In this paper, antimicrobial finishing agent, Microfresh Liquid Formulation 9200-200 (MF), and a binder (polyurethane dispersion, Microban Liquid Formulation R10800-0, MB) will be used for treating the cotton fabric for improving the antimicrobial property and pre-treatment of cotton fabric by plasma under atmospheric pressure will be employed to improve loading of chemical agents. The chemical analysis of the treated cotton fabric will be conducted by Fourier transform Infrared Spectroscopy.

  18. Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques

    Science.gov (United States)

    Decesari, S.; Allan, J.; Plass-Duelmer, C.; Williams, B. J.; Paglione, M.; Facchini, M. C.; O'Dowd, C.; Harrison, R. M.; Gietl, J. K.; Coe, H.; Giulianelli, L.; Gobbi, G. P.; Lanconelli, C.; Carbone, C.; Worsnop, D.; Lambe, A. T.; Ahern, A. T.; Moretti, F.; Tagliavini, E.; Elste, T.; Gilge, S.; Zhang, Y.; Dall'Osto, M.

    2014-11-01

    The use of co-located multiple spectroscopic techniques can provide detailed information on the atmospheric processes regulating aerosol chemical composition and mixing state. So far, field campaigns heavily equipped with aerosol mass spectrometers have been carried out mainly in large conurbations and in areas directly affected by their outflow, whereas lesser efforts have been dedicated to continental areas characterised by a less dense urbanisation. We present here the results obtained at a background site in the Po Valley, Italy, in summer 2009. For the first time in Europe, six state-of-the-art spectrometric techniques were used in parallel: aerosol time-of-flight mass spectrometer (ATOFMS), two aerosol mass spectrometers (high-resolution time-of-flight aerosol mass spectrometer - HR-ToF-AMS and soot particle aerosol mass spectrometer - SP-AMS), thermal desorption aerosol gas chromatography (TAG), chemical ionisation mass spectrometry (CIMS) and (offline) proton nuclear magnetic resonance (1H-NMR) spectroscopy. The results indicate that, under high-pressure conditions, atmospheric stratification at night and early morning hours led to the accumulation of aerosols produced by anthropogenic sources distributed over the Po Valley plain. Such aerosols include primary components such as black carbon (BC), secondary semivolatile compounds such as ammonium nitrate and amines and a class of monocarboxylic acids which correspond to the AMS cooking organic aerosol (COA) already identified in urban areas. In daytime, the entrainment of aged air masses in the mixing layer is responsible for the accumulation of low-volatility oxygenated organic aerosol (LV-OOA) and also for the recycling of non-volatile primary species such as black carbon. According to organic aerosol source apportionment, anthropogenic aerosols accumulating in the lower layers overnight accounted for 38% of organic aerosol mass on average, another 21% was accounted for by aerosols recirculated in

  19. Eddy covariance measurements with high-resolution time-of-flight aerosol mass spectrometry: a new approach to chemically-resolved aerosol fluxes

    Directory of Open Access Journals (Sweden)

    D. K. Farmer

    2010-12-01

    Full Text Available Although laboratory studies show that biogenic volatile organic compounds (VOCs yield substantial secondary organic aerosol (SOA, production of biogenic SOA as indicated by upward fluxes has not been conclusively observed over forests. Further, while aerosols are known to deposit to surfaces, few techniques exist to provide chemically-resolved particle deposition fluxes. To better constrain aerosol sources and sinks, we have developed a new technique to directly measure fluxes of chemically-resolved submicron aerosols using the high-resolution time-of-flight aerosol mass spectrometer (HR-AMS in a new, fast eddy covariance mode. This approach takes advantage of the instrument's ability to quantitatively identify both organic and inorganic components, including ammonium, sulphate and nitrate, at a temporal resolution of several Hz. The new approach has been successfully deployed over a temperate ponderosa pine plantation in California during the BEARPEX-2007 campaign, providing both total and chemically resolved non-refractory (NR PM1 fluxes. Average deposition velocity for total NR-PM1 aerosol at noon was 2.05 ± 0.04 mm/s. Using a high resolution measurement of the NH2+ and NH3+ fragments, we demonstrate the first eddy covariance flux measurements of particulate ammonium, which show a noon-time deposition velocity of 1.9 ± 0.7 mm/s and are dominated by deposition of ammonium sulphate.

  20. Chemical composition, sources, and processes of urban aerosols during summertime in Northwest China: insights from High Resolution Aerosol Mass Spectrometry

    Science.gov (United States)

    Xu, J.; Zhang, Q.; Chen, M.; Ge, X.; Ren, J.; Qin, D.

    2014-06-01

    An aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed along with a Scanning Mobility Particle Sizer (SMPS) and a Multi Angle Absorption Photometers (MAAP) to measure the temporal variations of the mass loading, chemical composition, and size distribution of sub-micrometer particulate matter (PM1) in Lanzhou, northwest China, during 12 July-7 August 2012. The average PM1 mass concentration including non-refractory PM1 (NR-PM1) measured by HR-ToF-AMS and black carbon (BC) measured by MAAP during this study was 24.5 μg m-3 (ranging from 0.86 to 105μg m-3), with a mean composition consisting of 47% organics, 16% sulfate, 12% BC, 11% ammonium, 10% nitrate, and 4% chloride. The organics was consisted of 70% carbon, 21% oxygen, 8% hydrogen, and 1% nitrogen, with the average oxygen-to-carbon ratio (O / C) of 0.33 and organic mass-to-carbon ratio (OM / OC) of 1.58. Positive matrix factorization (PMF) of the high-resolution mass spectra of organic aerosols (OA) identified four distinct factors which represent, respectively, two primary OA (POA) emission sources (traffic and food cooking) and two secondary OA (SOA) types - a fresher, semi-volatile oxygenated OA (SV-OOA) and a more aged, low-volatility oxygenated OA (LV-OOA). Traffic-related hydrocarbon-like OA (HOA) and BC displayed distinct diurnal patterns both with peak at ~07:00-11:00 (BJT: UTC +8) corresponding to the morning rush hours, while cooking OA (COA) peaked during three meal periods. The diurnal profiles of sulfate and LV-OOA displayed a broad peak between ∼07:00-15:00, while those of nitrate, ammonium, and SV-OOA showed a narrower peak at ~08:00-13:00. The later morning and early afternoon peak in the diurnal profiles of secondary aerosol species was likely caused by mixing down of pollutants aloft, which were likely produced in the residual layer decoupled from the boundary layer during night time. The mass spectrum of SV-OOA also showed similarity with that of

  1. Hygroscopic properties of the Paris urban aerosol in relation to its chemical composition

    Directory of Open Access Journals (Sweden)

    K. A. Kamilli

    2013-05-01

    Full Text Available Aerosol hygroscopic growth factors and chemical properties were measured as part of the MEGAPOLI "Megacities Plume Case Study" at the urban site LHVP in the city center of Paris from June to August 2009, and from January to February 2010. Descriptive hygroscopic growth factors (DGF were derived in the diameter range from 25 to 350 nm at relative humidities of 30, 55, 75, and 90% by applying the summation method on humidified and dry aerosol size distributions measured simultaneously with a humidified differential mobility particle sizer (HDMPS and a twin differential mobility particle sizer (TDMPS. For 90% relative humidity, the DGF varied from 1.06 to 1.46 in summer, and from 1.06 to 1.66 in winter. Temporal variations in the observed mean DGF could be well explained with a simple growth model based on the aerosol chemical composition measured by aerosol mass spectrometry (AMS and black carbon photometry (MAAP. In particular, good agreement was observed when sulfate was the predominant inorganic factor. A clear overestimation of the predicted growth factor was found when the nitrate mass concentration exceeded values of 10 μg m3, e.g. during winter.

  2. Hygroscopic properties of the Paris urban aerosol in relation to its chemical composition

    Science.gov (United States)

    Kamilli, K. A.; Poulain, L.; Held, A.; Nowak, A.; Birmili, W.; Wiedensohler, A.

    2014-01-01

    Aerosol hygroscopic growth factors and chemical properties were measured as part of the MEGAPOLI "Megacities Plume Case Study" at the urban site Laboratoire d'Hygiène de la Ville de Paris (LHVP) in the city center of Paris from June to August 2009, and from January to February 2010. Descriptive hygroscopic growth factors (DGF) were derived in the diameter range from 25 to 350 nm at relative humidities of 30, 55, 75, and 90% by applying the summation method on humidified and dry aerosol size distributions measured simultaneously with a humidified differential mobility particle sizer (HDMPS) and a twin differential mobility particle sizer (TDMPS). For 90% relative humidity, the DGF varied from 1.06 to 1.46 in summer, and from 1.06 to 1.66 in winter. Temporal variations in the observed mean DGF could be well explained with a simple growth model based on the aerosol chemical composition measured by aerosol mass spectrometry (AMS) and black carbon photometry (MAAP). In particular, good agreement was observed when sulfate was the predominant inorganic factor. A clear overestimation of the predicted growth factor was found when the nitrate mass concentration exceeded values of 10 μg m-3, e.g., during winter.

  3. Surface Modification of Aerosol-Assisted CVD Produced TiO2 Thin Film for Dye Sensitised Solar Cell

    Directory of Open Access Journals (Sweden)

    SuPei Lim

    2014-01-01

    Full Text Available We report a simple and convenient method for the preparation of Ag/TiO2 thin films supported on indium tin oxide, which was achieved by sonochemical deposition of Ag+ on aerosol-assisted chemical vapour deposited TiO2 thin films. Posttreatment was performed on the film by immersion in HCl. The as-prepared composite film was characterised by X-ray diffraction, ultraviolet-visible absorption spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy. The photoelectrochemical measurements and J-V characterisation showed approximately fivefold increase in photocurrent density generation and approximately sevenfold enhancement in dye sensitiser solar cell (DSSC conversion efficiency, which was achieved after modification of the TiO2 film with HCl posttreatment and Ag particle deposition. The improved photocurrent density of 933.30 μA/cm2, as well as DSSC power conversion efficiency of 3.63% with high stability, is an indication that the as-synthesised thin film is a potential candidate for solar energy conversion applications.

  4. Chemical Composition of Atmospheric Aerosols Above a Pristine South East Asian Rainforest

    Science.gov (United States)

    Robinson, N. H.; Allan, J. D.; Williams, P. I.; Coe, H.; Hamilton, J.; Chen, Q.; Martin, S.; Trembath, J.

    2009-04-01

    conjunction with a constant pressure inlet. The aerosols' chemical origins have been further investigated by comparing these spectra to chamber experiments, mass spectral libraries and data from comparable experiments in other locations. These data are also being analysed in conjunction with offline techniques applied to samples collected using filters and a Particle-Into-Liquid Sampler (PILS). Methods used include liquid chromatography and comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry. These techniques provide a more detailed chemical characterisation of the SOA and water soluble organic carbon, allowing direct links back to gas phase precursors. In conjunction with the field measurements, a programme of chamber experiments is being carried out at Manchester as part of the ACES project. This will generate comparable SOA under controlled conditions and subjecting them to similar analysis.

  5. Investigations of microphysical and chemical composition of aerosol in near-water layer of the atmosphere over the White Sea

    Science.gov (United States)

    Panchenko, Mikhail V.; Kozlov, Valerii S.; Pol'kin, Victor V.; Golobokova, Lyudmila P.; Pogodaeva, Tatyana V.; Khodzher, Tamara V.; Lisitzin, Alexander P.; Shevchenko, Vladimir P.

    2006-11-01

    The peculiarities of spatial-temporal variability of the submicron aerosol number density N Σ (cm -3), particle size distribution in the diameter range 0.4 to 10 μm, mass concentration of submicron aerosol Ma (μg/m 3) and the mass concentration of black carbon (soot, BC) Ms (μg/m 3), as well as chemical composition of particles (ion composition of aerosol soluble fraction) in different regions of White Sea are considered in this paper. The effect of continental and marine sources on formation of the near-water aerosol characteristics is estimated.

  6. Biomass burning aerosol over the Amazon during SAMBBA: impact of chemical composition on radiative properties

    Science.gov (United States)

    Morgan, William; Allan, James; Flynn, Michael; Darbyshire, Eoghan; Hodgson, Amy; Liu, Dantong; O'shea, Sebastian; Bauguitte, Stephane; Szpek, Kate; Langridge, Justin; Johnson, Ben; Haywood, Jim; Longo, Karla; Artaxo, Paulo; Coe, Hugh

    2014-05-01

    Biomass burning represents one of the largest sources of particulate matter to the atmosphere, resulting in a significant perturbation to the Earth's radiative balance coupled with serious impacts on public health. Globally, biomass burning aerosols are thought to exert a small warming effect but with the uncertainty being 4 times greater than the central estimate. On regional scales, the impact is substantially greater, particularly in areas such as the Amazon Basin where large, intense and frequent burning occurs on an annual basis for several months. Absorption by atmospheric aerosols is underestimated by models over South America, which points to significant uncertainties relating to Black Carbon (BC) aerosol properties. Initial results from the South American Biomass Burning Analysis (SAMBBA) field experiment, which took place during September and October 2012 over Brazil on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft, are presented here. Aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and a DMT Single Particle Soot Photometer (SP2). The physical, chemical and optical properties of the aerosols across the region will be characterized in order to establish the impact of biomass burning on regional air quality, weather and climate. The aircraft sampled a range of conditions including sampling of pristine Rainforest, fresh biomass burning plumes, regional haze and elevated biomass burning layers within the free troposphere. The aircraft sampled biomass burning aerosol across the southern Amazon in the states of Rondonia and Mato Grosso, as well as in a Cerrado (Savannah-like) region in Tocantins state. This presented a range of fire conditions, both in terms of their number, intensity, vegetation-type and their combustion efficiencies. Near-source sampling of fires in Rainforest environments suggested that smouldering combustion dominated, while flaming combustion dominated

  7. Optical, physical and chemical characteristics of Australian Desert dust aerosols: results from a field experiment

    Directory of Open Access Journals (Sweden)

    M. D. Keywood

    2009-11-01

    Full Text Available Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the northern hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol. Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – both ion beam analysis and ion chromatography.

    The aerosol optical depth data showed a weak seasonal cycle with an annual mean of 0.06±0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. Size distribution inversions showed a bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of biomass burning and marine biogenic material. Ion Beam Analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated, with the Fe/Si ratio higher than the crustal average, as expected. Scatter plots for Ca, Mn and K against Si showed clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. Ion Chromatography was used to quantify water soluble ions for 2 of our sample sets, showing the importance of marine influences on both fine (biogenic and

  8. Daily and hourly chemical impact of springtime transboundary aerosols on Japanese air quality

    Directory of Open Access Journals (Sweden)

    T. Moreno

    2013-02-01

    Full Text Available The regular eastward drift of transboundary aerosol intrusions from the Asian mainland into the NW Pacific region has a pervasive impact on air quality in Japan, especially during springtime. Analysis of 24-h filter samples with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES and Mass Spectrometry (ICP-MS, and hourly Streaker with Particle Induced X-ray Emission (PIXE samples collected continuously for six weeks reveal the chemistry of successive waves of natural mineral desert dust ("Kosa" and metalliferous sulphatic pollutants arriving in western Japan during spring 2011. The main aerosol sources recognised by Positive Matrix Factorization (PMF analysis of Streaker data are mineral dust and fresh sea salt (both mostly in the coarser fraction PM2.5–10, As-bearing sulphatic aerosol (PM0.1–2.5, metalliferous sodic particulate matter (PM interpreted as aged, industrially contaminated marine aerosol, and ZnCu-bearing aerosols. Whereas mineral dust arrivals are typically highly transient, peaking over a few hours, sulphatic intrusions build up and decline more slowly, and are accompanied by notable rises in ambient concentrations of metallic trace elements such as Pb, As, Zn, Sn and Cd. The magnitude of the loss in regional air quality due to the spread and persistence of pollution from mainland Asia is especially clear when cleansing oceanic air advects westward across Japan, removing the continental influence and reducing concentrations of the undesirable metalliferous pollutants by over 90%. Our new chemical database, especially the Streaker data, demonstrates the rapidly changing complexity of ambient air inhaled during these transboundary events, and implicates Chinese coal combustion as the main source of the anthropogenic aerosol component.

  9. Azo dye decolorization assisted by chemical and biogenic sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Prato-Garcia, Dorian [Laboratory for Research on Advanced Processes for Water Treatment, Unidad Académica Juriquilla, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, Querétaro 76230 (Mexico); Cervantes, Francisco J. [División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa de San José 2055, San Luis Potosí 78216 (Mexico); Buitrón, Germán, E-mail: gbuitronm@ii.unam.mx [Laboratory for Research on Advanced Processes for Water Treatment, Unidad Académica Juriquilla, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, Querétaro 76230 (Mexico)

    2013-04-15

    Highlights: ► Azo dyes were reduced efficiently by chemical and biogenic sulfide. ► Biogenic sulfide was more efficient than chemical sulfide. ► There was no competition between dyes and sulfate for reducing equivalents. ► Aromatic amines barely affected the sulfate-reducing process. -- Abstract: The effectiveness of chemical and biogenic sulfide in decolorizing three sulfonated azo dyes and the robustness of a sulfate-reducing process for simultaneous decolorization and sulfate removal were evaluated. The results demonstrated that decolorization of azo dyes assisted by chemical sulfide and anthraquinone-2,6-disulfonate (AQDS) was effective. In the absence of AQDS, biogenic sulfide was more efficient than chemical sulfide for decolorizing the azo dyes. The performance of sulfate-reducing bacteria in attached-growth sequencing batch reactors suggested the absence of competition between the studied azo dyes and the sulfate-reducing process for the reducing equivalents. Additionally, the presence of chemical reduction by-products had an almost negligible effect on the sulfate removal rate, which was nearly constant (94%) after azo dye injection.

  10. Size-dependent chemical ageing of oleic acid aerosol under dry and humidified conditions

    Science.gov (United States)

    Al-Kindi, Suad S.; Pope, Francis D.; Beddows, David C.; Bloss, William J.; Harrison, Roy M.

    2016-12-01

    A chemical reaction chamber system has been developed for the processing of oleic acid aerosol particles with ozone under two relative humidity conditions: dry and humidified to 65 %. The apparatus consists of an aerosol flow tube, in which the ozonolysis occurs, coupled to a scanning mobility particle sizer (SMPS) and an aerosol time-of-flight mass spectrometer (ATOFMS) which measure the evolving particle size and composition. Under both relative humidity conditions, ozonolysis results in a significant decrease in particle size and mass which is consistent with the formation of volatile products that partition from the particle to the gas phase. Mass spectra derived from the ATOFMS reveal the presence of the typically observed reaction products: azelaic acid, nonanal, oxononanoic acid and nonanoic acid, as well as a range of higher molecular weight products deriving from the reactions of reaction intermediates with oleic acid and its oxidation products. These include octanoic acid and 9- and 10-oxooctadecanoic acid, as well as products of considerably higher molecular weight. Quantitative evaluation of product yields with the ATOFMS shows a marked dependence upon both particle size association (from 0.3 to 2.1 µm diameter) and relative humidity. Under both relative humidity conditions, the percentage residual of oleic acid increases with increasing particle size and the main lower molecular weight products are nonanal and oxononanoic acid. Under dry conditions, the percentage of higher molecular weight products increases with increasing particle size due to the poorer internal mixing of the larger particles. Under humidified conditions, the percentage of unreacted oleic acid is greater, except in the smallest particle fraction, with little formation of high molecular weight products relative to the dry particles. It is postulated that water reacts with reactive intermediates, competing with the processes which produce high molecular weight products. Whilst the

  11. Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques

    Directory of Open Access Journals (Sweden)

    S. Decesari

    2014-04-01

    Full Text Available The use of co-located multiple spectroscopic techniques can provide detailed information on the atmospheric processes regulating aerosol chemical composition and mixing state. So far, field campaigns heavily equipped with aerosol mass spectrometers have been carried out mainly in large conurbations and in areas directly affected by their outflow, whereas lesser efforts have been dedicated to continental areas characterized by a less dense urbanization. We present here the results obtained in San Pietro Capofiume, which is located in a sparsely inhabited sector of the Po Valley, Italy. The experiment was carried out in summer 2009 in the framework of the EUCAARI project ("European Integrated Project on Aerosol, Cloud Climate Aerosol Interaction". For the first time in Europe, six state-of-the-art techniques were used in parallel: (1 on-line TSI aerosol time-of-flight mass spectrometer (ATOFMS, (2 on-line Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS, (3 soot particle aerosol mass spectrometer (SP-AMS, (4 on-line high resolution time-of-flight mass spectrometer-thermal desorption aerosol gas chromatograph (HR-ToFMS-TAG, (5 off-line twelve-hour resolution proton nuclear magnetic resonance (H-NMR spectroscopy, and (6 chemical ionization mass spectrometry (CIMS for the analysis of gas-phase precursors of secondary aerosol. Data from each aerosol spectroscopic method were analysed individually following ad-hoc tools (i.e. PMF for AMS, Art-2a for ATOFMS. The results obtained from each techniques are herein presented and compared. This allows us to clearly link the modifications in aerosol chemical composition to transitions in air mass origin and meteorological regimes. Under stagnant conditions, atmospheric stratification at night and early morning hours led to the accumulation of aerosols produced by anthropogenic sources distributed over the Po Valley plain. Such aerosols include primary components such as black

  12. Synthesis, microstructural characterization and optical properties of CuO nanorods and nanowires obtained by aerosol assisted CVD

    Energy Technology Data Exchange (ETDEWEB)

    Lugo-Ruelas, M. [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, Chihuahua, Chih. C.P. 31109 (Mexico); Universidad Autónoma de Chihuahua, Facultad de Ingeniería, Circuito No. 1, Nuevo Campus Universitario, Apdo. Postal 1552, Chihuahua, Chih. C.P. 31240 (Mexico); Amézaga-Madrid, P. [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, Chihuahua, Chih. C.P. 31109 (Mexico); Esquivel-Pereyra, O. [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, Chihuahua, Chih. C.P. 31109 (Mexico); Universidad Autónoma de Chihuahua, Facultad de Ingeniería, Circuito No. 1, Nuevo Campus Universitario, Apdo. Postal 1552, Chihuahua, Chih. C.P. 31240 (Mexico); Antúnez-Flores, W.; Pizá-Ruiz, P.; Ornelas-Gutiérrez, C. [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, Chihuahua, Chih. C.P. 31109 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No. 120, Chihuahua, Chih. C.P. 31109 (Mexico)

    2015-09-15

    Highlights: • Nanorods and nanowires of CuO were successfully synthesized by AACVD technique. • The carrier gas velocity was a determinant factor for the growth of nanorods or nanowires. • The increase of deposition time generates the reduction in the evenness and distribution density. • The crystalline phase of nanorods and nanowires was monoclinic tenorite. - Abstract: Copper oxide is a particularly interesting material because it presents photovoltaic, electrochemical and catalytic properties. Its unique properties are very important in the area of nanotechnology and may be an advantage because these nanomaterials can be applied in the design and manufacture of nanosensors, photocatalysis area, nanolasers switches and transistors. Nowadays one-dimensional nanostructures as nanorods, nanowires, etc., have generated a great importance and have received considerable attention and study due to their unique physical and chemical properties. In this work we report the synthesis, microstructural characterization and optical properties of CuO nanorods and nanowires grown by aerosol assisted chemical vapor deposition onto a CuO, ZnO and TiO{sub 2} thin film covered and bare borosilicate glass substrate. Concentration of the precursor solution and carrier gas flux were previously optimized and fixed at 0.1 mol dm{sup −3} and 5 L min{sup −1}, respectively. Other deposition parameters such as substrate temperature, as well the carrier gas velocity and deposition time were varied from 623 to 973 K, 0.88 to 1.77 m s{sup −1} and 11 to 16 min, respectively. Their influence on the morphology, microstructure and optical properties of the nanorods and nanowires were analyzed. The crystalline structure of the materials was characterized by grazing incidence X-ray diffraction; results indicate the presence of the tenorite phase. Surface morphology and microstructure were studied by field emission scanning electron microscopy, and high resolution transmission electron

  13. Chemical Characterization of the Aerosol During the CLAMS Experiment Using Aircraft and Ground Stations

    Science.gov (United States)

    Castanho, A. D.; Martins, J.; Artaxo, P.; Hobbs, P. V.; Remer, L.; Yamasoe, M.; Fattori, A.

    2002-05-01

    During the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) Experiment Nuclepore filters were collected in two ground stations and aboard the University of Wasghington's Convair 580 Reserarch Aircraft. The two ground stations were chosen in strategic positions to characterize the chemical composition, the mass concentration, black carbon (BC) content, and the absorption properties of the aerosol particles at the surface level. One of the stations was located at the Cheasapeake lighthouse (25 km from the coast) and the other one was located at the Wallops Island. Aerosol particles where collected in two stages, fine (d2.5um) and coarse mode (2.5aerosol in the atmospheric column in the CLAMS Experiment area. Some of the filters were also submitted to Scanning Electron Microscopy analysis. The particulate matter mass for all the samples were obtained gravimetrically. The concentration of black carbon in the fine filters was optically determined by a broadband reflectance technique. The spectral (from UV to near IR) reflectance in the fine and coarse mode filter were also obtained with a FieldSpec ASD spectrometer. Aerosol elemental characterization (Na through Pb) was obtained by the PIXE (Particle induced X ray emission) analyses of the nuclepore filters. The sources of the aerosol measured at the ground stations were estimated by principal component analyses mainly in the Wallops Island, where a longer time series was collected. One of the main urban components identified in the aerosol during the experiment was sulfate. Black carbon

  14. Microphysical and chemical characteristics of near-water aerosol over White and Kara Seas

    Science.gov (United States)

    Terpugova, S. A.; Polkin, V. V.; Panchenko, M. V.; Golobokova, L. P.; Kozlov, V. S.; Shmargunov, V. P.; Shevchenko, V. P.; Lisitzin, A. P.

    2009-04-01

    The results are presented of five-year-long (2003-2007) study of the spatial - temporal variability of the near-water aerosol in the water area of White and Kara Seas (55, 64, 71 and 80-th cruises of RV "Professor Shtockman"; 53 and 54-th cruises of RV "Akademik Mstislav Keldysh"). Measurements of aerosol microphysical characteristics were carried out by means of the automated mobile aerosol complex consisting of nephelometer, photoelectric counter and aethalometer. The aerosol disperse composition was studied with photoelectric counter in 256 size intervals from 0.4 to 10 m. About 1500 series of measurements were carried out in White Sea, and about 1400 series in Kara Sea. Chemical characteristics of aerosol were determined from samples collected on aerosol filters (92 samples were collected in White Sea and 48 in Kara Sea). The ion composition was determined under laboratory conditions. The H+, Na+, K+, Ca2+, Mg2+, NH4+, Cl-, NO3-, HCO3-, SO42- ions were under examination. Comparing aerosol characteristics of two seas, one can note that the mean values of the aerosol content parameters in Kara Sea are less than in White Sea. The ratio of the aerosol mass concentration are from 2 (Yamal Peninsula, northern part of Novaya Zemlya) to 9 times (Blagopoluchia Bay, Ob' Gulf). The differences in the concentration of black carbon vary from 3 (Yamal Peninsula) to 17 times (Blagopoluchia Bay). The differences in the aerosol number concentration NA are not so big. The values NA near Kara Gate, Yamal Peninsula and northern part of Novaya Zemlya are practically the same as in White Sea. The concentration NA at Ob' gulf is one order of magnitude less than in White sea. The obtained aerosol volume size distributions were approximated by the sums of two fractions, submicron and coarse, with lognormal size distributions. The mean volume size distribution of submicron fraction in White Sea is approximated by the distribution with the variance of the radius logarithm s=0.6 and modal

  15. Investigating the Chemical Pathways to PAH- and PANH-Based Aerosols in Titan's Atmospheric chemistry

    Science.gov (United States)

    Sciamma-O'Brien, Ella Marion; Contreras, Cesar; Ricketts, Claire Louise; Salama, Farid

    2011-01-01

    A complex organic chemistry between Titan's two main constituents, N2 and CH4, leads to the production of more complex molecules and subsequently to solid organic aerosols. These aerosols are at the origin of the haze layers giving Titan its characteristic orange color. In situ measurements by the Ion Neutral Mass Spectrometer (INMS) and Cassini Plasma Spectrometer (CAPS) instruments onboard Cassini have revealed the presence of large amounts of neutral, positively and negatively charged heavy molecules in the ionosphere of Titan. In particular, benzene (C6H6) and toluene (C6H5CH3), which are critical precursors of polycyclic aromatic hydrocarbon (PAH) compounds, have been detected, suggesting that PAHs might play a role in the production of Titan s aerosols. Moreover, results from numerical models as well as laboratory simulations of Titan s atmospheric chemistry are also suggesting chemical pathways that link the simple precursor molecules resulting from the first steps of the N2-CH4 chemistry (C2H2, C2H4, HCN ...) to benzene, and to PAHs and nitrogen-containing PAHs (or PANHs) as precursors to the production of solid aerosols.

  16. Chemical properties and morphology of Marine Aerosol in the Mediterranean atmosphere: a mesocosm study

    Science.gov (United States)

    D'Anna, Barbara; Sellegri, Karine; Charrière, Bruno; Sempéré, Richard; Mas, Sébastien; Marchand, Nicolas; George, Christian; Même, Aurèlie; R'mili, Badr; Delmont, Anne; Schwier, Allison; Rose, Clémence; Colomb, Aurèlie; Pey, Jorge; Langley Dewitt, Helen

    2014-05-01

    The Mediterranean Sea is a special marine environment characterized by low biological activity and high anthropogenic pressure. It is often difficult to discriminate the contribution of Primary Sea Salt Aerosol formed at the sea surface from background level of the aerosol. An alternative tool to study the sea-air exchanges in a controlled environment is provided by the mesocosms, which represent an important link between field studies and laboratory experiments. The sea-air transfer of particles and gases was investigated in relation to water chemical composition and biological activity during a mesocosm experiment within the SAM project (Sources of marine Aerosol in the Mediterranean) at the Oceanographic and Marine Station STARESO in Western Corsica (May 2013). Three 2 m mesocosms were filled with screened (treatments: one was left unchanged as control and two were enriched by addition of nitrates and phosphates respecting Redfield ratio (N:P = 16). The evolution of the three systems was followed for 20 days. The set of sensors in each mesocosm was allowed to monitor, at high frequency (every 10 min), the water temperature, conductivity, pH, incident light, fluorescence of chlorophyll a and dissolved oxygen concentration. The mesocosm seawaters were daily sampled for chemical (colored dissolved organic matter, particulate matter and related polar compounds, transparent polysaccharides and nutrients concentration) and biological (chlorophyll a, virus, phytoplankton and zooplankton) analyses. Both dissolved and gaseous VOCs were also analyzed. In addition, few liters of seawater from each mesocosm were daily and immediately collected and transferred to a bubble-bursting apparatus to simulate nascent sea spray aerosol. On-line chemical analysis of the sub-micrometer fraction was performed by a TOF-AMS (Aerodyne). Off-line analysis included TEM-EDX for morphology and size distribution studies and a hybrid quadrupole-orbitrap mass spectrometer (Thermo Fischer) for

  17. Long-term Chemical Characterization of Submicron Aerosol Particles in the Amazon Forest - ATTO Station

    Science.gov (United States)

    Carbone, S.; Brito, J.; Rizzo, L. V.; Holanda, B. A.; Cirino, G. G.; Saturno, J.; Krüger, M. L.; Pöhlker, C.; Ng, N. L.; Xu, L.; Andreae, M. O.; Artaxo, P.

    2015-12-01

    The study of the chemical composition of aerosol particles in the Amazon forest represents a step forward to understand the strong coupling between the atmosphere and the forest. For this reason submicron aerosol particles were investigated in the Amazon forest, where biogenic and anthropogenic aerosol particles coexist at the different seasons (wet/dry). The measurements were performed at the ATTO station, which is located about 150 km northeast of Manaus. At ATTO station the Aerosol chemical speciation monitor (ACSM, Aerodyne) and the Multiangle absorption photometer (MAAP, Thermo 5012) have been operated continuously from March 2014 to July 2015. In this study, long-term measurements (near-real-time, ~30 minutes) of PM1 chemical composition were investigated for the first time in this environment.The wet season presented lower concentrations than the dry season (~5 times). In terms of chemical composition, both seasons were dominated by organics (75 and 63%) followed by sulfate (11 and 13%). Nitrate presented different ratio values between the mass-to-charges 30 to 46 (main nitrate fragments) suggesting the presence of nitrate as inorganic and organic nitrate during both seasons. The results indicated that about 75% of the nitrate signal was from organic nitrate during the dry season. In addition, several episodes with elevated amount of chloride, likely in the form of sea-salt from the Atlantic Ocean, were observed during the wet season. During those episodes, chloride comprised up to 7% of the PM1. During the dry season, chloride was also observed; however, with different volatility, which suggested that Chloride was present in different form and source. Moreover, the constant presence of sulfate and BC during the wet season might be related to biomass burning emissions from Africa. BC concentration was 2.5 times higher during the dry season. Further characterization of the organic fraction was accomplished with the positive matrix factorization (PMF), which

  18. Silicon nanowire photodetectors made by metal-assisted chemical etching

    Science.gov (United States)

    Xu, Ying; Ni, Chuan; Sarangan, Andrew

    2016-09-01

    Silicon nanowires have unique optical effects, and have potential applications in photodetectors. They can exhibit simple optical effects such as anti-reflection, but can also produce quantum confined effects. In this work, we have fabricated silicon photodetectors, and then post-processed them by etching nanowires on the incident surface. These nanowires were produced by a wet-chemical etching process known as the metal-assisted-chemical etching, abbreviated as MACE. N-type silicon substrates were doped by thermal diffusion from a solid ceramic source, followed by etching, patterning and contact metallization. The detectors were first tested for functionality and optical performance. The nanowires were then made by depositing an ultra-thin film of gold below its percolation thickness to produce an interconnected porous film. This was then used as a template to etch high aspect ratio nanowires into the face of the detectors with a HF:H2O2 mixture.

  19. Chemical insights, explicit chemistry and yields of secondary organic aerosol from methylglyoxal and glyoxal

    Science.gov (United States)

    Lim, Y. B.; Tan, Y.; Turpin, B. J.

    2013-02-01

    Atmospherically abundant, volatile water soluble organic compounds formed through gas phase chemistry (e.g., glyoxal (C2), methylglyoxal (C3) and acetic acid) have great potential to form secondary organic aerosol (SOA) via aqueous chemistry in clouds, fogs and wet aerosols. This paper (1) provides chemical insights into aqueous-phase OH radical-initiated reactions leading to SOA formation from methylglyoxal and (2) uses this and a previously published glyoxal mechanism (Lim et al., 2010) to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012). This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010), and is used to simulate the profiles of products and to estimate SOA yields. At cloud relevant concentrations (∼ 10-6-∼ 10-3 M; Munger et al., 1995) of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass) are ∼ 120% for glyoxal and ∼ 80% for methylglyoxal. Oligomerization of unreacted aldehydes during droplet evaporation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (∼ 10 M), the major products are oligomers formed via organic radical-radical reactions, and simulated SOA yields (by mass) are ∼ 90% for both glyoxal and methylglyoxal.

  20. Chemical and Physical Properties of Bulk Aerosols within Four Sectors Observed during TRACE-P

    Science.gov (United States)

    Jordan, C. E.; Anderson, B. E.; Talbot, R. W.; Dibb, J. E.; Fuelberg, E.; Hudgins, C. H.; Kiley, C. M.; Russo, R.; Scheuer, E.; Seid, G.

    2003-01-01

    Chemical and physical aerosol data collected on the DC-8 during TRACE-P were grouped into four sectors based on back trajectories. The four sectors represent long-range transport from the west (WSW), regional circulation over the western Pacific and Southeast Asia (SE Asia), polluted transport from Northern Asia with substantial sea salt at low altitudes (NNW) and a substantial amount of dust (Channel). WSW has generally low mixing ratios at both middle and high altitudes, with the bulk of the aerosol mass due to non-sea-salt water-soluble inorganic species. Low altitude SE Asia also has low mean mixing ratios in general, with the majority of the aerosol mass comprised of non-sea-salts, however, soot is also relatively important m this region. "w had the highest mean sea salt mixing ratios, with the aerosol mass at low altitudes (a km) evenly divided between sea salts, mm-sea-salts, and dust. The highest mean mixing ratios of water-soluble ions and soot were observed at the lowest altitudes (a km) in the Channel sector. The bulk of the aerosol mass exported from Asia emanates h m Channel at both low and midaltitudes, due to the prevalence of dust compared to other sectors. Number densities show enhanced fine particles for Channel and NNW, while their volume distributions are enhanced due to sea salt and dust Low-altitude Channel exhibits the highest condensation nuclei ((34) number densities along with enhanced scattering coefficients, compared to the other sectors. At midaltitudes (2-7 km), low mean CN number densities coupled with a high proportion of nonvolatile particles (265%) observed in polluted sectors (Channel and NNW) are attributed to wet scavenging which removes hygroscopic CN particles. Low single scatter albedo m SE Asia reflects enhanced soot

  1. Chemical composition, sources, and processes of urban aerosols during summertime in Northwest China: insights from High Resolution Aerosol Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    J. Xu

    2014-06-01

    Full Text Available An aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS was deployed along with a Scanning Mobility Particle Sizer (SMPS and a Multi Angle Absorption Photometers (MAAP to measure the temporal variations of the mass loading, chemical composition, and size distribution of sub-micrometer particulate matter (PM1 in Lanzhou, northwest China, during 12 July–7 August 2012. The average PM1 mass concentration including non-refractory PM1 (NR-PM1 measured by HR-ToF-AMS and black carbon (BC measured by MAAP during this study was 24.5 μg m−3 (ranging from 0.86 to 105μg m−3, with a mean composition consisting of 47% organics, 16% sulfate, 12% BC, 11% ammonium, 10% nitrate, and 4% chloride. The organics was consisted of 70% carbon, 21% oxygen, 8% hydrogen, and 1% nitrogen, with the average oxygen-to-carbon ratio (O / C of 0.33 and organic mass-to-carbon ratio (OM / OC of 1.58. Positive matrix factorization (PMF of the high-resolution mass spectra of organic aerosols (OA identified four distinct factors which represent, respectively, two primary OA (POA emission sources (traffic and food cooking and two secondary OA (SOA types – a fresher, semi-volatile oxygenated OA (SV-OOA and a more aged, low-volatility oxygenated OA (LV-OOA. Traffic-related hydrocarbon-like OA (HOA and BC displayed distinct diurnal patterns both with peak at ~07:00–11:00 (BJT: UTC +8 corresponding to the morning rush hours, while cooking OA (COA peaked during three meal periods. The diurnal profiles of sulfate and LV-OOA displayed a broad peak between ∼07:00–15:00, while those of nitrate, ammonium, and SV-OOA showed a narrower peak at ~08:00–13:00. The later morning and early afternoon peak in the diurnal profiles of secondary aerosol species was likely caused by mixing down of pollutants aloft, which were likely produced in the residual layer decoupled from the boundary layer during night time. The mass spectrum of SV-OOA also showed similarity

  2. His6 tag-assisted chemical protein synthesis

    Science.gov (United States)

    Bang, Duhee; Kent, Stephen B. H.

    2005-04-01

    To make more practical the total chemical synthesis of proteins by the ligation of unprotected peptide building blocks, we have developed a method to facilitate the isolation and handling of intermediate products. The synthetic technique makes use of a His6 tag at the C terminus of the target polypeptide chain, introduced during the synthesis of the C-terminal peptide segment building block. The presence of a His6 tag enables the isolation of peptide or protein products directly from ligation reaction mixtures by Ni-NTA affinity column purification. This simple approach enables facile buffer exchange to alternate reaction conditions and is compatible with direct analytical control by protein MS of the multiple ligation steps involved in protein synthesis. We used syntheses of crambin and a modular tetratricopeptide repeat protein of 17 kDa as models to examine the utility of this affinity purification approach. The results show that His6 tag-assisted chemical protein synthesis is a useful method that substantially reduces handling losses and provides for rapid chemical protein syntheses. affinity purification | native chemical ligation

  3. Chemical composition and size distribution of secondary organic aerosol formed from the photooxidation of isoprene

    Institute of Scientific and Technical Information of China (English)

    LIU Xianyun; ZHANG Weijun; WANG Zhenya; ZHAO Weixiong; TAO Ling; YANG Xibin

    2009-01-01

    Photooxidation of isoprene leads to the formation of secondary organic aerosol (SOA).In this study,the chemical composition of SOA formed from OH-initiated photooxidation of isoprene has been investigated with gas chromatography/mass spectrometry (GC/MS) and a home-made aerosol time-of-flight mass spectrometer (ATOFMS).Sampling particles generated in a home-made smog chamber.The size distribution of SOA particles was detected by a TSI 3321 aerodynamic particle size spectrometer in real time.Results showed that SOA created by isoprene photooxidation was predominantly in the form of fine particles,which have diameters less than 2.5 μm.The obtained mass spectra of individual particles show that products of the OH-initiated oxidation of isoprene contain methyl vinyl ketone,methacrolein,formaldehyde,and some other hydroxycarbonyls.The possible reaction mechanisms leading to these products were also discussed.

  4. Submicron aerosol source apportionment of wintertime pollution in Paris, France by Double Positive Matrix Factorization (PMF2 using Aerosol Chemical Speciation Monitor (ACSM and multi-wavelength Aethalometer

    Directory of Open Access Journals (Sweden)

    J.-E. Petit

    2014-06-01

    Full Text Available Online non-refractory submicron Aerosol Mass Spectrometer (AMS measurements in urban areas have successfully allowed the apportionment of specific sources and/or physical and chemical properties of the organic fraction. However, in order to be fully representative of PM pollution, a comprehensive source apportionment analysis is needed by taking into account all major components of submicron aerosols, creating strengthened bonds between the organic components and pollution sources. We present here a novel two-step methodology to perform such an analysis, by taking advantage of high time resolution of monitoring instruments: the Aerosol Chemical Speciation Monitor (ACSM and the multi-wavelength absorption measurements (Aethalometer AE31 in Paris, France. As a first step, organic aerosols (OA were deconvoluted to hydrocarbon-like OA (HOA, Biomass Burning OA (BBOA and Oxygenated OA (OOA with Positive Matrix Factorization, and black carbon was deconvolved into its wood burning and fossil fuel combustion fractions. A second PMF analysis was then carried out with organic factors, BC fractions and inorganic species (nitrate, sulfate, ammonium, chloride, leading to a~four-factor solution allowing real-time characterization of the major sources of PM1. Outputs of this PMF2 include two dominant combustion sources (wood burning and traffic as well as semi-volatile and low-volatile secondary aerosols. While HOA is found to be emitted by both wood burning and traffic, the latter sources occurred to significantly contribute also to OOA.

  5. Aerosol Physical and Chemical Properties Before and After the Manaus Plume in the GoAmazon2014 Experiment

    Science.gov (United States)

    Artaxo, P.; Barbosa, H. M.; Ferreira De Brito, J.; Wurm, F.; Holanda, B. A.; Carbone, S.; Arana, A.; Cirino, G. G.; Souza, R. A. F. D.; Rizzo, L. V.; Martin, S. T.; Andreae, M. O.; Holben, B. N.; Schafer, J.

    2014-12-01

    As part of the GoAmazon2014 experiment, several aerosol and trace gas monitoring stations are being operated for at least one year before and after the Manaus plume. Three sites are being operated in pristine conditions, with atmospheric properties under natural biogenic conditions. These three sites called T0 are: ATTO (Amazon Tall Tower Observatory), ZF2 ecological research site and a third site called EMBRAPA. After the air masses are exposed to the Manaus plume, one site (called T2) is being operated right on the opposite side of the Negro River under the direct influence of the Manaus plume at 5 Km downwind of Manaus. Finally, at about 150 Km downwind of Manaus is the T3 Manacapuru site. Aerosol chemical composition is being analyzed using filters for fine (PM2.5) and coarse mode aerosol as well as three Aerodyne ACSM (Aerosol Chemical Speciation Monitors) instruments. Aerosol absorption is being studied with several aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using nephelometers. Aerosol size distribution is determined using scanning mobility particle sizers. The aerosol column is measures using AERONET sunphotometers before and after the Manaus plume, as well as several Lidar systems. The three sites before the Manaus plume show remarkable similar variability in aerosol concentrations and optical properties. This pattern is very different at the T2 site, with large aerosol concentrations enhancing aerosol absorption and scattering significantly. The aerosol is very oxidized before being exposed to the Manaus plume, and this pattern changes significantly for T2 and T3 sites, with a much higher presence of less oxidized aerosol. Typical ozone concentrations at mid-day before Manaus plume is a low 10-12 ppb, value that changes to 50-70 ppb for air masses suffering the influence of Manaus plume. A detailed comparison of aerosol characteristics and composition for the several

  6. Introductory lecture: atmospheric organic aerosols: insights from the combination of measurements and chemical transport models.

    Science.gov (United States)

    Pandis, Spyros N; Donahue, Neil M; Murphy, Benjamin N; Riipinen, Ilona; Fountoukis, Christos; Karnezi, Eleni; Patoulias, David; Skyllakou, Ksakousti

    2013-01-01

    The formation, atmospheric evolution, properties, and removal of organic particulate matter remain some of the least understood aspects of atmospheric chemistry despite the importance of organic aerosol (OA) for both human health and climate change. Here, we summarize our recent efforts to deal with the chemical complexity of the tens of thousands of organic compounds in the atmosphere using the volatility-oxygen content framework (often called the 2D-Volatility Basis Set, 2D-VBS). Our current ability to measure the ambient OA concentration as a function of its volatility and oxygen to carbon (O:C) ratio is evaluated. The combination of a thermodenuder, isothermal dilution and Aerosol Mass Spectrometry (AMS) together with a mathematical aerosol dynamics model is a promising approach. The development of computational modules based on the 2D-VBS that can be used in chemical transport models (CTMs) is described. Approaches of different complexity are tested against ambient observations, showing the challenge of simulating the complex chemical evolution of atmospheric OA. The results of the simplest approach describing the net change due to functionalization and fragmentation are quite encouraging, reproducing both the observed OA levels and O : C in a variety of conditions. The same CTM coupled with source-apportionment algorithms can be used to gain insights into the travel distances and age of atmospheric OA. We estimate that the average age of OA near the ground in continental locations is 1-2 days and most of it was emitted (either as precursor vapors or particles) hundreds of kilometers away. Condensation of organic vapors on fresh particles is critical for the growth of these new particles to larger sizes and eventually to cloud condensation nuclei (CCN) sizes. The semivolatile organics currently simulated by CTMs are too volatile to condense on these tiny particles with high curvature. We show that chemical aging reactions converting these semivolatile

  7. Eddy covariance measurements with high-resolution time-of-flight aerosol mass spectrometry: a new approach to chemically resolved aerosol fluxes

    Directory of Open Access Journals (Sweden)

    D. K. Farmer

    2011-06-01

    Full Text Available Although laboratory studies show that biogenic volatile organic compounds (VOCs yield substantial secondary organic aerosol (SOA, production of biogenic SOA as indicated by upward fluxes has not been conclusively observed over forests. Further, while aerosols are known to deposit to surfaces, few techniques exist to provide chemically-resolved particle deposition fluxes. To better constrain aerosol sources and sinks, we have developed a new technique to directly measure fluxes of chemically-resolved submicron aerosols using the high-resolution time-of-flight aerosol mass spectrometer (HR-AMS in a new, fast eddy covariance mode. This approach takes advantage of the instrument's ability to quantitatively identify both organic and inorganic components, including ammonium, sulphate and nitrate, at a temporal resolution of several Hz. The new approach has been successfully deployed over a temperate ponderosa pine plantation in California during the BEARPEX-2007 campaign, providing both total and chemically resolved non-refractory (NR PM1 fluxes. Average deposition velocities for total NR-PM1 aerosol at noon were 2.05 ± 0.04 mm s−1. Using a high resolution measurement of the NH2+ and NH3+ fragments, we demonstrate the first eddy covariance flux measurements of particulate ammonium, which show a noon-time deposition velocity of 1.9 ± 0.7 mm s−1 and are dominated by deposition of ammonium sulphate.

  8. Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

    Directory of Open Access Journals (Sweden)

    T. S. Bates

    2006-01-01

    Full Text Available The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001. Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO during INDOEX, the Northwest Pacific Ocean (NWP during ACE-Asia, and the Northwest Atlantic Ocean (NWA during ICARTT, incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART. Measurements of burdens, extinction optical depth (AOD, and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity are used as input parameters to two radiative transfer models (GFDL and University of Michigan to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative

  9. Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

    Science.gov (United States)

    Bates, T. S.; Anderson, T. L.; Baynard, T.; Bond, T.; Boucher, O.; Carmichael, G.; Clarke, A.; Erlick, C.; Guo, H.; Horowitz, L.; Howell, S.; Kulkarni, S.; Maring, H.; McComiskey, A.; Middlebrook, A.; Noone, K.; O'Dowd, C. D.; Ogren, J.; Penner, J.; Quinn, P. K.; Ravishankara, A. R.; Savoie, D. L.; Schwartz, S. E.; Shinozuka, Y.; Tang, Y.; Weber, R. J.; Wu, Y.

    2006-05-01

    The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE - change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer

  10. Influences of relative humidity and particle chemical composition on aerosol scattering properties during the 2006 PRD campaign

    Science.gov (United States)

    Liu, Xingang; Cheng, Yafang; Zhang, Yuanhang; Jung, Jinsang; Sugimoto, Nobuo; Chang, Shih-Yu; Kim, Young J.; Fan, Shaojia; Zeng, Limin

    In situ measurements of the physical, chemical, and optical properties of aerosols were carried out in Guangzhou city, China, from 1 to 31 July 2006 during the Pearl River Delta (PRD) Campaign. The light extinction coefficient of the ambient atmosphere, the aerosol scattering coefficient under dry conditions, the aerosol absorption coefficient under ambient conditions, NO 2 concentration, and relative humidity (RH) were measured by transmissionmeter, an integrating nephelometer, a multi-angle absorption photometer (MAAP), a NO X analyzer, and an automatic meteorological station, respectively. Meanwhile, the molecular scattering coefficient was calculated by the Rayleigh scattering function using the US Standard Atmosphere. A method to calculate the aerosol hygroscopic growth factor f(RH), defined as the ratio of the aerosol scattering coefficient under a wet condition to that under a dry condition (40% RH), is proposed based on these optical parameters. The mean and standard deviation aerosol hygroscopic growth factors at 80% RH ( f(RH)=80%) in Ganzhou were 2.04±0.28, 2.29±0.28, and 2.68±0.59 for urban aerosols, mixed aerosols, and marine aerosols, respectively, with the air mass classification being based on the air mass source region. The relationship between f(RH) and RH is fitted by empirical equations and the fitting parameters are calculated. The relationships between f(RH)=80% and total carbon mass fraction (TCF) in PM 2.5, the water-soluble mass fraction (WSF) in PM 10, and the sea-salt aerosol mass fraction (SSF) in PM 10 reveal that the hygroscopic properties of the observed aerosol have a good positive correlation with the WSF and SSF, but have a negative correlation with the TCF.

  11. Nanoscale wear as a stress-assisted chemical reaction.

    Science.gov (United States)

    Jacobs, Tevis D B; Carpick, Robert W

    2013-02-01

    Wear of sliding contacts leads to energy dissipation and device failure, resulting in massive economic and environmental costs. Typically, wear phenomena are described empirically, because physical and chemical interactions at sliding interfaces are not fully understood at any length scale. Fundamental insights from individual nanoscale contacts are crucial for understanding wear at larger length scales, and to enable reliable nanoscale devices, manufacturing and microscopy. Observable nanoscale wear mechanisms include fracture and plastic deformation, but recent experiments and models propose another mechanism: wear via atom-by-atom removal ('atomic attrition'), which can be modelled using stress-assisted chemical reaction kinetics. Experimental evidence for this has so far been inferential. Here, we quantitatively measure the wear of silicon--a material relevant to small-scale devices--using in situ transmission electron microscopy. We resolve worn volumes as small as 25 ± 5 nm(3), a factor of 10(3) lower than is achievable using alternative techniques. Wear of silicon against diamond is consistent with atomic attrition, and inconsistent with fracture or plastic deformation, as shown using direct imaging. The rate of atom removal depends exponentially on stress in the contact, as predicted by chemical rate kinetics. Measured activation parameters are consistent with an atom-by-atom process. These results, by direct observation, establish atomic attrition as the primary wear mechanism of silicon in vacuum at low loads.

  12. Variations of the aerosol concentration and chemical composition over the arid steppe zone of Southern Russia in summer

    Science.gov (United States)

    Artamonova, M. S.; Gubanova, D. P.; Iordanskii, M. A.; Lebedev, V. A.; Maksimenkov, L. O.; Minashkin, V. M.; Obvintsev, Y. I.; Chketiani, O. G.

    2016-12-01

    Variations in the surface aerosol over the arid steppe zone of Southern Russia have been measured. The parameters of atmospheric aerosol (mass concentration, both dispersed and elemental compositions) and meteorological parameters were measured in Tsimlaynsk raion (Rostov oblast). The chemical composition of aerosol particles in the atmospheric surface layer has been determined, and the coefficients of enrichment of elements with respect to clarkes in the Earth's crust have been calculated. It is shown that, in summer, arid aerosols are transported from both alkaline and sandy soils of Kalmykia to the air basin over the observation zone. Aerosol particles in the surface air layer over this region have been found to contain the products of combustion of oil, coal, and ethylized fuel. These combustion products make a small contribution to the total mass concentration of atmospheric aerosol; however, they are most hazardous to the health of people because of their sizes and heavy-metal contents. A high concentration of submicron sulfur-containing aerosol particles of chemocondensation nature has been recorded. Sources of aerosol of both natural and anthropogenic origins in southern Russia are discussed.

  13. Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

    Directory of Open Access Journals (Sweden)

    M. Kajino

    2012-12-01

    Full Text Available A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2, was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS and achieved a completely dynamic (non-equilibrium solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super-μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK, soot-free particles in the accumulation mode (ACM, soot aggregates (AGR, and particles in the coarse mode (COR. The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation (Δx = 60 km was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM1/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non–sea-salt SO42− mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO42− was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO3 was mixed with sea salt at Hedo, whereas 53.7% of the NO3 was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean accounts for the difference in the NO3 mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol

  14. Chemical and microphysical properties of the aerosol during foggy and nonfoggy episodes: a relationship between organic and inorganic content of the aerosol

    Directory of Open Access Journals (Sweden)

    D. S. Kaul

    2012-06-01

    Full Text Available An extensive field measurement during winter was carried out at a site located in the Indo-Gangetic Plain (IGP which gets heavily influenced by the fog during winter almost every year. The chemical and microphysical properties of the aerosols during foggy and nonfoggy episodes and chemical composition of the fogwater are presented. Positive matrix factorization (PMF as a tool for the source apportionment was employed to understand the sources of pollution. Four major sources viz. biomass burning, refractory, secondary and mineral dust were identified. Aerosols properties during foggy episodes were heavily influenced by almost all the sources and they caused considerable loading of almost all the organic and inorganic species during the period. The biomass generated aerosols were removed from the atmosphere by scavenging during foggy episodes. The wet removal of almost all the species by the fog droplets was observed. The K+, water soluble organic carbon (WSOC, water soluble inorganic carbon (WSIC and NO3- were most heavily scavenged among the species and their concentrations consequently became lower than the nonfoggy episode concentrations. The production of secondary inorganic aerosol, mainly sulfate and ammonium, during foggy episodes was considerably higher than nitrate which was rather heavily scavenged and removed by the fog droplets. The fogwater analysis showed that dissolved inorganic species play a vital role in processing of organic carbon such as the formation of organo-sulfate and organo-nitrate inside the fog droplets. The formation of organo-sulfate and organo-nitrate in aerosol and the influence of acidity on the secondary organic aerosol (SOA formation were rather found to be negligible. The study average inorganic component of the aerosol was considerably higher than the carbonaceous component during both foggy and nonfoggy episode. The secondary production of the aerosol changed the

  15. Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

    Directory of Open Access Journals (Sweden)

    Y.-N. Lee

    2013-10-01

    Full Text Available The chemical composition of aerosol particles (Dp ≤ 1.5 μm was measured over the southeast Pacific ocean during the VOCALS-REx experiment between 16~October and 15 November 2008 using the US DOE G-1 aircraft. The objective of these flights was to gain an understanding of the sources and evolution of these aerosols, and how they interacted with the marine stratus cloud layer that prevails in this region of the globe. Our measurements showed that the marine boundary layer (MBL aerosol mass was dominated by non-sea-salt SO42−, followed by Na+, Cl−, Org, NH4+, and NO3−, in decreasing order of importance; CH3SO3−1 (MSA, Ca2+, and K+ rarely exceeded their limits of detection of ~0.05 and ~0.15 μg m−3 for anions and cations, respectively. The aerosols were strongly acidic as the NH4+ to SO42− equivalence ratio was typically − deficits caused by both HNO3 and H2SO4, and were externally mixed with SO42− particles as the AMS detected no NO3− whilst uptake of HNO3 occurred only on SSA particles. The SSA loading as a function of wind speed agreed with that calculated from published relationships, and contributed only a small fraction of the total accumulation mode particle number. Vertical distribution of MBL SSA particles (Dp ≤ ~1.5 μm was uniform, suggesting a very limited dilution from entrainment of free tropospheric (FT air. It was inferred that because all of the aerosol species (except SSA exhibited a strong land-to-sea gradient, they were of continental origin. Comparison of relative changes in median values using LOWESS fits as proxies suggests that (1 an oceanic source of NH3 is present between 72° W and 76° W, and (2 additional organic aerosols from biomass burns or biogenic precursors were emitted from coastal regions south of 31° S, with possible cloud processing, and (3 FT contributions to MBL gas and aerosols were negligible. Positive Matrix Factorization analysis of organic aerosol mass spectra obtained with

  16. Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

    Directory of Open Access Journals (Sweden)

    T. S. Bates

    2006-01-01

    Full Text Available The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001. Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO during INDOEX, the Northwest Pacific Ocean (NWP during ACE-Asia, and the Northwest Atlantic Ocean (NWA during ICARTT, incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART. Measurements of burdens, extinction optical depth (AOD, and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity are used as input parameters to two radiative transfer models (GFDL and University of Michigan to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative

  17. Chemically-resolved aerosol volatility measurements from two megacity field studies

    Directory of Open Access Journals (Sweden)

    J. A. Huffman

    2009-09-01

    Full Text Available The volatilities of different chemical species in ambient aerosols are important but remain poorly characterized. The coupling of a recently developed rapid temperature-stepping thermodenuder (TD, operated in the range 54–230°C with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS during field studies in two polluted megacities has enabled the first direct characterization of chemically-resolved urban particle volatility. Measurements in Riverside, CA and Mexico City are generally consistent and show ambient nitrate as having the highest volatility of any AMS standard aerosol species while sulfate showed the lowest volatility. Total organic aerosol (OA showed volatility intermediate between nitrate and sulfate, with an evaporation rate of 0.6%·K−1 near ambient temperature, although OA dominates the residual species at the highest temperatures. Different types of OA were characterized with marker ions, diurnal cycles, and positive matrix factorization (PMF and show significant differences in volatility. Reduced hydrocarbon-like OA (HOA, a surrogate for primary OA, POA, oxygenated OA (OOA, a surrogate for secondary OA, SOA, and biomass-burning OA (BBOA separated with PMF were all determined to be semi-volatile. The most aged OOA-1 and its dominant ion, CO2+, consistently exhibited the lowest volatility, with HOA, BBOA, and associated ions for each among the highest. The similar or higher volatility of HOA/POA compared to OOA/SOA contradicts the current representations of OA volatility in most atmospheric models and has important implications for aerosol growth and lifetime. A new technique using the AMS background signal was demonstrated to quantify the fraction of species up to four orders-of-magnitude less volatile than those detectable in the MS mode, which for OA represent ~5% of the non-refractory (NR OA signal. Our results strongly imply that all OA types should be considered

  18. Influence of Aerosol Chemical Composition on Heterogeneous Ice Formation under Mid-Upper Troposphere Conditions

    Science.gov (United States)

    Kanji, Z. A.; Niemand, M.; Saathoff, H.; Möhler, O.; Chou, C.; Abbatt, J.; Stetzer, O.

    2011-12-01

    Aerosols are involved in cooling/warming the atmosphere directly via interaction with incoming solar radiation (aerosol direct effect), or via their ability to act as cloud condensation or ice nuclei (IN) and thus play a role in cloud formation (indirect effect). In particular, the physical properties of aerosols such as size and solubility and chemical composition can influence their behavior and fate in the atmosphere. Ice nucleation taking place via IN is termed as heterogeneous ice nucleation and can take place with via deposition (ice forming on IN directly from the vapor phase), condensation/immersion (freezing via formation of the liquid phase on IN) or condensation (IN colliding with supercooled liquid drops). This presentation shows how the chemical composition and surface area of various tropospherically relevant aerosols influence conditions of temperature (T) and relative humidity (RH) required for heterogeneous ice formation conditions in the mid-upper troposphere regime (253 - 220K)? Motivation for this comes first from, the importance of being able to predict ice formation accurately so as to understand the hydrological cycle since the ice is the primary initiator of precipitation forming clouds. Second, the tropospheric budget of water vapour, an especially active greenhouse gas is strongly influenced by ice nucleation and growth. Third, ice surfaces in the atmosphere act as heterogeneous surfaces for chemical reactions of trace gases (e.g., SO2, O3, NOx and therefore being able to accurately estimate ice formation rates and quantify ice surface concentrations will allow a more accurate calculation of trace gas budgets in the troposphere. Ice nucleation measurements were conducted using a self-developed continuous flow diffusion chamber and static chamber. A number of tropospherically relevant particulates with naturally-varying and laboratory-modified surface chemistry/structure were investigated for their ice formation efficiency based on highest

  19. How much information do extinction and backscattering measurements contain about the chemical composition of atmospheric aerosol?

    Science.gov (United States)

    Kahnert, Michael; Andersson, Emma

    2017-03-01

    We theoretically and numerically investigate the problem of assimilating multiwavelength lidar observations of extinction and backscattering coefficients of aerosols into a chemical transport model. More specifically, we consider the inverse problem of determining the chemical composition of aerosols from these observations. The main questions are how much information the observations contain to determine the particles' chemical composition, and how one can optimize a chemical data assimilation system to make maximum use of the available information. We first quantify the information content of the measurements by computing the singular values of the scaled observation operator. From the singular values we can compute the number of signal degrees of freedom, Ns, and the reduction in Shannon entropy, H. As expected, the information content as expressed by either Ns or H grows as one increases the number of observational parameters and/or wavelengths. However, the information content is strongly sensitive to the observation error. The larger the observation error variance, the lower the growth rate of Ns or H with increasing number of observations. The right singular vectors of the scaled observation operator can be employed to transform the model variables into a new basis in which the components of the state vector can be partitioned into signal-related and noise-related components. We incorporate these results in a chemical data assimilation algorithm by introducing weak constraints that restrict the assimilation algorithm to acting on the signal-related model variables only. This ensures that the information contained in the measurements is fully exploited, but not overused. Numerical tests show that the constrained data assimilation algorithm provides a solution to the inverse problem that is considerably less noisy than the corresponding unconstrained algorithm. This suggests that the restriction of the algorithm to the signal-related model variables suppresses

  20. Characterization of aerosol optical properties, chemical composition and mixing states in the winter season in Shanghai, China

    Institute of Scientific and Technical Information of China (English)

    Yong Tang; Yuanlong Huang; Ling Li; Hong Chen; Jianmin Chen; Xin Yang; Song Gao

    2014-01-01

    Physical and chemical properdes of ambient aerosols at the single particle level were studied in Shanghai from December 22 to 28,2009.A Cavity-Ring-Down Aerosol Extinction Spectrometer (CRD-AES) and a nephelometer were deployed to measure aerosol light extinction and scattering properties,respectively.An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS)was used to detect single particle sizes and chemical composition.Seven particle types were detected.Air parcels arrived at the sampling site from the vicinity of Shanghai until mid-day of December 25,when they started to originate from North China.The aerosol extinction,scattering,and absorption coefficients all dropped sharply when this cold,clean air arrived.Aerosol particles changed from a highly aged type before this meteorological shift to a relatively fresh type afterwards.The aerosol optical properties were dependent on the wind direction.Aerosols with high extinction coefficient and scattering Angstr(o)m exponent (SAE) were observed when the wind blew from the west and northwest,indicating that they were predominantly fine particles.Nitrate and ammonium correlated most strongly with the change in aerosol optical properties.In the elemental carbon/organic carbon (ECOC) particle type,the diurnal trends of single scattering albedo (SSA) and elemental carbon (EC) signal intensity had a negative correlation.We also found a negative correlation (r =-0.87) between high mass-OC particle number fraction and the SSA in a relatively clean period,suggesting that particulate aromatic components might play an important role in light absorption in urban areas.

  1. Flight-based chemical characterization of biomass burning aerosols within two prescribed burn smoke plumes

    Directory of Open Access Journals (Sweden)

    K. A. Pratt

    2011-12-01

    Full Text Available Biomass burning represents a major global source of aerosols impacting direct radiative forcing and cloud properties. Thus, the goal of a number of current studies involves developing a better understanding of how the chemical composition and mixing state of biomass burning aerosols evolve during atmospheric aging processes. During the Ice in Clouds Experiment-Layer Clouds (ICE-L in the fall of 2007, smoke plumes from two small Wyoming Bureau of Land Management prescribed burns were measured by on-line aerosol instrumentation aboard a C-130 aircraft, providing a detailed chemical characterization of the particles. After ~2–4 min of aging, submicron smoke particles, produced primarily from sagebrush combustion, consisted predominantly of organics by mass, but were comprised primarily of internal mixtures of organic carbon, elemental carbon, potassium chloride, and potassium sulfate. Significantly, the fresh biomass burning particles contained minor mass fractions of nitrate and sulfate, suggesting that hygroscopic material is incorporated very near or at the point of emission. The mass fractions of ammonium, sulfate, and nitrate increased with aging up to ~81–88 min and resulted in acidic particles. Decreasing black carbon mass concentrations occurred due to dilution of the plume. Increases in the fraction of oxygenated organic carbon and the presence of dicarboxylic acids, in particular, were observed with aging. Cloud condensation nuclei measurements suggested all particles >100 nm were active at 0.5% water supersaturation in the smoke plumes, confirming the relatively high hygroscopicity of the freshly emitted particles. For immersion/condensation freezing, ice nuclei measurements at −32 °C suggested activation of ~0.03–0.07% of the particles with diameters greater than 500 nm.

  2. Flight-based chemical characterization of biomass burning aerosols within two prescribed burn smoke plumes

    Directory of Open Access Journals (Sweden)

    K. A. Pratt

    2011-06-01

    Full Text Available Biomass burning represents a major global source of aerosols impacting direct radiative forcing and cloud properties. Thus, the goal of a number of current studies involves developing a better understanding of how the chemical composition and mixing state of biomass burning aerosols evolve during atmospheric aging processes. During the Ice in Cloud Experiment – Layer Clouds (ICE-L in fall of 2007, smoke plumes from two small Wyoming Bureau of Land Management prescribed burns were measured by on-line aerosol instrumentation aboard a C-130 aircraft, providing a detailed chemical characterization of the particles. After ~2–4 min of aging, submicron smoke particles, produced primarily from sagebrush combustion, consisted predominantly of organics by mass, but were comprised primarily of internal mixtures of organic carbon, elemental carbon, potassium chloride, and potassium sulfate. Significantly, 100 % of the fresh biomass burning particles contained minor mass fractions of nitrate and sulfate, suggesting that hygroscopic material is incorporated very near or at the point of emission. The mass fractions of ammonium, sulfate, and nitrate increased with aging up to ~81–88 min and resulted in acidic particles, with both nitric acid and sulfuric acid present. Decreasing black carbon mass concentrations occurred due to dilution of the plume. Increases in the fraction of oxygenated organic carbon and the presence of dicarboxylic acids, in particular, were observed with aging. Cloud condensation nuclei measurements suggested all particles >100 nm were active at 0.5 % water supersaturation in the smoke plumes, confirming the relatively high hygroscopicity of the freshly emitted particles. For immersion/condensation freezing, ice nuclei measurements at −32 °C suggested activation of ~0.03–0.07 % of the particles with diameters greater than 500 nm.

  3. Chemical insights, explicit chemistry and yields of secondary organic aerosol from methylglyoxal and glyoxal

    Directory of Open Access Journals (Sweden)

    Y. B. Lim

    2013-02-01

    Full Text Available Atmospherically abundant, volatile water soluble organic compounds formed through gas phase chemistry (e.g., glyoxal (C2, methylglyoxal (C3 and acetic acid have great potential to form secondary organic aerosol (SOA via aqueous chemistry in clouds, fogs and wet aerosols. This paper (1 provides chemical insights into aqueous-phase OH radical-initiated reactions leading to SOA formation from methylglyoxal and (2 uses this and a previously published glyoxal mechanism (Lim et al., 2010 to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012. This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010, and is used to simulate the profiles of products and to estimate SOA yields.

    At cloud relevant concentrations (∼ 10−6–∼ 10−3 M; Munger et al., 1995 of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass are ∼ 120% for glyoxal and ∼ 80% for methylglyoxal. Oligomerization of unreacted aldehydes during droplet evaporation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (∼ 10 M, the major products are oligomers formed via organic radical-radical reactions, and simulated SOA yields (by mass are ∼ 90% for both glyoxal and methylglyoxal.

  4. Chemical composition and characteristics of ambient aerosols and rainwater residues during Indian summer monsoon: Insight from aerosol mass spectrometry

    Science.gov (United States)

    Chakraborty, Abhishek; Gupta, Tarun; Tripathi, Sachchida N.

    2016-07-01

    Real time composition of non-refractory submicron aerosol (NR-PM1) is measured via Aerosol mass spectrometer (AMS) for the first time during Indian summer monsoon at Kanpur, a polluted urban location located at the heart of Indo Gangetic Plain (IGP). Submicron aerosols are found to be dominated by organics followed by nitrate. Source apportionment of organic aerosols (OA) via positive matrix factorization (PMF) revealed several types of secondary/oxidized and primary organic aerosols. On average, OA are completely dominated by oxidized OA with a very little contribution from biomass burning OA. During rain events, PM1 concentration is decreased almost by 60%, but its composition remains nearly the same. Oxidized OA showed slightly more decrease than primary OAs, probably due to their higher hygroscopicity. The presence of organo nitrates (ON) is also detected in ambient aerosols. Apart from real-time sampling, collected fog and rainwater samples were also analyzed via AMS in offline mode and in the ICP-OES (Inductively coupled plasma - Optical emission spectrometry) for elements. The presence of sea salt, organo nitrates and sulfates has been observed. Rainwater residues are also dominated by organics but their O/C ratios are 15-20% lower than the observed values for ambient OA. Alkali metals such as Ca, Na, K are found to be most abundant in the rainwater followed by Zn. Rainwater residues are also found to be much less oxidized than the aerosols present inside the fog water, indicating presence of less oxidized organics. These findings indicate that rain can act as an effective scavenger of different types of pollutants even for submicron particle range. Rainwater residues also contain organo sulfates which indicate that some portion of the dissolved aerosols has undergone aqueous processing, possibly inside the cloud. Highly oxidized and possibly hygroscopic OA during monsoon period compared to other seasons (winter, post monsoon), indicates that they can act

  5. Development of an aerosol chemical transport model RAQM2 and predictions of Northeast Asian aerosol mass, size, chemistry, and mixing type

    Directory of Open Access Journals (Sweden)

    M. Kajino

    2012-05-01

    Full Text Available A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2, was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model (MADMS and achieved a completely dynamic (non-equilibrium solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized, in which the aerosols were distributed into 4 categories: Aitken mode (ATK, soot-free accumulation mode (ACM, soot aggregates (AGR, and coarse mode (COR. Condensation, evaporation, and Brownian coagulations for each category were solved dynamically. A regional-scale simulation (Δ x = 60 km was performed for the entire year of 2006 covering the Northeast Asian region. Statistical analyses showed that the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. The modeled PM1/bulk ratios of the chemical components were consistent with the observations, indicating that the simulations of aerosol mixing types were successful. Non-sea salt SO42- mixed with ATK + ACM was the largest at Hedo in summer, whereas it mixed with AGR was substantial in cold seasons. Ninety-eight percent of the modeled NO3- was mixed with sea salt at Hedo, whereas 53.7% of the NO3- was mixed with sea salt at Gosan, located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean makes the difference in the NO3- mixing type at the two sites. Because the aerosol mixing type alters optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

  6. Metal fractionation of atmospheric aerosols via sequential chemical extraction: a review

    Energy Technology Data Exchange (ETDEWEB)

    Smichowski, Patricia; Gomez, Dario [Unidad de Actividad Quimica, Comision Nacional de Energia Atomica, San Martin (Argentina); Polla, Griselda [Unidad de Actividad Fisica, Comision Nacional de Energia Atomica, San Martin (Argentina)

    2005-01-01

    This review surveys schemes used to sequentially chemically fractionate metals and metalloids present in airborne particulate matter. It focuses mainly on sequential chemical fractionation schemes published over the last 15 years. These schemes have been classified into five main categories: (1) based on Tessier's procedure, (2) based on Chester's procedure, (3) based on Zatka's procedure, (4) based on BCR procedure, and (5) other procedures. The operational characteristics as well as the state of the art in metal fractionation of airborne particulate matter, fly ashes and workroom aerosols, in terms of applications, optimizations and innovations, are also described. Many references to other works in this area are provided. (orig.)

  7. NUMERICAL SIMULATION WITH A COMPREHENSIVE CHEMICAL TRANSPORT MODEL OF NITRATE, SULFATE, AND AMMONIUM AEROSOL DISTRIBUTIONS OVER EAST ASIA

    Institute of Scientific and Technical Information of China (English)

    Meigen Zhang

    2005-01-01

    The transport and chemical production processes of nitrate, sulfate, and ammonium aerosols over East Asia were investigated by use of the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system coupled with the Regional Atmospheric Modeling System (RAMS). For the evaluation of the model's ability in depicting their3-dimensional concentration distributions and temporal variations, modeled concentrations of nitrate, sulfate, and ammonium aerosols are compared with the observations obtained at a ground station in Japan in March 2001 and onboard of an aircraft DC-8 on 18 and 21 March 2001 during the Transport and Chemical Evolution over the Pacific (TRACE-P)field campaign. Comparison shows that simulated values of nitrate, sulfate, and ammonium aerosols are generally in good agreement with their observed data, and the model captures most important observed features, and reproduces temporal and spatial variations of nitrate, sulfate, and ammonium aerosol concentrations reasonably well, e.g., the timing and locations of the concentration spikes of nitrate, sulfate, and ammonium aerosols are well reproduced, but large discrepancies between observed and simulated values are also clearly seen at some points and some times due to the coarse grid resolution and uncertainties of the emissions used in this study. This comparison results indicate that CMAQ is able to simulate the distributions of nitrate, sulfate, and ammonium aerosols and their related species in the troposphere over East Asia reasonably well.

  8. The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

    Directory of Open Access Journals (Sweden)

    R. Fröhlich

    2013-11-01

    Full Text Available We present a new instrument for monitoring aerosol composition, the time-of-flight aerosol chemical speciation monitor (ToF-ACSM, combining precision state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM. Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of −3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~ 8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation and calibration and analysis provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS measurements, performed during a first long-term deployment (> 10 months on the Jungfraujoch mountain ridge (3580 m a.s.l. in the Swiss Alps, agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th, as well as improving inorganic/organic separation.

  9. Chemical aging of m-xylene secondary organic aerosol: laboratory chamber study

    Directory of Open Access Journals (Sweden)

    J. H. Seinfeld

    2011-09-01

    Full Text Available Secondary organic aerosol (SOA can reside in the atmosphere for a week or more. While its initial formation from the gas-phase oxidation of volatile organic compounds tends to take place in the first few hours after emission, SOA can continue to evolve chemically over its atmospheric lifetime. Simulating this chemical aging over an extended time in the laboratory has proven to be challenging. We present here a procedure for studying SOA aging in laboratory chambers that is applied to achieve 36 h of oxidation. The formation and evolution of SOA from the photooxidation of m-xylene under low-NOx conditions and in the presence of either neutral or acidic seed particles is studied. In SOA aging, increasing molecular functionalization leads to less volatile products and an increase in SOA mass, whereas gas-phase or particle-phase fragmentation chemistry results in more volatile products and a loss of SOA. The challenge is to discern from measured chamber variables the extent to which these processes are important for a given SOA system. In the experiments conducted, m-xylene SOA mass increased over the initial 12-h of photooxidation and decreased beyond that time. The oxidation of the SOA, as manifested in the O:C elemental ratio and fraction of organic ion detected at m/z 44 measured by the Aerodyne aerosol mass spectrometer, decreased during the first 5 h of reaction, reached a minimum, and then increased continuously until the 36 h termination. This behavior is consistent with an initial period in which, as the mass of SOA increases, products of higher volatility partition to the aerosol phase, followed by an aging period in which gas- and particle-phase reaction products become increasingly more oxidized. After about 12–13 h, the SOA mass reaches a maximum and decreases, suggesting the existence of fragmentation chemistry. When irradiation is stopped 12.4 h into one experiment, and OH generation ceases, no loss of SOA is observed, indicating

  10. A Comparison of the OSHA Modified NIOSH Physical and Chemical Analytical Method (P and CAM) 304 and the Dust Trak Photometric Aerosol Sampler for 0-Chlorobenzylidine Malonitrile

    Science.gov (United States)

    2013-04-02

    form of smokes, dusts, fumes and mists . Naturally occurring aerosols include airborne dusts, clouds, mists , clay particles and sandstorms. Aerosol...CS is vaporized by the heat followed by condensation to an aerosol-particulate, and is assisted in dispersal throughout the chamber by fans (41...particulate monitor that measures contaminants such as dust, smoke, fumes and mists . This device is designed to conduct monitoring in industrial

  11. Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch

    Directory of Open Access Journals (Sweden)

    J. Cozic

    2008-01-01

    Full Text Available The chemical composition of submicron (fine mode and supermicron (coarse mode aerosol particles has been investigated at the Jungfraujoch high alpine research station (3580 m a.s.l., Switzerland as part of the GAW aerosol monitoring program since 1999. A clear seasonality was observed for all major components throughout the period with low concentrations in winter (predominantly free tropospheric aerosol and higher concentrations in summer (enhanced vertical transport of boundary layer pollutants. In addition, mass closure was attempted during intensive campaigns in March 2004, February–March 2005 and August 2005. Ionic, carbonaceous and non-refractory components of the aerosol were quantified as well as the PM1 and coarse mode total aerosol mass concentrations. A relatively low conversion factor of 1.8 for organic carbon (OC to particulate organic matter (OM was found in winter (February–March 2005. Organics, sulfate, ammonium, and nitrate were the major components of the fine aerosol fraction that were identified, while calcium and nitrate were the only two measured components contributing to the coarse mode. The aerosol mass concentrations for fine and coarse mode aerosol measured during the intensive campaigns were not typical of the long-term seasonality due largely to dynamical differences. Average fine and coarse mode concentrations during the intensive field campaigns were 1.7 μg m−3 and 2.4 μg m−3 in winter and 2.5 μg m−3 and 2.0 μg m−3 in summer, respectively. The mass balance of aerosols showed higher contributions of calcium and nitrate in the coarse mode during Saharan dust events (SDE than without SDE.

  12. Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch

    Directory of Open Access Journals (Sweden)

    J. Cozic

    2007-08-01

    Full Text Available The chemical composition of submicron (fine mode and supermicron (coarse mode aerosol particles has been investigated since 1999 within the GAW aerosol monitoring program at the high alpine research station Jungfraujoch (3580 m a.s.l., Switzerland. Clear seasonality was observed for all major components in the last 9 years with low concentrations in winter (predominantly free tropospheric aerosol and higher concentrations in summer (enhanced vertical transport of boundary layer pollutants. In addition, mass closure was attempted during intensive experiments in March 2004, February–March 2005 and August 2005. Ionic, carbonaceous and refractory components of the aerosol were quantified as well as the PM1 and coarse mode total aerosol mass concentrations. A relatively low conversion factor of 1.8 for organic carbon (OC to particulate organic matter (OM in winter (February–March 2005 was found. Organics, sulfate, ammonium, and nitrate were the major identified components of the fine aerosol fraction, while calcium and nitrate were the two major measured components in the coarse mode. The aerosol mass concentrations for fine and coarse mode aerosol during the intensive campaigns were not typical of the long term seasonality due largely to dynamical differences. Average fine and coarse mode concentrations during the intensive field campaigns were 1.7 μg m−3 and 2.4 μg m−3 in winter and 2.5 μg m−3 and 2.0 μg m−3 in summer, respectively. The mass balance of aerosols showed higher contributions of calcium and nitrate in the coarse mode during Saharan dust events (SDE than without SDE.

  13. The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties

    Directory of Open Access Journals (Sweden)

    M. J. Cubison

    2008-03-01

    Full Text Available The relationship between cloud condensation nuclei (CCN number and the physical and chemical properties of the atmospheric aerosol distribution is explored for a polluted urban data set from the Study of Organic Aerosols at Riverside I (SOAR-1 campaign conducted at Riverside, California, USA during summer 2005. The mixing state and, to a lesser degree, the average chemical composition are shown to be important parameters in determining the activation properties of those particles around the critical activation diameters for atmospherically-realistic supersaturation values. Closure between predictions and measurements of CCN number at several supersaturations is attempted by modeling a number of aerosol chemical composition and mixing state schemes of increasing complexity. It is shown that a realistic treatment of the state of mixing of the urban aerosol distribution is critical in order to eliminate model bias. Fresh emissions such as elemental carbon and small organic particles must be treated as non-activating and explicitly accounted for in the model scheme. The relative number concentration of these particles compared to inorganics and oxygenated organic compounds of limited hygroscopicity plays an important role in determining the CCN number. Furthermore, expanding the different composition/mixing state schemes to predictions of cloud droplet number concentration in a cloud parcel model highlights the dependence of cloud optical properties on the state of mixing and hygroscopic properties of the different aerosol modes, but shows that the relative differences between the different schemes are reduced compared to those from the CCN model.

  14. Peer-Assisted Tutoring in a Chemical Engineering Curriculum: Tutee and Tutor Experiences

    Science.gov (United States)

    Kieran, Patricia; O'Neill, Geraldine

    2009-01-01

    Peer-Assisted Tutorials (PATs), a form of Peer-Assisted Learning (PAL), were introduced to a conventional 4-year honours degree programme in Chemical Engineering. PATs were designed to support students in becoming more self-directed in their learning, to develop student confidence in tackling Chemical Engineering problems and to promote effective…

  15. Cloud Formation Potential of Biomass Burning Aerosol Surrogate-Particles Chemically Aged by OH

    Science.gov (United States)

    Slade, J. H.; Thalman, R. M.; Wang, J.; Li, Z. Q.; Knopf, D. A.

    2014-12-01

    Heterogeneous or multiphase reactions between trace gases such as OH and atmospheric aerosol can influence physicochemical properties of the particles including composition, morphology and lifetime. In this work, the cloud condensation nuclei (CCN) activity of laboratory-generated biomass burning aerosol (BBA) exposed to OH radicals is evaluated by determining the hygroscopicity parameter, κ, as a function of particle type and OH exposure ([OH]×time) using a CCN counter coupled to a custom-built aerosol flow reactor (AFR). The composition of particles collected by a micro-orifice uniform deposit impactor (MOUDI) first subjected to different OH exposures is analyzed by Raman and scanning transmission X-ray microscopy coupled with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative compounds found in BBA that have different hygroscopicity, chemical functionalities, and reactivity with OH radicals. BBA surrogate-particles are generated following atomization of aqueous solutions with mass ratios LEV:MNC:KS of 1:0:0, 0:1:0, 0:0:1, 1:1:0, 0:1:1, 1:0:1, 1:1:1, and 1:0.03:0.3. OH radicals are generated in the AFR following photolysis of O3 in the presence of H2O using a variable intensity ultra-violet (UV) lamp, which allows equivalent atmospheric OH exposures from days to weeks. In addition, we investigate how κ changes i) in response to varying [O3] with and without OH, and ii) at a fixed OH exposure while varying RH. The impact of OH exposure on the CCN activity of BBA will be presented and its atmospheric implications will be discussed.

  16. Radiolysis and hydrolysis of magnetically assisted chemical separation particles

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, B.A.; Nunez, L.; Vandegrift, G.F.

    1995-05-01

    The magnetically assisted chemical separation (MACS) process is designed to separate transuranic (TRU) elements out of high-level waste (HLW) or TRU waste. Magnetic microparticles (1--25 {mu}m) were coated with octyl (phenyl)N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in tributyl phosphate (TBP) and tested for removing TRU elements from acidic nitrate solutions. The particles were contacted with nitric acid solutions and Hanford plutonium finishing plant (PFP) simulant, irradiated with a high intensity {sup 60}Co {gamma}-ray source, and evaluated for effectiveness in removing TRU elements from 2m HNO{sub 3} solutions. The resistance of the coatings and magnetic cores to radiolytic damage and hydrolytic degradation was investigated by irradiating samples of particles suspended in a variety of solutions with doses of up to 5 Mrad. Transmission electron microscopy (TEM), magnetic susceptibility measurements, and physical observations of the particles and suspension solutions were used to assess physical changes to the particles. Processes that affect the surface of the particles dramatically alter the binding sites for TRU in solution. Hydrolysis played a larger role than radiolysis in the degradation of the extraction capacity of the particles.

  17. Aerosol-Assisted Self-Assembly of Reticulated N-Doped Carbonaceous Submicron Spheres for Effective Removal of Hexavalent Chromium.

    Science.gov (United States)

    He, Jiawei; Long, Yuan; Wang, Yiyan; Wei, Chaoliang; Zhan, Jingjing

    2016-07-01

    This Research Article described a facile one-step method to prepare reticulated N-doped carbonaceous submicron spheres. Through a simple aerosol-assisted technology, glucosamine sulfate used as a carbon source was aerosolized and carbonized to functionalized carbonaceous submicron spheres. The electrostatic attraction between protonated amino groups and sulfate in the aerosol droplets induced a self-assembly and led to the formation of reticular structure, avoiding the use of templates. Compared to bare carbonaceous materials produced from glucose, reticulated N-doped carbonaceous spheres exhibit higher efficiency in the removal of Cr(VI), where the doping of element nitrogen led to electrostatic attraction between protonated nitrogen and chromium ions, and reticulated structure created relatively higher surface area and pore volume, facilitating materials to contact with Cr(VI) ions. XPS characterization proved these novel N-doped carbonaceous materials could effectively transform Cr(VI) to less toxic Cr(III) because of the surface reducing groups. For the practical application, several factors including the initial pH, materials dosage and recycle numbers on the removal performance were studied.

  18. Laboratory analogues simulating Titan's atmospheric aerosols: Compared chemical compositions of grains and thin films

    Science.gov (United States)

    Carrasco, Nathalie; Jomard, François; Vigneron, Jackie; Etcheberry, Arnaud; Cernogora, Guy

    2016-09-01

    Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere. The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. The main parameter probed is the CH4/N2 ratio to explore various possible chemical regimes. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions could be explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes. The higher nitrogen content in the grains possibly involves a higher optical absorption than the one measured on the films, with a possible impact on Titan's radiative models.

  19. Chemical closure study on hygroscopic properties of urban aerosol particles in Sapporo, Japan.

    Science.gov (United States)

    Aggarwal, Shankar Gopala; Mochida, Michihiro; Kitamori, Yasuyuki; Kawamura, Kimitaka

    2007-10-15

    To assess the link between hygroscopicity of atmospheric particles and the chemical composition, we performed a chemical closure study on the hygroscopicity of organic-inorganic mixed particles nebulized from water extracts of ambient aerosols collected in Sapporo, Japan during summer 2005. The hygroscopicity of 100 nm particles was measured using a hygroscopicity tandem differential mobility analyzer (HTDMA) at 5-95% relative humidity. The chemical analyses of the extracts showed that inorganic salts accounted for 32-84% of the water-soluble fraction and that the remaining was water-soluble organic matter (WSOM). The liquid water content (LWC) of particles was primarily governed by the relative abundance of inorganic salts in particles. The chemical closure with a thermodynamic model did not indicate a significant perturbation of LWC by WSOM at 85% RH with the consideration of the uncertainties estimated. However, a positive perturbation by WSOM was suggested at 50% RH. Individual oxygenated compounds identified using gas chromatography were not abundant enough to substantially increase the LWC at 85% RH.

  20. Microbiology and atmospheric processes: biological, physical and chemical characterization of aerosol particles

    Science.gov (United States)

    Georgakopoulos, D. G.; Després, V.; Fröhlich-Nowoisky, J.; Psenner, R.; Ariya, P. A.; Pósfai, M.; Ahern, H. E.; Moffett, B. F.; Hill, T. C. J.

    2009-04-01

    The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e.g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques) required prior to comprehensive understanding of chemical and physical characterization of bioaerosols.

  1. Microbiology and atmospheric processes: biological, physical and chemical characterization of aerosol particles

    Directory of Open Access Journals (Sweden)

    D. G. Georgakopoulos

    2008-04-01

    Full Text Available The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e.g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques required prior to comprehensive understanding of chemical and physical characterization of bioaerosols.

  2. Microbiology and atmospheric processes: biological, physical and chemical characterization of aerosol particles

    Directory of Open Access Journals (Sweden)

    D. G. Georgakopoulos

    2009-04-01

    Full Text Available The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e.g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques required prior to comprehensive understanding of chemical and physical characterization of bioaerosols.

  3. Aerosol data assimilation in the chemical transport model MOCAGE during the TRAQA/ChArMEx campaign: aerosol optical depth

    Science.gov (United States)

    Sič, Bojan; El Amraoui, Laaziz; Piacentini, Andrea; Marécal, Virginie; Emili, Emanuele; Cariolle, Daniel; Prather, Michael; Attié, Jean-Luc

    2016-11-01

    In this study, we describe the development of the aerosol optical depth (AOD) assimilation module in the chemistry transport model (CTM) MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle). Our goal is to assimilate the spatially averaged 2-D column AOD data from the National Aeronautics and Space Administration (NASA) Moderate-resolution Imaging Spectroradiometer (MODIS) instrument, and to estimate improvements in a 3-D CTM assimilation run compared to a direct model run. Our assimilation system uses 3-D-FGAT (first guess at appropriate time) as an assimilation method and the total 3-D aerosol concentration as a control variable. In order to have an extensive validation dataset, we carried out our experiment in the northern summer of 2012 when the pre-ChArMEx (CHemistry and AeRosol MEditerranean EXperiment) field campaign TRAQA (TRAnsport à longue distance et Qualité de l'Air dans le bassin méditerranéen) took place in the western Mediterranean basin. The assimilated model run is evaluated independently against a range of aerosol properties (2-D and 3-D) measured by in situ instruments (the TRAQA size-resolved balloon and aircraft measurements), the satellite Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instrument and ground-based instruments from the Aerosol Robotic Network (AERONET) network. The evaluation demonstrates that the AOD assimilation greatly improves aerosol representation in the model. For example, the comparison of the direct and the assimilated model run with AERONET data shows that the assimilation increased the correlation (from 0.74 to 0.88), and reduced the bias (from 0.050 to 0.006) and the root mean square error in the AOD (from 0.12 to 0.07). When compared to the 3-D concentration data obtained by the in situ aircraft and balloon measurements, the assimilation consistently improves the model output. The best results as expected occur when the shape of the vertical profile is correctly simulated by the direct model. We

  4. Chemical apportionment of aerosol optical properties during the Asia-Pacific Economic Cooperation summit in Beijing, China

    Science.gov (United States)

    Han, Tingting; Xu, Weiqi; Chen, Chen; Liu, Xingang; Wang, Qingqing; Li, Jie; Zhao, Xiujuan; Du, Wei; Wang, Zifa; Sun, Yele

    2015-12-01

    We have investigated the chemical and optical properties of aerosol particles during the 2014 Asia-Pacific Economic Cooperation (APEC) summit in Beijing, China, using the highly time-resolved measurements by a high-resolution aerosol mass spectrometer and a cavity attenuated phase shift extinction monitor. The average (±σ) extinction coefficient (bext) and absorption coefficient (bap) were 186.5 (±184.5) M m-1 and 23.3 (±21.9) M m-1 during APEC, which were decreased by 63% and 56%, respectively, compared to those before APEC primarily due to strict emission controls. The aerosol composition and size distributions showed substantial changes during APEC; as a response, the mass scattering efficiency (MSE) of PM1 was decreased from 4.7 m2 g-1 to 3.5 m2 g-1. Comparatively, the average single-scattering albedo (SSA) remained relatively unchanged, illustrating the synchronous reductions of bext and bap during APEC. MSE and SSA were found to increase as function of the oxidation degree of organic aerosol (OA), indicating a change of aerosol optical properties during the aging processes. The empirical relationships between chemical composition and particle extinction were established using a multiple linear regression model. Our results showed the largest contribution of ammonium nitrate to particle extinction, accounting for 35.1% and 29.3% before and during APEC, respectively. This result highlights the important role of ammonium nitrate in the formation of severe haze pollution during this study period. We also observed very different optical properties of primary and secondary aerosol. Owing to emission controls in Beijing and surrounding regions and also partly the influences of meteorological changes, the average bext of secondary aerosol during APEC was decreased by 71% from 372.3 M m-1 to 108.5 M m-1, whereas that of primary aerosol mainly from cooking, traffic, and biomass burning emissions showed a smaller reduction from 136.7 M m-1 to 71.3 M m-1. As a result

  5. Size distribution and chemical composition of secondary organic aerosol formed from Cl-initiated oxidation of toluene

    Institute of Scientific and Technical Information of China (English)

    Mingqiang Huang; Weijun Zhang; Xuejun Gu; Changjin Hu; Weixiong Zhao; Zhenya Wang; Li Fang

    2012-01-01

    Secondary organic aerosol (SOA) formed from Cl-initiated oxidation of toluene was investigated in a home-made smog chamber.The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS),respectively.According to a large number of single aerosol diameter and mass spectra,the size distribution and chemical composition of SOA were obtained statistically.Experimental results showed that SOA particles created by Cl-initiated oxidation of toluene is predominantly in the form of fine particles,which have diameters less than 2.5 μm (i.e.,PM2.5),and glyoxal,benzaldehyde,benzyl alcohol,benzoquinone,benzoic acid,benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA.The possible reaction mechanisms leading to these products are also proposed.

  6. Airborne measurements of the spatial distribution of aerosol chemical composition across Europe and evolution of the organic fraction

    Directory of Open Access Journals (Sweden)

    W. T. Morgan

    2009-12-01

    Full Text Available The spatial distribution of aerosol chemical composition and the evolution of the Organic Aerosol (OA fraction is investigated based upon airborne measurements of aerosol chemical composition in the planetary boundary layer across Europe. Sub-micron aerosol chemical composition was measured using a compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS. A range of sampling conditions were evaluated, including relatively clean background conditions, polluted conditions in North-Western Europe and the near-field to far-field outflow from such conditions. Ammonium nitrate and OA were found to be the dominant chemical components of the sub-micron aerosol burden, with mass fractions ranging from 20–50% each. Ammonium nitrate was found to dominate in North-Western Europe during episodes of high pollution, reflecting the enhanced NOx and ammonia sources in this region. OA was ubiquitous across Europe and concentrations generally exceeded sulphate by 50–100%. A factor analysis of the OA burden was performed in order to probe the evolution across this large range of spatial and temporal scales. Two separate Oxygenated Organic Aerosol (OOA components were identified; one representing an aged-OOA, termed Low Volatility-OOA and another representing fresher-OOA, termed Semi Volatile-OOA on the basis of their mass spectral similarity to previous studies. The factors derived from different flights were not chemically the same but rather reflect the range of OA composition sampled during a particular flight. Significant chemical processing of the OA was observed downwind of major sources in North-Western Europe, with the LV-OOA component becoming increasingly dominant as the distance from source and photochemical processing increased. The measurements suggest that the aging of OA can be viewed as a continuum, with a progression from a less oxidised, semi-volatile component to a highly oxidised, less-volatile component. Substantial amounts of

  7. Pattern of aerosol mass loading and chemical composition over the atmospheric environment of an urban coastal station

    Science.gov (United States)

    Bindu, G.; Nair, Prabha R.; Aryasree, S.; Hegde, Prashant; Jacob, Salu

    2016-02-01

    Aerosol sampling was carried out at four locations in and around Cochin (9°58‧ N, 76°17‧ E), an urban area, located on the southwest coast of India. The gravimetric estimates of aerosol mass loading showed wide range from 78 μg m-3 to >450 μg m-3, occasionally reaching values >500 μg m-3, associated with regional source characteristics. Most of the values were above the air quality standard. Both boundary layer and synoptic scale airflow pattern play role in the temporal features in aerosol mass loading and chemical composition. Chemical analysis of the aerosol samples were done for anionic species viz; F-, Cl-, Br-, NO2-,   NO3-,   PO43-,   SO42- and metallic/cationic species viz; Na, Ca, K, Mg, NH4+, Fe, Al, Cu, Mg, Pb, etc using Ion Chromatography, Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma- Atomic Emission Spectroscopy (ICP-AES). At all the locations, extremely high mass concentration of SO42- was observed with the mean value of 13±6.4 μg m-3 indicating the strong anthropogenic influence. Statistical analysis of the chemical composition data was carried out and the principal factors presented. Seasonal variation of these chemical species along with their percentage contributions and regional variations were also examined. Increase in level of Na in aerosol samples indicated the influence of monsoonal activity. Most of the species showed mass concentrations well above those measured over another coastal site Thiruvananthapuram (8°29‧ N, 76°57‧ E) situated ~220 km south of Cochin revealing the highly localized aerosol features.

  8. Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

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    M. Radhi

    2010-07-01

    Full Text Available Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the Northern Hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol.

    Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. The aerosol optical depth data showed a clear though moderate seasonal cycle with an annual mean of 0.06 ± 0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. AERONET size distributions showed a generally bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of fine dust, biomass burning and marine biogenic material.

    In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – ion beam analysis and ion chromatography. Ion beam analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated with Si, with the Fe/Al ratio somewhat higher than values reported from Northern Hemisphere sites (as expected. Scatter plots for Ca, Mn and K against Si showed clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. These data may be used to attempt to build a signature of soil in this

  9. Aqueous organic chemistry in the atmosphere: sources and chemical processing of organic aerosols.

    Science.gov (United States)

    McNeill, V Faye

    2015-02-03

    Over the past decade, it has become clear that aqueous chemical processes occurring in cloud droplets and wet atmospheric particles are an important source of organic atmospheric particulate matter. Reactions of water-soluble volatile (or semivolatile) organic gases (VOCs or SVOCs) in these aqueous media lead to the formation of highly oxidized organic particulate matter (secondary organic aerosol; SOA) and key tracer species, such as organosulfates. These processes are often driven by a combination of anthropogenic and biogenic emissions, and therefore their accurate representation in models is important for effective air quality management. Despite considerable progress, mechanistic understanding of some key aqueous processes is still lacking, and these pathways are incompletely represented in 3D atmospheric chemistry and air quality models. In this article, the concepts, historical context, and current state of the science of aqueous pathways of SOA formation are discussed.

  10. Long-term Measurements of Submicrometer Aerosol Chemistry at the Southern Great Plains (SGP) Using an Aerosol Chemical Speciation Monitor (ACSM)

    Energy Technology Data Exchange (ETDEWEB)

    Parworth, Caroline; Fast, Jerome D.; Mei, Fan; Shippert, Timothy R.; Sivaraman, Chitra; Tilp, Alison; Watson, Thomas; Zhang, Qi

    2015-04-01

    In this study the long-term trends of non-refractory submicrometer aerosol (NR-PM1) composition and mass concentration measured by an Aerosol Chemical Speciation Monitor (ACSM) at the U.S. Department of Energy’s Southern Great Plains (SGP) site are discussed. Over the period of 19 months (Nov. 20, 2010 – June 2012) highly time resolved (~30 min.) NR-PM1 data was recorded. Using this dataset the value-added product (VAP) of deriving organic aerosol components (OACOMP) is introduced. With this VAP, multivariate analysis of the measured organic mass spectral matrix can be performed on long term data to return organic aerosol (OA) factors that are associated with distinct sources, evolution processes, and physiochemical properties. Three factors were obtained from this VAP including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a biomass burning OA (BBOA) factor. Back trajectory analyses were performed to investigate possible sources of major NR-PM1 species at the SGP site. Organics dominated NR-PM1 mass concentration for the majority of the study with the exception of winter, when nitrate increased due to transport of precursor species from surrounding urban and agricultural areas and also due to cooler temperatures. Sulfate mass concentrations showed little seasonal variation with mixed regional and local sources. In the spring BBOA emissions increased and were mainly associated with local fires. Isoprene and carbon monoxide emission rates were computed by the Model of Emissions of Gases and Aerosols from Nature (MEGAN) to represent the spatial distribution of biogenic and anthropogenic sources, respectively. From this model there is evidence to support that biogenic emissions from the southeast contribute to SOA formation at the SGP site during the summer.

  11. Aqueous-phase photooxidation of levoglucosan - a mechanistic study using aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS)

    Science.gov (United States)

    Zhao, R.; Mungall, E. L.; Lee, A. K. Y.; Aljawhary, D.; Abbatt, J. P. D.

    2014-09-01

    Levoglucosan (LG) is a widely employed tracer for biomass burning (BB). Recent studies have shown that LG can react rapidly with hydroxyl (OH) radicals in the aqueous phase despite many mass balance receptor models assuming it to be inert during atmospheric transport. In the current study, aqueous-phase photooxidation of LG by OH radicals was performed in the laboratory. The reaction kinetics and products were monitored by aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS). Approximately 50 reaction products were detected by the Aerosol ToF-CIMS during the photooxidation experiments, representing one of the most detailed product studies yet performed. By following the evolution of mass defects of product peaks, unique trends of adding oxygen (+O) and removing hydrogen (-2H) were observed among the products detected, providing useful information for determining potential reaction mechanisms and sequences. Additionally, bond-scission reactions take place, leading to reaction intermediates with lower carbon numbers. We introduce a data analysis framework where the average oxidation state (OSc) is plotted against a novel molecular property: double-bond-equivalence-to-carbon ratio (DBE/#C). The trajectory of LG photooxidation on this plot suggests formation of polycarbonyl intermediates and their subsequent conversion to carboxylic acids as a general reaction trend. We also determined the rate constant of LG with OH radicals at room temperature to be 1.08 ± 0.16 × 109 M-1 s-1. By coupling an aerosol mass spectrometer (AMS) to the system, we observed a rapid decay of the mass fraction of organic signals at mass-to-charge ratio 60 (f60), corresponding closely to the LG decay monitored by the Aerosol ToF-CIMS. The trajectory of LG photooxidation on a f44-f60 correlation plot matched closely to literature field measurement data. This implies that aqueous-phase photooxidation might be partially contributing to aging of BB particles in the

  12. Aqueous-phase photooxidation of levoglucosan - a mechanistic study using Aerosol Time of Flight Chemical Ionization Mass Spectrometry (Aerosol-ToF-CIMS)

    Science.gov (United States)

    Zhao, R.; Mungall, E. L.; Lee, A. K. Y.; Aljawhary, D.; Abbatt, J. P. D.

    2014-04-01

    Levoglucosan (LG) is a widely employed tracer for biomass burning (BB). Recent studies have shown that LG can react rapidly with hydroxyl (OH) radicals in the aqueous phase, despite many mass balance receptor models assuming it to be inert during atmospheric transport. In the current study, aqueous-phase photooxidation of LG by OH radicals was performed in the laboratory. The reaction kinetics and products were monitored by Aerosol Time of Flight Chemical Ionization Mass Spectrometry (Aerosol-ToF-CIMS). Approximately 50 reaction products were detected by the Aerosol-ToF-CIMS during the photooxidation experiments, representing one of the most detailed product studies yet performed. By following the evolution of mass defects of product peaks, unique trends of adding oxygen (+O) and removing hydrogen (-2H) were observed among the products detected, providing useful information to determine potential reaction mechanisms and sequences. As well, bond scission reactions take place, leading to reaction intermediates with lower carbon numbers. We introduce a data analysis framework where the average oxidation state (OSc) is plotted against a novel molecular property: double bond equivalence to carbon ratio (DBE / #C). The trajectory of LG photooxidation on this plot suggests formation of poly-carbonyl intermediates and their subsequent conversion to carboxylic acids as a general reaction trend. We also determined the rate constant of LG with OH radicals at room temperature to be 1.08 ± 0.16 × 109 M-1 s-1. By coupling an Aerosol Mass Spectrometer (AMS) to the system, we observed a rapid decay of the mass fraction of organic signals at mass-to-charge ratio 60 (f60), corresponding closely to the LG decay monitored by the Aerosol-ToF-CIMS. The trajectory of LG photooxidation on a f44-f60 correlation plot matched closely to literature field measurement data. This implies that aqueous-phase photooxidation might be partially contributing to aging of BB particles in the ambient

  13. Physical and chemical properties of pollution aerosol particles transported from North America to Greenland as measured during the POLARCAT summer campaign

    Directory of Open Access Journals (Sweden)

    B. Quennehen

    2011-04-01

    Full Text Available Within the framework of the POLARCAT-France campaign, aerosol physical, chemical and optical properties over Greenland were measured onboard the French ATR-42 research aircraft. The Lagrangian particle dispersion model FLEXPART was used to determine air mass origins. The study focuses particularly on the characterization of air masses transported from the North American continent. Air masses that picked up emissions from Canadian and Alaskan boreal forest fires as well as from the cities on the American east coast were identified and selected for a detailed study. Measurements of CO concentrations, aerosol chemical composition, aerosol size distributions, aerosol volatile fractions and aerosol light absorption (mainly from black carbon are used in order to study the relationship between CO enhancement, ageing of the air masses, aerosol particle concentrations and size distributions. Aerosol size distributions are in good agreement with previous studies, even though, wet scavenging potentially occurred along the pathway between the emission sources and Greenland leading to lower concentrations in the aerosol accumulation mode. The measured aerosol size distributions show a significant enhancement of Aitken mode particles. It is demonstrated that the Aitken mode is largely composed of black carbon, while the accumulation mode is more dominated by organics, as deduced from aerosol mass spectrometric AMS and aerosol volatility measurements. Overall, during the campaign rather small amounts of black carbon from the North American continent were transported towards Greenland. An important finding given the potential climate impacts of black carbon in the Arctic.

  14. Modeling chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx

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    J. Kazil

    2011-08-01

    Full Text Available Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN. Potential sources of CCN include wind-driven production of sea salt from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate CCN sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We conduct numerical simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx. The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation produces new aerosol in significant numbers. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number of particles produced

  15. Aerosol Types using Passive Remote Sensing: Global Distribution, Consistency Check, Total-Column Investigation and Translation into Composition Derived from Climate and Chemical Transport Model

    Science.gov (United States)

    Kacenelenbogen, M. S.; Dawson, K. W.; Johnson, M. S.; Burton, S. P.; Redemann, J.; Hasekamp, O. P.; Hair, J. W.; Ferrare, R. A.; Butler, C. F.; Holben, B. N.; Beyersdorf, A. J.; Ziemba, L. D.; Froyd, K. D.; Dibb, J. E.; Shingler, T.; Sorooshian, A.; Jimenez, J. L.; Campuzano Jost, P.; Jacob, D. J.

    2015-12-01

    To improve the predictions of aerosol composition in chemical transport models (CTMs) and global climate models (GCMs), we have developed an aerosol classification algorithm (called Specified Clustering and Mahalanobis Classification, SCMC) that assigns an aerosol type to multi-parameter retrievals by spaceborne, airborne or ground based passive remote sensing instruments [Russell et al., 2014]. The aerosol types identified by our scheme are pure dust, polluted dust, urban-industrial/developed economy, urban-industrial/developing economy, dark biomass smoke, light biomass smoke and pure marine. We apply the SCMC method to two different total-column datasets of aerosol optical properties: inversions from the ground-based AErosol RObotic NETwork (AERONET) and retrievals from the space-borne POLDER (Polarization and Directionality of Earth's Reflectances) instrument. The POLDER retrievals that we use differ from the standard POLDER retrievals [Deuzé et al., 2001] as they make full use of multi-angle, multispectral polarimetric data [Hasekamp et al., 2011]. We analyze agreement in the aerosol types inferred from both AERONET and POLDER globally. Then, we investigate how our total-column "effective" SCMC aerosol types relate to different aerosol types within the column (i.e. either a mixture of different types within one layer in the vertical or the stacking of different aerosol types within the vertical column). For that, we compare AERONET-SCMC aerosol types to collocated NASA LaRC HSRL vertically resolved aerosol types [Burton et al., 2012] during the SEAC4RS and DISCOVER-AQ airborne field experiments, mostly over Texas in Aug-Sept 2013. Finally, in order to evaluate the GEOS-Chem CTM aerosol types, we translate each of our SCMC aerosol type into a unique distribution of GEOS-Chem aerosol composition (e.g. biomass burning, dust, sulfate, sea salt). We bridge the gap between remote sensing and model-inferred aerosol types by using multiple years of collocated AERONET

  16. Satellite assisted aerosol correlation in a sequestered CO2 leakage controlled site

    Science.gov (United States)

    Landulfo, Eduardo; da Silva Lopes, Fábio J.; Nakaema, Walter M.; de Medeiros, José A. G.; Moreira, Andrea

    2014-10-01

    Currently one of the main challenges in CO2 storage research is to grant the development, testing and validation of accurate and efficient Measuring, Monitoring and Verification (MMV) techniques to be deployed at the final storage site, targeting maximum storage efficiency at the minimal leakage risk levels. For such task a mimetic sequestration site has been deployed in Florianopolis, Brazil, in order to verify the performance of monitoring plataforms to detect and quantify leakages of ground injected CO2, namely a Cavity Ring Down System (CRDS) - Los Gatos Research - an Eddy Covariance System (Campbell Scientific and Irgason) and meteorological tower for wind, humidity, precipitation and temperature monitoring onsite. The measurement strategy for detecting CO2 leakages can be very challenging since environmental and phytogenic influence can be very severe and play a role on determining if the values measured are unambiguous or not. One external factor to be considered is the amount of incoming solar radiation which will be the driving force for the whole experimental setup and following this reasoning the amount of aerosols in the atmospheric column can be a determinant factor influencing the experimental results. Thus the investigation of measured fluxes CO2 and its concentration with the aforementioned experimental instruments and their correlation with the aerosol data should be taken into account by means of satellite borne systems dedicated to measure aerosol vertical distribution and its optical properties, in this study we have selected CALIPSO and MODIS instrumentation to help on deriving the aerosol properties and CO2 measurements.

  17. Accessing the Impact of Sea-Salt Emissions on Aerosol Chemical Formation and Deposition Over Pearl River Delta, China

    Science.gov (United States)

    Fan, Q.; Wang, X.; Liu, Y.; Wu, D.; Chan, P. W.; Fan, S.; Feng, Y.

    2015-12-01

    Sea-salt aerosol (SSA) emissions have a significant impact on aerosol pollution and haze formation in the coastal areas. In this study, Models-3/CMAQ modeling system was utilized to access the impact of SSA emissions on aerosol chemical formation and deposition over Pearl River Delta (PRD), China in July 2006. More SSAs were transported inland from the open-ocean under the southeast wind in summertime. Two experiments (with and without SSA emissions in the CMAQ model) were set up to compare the modeling results with each other. The results showed that the increase of sulfate concentrations were more attributable to the primary emissions of coarse SO42- particles in SSA, while the increase of nitrate concentrations were more attributable to secondary chemical formations, known as the mechanisms of chloride depletion in SSA. In the coastal areas, 17.62 % of SO42-, 26.6% of NO3- and 38.2% of PM10 were attributed to SSA emissions, while those portions were less than 1% in the inland areas. The increases of PM10 and its components due to SSA emissions resulted in higher deposition fluxes over PRD, particularly in the coastal areas, except for the wet deposition of nitrate. Nitrate was more sensitive to SSA emissions in chemical formations than sulfate and dry deposition of aerosol was also more sensitive than that for wet deposition. Process analysis of sulfate and nitrate was applied to find out the difference of physical and chemical mechanisms between Guangzhou (the inland areas) and Zhuhai (the coastal areas). The negative contributions of dry deposition process to both sulfate and nitrate concentrations increased if SSA emissions were taken into account in the model, especially for Zhuhai. The negative contributions of cloud process also increased due to cloud scavenging and wet deposition process. In the coastal area, the gas-to-particle conversions became more active with high contributions of aerosol process to nitrate concentrations.

  18. The chemical composition of organic nitrogen in marine rainwater and aerosols

    Science.gov (United States)

    Altieri, K. E.; Hastings, M. G.; Peters, A.; Sigman, D. M.

    2010-12-01

    The current state of knowledge on organic nitrogen in the atmosphere is very limited. Atmospheric water soluble organic nitrogen (WSON) is a subset of the complex water soluble organic matter measured in atmospheric aerosols and rainwater; as such, it impacts cloud condensation processes and aerosol chemical and optical properties. In marine and continental atmospheric deposition, the organic N fraction can be 20-80% of total N potentially influencing receiving ecosystems. Therefore, atmospheric WSON plays an important role in both atmospheric chemistry and the global biogeochemical N cycle. However, the sources (i.e., anthropogenic vs. terrestrial vs. marine), composition (e.g., reduced or oxidized N), potential connections to inorganic N (NO3- and NH4+), and spatio-temporal variability of atmospheric WSON are largely unknown. Samples were collected on or near the island of Bermuda (32.27°N, 64.87°W), which is located in the western North Atlantic and experiences seasonal changes in transport that allow for study of both anthropogenically and primarily marine influenced air masses. Rainwater samples (n=7) and aqueous extracted aerosol samples (n=4) were analyzed by positive ion ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to characterize the chemical composition of the water soluble organic N on a per compound level. We found ~ 800 N containing compounds in 8 compound classes. The CHON+ compound class contained the largest number of N compounds (~ 460). Compared to continental rainwater [Altieri et al., ES&T, 2009], the CHON+ compounds in the marine samples are as dominant in number, yet have less regular patterns and lower O:C ratios for comparable N:C ratios. In fact, average O:C ratios of all N containing compound classes were lower in the marine samples than in continental rainwater samples. No organosulfates or nitrooxy-organosulfates were detected in the marine samples, both of

  19. A case study of the highly time-resolved evolution of aerosol chemical and optical properties in urban Shanghai, China

    Directory of Open Access Journals (Sweden)

    Y. Huang

    2013-04-01

    Full Text Available Characteristics of the chemical and optical properties of aerosols in urban Shanghai and their relationship were studied over a three-day period in October 2011. A suite of real-time instruments, including an Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS, a Monitor for AeRosols and GAses (MARGA, a Cavity Ring Down Spectrometer (CRDS, a nephelometer and a Scanning Mobility Particle Sizer (SMPS, was employed to follow the quick changes of the aerosol properties within the 72 h sampling period. The origin of the air mass arriving in Shanghai during this period shifted from the East China Sea to the northwest area of China, offering a unique opportunity to observe the evolution of aerosols influenced by regional transport from the most polluted areas in China. According to the meteorological conditions and temporal characterizations of the chemical and optical properties, the sampling period was divided into three periods. During Period 1 (00:00–23:00 LT, 13 October, the aerosols in urban Shanghai were mainly fresh and the single scattering albedo varied negatively with the emission of elemental carbon, indicating that local sources dominated. Period 2 (23:00 LT on 13 October to 10:00 LT on 15 October was impacted by regionally transported pollutants and had the highest particulate matter (PM mass loading and the lowest particle acidity, characterized by large fractions of aged particles and high secondary ion (nitrate, sulfate and ammonium mass concentrations. Comparison between ATOFMS particle acidity and quantitative particle acidity by MARGA indicated the significance of semi-quantitative calculation in ATOFMS. Two sub-periods were identified in Period 2 based on the scattering efficiency of PM1 mass. Period 3 (from 10:00 LT on 15 October to 00:00 LT on 16 October had a low PM1/PM10 ratio and a new particle formation event. The comparison of these sub-periods highlights the influence of particle mixing state on aerosol optical properties

  20. The Pasadena Aerosol Characterization Observatory (PACO): chemical and physical analysis of the Western Los Angeles basin aerosol

    Science.gov (United States)

    Hersey, S. P.; Craven, J. S.; Schilling, K. A.; Metcalf, A. R.; Sorooshian, A.; Chan, M. N.; Flagan, R. C.; Seinfeld, J. H.

    2011-08-01

    The Pasadena Aerosol Characterization Observatory (PACO) represents the first major aerosol characterization experiment centered in the Western/Central Los Angeles Basin. The sampling site, located on the campus of the California Institute of Technology in Pasadena, was positioned to sample a continuous afternoon influx of transported urban aerosol with a photochemical age of 1-2 h and generally free from major local contributions. Sampling spanned 5 months during the summer of 2009, which were broken into 3 regimes on the basis of distinct meteorological conditions. Regime I was characterized by a series of low pressure systems, resulting in high humidity and rainy periods with clean conditions. Regime II typified early summer meteorology, with significant morning marine layers and warm, sunny afternoons. Regime III was characterized by hot, dry conditions with little marine layer influence. Regardless of regime, organic aerosol (OA) is the most significant constituent of nonrefractory submicron Los Angeles aerosol (42, 43, and 55 % of total submicron mass in regimes I, II, and III, respectively). The overall oxidation state remains relatively constant on timescales of days to weeks (O:C = 0.44 ± 0.08, 0.55 ± 0.05, and 0.48 ± 0.08 during regimes I, II, and III, respectively), with no difference in O:C between morning and afternoon periods. Periods characterized by significant morning marine layer influence followed by photochemically favorable afternoons displayed significantly higher aerosol mass and O:C ratio, suggesting that aqueous processes may be important in the generation of secondary aerosol and oxidized organic aerosol (OOA) in Los Angeles. Online analysis of water soluble organic carbon (WSOC) indicates that water soluble organic mass (WSOM) reaches maxima near 14:00-15:00 local time (LT), but the percentage of AMS organic mass contributed by WSOM remains relatively constant throughout the day. Sulfate and nitrate reside predominantly in accumulation

  1. The Pasadena Aerosol Characterization Observatory (PACO: chemical and physical analysis of the Western Los Angeles basin aerosol

    Directory of Open Access Journals (Sweden)

    S. P. Hersey

    2011-08-01

    Full Text Available The Pasadena Aerosol Characterization Observatory (PACO represents the first major aerosol characterization experiment centered in the Western/Central Los Angeles Basin. The sampling site, located on the campus of the California Institute of Technology in Pasadena, was positioned to sample a continuous afternoon influx of transported urban aerosol with a photochemical age of 1–2 h and generally free from major local contributions. Sampling spanned 5 months during the summer of 2009, which were broken into 3 regimes on the basis of distinct meteorological conditions. Regime I was characterized by a series of low pressure systems, resulting in high humidity and rainy periods with clean conditions. Regime II typified early summer meteorology, with significant morning marine layers and warm, sunny afternoons. Regime III was characterized by hot, dry conditions with little marine layer influence. Regardless of regime, organic aerosol (OA is the most significant constituent of nonrefractory submicron Los Angeles aerosol (42, 43, and 55 % of total submicron mass in regimes I, II, and III, respectively. The overall oxidation state remains relatively constant on timescales of days to weeks (O:C = 0.44 ± 0.08, 0.55 ± 0.05, and 0.48 ± 0.08 during regimes I, II, and III, respectively, with no difference in O:C between morning and afternoon periods. Periods characterized by significant morning marine layer influence followed by photochemically favorable afternoons displayed significantly higher aerosol mass and O:C ratio, suggesting that aqueous processes may be important in the generation of secondary aerosol and oxidized organic aerosol (OOA in Los Angeles. Online analysis of water soluble organic carbon (WSOC indicates that water soluble organic mass (WSOM reaches maxima near 14:00–15:00 local time (LT, but the percentage of AMS organic mass contributed by WSOM remains relatively constant throughout the day. Sulfate and nitrate reside predominantly

  2. Chemical aging of m-xylene secondary organic aerosol: laboratory chamber study

    Directory of Open Access Journals (Sweden)

    J. H. Seinfeld

    2012-01-01

    Full Text Available Secondary organic aerosol (SOA can reside in the atmosphere for a week or more. While its initial formation from the gas-phase oxidation of volatile organic compounds tends to take place in the first few hours after emission, SOA can continue to evolve chemically over its atmospheric lifetime. Simulating this chemical aging over an extended time in the laboratory has proven to be challenging. We present here a procedure for studying SOA aging in laboratory chambers that is applied to achieve 36 h of oxidation. The formation and evolution of SOA from the photooxidation of m-xylene under low-NOx conditions and in the presence of either neutral or acidic seed particles is studied. In SOA aging, increasing molecular functionalization leads to less volatile products and an increase in SOA mass, whereas gas- or particle-phase fragmentation chemistry results in more volatile products and a loss of SOA. The challenge is to discern from measured chamber variables the extent to which these processes are important for a given SOA system. In the experiments conducted, m-xylene SOA mass, calculated under the assumption of size-invariant particle composition, increased over the initial 12–13 h of photooxidation and decreased beyond that time, suggesting the existence of fragmentation chemistry. The oxidation of the SOA, as manifested in the O:C elemental ratio and fraction of organic ion detected at m/z 44 measured by the Aerodyne aerosol mass spectrometer, increased continuously starting after 5 h of irradiation until the 36 h termination. This behavior is consistent with an initial period in which, as the mass of SOA increases, products of higher volatility partition to the aerosol phase, followed by an aging period in which gas- and particle-phase reaction products become increasingly more oxidized. When irradiation is stopped 12.4 h into one experiment, and OH generation ceases, minimal loss of SOA is observed, indicating that the loss of SOA is either

  3. The chemical composition of fine ambient aerosol particles in the Beijing area

    Science.gov (United States)

    Nekat, Bettina; van Pinxteren, Dominik; Iinuma, Yoshiteru; Gnauk, Thomas; Müller, Konrad; Herrmann, Hartmut

    2010-05-01

    The strong economical growth in China during the last few decades led to heavy air pollution caused by significantly increased particle emissions. The aerosol particles affect not only the regional air quality and visibility, but can also influence cloud formation processes and the radiative balance of the atmosphere by their optical and microphysical properties. The ability to act as Cloud Condensation Nuclei (CCN) is related to microphysical properties like the hygroscopic growth or the cloud droplet activation. The chemical composition of CCN plays an important role on these properties and varies strongly with the particle size and the time of day. Hygroscopic or surface active substances can increase the hygroscopicity and lower the surface tension of the particle liquid phase, respectively. The presence of such compounds may result in faster cloud droplet activation by faster water uptake. The DFG project HaChi (Haze in China) aimed at studying physical and chemical parameters of urban aerosol particles in the Beijing area in order to associate the chemical composition of aerosol particles with their ability to act as CCN. To this end, two measurement campaigns were performed at the Wuqing National Ordinary Meteorological Observing Station, which is a background site near Beijing. The winter campaign was realized in March 2009 and the summer campaign took place from mid July 2009 to mid August 2009. Fine particles with an aerodynamic diameter smaller than or equal 1 μm were continuously sampled for 24h over the two campaigns using a DIGITEL high volume sampler (DHA-80). The present contribution presents and discusses the results of the chemical characterization of the DIGITEL filters samples. The filters were analyzed for the mass concentration, inorganic ions and carbon sum parameters like elemental (EC), organic (OC) and water soluble organic carbon (WSOC). The WSOC fraction was further characterized for hygroscopic substances like low molecular

  4. Physical and Chemical Characterization of Particles in the Upper Troposphere and Lower Stratosphere: Microanalysis of Aerosol Impactor Samples

    Science.gov (United States)

    Sheridan, Patrick J.

    1999-01-01

    Herein is reported activities to support the characterization of the aerosol in the upper troposphere (UT) and lower stratosphere (LS) collected during the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) missions in 1994. Through a companion proposal, another group was to measure the size distribution of aerosols in the 0.008 to 2 micrometer diameter range and to collect for us impactor samples of particles larger than about 0.02 gm. In the first year, we conducted laboratory studies related to particulate deposition patterns on our collection substrates, and have performed the analysis of many ASHOE/MAESA aerosol samples from 1994 using analytical electron microscopy (AEM). We have been building an "aerosol climatology" with these data that documents the types and relative abundances of particles observed at different latitudes and altitudes. The second year (and non-funded extension periods) saw continued analyses of impactor aerosol samples, including more ASHOE/MAESA samples, some northern hemisphere samples from the NASA Stratospheric Photochemistry Aerosols and Dynamics Expedition (SPADE) program for comparison, and a few aerosol samples from the NASA Stratospheric TRacers of Atmospheric Transport (STRAT) program. A high-resolution field emission microscope was used for the analysis and re-analysis of a number of samples to determine if this instrument was superior in performance to our conventional electron microscope. In addition, some basic laboratory studies were conducted to determine the minimum detectable and analyzable particle size for different types of aerosols. In all, 61 aerosol samples were analyzed, with a total of over 30,000 individual particle analyses. In all analyzed samples, sulfate particles comprised the major aerosol number fraction. It must be stressed that particles composed of more than one species, for example sulfate and organic carbon, were classified

  5. Seasonal characterization of submicron aerosol chemical composition and organic aerosol sources in the southeastern United States: Atlanta, Georgia,and Look Rock, Tennessee

    Science.gov (United States)

    Hapsari Budisulistiorini, Sri; Baumann, Karsten; Edgerton, Eric S.; Bairai, Solomon T.; Mueller, Stephen; Shaw, Stephanie L.; Knipping, Eladio M.; Gold, Avram; Surratt, Jason D.

    2016-04-01

    A year-long near-real-time characterization of non-refractory submicron aerosol (NR-PM1) was conducted at an urban (Atlanta, Georgia, in 2012) and rural (Look Rock, Tennessee, in 2013) site in the southeastern US using the Aerodyne Aerosol Chemical Speciation Monitor (ACSM) collocated with established air-monitoring network measurements. Seasonal variations in organic aerosol (OA) and inorganic aerosol species are attributed to meteorological conditions as well as anthropogenic and biogenic emissions in this region. The highest concentrations of NR-PM1 were observed during winter and fall seasons at the urban site and during spring and summer at the rural site. Across all seasons and at both sites, NR-PM1 was composed largely of OA (up to 76 %) and sulfate (up to 31 %). Six distinct OA sources were resolved by positive matrix factorization applied to the ACSM organic mass spectral data collected from the two sites over the 1 year of near-continuous measurements at each site: hydrocarbon-like OA (HOA), biomass burning OA (BBOA), semi-volatile oxygenated OA (SV-OOA), low-volatility oxygenated OA (LV-OOA), isoprene-derived epoxydiols (IEPOX) OA (IEPOX-OA) and 91Fac (a factor dominated by a distinct ion at m/z 91 fragment ion previously observed in biogenic influenced areas). LV-OOA was observed throughout the year at both sites and contributed up to 66 % of total OA mass. HOA was observed during the entire year only at the urban site (on average 21 % of OA mass). BBOA (15-33 % of OA mass) was observed during winter and fall, likely dominated by local residential wood burning emission. Although SV-OOA contributes quite significantly ( ˜ 27 %), it was observed only at the urban site during colder seasons. IEPOX-OA was a major component (27-41 %) of OA at both sites, particularly in spring and summer. An ion fragment at m/z 75 is well correlated with the m/z 82 ion associated with the aerosol mass spectrum of IEPOX-derived secondary organic aerosol (SOA). The

  6. Chemically-resolved volatility measurements of organic aerosol fom different sources.

    Science.gov (United States)

    Huffman, J A; Docherty, K S; Mohr, C; Cubison, M J; Ulbrich, I M; Ziemann, P J; Onasch, T B; Jimenez, J L

    2009-07-15

    A newly modified fast temperature-stepping thermodenuder (TD) was coupled to a High Resolution Time-of-Flight Aerosol Mass Spectrometer for rapid determination of chemically resolved volatility of organic aerosols (OA) emitted from individual sources. The TD-AMS system was used to characterize primary OA (POA) from biomass burning, trash burning surrogates (paper and plastic), and meat cooking as well as chamber-generated secondary OA (SOA) from alpha-pinene and gasoline vapor. Almost all atmospheric models represent POA as nonvolatile, with no allowance for evaporation upon heating or dilution, or condensation upon cooling. Our results indicate that all OAs observed show semivolatile behavior and that most POAs characterized here were at least as volatile as SOA measured in urban environments. Biomass-burning OA (BBOA) exhibited a wide range of volatilities, but more often showed volatility similar to urban OA. Paper-burning resembles some types of BBOA because of its relatively high volatility and intermediate atomic oxygen-to-carbon (O/C) ratio, while meat-cooking OAs (MCOA) have consistently lower volatility than ambient OA. Chamber-generated SOA under the relatively high concentrations used intraditional experiments was significantly more volatile than urban SOA, challenging extrapolation of traditional laboratory volatility measurements to the atmosphere. Most OAs sampled show increasing O/C ratio and decreasing H/C (hydrogen-to-carbon) ratio with temperature, further indicating that more oxygenated OA components are typically less volatile. Future experiments should systematically explore a wider range of mass concentrations to more fully characterize the volatility distributions of these OAs.

  7. Analysis of Aerosol Physical and Chemical Properties on the Coast of the Japanese Sea (Tango peninsula) during ACE-Asia

    Science.gov (United States)

    Tohno, S.; Hoeller, R.; Ito, K.; Onishi, Y.; Ma, C. J.; Kasahara, M.; Cahill, T. A.; Cliff, S.

    2001-12-01

    During springtime the Japanese archipelago is periodically influenced by haze events originating from the Asian continent. The sources of these materials include both anthropogenic and natural aerosol, including the well-known yellow sand (Kosa) events, which can be recognized at places as far as Hawaii and the west coast of the United States. But there is also strong evidenced, which we want to support in this study, that these Kosa events are accompanied by strongly absorbing material as well as sulfates and organics. The springtime of 2001 was characterized by several strong dust events, which happened to be during the international ACE-Asia campaign. We participated in the ACE observation network by setting up a monitoring station during the period March 19 to April 6, 2001 for the measurement of aerosol optical, physical and chemical properties as well as observations of sky radiation. The measurement site is located on the coast of the Japanese Sea (Tango Peninsula, Kyoto Prefecture). Tango was chosen as an observation site, since it is relatively unpolluted and can therefore serve as a background site for studies of the direct impact of the mainland Asian outflow on the western Pacific area. The purpose of this work is to perform local and column closure experiments on aerosol properties, and to distinguish the anthropogenic part of the aerosol from the natural one. For this purpose, backward air-mass trajectories are calculated to identify potential sources of the observed aerosol. For measurements of aerosol mass-size distributions we used 12-stage low-pressure impactors, which were subsequently analyzed for elemental and ionic concentrations by PIXE, and Ion-chromatography, respectively. In addition, to get both the necessary time- and size-resolution, a DRUM sampler was operated with continuous collection and analysis for mass and optical transmission from 320 nm to 850 nm. Analysis is scheduled by synchrotron-XRF to http://aerosol.energy.kyoto- u.ac.jp/~hoeller/ACEmineyama.html

  8. Uptake of Organic Vapors by Sulfate Aerosols: Physical and Chemical Processes

    Science.gov (United States)

    Michelsen, R. R.; Ashbourn, S. F. M.; Iraci, L.T.; Staton, S. J. R.

    2003-01-01

    While it is known that upper tropospheric sulfate particles contain a significant amount of organic matter, both the source of the organic fraction and its form in solution are unknown. These studies explore how the chemical characteristics of the molecules and surfaces in question affect heterogeneous interactions. The solubilities of acetaldehyde [CH3CHO] and ethanol [CH3CH20H] in cold, aqueous sulfuric acid solutions have been measured by Knudsen cell studies. Henry's law solubility coefficients range from 10(exp 2) to 10(exp 5) M/atm for acetaldehyde, and from 10(exp 4) to 10(exp 9) M/atm for ethanol under upper tropospheric conditions (210-240 K, 40-80 wt. % H2S04). The multiple solvation pathways (protonation, enolization, etc.) available to these compounds in acidic aqueous environments will be discussed. Preliminary results from the interaction of acetaldehyde with solutions of formaldehyde in sulfuric acid will be presented as well. The physical and chemical processes that affect organic uptake by aqueous aerosols will be explored, with the aim of evaluating organic species not yet studied in low temperature aqueous sulfuric acid.

  9. Temperature effect on physical and chemical properties of secondary organic aerosol from m-xylene photooxidation

    Directory of Open Access Journals (Sweden)

    D. R. Cocker III

    2010-01-01

    Full Text Available The chemical and physical differences of secondary organic aerosol (SOA formed at select isothermal temperatures (278 K, 300 K, and 313 K are explored with respect to density, particle volatility, particle hygroscopicity, and elemental chemical composition. A transition point in SOA density, volatility, hygroscopicity and elemental composition is observed near 290–292 K as SOA within an environmental chamber is heated from 278 K to 313 K, indicating the presence of a thermally labile compound. No such transition points are observed for SOA produced at 313 K or 300 K and subsequently cooled to 278 K. The SOA formed at the lowest temperatures (278 K is more than double the SOA formed at 313 K. SOA formed at 278 K is less hydrophilic and oxygenated while more volatile and dense than SOA formed at 300 K or 313 K. The properties of SOA formed at 300 K and 313 K when reduced to 278 K did not match the properties of SOA initially formed at 278 K. This study demonstrates that it is insufficient to utilize the enthalpy of vaporization when predicting SOA temperature dependence.

  10. Correlations between Optical, Chemical and Physical Properties ofBiomass Burn Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, Rebecca J.; Lewis, K.; Desyaterik, Yury; Wang, Z.; Tivanski, Alexei V.; Arnott, W.P.; Laskin, Alexander; Gilles, M.K.

    2008-01-29

    Aerosols generated from burning different plant fuels were characterized to determine relationships between chemical, optical and physical properties. Single scattering albedo ({omega}) and Angstrom absorption coefficients ({alpha}{sub ap}) were measured using a photoacoustic technique combined with a reciprocal nephelometer. Carbon-to-oxygen atomic ratios, sp{sup 2} hybridization, elemental composition and morphology of individual particles were measured using scanning transmission X-ray microscopy coupled with near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) and scanning electron microscopy with energy dispersion of X-rays (SEM/EDX). Particles were grouped into three categories based on sp2 hybridization and chemical composition. Measured {omega} (0.4-1.0 at 405 nm) and {alpha}{sub ap} (1.0-3.5) values displayed a fuel dependence. The category with sp{sup 2} hybridization >80% had values of {omega} (<0.5) and {alpha}{sub ap} ({approx}1.25) characteristic of light absorbing soot. Other categories with lower sp2 hybridization (20 to 60%) exhibited higher {omega} (>0.8) and {alpha}{sub ap} (1.0 to 3.5) values, indicating increased absorption spectral selectivity.

  11. Handheld hyperspectral imager for standoff detection of chemical and biological aerosols

    Science.gov (United States)

    Hinnrichs, Michele; Jensen, James O.; McAnally, Gerard

    2004-08-01

    Pacific Advanced Technology has developed a small hand held imaging spectrometer, Sherlock, for gas leak and aerosol detection and imaging. The system is based on a patented technique, (IMSS Image Multi-spectral Sensing), that uses diffractive optics and image processing algorithms to detect spectral information about objects in the scene of the camera. This cameras technology has been tested at Dugway Proving Ground and Dstl Porton Down facilities looking at Chemical and Biological agent simulants. In addition to Chemical and Biological detection, the camera has been used for environmental monitoring of green house gases and is currently undergoing extensive laboratory and field testing by the Gas Technology Institute, British Petroleum and Shell Oil for applications for gas leak detection and repair. In this paper we will present some of the results from the data collection at the TRE test at Dugway Proving Ground during the summer of 2002 and laboratory testing at the Dstl facility at Porton Down in the UK in the fall of 2002.

  12. Aerosol-Assisted Synthesis of Monodisperse Single-Crystalline α-Cristobalite Nanospheres

    OpenAIRE

    Jiang, Xingmao; Bao, Lihong; Cheng, Yung-Sung; Dunphy, Darren R.; Li, Xiaodong; Brinker, C. Jeffrey

    2011-01-01

    Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity nanocrystalline α-cristobalite is important for catalysis, nanocomposites, advanced polishing, and und...

  13. The Pasadena Aerosol Characterization Observatory (PACO: chemical and physical analysis of the Western Los Angeles Basin aerosol

    Directory of Open Access Journals (Sweden)

    S. P. Hersey

    2011-02-01

    Full Text Available The Pasadena Aerosol Characterization Observatory (PACO represents the first major aerosol characterization experiment centered in the Western/Central Los Angeles Basin. The sampling site, located on the campus of the California Institute of Technology in Pasadena, was positioned to sample a continuous afternoon influx of transported urban aerosol with a photochemical age of 1–2 h and generally free from major local contributions. Sampling spanned 5 months during the summer of 2009, which were broken into 3 regimes on the basis of distinct meteorological conditions. Regime I was characterized by a series of low pressure systems, resulting in high humidity and rainy periods with clean conditions. Regime II typified early summer meteorology, with significant morning marine layers and warm, sunny afternoons. Regime III was characterized by hot, dry conditions with little marine layer influence.

    Organic aerosol (OA is the most significant constituent of Los Angeles aerosol (42, 43, and 55% of total submicron mass in regimes I, II, and III, respectively, and that the overall oxidation state remains relatively constant on timescales of days to weeks (O:C = 0.44 ± 0.08, 0.55 ± 0.05, and 0.48 ± 0.08 during regimes I, II, and III, respectively, with no difference in O:C between morning and afternoon periods. Periods characterized by significant morning marine layer influence followed by photochemically favorable afternoons displayed significantly higher aerosol mass and O:C ratio, suggesting that aqueous processes may be important in the generation of secondary aerosol and oxidized organic aerosol (OOA in Los Angeles.

    Water soluble organic mass (WSOM reaches maxima near 14:00–15:00 local time (LT, but the percentage of AMS organic mass contributed by WSOM remains relatively constant throughout the day. Sulfate and nitrate reside predominantly in accumulation mode aerosol, while afternoon SOA production coincides with the

  14. Urban aerosol in Oporto, Portugal: Chemical characterization of PM10 and PM2.5

    Science.gov (United States)

    Custódio, Danilo; Ferreira, Catarina; Alves, Célia; Duarte, Mácio; Nunes, Teresa; Cerqueira, Mário; Pio, Casimiro; Frosini, Daniele; Colombi, Cristina; Gianelle, Vorne; Karanasiou, Angeliki; Querol, Xavier

    2014-05-01

    Several urban and industrial areas in Southern Europe are not capable of meeting the implemented EU standards for particulate matter. Efficient air quality management is required in order to ensure that the legal limits are not exceeded and that the consequences of poor air quality are controlled and minimized. Many aspects of the direct and indirect effects of suspended particulate matter on climate and public health are not well understood. The temporal variation of the chemical composition is still demanded, since it enables to adopt off-set strategies and to better estimate the magnitude of anthropogenic forcing on climate. This study aims to provide detailed information on concentrations and chemical composition of aerosol from Oporto city, an urban center in Southern Europe. This city is located near the coast line in the North of Portugal, being the country's second largest urban area. Moreover, Oporto city economic prospects depend heavily on a diversified industrial park, which contribute to air quality degradation. Another strong source of air pollution is traffic. The main objectives of this study are: 1) to characterize the chemical composition of PM10 and PM2.5 by setting up an orchestra of aerosol sampling devices in a strategic place in Oporto; 2) to identify the sources of particles exploring parameters such as organic and inorganic markers (e.g. sugars as tracers for biomass burning; metals and elemental carbon for industrial and vehicular emissions); 3) to evaluate long range transport of pollutants using back trajectory analysis. Here we present data obtained between January 2013 and January 2014 in a heavy traffic roadside sampling site located in the city center. Different PM10 and PM2.5 samplers were operated simultaneously in order to collect enough mass on different filter matrixes and to fulfill the requirements of analytical methodologies. More than 100 aerosol samples were collected and then analysed for their mass concentration and

  15. Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation

    Directory of Open Access Journals (Sweden)

    E. Asmi

    2009-12-01

    Full Text Available The Antarctic near-coastal sub-micrometre aerosol particle features in summer were characterised based on measured data on aerosol hygroscopicity, size distributions, volatility and chemical ion and organic carbon mass concentrations. Hysplit model was used to calculate the history of the air masses to predict the particle origin. Additional measurements of meteorological parameters were utilised. The hygroscopic properties of particles mostly resembled those of marine aerosols. The measurements took place at 130 km from the Southern Ocean, which was the most significant factor affecting the particle properties. This is explained by the lack of additional sources on the continent of Antarctica. The Southern Ocean was thus a likely source of the particles and nucleating and condensing vapours. The particles were very hygroscopic (HGF 1.75 at 90 nm and very volatile. Most of the sub-100 nm particle volume volatilised below 100 °C. Based on chemical data, particle hygroscopic and volatile properties were explained by a large fraction of non-neutralised sulphuric acid together with organic material. The hygroscopic growth factors assessed from chemical data were similar to measured. Hygroscopicity was higher in dry continental air masses compared with the moist marine air masses. This was explained by the aging of the marine organic species and lower methanesulphonic acid volume fraction together with the changes in the inorganic aerosol chemistry as the aerosol had travelled long time over the continental Antarctica. Special focus was directed in detailed examination of the observed new particle formation events. Indications of the preference of negative over positive ions in nucleation could be detected. However, in a detailed case study, the neutral particles dominated the particle formation process. Freshly nucleated particles had the smallest hygroscopic growth factors, which increased subsequent to particle aging.

  16. Optical-chemical relationships for carbonaceous aerosols observed at Jeju Island, Korea with a 3-laser photoacoustic spectrometer

    Directory of Open Access Journals (Sweden)

    B. A. Flowers

    2010-04-01

    Full Text Available Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 76% of the deployment days, showing large variations in their measured chemical and optical properties. Our analysis of eight distinct episodes, spanning a wide range of chemical composition, optical properties, and source regions, reveals that at episodes with higher OC/SO2−4 and NO3/SO2−4 composition ratios exhibit lower single scatter albedo at shorter wavelengths (ω405; significantly lower [ω405meas = 0.79±0.06, ω405calc = 0.86±0.01] than predicted by an optical model that assumes constant complex index of refraction with wavelength (an optical model of soot. We attribute this discrepancy to enhanced absorption by organic material. Organic carbon absorption accounts for up to 50% of the measured aerosol absorption at 405 nm for the high OC/SO2−4 episode. Coatings of elemental carbon aerosol cores are hypothesized to increase absorption by factors up to 6 at visible wavelengths. Carbonaceous aerosol absorption can alter global radiative forcing estimates substantially, underscoring the need to understand and predict chemical composition effects on optical properties.

  17. Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation

    Directory of Open Access Journals (Sweden)

    E. Asmi

    2010-05-01

    Full Text Available The Antarctic near-coastal sub-micrometre aerosol particle features in summer were characterised based on measured data on aerosol hygroscopicity, size distributions, volatility and chemical ion and organic carbon mass concentrations. Hysplit model was used to calculate the history of the air masses to predict the particle origin. Additional measurements of meteorological parameters were utilised. The hygroscopic properties of particles mostly resembled those of marine aerosols. The measurements took place at 130 km from the Southern Ocean, which was the most significant factor affecting the particle properties. This is explained by the lack of additional sources on the continent of Antarctica. The Southern Ocean was thus a likely source of the particles and nucleating and condensing vapours. The particles were very hygroscopic (HGF 1.75 at 90 nm and very volatile. Most of the sub-100 nm particle volume volatilised below 100 °C. Based on chemical data, particle hygroscopic and volatile properties were explained by a large fraction of non-neutralised sulphuric acid together with organic material. The hygroscopic growth factors assessed from chemical data were similar to measured. Hygroscopicity was higher in dry continental air masses compared with the moist marine air masses. This was explained by the aging of the marine organic species and lower methanesulphonic acid volume fraction together with the changes in the inorganic aerosol chemistry as the aerosol had travelled long time over the continental Antarctica. Special focus was directed in detailed examination of the observed new particle formation events. Indications of the preference of negative over positive ions in nucleation could be detected. However, in a detailed case study, the neutral particles dominated the particle formation process. Freshly nucleated particles had the smallest hygroscopic growth factors, which increased subsequent to particle aging.

  18. Chemical composition of size-segregated aerosols in Lhasa city, Tibetan Plateau

    Science.gov (United States)

    Wan, Xin; Kang, Shichang; Xin, Jinyuan; Liu, Bin; Wen, Tianxue; Wang, Pengling; Wang, Yuesi; Cong, Zhiyuan

    2016-06-01

    To reveal the chemical characteristics of size-segregated aerosols in the high-altitude city of Tibetan Plateau, eight-size aerosol samples were collected in Lhasa from March 2013 to February 2014. The annual mean of online PM2.5 was 25.0 ± 16.0 μg m- 3, which was much lower than Asian cities but similar with some European cities. The annual mean concentrations of organic carbon (OC, 7.92 μg m- 3 in PM2.1 and 12.66 μg m- 3 in PM9.0) and elemental carbon (EC, 1.00 μg m- 3 in PM2.1 and 1.21 μg m- 3 in PM9.0) in Lhasa aerosols were considerably lower than those heavily polluted cities such as Beijing and Xi'an, China and Kathmandu, Nepal. Sulfate, NO3-, NH4+ and Ca2 + were 0.75 ± 0.31, 0.82 ± 0.35, 0.38 ± 0.34 and 0.57 ± 0.29 μg m- 3 in fine particles while in coarse particles they were 0.57 ± 0.37, 0.73 ± 0.23, 0.07 ± 0.03 and 2.52 ± 1.37 μg m- 3, respectively. Secondary water-soluble ions composed 35.8% of the total ionic components in fine particles according to the established electroneutrality, while in coarse particles they took up only 9.3%. Ca2 + (40.6%) was the major component of the coarse particles. For seasonality, the concentrations of OC, EC, SO42 -, NH4+, K+, Ca2 +, Mg2 +, Cl- and Na+ presented higher values during late autumn and winter but were relatively lower in spring and summer. Nevertheless, NO3- was considerably higher in summer and autumn, presumably due to increased tourist-vehicle emissions. During winter and spring, [Ca2 +]/[NO3-+ SO42 -] ratios in coarse particles showed higher values of 7.31 and 6.17, respectively, emphasizing the dust influence. [NO3-]/[SO42 -] ratios in fine particles during spring, summer and autumn exceeding 1 indicated that the currently predominant vehicle exhaust makes a greater contribution to the aerosols. While more stationary sources such as coal and biomass burning existed in winter since the [NO3-]/[SO42 -] ratio was less than 1. Different sources and formation processes lead to a bimodal size

  19. 2014 iAREA campaign on aerosol in Spitsbergen - Part 1: Study of physical and chemical properties

    Science.gov (United States)

    Lisok, J.; Markowicz, K. M.; Ritter, C.; Makuch, P.; Petelski, T.; Chilinski, M.; Kaminski, J. W.; Becagli, S.; Traversi, R.; Udisti, R.; Rozwadowska, A.; Jefimow, M.; Markuszewski, P.; Neuber, R.; Pakszys, P.; Stachlewska, I. S.; Struzewska, J.; Zielinski, T.

    2016-09-01

    This paper presents the results of measurements of aerosol physical and chemical properties during iAREA2014 campaign that took place on Svalbard between 15th of Mar and 4th of May 2014. With respect to field area, the experiment consisted of two sites: Ny-Ålesund (78°55‧N, 11°56‧E) and Longyearbyen (78°13‧N, 15°33‧E) with further integration of Aerosol Robotic Network (AERONET) station in Hornsund (77°00‧N, 15°33‧E). The subject of this study is to investigate the in-situ, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol single-scattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced single-scattering properties due to the existence of sulphate and additional sea-salt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEM-AQ model and by chemical observations that indicated up to 45% contribution of the sea-salt to a PM10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Ångstrom exponent indicated that slightly larger particles dominated during special events. The in-situ surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive single-scattering properties indicate a diurnal cycle in Longyearbyen, where 21:00-5:00 data stays at the background level, however increasing during the day by the factor of 3-4. It is considered to be highly connected with local emissions originating

  20. Chemical Composition, Seasonal Variation and Size distribution of Atmospheric Aerosols at an Alpine Site in Guanzhong Plain, China

    Science.gov (United States)

    Li, J.

    2015-12-01

    PM10 and size-segregated aerosol samples were collected at Mt. Hua (2065 a.s.m) in central China, and determined for carbonaceous fraction, ions and organic composition. The concentration of most chemical compositions in summer are lower than those in winter, due to decreased emissions of biomass and coal burning for house heating. High temperature and relative humidity (RH) conditions are favorable for secondary aerosol formation, resulting in higher concentrations of SO42- and NH4+ in summer. Non-dehydrated sugars are increased in summer because of the enhanced metabolism. Carbon preference index results indicate that n-alkanes at Mt. Hua are derived mostly by plant wax. Low Benzo(a)pyrene/Benzo(a)pyrene ratios indicate that mountain aerosols are more aged. Concentrations of biogenic (BSOA, the isoprene/pinene/caryophyllene oxidation products) and anthropogenic (ASOA, mainly aromatic acids) SOA positively correlated with temperature . However, a decreasing trend of BSOA concentration with an increase in RH was observed during the sampling period, although a clear trend between ASOA and RH was not found. Based on the AIM Model calculation, we found that during the sampling period an increase in RH resulted in a decrease in the aerosol acidity and thus reduced the effect of acid-catalysis on BSOA formation. Size distributions of K+ and NH4+ present as an accumulation mode, in contrast to Ca2+ and Mg2+, which are mainly existed in coarse particles. SO42- and NO3- show a bimodal pattern. Dehydrated sugars, fossil fuel derived n-alkanes and PAHs presented unimode size distribution, whereas non-dehydrated sugars and plant wax derived n-alkanes showed bimodal pattern. Most of the determined BSOA are formed in the aerosol phase and enriched in the fine mode except for cis-pinonic acid, which is formed in the gas phase and subsequently partitioned into aerosol phase and thus presents a bimodal pattern with a major peak in the coarse mode.

  1. Detailed mass size distributions of elements and species, and aerosol chemical mass closure during fall 1999 at Gent, Belgium

    Science.gov (United States)

    Maenhaut, Willy; Cafmeyer, Jan; Dubtsov, Sergei; Chi, Xuguang

    2002-04-01

    A 10-stage microorifice uniform deposit impactor (MOUDI) and a 12-stage small deposit area low pressure impactor (SDI) were operated at Gent from 6 September to 30 October 1999. Thirty-four parallel samples (of typically 24 h) were collected. The MOUDI samples were analysed for the particulate mass (PM) by weighing, and for organic carbon (OC) and elemental carbon (EC) by a thermal-optical transmission technique. The SDI samples were analysed for 27 elements by PIXE. PM and OC exhibited typically a rather similar bimodal size distribution, with most of their mass in the submicrometer size range. EC was predominantly associated with fine particles, with maximum typically at around 0.2 μm equivalent aerodynamic diameter (EAD). Sulphur was also mainly in the fine size range, but with maximum at 0.5 μm EAD. Other elements with mainly a fine mode were V, Ni, As, Se and Pb. The crustal elements (Al, Si, Ti, Fe, Zr) exhibited mostly a unimodal coarse mode size distribution, with maximum at about 4 μm EAD. Other elements with mainly a coarse mode were Na, Mg, P, Ca, Cr, Mn, Cu, Ga and Sr. The elements K, Zn and Rb were generally bimodal. Aerosol chemical mass closure calculations indicated that organic aerosol and crustal matter were the major aerosol types in the supermicrometer size range, and that the dominant aerosol types in the submicrometer fraction were organic aerosol and sulphate. On average, 74% of the gravimetric PM was accounted for by the aerosol types considered.

  2. Detailed Chemical Characterization of Unresolved Complex Mixtures (UCM) inAtmospheric Organics: Insights into Emission Sources, Atmospheric Processing andSecondary Organic Aerosol Formation

    Science.gov (United States)

    Recent studies suggest that semivolatile organic compounds (SVOCs) are important precursors to secondary organic aerosol (SOA) in urban atmospheres. However, knowledge of the chemical composition of SVOCs is limited by current analytical techniques, which are typically unable to...

  3. Optical properties and chemical composition of aerosol particles at an urban location: An estimation of the aerosol mass scattering and absorption efficiencies

    Science.gov (United States)

    Titos, G.; Foyo-Moreno, I.; Lyamani, H.; Querol, X.; Alastuey, A.; Alados-Arboledas, L.

    2012-02-01

    We investigated aerosol optical properties, mass concentration and chemical composition over a 1 year period (from March 2006 to February 2007) at an urban site in Southern Spain (Granada, 37.18°N, 3.58°W, 680 m above sea level). Light-scattering and absorption measurements were performed using an integrating nephelometer and a MultiAngle Absorption Photometer (MAAP), respectively, with no aerosol size cut-off and without any conditioning of the sampled air. PM10 and PM1 (ambient air levels of atmospheric particulate matter finer than 10 and 1 microns) were collected with two high volume samplers, and the chemical composition was investigated for all samples. Relative humidity (RH) within the nephelometer was below 50% and the weighting of the filters was also at RH of 50%. PM10 and PM1 mass concentrations showed a mean value of 44 ± 19 μg/m3 and 15 ± 7 μg/m3, respectively. The mineral matter was the major constituent of the PM10-1 fraction (contributing more than 58%) whereas organic matter and elemental carbon (OM+EC) contributed the most to the PM1 fraction (around 43%). The absorption coefficient at 550 nm showed a mean value of 24 ± 9 Mm-1 and the scattering coefficient at 550 nm presented a mean value of 61 ± 25 Mm-1, typical of urban areas. Both the scattering and the absorption coefficients exhibited the highest values during winter and the lowest during summer, due to the increase in the anthropogenic contribution and the lower development of the convective mixing layer during winter. A very low mean value of the single scattering albedo of 0.71 ± 0.07 at 550 nm was calculated, suggesting that urban aerosols in this site contain a large fraction of absorbing material. Mass scattering and absorption efficiencies of PM10 particles exhibited larger values during winter and lower during summer, showing a similar trend to PM1 and opposite to PM10-1. This seasonality is therefore influenced by the variations on PM composition. In addition, the mass

  4. Sensitivity of thermal infrared sounders to the chemical and micro-physical properties of UTLS secondary sulphate aerosols

    Science.gov (United States)

    Sellitto, P.; Legras, B.

    2015-08-01

    Monitoring upper tropospheric-lower stratospheric (UTLS) secondary sulphate aerosols and their chemical and micro-physical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact to the UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR) satellite nadir observations to the chemical composition and the size distribution of idealized UTLS sulphate aerosol layers. The extinction properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the extinction of idealized aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with the main absorption peaks at 1170 and 905 cm-1. The dependence of the aerosol spectral signature to the sulphuric acid mixing ratio, and effective number concentration and radius, as well as the role of interferring parameters like the ozone, sulphur dioxide, carbon dioxide and ash absorption, and temperature and water vapour profile

  5. Sensitivity of thermal infrared sounders to the chemical and micro-physical properties of UTLS secondary sulphate aerosols

    Directory of Open Access Journals (Sweden)

    P. Sellitto

    2015-08-01

    Full Text Available Monitoring upper tropospheric-lower stratospheric (UTLS secondary sulphate aerosols and their chemical and micro-physical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact to the UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR satellite nadir observations to the chemical composition and the size distribution of idealized UTLS sulphate aerosol layers. The extinction properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas radiative transfer model, to estimate the impact of the extinction of idealized aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm−1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with the main absorption peaks at 1170 and 905 cm−1. The dependence of the aerosol spectral signature to the sulphuric acid mixing ratio, and effective number concentration and radius, as well as the role of interferring parameters like the ozone, sulphur dioxide, carbon dioxide and ash absorption, and temperature and

  6. Chemical composition of Titan's aerosols analogues characterized with a systematic pyrolysis-gas chromatography-mass spectrometry characterization

    Science.gov (United States)

    Szopa, Cyril; Raulin, Francois; Coll, Patrice; Cabane, Michel; GCMS Team

    2014-05-01

    The in situ chemical characterization of Titan's atmosphere was achieved in 2005 with two instruments present onboard the Huygens atmospheric probe : the Aerosol Collector and Pyrolyzer (ACP) devoted to collect and pyrolyse Titan's aerosols ; the Gas Chromatograph-Mass Spectrometer (GCMS) experiment devoted to analyze gases collected in the atmosphere or coming from the aerosols pyrolysis. The GCMS was developed by Hasso Niemann in the filiation of the quadrupole mass spectrometers he built for several former space missions. The main objectives were to : determine the concentration profile of the most abundant chemical species; seek for minor atmospheric organic species not detected with remote observations ; give a first view of the organic aerosols structure; characterize the condensed volatiles present at the surface (e.g. lakes) in case of survival of the probe to the landing impact. Taking into account for the potential complexity of the gaseous samples to be analyzed, it was decided to couple to the MS analyzer a gas chromatograph capable to separate volatile species from light inorganic molecules and noble gases, to organic compounds including aromatics. This was the first GCMS analyzer that worked in an extraterrestrial environment since the Viking missions on Mars. Even if the GCMS coupling mode did not provide any result of interest, it has been demonstrated to be functional during the Huygens descent. But, the direct MS analysis of the atmosphere, and the pyrolysis-MS analysis of aerosols allowed to make great discoveries which are still of primary importance to describe the Titan's lower atmosphere composition. This contribution aims at presenting this instrument that worked in the Titan's atmosphere, and summarizing the most important discoveries it allowed.

  7. Chemical and physical drivers of the evolution of organic aerosols over forests

    NARCIS (Netherlands)

    Janssen, R.H.H.

    2013-01-01

    Diurnal evolution of organic aerosol over boreal and tropical forests The first research question of this thesis is: how do local surface forcings and large-scale meteorological forcings shape the evolution of organic aerosol over the boreal and tropical forest? This question is de

  8. Comparison of Aerosol Optical Depth from GOES Aerosol and Smoke Product (GASP) and MODIS to AERONET AOD and IMPROVE PM2.5 Mass at Bondville, Illinois Stratified by Chemical Composition, RH, Particle Size, and Season

    Science.gov (United States)

    Green, M. C.; Kondragunta, S.; Ciren, P.

    2008-05-01

    The USEPA is interested in using satellite remote sensing data to estimate levels of PM2.5. Here we report on comparisons of aerosol optical depth (AOD) from GOES Aerosol and Smoke Product (GASP) and the Moderate Resolution Imaging Spectroradiometer (MODIS) to IMPROVE network PM2.5 mass and AErosol RObotic NETwork (AERONET) ground-based AOD. Before we compare GASP and MODIS AOD to PM2.5, we first evaluate satellite AOD using the ground-based AERONET measurements and how it varies by aerosol chemical composition and size distribution. We focus attention on the Bondville, Illinois site because there is collocated IMPROVE sampling and an AERONET site. GASP provides aerosol optical depth at 0.55 um using top of atmosphere visible channel radiance measured from GOES east and GOES west. Time resolution is typically every 30 minutes during daylight hours. MODIS provides typically once per day AOD for any given location. The IMPROVE sampler provides a 24-hour integrated sample of PM10 mass, and PM2.5 mass and elemental composition on a one day in three schedule. AERONET provides aerosol optical depth at multiple wavelengths and aerosol size distribution as well as other derived parameters such as Angstrom exponent from ground based daytime measurements. We stratified cases by RH group, major chemical component, size distribution, and season. GOES AOD correlated best with PM2.5 mass during periods with mainly small particles, moderate RH, and sulfate dominated aerosol. It correlated poorly when RH is very high or low, aerosol is primarily organic, and when coarse to fine mass ratio is high. GASP AOD also correlated best with AERONET AOD when particles are mainly fine, suggesting the aerosol model assumptions (e.g. size distribution) may need to be varied geographically for GASP to achieve better AOD results.

  9. Characteristics of aerosol size distributions and chemical compositions during wintertime pollution episodes in Beijing

    Science.gov (United States)

    Liu, Zirui; Hu, Bo; Zhang, Junke; Yu, Yangchun; Wang, Yuesi

    2016-02-01

    To characterize the features of particle pollution, continuous measurements of particle number size distributions and chemical compositions were performed at an urban site in Beijing in January 2013. The particle number and volume concentration from 14 nm to 1000 nm were (37.4 ± 15.3) × 103 cm- 3 and (85.2 ± 65.6) μm3 cm- 3, respectively. N-Ait (Aitken mode) particles dominated the number concentration, whereas N-Acc (accumulation mode) particles dominated the volume concentration. Submicron particles were generally characterized by a high content of organics and SO42 -, and a low level of NO3- and Cl-. Two types of pollution episodes were observed, characterized by the "explosive growth" (EXP) and "sustained growth" (SUS) of PM2.5. Fine particles greater than 100 nm dominated the volume concentration during the ends of these pollution episodes, shifting the maximum of the number size distribution from 60 nm to greater than 100 nm in a few hours (EXP) or a few days (SUS). Secondary transformation is the main reason for the pollution episodes; SO42 -, NO3- and NH4+ (SNA) accounted for approximately 42% (EXP) and greater than 60% (SUS) of the N-Acc particle mass increase. The size distributions of particulate organics and SNA varied on timescales of hours to days, the characteristics of which changed from bimodal to unimodal during the evolution of haze episodes. The accumulation mode (peaking at approximately 500-700 nm) was dominated by organics that appeared to be internally mixed with nitrate or sulfate. The sulfate was most likely formed via heterogeneous reactions, because the SOR was constant under dry conditions (RH 50%, suggesting an important contribution from heterogeneous reactions with abundant aerosol water under wet conditions. Finally, the correlations between [NO3-]/[SO42 -] and [NH4+]/[SO42 -] suggest that the homogenous reaction between HNO3 and NH3 dominated the formation of nitrate under conditions of lower aerosol acidity. Therefore

  10. Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006

    Science.gov (United States)

    Zalakeviciute, R.; Alexander, M. L.; Allwine, E.; Jimenez, J. L.; Jobson, B. T.; Molina, L. T.; Nemitz, E.; Pressley, S. N.; VanReken, T. M.; Ulbrich, I. M.; Velasco, E.; Lamb, B. K.

    2012-08-01

    As part of the MILAGRO 2006 field campaign, the exchange of atmospheric aerosols with the urban landscape was measured from a tall tower erected in a heavily populated neighborhood of Mexico City. Urban submicron aerosol fluxes were measured using an eddy covariance method with a quadrupole aerosol mass spectrometer during a two week period in March, 2006. Nitrate and ammonium aerosol concentrations were elevated at this location near the city center compared to measurements at other urban sites. Significant downward fluxes of nitrate aerosol, averaging -0.2 μg m-2 s-1, were measured during daytime. The urban surface was not a significant source of sulfate aerosols. The measurements also showed that primary organic aerosol fluxes, approximated by hydrocarbon-like organic aerosols (HOA), displayed diurnal patterns similar to CO2 fluxes and anthropogenic urban activities. Overall, 47% of submicron organic aerosol emissions were HOA, 35% were oxygenated (OOA) and 18% were associated with biomass burning (BBOA). Organic aerosol fluxes were bi-directional, but on average HOA fluxes were 0.1 μg m-2 s-1, OOA fluxes were -0.03 μg m-2 s-1, and BBOA fluxes were -0.03 μg m-2 s-1. After accounting for size differences (PM1 vs PM2.5) and using an estimate of the black carbon component, comparison of the flux measurements with the 2006 gridded emissions inventory of Mexico City, showed that the daily-averaged total PM emission rates were essentially identical for the emission inventory and the flux measurements. However, the emission inventory included dust and metal particulate contributions, which were not included in the flux measurements. As a result, it appears that the inventory underestimates overall PM emissions for this location.

  11. Aerosol physical and chemical properties retrieved from ground-based remote sensing measurements during heavy haze days in Beijing winter

    Science.gov (United States)

    Li, Z.; Gu, X.; Wang, L.; Li, D.; Xie, Y.; Li, K.; Dubovik, O.; Schuster, G.; Goloub, P.; Zhang, Y.; Li, L.; Ma, Y.; Xu, H.

    2013-10-01

    With the increase in economic development over the past thirty years, many large cities in eastern and southwestern China are experiencing increased haze events and atmospheric pollution, causing significant impacts on the regional environment and even climate. However, knowledge on the aerosol physical and chemical properties in heavy haze conditions is still insufficient. In this study, two winter heavy haze events in Beijing that occurred in 2011 and 2012 were selected and investigated by using the ground-based remote sensing measurements. We used a CIMEL CE318 sun-sky radiometer to retrieve haze aerosol optical, physical and chemical properties, including aerosol optical depth (AOD), size distribution, complex refractive indices and aerosol fractions identified as black carbon (BC), brown carbon (BrC), mineral dust (DU), ammonium sulfate-like (AS) components and aerosol water content (AW). The retrieval results from a total of five haze days showed that the aerosol loading and properties during the two winter haze events were comparable. Therefore, average heavy haze property parameters were drawn to present a research case for future studies. The average AOD is about 3.0 at 440 nm, and the Ångström exponent is 1.3 from 440 to 870 nm. The fine-mode AOD is 2.8 corresponding to a fine-mode fraction of 0.93. The coarse particles occupied a considerable volume fraction of the bimodal size distribution in winter haze events, with the mean particle radius of 0.21 and 2.9 μm for the fine and coarse modes respectively. The real part of the refractive indices exhibited a relatively flat spectral behavior with an average value of 1.48 from 440 to 1020 nm. The imaginary part showed spectral variation, with the value at 440 nm (about 0.013) higher than the other three wavelengths (about 0.008 at 675 nm). The aerosol composition retrieval results showed that volume fractions of BC, BrC, DU, AS and AW are 1, 2, 49, 15 and 33%, respectively, on average for the investigated

  12. Coupled aerosol-chemical modeling of UARS HNO3 and N2O5 measurements in the Arctic upper stratosphere

    Science.gov (United States)

    Bekki, S.; Chipperfield, M. P.; Pyle, J. A.; Remedios, J. J.; Smith, S. E.; Grainger, R. G.; Lambert, A.; Kumer, J. B.; Mergenthaler, J. L.

    1997-04-01

    Gas-phase photochemical models do not account for the formation of a secondary altitude HNO3 maximum in the upper stratosphere at high latitudes during winter, suggesting that some processes are missing in the currently accepted chemistry of reactive nitrogen species [Kawa et al, 1995]. Heterogeneous chemistry on aerosol particles had been discounted as the cause because the aerosol surface area is expected to be very low at these altitudes. We have coupled a sulphate aerosol microphysical model to a chemical transport model to investigate this model deficiency in the Arctic during January 1992. The aerosol model predicts the formation of small sulphate particles at 1100 K. Comparisons with cryogenic limb array etalon spectrometer (CLAES) HNO3 and improved stratospheric and mesospheric sounder (ISAMS) N2O5 observations show that the heterogeneous conversion of N2O5 to HNO3 on the modeled small sulphate particles can account for some of the unexpected features seen in Upper Atmosphere Research Satellite (UARS) observations.

  13. Improving the representation of secondary organic aerosol (SOA in the MOZART-4 global chemical transport model

    Directory of Open Access Journals (Sweden)

    A. Mahmud

    2012-12-01

    Full Text Available The secondary organic aerosol (SOA module in the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4 has been updated by replacing existing two-product (2p parameters with those obtained from two-product volatility basis set (2p-VBS fits, and by treating SOA formation from the following volatile organic compounds (VOCs: isoprene, propene and lumped alkenes. Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base-case and updated model versions. The base-case MOZART-4 predicted annual average SOA of 0.36 ± 0.50 μg m−3 in South America, 0.31 ± 0.38 μg m−3 in Indonesia, 0.09 ± 0.05 μg m−3 in the USA, and 0.12 ± 0.07 μg m−3 in Europe. Concentrations from the updated versions of the model showed a~marked increase in annual average SOA. Using the updated set of parameters alone (MZ4-v1 increased annual average SOA by ~8%, ~16%, ~56%, and ~108% from the base-case in South America, Indonesia, USA, and Europe, respectively. Treatment of additional parent VOCs (MZ4-v2 resulted in an even more dramatic increase of ~178–406% in annual average SOA for these regions over the base-case. The increases in predicted SOA concentrations further resulted in increases in corresponding SOA contributions to annual average total aerosol optical depth (AOD by <1% for MZ4-v1 and ~1–6% for MZ4-v2. Estimated global SOA production was ~6.6 Tg yr−1 and ~19.1 Tg yr−1 with corresponding burdens of ~0.24 Tg and ~0.59 Tg using MZ4-v1 and MZ4-v2, respectively. The SOA budgets predicted in the current study fall well within reported ranges for similar modeling studies, 6.7 to 96 Tg yr−1, but are lower than recently reported observationally-constrained values, 50 to 380 Tg yr−1. With MZ4-v2, simulated SOA concentrations at the surface were also in

  14. Improving the representation of secondary organic aerosol (SOA in the MOZART-4 global chemical transport model

    Directory of Open Access Journals (Sweden)

    A. Mahmud

    2013-07-01

    Full Text Available The secondary organic aerosol (SOA module in the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4 was updated by replacing existing two-product (2p parameters with those obtained from two-product volatility basis set (2p-VBS fits (MZ4-C1, and by treating SOA formation from the following additional volatile organic compounds (VOCs: isoprene, propene and lumped alkenes (MZ4-C2. Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base case and updated model simulations. Updates to the model resulted in significant increases in annual average SOA mass concentrations, particularly for the MZ4-C2 simulation in which the additional SOA precursor VOCs were treated. Annual average SOA concentrations predicted by the MZ4-C2 simulation were 1.00 ± 1.04 μg m−3 in South America, 1.57 ± 1.88 μg m−3 in Indonesia, 0.37 ± 0.27 μg m−3 in the USA, and 0.47 ± 0.29 μg m−3 in Europe with corresponding increases of 178, 406, 311 and 292% over the base-case simulation, respectively, primarily due to inclusion of isoprene. The increases in predicted SOA mass concentrations resulted in corresponding increases in SOA contributions to annual average total aerosol optical depth (AOD by ~ 1–6%. Estimated global SOA production was 5.8, 6.6 and 19.1 Tg yr−1 with corresponding burdens of 0.22, 0.24 and 0.59 Tg for the base-case, MZ4-C1 and MZ4-C2 simulations, respectively. The predicted SOA budgets fell well within reported ranges for comparable modeling studies, 6.7 to 96 Tg yr−1, but were lower than recently reported observationally constrained values, 50 to 380 Tg yr−1. For MZ4-C2, simulated SOA concentrations at the surface also were in reasonable agreement with comparable modeling studies and observations. Total organic aerosol (OA mass concentrations at the surface, however, were slightly over-predicted in Europe, Amazonian

  15. Improving the representation of secondary organic aerosol (SOA) in the MOZART-4 global chemical transport model

    Science.gov (United States)

    Mahmud, A.; Barsanti, K.

    2013-07-01

    The secondary organic aerosol (SOA) module in the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) was updated by replacing existing two-product (2p) parameters with those obtained from two-product volatility basis set (2p-VBS) fits (MZ4-C1), and by treating SOA formation from the following additional volatile organic compounds (VOCs): isoprene, propene and lumped alkenes (MZ4-C2). Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base case and updated model simulations. Updates to the model resulted in significant increases in annual average SOA mass concentrations, particularly for the MZ4-C2 simulation in which the additional SOA precursor VOCs were treated. Annual average SOA concentrations predicted by the MZ4-C2 simulation were 1.00 ± 1.04 μg m-3 in South America, 1.57 ± 1.88 μg m-3 in Indonesia, 0.37 ± 0.27 μg m-3 in the USA, and 0.47 ± 0.29 μg m-3 in Europe with corresponding increases of 178, 406, 311 and 292% over the base-case simulation, respectively, primarily due to inclusion of isoprene. The increases in predicted SOA mass concentrations resulted in corresponding increases in SOA contributions to annual average total aerosol optical depth (AOD) by ~ 1-6%. Estimated global SOA production was 5.8, 6.6 and 19.1 Tg yr-1 with corresponding burdens of 0.22, 0.24 and 0.59 Tg for the base-case, MZ4-C1 and MZ4-C2 simulations, respectively. The predicted SOA budgets fell well within reported ranges for comparable modeling studies, 6.7 to 96 Tg yr-1, but were lower than recently reported observationally constrained values, 50 to 380 Tg yr-1. For MZ4-C2, simulated SOA concentrations at the surface also were in reasonable agreement with comparable modeling studies and observations. Total organic aerosol (OA) mass concentrations at the surface, however, were slightly over-predicted in Europe, Amazonian regions and Malaysian Borneo

  16. Chemical characterization of organosulfates in secondary organic aerosol derived from the photooxidation of alkanes

    Science.gov (United States)

    Riva, Matthieu; Da Silva Barbosa, Thais; Lin, Ying-Hsuan; Stone, Elizabeth A.; Gold, Avram; Surratt, Jason D.

    2016-09-01

    We report the formation of aliphatic organosulfates (OSs) in secondary organic aerosol (SOA) from the photooxidation of C10-C12 alkanes. The results complement those from our laboratories reporting the formation of OSs and sulfonates from gas-phase oxidation of polycyclic aromatic hydrocarbons (PAHs). Both studies strongly support the formation of OSs from the gas-phase oxidation of anthropogenic precursors, as hypothesized on the basis of recent field studies in which aromatic and aliphatic OSs were detected in fine aerosol collected from several major urban locations. In this study, dodecane, cyclodecane and decalin, considered to be important SOA precursors in urban areas, were photochemically oxidized in an outdoor smog chamber in the presence of either non-acidified or acidified ammonium sulfate seed aerosol. Effects of acidity and relative humidity on OS formation were examined. Aerosols collected from all experiments were characterized by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS). Most of the OSs identified could be explained by formation of gaseous epoxide precursors with subsequent acid-catalyzed reactive uptake onto sulfate aerosol and/or heterogeneous reactions of hydroperoxides. The OSs identified here were also observed and quantified in fine urban aerosol samples collected in Lahore, Pakistan, and Pasadena, CA, USA. Several OSs identified from the photooxidation of decalin and cyclodecane are isobars of known monoterpene organosulfates, and thus care must be taken in the analysis of alkane-derived organosulfates in urban aerosol.

  17. Aerosol chemical composition and light scattering during a winter season in Beijing

    Science.gov (United States)

    Tao, Jun; Zhang, Leiming; Gao, Jian; Wang, Han; Chai, Faihe; Wang, Shulan

    2015-06-01

    To evaluate PM2.5 contributions to light scattering under different air pollution levels, PM2.5 and its major chemical components, PM10, size-segregated water-soluble ions, and aerosol scattering coefficient (bsp) under dry conditions were measured at an urban site in Beijing in January 2013 when heavy pollution events frequently occurred. Measurements were categorized into three pollution levels including heavy-polluted (Air Quality Index (AQI) ≥ 200), light-polluted (200 > AQI ≥ 100) and clean periods (AQI 0.95) during the different pollution levels. The mass scattering efficiency (MSE) of PM2.5 was 4.9 m2 g-1 during the heavy-polluted period, which was higher than those during the light-polluted (4.3 m2 g-1) and clean periods (3.6 m2 g-1). To further evaluate the impact of individual chemical components of PM2.5 on light scattering, a multiple linear regression equation of measured bsp against the mass concentration of (NH4)2SO4, NH4NO3, Organic Matter (OM), EC, Fine Soil (FS), Coarse Matter (CM) and Other chemical compounds were performed. (NH4)2SO4, NH4NO3 and OM were the dominant species contributing to bsp under both dry and ambient conditions. OM contributed more to bsp than the sum of (NH4)2SO4 and NH4NO3 did under the dry condition during all the pollution periods and this was also the case under the ambient condition during the light-polluted and clean periods. However, the total contributions of (NH4)2SO4 and NH4NO3 to bsp under the ambient condition was 55%, much more than the 29% contribution from OM during the heavy-polluted period. High (NH4)2SO4 and NH4NO3 concentrations and their hygroscopicity were the main reasons causing visibility degradation during the heavy-polluted period, and the effect can be enhanced under high RH conditions.

  18. Chemical composition, sources, and processes of urban aerosols during summertime in northwest China: insights from high-resolution aerosol mass spectrometry

    Science.gov (United States)

    Xu, J.; Zhang, Q.; Chen, M.; Ge, X.; Ren, J.; Qin, D.

    2014-12-01

    An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed along with a scanning mobility particle sizer (SMPS) and a multi-angle absorption photometer (MAAP) to measure the temporal variations of the mass loading, chemical composition, and size distribution of submicron particulate matter (PM1) in Lanzhou, northwest China, during 11 July-7 August 2012. The average (PM1 mass concentration including non-refractory (PM1 (NR-(PM1) measured by HR-ToF-AMS and black carbon (BC) measured by MAAP during this study was 24.5 μg m-3 (ranging from 0.86 to 105 μg m-3), with a mean composition consisting of 47% organics, 16% sulfate, 12% BC, 11% ammonium, 10% nitrate, and 4% chloride. Organic aerosol (OA) on average consisted of 70% carbon, 21% oxygen, 8% hydrogen, and 1% nitrogen, with the average oxygen-to-carbon ratio (O / C) of 0.33 and organic mass-to-carbon ratio (OM / OC) of 1.58. Positive matrix factorization (PMF) of the high-resolution organic mass spectra identified four distinct factors which represent, respectively, two primary OA (POA) emission sources (traffic and food cooking) and two secondary OA (SOA) types - a fresher, semi-volatile oxygenated OA (SV-OOA) and a more aged, low-volatility oxygenated OA (LV-OOA). Traffic-related hydrocarbon-like OA (HOA) and BC displayed distinct diurnal patterns, both with peak at ~ 07:00-11:00 (BJT: UTC +8), corresponding to the morning rush hours, while cooking-emission related OA (COA) peaked during three meal periods. The diurnal profiles of sulfate and LV-OOA displayed a broad peak between ~ 07:00 and 15:00, while those of nitrate, ammonium, and SV-OOA showed a narrower peak between ~ 08:00-13:00. The later morning and early afternoon maximum in the diurnal profiles of secondary aerosol species was likely caused by downward mixing of pollutants aloft, which were likely produced in the residual layer decoupled from the boundary layer during nighttime. The mass spectrum of SV-OOA was

  19. Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6

    Directory of Open Access Journals (Sweden)

    M. Kamphus

    2009-07-01

    Full Text Available Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l. during the Cloud and Aerosol Characterization Experiment (CLACE 6 in February and March 2007. During mixed phase cloud events ice crystals from 5 μm up to 20 μm were separated from large ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI. During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The resulting ice and droplet residues (IR and DR were analyzed for size and composition by two single particle mass spectrometers: a custom-built Single Particle Laser-Ablation Time-of-Flight Mass Spectrometer (SPLAT and a commercial Aerosol Time of Flight Mass Spectrometer (ATOFMS, TSI Model 3800. During CLACE 6 the SPLAT instrument characterized 355 individual ice residues that produced a mass spectrum for at least one polarity and the ATOFMS measured 152 particles. The mass spectra were binned in classes, based on the combination of dominating substances, such as mineral dust, sulfate, potassium and elemental carbon or organic material. The derived chemical information from the ice residues is compared to the JFJ ambient aerosol that was sampled while the measurement station was out of clouds (several thousand particles analyzed by SPLAT and ATOFMS and to the composition of the residues of supercooled cloud droplets (SPLAT: 162 cloud droplet residues analyzed, ATOFMS: 1094. The measurements showed that mineral dust particles were strongly enhanced in the ice particle residues. 57% of the SPLAT spectra from ice residues were dominated by signatures from mineral compounds, and 78% of the ATOFMS spectra. Sulfate and nitrate containing particles were strongly

  20. Seasonal characterization of submicron aerosol chemical composition and organic aerosol sources in the southeastern United States: Atlanta, Georgia and Look Rock, Tennessee

    Directory of Open Access Journals (Sweden)

    S. H. Budisulistiorini

    2015-08-01

    Full Text Available A yearlong near-real-time characterization of non-refractory submicron aerosol (NR-PM1 was conducted at an urban (Atlanta, Georgia and rural (Look Rock, Tennessee site in the southeastern US using the Aerodyne aerosol chemical speciation monitor (ACSM collocated with established air-monitoring network measurements. Seasonal variations in organic aerosol (OA and inorganic aerosol species are attributed to meteorological conditions as well as anthropogenic and biogenic emissions in this region. The highest concentrations of NR-PM1 were observed during winter and fall seasons at the urban site and during spring and summer at the rural site. Across all seasons and at both sites, NR-PM1 was composed largely of OA (50–76 % and inorganic sulfate (12–31 %. Six distinct OA sources were resolved by positive matrix factorization applied to the ACSM organic mass spectral data collected from the two sites over the one year of near-continuous measurements at each site: hydrocarbon-like OA (HOA, biomass burning OA (BBOA, semi-volatile oxygenated OA (SV-OOA, low-volatility oxygenated OA (OOA, isoprene-derived epoxydiol (IEPOX OA (IEPOX-OA, and 91Fac OA (a factor dominated by a distinct ion at m/z 91 fragment ion previously observed in biogenic influenced areas. LV-OOA was observed throughout the year at both sites and contributed 30–66 % of total OA mass. HOA was also observed during the entire year only at the urban site (15–24 % of OA mass. BBOA (15–33 % of OA mass was observed during winter and fall, likely dominated by local residential wood burning emission. Although SV-OOA contributes quite significantly (∼ 27 %, it was observed only at the urban site during colder seasons. IEPOX-OA was a major component (27–41 % of OA at both sites, particularly in spring and summer. An ion fragment at m/z 75 is proposed as an additional marker for IEPOX-OA, as it is shown to correlate well with the m/z 82 ion shown to be associated with the aerosol mass

  1. PM2.5 Chemical Compositions and Aerosol Optical Properties in Beijing during the Late Fall

    Directory of Open Access Journals (Sweden)

    Huanbo Wang

    2015-01-01

    Full Text Available Daily PM2.5 mass concentrations and chemical compositions together with the aerosol optical properties were measured from 8–28 November 2011 in Beijing. PM2.5 mass concentration varied from 15.6–237.5 μg∙m−3 and showed a mean value of 111.2 ± 73.4 μg∙m−3. Organic matter, NH4NO3 and (NH42SO4 were the major constituents of PM2.5, accounting for 39.4%, 15.4%, and 14.9% of the total mass, respectively, while fine soil, chloride salt, and elemental carbon together accounted for 27.7%. Daily scattering and absorption coefficients (σsc and σap were in the range of 31.1–667 Mm−1 and 8.24–158.0 Mm−1, with mean values of 270 ± 200 Mm−1 and 74.3 ± 43.4 Mm−1. Significant increases in σsc and σap were observed during the pollution accumulation episodes. The revised IMPROVE algorithm was applied to estimate the extinction coefficient (bext. On average, organic matter was the largest contributor, accounting for 44.6% of bext, while (NH42SO4, NH4NO3, elemental carbon, and fine soil accounted for 16.3% 18.0%, 18.6%, and 2.34% of bext, respectively. Nevertheless, the contributions of (NH42SO4 and NH4NO3 were significantly higher during the heavy pollution periods than those on clean days. Typical pollution episodes were also explored, and it has been characterized that secondary formation of inorganic compounds is more important than carbonaceous pollution for visibility impairment in Beijing.

  2. Near Real-Time, Microchip Assay of Aerosol Chemical Composition Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A compact, autonomous and rugged instrument to measure the concentration of inorganic ions, and possibly organic acids, in atmospheric aerosols is proposed. This...

  3. Analysis of the chemical and physical properties of combustion aerosols: State of the art.

    Science.gov (United States)

    The impact of combustion aerosols on human health is well documented byepidemiological studies, however the effect of low concentrations of ultrafineparticles on the human lung are not yet fully understood. With the advent ofnovel measurement technologies for simultaneous charact...

  4. In Situ Measurement of the Infrared Spectral Extinction for Various Chemical, Biological, and Background Aerosols

    Science.gov (United States)

    2003-09-01

    11 Figure 10. Measured extinction for agglomerated Cab-O-sil aerogel at various...Transmitted light was coupled to the interferometer with a gold -surfaced f/4 off-axis parabola. Because spectra derived from aerosols are devoid of any... aerogel ” is extremely amorphous (94% of its volume is air) and is sometimes used as a fluidizer to improve aerosol dissemination efficiencies. As a

  5. The Statistical Evolution of Multiple Generations of Oxidation Products in the Photochemical Aging of Chemically Reduced Organic Aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Kevin R.; Smith, Jared D.; Kessler, Sean; Kroll, Jesse H.

    2011-10-03

    The heterogeneous reaction of hydroxyl radicals (OH) with squalane and bis(2-ethylhexyl) sebacate (BES) particles are used as model systems to examine how distributions of reactionproducts evolve during the oxidation of chemically reduced organic aerosol. A kinetic model of multigenerational chemistry, which is compared to previously measured (squalane) and new(BES) experimental data, reveals that it is the statistical mixtures of different generations of oxidation products that control the average particle mass and elemental composition during thereaction. The model suggests that more highly oxidized reaction products, although initially formed with low probability, play a large role in the production of gas phase reaction products.In general, these results highlight the importance of considering atmospheric oxidation as a statistical process, further suggesting that the underlying distribution of molecules could playimportant roles in aerosol formation as well as in the evolution of key physicochemical properties such as volatility and hygroscopicity.

  6. MORPHOLOGY OF BLACK CARBON AEROSOLS AND UBIQUITY OF 50-NANOMETER BLACK CARBON AEROSOLS IN THE ATMOSPHERE

    Institute of Scientific and Technical Information of China (English)

    Fengfu Fu; Liangjun Xu; Wei Ye; Yiquan Chen; Mingyu Jiang; Xueqin Xu

    2006-01-01

    Different-sized aerosols were collected by an Andersen air sampler to observe the detailed morphology of the black carbon (BC) aerosols which were separated chemically from the other accompanying aerosols, using a Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDX). The results indicate that most BC aerosols are spherical particles of about 50 nm in diameter and with a homogeneous surface. Results also show that these particles aggregate with other aerosols or with themselves to form larger agglomerates in the micrometer range. The shape of these 50-nm BC spherical particles was found to be very similar to that of BC particles released from petroleum-powered vehicular internal combustion engines. These spherical BC particles were shown to be different from the previously reported fullerenes found using Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS).

  7. Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006

    Directory of Open Access Journals (Sweden)

    R. Zalakeviciute

    2012-08-01

    Full Text Available As part of the MILAGRO 2006 field campaign, the exchange of atmospheric aerosols with the urban landscape was measured from a tall tower erected in a heavily populated neighborhood of Mexico City. Urban submicron aerosol fluxes were measured using an eddy covariance method with a quadrupole aerosol mass spectrometer during a two week period in March, 2006. Nitrate and ammonium aerosol concentrations were elevated at this location near the city center compared to measurements at other urban sites. Significant downward fluxes of nitrate aerosol, averaging −0.2 μg m−2 s−1, were measured during daytime. The urban surface was not a significant source of sulfate aerosols. The measurements also showed that primary organic aerosol fluxes, approximated by hydrocarbon-like organic aerosols (HOA, displayed diurnal patterns similar to CO2 fluxes and anthropogenic urban activities. Overall, 47% of submicron organic aerosol emissions were HOA, 35% were oxygenated (OOA and 18% were associated with biomass burning (BBOA. Organic aerosol fluxes were bi-directional, but on average HOA fluxes were 0.1 μg m−2 s−1, OOA fluxes were −0.03 μg m−2 s−1, and BBOA fluxes were −0.03 μg m−2 s−1. After accounting for size differences (PM1 vs PM2.5 and using an estimate of the black carbon component, comparison of the flux measurements with the 2006 gridded emissions inventory of Mexico City, showed that the daily-averaged total PM emission rates were essentially identical for the emission inventory and the flux measurements. However, the emission inventory included dust and metal particulate contributions, which were not included in the flux measurements. As a result, it appears that the inventory underestimates overall PM emissions for this location.

  8. Exploring Atmospheric Aqueous Chemistry (and Secondary Organic Aerosol Formation) through OH Radical Oxidation Experiments, Droplet Evaporation and Chemical Modeling

    Science.gov (United States)

    Turpin, B. J.; Kirkland, J. R.; Lim, Y. B.; Ortiz-Montalvo, D. L.; Sullivan, A.; Häkkinen, S.; Schwier, A. N.; Tan, Y.; McNeill, V. F.; Collett, J. L.; Skog, K.; Keutsch, F. N.; Sareen, N.; Carlton, A. G.; Decesari, S.; Facchini, C.

    2013-12-01

    Gas phase photochemistry fragments and oxidizes organic emissions, making water-soluble organics ubiquitous in the atmosphere. My group and others have found that several water-soluble compounds react further in the aqueous phase forming low volatility products under atmospherically-relevant conditions (i.e., in clouds, fogs and wet aerosols). Thus, secondary organic aerosol can form as a result of gas followed by aqueous chemistry (aqSOA). We have used aqueous OH radical oxidation experiments coupled with product analysis and chemical modeling to validate and refine the aqueous chemistry of glyoxal, methylglyoxal, glycolaldehyde, and acetic acid. The resulting chemical model has provided insights into the differences between oxidation chemistry in clouds and in wet aerosols. Further, we conducted droplet evaporation experiments to characterize the volatility of the products. Most recently, we have conducted aqueous OH radical oxidation experiments with ambient mixtures of water-soluble gases to identify additional atmospherically-important precursors and products. Specifically, we scrubbed water-soluble gases from the ambient air in the Po Valley, Italy using four mist chambers in parallel, operating at 25-30 L min-1. Aqueous OH radical oxidation experiments and control experiments were conducted with these mixtures (total organic carbon ≈ 100 μM-C). OH radicals (3.5E-2 μM [OH] s-1) were generated by photolyzing H2O2. Precursors and products were characterized using electrospray ionization mass spectrometry (ESI-MS), ion chromatography (IC), IC-ESI-MS, and ultra high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Chemical modeling suggests that organic acids (e.g., oxalate, pyruvate, glycolate) are major products of OH radical oxidation at cloud-relevant concentrations, whereas organic radical - radical reactions result in the formation of oligomers in wet aerosols. Products of cloud chemistry and droplet evaporation have

  9. Electron microscopic study on aerosol-assisted synthesis of aluminum organophosphonates using flexible colloidal PS-b-PEO templates.

    Science.gov (United States)

    Kimura, Tatsuo; Yamauchi, Yusuke

    2012-09-04

    A wide variety of synthetic approaches from homogeneous precursor solutions have so far been developed for precise structural design of materials in multiscale. In organic templating approaches for porous materials design, we have recently developed a new approach to fabricate colloidal polystyrene-block-poly(oxyethylene) (PS-b-PEO) templated large pores that can be controlled in thick films of aluminum organophosphonate (AOP). In this study, we extended this approach using colloidal PS-b-PEO aggregates to aerosol-assisted synthesis for the fabrication of spherical particles. Structural variations (morphology and porous structure) depended on the synthetic conditions, which were mainly investigated by using electron microscopies (SEM and TEM). In addition to the insight on the colloidal PS-b-PEO templating of spherical pores in AOP spheres, it was found that colloidal PS-b-PEO aggregates were flexible for further design of pore shape that was strongly affected by external morphology. In this context, we proposed this method as flexible colloidal PS-b-PEO templating to fabricate unusual macroporous structures during morphological control from precursor solutions containing colloidal PS-b-PEO aggregates. The insights will be promising for precise construction of unique devices using porous materials templated by colloidal organic aggregates. In addition, we found a useful water adsorption-desorption behavior over the macroporous AOP bulky powders when the macropores were connected through large pores, which is also significant for future development of AOP-based porous materials.

  10. Thickness dependence of electrical properties of PZT films deposited on metal substrates by laser-assisted aerosol deposition.

    Science.gov (United States)

    Baba, S; Tsuda, H; Akedo, J

    2008-05-01

    Dependence of electrical properties-dielectric, ferroelectric, and piezoelectric properties-on film thickness was studied for lead-zirconate titanate (PZT) thick films directly deposited onto stainless-steel (SUS) substrates in actuator devices by using a carbon dioxide (CO(2) ), laser assisted aerosol deposition technique. Optical spectroscopic analysis data and laser irradiation experiments revealed that absorption at a given wavelength by the film increased with increasing film thickness. Dielectric constant epsilon, remanent polarization value P(r), and coercive field strength E(c) of PZT films directly deposited onto a SUS-based piezoelectric actuator substrate annealed by CO(2) laser irradiation at 850 degrees C improved with increasing film thickness, and for films thicker than 25 microm, epsilon 800, P(r) 40 microC/cm(2), and E(c) 45 kV/cm. In contrast, the displacement of the SUS-based actuator with the laser-annealed PZT thick film decreased with increasing film thickness.

  11. GEM-AQ/EC, an on-line global multi-scale chemical weather modelling system: model development and evaluation of global aerosol climatology

    Directory of Open Access Journals (Sweden)

    S. L. Gong

    2012-09-01

    Full Text Available A global air quality modeling system GEM-AQ/EC was developed by implementing tropospheric chemistry and aerosol processes on-line into the Global Environmental Multiscale weather prediction model – GEM. Due to the multi-scale features of the GEM, the integrated model, GEM-AQ/EC, is able to investigate chemical weather at scales from global to urban domains. The current chemical mechanism is comprised of 50 gas-phase species, 116 chemical and 19 photolysis reactions, and is complemented by a sectional aerosol module CAM (The Canadian Aerosol Module with 5 aerosols types: sulphate, black carbon, organic carbon, sea-salt and soil dust. Monthly emission inventories of black carbon and organic carbon from boreal and temperate vegetation fires were assembled using the most reliable areas burned datasets by countries, from statistical databases and derived from remote sensing products of 1995–2004. The model was run for ten years from from 1995–2004 with re-analyzed meteorology on a global uniform 1° × 1° horizontal resolution domain and 28 hybrid levels extending up to 10 hPa. The simulating results were compared with various observations including surface network around the globe and satellite data. Regional features of global aerosols are reasonably captured including emission, surface concentrations and aerosol optical depth. For various types of aerosols, satisfactory correlations were achieved between modeled and observed with some degree of systematic bias possibly due to large uncertainties in the emissions used in this study. A global distribution of natural aerosol contributions to the total aerosols is obtained and compared with observations.

  12. GEM-AQ/EC, an on-line global multiscale chemical weather modelling system: model development and evaluations of global aerosol climatology

    Directory of Open Access Journals (Sweden)

    S. L. Gong

    2012-04-01

    Full Text Available A global air quality modeling system GEM-AQ/EC was developed by implementing tropospheric chemistry and aerosol processes on-line into the Global Environmental Multiscale weather prediction model – GEM. Due to the multi-scale features of the GEM, the integrated model, GEM-AQ/EC, is able to investigate chemical weather at scales from global to urban domains. The current chemical mechanism is comprised of 50 gas-phase species, 116 chemical and 19 photolysis reactions, and is complemented by a sectional aerosol module CAM (The Canadian Aerosol Module with 5 aerosols types: sulphate, black carbon, organic carbon, sea-salt and soil dust. Monthly emission inventories of black carbon and organic carbon from boreal and temperate vegetation fires were assembled using the most reliable areas burned datasets by countries, from statistical databases and derived from remote sensing products of 1995–2004. The model was run for ten years from from 1995–2004 with re-analyzed meteorology on a global uniform 1 × 1° horizontal resolution domain and 28 hybrid levels extending up to 10 hPa. The simulating results were compared with various observations including surface network around the globe and satellite data. Regional features of global aerosols are reasonably captured including emission, surface concentrations and aerosol optical depth. For various types of aerosols, satisfactory correlations were achieved between modeled and observed with some degree of systematic bias possibly due to large uncertainties in the emissions used in this study. A global distribution of natural aerosol contributions to the total aerosols is obtained and compared with observations.

  13. Experimental Measurements of the Effects of Photo-chemical Oxidation on Aerosol Emissions in Aircraft Exhaust

    Science.gov (United States)

    Miracolo, M. A.; Presto, A. A.; Hennigan, C. J.; Nguyen, N.; Ranjan, M.; Reeder, A.; Lipsky, E.; Donahue, N. M.; Robinson, A. L.

    2009-12-01

    Many military and commercial airfields are located in non-attainment areas for particulate matter (PM2.5), but the contribution of emissions from in-use aircraft to local and regional PM2.5 concentrations is uncertain. In collaboration with the Pennsylvania Air National Guard 171st Air Refueling Wing, the Carnegie Mellon University (CMU) Mobile Laboratory was deployed to measure fresh and aged emissions from a CFM56-2B1 gas-turbine engine mounted on a KC-135 Stratotanker airframe. The CFM-56 family of engine powers many different types of military and civilian aircraft, including the Boeing 737 and several Airbus models. It is one of the most widely deployed models of engines in the world. The goal of this work was to measure the gas-particle partitioning of the fresh emissions at atmospherically relevant conditions and to investigate the effect of atmospheric oxidation on aerosol loadings as the emissions age. Emissions were sampled from an inlet installed one meter downstream of the engine exit plane and transferred into a portable smog chamber via a heated inlet line. Separate experiments were conducted at different engine loads ranging from ground idle to take-off rated thrust. During each experiment, some diluted exhaust was added to the chamber and the volatility of the fresh emissions was then characterized using a thermodenuder. After this characterization, the chamber was exposed to either ambient sunlight or UV lights to initiate photochemical oxidation, which produced secondary aerosol and ozone. A suite of gas and particle-phase instrumentation was used to characterize the evolution of the gas and particle-phase emissions, including an aerosol mass spectrometer (AMS) to measure particle size and composition distributions. Fresh emissions of fine particles varied with engine load with peak emission factors at low and high loads. At high engine loads, the fresh emissions were dominated by black carbon; at low loads volatile organic carbon emissions were

  14. Chemical characteristics of organic aerosols in Algiers city area: influence of a fat manufacture plant

    Science.gov (United States)

    Yassaa, Noureddine; Meklati, Brahim Youcef; Cecinato, Angelo

    Total concentrations and homologue distributions of organic fraction constituents have been determined in particulate matter emitted from different units of a fat manufacturer (i.e. oils refining and conditioning plants, and production and conditioning units of a soap industry) located in Algiers area, as well as in atmospheric aerosols. In particular n-alkanes, n-alkanoic and n-alkenoic acids, n-alkan-2-ones and polycyclic aromatic hydrocarbons (PAH) were investigated. Organic aerosol contents varied broadly among the plant units, depending upon nature of the manufactured products. The percent composition of all classes of compounds investigated in ambient atmosphere was similar to those observed indoor at industrial plant units. Organic acids, n-alkanoic as well as n-alkenoic, appeared by far the most abundant organic constituents of aerosols, both indoor and outdoor, ranging from 7.7 to 19.8 and from 12.7 to 17.1 μg m -3, respectively. The huge occurrence of acids and n-alkanes in ambient aerosols was consistent with their high levels present in oil and fat materials. Among minor components of aerosols, n-alkan-2-ones and PAH, seemed to be related to thermally induced ageing and direct combustion of raw organic material used for oil and soap production.

  15. Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations.

    Science.gov (United States)

    Ben Salah, Mehdi; Hallé, Stéphane; Tuduri, Ludovic

    2016-01-01

    Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies.

  16. Optical and chemical characterization of aerosols emitted from coal, heavy and light fuel oil, and small-scale wood combustion.

    Science.gov (United States)

    Frey, Anna K; Saarnio, Karri; Lamberg, Heikki; Mylläri, Fanni; Karjalainen, Panu; Teinilä, Kimmo; Carbone, Samara; Tissari, Jarkko; Niemelä, Ville; Häyrinen, Anna; Rautiainen, Jani; Kytömäki, Jorma; Artaxo, Paulo; Virkkula, Aki; Pirjola, Liisa; Rönkkö, Topi; Keskinen, Jorma; Jokiniemi, Jorma; Hillamo, Risto

    2014-01-01

    Particle emissions affect radiative forcing in the atmosphere. Therefore, it is essential to know the physical and chemical characteristics of them. This work studied the chemical, physical, and optical characteristics of particle emissions from small-scale wood combustion, coal combustion of a heating and power plant, as well as heavy and light fuel oil combustion at a district heating station. Fine particle (PM1) emissions were the highest in wood combustion with a high fraction of absorbing material. The emissions were lowest from coal combustion mostly because of efficient cleaning techniques used at the power plant. The chemical composition of aerosols from coal and oil combustion included mostly ions and trace elements with a rather low fraction of absorbing material. The single scattering albedo and aerosol forcing efficiency showed that primary particles emitted from wood combustion and some cases of oil combustion would have a clear climate warming effect even over dark earth surfaces. Instead, coal combustion particle emissions had a cooling effect. Secondary processes in the atmosphere will further change the radiative properties of these emissions but are not considered in this study.

  17. Special issue: Chemical characterization of secondary organic aerosol - Dedication to Professor Magda Claeys

    Science.gov (United States)

    Surratt, Jason D.; Szmigielski, Rafal; Faye McNeill, V.

    2016-04-01

    Atmospheric aerosols are suspensions of liquid and solid particles that have diameters ranging from a few nanometers to several micrometers (μm). Atmospheric fine particulate matter (PM2.5, aerosols with aerodynamic diameters of 2.5 μm or less) are especially important since they can adversely affect air quality and human health as well as play a critical role in Earth's climate system. In terms of aerosol climate effects, PM2.5 can directly affect climate by scattering or absorbing incoming solar radiation or indirectly by acting as nuclei on which cloud droplets and ice particles form. As a result, a better understanding of processes that determine the formation and sinks of PM2.5 is needed for developing effective policies that improve air quality and public health as well as to accurately predict the response of the climate system due to changes in anthropogenic emissions.

  18. Chemical and statistical interpretation of sized aerosol particles collected at an urban site in Thessaloniki, Greece.

    Science.gov (United States)

    Tsitouridou, Roxani; Papazova, Petia; Simeonova, Pavlina; Simeonov, Vasil

    2013-01-01

    The size distribution of aerosol particles (PM0.015-PM18) in relation to their soluble inorganic species and total water soluble organic compounds (WSOC) was investigated at an urban site of Thessaloniki, Northern Greece. The sampling period was from February to July 2007. The determined compounds were compared with mass concentrations of the PM fractions for nano (N: 0.015 pollution were identified and an attempt is made to find patterns of similarity between the different sized aerosols and the seasons of monitoring. It was proven that several major latent factors are responsible for the data structure despite the size of the aerosols - mineral (soil) dust, sea sprays, secondary emissions, combustion sources and industrial impact. The seasonal separation proved to be not very specific.

  19. Chemical characterization of fine organic aerosol for source apportionment at Monterrey, Mexico

    Directory of Open Access Journals (Sweden)

    Y. Mancilla

    2015-07-01

    events. Finally, source attribution results obtained using the CMB model indicate that emissions from motor vehicle exhausts are the most important, accounting for the 64 % of the PM2.5. The vegetative detritus and biomass burning had the smallest contribution (2.2 % of the PM2.5. To our knowledge, this is the second study to explore the broad chemical characterization of fine organic aerosol in Mexico and the first for the MMA.

  20. Chemical Aging and Cloud Condensation Nuclei Activity of Biomass Burning Aerosol Proxies in the Presence of OH Radicals

    Science.gov (United States)

    Slade, Jonathan H., Jr.

    Biomass burning aerosol (BBA) can adversely impact regional and global air quality and represents a significant source of organic aerosol (OA) to the atmosphere that can affect climate. Aerosol particles can alter the transfer of radiation in earth's atmosphere directly by scattering and absorbing radiation or indirectly via cloud formation. Gas-to-particle, also termed heterogeneous, oxidation reactions can significantly alter the particle's physical and chemical properties. In turn, this can lead to the degradation of biomolecular markers for air quality-related aerosol source apportionment studies, the particles' lifetime, and modify the particles' abilities to serve as cloud condensation nuclei (CCN). However, the rates, mechanisms, and conditions by which these multiphase oxidation reactions occur and influence the CCN activity of OA is not well understood. The work presented here aims to determine the reactivity and products from the interaction of BBA surrogate-particles and trace gas-phase oxidants and to link the effects of OA chemical aging on the particles' ability to nucleate clouds. The reactive uptake of OH by BBA surrogate-substrates and particles, including levoglucosan, nitroguaiacol, abietic acid, and methyl-nitrocatechol, was determined as a function of both OH concentration and relative humidity (RH) using chemical ionization mass spectrometry coupled to various flow reactors. OH reactive uptake decreased with increasing OH concentration, indicative of OH adsorption followed by reaction. OH oxidation led to significant volatilization, i.e. mass loss of the organic material, as determined by application of high resolution proton transfer reaction time-of-flight mass spectrometry. Volatilized reaction products were identified, providing mechanistic insight of the chemical pathways in the heterogeneous OH oxidation of BBA. The reactive uptake of OH by levoglucosan particles increased with RH due to enhanced OH and organic bulk diffusivity. In

  1. Review on advanced of solar assisted chemical heat pump dryer for agriculture produce

    Energy Technology Data Exchange (ETDEWEB)

    Fadhel, M.I. [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450 Melaka (Malaysia); Sopian, K.; Daud, W.R.W.; Alghoul, M.A. [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2011-02-15

    Over the past three decades there has been nearly exponential growth in drying R and D on a global scale. Improving of the drying operation to save energy, improve product quality as well as reduce environmental effect remained as the main objectives of any development of drying system. A solar assisted chemical heat pump dryer is a new solar drying system, which have contributed to better cost-effectiveness and better quality dried products as well as saving energy. A solar collector is adapted to provide thermal energy in a reactor so a chemical reaction can take place. This reduces the dependency of the drying technology on fossil energy for heating. In this paper a review on advanced of solar assisted chemical heat pump dryer is presented (the system model and the results from experimental studies on the system performance are discussed). The review of heat pump dryers and solar assisted heat pump dryer is presented. Description of chemical heat pump types and the overview of chemical heat pump dryer are discussed. The combination of chemical heat pump and solar technology gives extra efficiency in utilizing energy. (author)

  2. Sensitivity of thermal infrared nadir instruments to the chemical and microphysical properties of UTLS secondary sulfate aerosols

    Science.gov (United States)

    Sellitto, P.; Legras, B.

    2016-01-01

    Monitoring upper-tropospheric-lower-stratospheric (UTLS) secondary sulfate aerosols and their chemical and microphysical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact on UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR) satellite nadir observations to the chemical composition and the size distribution of idealised UTLS sulfate aerosol layers. The extinction properties of sulfuric acid/water droplets, for different sulfuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indices taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the extinction of idealised aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulfate and bisulfate ions and the undissociated sulfuric acid, with the main absorption peaks at 1170 and 905 cm-1. The dependence of the aerosol spectral signature to the sulfuric acid mixing ratio, and effective number concentration and radius, as well as the role of interfering parameters like the ozone, sulfur dioxide, carbon dioxide and ash absorption, and temperature and water vapour profile uncertainties

  3. Functional group analysis by H NMR/chemical derivatization for the characterization of organic aerosol from the SMOCC field campaign

    Directory of Open Access Journals (Sweden)

    E. Tagliavini

    2006-01-01

    Full Text Available Water soluble organic compounds (WSOC in aerosol samples collected in the Amazon Basin in a period encompassing the middle/late dry season and the beginning of the wet season, were investigated by H NMR spectroscopy. HiVol filter samples (PM2.5 and PM>2.5 and size-segregated samples from multistage impactor were subjected to H NMR characterization. The H NMR methodology, recently developed for the analysis of organic aerosol samples, has been improved by exploiting chemical methylation of carboxylic groups with diazomethane, which allows the direct determination of the carboxylic acid content of WSOC. The content of carboxylic carbons for the different periods and sizes ranged from 12% to 20% of total measured carbon depending on the season and aerosol size, with higher contents for the fine particles in the transition and wet periods with respect to the dry period. A comprehensive picture is presented of WSOC functional groups in aerosol samples representative of the biomass burning period, as well as of transition and semi-clean atmospheric conditions. A difference in composition between fine (PM2.5 and coarse (PM>2.5 size fractions emerged from the NMR data, the former showing higher alkylic content, the latter being largely dominated by R-O-H (or R-O-R' functional groups. Very small particles (<0.14 μm, however, present higher alkyl-chain content and less oxygenated carbons than larger fine particles (0.42–1.2 μm. More limited variations were found between the average compositions in the different periods of the campaign.

  4. DAWN (Design Assistant Workstation) for advanced physical-chemical life support systems

    Science.gov (United States)

    Rudokas, Mary R.; Cantwell, Elizabeth R.; Robinson, Peter I.; Shenk, Timothy W.

    1989-01-01

    This paper reports the results of a project supported by the National Aeronautics and Space Administration, Office of Aeronautics and Space Technology (NASA-OAST) under the Advanced Life Support Development Program. It is an initial attempt to integrate artificial intelligence techniques (via expert systems) with conventional quantitative modeling tools for advanced physical-chemical life support systems. The addition of artificial intelligence techniques will assist the designer in the definition and simulation of loosely/well-defined life support processes/problems as well as assist in the capture of design knowledge, both quantitative and qualitative. Expert system and conventional modeling tools are integrated to provide a design workstation that assists the engineer/scientist in creating, evaluating, documenting and optimizing physical-chemical life support systems for short-term and extended duration missions.

  5. Daily and hourly chemical impact of springtime transboundary aerosols on Japanese air quality

    NARCIS (Netherlands)

    Moreno, T.; Kojima, T.; Amato, F.; Lucarelli, F.; Rosa, J. de la; Calzolai, G.; Nava, S.; Chiari, M.; Alastuey, A.; Querol, X.; Gibbons, W.

    2013-01-01

    The regular eastward drift of transboundary aerosol intrusions from the Asian mainland into the NW Pacific region has a pervasive impact on air quality in Japan, especially during springtime. Analysis of 24-h filter samples with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and M

  6. Modeling of photolysis rates over Europe: impact on chemical gaseous species and aerosols

    Directory of Open Access Journals (Sweden)

    E. Real

    2010-07-01

    Full Text Available This paper evaluates the impact of photolysis rate calculation on European air composition and air quality monitoring. In particular, the impact of cloud parametrisation and the impact of aerosols on photolysis rates are analysed. Photolysis rates are simulated using the Fast-JX photolysis scheme and gas and aerosol concentrations over Europe are simulated with the regional model Polair3D of the Polyphemus platform. The photolysis scheme is first use to update the clear sky tabulation used in the previous Polair3D version. Important differences in photolysis rates are simulated, mainly due to updated cross-sections in the Fast-JX scheme. In the previous Polair3D version, clouds were taken into account by multiplying the clear-sky photolysis rates using a correction factor. In a second stage, the impact of clouds is taken into account more accurately by simulating them directly in the photolysis scheme. Differences in photolysis rates inside clouds are as high as differences between simulations with and without clouds. Outside clouds, the differences are small. The largest difference in gas concentrations is simulated for OH with a mean increase of its tropospheric burden of 4 to 5%.

    To take into account the impact of aerosols on photolysis rates, Polair3D and Fast-JX are coupled. Photolysis rates are updated every hour. Large impact on photolysis rates is observed at the ground, decreasing with altitude. The aerosol species that impact the most photolysis rates is dust especially in South Europe. Strong impact is also observed over anthropogenic emission regions (Paris, The Po and the Ruhr Valley where mainly nitrate and sulphate reduced the incoming radiation. Differences in photolysis rates lead to changes in gas concentrations, with the largest impact simulated for OH and NO concentrations. At the ground, monthly mean concentrations of both species are reduced over Europe by around 10 to 14% and their tropospheric burden by around 10

  7. Laboratory studies of reactions of atmospheric gases with components of mineral dust aerosol and research in chemical education

    Science.gov (United States)

    Schuttlefield, Jennifer Dianne

    Mineral dust aerosol surfaces provide a medium in the atmosphere for heterogeneous chemistry to occur, which can alter the chemical balance of the Earth's atmosphere. It is becoming increasingly clear that the heterogeneous chemistry of these aerosols is a function of relative humidity (RH), as water on the surface of these particles can enhance or inhibit reactivity depending on the reaction. In this thesis, the uptake of water on clays and oxides was investigated, as well as phase transitions for atmospherically relevant salts. Reactions of carbon dioxide and nitric acid on oxide particles in the presence and absence of water were also examined. Following the reaction of HNO 3 on an alumina surface, photoirradiation experiments were preformed to determine the effect of irradiation on the adsorbed nitrate. The results presented in this thesis provide insight into the heterogeneous reactivity of mineral dust aerosol in the presence and absence of co-adsorbed water, as well as a fundamental understanding of water uptake on soluble and insoluble aerosols. A new method, using a quartz crystal microbalance, was developed to attempt to obtain a better fundamental understanding of different mineral dust components. In addition to the laboratory research, research in chemical education is also presented in this thesis. Two different types of work being done in the area of chemical education are shown. First a new experiment was implemented into an undergraduate physical chemistry course. The technique, ATR-FTIR spectroscopy, was chosen for its ability to expose students to a technique that is commonly used in laboratory research as well as the ease for which high quality results can be obtained. Students used ATR-FTIR spectroscopy to monitor sulfate, SO 42-, adsorption on TiO2 thin films. Second, the role of cognitive load and problem difficulty was accessed with data acquired while students completed an introductory-level chemistry word problem using a web-based tool

  8. Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

    Directory of Open Access Journals (Sweden)

    P. Shrestha

    2010-06-01

    Full Text Available Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June. This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevation in the Middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14~340 nm, and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening, during the transitional period of boundary layer growth and collapse. The increase in number concentration during the peak period was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope mountain winds that force the low level warmer air in the valley to

  9. Phase state of ambient aerosol linked with water uptake and chemical aging in the southeastern US

    Science.gov (United States)

    Pajunoja, Aki; Hu, Weiwei; Leong, Yu J.; Taylor, Nathan F.; Miettinen, Pasi; Palm, Brett B.; Mikkonen, Santtu; Collins, Don R.; Jimenez, Jose L.; Virtanen, Annele

    2016-09-01

    During the summer 2013 Southern Aerosol and Oxidant Study (SOAS) field campaign in a rural site in the southeastern United States, the effect of hygroscopicity and composition on the phase state of atmospheric aerosol particles dominated by the organic fraction was studied. The analysis is based on hygroscopicity measurements by a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA), physical phase state investigations by an Aerosol Bounce Instrument (ABI) and composition measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). To study the effect of atmospheric aging on these properties, an OH-radical oxidation flow reactor (OFR) was used to simulate longer atmospheric aging times of up to 3 weeks. Hygroscopicity and bounce behavior of the particles had a clear relationship showing higher bounce at elevated relative humidity (RH) values for less hygroscopic particles, which agrees well with earlier laboratory studies. Additional OH oxidation of the aerosol particles in the OFR increased the O : C and the hygroscopicity resulting in liquefying of the particles at lower RH values. At the highest OH exposures, the inorganic fraction starts to dominate the bounce process due to production of inorganics and concurrent loss of organics in the OFR. Our results indicate that at typical ambient RH and temperature, organic-dominated particles stay mostly liquid in the atmospheric conditions in the southeastern US, but they often turn semisolid when dried below ˜ 50 % RH in the sampling inlets. While the liquid phase state suggests solution behavior and equilibrium partitioning for the SOA particles in ambient air, the possible phase change in the drying process highlights the importance of thoroughly considered sampling techniques of SOA particles.

  10. Source identification and airborne chemical characterisation of aerosol pollution from long-range transport over Greenland during POLARCAT summer campaign 2008

    Directory of Open Access Journals (Sweden)

    J. Schmale

    2011-03-01

    Full Text Available We deployed an aerosol mass spectrometer during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport summer campaign in Greenland in June/July 2008 on the research aircraft ATR-42. Online size resolved chemical composition data of submicron aerosol were collected up to 7.6 km altitude in the region 60 to 71° N and 40 to 60° W. Biomass burning (BB and fossil fuel combustion (FF plumes originating from North America, Asia, Siberia and Europe were sampled. Transport pathways of detected plumes included advection below 700 hPa, air mass uplifting in warm conveyor belts, and high altitude transport in the upper troposphere. By means of the Lagrangian particle dispersion model FLEXPART, trace gas analysis of O3 and CO, particle size distributions and aerosol chemical composition 48 pollution events were identified and classified into five chemically distinct categories. Aerosol from North American BB consisted of 22% particulate sulphate, while with increasing anthropogenic and Asian influence aerosol was composed of up to 37% sulphate category mean value. Overall, it was found that the organic matter fraction was larger (85% in pollution plumes than for background conditions (71%. Despite different source regions and emission types the particle oxygen to carbon ratio of all plume classes was around 1 indicating low-volatile highly oxygenated aerosol. Also the volume size distributions were rather similar for all sampled plume categories. This can be explained by the relatively long transport times of roughly one week from North America and two weeks from Asia/Siberia. The derived aerosol lifetime for North American emissions was about 9 ± 2 days.

  11. Real time monitoring of accelerated chemical reactions by ultrasonication-assisted spray ionization mass spectrometry.

    Science.gov (United States)

    Lin, Shu-Hsuan; Lo, Ta-Ju; Kuo, Fang-Yin; Chen, Yu-Chie

    2014-01-01

    Ultrasonication has been used to accelerate chemical reactions. It would be ideal if ultrasonication-assisted chemical reactions could be monitored by suitable detection tools such as mass spectrometry in real time. It would be helpful to clarify reaction intermediates/products and to have a better understanding of reaction mechanism. In this work, we developed a system for ultrasonication-assisted spray ionization mass spectrometry (UASI-MS) with an ~1.7 MHz ultrasonic transducer to monitor chemical reactions in real time. We demonstrated that simply depositing a sample solution on the MHz-based ultrasonic transducer, which was placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Singly and multiply charged ions from small and large molecules, respectively, can be observed in the UASI mass spectra. Furthermore, the ultrasonic transducer used in the UASI setup accelerates the chemical reactions while being monitored via UASI-MS. The feasibility of using this approach for real-time acceleration/monitoring of chemical reactions was demonstrated. The reactions of Girard T reagent and hydroxylamine with steroids were used as the model reactions. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions are readily generated and instantaneously monitored using MS within 1 s. Additionally, we also showed the possibility of using this reactive UASI-MS approach to assist the confirmation of trace steroids from complex urine samples by monitoring the generation of the product ions.

  12. Enhanced Bactericidal Activity of Silver Thin Films Deposited via Aerosol-Assisted Chemical Vapor Deposition

    OpenAIRE

    Ponja, S. D.; Sehmi, S. K.; Allan, E.; MacRobert, A. J.; Parkin, I. P.; Carmalt, C. J.

    2015-01-01

    Silver thin films were deposited on SiO2-barrier-coated float glass, fluorine-doped tin oxide (FTO) glass, Activ glass, and TiO2-coated float glass via AACVD using silver nitrate at 350 °C. The films were annealed at 600 °C and analyzed by X-ray powder diffraction, X-ray photoelectron spectroscopy, UV/vis/near-IR spectroscopy, and scanning electron microscopy. All the films were crystalline, and the silver was present in its elemental form and of nanometer dimension. The antibacterial activit...

  13. Physical properties, chemical composition, sources, spatial distribution and sinks of indoor aerosol particles in a university lecture hall

    Science.gov (United States)

    Salma, I.; Dosztály, K.; Borsós, T.; Söveges, B.; Weidinger, T.; Kristóf, G.; Péter, N.; Kertész, Zs.

    2013-01-01

    PM10 mass, particle number (N) and CO2 concentrations, particle number size distributions and meteorological parameters were determined with high time resolution, and daily aerosol samples were collected in the PM10-2.0 and PM2.0 size fractions for chemical analysis in the middle of a university lecture hall for one week. Median concentrations for the PM10 mass and N of 15.3 μg m-3 and 3.7 × 103 cm-3, respectively were derived. The data are substantially smaller than the related outdoor levels or typical values for residences. There were considerable concentration differences for workdays, weekends and various lectures. Main sources of PM10 mass include the usage of chalk sticks for writing, wiping the blackboard, ordinary movements and actions of students and cleaning. High PM10 mass concentration levels up to 100 μg m-3 were realised for short time intervals after wiping the blackboard. The mass concentrations decreased rapidly after the emission source ceased to be active. Two classes of coarse particles were identified. General indoor dust particles exhibited a residence time of approximately 35 min, while the residence time for the chalk dust particles was approximately 20 min as lower estimates. Emission source rate for wiping the blackboard was estimated to be between 8 and 14 mg min-1. This represents a substantial emission rate but the source is active only up to 1 min. Suspension of the chalk (made mainly of gypsum) dust particles was confirmed by enrichment of Ca and S in the hall with respect to ambient urban aerosol. Contribution of ambient aerosol via the heating, ventilation and air conditioning (HVAC) facility was considerable for time intervals when the indoor sources of PM10 mass were not intensive. The HVAC facility introduces, however, the major amount of aerosol particles from the outdoors as far as their number concentration is regarded. Mean contribution of ultrafine particles to the total particle number was (69 ± 7)%, which is smaller

  14. Continuous measurements at the urban roadside in an Asian Megacity by Aerosol Chemical Speciation Monitor (ACSM: particulate matter characteristics during fall and winter seasons in Hong Kong

    Directory of Open Access Journals (Sweden)

    C. Sun

    2015-07-01

    Full Text Available Non-refractory submicron aerosol is characterized using an Aerosol Chemical Speciation Monitor (ACSM in the fall and winter seasons of 2013 at the roadside in an Asian megacity environment in Hong Kong. Organic aerosol (OA, characterized by application of Positive Matrix Factorization (PMF, and sulfate are found dominant. Traffic-related organic aerosol shows good correlation with other vehicle-related species, and cooking aerosol displays clear meal-time concentration maxima and association with surface winds from restaurant areas. Contributions of individual species and OA factors to high NR-PM1 are analyzed for hourly data and daily data; while cooking emissions in OA contribute to high hourly concentrations, particularly during meal times, secondary organic aerosol components are responsible for episodic events and high day-to-day PM concentrations. Clean periods are either associated with precipitation, which reduces secondary OA with a~lesser impact on primary organics, or clean oceanic air masses with reduced long-range transport and better dilution of local pollution. Haze events are connected with increases in contribution of secondary organic aerosol, from 30 to 50 % among total non-refractory organics, and influence of continental air masses.

  15. Continuous measurements at the urban roadside in an Asian megacity by Aerosol Chemical Speciation Monitor (ACSM): particulate matter characteristics during fall and winter seasons in Hong Kong

    Science.gov (United States)

    Sun, C.; Lee, B. P.; Huang, D.; Jie Li, Y.; Schurman, M. I.; Louie, P. K. K.; Luk, C.; Chan, C. K.

    2016-02-01

    Non-refractory submicron aerosol is characterized using an Aerosol Chemical Speciation Monitor (ACSM) in the fall and winter seasons of 2013 on the roadside in an Asian megacity environment in Hong Kong. Organic aerosol (OA), characterized by application of Positive Matrix Factorization (PMF), and sulfate are found to be dominant. Traffic-related organic aerosol shows good correlation with other vehicle-related species, and cooking aerosol displays clear mealtime concentration maxima and association with surface winds from restaurant areas. Contributions of individual species and OA factors to high NR-PM1 are analyzed for hourly data and daily data; while cooking emissions in OA contribute to high hourly concentrations, particularly during mealtimes, secondary organic aerosol components are responsible for episodic events and high day-to-day PM concentrations. Clean periods are either associated with precipitation, which reduces secondary OA with a lesser impact on primary organics, or clean oceanic air masses with reduced long-range transport and better dilution of local pollution. Haze events are connected with increases in contribution of secondary organic aerosol, from 30 to 50 % among total non-refractory organics, and the influence of continental air masses.

  16. Nanostructured Thin Film Synthesis by Aerosol Chemical Vapor Deposition for Energy Storage Applications

    Science.gov (United States)

    Chadha, Tandeep S.

    Renewable energy sources offer a viable solution to the growing energy demand while mitigating concerns for greenhouse gas emissions and climate change. This has led to a tremendous momentum towards solar and wind-based energy harvesting technologies driving efficiencies higher and costs lower. However, the intermittent nature of these energy sources necessitates energy storage technologies, which remain the Achilles heel in meeting the renewable energy goals. This dissertation focusses on two approaches for addressing the needs of energy storage: first, targeting direct solar to fuel conversion via photoelectrochemical water-splitting and second, improving the performance of current rechargeable batteries by developing new electrode architectures and synthesis processes. The aerosol chemical vapor deposition (ACVD) process has emerged as a promising single-step approach for nanostructured thin film synthesis directly on substrates. The relationship between the morphology and the operating parameters in the process is complex. In this work, a simulation based approach has been developed to understand the relationship and acquire the ability of predicting the morphology. These controlled nanostructured morphologies of TiO2 , compounded with gold nanoparticles of various shapes, are used for solar water-splitting applications. Tuning of light absorption in the visible-light range along with reduced electron-hole recombination in the composite structures has been demonstrated. The ACVD process is further extended to a novel single-step synthesis of nanostructured TiO2 electrodes directly on the current collector for applications as anodes in lithium-ion batteries, mainly for electric vehicles and hybrid electric vehicles. The effect of morphology of the nanostructures has been investigated via experimental studies and electrochemical transport modelling. Results demonstrate the exceptional performance of the single crystal one-dimensional nanostructures over granular

  17. Mid-Infrared Mapping of Jupiter's Temperatures, Aerosol Opacity and Chemical Distributions with IRTF/TEXES

    CERN Document Server

    Fletcher, L N; Orton, G S; Sinclair, J A; Giles, R S; Irwin, P G J; Encrenaz, T

    2016-01-01

    Global maps of Jupiter's atmospheric temperatures, gaseous composition and aerosol opacity are derived from a programme of 5-20 $\\mu$m mid-infrared spectroscopic observations using the Texas Echelon Cross Echelle Spectrograph (TEXES) on NASA's Infrared Telescope Facility (IRTF). Image cubes from December 2014 in eight spectral channels, with spectral resolutions of $R\\sim2000-12000$ and spatial resolutions of $2-4^\\circ$ latitude, are inverted to generate 3D maps of tropospheric and stratospheric temperatures, 2D maps of upper tropospheric aerosols, phosphine and ammonia, and 2D maps of stratospheric ethane and acetylene. The results are compared to a re-analysis of Cassini Composite Infrared Spectrometer (CIRS) observations acquired during Cassini's closest approach to Jupiter in December 2000, demonstrating that this new archive of ground-based mapping spectroscopy can match and surpass the quality of previous investigations, and will permit future studies of Jupiter's evolving atmosphere. We identify mid-i...

  18. Connecting Organic Aerosol Climate-Relevant Properties to Chemical Mechanisms of Sources and Processing

    Energy Technology Data Exchange (ETDEWEB)

    Thornton, Joel [Univ. of Washington, Seattle, WA (United States)

    2015-01-26

    The research conducted on this project aimed to improve our understanding of secondary organic aerosol (SOA) formation in the atmosphere, and how the properties of the SOA impact climate through its size, phase state, and optical properties. The goal of this project was to demonstrate that the use of molecular composition information to mechanistically connect source apportionment and climate properties can improve the physical basis for simulation of SOA formation and properties in climate models. The research involved developing and improving methods to provide online measurements of the molecular composition of SOA under atmospherically relevant conditions and to apply this technology to controlled simulation chamber experiments and field measurements. The science we have completed with the methodology will impact the simulation of aerosol particles in climate models.

  19. In situ physical and chemical characterisation of the Eyjafjallajökull aerosol plume in the free troposphere over Italy

    Science.gov (United States)

    Sandrini, S.; Giulianelli, L.; Decesari, S.; Fuzzi, S.; Cristofanelli, P.; Marinoni, A.; Bonasoni, P.; Chiari, M.; Calzolai, G.; Canepari, S.; Perrino, C.; Facchini, M. C.

    2014-01-01

    Continuous measurements of physical and chemical properties at the Mt. Cimone (Italy) GAW-WMO (Global Atmosphere Watch, World Meteorological Organization) Global Station (2165 m a.s.l.) have allowed the detection of the volcanic aerosol plume resulting from the Eyjafjallajökull (Iceland) eruption of spring 2010. The event affected the Mt. Cimone site after a transport over a distance of more than 3000 km. Two main transport episodes were detected during the eruption period, showing a volcanic fingerprint discernible against the free tropospheric background conditions typical of the site, the first from April 19 to 21 and the second from 18 to 20 May 2010. This paper reports the modification of aerosol characteristics observed during the two episodes, both characterised by an abrupt increase in fine and, especially, coarse mode particle number. Analysis of major, minor and trace elements by different analytical techniques (ionic chromatography, particle induced X-ray emission-particle induced gamma-ray emission (PIXE-PIGE) and inductively coupled plasma mass spectrometry (ICP-MS)) were performed on aerosols collected by ground-level discrete sampling. The resulting database allows the characterisation of aerosol chemical composition during the volcanic plume transport and in background conditions. During the passage of the volcanic plume, the fine fraction was dominated by sulphates, denoting the secondary origin of this mode, mainly resulting from in-plume oxidation of volcanic SO2. By contrast, the coarse fraction was characterised by increased concentration of numerous elements of crustal origin, such as Fe, Ti, Mn, Ca, Na, and Mg, which enter the composition of silicate minerals. Data analysis of selected elements (Ti, Al, Fe, Mn) allowed the estimation of the volcanic plume's contribution to total PM10, resulting in a local enhancement of up to 9.5 μg m-3, i.e. 40% of total PM10 on 18 May, which was the most intense of the two episodes. These results appear

  20. Production Mechanisms, Number Concentration, Size Distribution. Chemical Composition, and Optical Properties of Sea Spray Aerosols

    Science.gov (United States)

    Meskhidze, Nicholas; Petters, Markus; Tsigaridis, Kostas; Bates. Tim; O'Dowd, Colin; Reid, Jeff; Lewis, Ernie R.; Gantt, Brett; Anguelova, Magdalena D.; Bhave, Prakash V.; Bird, James; Callaghan, Adrian H.; Ceburnis, Darius; Chang, Rachel; Clark, Antony; deLeeuw, Gerrit; Deane, Grant; DeMott, Paul J.; Elliot, Scott; Facchini, Maria Cristina; Fairall, Chris W.; Hawkins, Lelia; Hu, Yongxiang; Smirnov, Alexander

    2013-01-01

    Over forty scientists from six countries convened in Raleigh, NC on June 4-6 2012 to review the status and prospects of sea spray aerosol research. Participants were researchers from the oceanography and atmospheric science communities, including academia, private industry, and government agencies. The recommendations from the working groups are summarized in a science prioritization matrix that is meant to prioritize the research agenda and identify areas of investigation by the magnitude of their impact on proposed science questions. Str

  1. Microwave-irradiation-assisted hybrid chemical approach for titanium dioxide nanoparticle synthesis: microbial and cytotoxicological evaluation.

    Science.gov (United States)

    Ranjan, Shivendu; Dasgupta, Nandita; Rajendran, Bhavapriya; Avadhani, Ganesh S; Ramalingam, Chidambaram; Kumar, Ashutosh

    2016-06-01

    Titanium dioxide nanoparticles (TNPs) are widely used in the pharmaceutical and cosmetics industries. It is used for protection against UV exposure due to its light-scattering properties and high refractive index. Though TNPs are increasingly used, the synthesis of TNPs is tedious and time consuming; therefore, in the present study, microwave-assisted hybrid chemical approach was used for TNP synthesis. In the present study, we demonstrated that TNPs can be synthesized only in 2.5 h; however, the commonly used chemical approach using muffle furnace takes 5 h. The activity of TNP depends on the synthetic protocol; therefore, the present study also determined the effect of microwave-assisted hybrid chemical approach synthetic protocol on microbial and cytotoxicity. The results showed that TNP has the best antibacterial activity in decreasing order from Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. The IC50 values of TNP for HCT116 and A549 were found to be 6.43 and 6.04 ppm, respectively. Cell death was also confirmed from trypan blue exclusion assay and membrane integrity loss was observed. Therefore, the study determines that the microwave-assisted hybrid chemical approach is time-saving; hence, this technique can be upgraded from lab scale to industrial scale via pilot plant scale. Moreover, it is necessary to find the mechanism of action at the molecular level to establish the reason for greater bacterial and cytotoxicological toxicity. Graphical abstract A graphical representation of TNP synthesis.

  2. Carbonaceous aerosol in jet engine exhaust: emission characteristics and implications for heterogeneous chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Petzold, A.; Schroeder, F.P.; Kaercher, B. [Deutsches Zentrum fuer Luft- und Raumfahrt, Wessling (Germany). Institut fuer Physik der Atmosphaere; Stroem, J. [Stockholm University (Sweden). Dept. of Meteorology

    1999-08-01

    Characteristic parameters of black carbon aerosol (BC) emitted from jet engine were measured during ground tests and in-flight behind the same aircraft. Size distribution features were a primary BC mode at a model diameter D {approx} 0.045 {mu}m, and a BC agglomeration mode at D < 0.2 {mu}m. The total BC number concentration at the engine exit was 2.9 x 10{sup 7} cm{sup -3} with good agreement between model results and in-flight measured number concentrations of non-volatile particles with D {>=} 0.014 {mu}m. A comparison between total number concentration of BC particles and the non-volatile fraction of the total aerosol at the exit plane suggests that the non-volatile fraction of jet engine exhaust aerosol consists almost completely of BC. In-flight BC mass emission indices ranged from 0.11 to 0.15 g BC (kg fuel){sup -1}. The measured in-flight particle emission value was 1.75 {+-} 0.15 x 10{sup 15} kg{sup -1} with corresponding ground test values of 1.0-8.7 x 10{sup 14} kg{sup -1}. Both size distribution properties and mass emission indices can be scaled from ground test to in-flight conditions. Implications for atmosphere BC loading, BC and cirrus interaction and the potential of BC for perturbation of atmospheric chemistry are briefly outlined. (author)

  3. Mid-infrared mapping of Jupiter's temperatures, aerosol opacity and chemical distributions with IRTF/TEXES

    Science.gov (United States)

    Fletcher, Leigh N.; Greathouse, T. K.; Orton, G. S.; Sinclair, J. A.; Giles, R. S.; Irwin, P. G. J.; Encrenaz, T.

    2016-11-01

    Global maps of Jupiter's atmospheric temperatures, gaseous composition and aerosol opacity are derived from a programme of 5-20 μm mid-infrared spectroscopic observations using the Texas Echelon Cross Echelle Spectrograph (TEXES) on NASA's Infrared Telescope Facility (IRTF). Image cubes from December 2014 in eight spectral channels, with spectral resolutions of R ∼2000 - 12 , 000 and spatial resolutions of 2-4° latitude, are inverted to generate 3D maps of tropospheric and stratospheric temperatures, 2D maps of upper tropospheric aerosols, phosphine and ammonia, and 2D maps of stratospheric ethane and acetylene. The results are compared to a re-analysis of Cassini Composite Infrared Spectrometer (CIRS) observations acquired during Cassini's closest approach to Jupiter in December 2000, demonstrating that this new archive of ground-based mapping spectroscopy can match and surpass the quality of previous investigations, and will permit future studies of Jupiter's evolving atmosphere. The visibility of cool zones and warm belts varies from channel to channel, suggesting complex vertical variations from the radiatively-controlled upper troposphere to the convective mid-troposphere. We identify mid-infrared signatures of Jupiter's 5-μm hotspots via simultaneous M, N and Q-band observations, which are interpreted as temperature and ammonia variations in the northern Equatorial Zone and on the edge of the North Equatorial Belt (NEB). Equatorial plumes enriched in NH3 gas are located south-east of NH3-desiccated 'hotspots' on the edge of the NEB. Comparison of the hotspot locations in several channels across the 5-20 μm range indicate that these anomalous regions tilt westward with altitude. Aerosols and PH3 are both enriched at the equator but are not co-located with the NH3 plumes. The equatorial temperature minimum and PH3/aerosol maxima have varied in amplitude over time, possibly as a result of periodic equatorial brightenings and the fresh updrafts of

  4. Chemical characterization of the main secondary organic aerosol (SOA products formed through aqueous-phase photonitration of guaiacol

    Directory of Open Access Journals (Sweden)

    Z. Kitanovski

    2014-04-01

    Full Text Available Guaiacol (2-methoxyphenol and its derivatives can be emitted into the atmosphere by thermal degradation (i.e. burning of wood lignins. Due to its volatility, guaiacol is predominantly distributed in the atmospheric gaseous phase. Recent studies have shown the importance of aqueous-phase reactions in addition to the dominant gas-phase and heterogeneous reactions of guaiacol, in the formation of secondary organic aerosol (SOA in the atmosphere. The main objectives of the present study were to chemically characterize the low-volatility SOA products of the aqueous-phase photonitration of guaiacol and examine their possible presence in urban atmospheric aerosols. The aqueous-phase reactions were carried out under simulated sunlight and in the presence of H2O2 and nitrite. The formed guaiacol reaction products were concentrated by using solid-phase extraction (SPE and then purified by means of semi-preparative high-performance liquid chromatography (HPLC. The fractionated individual compounds were isolated as pure solids and further analyzed with liquid-state 1H, 13C and 2D nuclear magnetic resonance (NMR spectroscopy and direct infusion negative ion electrospray ionization tandem mass spectrometry ((–ESI-MS/MS. The NMR and product ion (MS2 spectra were used for unambiguous product structure elucidation. The main products of guaiacol photonitration are 4-nitroguaiacol (4NG, 6-nitroguaiacol (6NG, and 4,6-dinitroguaiacol (4,6DNG. Using the isolated compounds as standards, 4NG and 4,6DNG were unambiguously identified in winter PM10 aerosols from the city of Ljubljana (Slovenia by means of HPLC/(–ESI-MS/MS. Owing to the strong absorption of UV and visible light, 4,6DNG could be an important constituent of atmospheric "brown" carbon, especially in regions affected by biomass burning.

  5. A European aerosol phenomenology—2: chemical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe

    Science.gov (United States)

    Putaud, Jean-P.; Raes, Frank; Van Dingenen, Rita; Brüggemann, Erika; Facchini, M.-Cristina; Decesari, Stefano; Fuzzi, Sandro; Gehrig, Robert; Hüglin, Cristoph; Laj, Paolo; Lorbeer, Gundi; Maenhaut, Willy; Mihalopoulos, Nikolaos; Müller, Konrad; Querol, Xavier; Rodriguez, Sergio; Schneider, Jürgen; Spindler, Gerald; Brink, Harry ten; Tørseth, Kjetil; Wiedensohler, Alfred

    This paper synthesizes data on aerosol (or particulate matter, PM) chemical characteristics, which were obtained in European aerosol research activities at natural, rural, near-city, urban, and kerbside sites over the past decade. It includes only two (nearby) sites in the semi-arid Mediterranean area, and lacks data from Eastern Europe. PM chemical compositions are compared with the PM mass concentrations in PM10, PM2.5, and further size resolved PM fractions (chemical mass closure). Such data sets are more comprehensive than those currently provided by air quality monitoring networks (e.g. EMEP, EUROAIRNET). Data available from 24 sites in Europe were reviewed. They were processed and plotted to allow comparisons in spite of differences in the sampling and analytical techniques used in various studies. A number of conclusions are drawn among which are the following. Organic matter appears to be the major component of PM10 and PM2.5, except at natural and rural background sites, where sulphate contribution may be larger. Mineral dust shows up as a major component of PM10 at kerbside sites. Black carbon contributes 5-10% to PM2.5 and somewhat less to PM10 at all sites, including the natural background sites. Its contribution seems higher (15-20%) at some of the kerbside sites, but these data may be affected by analytical artefacts. On days when PM10 >50 μg m -3, nitrate concentrations can overtake organic matter concentrations in PM10 and PM2.5. High PM concentration episodes are often observed in cold periods, when the pollutant dispersion is least. Measurements indicate that the condensation in the particle phase of semi-volatile species like nitrate and (unspecified) organics is also favoured by cold temperatures. In particles with a diameter technological gap between scientific measurements and regulatory monitoring networks, is strongly needed.

  6. Antimony sulfide thin films prepared by laser assisted chemical bath deposition

    Science.gov (United States)

    Shaji, S.; Garcia, L. V.; Loredo, S. L.; Krishnan, B.; Aguilar Martinez, J. A.; Das Roy, T. K.; Avellaneda, D. A.

    2017-01-01

    Antimony sulfide (Sb2S3) thin films were prepared by laser assisted chemical bath deposition (LACBD) technique. These thin films were deposited on glass substrates from a chemical bath containing antimony chloride, acetone and sodium thiosulfate under various conditions of normal chemical bath deposition (CBD) as well as in-situ irradiation of the chemical bath using a continuous laser of 532 nm wavelength. Structure, composition, morphology, optical and electrical properties of the Sb2S3 thin films produced by normal CBD and LACBD were analyzed by X-Ray diffraction (XRD), Raman Spectroscopy, Atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and Photoconductivity. The results showed that LACBD is an effective synthesis technique to obtain Sb2S3 thin films for optoelectronic applications.

  7. Characterization of Organic Nitrate Formation in Limonene Secondary Organic Aerosol using High-Resolution Chemical Ionization Mass Spectrometry

    Science.gov (United States)

    Faxon, Cameron; Hammes, Julia; Peng, Jianfei; Hallquist, Mattias; Pathak, Ravi

    2016-04-01

    Previous work has shown that organic nitrates (RONO2) are prevalent in the boundary layer, and can contribute significantly to secondary organic aerosol formation. Monoterpenes, including limonene, have been shown to be precursors for the formation of these organic nitrates. Limonene has two double bonds, either of which may be oxidized by NO3 or O3. This leads to the generation of products that can subsequently condense or partition into the particle phase, producing secondary organic aerosol. In order to further elucidate the particle and gas phase product distribution of organic nitrates forming from the reactions of limonene and the nitrate radical (NO3), a series of experiments were performed in the Gothenburg Flow Reactor for Oxidation Studies at Low Temperatures (G-FROST), described by previous work. N2O5 was used as the source for NO3 and NO2, and a characterized diffusion source was used to introduce limonene into the flow reactor. All experiments were conducted in the absence of light, and the concentration of limonene was increased step-wise throughout each experiment to modify the ratio of N2O5to limonene. The experiments were conducted such that both limonene- and N2O5-limited regimes were present. Gas and particle phase products were measured using an iodide High-Resolution Time-of-Flight Mass Spectrometer (HR-ToF-CIMS) coupled to a Filter Inlet for Gases and AEROsols (FIGAERO, and particle size and SOA mass concentrations were derived using a Scanning Mobility Particle Sizer (SMPS). CIMS measurement techniques have previously been employed for the measurement of organic nitrate products of such compounds using multiple reagent ions. The use of this instrumentation allowed for the identification of chemical formulas for gas and particle phase species. The findings from the experiments will be presented in terms of the relative gas-particle partitioning of major products and the effects of N2O5/limonene ratios on product distributions. Additionally, a

  8. Sources, seasonality, and trends of Southeast US aerosol: an integrated analysis of surface, aircraft, and satellite observations with the GEOS-Chem chemical transport model

    Directory of Open Access Journals (Sweden)

    P. S. Kim

    2015-07-01

    Full Text Available We use an ensemble of surface (EPA CSN, IMPROVE, SEARCH, AERONET, aircraft (SEAC4RS, and satellite (MODIS, MISR observations over the Southeast US during the summer-fall of 2013 to better understand aerosol sources in the region and the relationship between surface particulate matter (PM and aerosol optical depth (AOD. The GEOS-Chem global chemical transport model (CTM with 25 km × 25 km resolution over North America is used as a common platform to interpret measurements of different aerosol variables made at different times and locations. Sulfate and organic aerosol (OA are the main contributors to surface PM2.5 (mass concentration of PM finer than 2.5 μm aerodynamic diameter and AOD over the Southeast US. GEOS-Chem simulation of sulfate requires a missing oxidant, taken here to be stabilized Criegee intermediates, but which could alternatively reflect an unaccounted for heterogeneous process. Biogenic isoprene and monoterpenes account for 60 % of OA, anthropogenic sources for 30 %, and open fires for 10 %. 60 % of total aerosol mass is in the mixed layer below 1.5 km, 20 % in the cloud convective layer at 1.5–3 km, and 20 % in the free troposphere above 3 km. This vertical profile is well captured by GEOS-Chem, arguing against a high-altitude source of OA. The extent of sulfate neutralization (f = [NH4+]/(2[SO42−] + [NO3−] is only 0.5–0.7 mol mol−1 in the observations, despite an excess of ammonia present, which could reflect suppression of ammonia uptake by organic aerosol. This would explain the long-term decline of ammonium aerosol in the Southeast US, paralleling that of sulfate. The vertical profile of aerosol extinction over the Southeast US follows closely that of aerosol mass. GEOS-Chem reproduces observed total column aerosol mass over the Southeast US within 6 %, column aerosol extinction within 16 %, and space-based AOD within 21 %. The large AOD decline observed from summer to winter is driven by sharp declines in both

  9. On titanium dioxide thin films growth from the direct current electric field assisted chemical vapour deposition of titanium (IV) chloride in toluene

    Energy Technology Data Exchange (ETDEWEB)

    Romero, L. [School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Jorge-Sobrido, A.-B.; McMillian, P.F. [Christopher Ingold Building (Chemistry), University College of London, 20 Gordon street, London WC1H 0AJ (United Kingdom); Binions, R. [School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2015-06-01

    Titanium dioxide thin films were deposited from the aerosol assisted chemical vapour deposition reaction of titanium tetrachloride in toluene (1 M) at 600 °C and 5 L min{sup −1}. Direct current electric fields were applied and increased in a range of 0 to 30 V during the reaction. Changes in particle size, agglomeration and particle shape were observed. Raman spectroscopy analysis revealed different composition of anatase and rutile and crystal phase depending on the field strength applied. The photocatalytic activity was calculated from the half-life or time needed by the films to degrade 50% Resazurin dye-ink initial concentration. High photocatalytic performance with high anatase content (98.3%) was observed with half-life values of 3.9 min. Deposited films with pure content in rutile showed better photocatalytic performance than films with mix of crystal phases with anatase content below 40%. - Highlights: • Electric field assisted chemical vapour deposition used to synthesis titania thin films. • Significant alterations to crystallographic orientation and microstructure observed • Order of magnitude reduction in half life of dye degradation obtainable.

  10. Chemical Imaging of Ambient Aerosol Particles: Observational Constraints on Mixing State Parameterization

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Rachel; Wang, Bingbing; Laskin, Alexander; Riemer, Nicole; West, Matthew; Zhang, Qi; Sun, Yele; Yu, Xiao-Ying; Alpert, Peter A.; Knopf, Daniel A.; Gilles, Mary K.; Moffet, Ryan

    2015-09-28

    A new parameterization for quantifying the mixing state of aerosol populations has been applied for the first time to samples of ambient particles analyzed using spectro-microscopy techniques. Scanning transmission x-ray microscopy/near edge x-ray absorption fine structure (STXM/NEXAFS) and computer controlled scanning electron microscopy/energy dispersive x-ray spectroscopy (CCSEM/EDX) were used to probe the composition of the organic and inorganic fraction of individual particles collected on June 27th and 28th during the 2010 Carbonaceous Aerosols and Radiative Effects (CARES) study in the Central Valley, California. The first field site, T0, was located in downtown Sacramento, while T1 was located near the Sierra Nevada Mountains. Mass estimates of the aerosol particle components were used to calculate mixing state metrics, such as the particle-specific diversity, bulk population diversity, and mixing state index, for each sample. Both microscopy imaging techniques showed more changes over these two days in the mixing state at the T0 site than at the T1 site. The STXM data showed evidence of changes in the mixing state associated with a build-up of organic matter confirmed by collocated measurements and the largest impact on the mixing state was due to an increase in soot dominant particles during this build-up. The CCSEM/EDX analysis showed the presence of two types of particle populations; the first was dominated by aged sea salt particles and had a higher mixing state index (indicating a more homogeneous population), the second was dominated by carbonaceous particles and had a lower mixing state index.

  11. Chemical imaging of ambient aerosol particles: Observational constraints on mixing state parameterization

    Science.gov (United States)

    O'Brien, Rachel E.; Wang, Bingbing; Laskin, Alexander; Riemer, Nicole; West, Matthew; Zhang, Qi; Sun, Yele; Yu, Xiao-Ying; Alpert, Peter; Knopf, Daniel A.; Gilles, Mary K.; Moffet, Ryan C.

    2015-09-01

    A new parameterization for quantifying the mixing state of aerosol populations has been applied for the first time to samples of ambient particles analyzed using spectro-microscopy techniques. Scanning transmission X-ray microscopy/near edge X-ray absorption fine structure (STXM/NEXAFS) and computer-controlled scanning electron microscopy/energy dispersive X-ray spectroscopy (CCSEM/EDX) were used to probe the composition of the organic and inorganic fraction of individual particles collected on 27 and 28 June during the 2010 Carbonaceous Aerosols and Radiative Effects study in the Central Valley, California. The first field site, T0, was located in downtown Sacramento, while T1 was located near the Sierra Nevada Mountains. Mass estimates of the aerosol particle components were used to calculate mixing state metrics, such as the particle-specific diversity, bulk population diversity, and mixing state index, for each sample. The STXM data showed evidence of changes in the mixing state associated with a buildup of organic matter confirmed by collocated measurements, and the largest impact on the mixing state was due to an increase in soot dominant particles during this buildup. The mixing state from STXM was similar between T0 and T1, indicating that the increased organic fraction at T1 had a small effect on the mixing state of the population. The CCSEM/EDX analysis showed the presence of two types of particle populations: the first was dominated by aged sea-salt particles and had a higher mixing state index (indicating a more homogeneous population); the second was dominated by carbonaceous particles and had a lower mixing state index.

  12. Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK

    Directory of Open Access Journals (Sweden)

    D. Johnson

    2006-01-01

    Full Text Available Following on from the companion study (Johnson et al., 2006, a photochemical trajectory model (PTM has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA material and the formation of secondary organic aerosol (SOA material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings, the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1. For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species. Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its

  13. ARTICLES: Influence Factors on Particle Growth for On-line Aerosol Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

    Science.gov (United States)

    Xia, Wei-wei; Ti, Ru-fang; Zhang, Zi-Iiang; Zheng, Hai-yang; Fang, Li

    2010-06-01

    An evaporation/condensation flow cell was developed and interfaced with the matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometer for on-line bioaerosol detection and characterization, which allows matrix addition by condensation onto the laboratory-generated bioaerosol particles. The final coated particle exiting from the condenser is then introduced into the aerodynamic particle sizer spectrometer or home-built aerosol laser time-of-flight mass spectrometer, and its aerodynamic size directly effects on the matrix-to-analyte molar ratio, which is very important for MALDI technique. In order to observe the protonated analyte molecular ion, and then determine the classification of biological aerosols, the matrix-to-analyte molar ratio must be appropriate. Four experimental parameters, including the temperature of the heated reservoir, the initial particle size, its number concentration, and the matrix material, were tested experimentally to analyze their influences on the final particle size. This technique represents an on-line system of detection that has the potential to provide rapid and reliable identification of airborne biological aerosols.

  14. Chemical characterization of submicron aerosol and particle growth events at a national background site (3295 m a.s.l. in the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    W. Du

    2015-05-01

    Full Text Available Atmospheric aerosols exert highly uncertain impacts on radiative forcing and also have detrimental effects on human health. While aerosol particles are widely characterized in megacities in China, aerosol composition, sources and particle growth in rural areas in the Tibetan Plateau remain less understood. Here we present the results from an autumn study that was conducted from 5 September to 15 October 2013 at a national background monitoring station (3295 m a.s.l. in the Tibetan Plateau. The submicron aerosol composition and particle number size distributions were measured in situ with an Aerodyne Aerosol Chemical Speciation Monitor (ACSM and a Scanning Mobility Particle Sizer (SMPS. The average mass concentration of submicron aerosol (PM1 is 11.9 μg m−3 (range: 1.0–78.4 μg m−3 for the entire study, which is much lower than those observed at urban and rural sites in eastern China. Organics dominated PM1 on average accounting for 43%, followed by sulfate (28% and nitrate (1%. Positive matrix factorization analysis of ACSM organic aerosol (OA mass spectra identified an oxygenated OA (OOA and a biomass burning OA (BBOA. The OOA dominated OA composition accounting for 85% on average, 17% of which was inferred from aged BBOA. The BBOA contributed a considerable fraction of OA (15% due to the burning of cow dung and straws in September. New particle formation and growth events were frequently observed (80% of time throughout the study. The average particle growth rate is 2.0 nm h−1 (range: 0.8–3.2 nm h−1. By linking the evolution of particle number size distribution to aerosol composition, we found an elevated contribution of organics during particle growth periods and also a positive relationship between the growth rate and the fraction of OOA in OA, which potentially indicates an important role of organics in particle growth in the Tibetan Plateau.

  15. Global aerosol modeling with the online NMMB/BSC Chemical Transport Model: sensitivity to fire injection height prescription and secondary organic aerosol schemes

    Science.gov (United States)

    Spada, Michele; Jorba, Oriol; Pérez García-Pando, Carlos; Tsigaridis, Kostas; Soares, Joana; Obiso, Vincenzo; Janjic, Zavisa; Baldasano, Jose M.

    2015-04-01

    We develop and evaluate a fully online-coupled model simulating the life-cycle of the most relevant global aerosols (i.e. mineral dust, sea-salt, black carbon, primary and secondary organic aerosols, and sulfate) and their feedbacks upon atmospheric chemistry and radiative balance. Following the capabilities of its meteorological core, the model has been designed to simulate both global and regional scales with unvaried parameterizations: this allows detailed investigation on the aerosol processes bridging the gap between global and regional models. Since the strong uncertainties affecting aerosol models are often unresponsive to model complexity, we choose to introduce complexity only when it clearly improves results and leads to a better understanding of the simulated aerosol processes. We test two important sources of uncertainty - the fires injection height and secondary organic aerosol (SOA) production - by comparing a baseline simulation with experiments using more advanced approaches. First, injection heights prescribed by Dentener et al. (2006, ACP) are compared with climatological injection heights derived from satellite measurements and produced through the Integrated Monitoring and Modeling System For Wildland Fires (IS4FIRES). Also global patterns of SOA produced by the yield conversion of terpenes as prescribed by Dentener et al. (2006, ACP) are compared with those simulated by the two-product approach of Tsigaridis et al. (2003, ACP). We evaluate our simulations using a variety of observations and measurement techniques. Additionally, we discuss our results in comparison to other global models within AEROCOM and ACCMIP.

  16. Chemical-assisted phytoremediation of CD-PAHs contaminated soils using Solanum nigrum L.

    Science.gov (United States)

    Yang, Chuanjie; Zhou, Qixing; Wei, Shuhe; Hu, Yahu; Bao, Yanyu

    2011-09-01

    A well-characterized cadmium (Cd) hyperaccumulating plant Solanum nigrum was grown in Cd and polycyclic aromatic hydrocarbons (PAHs) co-contaminated soil that was repeatedly amended with chemicals, including EDTA, cysteine (CY), salicylic acid (Sa), and Tween 80 (TW80), to test individual and combined treatment effects on phytoremediation of Cd-PAHs contaminated soils. Plant growth was negatively affected by exogenous chemicals except for EDTA. S. nigrum could accumulate Cd in tissues without assistant chemicals, while there was no visible effect on the degradation of PAHs. Cysteine had significant effects on phytoextraction of Cd and the highest metal extraction ratio (1.27%) was observed in 0.9 mmol/kg CY treatment. Both salicylic acid and Tween 80 had stimulative effects on the degradation of PAHs and there was the maximal degradation rate (52.6%) of total PAHs while 0.9 mmol/kg Sa was applied. Furthermore, the combined treatment T(0.1EDTA+0.9CY+0.5TW80) and T(0.5EDTA+0.9CY+03Sa) could not only increase the accumulation of Cd in plant tissues, but also promote the degradation of PAHs. These results indicated that S. nigrum might be effective in phytoextracting Cd and enhancing the biodegradation of PAHs in the co-contaminated soils with assistant chemicals.

  17. Seasonality of new particle formation in Vienna, Austria - Influence of air mass origin and aerosol chemical composition

    Science.gov (United States)

    Wonaschütz, Anna; Demattio, Anselm; Wagner, Robert; Burkart, Julia; Zíková, Naděžda; Vodička, Petr; Ludwig, Wolfgang; Steiner, Gerhard; Schwarz, Jaroslav; Hitzenberger, Regina

    2015-10-01

    The impact of air mass origin and season on aerosol chemical composition and new particle formation and growth events (NPF events) in Vienna, Austria, is investigated using impactor samples from short-term campaigns and two long-term number size distribution datasets. The results suggest that air mass origin is most important for bulk PM concentrations, chemical composition of the coarse fraction (>1.5 μm) and the mass size distribution, and less important for chemical composition of the fine fraction (<1.5 μm). Continental air masses (crustal elements) were distinguished from air masses of marine origin (traces of sea salt). NPF events were most frequent in summer (22% of measurement days), and least frequent in winter (3% of measurement days). They were associated with above-average solar radiation and ozone concentrations, but were largely independent of PM2.5. Air mass origin was a secondary influence on NPF, largely through its association with meteorological conditions. Neither a strong dependence on the PM2.5 loading of the air masses, nor indications of a source area for NPF precursors outside the city were found.

  18. Differences across the ITCZ in the chemical characteristics of the Indian Ocean MBL aerosol during INDOEX

    Directory of Open Access Journals (Sweden)

    M. Norman

    2003-01-01

    Full Text Available The water soluble inorganic part of the sub-micrometer aerosol was measured from two research vessels over the Indian Ocean during the winter monsoon season (February and March as part of the INDOEX project in 1998 and 1999. Additional measurements were made of gas phase SO2 from one of the vessels in 1999. All samples collected north of the Inter Tropical Convergence Zone, ITCZ, were clearly affected by continental, anthropogenic sources. A sharp transition occurred across the ITCZ with concentrations of nss-SO42-, NH4+ and nss-K+ being lower by a factor of 7-15, >20 and >40, respectively, on the southern side of the ITCZ. The contribution from DMS to the sub-micrometer nss-SO42- was estimated to be up to 40% in clean air north of the ITCZ but less than 10% in polluted air originating from India. South of the ITCZ virtually all nss-SO42- was likely to be derived from oxidation of DMS. The concentration of SO2 decreased rapidly with distance from the Indian coast, the molar ratio SO2/nss-SO42- reaching values below 5% after 35 h travel time over the ocean. Surprisingly, MSA, which is derived from DMS, also showed higher concentrations in the sub-micrometer aerosol north of the ITCZ than south of it. This could be explained by the larger sub-micrometer surface area available north of the ITCZ for the condensation of MSA. South of the ITCZ a major part of the MSA was found on the super-micrometer particles. An analysis based on the air trajectories showed that systematic variation in the observed concentrations was associated with variations in the transport from source regions. For example, differences in time since air parcels left the Arabian or Indian coasts was shown to be an important factor for explaining the substantial differences in absolute concentrations.

  19. CdS thin films prepared by laser assisted chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, L.V.; Mendivil, M.I.; Garcia Guillen, G.; Aguilar Martinez, J.A. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); CIIDIT – Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G.A.; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); CIIDIT – Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2015-05-01

    Highlights: • CdS thin films by conventional CBD and laser assisted CBD. • Characterized these films using XRD, XPS, AFM, optical and electrical measurements. • Accelerated growth was observed in the laser assisted CBD process. • Improved dark conductivity and good photocurrent response for the LACBD CdS. - Abstract: In this work, we report the preparation and characterization of CdS thin films by laser assisted chemical bath deposition (LACBD). CdS thin films were prepared from a chemical bath containing cadmium chloride, triethanolamine, ammonium hydroxide and thiourea under various deposition conditions. The thin films were deposited by in situ irradiation of the bath using a continuous laser of wavelength 532 nm, varying the power density. The thin films obtained during deposition of 10, 20 and 30 min were analyzed. The changes in morphology, structure, composition, optical and electrical properties of the CdS thin films due to in situ irradiation of the bath were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy. The thin films obtained by LACBD were nanocrystalline, photoconductive and presented interesting morphologies. The results showed that LACBD is an effective synthesis technique to obtain nanocrystalline CdS thin films having good optoelectronic properties.

  20. 21 CFR 173.315 - Chemicals used in washing or to assist in the peeling of fruits and vegetables.

    Science.gov (United States)

    2010-04-01

    ... peeling of fruits and vegetables. 173.315 Section 173.315 Food and Drugs FOOD AND DRUG ADMINISTRATION... used in washing or to assist in the peeling of fruits and vegetables. Chemicals may be safely used to wash or to assist in the peeling of fruits and vegetables in accordance with the following...

  1. Aircraft measurements over Europe of an air pollution plume from Southeast Asia – aerosol and chemical characterization

    Directory of Open Access Journals (Sweden)

    H. Schlager

    2006-12-01

    Full Text Available An air pollution plume from Southern and Eastern Asia, including regions in India and China, was predicted by the FLEXPART particle dispersion model to arrive in the upper troposphere over Europe on 24–25 March 2006. According to the model, the plume was exported from Southeast Asia only six days earlier, transported into the upper troposphere by a warm conveyor belt, and travelled to Europe in a fast zonal flow. This is confirmed by the retrievals of carbon monoxide (CO from AIRS satellite measurements, which are in excellent agreement with the model results over the entire transport history. The research aircraft DLR Falcon was sent into this plume west of Spain on 24 March and over Southern Europe on 25 March. On both days, the pollution plume was indeed found close to the predicted locations and, thus, the measurements taken allowed the first detailed characterization of the aerosol content and chemical composition of an anthropogenic pollution plume after a nearly hemispheric transport event. The mixing ratios of CO, reactive nitrogen (NOy and ozone (O3 measured in the Asian plume were all clearly elevated over a background that was itself likely elevated by Asian emissions: CO by 17–34 ppbv on average (maximum 60 ppbv and O3 by 2–9 ppbv (maximum 22 ppbv. Positive correlations existed between these species, and a ΔO3/ΔCO slope of 0.25 shows that ozone was formed in this plume, albeit with moderate efficiency. Nucleation mode and Aitken particles were suppressed in the Asian plume, whereas accumulation mode aerosols were strongly elevated and correlated with CO. The suppression of the nucleation mode was likely due to the large pre-existing aerosol surface due to the transported larger particles. Super-micron particles, likely desert dust, were found in part of the Asian pollution plume and also in surrounding cleaner air. The aerosol light absorption coefficient was enhanced in the plume (average values for individual plume

  2. Aircraft measurements over Europe of an air pollution plume from Southeast Asia – aerosol and chemical characterization

    Directory of Open Access Journals (Sweden)

    A. Stohl

    2007-01-01

    Full Text Available An air pollution plume from Southern and Eastern Asia, including regions in India and China, was predicted by the FLEXPART particle dispersion model to arrive in the upper troposphere over Europe on 24–25 March 2006. According to the model, the plume was exported from Southeast Asia six days earlier, transported into the upper troposphere by a warm conveyor belt, and travelled to Europe in a fast zonal flow. This is confirmed by the retrievals of carbon monoxide (CO from AIRS satellite measurements, which are in excellent agreement with the model results over the entire transport history. The research aircraft DLR Falcon was sent into this plume west of Spain on 24 March and over Southern Europe on 25 March. On both days, the pollution plume was found close to the predicted locations and, thus, the measurements taken allowed the first detailed characterization of the aerosol content and chemical composition of an anthropogenic pollution plume after a nearly hemispheric transport event. The mixing ratios of CO, reactive nitrogen (NOy and ozone (O3 measured in the Asian plume were all clearly elevated over a background that was itself likely elevated by Asian emissions: CO by 17–34 ppbv on average (maximum 60 ppbv and O3 by 2–9 ppbv (maximum 22 ppbv. Positive correlations existed between these species, and a ΔO3/ΔCO slope of 0.25 shows that ozone was formed in this plume, albeit with moderate efficiency. Nucleation mode and Aitken particles were suppressed in the Asian plume, whereas accumulation mode aerosols were strongly elevated and correlated with CO. The suppression of the nucleation mode was likely due to the large pre-existing aerosol surface of the transported larger particles. Super-micron particles, likely desert dust, were found in part of the Asian pollution plume and also in surrounding cleaner air. The aerosol light absorption coefficient was enhanced in the plume (average values for individual plume encounters 0.25–0

  3. Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA

    Directory of Open Access Journals (Sweden)

    C. E. Reeves

    2010-03-01

    Full Text Available During June, July and August 2006 five aircraft took part in a campaign over West Africa to observe the aerosol content and chemical composition of the troposphere and lower stratosphere as part of the African Monsoon Multidisciplinary Analysis (AMMA project. These are the first such measurements in this region during the monsoon period. In addition to providing an overview of the tropospheric composition, this paper provides a description of the measurement strategy (flights performed, instrumental payloads, wing-tip to wing-tip comparisons and points to some of the important findings discussed in more detailed in other papers in this special issue.

    The ozone data exhibits an "S" shaped vertical profile which appears to result from significant losses in the lower troposphere due to rapid deposition to forested areas and photochemical destruction in the moist monsoon air, and convective uplift of O3-poor air to the upper troposphere. This profile is disturbed, particularly in the south of the region, by the intrusions in the lower and middle troposphere of air from the Southern Hemisphere impacted by biomass burning. Comparisons with longer term data sets suggest the impact of these intrusions on West Africa in 2006 was greater than in other recent wet seasons. There is evidence for net photochemical production of ozone in these biomass burning plumes as well as in urban plumes, in particular that from Lagos, convective outflow in the upper troposphere and in boundary layer air affected by nitrogen oxide emissions from recently wetted soils. This latter effect, along with enhanced deposition to the forested areas, contributes to a latitudinal gradient of ozone in the lower troposphere. Biogenic volatile organic compounds are also important in defining the composition both for the boundary layer and upper tropospheric convective outflow.

    Mineral dust was found to be the most abundant and ubiquitous aerosol type in the

  4. Chemical characterization of fine particulate matter in Changzhou, China, and source apportionment with offline aerosol mass spectrometry

    Science.gov (United States)

    Ye, Zhaolian; Liu, Jiashu; Gu, Aijun; Feng, Feifei; Liu, Yuhai; Bi, Chenglu; Xu, Jianzhong; Li, Ling; Chen, Hui; Chen, Yanfang; Dai, Liang; Zhou, Quanfa; Ge, Xinlei

    2017-02-01

    Knowledge of aerosol chemistry in densely populated regions is critical for effective reduction of air pollution, while such studies have not been conducted in Changzhou, an important manufacturing base and populated city in the Yangtze River Delta (YRD), China. This work, for the first time, performed a thorough chemical characterization on the fine particulate matter (PM2.5) samples, collected during July 2015 to April 2016 across four seasons in this city. A suite of analytical techniques was employed to measure the organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble inorganic ions (WSIIs), trace elements, and polycyclic aromatic hydrocarbons (PAHs) in PM2.5; in particular, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was deployed to probe the chemical properties of water-soluble organic aerosol (WSOA). The average PM2.5 concentration was found to be 108.3 µg m-3, and all identified species were able to reconstruct ˜ 80 % of the PM2.5 mass. The WSIIs occupied about half of the PM2.5 mass (˜ 52.1 %), with SO42-, NO3-, and NH4+ as the major ions. On average, nitrate concentrations dominated over sulfate (mass ratio of 1.21), indicating that traffic emissions were more important than stationary sources. OC and EC correlated well with each other and the highest OC / EC ratio (5.16) occurred in winter, suggesting complex OC sources likely including both secondary and primary ones. Concentrations of eight trace elements (Mn, Zn, Al, B, Cr, Cu, Fe, Pb) can contribute up to ˜ 5.0 % of PM2.5 during winter. PAH concentrations were also high in winter (140.25 ng m-3), which were predominated by median/high molecular weight PAHs with five and six rings. The organic matter including both water-soluble and water-insoluble species occupied ˜ 21.5 % of the PM2.5 mass. SP-AMS determined that the WSOA had average atomic oxygen-to-carbon (O / C), hydrogen-to-carbon (H / C), nitrogen-to-carbon (N / C), and organic

  5. ELECTROHYDRODYNAMIC DISPERSION OF DEFORMABLE AERO-SOLS IN THE PRESENCE OF AN ELECTRIC FIELD AND CHEMICAL REACTION USING TAYLOR DISPERSION MODEL*

    Institute of Scientific and Technical Information of China (English)

    RUDRAIAH N.; DEVARAJU N.; NG Chiu-On

    2011-01-01

    Under the effects of electric field and chemical reaction, the problem of dispersion of aerosols in a poorly conducting fluid in a channel is solved analytically using the mixture theory together with a regular perturbation technique.It is shown that the aerosols are dispersed relative to a plane moving with the mean speed of atmospheric fluid as well as the mean speed of agglomeration of aerosol with a relative diffusion coefficient, called the Taylor dispersion coefficient.This coefficient is numerically computed and the results reveal that it increases with an increase in the electric number, but decreases with increasing porous parameter.The physical explanations for the phenomena are given in this article.

  6. Chemical analysis of refractory stratospheric aerosol particles collected within the arctic vortex and inside polar stratospheric clouds

    Science.gov (United States)

    Ebert, Martin; Weigel, Ralf; Kandler, Konrad; Günther, Gebhard; Molleker, Sergej; Grooß, Jens-Uwe; Vogel, Bärbel; Weinbruch, Stephan; Borrmann, Stephan

    2016-07-01

    Stratospheric aerosol particles with diameters larger than about 10 nm were collected within the arctic vortex during two polar flight campaigns: RECONCILE in winter 2010 and ESSenCe in winter 2011. Impactors were installed on board the aircraft M-55 Geophysica, which was operated from Kiruna, Sweden. Flights were performed at a height of up to 21 km and some of the particle samples were taken within distinct polar stratospheric clouds (PSCs). The chemical composition, size and morphology of refractory particles were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis. During ESSenCe no refractory particles with diameters above 500 nm were sampled. In total 116 small silicate, Fe-rich, Pb-rich and aluminum oxide spheres were found. In contrast to ESSenCe in early winter, during the late-winter RECONCILE mission the air masses were subsiding inside the Arctic winter vortex from the upper stratosphere and mesosphere, thus initializing a transport of refractory aerosol particles into the lower stratosphere. During RECONCILE, 759 refractory particles with diameters above 500 nm were found consisting of silicates, silicate / carbon mixtures, Fe-rich particles, Ca-rich particles and complex metal mixtures. In the size range below 500 nm the presence of soot was also proven. While the data base is still sparse, the general tendency of a lower abundance of refractory particles during PSC events compared to non-PSC situations was observed. The detection of large refractory particles in the stratosphere, as well as the experimental finding that these particles were not observed in the particle samples (upper size limit ˜ 5 µm) taken during PSC events, strengthens the hypothesis that such particles are present in the lower polar stratosphere in late winter and have provided a surface for heterogeneous nucleation during PSC formation.

  7. Analysis of the sensitivity of thermal infrared nadir satellite observations to the chemical and micro-physical properties of upper tropospheric-lower stratospheric sulphate aerosols

    Science.gov (United States)

    Sellitto, Pasquale; Sèze, Geneviève; Legras, Bernard

    2015-04-01

    Secondary sulphate aerosols are the predominant typology of aerosols in the upper troposphere/lower stratosphere (UTLS), and can have an important impact on radiative transfer and climate, cirrus formation and chemistry in the UTLS. Despite their importance, the satellite observation at the regional scale of sulphate aerosols in the UTLS is limited. In this work, we address the sensitivity of the thermal infrared satellite observations to secondary sulphate aerosols in the UTLS. The absorption properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The absorption coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques : Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) and SEVIRI (Spinning Enhanced Visible and Infrared Imager) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the absorption of idealized aerosol layers, at typical UTLS conditions, on the radiance spectra observed by these simulated satellite instruments. We found a marked spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with absorption peaks at 1170 and 905 cm-1. Micro-windows with a sensitivity to chemical and micro-physical properties of the sulphate aerosol layer are identified, and the role of interfering species, and temperature and water vapour profile is discussed.

  8. Interhemispheric differences in the chemical characteristics of the Indian Ocean aerosol during INDOEX

    Directory of Open Access Journals (Sweden)

    M. Norman

    2002-12-01

    Full Text Available The water soluble inorganic part of the sub-micrometer aerosol was measured from two research vessels over the Indian Ocean during the winter monsoon season (February and March as part of the INDOEX project in 1998 and 1999. Additional measurements were made of gas phase SO2 from one of the vessels in 1999. All samples collected north of the ITCZ were clearly affected by continental, anthropogenic sources. A sharp transition occurred across the ITCZ with concentrations of nss-SO42, NH4+ and nss-K+ being lower by a factor of 7--15, >20 and >40, respectively, on the southern side of the ITCZ. The contribution from DMS to the sub-micrometer nss-SO42 was estimated to be up to 40% in clean air north of the ITCZ but less than 10% in polluted air originating from India. South of the ITCZ virtually all nss-SO42 was likely to be derived from oxidation of DMS. The concentration of chem{SO_2} decreased rapidly with distance from the Indian coast, the ratio SO2nss-SO42 reaching values below 5% after 35 h travel time over the ocean. Surprisingly, MSA, which is derived from DMS, also showed higher concentrations in the sub-micrometer aerosol north of the ITCZ than south of it. This could be explained by the larger sub-micrometer surface area available north of the ITCZ for the condensation of MSA. South of the ITCZ a major part of the MSA was found on the super-micrometer particles. The total amount of MSA, on both sub-micrometer and super-micrometer particles, varied little across the ITCZ. An analysis based on the air trajectories showed that systematic variation in the observed concentrations was associated with variations in the transport from source regions. For example, differences in time since air parcels left the Arabian or Indian coasts was shown to be an important factor for explaining the substantial

  9. Study of the efficiency of chemically assisted enucleation method for handmade cloning in goat (Capra hircus).

    Science.gov (United States)

    Akshey, Y S; Malakar, D; De, A K; Jena, M K; Sahu, S; Dutta, R

    2011-08-01

    The present investigation was carried out to find an efficient chemically assisted procedure for enucleation of goat oocytes related to handmade cloning (HMC) technique. After 22-h in vitro maturation, oocytes were incubated with 0.5 μg/ml demecolcine for 2 h. Cumulus cells were removed by pipetting and vortexing in 0.5 mg/ml hyaluronidase, and zona pellucida were digested with pronase. Oocytes with extrusion cones were subjected to oriented bisection. One-third of the cytoplasm with the extrusion cone was removed with a micro blade. The remaining cytoplasts were used as recipients in HMC. Goat foetal fibroblasts were used as nuclear donors. The overall efficiency measured as the number of cytoplasts obtained per total number of oocytes used was significantly (p < 0.05) higher in chemically assisted handmade enucleation (CAHE) than oriented handmade enucleation without demecolcine (OHE) (80.02 ± 1.292% vs. 72.9 ± 1.00%, respectively, mean ± SEM). The reconstructed and activated embryos were cultured in embryo development medium (EDM) for 7 days. Fusion, cleavage and blastocyst development rate were 71.63 ± 1.95%, 92.94 ± 0.91% and 23.78 ± 3.33% (mean ± SEM), respectively which did not differ significantly from those achieved with random handmade enucleation and OHE. In conclusion, chemically assisted enucleation is a highly efficient and reliable enucleation method for goat HMC which eliminates the need of expensive equipment (inverted fluorescence microscope) and potentially harmful chromatin staining and ultraviolet (UV) irradiation for cytoplast selection.

  10. Physico-chemical characterization of secondary organic aerosol derived from catechol and guaiacol as a model substance for atmospheric humic-like substances

    Directory of Open Access Journals (Sweden)

    J. Ofner

    2010-07-01

    Full Text Available Secondary organic aerosol was produced from the aromatic precursors catechol and guaiacol by reaction with ozone in the presence and absence of simulated sunlight and humidity and investigated for its properties as a proxy for humic-like substances (HULIS. Beside a small particle size, a relatively low molecular weight and typical optical features in the UV/VIS spectral range, HULIS contain a typical aromatic and/or olefinic chemical structure and highly oxidized functional groups within a high chemical diversity. Various methods were used to characterize the secondary organic aerosols obtained: Fourier transform infrared spectroscopy (FTIR demonstrated the formation of different carbonyl containing functional groups as well as structural and functional differences between aerosols formed at different environmental conditions. UV/VIS spectroscopy of filter samples showed that the particulate matter absorbs far into the visible range up to more than 500 nm. Ultrahigh resolved mass spectroscopy (ICR-FT/MS determined O/C-ratios between 0.3 and 1 and main molecular weights between 200 and 500 Da. Temperature-programmed-pyrolysis mass spectroscopy identified carboxylic acids and lactones as major functional groups. Particle sizing using CNC-DMPS demonstrated the formation of small particles during a secondary organic aerosol formation process. Particle imaging using field-emission-gun scanning electron microscopy (FEG-SEM showed spherical particles, forming clusters and chains. Hence, secondary organic aerosols from catechol and guaiacol are appropriate model substances for studies of the processing of aromatic secondary organic aerosols and atmospheric HULIS on the laboratory scale.

  11. Magnetically assisted chemical separation (MACS) process: Preparation and optimization of particles for removal of transuranic elements

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, L.; Kaminski, M.; Bradley, C.; Buchholz, B.A.; Aase, S.B.; Tuazon, H.E.; Vandegrift, G.F. [Argonne National Lab., IL (United States); Landsberger, S. [Univ. of Illinois, Urbana, IL (United States)

    1995-05-01

    The Magnetically Assisted Chemical Separation (MACS) process combines the selectivity afforded by solvent extractants with magnetic separation by using specially coated magnetic particles to provide a more efficient chemical separation of transuranic (TRU) elements, other radionuclides, and heavy metals from waste streams. Development of the MACS process uses chemical and physical techniques to elucidate the properties of particle coatings and the extent of radiolytic and chemical damage to the particles, and to optimize the stages of loading, extraction, and particle regeneration. This report describes the development of a separation process for TRU elements from various high-level waste streams. Polymer-coated ferromagnetic particles with an adsorbed layer of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) diluted with tributyl phosphate (TBP) were evaluated for use in the separation and recovery of americium and plutonium from nuclear waste solutions. Due to their chemical nature, these extractants selectively complex americium and plutonium contaminants onto the particles, which can then be recovered from the solution by using a magnet. The partition coefficients were larger than those expected based on liquid[liquid extractions, and the extraction proceeded with rapid kinetics. Extractants were stripped from the particles with alcohols and 400-fold volume reductions were achieved. Particles were more sensitive to acid hydrolysis than to radiolysis. Overall, the optimization of a suitable NMCS particle for TRU separation was achieved under simulant conditions, and a MACS unit is currently being designed for an in-lab demonstration.

  12. Performance analysis of solar-assisted chemical heat-pump dryer

    Energy Technology Data Exchange (ETDEWEB)

    Fadhel, M.I. [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450, Melaka (Malaysia); Sopian, K.; Daud, W.R.W. [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2010-11-15

    A solar-assisted chemical heat-pump dryer has been designed, fabricated and tested. The performance of the system has been studied under the meteorological conditions of Malaysia. The system consists of four main components: solar collector (evacuated tubes type), storage tank, solid-gas chemical heat pump unit and dryer chamber. A solid-gas chemical heat pump unit consists of reactor, condenser and evaporator. The reaction used in this study (CaCl2-NH{sub 3}). A simulation has been developed, and the predicted results are compared with those obtained from experiments. The maximum efficiency for evacuated tubes solar collector of 80% has been predicted against the maximum experiment of 74%. The maximum values of solar fraction from the simulation and experiment are 0.795 and 0.713, respectively, whereas the coefficient of performance of chemical heat pump (COP{sup h}) maximum values 2.2 and 2 are obtained from simulation and experiments, respectively. The results show that any reduction of energy at condenser as a result of the decrease in solar radiation will decrease the coefficient of performance of chemical heat pump as well as decrease the efficiency of drying. (author)

  13. Review and evaluation of extractants for strontium removal using magnetically assisted chemical separation

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, C.B.; Rogers, R.D. [Northern Illinois Univ., De Kalb, IL (United States). Dept. of Chemistry; Nunez, L.; Ziemer, M.D.; Pleune, T.T.; Vandegrift, G.F. [Argonne National Lab., IL (United States)

    1995-11-01

    A literature review on extractants for strontium removal was initially performed at Northern Illinois University to assess their potential in magnetically assisted chemical separation. A series of potential strontium extractants was systematically evaluated there using radioanalytical methods. Initial experiments were designed to test the uptake of strontium from nitric acid using several samples of magnetic extractant particles that were coated with various crown ether ligands. High partition coefficient (K{sub d}) values for stimulant tank waste were obtained. Further studies demonstrated that the large partitioning was due to uncoated particles.

  14. Chemical properties and origin of dust aerosols in Beijing during springtime

    Institute of Scientific and Technical Information of China (English)

    Renjian Zhang; Zhiwei Han; Tiantao Cheng; Jun Tao

    2009-01-01

    Ground observation of dust aerosols was conducted in Beijing in the spring of 2005 in order to investigate the element composition and origin of mineral dust. Mass concentrations of most mineral elements of particles increased during dust events. Mineral elements were predominant in the sums of total element loadings in both dusty and non-dusty days. Mg, Si, Fe, Al or Ti can be used as an indicator of dust outflow; Cl can be viewed as an evidence of dust particles mixing with anthropogenic emissions. Mineral and pollutant elements showed a bimodal mass particle-size distribution (MSD) in non-dusty days, and a trimodal distribution in dusty days, but their peak concentrations fell in different size stages. Zn and S were mainly enriched in fine particles, whereas Cl was enriched in medium particles, but most mineral elements and Cu were enriched in coarse particles. Mineral elements were dominated by crustal material in dusty even non-dusty days, but pollutant elements were from non-crustal material including local and remote sources. Back trajectory analysis indicated that dust particles in Beijing mainly originated from the Gobi and desert regions of Mongolian and northern China.

  15. Chemical characterization of aerosols at the summit of Mountain Tai in Central East China

    Directory of Open Access Journals (Sweden)

    C. Deng

    2011-07-01

    Full Text Available PM2.5 and TSP samples were collected at the summit of Mountain Tai (MT (1534 m a.s.l. in spring 2006/2007 and summer 2006 to investigate the characteristics of aerosols over central eastern China. For comparison, aerosol samples were also collected at Tazhong, Urumqi, and Tianchi in Xinjiang in northwestern China, Duolun and Yulin in northern China, and two urban sites in the megacities, Beijing and Shanghai, in 2007. Daily mass concentrations of TSP and PM2.5 ranged from 39.6–287.6 μg m−3 and 17.2–235.7 μg m−3 respectively at the summit of MT. Averaged concentrations of PM2.5 showed a pronounced seasonal variation with higher concentration in summer than spring. 17 water-soluble ions (SO42−, NO3, Cl, F, PO43−, NO2, CH3COO, CH2C2O42−, C2H4C2O42−, HCOO, MSA, C2O42−, NH4+, Ca2+, K+, Mg2+, Na+, and 19 elements of all samples were measured. SO42−, NO3, and NH4+ were the major water-soluble species in PM2.5, accounting for 61.50 % and 72.65 % of the total measured ions in spring and summer, respectively. The average ratio of PM2.5/TSP was 0.37(2006 and 0.49(2007 in spring, while up to 0.91 in summer, suggesting that aerosol particles were primarily comprised of fine particles in summer and of considerable coarse particles in spring. Crustal elements (e.g., Ca, Mg, Al, Fe, etc. showed higher concentration in spring than summer, while most of the pollution species (SO42−, NO3, K

  16. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

    Science.gov (United States)

    Van Wyngarden, A L; Pérez-Montaño, S; Bui, J V H; Li, E S W; Nelson, T E; Ha, K T; Leong, L; Iraci, L T

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and (1)H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  17. Non-refractory PM1 in SE Asia: Chemically speciated aerosol fluxes and concentrations above contrasting land-uses in SE Asia.

    Science.gov (United States)

    Phillips, Gavin; Farmer, Delphine; di Marco, Chiara; Misztal, Pawel; Sueper, Donna; Kimmel, Joel; Jimenez, Jose; Fowler, David; Nemitz, Eiko

    2010-05-01

    New measurements of VOC emissions (measured with leaf cuvettes, and ecosystem fluxes obtained from eddy covariance measurements) suggest that oil palm (Elaeis guineensis Jacq) is a significantly larger source of isoprene than tropical forest, in Borneo. These larger sources of isoprene measured over oil palm, allied with a larger anthropogenic component of local emissions, contrasts with the composition of the atmosphere in the semi-remote tropical forest environment. The difference in the atmospheric composition above different land-uses has the potential to lead to contrasting chemistry and physics controlling the formation and processing of particulate matter. Thus land use changes, driven by the economics of biofuels, could give rise to rapidly changing chemical and aerosol regimes in the tropics. It is therefore important to understand the current emissions, chemical processing and composition of organic aerosol over both (semi-)natural and anthropogenic land uses in the tropical environment. Ecosystem flux measurements of chemically-speciated non-refractory PM1 were made over two contrasting land uses in the Malaysian state of Sabah, on the island of Borneo during 2008. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed at the Global Atmospheric Watch (GAW) site at a tropical rain forest location as well as the Sabahmas (PPB OIL) oil palm plantation near Lahad Datu, in Eastern Sabah, as a collaboration between three UK NERC funded projects (OP3, APPRAISE/ACES and DIASPORA). Recent technical developments using ToF detectors allow us to record 10 Hz full mass spectra at both high resolution (HR) and unit-mass resolution (UMR), suitable for the calculation of local eddy-covariance fluxes. The measurements provide information on the deposition rate of anthropogenic aerosol components (e.g. sulphate, nitrate, ammonium and hydrocarbon-like aerosol) to tropical forest and oil palm. At the same time, any biogenic secondary organic

  18. Chemicals loading in acetylated bamboo assisted by supercritical CO2 based on phase equilibrium data

    Science.gov (United States)

    Silviana, Petermann, M.

    2015-12-01

    Indonesia has a large tropical forest. However, the deforestation still appears annually and vastly. This reason drives a use of bamboo as wood alternative. Recently, there are many modifications of bamboo in order to prolong the shelf life. Unfortunately, the processes need more chemicals and time. Based on wood modification, esterifying of bamboo was undertaken in present of a dense gas, i.e. supercritical CO2. Calculation of chemicals loading referred to ASTM D1413-99 by using the phase equilibrium data at optimum condition by a statistical design. The results showed that the acetylation of bamboo assisted by supercritical CO2 required 14.73 kg acetic anhydride/m3 of bamboo for a treatment of one hour.

  19. Metal-assisted chemical etching of CIGS thin films for grain size analysis

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Chaowei [Research and Development Centre, Hanergy Thin Film Power Group Limited, Chengdu (China); Loi, Huu-Ha; Duong, Anh; Parker, Magdalena [Failure Analysis Department, MiaSole Hi-Tech Corp., Santa Clara, CA (United States)

    2016-09-15

    Grain size of the CIGS absorber is an important monitoring factor in the CIGS solar cell manufacturing. Electron backscatter diffraction (EBSD) analysis is commonly used to perform CIGS grain size analysis in the scanning electron microscope (SEM). Although direct quantification on SEM image using the average grain intercept (AGI) method is faster and simpler than EBSD, it is hardly applicable on CIGS thin films. The challenge is that, not like polycrystalline silicon, to define grain boundaries by selective chemical etching is not easily realizable for the multi-component CIGS alloy. In this Letter, we present direct quantification of CIGS thin film grain size using the AGI method by developing metal-assisted wet chemical etching process to define CIGS grain boundaries. The calculated value is similar to EBSD result. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Microwave assisted conversion of microcrystalline cellulose into value added chemicals using dilute acid catalyst.

    Science.gov (United States)

    Ching, Teck Wei; Haritos, Victoria; Tanksale, Akshat

    2017-02-10

    One of the grand challenges of this century is to transition fuels and chemicals production derived from fossil feedstocks to renewable feedstocks such as cellulosic biomass. Here we describe fast microwave conversion of microcrystalline cellulose (MCC) in water, with dilute acid catalyst to produce valuable platform chemicals. Single 10min microwave assisted treatment was able to convert >60% of MCC, with >50mol% yield of desirable products such as glucose, HMF, furfural and levulinic acid. Recycling of residual MCC with make-up fresh MCC resulted in an overall conversion of >93% after 5 cycles while maintaining >60% conversion in each cycle. Addition of isopropanol (70%v/v) as a co-solvent increased the yields of HMF and levulinic acid. This work shows for the first time proof of concept for complete conversion of recalcitrant microcrystalline cellulose in mild conditions of low temperature, dilute acid and short residence time using energy efficient microwave technology.

  1. Chemical composition and sources of ambient aerosol in an urban environment over Athens, Greece: Case study on the role of wintertime biomass burning

    Science.gov (United States)

    Theodosi, Christina

    2016-04-01

    This study examines the chemical composition of aerosols over the Greater Athens Area (GAA). To achieve this, particulate matter sampling has been conducted on a 6h-24h basis and more than 700 aerosol samples were collected at downtown Athens, in Thissio from January 2013 to December 2015. All samples, after mass quantification, were analyzed for major anions (Cl^-, Br^-, NO{_3^-}, SO{_4-2}, PO{_4-3}, C_2O{_4-2}), cations (NH{_4^+}, K^+, Na^+, Mg+2, Ca+2), trace elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, V, Zn, Mn, Ni, Pb, P, S, Sb), organic carbon (OC) and elemental carbon (EC). Aerosol chemical mass closure calculations indicated that carbonaceous aerosol constitutes a major component, along with nitrate and sulfate anions, dust, cations and EC. Moreover, during the winter periods of December 2012-January 2013 and December 2013-January 2014, air pollution due to excessive use of biomass for domestic heating has been reported as a major environmental problem in the area. To assess the importance of biomass burning as a source of air pollution over the GAA three main sugars specific biomass burning tracers (levoglucosan, mannosan and galactosan) and Polycyclic aromatic hydrocarbons (PAHs) were also analyzed during the winter period. Acknowledgments This work was supported by the State Scholarship Foundation ("IKY Fellowships of Excellence for Postgraduate Studies in Greece - Siemens Programme") in the framework of the Hellenic Republic-Siemens Settlement Agreement.

  2. Chemical composition and optical properties of aerosols in the lower mixed layer and the free troposphere. Final report of the AFS project; Chemische Zusammensetzung und optische Eigenschaften des Aerosols in der freien Troposphaere. Abschlussbericht zum AFS-Projekt

    Energy Technology Data Exchange (ETDEWEB)

    Asseng, H. [Freie Univ. Berlin (Germany). Inst. fuer Weltraumwissenschaften]|[Max-Planck-Institut fuer Chemie, Mainz (Germany). Abt. Biogeochemie; Fischer, J. [Freie Univ. Berlin (Germany). Inst. fuer Weltraumwissenschaften; Helas, G. [Max-Planck-Institut fuer Chemie, Mainz (Germany). Abt. Biogeochemie; Weller, M. [Deutscher Wetterdienst, Potsdam (Germany). Meteorologisches Observatorium

    2001-08-02

    Aerosol radiative forcing is the largest unknown in current climate models and, as a result, in predicting future climate. Accurate vertically-resolved measurements of aerosol optical properties are an important element of improved climate prediction (IPCC). The present project has contributed to this objective. Jets of directly and remotely determined radiation data have been provided suitable to cut down the uncertainty of column- or layer related optical aerosol parameters. In the present case mean values and profiles of spectral scattering - and absorption coefficients have been retrieved from ground based and airborne sky-radiance/solar irradiance measurements. Available analyses of size and chemical composition of sampled particles (adjoined projects) have been also taken into consideration. The retrieved parameters have served as an input for modelling the radiative transfer exactly for the real time of measurements. Closure procedures yielded finally realistic spectral scattering - and absorption coefficients typically for the lower troposphere in a mostly rural Central European region. (orig.) [German] Die ungenuegende Kenntnis strahlungswirksamer, optischer Aerosolparameter ist laut IPCC die groesste Unbekannte bei der Modellierung des Klimas und seiner Veraenderung. Wissenschaft und Technik bemuehen sich in sog. Schliessungsexperimenten aus der Ueberbestimmung direkt und indirekt gemessener Aerosolparameter genaue(re) Kenntnis (Mittelwert/Variation) ueber deren Klimawirksamkeit zu erlangen. Im vorliegenden Projekt wurden aus verschiedenen passiven, spektralen Messungen von Streulicht und Transmission der Atmosphaere in verschiedenen Hoehen sowie aus der Beruecksichtigung von Partikelanalysen Dritter, Streu- und Absorptionskoeffizienten des Aerosols der gesamten Luftsaeule und in vertikaler Aufloesung abgeleitet. Strahlungstransportmodellierungen mit den gewonnenen Aerosolparametern als input engten ueber den Vergleich mit den Messungen deren Grad an

  3. Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA

    Directory of Open Access Journals (Sweden)

    C. E. Reeves

    2010-08-01

    Full Text Available During June, July and August 2006 five aircraft took part in a campaign over West Africa to observe the aerosol content and chemical composition of the troposphere and lower stratosphere as part of the African Monsoon Multidisciplinary Analysis (AMMA project. These are the first such measurements in this region during the monsoon period. In addition to providing an overview of the tropospheric composition, this paper provides a description of the measurement strategy (flights performed, instrumental payloads, wing-tip to wing-tip comparisons and points to some of the important findings discussed in more detail in other papers in this special issue.

    The ozone data exhibits an "S" shaped vertical profile which appears to result from significant losses in the lower troposphere due to rapid deposition to forested areas and photochemical destruction in the moist monsoon air, and convective uplift of ozone-poor air to the upper troposphere. This profile is disturbed, particularly in the south of the region, by the intrusions in the lower and middle troposphere of air from the southern hemisphere impacted by biomass burning. Comparisons with longer term data sets suggest the impact of these intrusions on West Africa in 2006 was greater than in other recent wet seasons. There is evidence for net photochemical production of ozone in these biomass burning plumes as well as in urban plumes, in particular that from Lagos, convective outflow in the upper troposphere and in boundary layer air affected by nitrogen oxide emissions from recently wetted soils. This latter effect, along with enhanced deposition to the forested areas, contributes to a latitudinal gradient of ozone in the lower troposphere. Biogenic volatile organic compounds are also important in defining the composition both for the boundary layer and upper tropospheric convective outflow.

    Mineral dust was found to be the most abundant and ubiquitous aerosol type in the

  4. Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP: linking condensation, evaporation and chemical reactions of organics, oxidants and water

    Directory of Open Access Journals (Sweden)

    M. Shiraiwa

    2011-12-01

    Full Text Available We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007, and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds.

    In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity. Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the

  5. Chemometrics-assisted spectrophotometry method for the determination of chemical oxygen demand in pulping effluent.

    Science.gov (United States)

    Chen, Honglei; Chen, Yuancai; Zhan, Huaiyu; Fu, Shiyu

    2011-04-01

    A new method has been developed for the determination of chemical oxygen demand (COD) in pulping effluent using chemometrics-assisted spectrophotometry. Two calibration models were established by inducing UV-visible spectroscopy (model 1) and derivative spectroscopy (model 2), combined with the chemometrics software Smica-P. Correlation coefficients of the two models are 0.9954 (model 1) and 0.9963 (model 2) when COD of samples is in the range of 0 to 405 mg/L. Sensitivities of the two models are 0.0061 (model 1) and 0.0056 (model 2) and method detection limits are 2.02-2.45 mg/L (model 1) and 2.13-2.51 mg/L (model 2). Validation experiment showed that the average standard deviation of model 2 was 1.11 and that of model 1 was 1.54. Similarly, average relative error of model 2 (4.25%) was lower than model 1 (5.00%), which indicated that the predictability of model 2 was better than that of model 1. Chemometrics-assisted spectrophotometry method did not need chemical reagents and digestion which were required in the conventional methods, and the testing time of the new method was significantly shorter than the conventional ones. The proposed method can be used to measure COD in pulping effluent as an environmentally friendly approach with satisfactory results.

  6. Hygroscopicity Behavior, Activation Properties and Chemical Composition of Atmospheric Aerosol at a Background Site in the Megacity Region of Peking

    Science.gov (United States)

    Henning, Silvia; Nowak, Andreas; Mildenberger, Katrin; Göbel, Tina; Nekat, Bettina; van Pinxteren, Dominik; Herrmann, Hartmut; Zhao, Chunsheng; Wiedensohler, Alfred; Stratmann, Frank

    2010-05-01

    Large areas of China suffer from heavy air pollution (both gaseous and particulate) caused by strong economic growth in the last two decades. However, knowledge concerning the physical and chemical properties of the resulting aerosol particles populations, and their effects on the optical properties of the atmosphere, is still sparse. In the framework of the investigations presented here, comprehensive measurements concerning aerosol particle hygroscopicity, CCN ability, composition, and optical properties were performed. The investigations are part of the DFG-funded project HaChi (Haze in China) and are conducted in collaboration with the Peking University. A conclusive parameterization of aerosol hygroscopicity and activation data is aimed for, which will then be implemented in a meso-scale model to investigate aerosol-cloud-radiation and precipitation interactions. During two intensive measurements campaigns (March 2009 and July/ August 2009), in-situ aerosol measurements have been performed in an air-conditioned mobile laboratory next to the Wuqing Meteorological Station (39°23'8.53"N, 117°1'25.88"E), which is located between Bejing and Tijanjin and is thereby an ideal background site in a megacity region. The particle number size distribution (TDMPS), the particle optical properties (MAAP and nephelometer) and their hygroscopic properties at high RH (HH-TDMA, LACIS-mobile) were characterized as well as their cloud nucleating properties above supersaturation (DMT-CCNC). 24 h PM1 particle samples were continuously collected over the two campaigns in winter and summer using a DIGITEL high volume sampler (DHA-80). Additionally two 6h size-resolved samples (daytime and night-time) were collected each day applying an 11-stage Berner impactor. The size-selection of HH-TDMA, LACIS and the CCNC was synchronized with the Berner stages. Opening analysis of the winter campaign data showed that the HH-TDMA usually detected a hydrophobic and a hygroscopic mode, i.e., the

  7. Neutralization of Aerosolized Bio-Agents by Filled Nanocomposite Materials through Thermal and Chemical Inactivation Mechanisms

    Science.gov (United States)

    2016-06-01

    Inorganic chemistry , San Diego, Calif. : Berlin: Academic Press, W. de Gruyter, 2001, p.^pp. 930. S. Zhang; M. Schoenitz; E. L. Dreizin, Journal of...and oxide chemistry , 2013; American Chemical Society: 2013; pp FLUO-22. Z. Doorenbos; J. Puszynski; D. Kapoor in: The effect of particle morphology...Physical Chemistry C 114 (46) (2010a) 19653-19659 10.1021/jp108171k. S. Zhang; M. Schoenitz; E. L. Dreizin, Journal of Physics and Chemistry of Solids 71

  8. Size Distribution and Chemical Characteristic of Aerosols in Northwestern Black Sea Region of Turkey

    Science.gov (United States)

    Oztürk, Fatma; Keles, Melek; Halif Ngagine, Soulemane

    2016-04-01

    Size segregated PM samples were collected at the city center of Bolu, which is northwestern part of the Black Sea region of Turkey between 2015 and 2016. A cascade impactor was used for the collection of weekly PM samples on pre-fired quartz filters in eight different size ranges (9.0-10.0 μm, 5.8-9.0 μm, 4.7-5.8 μm, 3.3-4.7 μm, 2.1-3.3 μm, 1.1-2.1 μm, 0.65-1.1 μm, 0.43-0.65 μm). The collected samples were divided in three parts and each part was analyzed with different analytical technique. The first part of the filter was analyzed in terms of major ions (SO42-, NO3-, Cl-, NH4+, K+, Ca2+, Mg2+, Na+). A large suit of metals from Li to U were determined in the second fraction of the filter by means of ICPMS. Lastly, the third part of the filter was analyzed in terms of EC and OC. The preliminary results indicated that the PM mass depicted bimodal distribution and the average concentration of PM10 was about 100 μg/m3for a five week period. Both EC and OC showed bi-modal distribution while these two parameters were more enriched on smaller particles. The average concentrations of EC and OC in PM1 were determined as 4.1 and 40.6 μg/m3, respectively, indicating the secondary organic aerosol formation in Bolu ambient air. Among the major ions, SO42- and NH4+ depicted unimodal distribution having significantly higher concentrations in fine particles (< 1 μm) while the rest of the ions present bimodal distribution. Mass closure analysis will be applied to the generated data set and sources will be evaluated by applying PMF. This project was supported financially by Turkish Scientific and Technological Research Council (TÜBİTAK) with a project number 114Y429.

  9. Chemical Composition of Summertime PM_(2.5) and Its Relationship to Aerosol Optical Properties in Guangzhou,China

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Urban aerosols have a large effect on the deterioration of air quality and the degradation of atmospheric visibility.Characterization of the chemical composition of PM 2.5 and in situ measurements of the optical properties of aerosols were conducted in July 2008 at an urban site in Guangzhou,Southern China.The mean PM 2.5 concentration for the entire period was 53.7±23.2 μg m 3.The mean PM 2.5 concentration (82.7±25.4 μg m 3) on hazy days was roughly two times higher than that on clear days (38.8±8.7 μg m 3).The total water-soluble ion species and the total average carbon accounted for 47.9%±4.3% and 35.2%±4.5%,respectively,of the major components of PM 2.5.The increase of secondary and carbonaceous aerosols,in particular ammonium sulfate,played an important role in the formation of haze pollution.The mean absorption and scattering coefficients and the single scattering albedo over the whole period were 53±20 M m 1,226±111 M m 1,and 0.80±0.04,respectively.PM 2.5 had a high linear correlation with the aerosol extinction coefficient,elemental carbon (EC) was correlated with aerosol absorption,and organic carbon (OC) and SO 4 2 were tightly linked to aerosol scattering.

  10. The application of single particle aerosol mass spectrometry for the detection and identification of high explosives and chemical warfare agents

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Audrey Noreen [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2006-01-01

    Single Particle Aerosol Mass Spectrometry (SPAMS) was evaluated as a real-time detection technique for single particles of high explosives. Dual-polarity time-of-flight mass spectra were obtained for samples of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN); peaks indicative of each compound were identified. Composite explosives, Comp B, Semtex 1A, and Semtex 1H were also analyzed, and peaks due to the explosive components of each sample were present in each spectrum. Mass spectral variability with laser fluence is discussed. The ability of the SPAMS system to identify explosive components in a single complex explosive particle (~1 pg) without the need for consumables is demonstrated. SPAMS was also applied to the detection of Chemical Warfare Agent (CWA) simulants in the liquid and vapor phases. Liquid simulants for sarin, cyclosarin, tabun, and VX were analyzed; peaks indicative of each simulant were identified. Vapor phase CWA simulants were adsorbed onto alumina, silica, Zeolite, activated carbon, and metal powders which were directly analyzed using SPAMS. The use of metal powders as adsorbent materials was especially useful in the analysis of triethyl phosphate (TEP), a VX stimulant, which was undetectable using SPAMS in the liquid phase. The capability of SPAMS to detect high explosives and CWA simulants using one set of operational conditions is established.

  11. Photodegradation of secondary organic aerosol generated from limonene oxidation by ozone studied with chemical ionization mass spectrometry

    Directory of Open Access Journals (Sweden)

    X. Pan

    2009-02-01

    Full Text Available Photodegradation of secondary organic aerosol (SOA prepared by ozone-initiated oxidation of D-limonene is studied with an action spectroscopy approach, which relies on detection of volatile photoproducts with chemical ionization mass-spectrometry as a function of the UV irradiation wavelength. Efficient photodegradation is observed for a broad range of ozone and D-limonene concentrations (0.1–300 ppm used in the preparation of SOA. The observed photoproducts are dominated by oxygenated C1-C3 compounds such as methanol, formic acid, acetaldehyde, acetic acid, and acetone. The irradiation wavelength dependence of the combined yield of the photoproducts closely tracks the absorption spectrum of the SOA material suggesting that photodegradation is not limited to the UV wavelengths. Kinetic simulations suggest that RO2+HO2/RO2 reactions represent the dominant route to photochemically active carbonyl and peroxide species in the limonene SOA material. Similar photodegradation processes are likely to occur in realistic SOA produced by OH- or O3-initiated oxidation of biogenic volatile organic compounds in clean air.

  12. Photodegradation of secondary organic aerosol generated from limonene oxidation by ozone studied with chemical ionization mass spectrometry

    Directory of Open Access Journals (Sweden)

    X. Pan

    2009-06-01

    Full Text Available Photodegradation of secondary organic aerosol (SOA prepared by ozone-initiated oxidation of D-limonene is studied with an action spectroscopy approach, which relies on detection of volatile photoproducts with chemical ionization mass-spectrometry as a function of the UV irradiation wavelength. Efficient photodegradation is observed for a broad range of ozone (0.1–300 ppm and D-limonene (0.02–3 ppm concentrations used in the preparation of SOA. The observed photoproducts are dominated by oxygenated C1-C3 compounds such as methanol, formic acid, acetaldehyde, acetic acid, and acetone. The irradiation wavelength dependence of the combined yield of the photoproducts closely tracks the absorption spectrum of the SOA material suggesting that photodegradation is not limited to the UV wavelengths. Kinetic simulations suggest that RO2+HO2/RO2 reactions represent the dominant route to photochemically active carbonyl and peroxide species in the limonene SOA prepared in these experiments. Similar photodegradation processes are likely to occur in realistic SOA produced by OH- or O3-initiated oxidation of biogenic volatile organic compounds in clean air.

  13. Using the chemical equilibrium partitioning space to explore factors influencing the phase distribution of compounds involved in secondary organic aerosol formation

    OpenAIRE

    F. Wania; Lei, Y. D.; Wang, C.; Abbatt, J. P. D.; Goss, K.-U.

    2015-01-01

    Many atmospheric and chemical variables influence the partitioning equilibrium between gas phase and condensed phases of compounds implicated in the formation of secondary organic aerosol (SOA). The large number of factors and their interaction makes it often difficult to assess their relative importance and concerted impact. Here we introduce a two-dimensional space which maps regions of dominant atmospheric phase distribution within a coordinate system defined by equilibri...

  14. Using the chemical equilibrium partitioning space to explore factors influencing the phase distribution of compounds involved in secondary organic aerosol formation

    OpenAIRE

    F. Wania; Lei, Y. D.; Wang, C.; Abbatt, J. P. D.; K.-U. Goss

    2014-01-01

    Many atmospheric and chemical variables influence the partitioning equilibrium between gas phase and condensed phases of compounds implicated in the formation of secondary organic aerosol (SOA). The large number of factors and their interaction makes it often difficult to assess their relative importance and concerted impact. Here we introduce a two-dimensional space, which maps regions of dominant atmospheric phase distribution within a coordinate system de...

  15. The chemical composition of aerosols from Wildland fires: Current state of the science and possible new directions.

    Science.gov (United States)

    Wildland fire emits a substantial quantity of aerosol to the atmosphere. These aerosols typically comprise a complex mixture of organic matter and refractory elemental or black carbon with a relatively minor contribution of inorganic matter from soils and plant micronutrients. Id...

  16. Chemical Composition of Gas Phase and Secondary Organic Aerosol from Aromatic Precursors Produced in a Smog Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Sax, M. [ETH Zuerich and PSI (Switzerland); Kalberer, M. [ETH Zuerich (Switzerland); Zenobi, R. [ETH Zuerich (Switzerland); Paulsen, D.; Baltensperger, U.

    2004-03-01

    Reaction products formed during photooxidation of aromatic compounds contribute to secondary organic aerosol (SOA) mass. In this study we performed experiments with 1,3,5-trimethylbenzene (135TMB) in the PSI smog chamber to study the formation and composition of SOA. We used different techniques to analyze the aerosol and the gas phase. (author)

  17. Study of the correlation between columnar aerosol burden, suspended matter at ground and chemical components in a background European environment

    Science.gov (United States)

    EstelléS, VíCtor; MartíNez-Lozano, José A.; Pey, Jorge; Sicard, MichaëL.; Querol, Xavier; Esteve, Anna R.; Utrillas, MaríA. P.; Sorribas, Mar; Gangoiti, Gotzon; Alastuey, AndréS.; Rocadenbosch, Francesc

    2012-02-01

    Although routinely monitored by ground based air quality networks, the particulate matter distribution could be eventually better described with remote sensing techniques. However, valid relationships between ground level and columnar ground based quantities should be known beforehand. In this study we have performed a comparison between particulate matter measurements at ground level at different cut sizes (10, 2.5 and 1.0 μm), and the aerosol optical depth obtained by means of a ground based sunphotometer during a multiinstrumental field campaign held in El Arenosillo (Huelva, Spain) from 28 June to 4 July 2006. All the PM fractions were very well correlated with AOD with correlation coefficients that ranged from 0.71 to 0.81 for PM10, PM2.5 and PM1. Furthermore, the influence of the mixing layer height in the correlations was explored. The improvement in the correlation when the vertical distribution is taken into account was significant for days with a homogeneous mixing layer. Moreover, the chemical analysis of the individual size fractions allowed us to study the origin of the particulate matter. Secondary components were the most abundant and also well correlated in the three size fractions; but for PM10 fraction, chemical species related to marine origin were best correlated. Finally, we obtained a relationship between MODIS L3 AOD from collection 5.1 and the three PM cut sizes. In spite of being a relatively clean environment, all the techniques were able to capture similar day to day variations during this field campaign.

  18. Modeling Multiphase Chemical Kinetics of OH Radical Reacting with Biomass Burning Organic Aerosol

    Science.gov (United States)

    Arangio, Andrea; Slade, Jonathan H.; Berkemeier, Thomas; Knopf, Daniel A.; Shiraiwa, Manabu

    2014-05-01

    Levoglucosan, abietic acid and nitroguaiacol are commonly used as molecular tracers of biomass burning in source apportionment. Recent studies have demonstrated the decay of levoglucosan when the particles were exposed to atmospherically relevant concentration of OH radicals [1-3]. However, multiphase chemical kinetics of OH radical reacting with such compounds has not fully understood. Here we apply the kinetic multi-layer model for gas-particle interactions (KM-GAP) [4] to experimental data of OH exposure to levoglucosan, abietic acid and nitroguaiacol [1]. KM-GAP resolves the following mass transport and chemical reactions explicitly: gas-phase diffusion, reversible surface adsorption, surface reaction, surface-bulk transport, bulk diffusion and reaction. The particle shrink due to the evaporation of volatile reaction products is also considered. The time- and concentration-dependence of reactive uptake coefficient of OH radicals were simulated by KM-GAP. The measured OH uptake coefficients were fitted by a Monte Carlo (MC) filtering coupled with a genetic algorithm (GA) to derive physicochemical parameters such as bulk diffusion coefficient, Henry's law coefficient and desorption lifetime of OH radicals. We assessed the relative contribution of surface and bulk reactions to the overall uptake of OH radicals. Chemical half-life and the evaporation time scale of these compounds are estimated in different scenarios (dry, humid and cloud processing conditions) and at different OH concentrations. REFERENCES [1] J. H. Slade, D. A. Knopf, Phys. Chem. Chem. Phys., 2013, 15, 5898. [2] S. H. Kessler, J. D. Smith, D.L. Che, D.R. Worsnop, K. R. Wilson, J. H. Kroll, Environ. Sci. Technol., 2010, 44, 7005. [3] C. J. Hennigan, A. P. Sullivan, J. L. Collett Jr, A. L. Robinson, Geophys. Res. Lett., 2010, 37, L09806. [4] M. Shiraiwa, C. Pfrang, T. Koop, U. Pöschl, Atmos. Chem. Phys, 2012, 12, 2777.

  19. Traffic-generated changes in the chemical characteristics of size-segregated urban aerosols.

    Science.gov (United States)

    Rogula-Kozłowska, Wioletta

    2014-10-01

    The road traffic impact on the concentrations of 13 fractions of particulate matter (PM) and their components was assessed. PM was sampled at two points in Katowice (southern Poland), a background point beyond the effects of road traffic, and a near-highway traffic point. The samples were analyzed for organic and elemental carbon, 8 water-soluble ions, 24 elements, and 16 polycyclic aromatic hydrocarbons (PAHs). The traffic emissions (mainly particles from car exhaust) enriched the ultrafine, submicron, and fine PM particles with elemental carbon. The traffic-caused re-suspension of the road and soil dust affecting the concentrations and chemical composition of the coarse PM fraction. However, for each PM fraction, the carcinogenic equivalent ratios, assumed as a measure of the hazard from 16 PAHs in this paper, were similar at the two sampling points. The traffic emissions from the highway appeared to have a weaker influence on the concentrations and chemical composition of PM in a typical urban area of southern Poland than elsewhere in Europe.

  20. Program of technical assistance to the organization for the prohibition of chemical weapons, informal report

    Energy Technology Data Exchange (ETDEWEB)

    1995-01-01

    Currently, U.S. organizations provide technical support to the U.S. Delegation for its work as part of the Preparatory Commission (PrepCom) of the Organization for the Prohibition of Chemical Weapons (OPCW) in The Hague. The current efforts of the PrepCom are focussed on preparations for the Entry-Into-Force (EIF) of the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons (often referred to as the {open_quotes}Chemical Weapons Convention{close_quotes} (CWC)). EIF of the CWC is expected in 1995, and shortly thereafter the PrepCom will cease to exist, with the OPCW taking over responsibilities under the CWC. A U.S. program of technical assistance to the OPCW for its verification responsibilities may be created as part of U.S. policy objectives after EIF of the CWC. In the summary below, comments by participants are presented in Square Brackets Some of the same points arose several times during the discussions; they are grouped together under the most pertinent heading.

  1. Deep and vertical silicon bulk micromachining using metal assisted chemical etching

    Science.gov (United States)

    Zahedinejad, Mohammad; Delaram Farimani, Saeed; Khaje, Mahdi; Mehrara, Hamed; Erfanian, Alireza; Zeinali, Firooz

    2013-05-01

    In this paper, a newfound and simple silicon bulk micromachining process based on metal-assisted chemical etching (MaCE) is proposed which opens a whole new field of research in MEMS technology. This method is anisotropic and by controlling the etching parameters, deep vertical etching, relative to substrate surface, can be achieved in micrometer size for oriented Si wafer. By utilizing gold as a catalyst and a photoresist layer as the single mask layer for etching, 60 µm deep gyroscope micromachined structures have been fabricated for 2 µm features. The results indicate that MaCE could be the only wet etching method comparable to conventional dry etching recipes in terms of achievable etch rate, aspect ratio, verticality and side wall roughness. It also does not need a vacuum chamber and the other costly instruments associated with dry etching techniques.

  2. Microwave-Assisted Chemical Functionalization of Single-Walled Carbon Nanotubes with Organic Peroxides

    Institute of Scientific and Technical Information of China (English)

    WAN Li; WANG Xianbao; LI Shaoqing; LI Qin; TIAN Rong; LI Mingjian; CHENG Jing

    2009-01-01

    Microwave-assisted chemical functionalization of single-walled carbon nanotubes, with undecyl groups de-composed from lauroyl peroxides was reported. This rapid efficient procedure reduced the reaction time to 10 min, and obtained the products with higher functionalized degree than that by the conventional refluxing method. The in-fluence of different reaction time and microwave power on the functionalized degree has been explored by using FT-IR, TGA and Raman analyses. The results show that longer treatment time will lead to partial defunctionaliza-tion, and higher microwave power (higher than 900 W) can reduce the functionalized degree by removing some ini-tially-attached functional groups. Dispersion stability images and HRTEM images show that the resulting SWNT has enhanced dispersivity in organic solvents compared to the pristine nanotubes.

  3. Low temperature metal free growth of graphene on insulating substrates by plasma assisted chemical vapor deposition

    Science.gov (United States)

    Muñoz, R.; Munuera, C.; Martínez, J. I.; Azpeitia, J.; Gómez-Aleixandre, C.; García-Hernández, M.

    2017-03-01

    Direct growth of graphene films on dielectric substrates (quartz and silica) is reported, by means of remote electron cyclotron resonance plasma assisted chemical vapor deposition r-(ECR-CVD) at low temperature (650 °C). Using a two step deposition process- nucleation and growth- by changing the partial pressure of the gas precursors at constant temperature, mostly monolayer continuous films, with grain sizes up to 500 nm are grown, exhibiting transmittance larger than 92% and sheet resistance as low as 900 Ω sq-1. The grain size and nucleation density of the resulting graphene sheets can be controlled varying the deposition time and pressure. In additon, first-principles DFT-based calculations have been carried out in order to rationalize the oxygen reduction in the quartz surface experimentally observed. This method is easily scalable and avoids damaging and expensive transfer steps of graphene films, improving compatibility with current fabrication technologies.

  4. Nanocrystalline Diamond Films Deposited by Electron Assisted Hot Filament Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nanocrystalline diamond films were deposited on polished Si wafer surface with electron assisted hot filament chemical vapor deposition at 1 kPa gas pressure, the deposited films were characterized and observed by Raman spectrum, X-ray diffraction, atomic force microscopy and semiconductor characterization system. The results show that when 8 A bias current is applied for 5 h, the surface roughness decreases to 28.5 nm. After 6 and 8 A bias current are applied for 1 h, and the nanocrystalline films deposition continue for 4 h with 0 A bias current at 1 kPa gas pressure. The nanocrystalline diamond films with 0.5×109 and 1×1010 Ω·cm resistivity respectively are obtained. It is demonstrated that electron bombardment plays an important role of nucleation to deposit diamond films with smooth surface and high resistivity.

  5. Plasma Assisted Chemical Vapour Deposition – Technological Design Of Functional Coatings

    Directory of Open Access Journals (Sweden)

    Januś M.

    2015-06-01

    Full Text Available Plasma Assisted Chemical Vapour Deposition (PA CVD method allows to deposit of homogeneous, well-adhesive coatings at lower temperature on different substrates. Plasmochemical treatment significantly impacts on physicochemical parameters of modified surfaces. In this study we present the overview of the possibilities of plasma processes for the deposition of diamond-like carbon coatings doped Si and/or N atoms on the Ti Grade2, aluminum-zinc alloy and polyetherketone substrate. Depending on the type of modified substrate had improved the corrosion properties including biocompatibility of titanium surface, increase of surface hardness with deposition of good adhesion and fine-grained coatings (in the case of Al-Zn alloy and improving of the wear resistance (in the case of PEEK substrate.

  6. Bilayer–metal assisted chemical etching of silicon microwire arrays for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    R. W. Wu

    2016-02-01

    Full Text Available Silicon microwires with lateral dimension from 5 μm to 20 μm and depth as long as 20 μm are prepared by bilayer metal assisted chemical etching (MaCE. A bilayer metal configuration (Metal 1 / Metal 2 was applied to assist etching of Si where metal 1 acts as direct catalyst and metal 2 provides mechanical support. Different metal types were investigated to figure out the influence of metal catalyst on morphology of etched silicon. We find that silicon microwires with vertical side wall are produced when we use Ag/Au bilayer, while cone–like and porous microwires formed when Pt/Au is applied. The different micro-/nano-structures in as-etched silicon are demonstrated to be due to the discrepancy of work function of metal catalyst relative to Si. Further, we constructed a silicon microwire arrays solar cells in a radial p–n junction configurations in a screen printed aluminum paste p–doping process.

  7. Novel microwave assisted chemical synthesis of Nd₂Fe₁₄B hard magnetic nanoparticles.

    Science.gov (United States)

    Swaminathan, Viswanathan; Deheri, Pratap Kumar; Bhame, Shekhar Dnyaneswar; Ramanujan, Raju Vijayaraghavan

    2013-04-07

    The high coercivity and excellent energy product of Nd2Fe14B hard magnets have led to a large number of high value added industrial applications. Chemical synthesis of Nd2Fe14B nanoparticles is challenging due to the large reduction potential of Nd(3+) and the high tendency for Nd2Fe14B oxidation. We report the novel synthesis of Nd2Fe14B nanoparticles by a microwave assisted combustion process. The process consisted of Nd-Fe-B mixed oxide preparation by microwave assisted combustion, followed by the reduction of the mixed oxide by CaH2. This combustion process is fast, energy efficient and offers facile elemental substitution. The coercivity of the resulting powders was ∼8.0 kOe and the saturation magnetization was ∼40 emu g(-1). After removal of CaO by washing, saturation magnetization increased and an energy product of 3.57 MGOe was obtained. A range of magnetic properties was obtained by varying the microwave power, reduction temperature and Nd to Fe ratio. A transition from soft to exchange coupled to hard magnetic properties was obtained by varying the composition of NdxFe1-xB8 (x varies from 7% to 40%). This synthesis procedure offers an inexpensive and facile platform to produce exchange coupled hard magnets.

  8. Aerosol assisted synthesis of hierarchical tin–carbon composites and their application as lithium battery anode materials

    KAUST Repository

    Guo, Juchen

    2013-01-01

    We report a method for synthesizing hierarchically structured tin-carbon (Sn-C) composites via aerosol spray pyrolysis. In this method, an aqueous precursor solution containing tin(ii) chloride and sucrose is atomized, and the resultant aerosol droplets carried by an inert gas are pyrolyzed in a high-temperature tubular furnace. Owing to the unique combination of high reaction temperature and short reaction time, this method is able to achieve a hetero-structure in which small Sn particles (15 nm) are uniformly embedded in a secondary carbon particle. This procedure allows the size and size distribution of the primary Sn particles to be tuned, as well as control over the size of the secondary carbon particles by addition of polymeric surfactant in the precursor solution. When evaluated as anode materials for lithium-ion batteries, the resultant Sn-C composites demonstrate attractive electrochemical performance in terms of overall capacity, electrochemical stability, and coulombic efficiency. © 2013 The Royal Society of Chemistry.

  9. Aerosols Science and Technology

    CERN Document Server

    Agranovski, Igor

    2011-01-01

    This self-contained handbook and ready reference examines aerosol science and technology in depth, providing a detailed insight into this progressive field. As such, it covers fundamental concepts, experimental methods, and a wide variety of applications, ranging from aerosol filtration to biological aerosols, and from the synthesis of carbon nanotubes to aerosol reactors.Written by a host of internationally renowned experts in the field, this is an essential resource for chemists and engineers in the chemical and materials disciplines across multiple industries, as well as ideal supplementary

  10. Metabolic Profiling as Well as Stable Isotope Assisted Metabolic and Proteomic Analysis of RAW 264.7 Macrophages Exposed to Ship Engine Aerosol Emissions: Different Effects of Heavy Fuel Oil and Refined Diesel Fuel.

    Directory of Open Access Journals (Sweden)

    Sean C Sapcariu

    Full Text Available Exposure to air pollution resulting from fossil fuel combustion has been linked to multiple short-term and long term health effects. In a previous study, exposure of lung epithelial cells to engine exhaust from heavy fuel oil (HFO and diesel fuel (DF, two of the main fuels used in marine engines, led to an increased regulation of several pathways associated with adverse cellular effects, including pro-inflammatory pathways. In addition, DF exhaust exposure was shown to have a wider response on multiple cellular regulatory levels compared to HFO emissions, suggesting a potentially higher toxicity of DF emissions over HFO. In order to further understand these effects, as well as to validate these findings in another cell line, we investigated macrophages under the same conditions as a more inflammation-relevant model. An air-liquid interface aerosol exposure system was used to provide a more biologically relevant exposure system compared to submerged experiments, with cells exposed to either the complete aerosol (particle and gas phase, or the gas phase only (with particles filtered out. Data from cytotoxicity assays were integrated with metabolomics and proteomics analyses, including stable isotope-assisted metabolomics, in order to uncover pathways affected by combustion aerosol exposure in macrophages. Through this approach, we determined differing phenotypic effects associated with the different components of aerosol. The particle phase of diluted combustion aerosols was found to induce increased cell death in macrophages, while the gas phase was found more to affect the metabolic profile. In particular, a higher cytotoxicity of DF aerosol emission was observed in relation to the HFO aerosol. Furthermore, macrophage exposure to the gas phase of HFO leads to an induction of a pro-inflammatory metabolic and proteomic phenotype. These results validate the effects found in lung epithelial cells, confirming the role of inflammation and cellular

  11. Metabolic Profiling as Well as Stable Isotope Assisted Metabolic and Proteomic Analysis of RAW 264.7 Macrophages Exposed to Ship Engine Aerosol Emissions: Different Effects of Heavy Fuel Oil and Refined Diesel Fuel.

    Science.gov (United States)

    Sapcariu, Sean C; Kanashova, Tamara; Dilger, Marco; Diabaté, Silvia; Oeder, Sebastian; Passig, Johannes; Radischat, Christian; Buters, Jeroen; Sippula, Olli; Streibel, Thorsten; Paur, Hanns-Rudolf; Schlager, Christoph; Mülhopt, Sonja; Stengel, Benjamin; Rabe, Rom; Harndorf, Horst; Krebs, Tobias; Karg, Erwin; Gröger, Thomas; Weiss, Carsten; Dittmar, Gunnar; Hiller, Karsten; Zimmermann, Ralf

    2016-01-01

    Exposure to air pollution resulting from fossil fuel combustion has been linked to multiple short-term and long term health effects. In a previous study, exposure of lung epithelial cells to engine exhaust from heavy fuel oil (HFO) and diesel fuel (DF), two of the main fuels used in marine engines, led to an increased regulation of several pathways associated with adverse cellular effects, including pro-inflammatory pathways. In addition, DF exhaust exposure was shown to have a wider response on multiple cellular regulatory levels compared to HFO emissions, suggesting a potentially higher toxicity of DF emissions over HFO. In order to further understand these effects, as well as to validate these findings in another cell line, we investigated macrophages under the same conditions as a more inflammation-relevant model. An air-liquid interface aerosol exposure system was used to provide a more biologically relevant exposure system compared to submerged experiments, with cells exposed to either the complete aerosol (particle and gas phase), or the gas phase only (with particles filtered out). Data from cytotoxicity assays were integrated with metabolomics and proteomics analyses, including stable isotope-assisted metabolomics, in order to uncover pathways affected by combustion aerosol exposure in macrophages. Through this approach, we determined differing phenotypic effects associated with the different components of aerosol. The particle phase of diluted combustion aerosols was found to induce increased cell death in macrophages, while the gas phase was found more to affect the metabolic profile. In particular, a higher cytotoxicity of DF aerosol emission was observed in relation to the HFO aerosol. Furthermore, macrophage exposure to the gas phase of HFO leads to an induction of a pro-inflammatory metabolic and proteomic phenotype. These results validate the effects found in lung epithelial cells, confirming the role of inflammation and cellular stress in the

  12. Metabolic Profiling as Well as Stable Isotope Assisted Metabolic and Proteomic Analysis of RAW 264.7 Macrophages Exposed to Ship Engine Aerosol Emissions: Different Effects of Heavy Fuel Oil and Refined Diesel Fuel

    Science.gov (United States)

    Sapcariu, Sean C.; Kanashova, Tamara; Dilger, Marco; Diabaté, Silvia; Oeder, Sebastian; Passig, Johannes; Radischat, Christian; Buters, Jeroen; Sippula, Olli; Streibel, Thorsten; Paur, Hanns-Rudolf; Schlager, Christoph; Mülhopt, Sonja; Stengel, Benjamin; Rabe, Rom; Harndorf, Horst; Krebs, Tobias; Karg, Erwin; Gröger, Thomas; Weiss, Carsten; Dittmar, Gunnar; Hiller, Karsten; Zimmermann, Ralf

    2016-01-01

    Exposure to air pollution resulting from fossil fuel combustion has been linked to multiple short-term and long term health effects. In a previous study, exposure of lung epithelial cells to engine exhaust from heavy fuel oil (HFO) and diesel fuel (DF), two of the main fuels used in marine engines, led to an increased regulation of several pathways associated with adverse cellular effects, including pro-inflammatory pathways. In addition, DF exhaust exposure was shown to have a wider response on multiple cellular regulatory levels compared to HFO emissions, suggesting a potentially higher toxicity of DF emissions over HFO. In order to further understand these effects, as well as to validate these findings in another cell line, we investigated macrophages under the same conditions as a more inflammation-relevant model. An air-liquid interface aerosol exposure system was used to provide a more biologically relevant exposure system compared to submerged experiments, with cells exposed to either the complete aerosol (particle and gas phase), or the gas phase only (with particles filtered out). Data from cytotoxicity assays were integrated with metabolomics and proteomics analyses, including stable isotope-assisted metabolomics, in order to uncover pathways affected by combustion aerosol exposure in macrophages. Through this approach, we determined differing phenotypic effects associated with the different components of aerosol. The particle phase of diluted combustion aerosols was found to induce increased cell death in macrophages, while the gas phase was found more to affect the metabolic profile. In particular, a higher cytotoxicity of DF aerosol emission was observed in relation to the HFO aerosol. Furthermore, macrophage exposure to the gas phase of HFO leads to an induction of a pro-inflammatory metabolic and proteomic phenotype. These results validate the effects found in lung epithelial cells, confirming the role of inflammation and cellular stress in the

  13. Chemical characterisation of atmospheric aerosols during a 2007 summer field campaign at Brasschaat, Belgium: sources and source processes of biogenic secondary organic aerosol

    Directory of Open Access Journals (Sweden)

    Y. Gómez-González

    2012-01-01

    Full Text Available Measurements of organic marker compounds and inorganic species were performed on PM2.5 aerosols from a Belgian forest site that is severely impacted by urban pollution ("De Inslag", Brasschaat, Belgium during a 2007 summer period within the framework of the "Formation mechanisms, marker compounds, and source apportionment for biogenic atmospheric aerosols (BIOSOL" project. The measured organic species included (i low-molecular weight (MW dicarboxylic acids (LMW DCAs, (ii methanesulfonate (MSA, (iii terpenoic acids originating from the oxidation of α-pinene, β-pinene, d-limonene and Δ3-carene, and (iv organosulfates related to secondary organic aerosol from the oxidation of isoprene and α-pinene. The organic tracers explained, on average, 5.3 % of the organic carbon (OC, of which 0.7 % was due to MSA, 3.4 % to LMW DCAs, 0.6 % to organosulfates, and 0.6 % to terpenoic acids. The highest atmospheric concentrations of most species were observed during the first five days of the campaign, which were characterised by maximum day-time temperatures >22 °C. Most of the terpenoic acids and the organosulfates peaked during day-time, consistent with their local photochemical origin. High concentrations of 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA and low concentrations of cis-pinonic acid were noted during the first five days of the campaign, indicative of an aged biogenic aerosol. Several correlations between organic species were very high (r>0.85, high (0.7<r<0.85, or substantial (0.5<r<0.7, suggesting that they are generated through similar formation pathways. Substantial correlations with temperature were found for OC, water-soluble OC, MBTCA, and several other organic species. MBTCA and terebic acid were highly correlated with the temperature (r>0.7 and showed an Arrhenius-type relationship, consistent with their formation through OH radical chemistry.

  14. Evaluating Sources of Chemical Pathways of Aerosol Production on the Southern Ute Indian Reservation and Navajo Nation using Isotopic and Geochemical Analysis

    Science.gov (United States)

    King, M. Z.; Michalski, G. M.

    2012-12-01

    Increase emissions of nitrogen oxides (NOx) as a result of the development of oil, gas and coal resources in the Four Corners region of the United States have caused concern for area American Indian tribes that levels of ozone, acid rain, and aerosols or particulate matter (PM) may increase on reservation lands. NOx in the atmosphere plays an important role in the formation of these pollutants and high levels are indicators of poor air quality and exposure to them has been linked to a host of human health effects and environmental problems facing today's society. Nitrogen oxides are eventually oxidized in the atmosphere to form nitric acid and particulate nitrate which falls to earth's surface by way of dry or wet deposition. In the end, it is the removal of NOx from the atmosphere by chemical conversion to nitrate that halts this production of oxidants, acid, and aerosols. Despite the importance of understanding atmospheric nitrate production there remains major deficiencies in estimating the significant key reactions that transform atmospheric NOx. This project will examine the chemical composition (Cl-, NO3-, SO42-) and stable isotope composition (N15, O17, O18, Δ17O) of aerosols (PM2.5-PM10) collected on the Southern Ute Indian Reservation and Navajo Nation to provide insight into the sources of NOx and the oxidation pathways that convert NOx into nitrate on these reservation lands.

  15. Using a moving measurement platform for determining the chemical composition of atmospheric aerosols between Moscow and Vladivostok

    Directory of Open Access Journals (Sweden)

    S. Kuokka

    2007-09-01

    Full Text Available The TROICA-9 expedition (Trans-Siberian Observations Into the Chemistry of the Atmosphere was carried out at the Trans-Siberian railway between Moscow and Vladivostok in October 2005. Measurements of aerosol physical and chemical properties were made from an observatory carriage connected to a passenger train. Black carbon (BC concentrations in fine particles (PM2.5, aerodynamic diameter <2.5 μm were measured with an aethalometer using a five-minute time resolution. Concentrations of inorganic ions and some organic compounds (Cl, NO3, SO42−, Na+, NH4+, K+, Ca2+, Mg2+, oxalate and methane sulphonate were measured continuously by using an on-line system with a 15-min time resolution. In addition, particle volume size distributions were determined for particles in the diameter range 3–850 nm using a 10-min time resolution. The continuous measurements were completed with 24-h PM2.5 filter samples stored in a refrigerator and analyzed later in a chemical laboratory. The analyses included the mass concentrations of PM2.5, ions, monosaccharide anhydrides (levoglucosan, galactosan and mannosan and trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, V and Zn. The mass concentrations of PM2.5 varied in the range of 4.3–34.8 μg m−3 with an average of 21.6 μg m−3. Fine particle mass consisted mainly of BC (average 27.6%, SO42− (13.0%, NH4+ (4.1% and NO3 (1.4%. One of the major constituents was obviously organic carbon which was not determined. The contribution of BC was high compared with other studies made in Europe and Asia. High concentrations of ions, BC and particle volume were observed between Moscow and roughly 4000 km east of it, as well as close to Vladivostok

  16. Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis

    Directory of Open Access Journals (Sweden)

    B. A. Flowers

    2010-11-01

    Full Text Available Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer (PASS-3, chemical filter analysis, and size distributions. The PASS-3 directly measures the effects of morphology (e.g. coatings on light absorption that traditional filter-based instruments are unable to address. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 74% of the deployment days, showing large variations in their measured chemical and optical properties. Analysis of eight distinct episodes, spanning wide ranges of chemical composition, optical properties, and source regions, reveals that episodes with higher organic carbon (OC/sulfate (SO42− and nitrate (NO3/SO42− composition ratios exhibit lower single scatter albedo at shorter wavelengths (ω405. We infer complex refractive indices (n–ik as a function of wavelength for the high, intermediate, and low OC/SO42− pollution episodes by using the observed particle size distributions and the measured optical properties. The smallest mean particle diameter corresponds to the high OC/SO42− aerosol episode. The imaginary part of the refractive index (k is greater for the high OC/SO42− episode at all wavelengths. A distinct, sharp increase in k at short wavelength implies enhanced light absorption by OC, which accounts for 50% of the light absorption at 405 nm, in the high OC/SO42− episode. Idealized analysis indicates increased absorption at 781 nm by factors greater than 3 relative to denuded black carbon in the laboratory. We hypothesize

  17. Analysis of long-range transport of aerosols for Portugal using 3D Chemical Transport Model and satellite measurements

    OpenAIRE

    Tchepel, Oxana; Ferreira, Joaquim; Fernandes, A.P.; Basart Alpuente, Sara; Baldasano Recio, José María; Borrego, Carlos

    2013-01-01

    The objective of this work is to assess the contribution of long-range transport of mineral dust from North Africa to the air pollution levels in Portugal based on a combination of a modelling approach and satellite observations. The Comprehensive Air Quality Model (CAMx) was applied together with the updated Dust REgional Atmospheric Model (BSC-DREAM8b) to characterise anthropogenic and natural sources of primary aerosols as well as secondary aerosols formation. The modelling results, ...

  18. Wintertime aerosol chemical composition and source apportionment of the organic fraction in the metropolitan area of Paris

    OpenAIRE

    M. Crippa; P. F. DeCarlo; Slowik, J. G.; Mohr, C; M. F. Heringa; R. Chirico; POULAIN L.; F. Freutel; Sciare, J.; Cozic, J.; Marco, C. F.; M. Elsasser; Nicolas, J.B.; N. Marchand; Abidi, E.

    2013-01-01

    The effect of a post-industrial megacity on local and regional air quality was assessed via a month-long field measurement campaign in the Paris metropolitan area during winter 2010. Here we present source apportionment results from three aerosol mass spectrometers and two aethalometers deployed at three measurement stations within the Paris region. Submicron aerosol composition is dominated by the organic fraction (30–36%) and nitrate (28–29%), with lower contributions from sulfate (14–16%),...

  19. Wintertime aerosol chemical composition and source apportionment of the organic fraction in the metropolitan area of Paris

    OpenAIRE

    M. Crippa; P. F. DeCarlo; Slowik, J. G.; Mohr, C; M. F. Heringa; R. Chirico; POULAIN L.; F. Freutel; Sciare, J.; Cozic, J.; C. F. Di Marco; M. Elsasser; N. José; N. Marchand; Abidi, E.

    2012-01-01

    The effect of a post-industrial megacity on local and regional air quality was assessed via a month-long field measurement campaign in the Paris metropolitan area during winter 2010. Here we present source apportionment results from three aerosol mass spectrometers and two aethalometers deployed at three measurement stations within the Paris region. Submicron aerosol composition is dominated by the organic fraction (30–36%) and nitrate (28–29%), with lower contributions from sulfate (14–16%),...

  20. Lanthanides determination in red wine using ultrasound assisted extraction, flow injection, aerosol desolvation and ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Bentlin, Fabrina R.S. [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501.970 Porto Alegre, RS (Brazil); Santos, Clarissa M.M. dos; Flores, Erico M.M. [Departamento de Quimica Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Pozebon, Dirce, E-mail: dircepoz@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, 91501.970 Porto Alegre, RS (Brazil)

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer Ultrasound was investigated and applied for red wine samples preparation. Black-Right-Pointing-Pointer Aliquots of 50 {mu}L of sample were nebulized and transported to plasma. Black-Right-Pointing-Pointer FI and pneumatic nebulization/aerosol desolvation were used. Black-Right-Pointing-Pointer LODs of the ICP-MS method for lanthanides determination were at ng L{sup -1} level. Black-Right-Pointing-Pointer Lanthanides concentration allowed red wines classification. - Abstract: This paper deals with the determination of the fourteen naturally occurring elements of the lanthanide series in red wine. Ultrasound (US) was used for sample preparation prior lanthanides determination using ICP-MS. Flow injection (FI) and pneumatic nebulization/aerosol desolvation were used for nebulization of aliquots of 50 {mu}L of sample and its subsequent transportation to plasma. Sample preparation procedures, matrix interference and time of sonication were evaluated. Better results for lanthanides in red wine were obtained by sonication with US probe for 90 s and sample 10-fold diluted. The limits of detection of La, Ce, Nd, Sm, Gd, Pr, Eu, Tb, Dy, Ho, Er, Tm, Lu and Yb were 6.57, 10.8, 9.97, 9.38, 2.71, 1.29, 1.22, 0.52, 2.35, 0.96, 2.30, 0.45, 0.24 and 1.35 ng L{sup -1}, respectively. Red wines of different varieties from three countries of South America were discriminated according to the country of origin by means of multivariate analysis of lanthanides concentration.

  1. Mixing of mineral dust with urban pollution aerosol over Dakar (Senegal): impact on dust physico-chemical and radiative properties

    Energy Technology Data Exchange (ETDEWEB)

    Petzold, A.; Veira, A.; Mund, S.; Esselborn, M.; Kiemle, C.; Weinzierl, B.; Hamburger, T.; Ehret, G. (Institut fur Physik der Atmosphaere, Deutsches Zentrum fur Luft- und Raumfahrt Oberpfaffenhofen, Wessling (Germany)), e-mail: andreas.petzold@dlr.de; Lieke, K.; Kandler, K. (Institut fur Angewandte Geowissenschaften, Technische Universitaet Darmstadt, Darmstadt (Germany))

    2011-09-15

    In the framework of the Saharan Mineral Dust Experiment (SAMUM) in 2008, the mixing of the urban pollution plume of Dakar (Senegal) with mineral dust was studied in detail using the German research aircraft Falcon which was equipped with a nadir-looking high spectral resolution lidar (HSRL) and extensive aerosol in situ instrumentation. The mineral dust layer as well as the urban pollution plume were probed remotely by the HSRL and in situ. Back trajectory analyses were used to attribute aerosol samples to source regions.We found that the emission from the region of Dakar increased the aerosol optical depth (532 nm) from approximately 0.30 over sea and over land east of Dakar to 0.35 in the city outflow. In the urban area, local black carbon (BC) emissions, or soot respectively, contributed more than 75% to aerosol absorption at 530 nm. In the dust layer, the single-scattering albedo at 530 nm was 0.96 - 0.99, whereas we found a value of 0.908 +- 0.018 for the aerosol dominated by urban pollution. After 6 h of transport over the North Atlantic, the externally mixed mode of secondary aerosol particles had almost completely vanished, whereas the BC agglomerates (soot) were still externally mixed with mineral dust particles

  2. Size-resolved aerosol chemical analysis of extreme haze pollution events during early 2013 in urban Beijing, China

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Shili; Pan, Yuepeng, E-mail: panyuepeng@mail.iap.ac.cn; Liu, Zirui; Wen, Tianxue; Wang, Yuesi, E-mail: wys@mail.iap.ac.cn

    2014-08-30

    Highlights: • Anthropogenic species substantially accumulated in both fine and coarse particles. • Secondary organic carbon in PM{sub 1.1} decreased from clear to haze days. • The mass peak shifted to larger particles from clear to haze days. • The NO{sub 3}{sup −}/SO{sub 4}{sup 2−} ratio decreased with enhanced haze pollution. • Both mobile local and stationary regional sources were vital for haze formation. - Abstract: Using size-resolved filter sampling and chemical characterization, high concentrations of water-soluble ions, carbonaceous species and heavy metals were found in both fine (PM{sub 2.1}) and coarse (PM{sub 2.1–9}) particles in Beijing during haze events in early 2013. Even on clear days, average mass concentration of submicron particles (PM{sub 1.1}) was several times higher than that previously measured in most of abroad urban areas. A high concentration of particulate matter on haze days weakens the incident solar radiation, which reduces the generation rate of secondary organic carbon in PM{sub 1.1}. We show that the peak mass concentration of particles shifted from 0.43–0.65 μm on clear days to 0.65–1.1 μm on lightly polluted days and to 1.1–2.1 μm on heavily polluted days. The peak shifts were also found for the following species: organic carbon, elemental carbon, NH{sub 4}{sup +}, SO{sub 4}{sup 2−}, NO{sub 3}{sup −}, K, Cu, Zn, Cd and Pb. Our findings demonstrate that secondary inorganic aerosols (36%) and organic matter (26%) dominated the fine particle mass on heavily polluted days, while their contribution reduced to 29% and 18%, respectively, on clear days. Besides fine particles, anthropogenic chemical species also substantially accumulated in the coarse mode, which suggests that particles with aerodynamic diameter larger than 2.1 μm cannot be neglected during severe haze events.

  3. In-situ physical and chemical characterization of the Eyjafjallajökull aerosol plume in the free troposphere over Italy

    Science.gov (United States)

    Sandrini, S.; Giulianelli, L.; Decesari, S.; Facchini, M. C.; Fuzzi, S.; Cristofanelli, P.; Marinoni, A.; Bonasoni, P.; Chiari, M.; Calzolai, G.; Canepari, S.; Perrino, C.

    2013-08-01

    Continuous measurements of physical and chemical properties at the Mt. Cimone GAW-WMO Global Station (2165 m a.s.l.) allowed the detection of the volcanic aerosol plume resulting from the Eyjafjallajökull eruption of spring 2010. The event affected the site after a transport over a distance of more than 3000 km. Two main transport episodes were detected during the eruption period, showing a volcanic fingerprint discernible against the free tropospheric background conditions typical of the site, the first from 19 to 21 April and the second from 18 to 20 May 2010. The paper reports the modification of aerosol characteristics observed during the two episodes, both characterized by an abrupt increase in fine and, especially, coarse mode particle number. Analysis of major, minor and trace elements by different analytical techniques (Ionic Chromatography, PIXE-PIGE and ICP-MS) were performed on aerosols collected by ground level discrete sampling. The resulting database allows the characterization of aerosol chemical composition during the volcanic plume transport and in background conditions. During the passage of the volcanic plume, the fine fraction was dominated by sulphates, denoting the secondary origin of this mode, mainly resulting from in-plume oxidation of volcanic SO2. By contrast, the coarse fraction was characterized by increased concentration of numerous elements of crustal origin, such as Fe, Ti, Mn, Ca, Na, and Mg, which enter the composition of silicate minerals. Data analysis of selected elements (Ti, Al, Fe, Mn) allowed the estimation of the volcanic plume's contribution to total PM10, resulting in a local enhancement of up to 9.5 μg m-3, i.e. 40% of total PM10, on 18 May, which was the most intense of the two episodes. These results appear significant, especially in the light of the huge distance of Mt. Cimone from the source, confirming the widespread diffusion of the Eyjafjallajokull ashes over Europe.

  4. In-situ physical and chemical characterization of the Eyjafjallajökull aerosol plume in the free troposphere over Italy

    Directory of Open Access Journals (Sweden)

    S. Sandrini

    2013-08-01

    Full Text Available Continuous measurements of physical and chemical properties at the Mt. Cimone GAW-WMO Global Station (2165 m a.s.l. allowed the detection of the volcanic aerosol plume resulting from the Eyjafjallajökull eruption of spring 2010. The event affected the site after a transport over a distance of more than 3000 km. Two main transport episodes were detected during the eruption period, showing a volcanic fingerprint discernible against the free tropospheric background conditions typical of the site, the first from 19 to 21 April and the second from 18 to 20 May 2010. The paper reports the modification of aerosol characteristics observed during the two episodes, both characterized by an abrupt increase in fine and, especially, coarse mode particle number. Analysis of major, minor and trace elements by different analytical techniques (Ionic Chromatography, PIXE-PIGE and ICP-MS were performed on aerosols collected by ground level discrete sampling. The resulting database allows the characterization of aerosol chemical composition during the volcanic plume transport and in background conditions. During the passage of the volcanic plume, the fine fraction was dominated by sulphates, denoting the secondary origin of this mode, mainly resulting from in-plume oxidation of volcanic SO2. By contrast, the coarse fraction was characterized by increased concentration of numerous elements of crustal origin, such as Fe, Ti, Mn, Ca, Na, and Mg, which enter the composition of silicate minerals. Data analysis of selected elements (Ti, Al, Fe, Mn allowed the estimation of the volcanic plume's contribution to total PM10, resulting in a local enhancement of up to 9.5 μg m-3, i.e. 40% of total PM10, on 18 May, which was the most intense of the two episodes. These results appear significant, especially in the light of the huge distance of Mt. Cimone from the source, confirming the widespread diffusion of the Eyjafjallajokull ashes over Europe.

  5. Correlations in the chemical composition of rural background atmospheric aerosol in the UK determined in real time using time-of-flight mass spectrometry.

    Science.gov (United States)

    Beddows, David C S; Donovan, Robert J; Harrison, Roy M; Heal, Mathew R; Kinnersley, Robert P; King, Martin D; Nicholson, David H; Thompson, Katherine C

    2004-02-01

    An aerosol time-of-flight mass spectrometer (ATOFMS) was used to determine, in real time, the size and chemical composition of individual particles in the atmosphere at the remote inland site of Eskdalemuir, Scotland. A total of 51,980 particles, in the size range 0.3-7.4 microm, were detected between the 25th and 30th June 2001. Rapid changes in the number density, size and chemical composition of the atmospheric aerosol were observed. These changes are attributed to two distinct types of air mass; a polluted air mass that had passed over the British mainland before reaching Eskdalemuir, interposed between two cleaner air masses that had arrived directly from the sea. Such changes in the background aerosol could clearly be very important to studies of urban aerosols and attempts at source apportionment. The results of an objective method of data analysis are presented. Correlations were sought between the occurrence of: lithium, potassium, rubidium, caesium, beryllium, strontium, barium, ammonium, amines, nitrate, nitrite, boron, mercury, sulfate, phosphate, fluorine, chlorine, bromine, iodine and carbon (both elemental and organic hydrocarbon) in both fine (d 2.5 microm) particle fractions. Several previously unreported correlations were observed, for instance between the elements lithium, beryllium and boron. The results suggest that about 2 in 3 of all fine particles (by number rather than by mass), and 1 in 2 of all coarse particles containing carbon, consisted of elemental carbon rather than organic hydrocarbon (although a bias in the sensitivity of the ATOFMS could have affected these numbers). The ratio of the number of coarse particles containing nitrate anions to the number of particles containing chloride anions exceeded unity when the air mass had travelled over the British mainland. The analysis also illustrates that an air mass of marine origin that had travelled slowly over agricultural land can accumulate amines and ammonium.

  6. Changes in chemical components of aerosol particles in different haze regions in China from 2006 to 2013 and contribution of meteorological factors

    Science.gov (United States)

    Zhang, X. Y.; Wang, J. Z.; Wang, Y. Q.; Liu, H. L.; Sun, J. Y.; Zhang, Y. M.

    2015-11-01

    Since there have been individual reports of persistent haze-fog events in January 2013 in central-eastern China, questions on factors causing the drastic differences in changes in 2013 from changes in adjacent years have been raised. Changes in major chemical components of aerosol particles over the years also remain unclear. The extent of meteorological factors contributing to such changes is yet to be determined. The study intends to present the changes in daily based major water-soluble constituents, carbonaceous species, and mineral aerosol in PM10 at 13 stations within different haze regions in China from 2006 to 2013, which are associated with specific meteorological conditions that are highly related to aerosol pollution (parameterized as an index called Parameter Linking Aerosol Pollution and Meteorological Elements - PLAM). No obvious changes were found in annual mean concentrations of these various chemical components and PM10 in 2013, relative to 2012. By contrast, wintertime mass of these components was quite different. In Hua Bei Plain (HBP), sulfate, organic carbon (OC), nitrate, ammonium, element carbon (EC), and mineral dust concentrations in winter were approximately 43, 55, 28, 23, 21, and 130 μg m-3, respectively; these masses were approximately 2 to 4 times higher than those in background mass, which also exhibited a decline during 2006 to 2010 and then a rise till 2013. The mass of these concentrations and PM10, except minerals, respectively, increased by approximately 28 to 117 % and 25 % in January 2013 compared with that in January 2012. Thus, persistent haze-fog events occurred in January 2013, and approximately 60 % of this increase in component concentrations from 2012 to 2013 can be attributed to severe meteorological conditions in the winter of 2013. In the Yangtze River Delta (YRD) area, winter masses of these components, unlike HBP, have not significantly increase since 2010; PLAM were also maintained at a similar level without

  7. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2016-08-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

  8. Chemical mimicking of bio-assisted aluminium extraction by Aspergillus niger's exometabolites.

    Science.gov (United States)

    Boriová, Katarína; Urík, Martin; Bujdoš, Marek; Pifková, Ivana; Matúš, Peter

    2016-11-01

    Presence of microorganisms in soils strongly affects mobility of metals. This fact is often excluded when mobile metal fraction in soil is studied using extraction procedures. Thus, the first objective of this paper was to evaluate strain Aspergillus niger's exometabolites contribution on aluminium mobilization. Fungal exudates collected in various time intervals during cultivation were analyzed and used for two-step bio-assisted extraction of alumina and gibbsite. Oxalic, citric and gluconic acids were identified in collected culture media with concentrations up to 68.4, 2.0 and 16.5 mmol L(-1), respectively. These exometabolites proved to be the most efficient agents in mobile aluminium fraction extraction with aluminium extraction efficiency reaching almost 2.2%. However, fungal cultivation is time demanding process. Therefore, the second objective was to simplify acquisition of equally efficient extracting agent by chemically mimicking composition of main organic acid components of fungal exudates. This was successfully achieved with organic acids mixture prepared according to medium composition collected on the 12th day of Aspergillus niger cultivation. This mixture extracted similar amounts of aluminium from alumina compared to culture medium. The aluminium extraction efficiency from gibbsite by organic acids mixture was lesser than 0.09% which is most likely because of more rigid mineral structure of gibbsite compared to alumina. The prepared organic acid mixture was then successfully applied for aluminium extraction from soil samples and compared to standard single step extraction techniques. This showed there is at least 2.9 times higher content of mobile aluminium fraction in soils than it was previously considered, if contribution of microbial metabolites is considered in extraction procedures. Thus, our contribution highlights the significance of fungal metabolites in aluminium extraction from environmental samples, but it also simplifies the

  9. Observations about chemical composition of aerosols in the Brazilian Amazon region - Case study: Biomass burning in the subequatorial Amazon region

    Science.gov (United States)

    Gioda, A.; Monteiro, I. L.; Almeida, A. C.; Hacon, S. S.; Dallacort, R.; Ignotti, E.; Godoy, J. M.; Loureiro, A. L.; Morais, F.; Artaxo, P.

    2012-04-01

    The study was carried out in two cities in the Brazilian Amazon region, Tangará da Serra (14 ° 37'10 "S, 57 ° 29'09" W, 427 m asl), located in a transition area between the Amazon biome and the Cerrado and has the characteristics of urban area in Amazon region; and Alta Floresta (9 ° 52 '32 "S, 56 ° 5' 10" W, 283 m asl) situated in the extreme north of the state of Mato Grosso (MT), both in the subequatorial Amazon region. Tangara da Serra has the largest production of sugar cane in the subequatorial Amazon region. They are located 800 km from each other. These two regions are inserted in a region with typical cycles of drought and rain that alter air pollution levels, and lies in the dispersion path of the pollution plume resulting from burnings in the Brazilian Amazon and pollution emanating from neighboring countries. Both cities have wet tropical climate with two well defined seasons: rainy summer (November to May) and dry winter (June to October). During the dry winter, biomass burnings are frequent in these regions. In 2008, the Department of the Environment has banned fires in the period from July 15 to September 15 throughout the State. In this study chemical characterization was performed for approximately 100 aerosol samples collected in each site during 2008. Fine and coarse aerosol samples collected in SFUs were analyzed by ion chromatography for determination of cations (Na+, K+, NH3+, Ca2+ and Mg2+), anions (SO42-, Cl- and NO3-) and organic acids (acetate and formiate) and also measures of black carbon (BC) (Aethalometer). The results showed that for both sites the average concentrations were quite similar for PM2.5 (16 µg/m3), PM10 (11 and 13 µg/m3) and black carbon (1.4 µg/m3 for PM2.5 and 1.6 µg/m3 for PM10). Sulfate was the predominant species in fine (45%) and coarse (26%) particles in both sites. The sulfate concentrations ranged from 0.01-1.92 µg/m3 in PM2.5 and 0.01-1.66 µg/m3 in PM10 in Tangará da Serra and 0.01-2.93 µg/m3 in PM2

  10. Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP: linking condensation, evaporation and chemical reactions of organics, oxidants and water

    Directory of Open Access Journals (Sweden)

    M. Shiraiwa

    2012-03-01

    Full Text Available We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007, and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system and the computational constraints, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds.

    In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity (Winkler et al., 2006. Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative

  11. Aerosol-Assisted Fast Formulating Uniform Pharmaceutical Polymer Microparticles with Variable Properties toward pH-Sensitive Controlled Drug Release

    Directory of Open Access Journals (Sweden)

    Hong Lei

    2016-05-01

    Full Text Available Microencapsulation is highly attractive for oral drug delivery. Microparticles are a common form of drug carrier for this purpose. There is still a high demand on efficient methods to fabricate microparticles with uniform sizes and well-controlled particle properties. In this paper, uniform hydroxypropyl methylcellulose phthalate (HPMCP-based pharmaceutical microparticles loaded with either hydrophobic or hydrophilic model drugs have been directly formulated by using a unique aerosol technique, i.e., the microfluidic spray drying technology. A series of microparticles of controllable particle sizes, shapes, and structures are fabricated by tuning the solvent composition and drying temperature. It is found that a more volatile solvent and a higher drying temperature can result in fast evaporation rates to form microparticles of larger lateral size, more irregular shape, and denser matrix. The nature of the model drugs also plays an important role in determining particle properties. The drug release behaviors of the pharmaceutical microparticles are dependent on their structural properties and the nature of a specific drug, as well as sensitive to the pH value of the release medium. Most importantly, drugs in the microparticles obtained by using a more volatile solvent or a higher drying temperature can be well protected from degradation in harsh simulated gastric fluids due to the dense structures of the microparticles, while they can be fast-released in simulated intestinal fluids through particle dissolution. These pharmaceutical microparticles are potentially useful for site-specific (enteric delivery of orally-administered drugs.

  12. Smart Magnetically Responsive Hydrogel Nanoparticles Prepared by a Novel Aerosol-Assisted Method for Biomedical and Drug Delivery Applications

    Directory of Open Access Journals (Sweden)

    Ibrahim M. El-Sherbiny

    2011-01-01

    Full Text Available We have developed a novel spray gelation-based method to synthesize a new series of magnetically responsive hydrogel nanoparticles for biomedical and drug delivery applications. The method is based on the production of hydrogel nanoparticles from sprayed polymeric microdroplets obtained by an air-jet nebulization process that is immediately followed by gelation in a crosslinking fluid. Oligoguluronate (G-blocks was prepared through the partial acid hydrolysis of sodium alginate. PEG-grafted chitosan was also synthesized and characterized (FTIR, EA, and DSC. Then, magnetically responsive hydrogel nanoparticles based on alginate and alginate/G-blocks were synthesized via aerosolization followed by either ionotropic gelation or both ionotropic and polyelectrolyte complexation using CaCl2 or PEG-g-chitosan/CaCl2 as crosslinking agents, respectively. Particle size and dynamic swelling were determined using dynamic light scattering (DLS and microscopy. Surface morphology of the nanoparticles was examined using SEM. The distribution of magnetic cores within the hydrogels nanoparticles was also examined using TEM. In addition, the iron and calcium contents of the particles were estimated using EDS. Spherical magnetic hydrogel nanoparticles with average particle size of 811 ± 162 to 941 ± 2 nm were obtained. This study showed that the developed method is promising for the manufacture of hydrogel nanoparticles, and it represents a relatively simple and potential low-cost system.

  13. Variations in the chemical composition of the submicron aerosol and in the sources of the organic fraction at a regional background site of the Po Valley (Italy)

    Science.gov (United States)

    Bressi, Michael; Cavalli, Fabrizia; Belis, Claudio A.; Putaud, Jean-Philippe; Fröhlich, Roman; Martins dos Santos, Sebastiao; Petralia, Ettore; Prévôt, André S. H.; Berico, Massimo; Malaguti, Antonella; Canonaco, Francesco

    2016-10-01

    Fine particulate matter (PM) levels and resulting impacts on human health are in the Po Valley (Italy) among the highest in Europe. To build effective PM abatement strategies, it is necessary to characterize fine PM chemical composition, sources and atmospheric processes on long timescales (> months), with short time resolution (fossil fuel combustion (11 %). Significant contributions of aged secondary organic aerosol (OOA) are observed throughout the year. The unexpectedly high degree of oxygenation estimated during wintertime is probably due to the contribution of secondary BBOA and the enhancement of aqueous-phase production of OOA during cold months. BBOA and nitrate are the only components of which contributions increase with the NR-PM1 levels. Therefore, biomass burning and NOx emission reductions would be particularly efficient in limiting submicron aerosol pollution events. Abatement strategies conducted during cold seasons appear to be more efficient than annual-based policies. In a broader context, further studies using high-time-resolution analytical techniques on a long-term basis for the characterization of fine aerosol should help better shape our future air quality policies, which constantly need refinement.

  14. Long-term real-time chemical characterization of submicron aerosols at Montsec (Southern Pyrenees, 1570 m a.s.l.

    Directory of Open Access Journals (Sweden)

    A. Ripoll

    2014-11-01

    Full Text Available Real-time measurements of inorganic (sulfate, nitrate, ammonium, chloride and black carbon (BC and organic submicron aerosols from a continental background site (Montsec, MSC, 1570 m a.s.l. in the Western Mediterranean Basin (WMB were conducted for 10 months (July 2011–April 2012. An Aerosol Chemical Speciation Monitor (ACSM was co-located with other on-line and off-line PM1 measurements. Analyses of the hourly, diurnal, and seasonal variations are presented here, for the first time for this region. Seasonal trends in PM1 components are attributed to variations in: evolution of the planetary boundary layer (PBL height, air mass origin, and meteorological conditions. In summer, the higher temperature and solar radiation increases convection, enhancing the growth of the PBL and the transport of anthropogenic pollutants towards high altitude sites. Furthermore, the regional recirculation of air masses over the WMB creates a continuous increase in the background concentrations of PM1 components and causes the formation of reserve strata at relatively high altitudes. Sporadically, MSC is affected by air masses from North Africa. The combination of all these atmospheric processes at local, regional and continental scales results in a high variability of PM1 components, with poorly defined daily patterns, except for the organic aerosols (OA. OA was mostly oxygenated organic aerosol (OOA, with two different types: semi-volatile (SV-OOA and low-volatile (LV-OOA, and both showed marked diurnal cycles regardless of the air mass origin, especially SV-OOA. This different diurnal variation compared to inorganic aerosols suggested that OA components at MSC are not only associated with anthropogenic and long-range-transported secondary OA (SOA, but also with recently-produced biogenic SOA. Very different conditions drive the aerosol phenomenology in winter at MSC. The thermal inversions and the lower vertical development of the PBL leave MSC in the free

  15. Nighttime chemical evolution of aerosol and trace gases in a power plant plume: Implications for secondary organic nitrate and organosulfate aerosol formation, NO3 radical chemistry, and N2O5 heterogeneous hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Zaveri, R.A.; Kleinman, L.; Berkowitz, C. M.; Brechtel, F. J.; Gilles, M. K.; Hubbe, J. M.; Jayne, J. T.; Laskin, A.; Madronich, S.; Onasch, T. B.; Pekour, M. S.; Springston, S. R.; Thornton, J. A.; Tivanski, A. V.; Worsnop, D. R.

    2010-06-01

    Nighttime chemical evolution of aerosol and trace gases in a coal-fired power plant plume was monitored with the Department of Energy Grumman Gulfstream-1 aircraft during the 2002 New England Air Quality Study field campaign. Quasi-Lagrangian sampling in the plume at increasing downwind distances and processing times was guided by a constant-volume balloon that was released near the power plant at sunset. While no evidence of fly ash particles was found, concentrations of particulate organics, sulfate, and nitrate were higher in the plume than in the background air. The enhanced sulfate concentrations were attributed to direct emissions of gaseous H{sub 2}SO{sub 4}, some of which had formed new particles as evidenced by enhanced concentrations of nucleation-mode particles in the plume. The aerosol species were internally mixed and the particles were acidic, suggesting that particulate nitrate was in the form of organic nitrate. The enhanced particulate organic and nitrate masses in the plume were inferred as secondary organic aerosol, which was possibly formed from NO{sub 3} radical-initiated oxidation of isoprene and other trace organic gases in the presence of acidic sulfate particles. Microspectroscopic analysis of particle samples suggested that some sulfate was in the form of organosulfates. Microspectroscopy also revealed the presence of sp{sup 2} hybridized C = C bonds, which decreased with increasing processing time in the plume, possibly because of heterogeneous chemistry on particulate organics. Constrained plume modeling analysis of the aircraft and tetroon observations showed that heterogeneous hydrolysis of N{sub 2}O{sub 5} was negligibly slow. These results have significant implications for several issues related to the impacts of power plant emissions on air quality and climate.

  16. Surface passivation of silicon nanowires based metal nano-particle assisted chemical etching for photovoltaic applications

    Science.gov (United States)

    Ben Rabha, Mohamed; Khezami, Lotfi; Jemai, Abdelbasset Bessadok; Alhathlool, Raed; Ajbar, Abdelhamid

    2017-03-01

    Metal Nano-particle Assisted Chemical Etching (MNpACE) is an extraordinary developed wet etching method for producing uniform semiconductor nanostructure (silicon nanowires) from patterned metallic film on crystalline silicon surface. The metal films facilitate the etching in HF and H2O2 solution and produce silicon nanowires (SiNWs).The creation of different SiNWs morphologies by changing the etching time and its effects on optical and optoelectronic properties was investigated. The combination effect of formed SiNWs and stain etching treatment in acid (HF/HNO3/H2O) solution on the surface morphology of Si wafers as well as on the optical and optoelectronic properties especially a PL response at 640 nm are presented. As a results, the effective lifetime (τeff) and surface recombination velocity (Seff) evolution of SiNWs after stain etching treatment showed significant improvements and less than 1% reflectance was achieved over the wavelength range of 400-800 nm and more than 36% reduction was observed compared to untreated surface. It has, thus, been demonstrated that all these factors may lead to improved energy efficiency from 8% to nearly 14.2% for a cell with SiNWs treated in acid (HF/HNO3/H2O) solution.

  17. Chemical vapor deposition graphene transfer process to a polymeric substrate assisted by a spin coater

    Science.gov (United States)

    Kessler, Felipe; da Rocha, Caique O. C.; Medeiros, Gabriela S.; Fechine, Guilhermino J. M.

    2016-03-01

    A new method to transfer chemical vapor deposition graphene to polymeric substrates is demonstrated here, it is called direct dry transfer assisted by a spin coater (DDT-SC). Compared to the conventional method DDT, the improvement of the contact between graphene-polymer due to a very thin polymeric film deposited by spin coater before the transfer process prevented air bubbles and/or moisture and avoided molecular expansion on the graphene-polymer interface. An acrylonitrile-butadiene-styrene copolymer, a high impact polystyrene, polybutadiene adipate-co-terephthalate, polylactide acid, and a styrene-butadiene-styrene copolymer are the polymers used for the transfers since they did not work very well by using the DDT process. Raman spectroscopy and optical microscopy were used to identify, to quantify, and to qualify graphene transferred to the polymer substrates. The quantity of graphene transferred was substantially increased for all polymers by using the DDT-SC method when compared with the DDT standard method. After the transfer, the intensity of the D band remained low, indicating low defect density and good quality of the transfer. The DDT-SC transfer process expands the number of graphene applications since the polymer substrate candidates are increased.

  18. 3D spirals with controlled chirality fabricated using metal-assisted chemical etching of silicon.

    Science.gov (United States)

    Hildreth, Owen J; Fedorov, Andrei G; Wong, Ching Ping

    2012-11-27

    The ability to fabricate 3D spiraling structures using metal-assisted chemical etching (MaCE) is one of the unique advantages of MaCE over traditional etching methods. However, control over the chirality of the spiraling structures has not been established. In this work, a systematic parametric study was undertaken for MaCE of star-shaped catalysts, examining the influence of arm shape, arm length, number of arms, center core diameter, and catalyst thickness on the rotation direction. This data was used to identify a set of geometric parameters that reliably induce rotation in a predefined direction such that large arrays of 3D spiraling structures can be fabricated with the same chirality. Electroless deposition into the MaCE template was used to examine the full etch path of the catalyst and an experimental fit was established to control rotation angle by adjusting the catalyst's center core diameter. The ability to fabricate large arrays of 3D spiraling structures with predefined chirality could have important applications in photonics and optoelectronics.

  19. Surface optical phonons in GaAs nanowires grown by Ga-assisted chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    García Núñez, C., E-mail: carlos.garcia@uam.es; Braña, A. F.; Pau, J. L.; Ghita, D.; García, B. J. [Grupo de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Shen, G.; Wilbert, D. S.; Kim, S. M.; Kung, P. [Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487 (United States)

    2014-01-21

    Surface optical (SO) phonons were studied by Raman spectroscopy in GaAs nanowires (NWs) grown by Ga-assisted chemical beam epitaxy on oxidized Si(111) substrates. NW diameters and lengths ranging between 40 and 65 nm and between 0.3 and 1.3 μm, respectively, were observed under different growth conditions. The analysis of the Raman peak shape associated to either longitudinal or surface optical modes gave important information about the crystal quality of grown NWs. Phonon confinement model was used to calculate the density of defects as a function of the NW diameter resulting in values between 0.02 and 0.03 defects/nm, indicating the high uniformity obtained on NWs cross section size during growth. SO mode shows frequency downshifting as NW diameter decreases, this shift being sensitive to NW sidewall oxidation. The wavevector necessary to activate SO phonon was used to estimate the NW facet roughness responsible for SO shift.

  20. Glass Imprint Templates by Spark Assisted Chemical Engraving for Microfabrication by Hot Embossing

    Directory of Open Access Journals (Sweden)

    Lucas Abia Hof

    2017-01-01

    Full Text Available As the field of microelectromechanical systems (MEMS matures, new demands are being placed on the microfabrication of complex architectures in robust materials, such as hard plastics. Iterative design optimization in a timely manner—rapid prototyping—places challenges on template fabrication, for methods such as injection moulding and hot embossing. In this paper, we demonstrate the possibility of using spark assisted chemical engraving (SACE to produce micro patterned glass templates. The direct, write-based approach enabled the facile fabrication of smooth microfeatures with variations in all three-dimensions, which could be replicated by hot embossing different thermoplastics. As a proof of principle, we demonstrated the technique for a high glass transition temperature polycarbonate. Good fidelity over more than 10 cycles provides evidence that the approach is viable for rapid prototyping and has the potential to satisfy commercial-grade production at medium-level output volumes. Glass imprint templates showed no degradation after use, but care must be taken due to brittleness. The technique has the potential to advance microfabrication needs in academia and could be used by MEMS product developers.

  1. Kinetics of diamond-like film growth using filament-assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gorsuch, G.; Jin, Y.; Ingle, N.K.; Mountziaris, T.J.; Yu, W.Y.; Petrou, A. [State Univ. of New York, Buffalo, NY (United States)

    1995-08-01

    A detailed kinetic model of diamond-like film growth from methane diluted in hydrogen using low-pressure, filament-assisted chemical vapor deposition (FACVD) has been developed. The model includes both gas-phase and surface reactions. The surface kinetics include adsorption of CH{sub 3}{center_dot} and H{center_dot}, abstraction reactions by gas phase radicals, desorption, and two pathways for diamond (sp{sup 3}) and graphitic carbon (sp{sup 2}) growth. It is postulated that adsorbed CH{sub 2}{center_dot} species are the major film precursors. The proposed kinetic model was incorporated into a transport model describing flow, heat and mass transfer in stagnation flow FACVD reactors. Diamond-like films were deposited on preceded Si substrates in such a reactor as a pressure of 26 Torr, inlet gas composition ranging from 0.5% to 1.5% methane in hydrogen and substrate temperatures ranging from 600 to 950 C. The best films were obtained at low methane concentrations and substrate temperature of 700 C. The films were characterized using Scanning Electron Microscopy (SEM) and Raman spectroscopy. Observations from their experiments and growth rates, compositions and stable species distributions in the gas phase. It is the first complete model of FACVD that includes gas-phase and surface kinetics coupled with transport phenomena.

  2. Changes in chemical components of aerosol particles in different haze regions in China from 2006 to 2013 and contribution of meteorological factors

    Directory of Open Access Journals (Sweden)

    X. Y. Zhang

    2015-07-01

    Full Text Available Since individuals experienced persistent haze-fog events in January 2013 in central-eastern China, questions on factors causing differences in drastic changes in 2013 from those in adjacent years have been raised. Changes in major chemical components of aerosol particles over the years also remain unclear. The extent of meteorological factors contributed to such changes is yet to be determined. The study intends to present the changes in daily-based major water-soluble constituents, carbonaceous species and mineral aerosol in PM10 at 13 stations within different haze regions in China from 2006 to 2013, associated with specific meteorological conditions that are highly related with aerosol pollution (parameterized as an index called "PLAM". No obvious changes were found in annual mean concentrations of these various chemical components and PM10 in 2013, relative to 2012. By contrast, wintertime mass of these components were quite different, in Hua Bei Plain (HBP, sulfate, OC, nitrate, ammonium, EC, and mineral dust concentrations in winter were approximately 43, 55, 28, 23, 21 and 130 μg m−3, respectively; these masses were approximately two to four times higher than those in background mass, also exhibiting a decline during 2006 to 2010, and then a rise till 2013. The mass of these concentrations and PM10, except mineral, respectively increased by approximately 28 to 117 and 25 % in January 2013 compared with that in January 2012. Thus, persistent haze-fog events occurred in January 2013, and approximately 60 % of this increase in component concentrations from 2012 to 2013 can be attributed to severe meteorological conditions in the winter of 2013. In Yangtzi River Delta (YRD area, winter masses of these components, unlike HBP, did not significantly increase since 2010; PLAM was also maintained at a similar level without significant changes. In the Pearl River Delta (PRD area, the regional background concentrations of the major chemical

  3. Towards the regulation of aerosol emissions by their potential health impact: Assessing adverse effects of aerosols from wood combustion and ship diesel engine emissions by combining comprehensive data on the chemical composition and their toxicological effects on human lung cells

    Science.gov (United States)

    Zimmermann, R.; Streibel, T.; Dittmar, G.; Kanashova, T.; Buters, J.; Öder, S.; Paur, H. R.; Dilger, M.; Weiss, C.; Harndorf, H.; Stengel, B.; Hirvonen, M. R.; Jokiniemi, J.; Hiller, K.; Sapcariu, S.; Sippula, O.; Orasche, J.; Müller, L.; Rheda, A.; Passig, J.; Radischat, C.; Czech, H.; Tiita, P.; Jalava, P.; Kasurinen, S.; Schwemer, T.; Yli-Prilä, P.; Tissari, J.; Lamberg, H.; Schnelle-Kreis, J.

    2014-12-01

    Ship engine emissions are important regarding lung and cardiovascular diseases in coastal regions worldwide. Bio mass burning is made responsible for adverse health effects in many cities and rural regions. The Virtual Helmholtz Institute-HICE (www.hice-vi.eu) addresses chemical & physical properties and health effects of anthropogenic combustion emissions. Typical lung cell responses to combustion aerosols include inflammation and apoptosis, but a molecular link with the specific chemical composition in particular of ship emissions has not been established. Through an air-liquid interface exposure system (ALI), we exposed human lung cells at-site to exhaust fumes from a ship engine running on common heavy fuel oil (HFO) and cleaner-burning diesel fuel (DF) as well as to emissions of wood combustion compliances. A special field deployable ALI-exposition system and a mobile S2-biological laboratory were developed for this study. Human alveolar basal epithelial cells (A549 etc.) are ALI-exposed to fresh, diluted (1:40-1:100) combustion aerosols and subsequently were toxicologically and molecular-biologically characterized. Advanced chemical analyses of the exhaust aerosols were combined with transcriptional, proteomic and metabolomic profiling to characterise the cellular responses. The HFO ship emissions contained high concentrations of toxic compounds (transition metals, organic toxicants) and particle masses. The cellular responses included inflammation and oxidative stress. Surprisingly, the DF ship emissions, which predominantly contain rather "pure" carbonaceous soot and much less known toxicants, induced significantly broader biological effects, affecting essential cellular pathways (e.g., mitochondrial function and intracellular transport). Therefore the use of distillate fuels for shipping (this is the current emission reduction strategy of the IMO) appears insufficient for diminishing health effects. The study suggests rather reducing the particle emissions

  4. Multiphase chemical kinetics of OH radical uptake by molecular organic markers of biomass burning aerosols: humidity and temperature dependence, surface reaction, and bulk diffusion.

    Science.gov (United States)

    Arangio, Andrea M; Slade, Jonathan H; Berkemeier, Thomas; Pöschl, Ulrich; Knopf, Daniel A; Shiraiwa, Manabu

    2015-05-14

    Multiphase reactions of OH radicals are among the most important pathways of chemical aging of organic aerosols in the atmosphere. Reactive uptake of OH by organic compounds has been observed in a number of studies, but the kinetics of mass transport and chemical reaction are still not fully understood. Here we apply the kinetic multilayer model of gas-particle interactions (KM-GAP) to experimental data from OH exposure studies of levoglucosan and abietic acid, which serve as surrogates and molecular markers of biomass burning aerosol (BBA). The model accounts for gas-phase diffusion within a cylindrical coated-wall flow tube, reversible adsorption of OH, surface-bulk exchange, bulk diffusion, and chemical reactions at the surface and in the bulk of the condensed phase. The nonlinear dependence of OH uptake coefficients on reactant concentrations and time can be reproduced by KM-GAP. We find that the bulk diffusion coefficient of the organic molecules is approximately 10(-16) cm(2) s(-1), reflecting an amorphous semisolid state of the organic substrates. The OH uptake is governed by reaction at or near the surface and can be kinetically limited by surface-bulk exchange or bulk diffusion of the organic reactants. Estimates of the chemical half-life of levoglucosan in 200 nm particles in a biomass burning plume increase from 1 day at high relative humidity to 1 week under dry conditions. In BBA particles transported to the free troposphere, the chemical half-life of levoglucosan can exceed 1 month due to slow bulk diffusion in a glassy matrix at low temperature.

  5. Chemical insights, explicit chemistry, and yields of secondary organic aerosol from OH radical oxidation of methylglyoxal and glyoxal in the aqueous phase

    Directory of Open Access Journals (Sweden)

    Y. B. Lim

    2013-09-01

    Full Text Available Atmospherically abundant, volatile water-soluble organic compounds formed through gas-phase chemistry (e.g., glyoxal (C2, methylglyoxal (C3, and acetic acid have great potential to form secondary organic aerosol (SOA via aqueous chemistry in clouds, fogs, and wet aerosols. This paper (1 provides chemical insights into aqueous-phase OH-radical-initiated reactions leading to SOA formation from methylglyoxal and (2 uses this and a previously published glyoxal mechanism (Lim et al., 2010 to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012. This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010, and is used to simulate the profiles of products and to estimate SOA yields. At cloud-relevant concentrations (~ 10−6 − ~ 10−3 M; Munger et al., 1995 of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass are ~ 120% for glyoxal and ~ 80% for methylglyoxal. During droplet evaporation oligomerization of unreacted methylglyoxal/glyoxal that did not undergo aqueous photooxidation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (~ 10 M, the major oxidation products are oligomers formed via organic radical–radical reactions, and simulated SOA yields (by mass are ~ 90% for both glyoxal and methylglyoxal. Non-radical reactions (e.g., with ammonium could enhance yields.

  6. Chemical insights, explicit chemistry, and yields of secondary organic aerosol from OH radical oxidation of methylglyoxal and glyoxal in the aqueous phase

    Science.gov (United States)

    Lim, Y. B.; Tan, Y.; Turpin, B. J.

    2013-09-01

    Atmospherically abundant, volatile water-soluble organic compounds formed through gas-phase chemistry (e.g., glyoxal (C2), methylglyoxal (C3), and acetic acid) have great potential to form secondary organic aerosol (SOA) via aqueous chemistry in clouds, fogs, and wet aerosols. This paper (1) provides chemical insights into aqueous-phase OH-radical-initiated reactions leading to SOA formation from methylglyoxal and (2) uses this and a previously published glyoxal mechanism (Lim et al., 2010) to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012). This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010), and is used to simulate the profiles of products and to estimate SOA yields. At cloud-relevant concentrations (~ 10-6 - ~ 10-3 M; Munger et al., 1995) of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass) are ~ 120% for glyoxal and ~ 80% for methylglyoxal. During droplet evaporation oligomerization of unreacted methylglyoxal/glyoxal that did not undergo aqueous photooxidation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (~ 10 M), the major oxidation products are oligomers formed via organic radical-radical reactions, and simulated SOA yields (by mass) are ~ 90% for both glyoxal and methylglyoxal. Non-radical reactions (e.g., with ammonium) could enhance yields.

  7. Appearance of strong absorbers and fluorophores in limonene-O3 secondary organic aerosol due to NH4+-mediated chemical aging over long time scales

    Science.gov (United States)

    Bones, David L.; Henricksen, Dana K.; Mang, Stephen A.; Gonsior, Michael; Bateman, Adam P.; Nguyen, Tran B.; Cooper, William J.; Nizkorodov, Sergey A.

    2010-03-01

    This study investigated long-term chemical aging of model biogenic secondary organic aerosol (SOA) prepared from the ozonolysis of terpenes. Techniques including electrospray ionization mass spectrometry (ESI-MS), UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, NMR, and three-dimensional fluorescence were used to probe the changes in chemical composition of SOA collected by impaction on substrates and also of aqueous extracts of SOA. The addition of ammonium ions or amino acids to limonene SOA reproducibly produced orange-colored species that strongly absorbed visible radiation and fluoresced at UV and visible wavelengths. Simultaneous addition of H2SO4 to the SOA aqueous extracts inhibited this color transformation. These observations suggest the existence of aging processes leading to heavily conjugated molecules containing organic nitrogen. The presence of nitrogen in the chromophores was confirmed by the dependence of the absorption and fluorescence spectra on the amino acids added. In contrast to the strong change in the absorption and fluorescence spectra, there was no significant change in the ESI-MS, FTIR, and NMR spectra, suggesting that the chromophores were minor species in the aged SOA. Aqueous extracts of aged limonene + NH4+ SOA were characterized by an effective base-e absorption coefficient of ˜3 L g-1 cm-1 at 500 nm. Assuming particulate matter concentrations typical of polluted rural air gives an upper limit of 0.2 M m-1 for the aerosol absorption coefficient due to the aged limonene oxidation products. Biogenic SOA can therefore become weakly absorbing if they undergo aging in the presence of NH4+-containing aerosol.

  8. Microwave-assisted chemical insertion: a rapid technique for screening cathodes for Mg-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Kaveevivitchai, Watchareeya; Huq, Ashfia; Manthiram, Arumugam

    2016-12-19

    We report an ultrafast microwave-assisted solvothermal method for chemical insertion of Mg2+ ions into host materials using magnesium acetate [Mg(CH3COO)2] as a metal-ion source and diethylene glycol (DEG) as a reducing agent. For instance, up to 3 Mg ions per formula unit of a microporous host framework Mo2.5+yVO9+z could be inserted in as little as 30 min at 170–195 °C in air. This process is superior to the traditional method which involves the use of organometallic reagents, such as di-n-butylmagnesium [(C4H9)2Mg] and magnesium bis(2,6-di-tert-butylphenoxide) [Mg-(O-2,6-But2C6H3)2], and requires an inert atmosphere with extremely long reaction times. Considering the lack of robust electrolytes for Mg-ion batteries, this facile approach can be readily used as a rapid screening technique to identify potential Mg-ion electrode hosts without the necessity of fabricating electrodes and assembling electrochemical cells. Due to the mild reaction conditions, the overall structure and morphology of the Mg-ion inserted products are maintained and the compounds can be used successfully as a cathode in Mg-ion batteries. The combined synchrotron X-ray and neutron diffraction Rietveld analysis reveals the structure of the Mg-inserted compounds and gives an insight into the interactions between the Mg ions and the open-tunnel host framework.

  9. Light-emitting silicon nanowires obtained by metal-assisted chemical etching

    Science.gov (United States)

    Irrera, Alessia; Josè Lo Faro, Maria; D’Andrea, Cristiano; Alessio Leonardi, Antonio; Artoni, Pietro; Fazio, Barbara; Picca, Rosaria Anna; Cioffi, Nicola; Trusso, Sebastiano; Franzò, Giorgia; Musumeci, Paolo; Priolo, Francesco; Iacona, Fabio

    2017-04-01

    This review reports on a new process for the synthesis of Si nanowires (NWs), based on the wet etching of Si substrates assisted by a thin metal film. The approach exploits the thickness-dependent morphology of the metal layers to define uncovered nanometric Si regions, which behave as precursor sites for the formation of very dense (up to 1 × 1012 NW cm‑2) arrays of long (up to several μm) and ultrathin (diameter of 5–9 nm) NWs. Intense photoluminescence (PL) peaks, characterized by maxima in the 640–750 nm range and by an external quantum efficiency of 0.5%, are observed when the Si NWs are excited at room temperature. The spectra show a blueshift if the size of the NW is decreased, in agreement with the occurrence of quantum confinement effects. The same etching process can be used to obtain ultrathin Si/Ge NWs from a Si/Ge multi-quantum well. The Si/Ge NWs exhibit—in addition to the Si-related PL peak—a signal at about 1240 nm due to Ge nanostructures. The huge surface area of the Si NW arrays can be exploited for sensing and analytical applications. The dependence of the PL intensity on the chemical composition of the surface indeed suggests interesting perspectives for the detection of gaseous molecules. Moreover, Si NWs decorated with Ag nanoparticles can be effectively employed in the interference-free laser desorption-ionization mass spectrometry of low-molecular-weight analytes. A device based on conductive Si NWs, showing intense and stable electroluminescence at an excitation voltage as low as 2 V, is also presented. The unique features of the proposed synthesis (the process is cheap, fast, maskless and compatible with Si technology) and the unusual optical properties of the material open the route towards new and unexpected perspectives for semiconductor NWs in photonics.

  10. Intercomparison of modal and sectional aerosol microphysics representations within the same 3-D global chemical transport model

    Directory of Open Access Journals (Sweden)

    G. W. Mann

    2012-05-01

    Full Text Available In the most advanced aerosol-climate models it is common to represent the aerosol particle size distribution in terms of several log-normal modes. This approach, motivated by computational efficiency, makes assumptions about the shape of the particle distribution that may not always capture the properties of global aerosol. Here, a global modal aerosol microphysics module (GLOMAP-mode is evaluated and improved by comparing against a sectional version (GLOMAP-bin and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that the current values for two size distribution parameter settings in the modal scheme (mode widths and inter-modal separation sizes resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Annual mean surface-level mass of sulphate, sea-salt, black carbon (BC and organic carbon (OC are within 25% in the two schemes in nearly all regions. Surface level concentrations of condensation nuclei (CN, cloud condensation nuclei (CCN, surface area density and condensation sink also compare within 25% in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically 25–60% higher in the modal model, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2–4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin

  11. Remote Marine Aerosol: A Characterization of Physical, Chemical and Optical Properties and their Relation to Radiative Transfer in the Troposphere

    Science.gov (United States)

    Clarke, Antony D.; Porter, John N.

    1997-01-01

    Our research effort is focused on improving our understanding of aerosol properties needed for optical models for remote marine regions. This includes in-situ and vertical column optical closure and involves a redundancy of approaches to measure and model optical properties that must be self consistent. The model is based upon measured in-situ aerosol properties and will be tested and constrained by the vertically measured spectral differential optical depth of the marine boundary layer, MBL. Both measured and modeled column optical properties for the boundary layer, when added to the free-troposphere and stratospheric optical depth, will be used to establish spectral optical depth over the entire atmospheric column for comparison to and validation of satellite derived radiances (AVHRR).

  12. Chemical Composition of Aerosol Particles Emitted by a Passenger Car Engine Fueled by Ethanol/Gasoline Mixtures

    Science.gov (United States)

    Medrano, J. M.; Gross, D. S.; Dutcher, D. D.; Drayton, M.; Kittelson, D.; McMurry, P.

    2007-12-01

    With concerns of national security, climate change, and human health, many people have called for oil independence for the United States and for the creation of alternative fuels. Ethanol has been widely praised as a viable alternative to petroleum-based fuels, due to the fact that it can be produced locally. A great deal of work has been done to characterize the energy balance of ethanol production versus consumption, but there have been fewer studies of the environmental and health impacts of emissions from combustion of ethanol/gasoline mixtures such as those burned in the modern vehicle fleet. To study the particulate emissions from such fuels, different ethanol/gasoline fuel mixtures with 0, 20, 40, and 85% ethanol were burned in a dynamometer-mounted automobile engine. The engine exhaust was diluted and sampled with two aerosol Time-of-Flight Mass Spectrometers (TSI 3800 ATOFMS), sampling different particle size ranges (50-500 nm and 150-3000 nm, respectively), to measure size and composition of the emitted aerosol particles. A variety of other aerosol characterization techniques were also employed to determine the size distribution of the aerosol particles, the mass emission rate from the engine, and the concentration of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC) in the particle emissions. Here we will focus on results from the ATOFMS, which provides us with a particle size and mass spectra - for both negative and positive ions - for each particle that is sampled. Particles being emitted were found to contain primarily PAHs, elemental carbon (EC), nitrates, and sulfates. Particles were analyzed to investigate trends in particle composition as a function of fuel ethanol content, particle size, and for the types of particles emitted. A trend in particle type as a function of fuel ethanol content was evident in smaller particles, and trends in composition as a function of particle size were visible across the entire size range sampled.

  13. Mixing of mineral dust with urban pollution aerosol over Dakar (Senegal): impact on dust physico-chemical and radiative properties

    OpenAIRE

    Petzold, A.; A. Veira; Mund, S.; Esselborn, M.; Kiemle, C.; B. Weinzierl; T. Hamburger; Ehret, G.; Lieke, K.; Kandler, K

    2011-01-01

    In the framework of the Saharan Mineral Dust Experiment (SAMUM) in 2008, the mixing of the urban pollution plume of Dakar (Senegal) with mineral dust was studied in detail using the German research aircraft Falcon which was equipped with a nadir-looking high spectral resolution lidar (HSRL) and extensive aerosol in situ instrumentation. The mineral dust layer as well as the urban pollution plume were probed remotely by the HSRL and in situ. Back trajectory analyses were used to attribute aero...

  14. Mixing of mineral dust with urban pollution aerosol over Dakar (Senegal): Impact on dust physico-chemical and radiative properties.

    OpenAIRE

    Petzold, A.; A. Veira; Mund, S.; Esselborn, M.; Kiemle, C.; B. Weinzierl; T. Hamburger; Ehret, G.; Lieke, K.; Kandler, K

    2011-01-01

    In the framework of the Saharan Mineral Dust Experiment (SAMUM) in 2008, the mixing of the urban pollution plume of Dakar (Senegal) with mineral dust was studied in detail using the German research aircraft Falcon which was equipped with a nadir-looking high spectral resolution lidar (HSRL) and extensive aerosol in situ instrumentation. The mineral dust layer as well as the urban pollution plume were probed remotely by the HSRL and in situ. Back trajectory analyses were used to at...

  15. Insights into a dust event transported through Beijing in spring 2012: Morphology, chemical composition and impact on surface aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wei [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China); Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan); Niu, Hongya [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China); Key Laboratory of Resource Exploration Research of Hebei Province, Hebei University of Engineering, Handan, Hebei 056038 (China); Zhang, Daizhou [Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan); Wu, Zhijun [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China); Chen, Chen [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China); Beijing Municipal Environmental Monitoring Center, Beijing 100044 (China); Wu, Yusheng; Shang, Dongjie [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China); Hu, Min, E-mail: minhu@pku.edu.cn [State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871 (China)

    2016-09-15

    Multiple approaches were used to investigate the evolution of surface aerosols in Beijing during the passage of a dust event at high altitude, which was from the Gobi areas of southern Mongolia and covered a wide range of North China. Single particle analysis with electron microscope showed that the majority of coarse particles were mineral ones, and most of them were in the size range of 1–7 μm with a peak of number concentration at about 3.5 μm. Based on elemental composition and morphology, the mineral particles could be classified into several groups, including Si-rich (71%), Ca-rich (15%), Fe-rich (6%), and halite-rich (2%), etc., and they were the main contributors to the aerosol optical depth as the dust occurred. The size distributions of surface aerosols were significantly affected by the dust intrusion. The average number concentration of accumulation mode particles during the event was about 400 cm{sup −3}, which was much lower than that in heavily polluted days (6300 cm{sup −3}). At the stage of floating dust, the number concentration of accumulation mode particles decreased, and coarse particles contributed to total volume concentration of particulate matter as much as 90%. The accumulation mode particles collected in this stage were mostly in the size range of 0.2–0.5 μm, and were rectangular or spherical. They were considered to be particles consisting of ammonium sulfate. New particle formation (NPF) was observed around noon in the three days during the dust event, indicating that the passage of the dust was probably favorable for NPF. - Highlights: • A dust event transported at high altitude through Beijing was investigated. • The dust event caused high variation in surface aerosol number concentrations. • Fine particles in the floating dust period probably consisted of ammonium sulfate. • Passage of the dust induced a favorable condition for new particle formation.

  16. Influence of the voltage waveform during nanocomposite layer deposition by aerosol-assisted atmospheric pressure Townsend discharge

    Science.gov (United States)

    Profili, J.; Levasseur, O.; Naudé, N.; Chaneac, C.; Stafford, L.; Gherardi, N.

    2016-08-01

    This work examines the growth dynamics of TiO2-SiO2 nanocomposite coatings in plane-to-plane Dielectric Barrier Discharges (DBDs) at atmospheric pressure operated in a Townsend regime using nebulized TiO2 colloidal suspension in hexamethyldisiloxane as the growth precursors. For low-frequency (LF) sinusoidal voltages applied to the DBD cell, with voltage amplitudes lower than the one required for discharge breakdown, Scanning Electron Microscopy of silicon substrates placed on the bottom DBD electrode reveals significant deposition of TiO2 nanoparticles (NPs) close to the discharge entrance. On the other hand, at higher frequencies (HF), the number of TiO2 NPs deposited strongly decreases due to their "trapping" in the oscillating voltage and their transport along the gas flow lines. Based on these findings, a combined LF-HF voltage waveform is proposed and used to achieve significant and spatially uniform deposition of TiO2 NPs across the whole substrate surface. For higher voltage amplitudes, in the presence of hexamethyldisiloxane and nitrous oxide for plasma-enhanced chemical vapor deposition of inorganic layers, it is found that TiO2 NPs become fully embedded into a silica-like matrix. Similar Raman spectra are obtained for as-prepared TiO2 NPs and for nanocomposite TiO2-SiO2 coating, suggesting that plasma exposure does not significantly alter the crystalline structure of the TiO2 NPs injected into the discharge.

  17. Dependence of aerosol scattering coefficients on relative humidity observed at two coastal sites on the East China Sea: Comparison to remote observations and influence of chemical composition

    Science.gov (United States)

    Kanaya, Y.; Taketani, F.; Irie, H.; Komazaki, Y.; Takashima, H.; Xiaole, P.; Takami, A.; Wang, Z.

    2011-12-01

    We employed an integrating nephelometer equipped with a humidifier (where the relative humidity (RH) was scanned between 40 and 90%) to measure the aerosol scattering coefficients and their dependence on RH at Fukue Island (32.75N, 128.68E), west of Japan, in May 2009 and at Rudong, Jiangsu, China (32.26N, 121.37E) in May/June 2010, aiming at better characterization of optical properties of the regional-scale aerosol pollution over East Asia. The two coastal sites are located east and west of the East China Sea and are separated by about 700 km. The observed scattering coefficients are normalized by the concurrently measured PM2.5 mass concentrations and thereby behaviors of the mass scattering coefficients are discussed. At Fukue, the mass scattering coefficients under the ambient RH conditions were >1.5 times higher than those observed under the dry condition (RH = 40%), suggesting that the RH effect was crucial in determining optical properties under ambient conditions. The coefficients under the ambient RH conditions, rather than the dry values, agreed better with the extinction coefficients determined by MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) technique based on remote measurements of O4 optical depths. The single-scattering albedo (SSA), estimated in combination to the absorption coefficients determined by a MAAP (Multi-Angle Absorption Photometer) instrument, had similar average values (~0.95) at the two sites. The SSA values at the two sites were commonly lowered (to below 0.90) when the air traveled from the North China Plain region. At Fukue, the RH dependence was found to be weakened when the organics/sulfate ratio increased (as observed by an Aerodyne Aerosol Mass Spectrometer), while such influence of chemical composition was less clear at Rudong, possibly masked by large temporal variations in the particle size distributions.

  18. Nighttime chemical evolution of aerosol and trace gases in a power plant plume: Implications for secondary organic nitrate and organosulfate aerosol formation, NO₃ radical chemistry, and N₂O₅ heterogeneous hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Zaveri, Rahul A.; Berkowitz, Carl M.; Brechtel, Fred J.; Gilles, Marry K.; Hubbe, John M.; Jayne, J. T.; Kleinman, Lawrence I.; Laskin, Alexander; Madronich, Sasha; Onasch, Timothy B.; Pekour, Mikhail S.; Springston, Stephen R.; Thornton, Joel A.; Tivanski, Alexei V.; Worsnop, Douglas R.

    2010-06-22

    Chemical evolution of aerosols and trace gases in the Salem Harbor power plant plume was monitored with the DOE G-1 aircraft on the night of July 30-31, 2002. Quasi-Lagrangian sampling in the plume at increasing downwind distances/processing times was guided by a constant-volume tetroon that was released near the power plant at sunset. While no evidence of fly ash particles was found, concentrations of particulate organics, sulfate, and nitrate were higher in the plume than in the nearby background air. These species were internally mixed and the particles were acidic, suggesting that particulate nitrate was in the form of organic nitrate. The enhanced particulate organic and nitrate masses in the plume were inferred to be as secondary organic aerosol, possibly formed from the NO3 radical-initiated oxidation of isoprene and other trace organic gases in the presence of acidic sulfate particles. The enhanced particulate sulfate concentrations observed in the plume were attributed to direct emissions of gaseous SO3/H2SO4 from the power plant. Furthermore, concentration of nucleation mode particles was significantly higher in the plume than in background air, suggesting that some of the emitted H2SO4 had nucleated to form new particles. Spectromicroscopic analyses of particle samples suggested that some sulfate was likely in the form of organosulfates. Constrained Lagrangian model analysis of the aircraft and tetroon observations showed that heterogeneous hydrolysis of N2O5 was negligibly slow. These results have significant implications for several scientific and regulatory issues related to the impacts of power plant emissions on atmospheric chemistry, air quality, visibility, and climate.

  19. Chemical composition, microstructure, and hygroscopic properties of aerosol particles at the Zotino Tall Tower Observatory (ZOTTO), Siberia, during a summer campaign

    Science.gov (United States)

    Mikhailov, E. F.; Mironov, G. N.; Pöhlker, C.; Chi, X.; Krüger, M. L.; Shiraiwa, M.; Förster, J.-D.; Pöschl, U.; Vlasenko, S. S.; Ryshkevich, T. I.; Weigand, M.; Kilcoyne, A. L. D.; Andreae, M. O.

    2015-08-01

    In this study we describe the hygroscopic properties of accumulation- and coarse-mode aerosol particles sampled at the Zotino Tall Tower Observatory (ZOTTO) in central Siberia (61° N, 89° E) from 16 to 21 June 2013. The hygroscopic growth measurements were supplemented with chemical analyses of the samples, including inorganic ions and organic/elemental carbon. In addition, the microstructure and chemical compositions of aerosol particles were analyzed by x-ray micro-spectroscopy (STXM-NEXAFS) and transmission electron microscopy (TEM). A mass closure analysis indicates that organic carbon accounted for 61 and 38 % of particulate matter (PM) in the accumulation mode and coarse mode, respectively. The water-soluble fraction of organic matter was estimated to be 52 and 8 % of PM in these modes. Sulfate, predominantly in the form of ammoniated sulfate, was the dominant inorganic component in both size modes: ~ 34 % in the accumulation mode vs. ~ 47 % in the coarse mode. The hygroscopic growth measurements were conducted with a filter-based differential hygroscopicity analyzer (FDHA) over the range of 5-99.4 % RH in the hydration and dehydration operation modes. The FDHA study indicates that both accumulation and coarse modes exhibit pronounced water uptake approximately at the same relative humidity (RH), starting at ~ 70 %, while efflorescence occurred at different humidities, i.e., at ~ 35 % RH for submicron particles vs. ~ 50 % RH for supermicron particles. This ~ 15 % RH difference was attributed to higher content of organic material in the submicron particles, which suppresses water release in the dehydration experiments. The kappa mass interaction model (KIM) was applied to characterize and parameterize non-ideal solution behavior and concentration-dependent water uptake by atmospheric aerosol samples in the 5-99.4 % RH range. Based on KIM, the volume-based hygroscopicity parameter, κv, was calculated. The κv,ws value related to the water-soluble (ws

  20. Chemical composition, microstructure, and hygroscopic properties of aerosol particles at the Zotino Tall Tower Observatory (ZOTTO, Siberia, during a summer campaign

    Directory of Open Access Journals (Sweden)

    E. F. Mikhailov

    2015-03-01

    Full Text Available In this study we describe the hygroscopic properties of accumulation- and coarse-mode aerosol particles sampled at the Zotino Tall Tower Observatory (ZOTTO in Central Siberia (61° N; 89° E from 16 to 21 June 2013. The hygroscopic growth measurements were supplemented with chemical analyses of the samples, including inorganic ions and organic/elemental carbon. In addition, the microstructure and chemical composition of aerosol particles were analyzed by X-ray micro-spectroscopy (STXM-NEXAFS and transmission electron microscopy (TEM. A mass closure analysis indicates that organic carbon accounted for 61 and 38% of PM in the accumulation mode and coarse mode, respectively. The water soluble fraction of organic matter was estimated to be 52 and 8% of PM in these modes. Sulfate, predominantly in the form of ammoniated sulfate, was the dominant inorganic component in both size modes: ∼34% in the accumulation vs. ∼47% in the coarse mode. The hygroscopic growth measurements were conducted with a filter-based differential hygroscopicity analyzer (FDHA over the range of 5–99.4% RH in the hydration and dehydration operation modes. The FDHA study indicates that both accumulation and coarse modes exhibit pronounced water uptake approximately at the same RH, starting at ∼70%, while efflorescence occurred at different humidities, i.e., at ∼35% RH for submicron particles vs. ∼50% RH for supermicron particles. This ∼15% RH difference was attributed to higher content of organic material in the submicron particles, which suppresses water release in the dehydration experiments. The kappa mass interaction model (KIM was applied to characterize and parameterize non-ideal solution behavior and concentration-dependent water uptake by atmospheric aerosol samples in the 5–99.4% RH range. Based on KIM, the volume-based hygroscopicity parameter, κv, was calculated. The κv, ws value related to the water soluble (ws fraction was estimated to be ∼0

  1. Use of high-volume outdoor smog chamber photo-reactors for studying physical and chemical atmospheric aerosol formation and composition

    Science.gov (United States)

    Borrás, E.; Ródenas, M.; Vera, T.; Muñoz, A.

    2015-12-01

    The atmospheric particulate matter has a large impact on climate, biosphere behaviour and human health. Its study is complex because of large number of species are present at low concentrations and the continuous time evolution, being not easily separable from meteorology, and transport processes. Closed systems have been proposed by isolating specific reactions, pollutants or products and controlling the oxidizing environment. High volume simulation chambers, such as EUropean PHOtoREactor (EUPHORE), are an essential tool used to simulate atmospheric photochemical reactions. This communication describes the last results about the reactivity of prominent atmospheric pollutants and the subsequent particulate matter formation. Specific experiments focused on organic aerosols have been developed at the EUPHORE photo-reactor. The use of on-line instrumentation, supported by off-line techniques, has provided well-defined reaction profiles, physical properties, and up to 300 different species are determined in particulate matter. The application fields include the degradation of anthropogenic and biogenic pollutants, and pesticides under several atmospheric conditions, studying their contribution on the formation of secondary organic aerosols (SOA). The studies performed at the EUPHORE have improved the mechanistic studies of atmospheric degradation processes and the knowledge about the chemical and physical properties of atmospheric particulate matter formed during these processes.

  2. Estimated total emissions of trace gases from the Canberra Wildfires of 2003: a new method using satellite measurements of aerosol optical depth & the MOZART chemical transport model

    Directory of Open Access Journals (Sweden)

    C. Paton-Walsh

    2010-06-01

    Full Text Available In this paper we describe a new method for estimating trace gas emissions from large vegetation fires using satellite measurements of aerosol optical depth (AOD at 550 nm, combined with an atmospheric chemical transport model. The method uses a threshold value to screen out normal levels of AOD that may be caused by raised dust, sea salt aerosols or diffuse smoke transported from distant fires. Using this method we infer an estimated total emission of 15±5 Tg of carbon monoxide, 0.05±0.02 Tg of hydrogen cyanide, 0.11±0.03 Tg of ammonia, 0.25±0.07 Tg of formaldehyde, 0.03±0.01 of acetylene, 0.10±0.03 Tg of ethylene, 0.03±0.01 Tg of ethane, 0.21±0.06 Tg of formic acid and 0.28±0.09 Tg of methanol released to the atmosphere from the Canberra fires of 2003. An assessment of the uncertainties in the new method is made and we show that our estimate agrees (within expected uncertainties with estimates made using current conventional methods of multiplying together factors for the area burned, fuel load, the combustion efficiency and the emission factor for carbon monoxide. A simpler estimate derived directly from the satellite AOD measurements is also shown to be in agreement with conventional estimates, suggesting that the method may, under certain meteorological conditions, be applied without the complication of using a chemical transport model. The new method is suitable for estimating emissions from distinct large fire episodes and although it has some significant uncertainties, these are largely independent of the uncertainties inherent in conventional techniques. Thus we conclude that the new method is a useful additional tool for characterising emissions from vegetation fires.

  3. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, Seisuke, E-mail: seisuke@riken.jp [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan); Sugioka, Koji; Midorikawa, Katsumi [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan)

    2009-09-30

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  4. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Science.gov (United States)

    Nakashima, Seisuke; Sugioka, Koji; Midorikawa, Katsumi

    2009-09-01

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  5. Chemical Characteristics of Particulate Matter from Vehicle emission using High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS)

    Science.gov (United States)

    Park, T.; Lee, T.; Kang, S.; Lee, J.; Kim, J.; Son, J.; Yoo, H. M.; Kim, K.; Park, G.

    2015-12-01

    Car emissions are major contributors of particulate matter (PM) in the urban environment and effects of air pollution, climate change, and human activities. By increasing of interest in research of car emission for assessment of the PM control, it became require to understand the chemical composition and characteristics of the car exhaust gases and particulate matter. To understand car emission characteristics of PM, we will study PM of car emissions for five driving modes (National Institute Environmental Research (NIER)-5, NIER-9, NIER-12, NIER-14) and three fixed speed driving modes (30km/h, 70km/h, 110km/h) using different fuel types (gasoline, diesel, and LPG) at Transportation Pollution Research Center (TPRC) of NIER in Incheon, South Korea. PM chemical composition of car emission was measured for concentrations of organics, sulfate, nitrate, ammonium, PAHs, oxidation states and size distribution using an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and engine exhaust particle sizer (EEPS) on real-time. In the study, organics concentration was dominated for all cases of driving modes and the concentration of organics was increased in 110km/h fixed speed mode for gasoline and diesel. The presentation will provide an overview of the chemical composition of PM in the car emissions.

  6. Intercomparison of modal and sectional aerosol microphysics representations within the same 3-D global chemical transport model

    Directory of Open Access Journals (Sweden)

    G. W. Mann

    2012-01-01

    Full Text Available A global modal aerosol microphysics module (GLOMAP-mode is evaluated and improved by comparing against a sectional version (GLOMAP-bin and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that various size distribution parameter settings (mode widths and inter-modal separation sizes resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Surface mass of sulphate, sea-salt, black carbon (BC and organic carbon (OC are, on the annual mean, within 25 % in the two schemes in nearly all regions. On the annual mean, surface level concentrations of condensation nuclei (CN, cloud condensation nuclei (CCN, surface area density and condensation sink also compare within 25 % in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically higher in the modal scheme, by 25–60 %, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2–4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin-mode differences are much less than model-observation differences, although some processes are missing in these runs which may pose a bigger challenge to modal schemes (e.g. boundary layer nucleation, ultra-fine sea-spray. The findings here underline the need for a spectrum of complexity in global models, with size-resolved aerosol properties

  7. Direct Fabrication of Carbon Nanotubes STM Tips by Liquid Catalyst-Assisted Microwave Plasma-Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Fa-Kuei Tung

    2009-01-01

    Full Text Available Direct and facile method to make carbon nanotube (CNT tips for scanning tunneling microscopy (STM is presented. Cobalt (Co particles, as catalysts, are electrochemically deposited on the apex of tungsten (W STM tip for CNT growth. It is found that the quantity of Co particles is well controlled by applied DC voltage, concentration of catalyst solution, and deposition time. Using optimum growth condition, CNTs are successfully synthesized on the tip apex by catalyst-assisted microwave-enhanced chemical vapor deposition (CA-MPECVD. A HOPG surface is clearly observed at an atomic scale using the present CNT-STM tip.

  8. Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

    OpenAIRE

    Lingyu Kong; Binayak Dasgupta; Yi Ren; Parsian K. Mohseni; Minghui Hong; Xiuling Li; Wai Kin Chim; Sing Yang Chiam

    2016-01-01

    In this work, we investigate the transport processes governing the metal-assisted chemical etching (MacEtch) of silicon (Si). We show that in the oxidation of Si during the MacEtch process, the transport of the hole charges can be accomplished by the diffusion of metal ions. The oxidation of Si is subsequently governed by a redox reaction between the ions and Si. This represents a fundamentally different proposition in MacEtch whereby such transport is understood to occur through hole carrier...

  9. Chemical characterization and source apportionment of PM2.5 aerosols in a megacity of Southeast China

    Science.gov (United States)

    Li, Huiming; Wang, Qin'geng; Yang, Meng; Li, Fengying; Wang, Jinhua; Sun, Yixuan; Wang, Cheng; Wu, Hongfei; Qian, Xin

    2016-11-01

    PM2.5 aerosol samples were collected during a haze-fog event in winter, as well as in spring, summer, and fall in 2013 within an urban area (Xianlin) and city center area (Gulou) of Nanjing, a megacity of SE China. The PM2.5 showed typical seasonality of waxing in winter and waning in summer or fall with annual average concentrations of 145 and 139 μg/m3 in Xianlin and Gulou, respectively. Concentrations of SO42 -, NO3-, NH4+, Cl-, and K+, EC, OC, secondary organic carbon, and most elements were elevated in winter. The sulfur oxidation ratio and concentrations of SO42 - and Cl- were significantly higher in Xianlin than Gulou (p S4 The enrichment factors (EF) obtained in four seasons in Xianlin (a) and Gulou (b). Fig. S5 Estimated versus observed PM2.5 mass concentrations during sampling period in the two areas (95% confidence interval).

  10. A Comparison Analysis of Chemical Composition of Aerosols in the Dust and Non-Dust Periods in Beijing

    Institute of Scientific and Technical Information of China (English)

    张仁健; 徐永福; 韩志伟

    2004-01-01

    Dust events occurred frequently in Beijing in recent years. In this work, 120 aerosol samples were collected in two typical dust events (21-22 March and 15 May) and a non-dust period in Beijing from March to May 2001. Samples were analyzed for major elemental components by the Proton Induced Xray Emission (PIXE) method. Results show that the enrichment factors of crustal elements such as Mg,Al, and Ti had little differences between the dust period and the non-dust period in Beijing, while the enrichment factors of other elements that have a relation to anthropogenic emissions were very low during the dust period. The results derived by using multivariate factor analysis from the observation data show that the sources such as soil dust, industry, and fuel combustion were among the major contributors to the particles in Beijing.

  11. Chemical characterization of aerosols at the summit of Mountain Tai in the middle of central east China

    Directory of Open Access Journals (Sweden)

    C. Deng

    2010-09-01

    Full Text Available PM2.5 and TSP samples were collected at the summit of Mountain Tai (MT (1534 m a.s.l. in spring 2006/2007 and summer 2006 to investigate the characteristics of aerosols over central eastern China. For comparison, aerosol samples were also collected at Tazhong, Urumqi, Tianchi in Xinjiang in northwestern China, Duolun and Yulin in northern China, and two urban sites in the megacities, Beijing and Shanghai, in spring 2007. Daily mass concentrations of TSP and PM2.5 ranged from 39.6–276.9 μg/m3 and 17.2–235.7 μg/m3 respectively at the summit of MT. Averaged concentrations of PM2.5 showed a pronounced seasonal variation with higher concentration in summer than spring. 17 water-soluble ions (SO42−, NO3, Cl, F, PO43−, NO2, CH3COO, CH2C2O42−, C2H4C2O42−, HCOO, MSA, C2O42−, NH4+, Ca2+, K+, Mg2+, Na+, and 19 elements of 176 samples from MT were measured. SO42−, NO3, and NH4+ were the major water-soluble species in PM2.5, accounting for 61.5% and 73.8% of the total measured ions in spring and summer, respectively. The average ratio of PM2.5/TSP was 0.37(2006 and 0.49(2007 in spring, while up to 0.91 in summer, suggesting that aerosol particles were primarily comprised of fine particles in summer and of considerable coarse particles in spring. Crustal elements (e.g., Ca, Mg, Al, Fe, etc. showed higher concentration in spring than summer, while most pollution species (SO42−, NO3, K

  12. Origins of atmospheric aerosols. Basic concepts on aerosol main physical properties; L`aerosol atmospherique: ses origines quelques notions sur les principales proprietes physiques des aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Renoux, A. [Paris-12 Univ., 94 - Creteil (France). Laboratoire de Physique des aerosols et de transferts des contaminations

    1996-12-31

    Natural and anthropogenic sources of atmospheric aerosols are reviewed and indications of their concentrations and granulometry are given. Calculation of the lifetime of an atmospheric aerosol of a certain size is presented and the various modes of aerosol granulometry and their relations with photochemical and physico-chemical processes in the atmosphere are discussed. The main physical, electrical and optical properties of aerosols are also presented: diffusion coefficient, dynamic mobility and relaxation time, Stokes number, limit rate of fall, electrical mobility, optical diffraction

  13. Acidic aerosol in urban air

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, M.; Yamaoka, S.; Miyazaki, T.; Oka, M.

    1982-01-01

    The distribution and chemical composition of acidic aerosol in Osaka City were investigated. Samples were collected at five sites in the city from June to September, 1979. Acidic aerosol was determined by the acid-base titration method, sulfate ion by barium chloride turbidimetry, nitrate ion by the xylenol method, and chloride ion by the mercury thiocyanate method. The concentration of acidic aerosol at five sites ranged from 7.7 micrograms per cubic meter to 10.0 micrograms per cubic meter, but mean concentrations in the residential area were slightly higher than those in the industrial area. When acidic aerosol concentrations were compared with concentrations of sulfate, nitrate, and chloride ions, a significant correlation was found between acidic aerosol and sulfate ion. The sum of the ion equivalents of the three types showed good correlation with the acidic aerosol equivalent during the whole period.

  14. Microwave assisted rapid growth of Mg(OH){sub 2} nanosheet networks for ethanol chemical sensor application

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hazmi, Faten [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Umar, Ahmad, E-mail: ahmadumar786@gmail.com [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Dar, G.N. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Al-Ghamdi, A.A.; Al-Sayari, S.A. [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Al-Hajry, A. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Department of Physics, College of Science and Arts, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Kim, S.H. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Al-Tuwirqi, Reem M. [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Alnowaiserb, Fowzia [Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); El-Tantawy, Farid [Department of Physics, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-04-05

    Highlights: Black-Right-Pointing-Pointer A facile microwave-assisted synthesis and characterizations of magnesium hydroxide (Mg(OH){sub 2}) nanosheet networks. Black-Right-Pointing-Pointer Fabrication of ethanol sensor based on (Mg(OH){sub 2}) nanosheet networks. Black-Right-Pointing-Pointer Good sensitivity ({approx}3.991 {mu}A cm{sup -2} mM{sup -1}) and lower detection limit (5 {mu}M). Black-Right-Pointing-Pointer This research opens a way to utilize Mg(OH){sub 2} nanostructures for chemical sensors applications. - Abstract: This paper reports a facile microwave-assisted synthesis of magnesium hydroxide (Mg(OH){sub 2}) nanosheet networks and their utilization for the fabrication of efficient ethanol chemical sensor. The synthesized nanosheets networks were characterized in terms of their morphological, structural and optical properties using various analysis techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The detailed morphological and structural investigations reveal that the synthesized (Mg(OH){sub 2}) products are nanosheet networks, grown in high density, and possessing hexagonal crystal structure. The optical band gap of as-synthesized Mg(OH){sub 2} nanosheet networks was examined by UV-Vis absorption spectrum, and found to be 5.76 eV. The synthesized nanosheet networks were used as supporting matrices for the fabrication of I-V technique based efficient ethanol chemical sensor. The fabricated ethanol sensor based on nanosheet networks exhibits good sensitivity ({approx}3.991 {mu}A cm{sup -2} mM{sup -1}) and lower detection limit (5 {mu}M), with linearity (R = 0.9925) in short response time (10.0 s). This work demonstrate that the simply synthesized Mg(OH){sub 2} nanosheet networks can effectively be used for the fabrication of efficient ethanol chemical sensors.

  15. Comparison of secondary organic aerosol formed with an aerosol flow reactor and environmental reaction chambers: effect of oxidant concentration, exposure time and seed particles on chemical composition and yield

    Directory of Open Access Journals (Sweden)

    A. T. Lambe

    2014-12-01

    Full Text Available We performed a systematic intercomparison study of the chemistry and yields of SOA generated from OH oxidation of a common set of gas-phase precursors in a Potential Aerosol Mass (PAM continuous flow reactor and several environmental chambers. In the flow reactor, SOA precursors were oxidized using OH concentrations ranging from 2.0×108 to 2.2×1010 molec cm−3 over exposure times of 100 s. In the environmental chambers, precursors were oxidized using OH concentrations ranging from 2×106 to 2×107 molec cm−3 over exposure times of several hours. The OH concentration in the chamber experiments is close to that found in the atmosphere, but the integrated OH exposure in the flow reactor can simulate atmospheric exposure times of multiple days compared to chamber exposure times of only a day or so. A linear correlation analysis of the mass spectra (m=0.91–0.92, r2=0.93–0.94 and carbon oxidation state (m=1.1, r2=0.58 of SOA produced in the flow reactor and environmental chambers for OH exposures of approximately 1011 molec cm−3 s suggests that the composition of SOA produced in the flow reactor and chambers is the same within experimental accuracy as measured with an aerosol mass spectrometer. This similarity in turn suggests that both in the flow reactor and in chambers, SOA chemical composition at low OH exposure is governed primarily by gas-phase OH oxidation of the precursors, rather than heterogeneous oxidation of the condensed particles. In general, SOA yields measured in the flow reactor are lower than measured in chambers for the range of equivalent OH exposures that can be measured in both the flow reactor and chambers. The influence of sulfate seed particles on isoprene SOA yield measurements was examined in the flow reactor. The studies show that seed particles increase the yield of SOA produced in flow reactors by a factor of 3 to 5 and may also account in part for higher SOA yields obtained in the chambers, where seed

  16. Applications of aerosol model in the reactor containment

    Directory of Open Access Journals (Sweden)

    Mossad Slama

    2014-10-01

    For spatially homogeneous aerosol of uniform chemical composition, the aerosol dynamic equation is solved in closed volume to simulate the radionuclide particle transport in the containment. The effects of initial conditions on the aerosol distribution, boundary layer thickness and the aerosol behaviour under source reinforcement (external source are considered.

  17. Chemical Characterization and Source Apportionment of Size Fractionated Atmospheric Aerosols, and, Evaluating Student Attitudes and Learning in Large Lecture General Chemistry Classes

    Science.gov (United States)

    Allen, Gregory Harold

    Chemical speciation and source apportionment of size fractionated atmospheric aerosols were investigated using laser desorption time-of-flight mass spectrometry (LD TOF-MS) and source apportionment was carried out using carbon-14 accelerator mass spectrometry (14C AMS). Sample collection was carried out using the Davis Rotating-drum Unit for Monitoring impact analyzer in Davis, Colfax, and Yosemite, CA. Ambient atmospheric aerosols collected during the winter of 2010/11 and 2011/12 showed a significant difference in the types of compounds found in the small and large sized particles. The difference was due to the increase number of oxidized carbon species that were found in the small particles size ranges, but not in the large particles size ranges. Overall, the ambient atmospheric aerosols collected during the winter in Davis, CA had and average fraction modern of F14C = 0.753 +/- 0.006, indicating that the majority of the size fractionated particles originated from biogenic sources. Samples collected during the King Fire in Colfax, CA were used to determine the contribution of biomass burning (wildfire) aerosols. Factor analysis was used to reduce the ions found in the LD TOF-MS analysis of the King Fire samples. The final factor analysis generated a total of four factors that explained an overall 83% of the variance in the data set. Two of the factors correlated heavily with increased smoke events during the sample period. The increased smoke events produced a large number of highly oxidized organic aerosols (OOA2) and aromatic compounds that are indicative of biomass burning organic aerosols (WBOA). The signal intensities of the factors generated in the King Fire data were investigated in samples collected in Yosemite and Davis, CA to look at the impact of biomass burning on ambient atmospheric aerosols. In both comparison sample collections the OOA2 and WBOA factors both increased during biomass burning events located near the sampling sites. The correlation

  18. The effect of meteorological and chemical factors on the agreement between observations and predictions of fine aerosol composition in southwestern Ontario during BAQS-Met

    Directory of Open Access Journals (Sweden)

    M. Z. Markovic

    2011-04-01

    Full Text Available The Border Air Quality and Meteorology Study (BAQS-Met was an intensive, collaborative field campaign during the summer of 2007 that investigated the effects of transboundary pollution, local pollution, and local meteorology on air quality in southwestern Ontario. This analysis focuses on the measurements of the inorganic constituents of particulate matter with diameter of less than 1 μm (PM1, with a specific emphasis on nitrate. We evaluate the ability of AURAMS, Environment Canada's chemical transport model, to represent regional air pollution in SW Ontario by comparing modelled aerosol inorganic chemical composition with measurements from Aerosol Mass Spectrometers (AMS onboard the National Research Council (NRC of Canada Twin Otter aircraft and at a ground site in Harrow, ON. The agreement between modelled and measured pNO3 at the ground site (observed mean (Mobs = 0.50 μg m−3; modelled mean (Mmod = 0.58 μg m−3; root mean square error (RSME = 1.27 μg m−3 was better than aloft (Mobs = 0.32 μg m−3; Mmod = 0.09 μg m−3; RSME = 0.48 μg m−3. Possible reasons for discrepancies include errors in (i emission inventories, (ii atmospheric chemistry, (iii predicted meteorological parameters, or (iv gas/particle thermodynamics in the model framework. Using the inorganic thermodynamics model, ISORROPIA, in an offline mode, we find that the assumption of thermodynamic equilibrium is consistent with observations of gas and particle composition at Harrow. We develop a framework to assess the sensitivity of PM1 nitrate to meteorological and chemical parameters and find that errors in both the predictions of relative humidity and free ammonia (FA ≡ NH3(g + pNH4+ − 2 · pSO42- are responsible for

  19. The effect of meteorological and chemical factors on the agreement between observations and predictions of fine aerosol composition in Southwestern Ontario during BAQS-Met

    Directory of Open Access Journals (Sweden)

    M. Z. Markovic

    2010-10-01

    Full Text Available The Border Air Quality and Meteorology Study (BAQS-Met was an intensive, collaborative field campaign during the summer of 2007 that investigated the effects of transboundary pollution, local pollution, and local meteorology on regional air quality in Southwestern Ontario. This analysis focuses on the measurements of the inorganic constituents of particulate matter with diameter of less than 1 μm (PM1, with a specific emphasis on nitrate. We evaluate the ability of AURAMS, the Environment Canada's chemical transport model, to represent regional air pollution in SW Ontario by comparing modelled aerosol inorganic chemical composition with measurements from Aerosol Mass Spectrometers (AMS onboard the National Research Council (NRC of Canada Twin Otter aircraft and at a ground site in Harrow, ON. The agreement between modelled and measured pNO3 at the ground site (observed mean (M_obs = 0.50 μg m−3; modelled mean (M_mod = 0.58 μg m−3; root mean square error (RSME = 1.27 μg m−3 was better than aloft (M_obs = 0.32 μg m−3; M_mod = 0.09 μg m−3; RSME = 0.48 μg m−3. Possible reasons for discrepancies include errors in (i emission inventories, (ii atmospheric chemistry, (iii predicted meteorological parameters, or (iv gas/particle thermodynamics in the model framework. Using the inorganic thermodynamics model, ISORROPIA, in an offline mode, we find that the assumption of thermodynamic equilibrium is consistent with observations of gas and particle composition at Harrow. We develop a framework to assess the sensitivity of PM1 nitrate to meteorological and chemical parameters and find that errors in both the predictions of relative humidity and free ammonia (FA ≡ NH3(g + NH4+ − SO42− are responsible for the poor agreement between modelled and measured values.

  20. Sources of chemical species in rainwater during monsoon and non-monsoonal periods over two mega cities in India and dominant source region of secondary aerosols

    Science.gov (United States)

    Rao, P. S. P.; Tiwari, S.; Matwale, J. L.; Pervez, S.; Tunved, P.; Safai, P. D.; Srivastava, A. K.; Bisht, D. S.; Singh, S.; Hopke, P. K.

    2016-12-01

    Samples of rainwater (RW) were collected to characterize the chemistry and sources in two representative megacities at Pune (Southwest) and Delhi (Northern) India from 2011 to 2014 across two seasons: monsoon (MN) and non-monsoon (NMN). Collected RW samples were analyzed for major chemical constituents (F-, Cl-, SO42-, NO3-, NH4+, Na+, K+, Ca2+, and Mg2+), pH and conductivity. In addition, bicarbonate (HCO3-) was also estimated. The mean pH values of the RW were >6 at Pune and pollution effects in these Indian mega cities. Both the Ca2+ and SO42- were the dominant ions, accounting for 43% (Pune) and 54% (Delhi) of the total ions. The sum of measured ions during the NMN period was greater than the NM period by a factor of 1.5 for Pune (278.4: NM and 412.1: NMN μeq/l) and a factor of about 2.5 for Delhi (406 and 1037.7 μeq/l). The contributions of SO42- and NO3- to the RW acidity were ∼40% and 60%, respectively, at Pune and correspondingly, 36% and 64% at Delhi. The concentrations of secondary aerosols (SO42-and NO3-) were higher by a factor of two and three when the air masses were transported to Pune from the continental side. At Delhi, the concentrations of SO42-, NO3-, Ca2+, and Mg2+ were significantly higher when the air masses arrive from Punjab, Haryana, and Pakistan indicating the greater atmospheric pollution over the Indo-Gangetic Plain. Positive matrix factorization was applied to the source apportionment of the deposition fluxes of these ions. Three factors were obtained for Pune and four for Delhi. The sources at Pune were secondary aerosols from fossil fuel combustion, soil dust, and marine, whereas, at Delhi, the sources were soil, fossil fuel combustion, biomass burning, and industrial chlorine.

  1. Seasonal variations and sources of mass and chemical composition for PM10 aerosol in Hangzhou,China

    Institute of Scientific and Technical Information of China (English)

    Junji Cao; Zhenxing Shen; Judith C.Chow; Guowei Qi; John G.Watsonc

    2009-01-01

    Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM10 mass, 22 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Cd, Ba, and Pb), 5 major ions (F-, Cl-, NO3-, SO42-, and NH4+), and organic and elemental carbon (OC and EC), showing that PM10 mass ranged from 46.7 to 270.8 μg/m3, with an annual average of 119.2 μg/m3. Na, AI, Si, S. K, Ca, and Fe were the most abundant elements in PM10, most ors being in the form of SO42-. SO42-, NO4-, and NH4+ were the major ions, which contributed to about 20%; of the PM10 mass. The mean seasonal concentrations for SO42- , averaged over all sites, were found to be 18.0, 18.5, 24.Z and 21.4 μg/m3. for spring, summer, autumn, and winter, respectively, while the corresponding Ioadings for NO3- were 72, 4.7, 7.1, and 11.2μg/m3. and for NH4+ were 6.0, 5.9, 8.2. and 9.3 μg/m3, in the form mostly of NH4NO3 in spring, autumn, and winter, and mostly of (NH4)2SO4 in summer. The low NO3-/SO42- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM10 were found to be 21A, and 4.1 μg/m3, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM10 for the four seasons, as is characteristic for cities in South China.

  2. Instrumentation for tropospheric aerosol characterization

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.; Young, S.E.; Becker, C.H.; Coggiola, M.J. [SRI International, Menlo Park, CA (United States); Wollnik, H. [Giessen Univ. (Germany)

    1997-12-31

    A new instrument has been developed that determines the abundance, size distribution, and chemical composition of tropospheric and lower stratospheric aerosols with diameters down to 0.2 {mu}m. In addition to aerosol characterization, the instrument also monitors the chemical composition of the ambient gas. More than 25.000 aerosol particle mass spectra were recorded during the NASA-sponsored Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) field program using NASA`s DC-8 research aircraft. (author) 7 refs.

  3. US technical assistance to the IAEA and the chemical weapons convection (CWC) - a review and look to the future

    Energy Technology Data Exchange (ETDEWEB)

    Indusi, J.; Parsick, R.J.; Reisman, A.W.

    1997-08-01

    This paper reviews the Safeguards mandate of the International Atomic Energy Agency (IAEA) and describes U.S. technical support programs. We also review the mandate of the Chemical Weapons Convention (CWC) and speculate on the technical areas where U.S. assistance may prove useful. The IAEA was organized in 1957 in response to President Eisenhower`s {open_quotes}Atoms for Peace{close_quotes} initiative presented to the UN General Assembly on December 8, 1953. The Organization for the Prohibition of Chemical Weapons (OPCW) has been organized by a Preparatory Commission (PREPCOM) to prepare for the entry-into-force of this new convention which prohibits the development, production, stockpiling and use of chemical weapons and on their destruction. The safeguards mandate of the IAEA is to carry out verifications of nuclear material pursuant to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and other voluntary but legally binding agreements. U.S. technical support programs have provided and continue to provide assistance in the form of Cost-Free Experts (CFE`s), systems studies on new safeguards approaches, training, computerized information systems, and equipment for nuclear materials measurements and containment and surveillance systems. Because the CWC just recently entered into force (April 29, 1997), verification procedures of the OPCW are not yet fully developed. However, it is expected, and can already be seen for many aspects of the technical task, that there are many similarities between the verification activities of the OPCW and those carried out by the IAEA. This paper will discuss potential technical support areas that can help strengthen the OPCW. 9 refs.

  4. The combined influence of chemical, metallurgical and mechanical factors on environment assisted cracking

    Science.gov (United States)

    Williams, D. P., III; Pao, P. S.; Wei, R. P.

    1979-01-01

    The principal aim of the paper is to re-emphasize and focus on both the multidisciplinary nature of the environment assisted cracking or embrittlement phenomenon. The multiplicity of factors involved in the embrittlement process is indicated, the mutual dependence of these factors and the influences of mechanical and environmental conditions are considered, and the interactions of various factors in determining the overall embrittlement response are discussed. The need for an interdisciplinary approach for resolving the major differences and for understanding embrittlement is outlined.

  5. Highly efficient and reliable chemically assisted enucleation method for handmade cloning in cattle

    DEFF Research Database (Denmark)

    Vajta, Gábor; Maddox-Hyttel, Poul; Skou, Christina T.

    2005-01-01

    The purpose of the present study was to find an efficient and reliable assisted procedure for enucleation related to the handmade cloning (HMC) technique. After in vitro maturation oocytes were incubated in 0.5 µgmL-¹ demecolcine for 2 h. Subsequently, zonae pellucidae were digested with pronase...... ultrastructure of the oocyte organelles, however, appeared to be unaltered by the treatments. Considering that no oocyte selection based on polar body presence was performed, this system seems to be more efficient and reliable than any other enucleation method. Moreover, expensive equipment (inverted...

  6. Evaluation of chemical transport model predictions of primary organic aerosol for air masses classified by particle-component-based factor analysis

    Directory of Open Access Journals (Sweden)

    C. A. Stroud

    2012-02-01

    Full Text Available Observations from the 2007 Border Air Quality and Meteorology Study (BAQS-Met 2007 in southern Ontario (ON, Canada, were used to evaluate Environment Canada's regional chemical transport model predictions of primary organic aerosol (POA. Environment Canada's operational numerical weather prediction model and the 2006 Canadian and 2005 US national emissions inventories were used as input to the chemical transport model (named AURAMS. Particle-component-based factor analysis was applied to aerosol mass spectrometer measurements made at one urban site (Windsor, ON and two rural sites (Harrow and Bear Creek, ON to derive hydrocarbon-like organic aerosol (HOA factors. Co-located carbon monoxide (CO, PM2.5 black carbon (BC, and PM1 SO4 measurements were also used for evaluation and interpretation, permitting a detailed diagnostic model evaluation.

    At the urban site, good agreement was observed for the comparison of daytime campaign PM1 POA and HOA mean values: 1.1 μg m−3 vs. 1.2 μg m−3, respectively. However, a POA overprediction was evident on calm nights due to an overly-stable model surface layer. Biases in model POA predictions trended from positive to negative with increasing HOA values. This trend has several possible explanations, including (1 underweighting of urban locations in particulate matter (PM spatial surrogate fields, (2 overly-coarse model grid spacing for resolving urban-scale sources, and (3 lack of a model particle POA evaporation process during dilution of vehicular POA tail-pipe emissions to urban scales. Furthermore, a trend in POA bias was observed at the urban site as a function of the BC/HOA ratio, suggesting a possible association of POA underprediction for diesel combustion sources. For several time periods, POA overprediction was also observed for sulphate-rich plumes, suggesting that our model POA fractions for the PM2.5 chemical

  7. A plug flow model for chemical reactions and aerosol nucleation and growth in an alkali-containing flue gas

    DEFF Research Database (Denmark)

    Christensen, K. A.; Livbjerg, Hans

    2000-01-01

    multicomponent growth models are treated. The local gas phase composition is determined from a gas phase chemical equilibrium calculation combined with finite reaction rate kinetics for slower reactions. The model is useful in the analysis of boiler operation with respect to the formation of particles, HCl, SO2......The paper presents a numerical model for the simulation of gas to particle conversion and the chemical changes during cooling of a flue gas from the combustion of fuels rich in volatile alkali species. For the homogeneous nucleation of alkali species the model uses the classical theory modified...

  8. Effect of MW-assisted roasting on nutritional and chemical properties of hazelnuts

    Directory of Open Access Journals (Sweden)

    Fatih Kalkan

    2015-12-01

    Full Text Available In order to enhance the flavor, texture, color, and appearance of hazelnuts, they are roasted during postharvest processing. In this study, raw hazelnuts (Corylus avellana L. were roasted using microwave (MW and MW-assisted hot air methods under various roasting conditions. The hazelnuts roasted were then examined to determine the percent DPPH radical scavenging activity, antioxidant capacity, total phenolic content, resistant starch, non-resistant starch, total starch, and protein concentration. The roasting experiments were done using a completely randomized factorial arrangement of two roasting types by three roasting times (9, 15, and 21 min by three roasting temperatures (70, 90, and 110°C using three replications within each experiment. These roasting methods were found to yield significant differences in antioxidant capacity, total phenolic content, resistant starch, non-resistant starch, and protein concentration between MW and MW-assisted hot air roasting processes, while no difference was found in percent DPPH radical scavenging activity and total starch. The results obtained may be of great importance to the food research community and industrial hazelnut roasting technologies.

  9. Social support net for chemically dependents: ecomap as instrumental in health assistance

    Directory of Open Access Journals (Sweden)

    Layana de Paula Cavalcante

    2012-06-01

    Full Text Available The social support net is composed by the group of bonds related to the individual. Taking into account that the quality, as well as the quantity of these bonds can interfere in the person's life, acting as positive or negative element, it was identified the need to know this net of relationships by the professionals that takes care of such individuals. It was aimed to assess the Ecomap of drug users assisted in a specialized service as instrumental of support for health care. This is a qualitative research carried out with 19 subjects assisted in a public service, through the Ecomap elaboration. Results show that CAPSad, family and religion constituted strong ties; work, colleagues and friends, links to be strengthened. Neighbors and former fellow drugs users were mentioned as stressors. Ecomap was an evaluation instrument that can be used to help the user to work his bonds, with special reference to those that need to be kept, broken or strengthened as social support.

  10. Chemical characteristics of aerosols in MABL of Bay of Bengal and Arabian Sea during spring inter-monsoon: A comparative study

    Indian Academy of Sciences (India)

    Ashwini Kumar; A K Sudheer; M M Sarin

    2008-07-01

    The chemical composition of aerosols in the Marine Atmospheric Boundary Layer (MABL) of Bay of Bengal (BoB) and Arabian Sea (AS) has been studied during the spring and inter-monsoon (March–May 2006) based on the analysis of water soluble constituents (Na+, NH$^{+}_{4}$, K+, Mg2+, Ca2+, Cl−, NO$^{−}_{3}$ and SO$^{2−}_{4}$), crustal elements (Al, Fe, and Ca) and carbonaceous species (EC, OC). The total suspended particulates (TSP) ranged from 5.2 to 46.6 g m−3 and 8.2 to 46.9 g m−3 during the sampling transects in the BoB and AS respectively. The water-soluble species, on average, accounted for 44% and 33% of TSP over BoB and AS respectively, with dominant contribution of SO$^{2−}_{4}$ over both the oceanic regions. However, distinct differences with respect to elevated abundances of NH$^{+}_{4}$ in the MABL of BoB and that of Na+ and Ca2+ in AS are clearly evident. The non-sea-salt component of SO$^{2−}_{4}$ ranging from 82 to 98% over BoB and 35 to 98% over AS; together with nss-Ca2+/nss-$SO^{2−}_{4}$ equivalent ratios 0.12 to 0.5 and 0.2 to 1.16, respectively, provide evidence for the predominance of anthropogenic constituents and chemical transformation processes occurring within MABL. The concentrations of OC and EC average around 1.9 and 0.4 g m−3 in BoB and exhibit a decreasing trend from north to south; however, abundance of these carbonaceous species are not significantly pronounced over AS. The abundance of Al, used as a proxy for mineral aerosols, varied from 0.2 to 1.9 g m−3 over BoB and AS, with a distinctly different spatial pattern – decreasing north to south in BoB in contrast to an increasing pattern in the Arabian Sea.

  11. Physico-chemical study of the anthropic aerosol and of its evolutions in Beijing; Etude physico-chimique de l'aerosol anthropique et de ses evolutions a Pekin

    Energy Technology Data Exchange (ETDEWEB)

    Guinot, B

    2006-05-15

    Beijing aerosols are characterised for the 2003-2004 period using an inclusive experimental set up for aerosol mass, chemistry and number, deployed at three sites. Aerosol size segregation in two fractions (fine and coarse) appears appropriated for source identification and investigations about gas-to-particle interactions. Several various sources contribute to air pollution: traffic, coal burning and industrial activities. The present study also shows how summer aerosol is influenced by the photochemical formation of secondary particles, and the significant amount of coarse and fine mineral dust all year long. Coal burning in winter has a lower influence than assessed in the past. The origin and altitude of the air masses entering Beijing are of key interest to understand the ageing of pollutants and their regional redistribution. By its expected effects onto these regional parameters, climate change may strongly affect Beijing air pollution in the coming decades. (author)

  12. Multi-wavelength Raman lidar, sunphotometric and aircraft measurements in combination with inversion models for the estimation of the aerosol optical and physico-chemical properties over Athens, Greece

    Directory of Open Access Journals (Sweden)

    R. E. Mamouri

    2012-01-01

    Full Text Available A novel procedure has been developed to retrieve, simultaneously, the optical, microphysical and chemical properties of tropospheric aerosols with a multi-wavelength Raman lidar system in the troposphere over an urban site (Athens, Greece: 37.9° N, 23.6° E, 200 m a.s.l. using data obtained during the European Space Agency (ESA THERMOPOLIS project which took place between 15–31 July 2009 over the Greater Athens Area (GAA. We selected to apply our procedure for a case study of intense aerosol layers occurred on 20–21 July 2009. The National Technical University of Athens (NTUA EOLE 6-wavelength Raman lidar system has been used to provide the vertical profiles of the optical properties of aerosols (extinction and backscatter coefficients, lidar ratio and the water vapor mixing ratio. An inversion algorithm was used to derive the mean aerosol microphysical properties (mean effective radius – reff, single-scattering albedo (ω and mean complex refractive index (m at selected heights in the 2–3 km height region. We found that reff was 0.3–0.4 μm, ω at 532 nm ranged from 0.63 to 0.88 and m ranged from 1.45 + 0.015i to 1.56 + 0.05i, in good accordance with in situ aircraft measurements. The final data set of the aerosol microphysical properties along with the water vapor and temperature profiles were incorporated into the ISORROPIA model to infer an in situ aerosol composition consistent with the retrieved m and ω values. The retrieved aerosol chemical composition in the 2–3 km height region gave a variable range of sulfate (0–60% and organic carbon (OC content (0–50%, although the OC content increased (up to 50% and the sulfate content dropped (up to 30% around 3 km height; in connection with the retrieved low ω value (0.63, indicates the presence of absorbing biomass burning smoke mixed with urban haze. Finally, the retrieved aerosol microphysical properties

  13. Adaptive Finite Element Method Assisted by Stochastic Simulation of Chemical Systems

    KAUST Repository

    Cotter, Simon L.

    2013-01-01

    Stochastic models of chemical systems are often analyzed by solving the corresponding Fokker-Planck equation, which is a drift-diffusion partial differential equation for the probability distribution function. Efficient numerical solution of the Fokker-Planck equation requires adaptive mesh refinements. In this paper, we present a mesh refinement approach which makes use of a stochastic simulation of the underlying chemical system. By observing the stochastic trajectory for a relatively short amount of time, the areas of the state space with nonnegligible probability density are identified. By refining the finite element mesh in these areas, and coarsening elsewhere, a suitable mesh is constructed and used for the computation of the stationary probability density. Numerical examples demonstrate that the presented method is competitive with existing a posteriori methods. © 2013 Society for Industrial and Applied Mathematics.

  14. MATRIX-VBS: implementing an evolving organic aerosol volatility in an aerosol microphysics model

    OpenAIRE

    Gao, Chloe Y.; Tsigaridis, Kostas; Bauer, Susanne E.

    2016-01-01

    We have implemented an existing aerosol microphysics scheme into a box model framework and extended it to represent gas-particle partitioning and chemical ageing of semi-volatile organic aerosols. We then applied this new research tool to investigate the effects of semi-volatile organic species on the growth, composition and mixing state of aerosol particles in case studies representing several different environments. The volatility-basis set (VBS) framework is implemented into the aerosol mi...

  15. Bias-assisted atomic force microscope nanolithography on NbS2 thin films grown by chemical vapor deposition

    Science.gov (United States)

    Bark, Hunyoung; Kwon, Sanghyuk; Lee, Changgu

    2016-12-01

    Niobium disulfide, one of the metallic transition metal dichalcogenides, has a high potential as an electrode material for electronic devices made of 2D materials. Here, we investigated the bias-assisted atomic force microscope nanolithography of NbS2 thin films synthesized by chemical vapor deposition. We analyzed the lithographed pattern using Raman spectroscopy, transmission electron microscopy and friction force microscopy. These analyses showed that lines having various widths and thicknesses could be generated using the lithography technique by simply varying the scan speed and applied voltage. These analyses also revealed that the NbS2 film transformed from a layered crystalline structure into an amorphous structure upon being lithographed. By generating four line segments forming a square and measuring I/V curves inside and outside of the square, the electrical properties of the lithographed material were characterized. These analyses indicate that NbS2 became hydrogenated and an insulator upon being lithographed.

  16. Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization

    Institute of Scientific and Technical Information of China (English)

    LI Guo-Fu; YU Hai-Jun; DUO Li-Ping; JIN Yu-Qi; WANG Jian; SANG Feng-Ting; FANG Ben-Jie; WANG De-Zhen

    2009-01-01

    The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2-2.9 kPa and single pulse energy is up to 180m J, the corresponding specific output energy is 1.0 J/L.

  17. Monte Carlo simulation of the behaviour of electrons during electron-assisted chemical vapour deposition of diamond

    Institute of Scientific and Technical Information of China (English)

    董丽芳; 陈俊英; 董国义; 尚勇

    2002-01-01

    The behaviour of electrons during electron-assisted chemical vapour deposition of diamond is investigated using Monte Carlo simulation. The electron energy distribution and velocity distribution are obtained over a wide range of reduced field E/N (the ratio of the electric field to gas molecule density) from 100 to 2000 in units of 1Td=10-17Vcm2.Their effects on the diamond growth are also discussed. Themain results obtained are as follows. (1) The velocity profile is asymmetric for the component parallel to the field.Ihe velocity distribution has a peak shift in the field direction. Most electrons possess non-zero velocity parallel to the substrate. (2) The number of atomic H is a function of E/N. (3) High-quality diamond can be obtained under the condition of E/N from 50 to 800Td due to sufficient atomic H and electron bombardment.

  18. The Enhanced Light Absorptance and Device Application of Nanostructured Black Silicon Fabricated by Metal-assisted Chemical Etching

    Science.gov (United States)

    Zhong, Hao; Guo, Anran; Guo, Guohui; Li, Wei; Jiang, Yadong

    2016-07-01

    We use metal-assisted chemical etching (MCE) method to fabricate nanostructured black silicon on the surface of C-Si. The Si-PIN photoelectronic detector based on this type of black silicon shows excellent device performance with a responsivity of 0.57 A/W at 1060 nm. Silicon nanocone arrays can be created using MCE treatment. These modified surfaces show higher light absorptance in the near-infrared range (800 to 2500 nm) compared to that of C-Si with polished surfaces, and the variations in the absorption spectra of the nanostructured black silicon with different etching processes are obtained. The maximum light absorptance increases significantly up to 95 % in the wavelength range of 400 to 2500 nm. Our recent novel results clearly indicate that nanostructured black silicon made by MCE has potential application in near-infrared photoelectronic detectors.

  19. Properties of Erbium Doped Hydrogenated Amorphous Carbon Layers Fabricated by Sputtering and Plasma Assisted Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    V. Prajzler

    2008-01-01

    Full Text Available We report about properties of carbon layers doped with Er3+ ions fabricated by Plasma Assisted Chemical Vapor Deposition (PACVD and by sputtering on silicon or glass substrates. The structure of the samples was characterized by X-ray diffraction and their composition was determined by Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. The Absorbance spectrum was taken in the spectral range from 400 nm to 600 nm. Photoluminescence spectra were obtained using two types of Ar laser (λex=514.5 nm, lex=488 nm and also using a semiconductor laser (λex=980 nm. Samples fabricated by magnetron sputtering exhibited typical emission at 1530 nm when pumped at 514.5 nm. 

  20. Optical properties of nanowire structures produced by the metal-assisted chemical etching of lightly doped silicon crystal wafers

    Energy Technology Data Exchange (ETDEWEB)

    Gonchar, K. A., E-mail: k.a.gonchar@gmail.com; Osminkina, L. A. [Moscow State University, Faculty of Physics (Russian Federation); Sivakov, V. [Leibniz Institute of Photonic Technology (Germany); Lysenko, V. [Institut National des Sciences Appliquées (INSA) de Lyon, Nanotechnology Institute of Lyon (France); Timoshenko, V. Yu. [Moscow State University, Faculty of Physics (Russian Federation)

    2014-12-15

    Layers of Si nanowires produced by the metal-assisted chemical etching of (100)-oriented single-crystal p-Si wafers with a resistivity of 1–20 Ω · cm are studied by reflectance spectroscopy, Raman spectros-copy, and photoluminescence measurements. The nanowire diameters are 20–200 nm. The wafers are supplied by three manufacturing companies and distinguished by their different lifetimes of photoexcited charge carriers. It is established that the Raman intensity for nanowires longer than 1 μm is 3–5 times higher than that for the substrates. The interband photoluminescence intensity of nanowires at the wavelength 1.12 μm is substantially higher than that of the substrates and reaches a maximum for samples with the longest bulk lifetime, suggesting a low nonradiative recombination rate at the nanowire surfaces.

  1. Microwave-assisted chemical reduction routes for direct synthesis of (fct) L1 phase of Fe-Pt.

    Science.gov (United States)

    Acharya, Smita; Singh, Kamal

    2011-01-01

    Microwave-assisted chemical reduction route has been explored for the direct synthesis of fct L1(0) - phase of Fe-Pt nanoparticles in the present work. Effects of microwave power and irradiation time on the growth process are systematically studied. Using this facile and high yield technique we could tune particle size from 7 to 17 nm. Prepared Fe-Pt NPs exhibited ordered face centered tetragonal (fct) L1(0) phase without any post-synthesis treatment. The particle size and magnetic properties of the prepared Fe-Pt were found to be very sensitive to the microwave irradiation power, while influence of exposure time was insignificant. The hysteresis measurements were performed at 300 K to study magnetic properties of the synthesized Fe-Pt as a function of crystallite size. Coercivity and saturation magnetization were observed to be decreasing with diminishing particle size. The microwave-assisted route is found to be a simple technique for direct synthesis of metal alloys and may prove to be a potential tool of high density data storage materials such as Fe-Pt.

  2. Diurnal Chemical Characterization of Aerosols at Downtown Mexico City During the Cold dry Seasons of 2003 and 2005. Part I. Data Validation

    Science.gov (United States)

    Grutter, M.; Moya, M.; Matias, E.; Baez, A.

    2006-12-01

    Data of size-differentiated (0.18-10 μm) and bulk (1, 2.5 μm) inorganic aerosols collected during February-March of 2003 and 2005 at a site near downtown Mexico City are analyzed and discussed in the present work. Physico-chemical consistency tests applied on the data base showed a reliability of 85%. Highest concentrations of PM occurred mainly in fine size ranges, i.e., accumulation mode (size-differentiated) and fine (PM1), specifically during the morning sampling periods. Sulfate, nitrate and ammonium were the dominant species though higher concentrations of NaCl were observed during the 2003 field campaign. Concentration of this species is explained in terms of the potential influence of the nearby dry salt-lake of Texcoco. Electroneutrality balances are achieved for all size ranges: PM10 (size-differentiated), PM2.5 and PM1 indicating the significant presence of gas-phase NH3 (> 40 ppb) observed consistently during the morning sampling periods in the Valley of Mexico was of importance in providing enough NH4+ to neutralize observed sulfate concentrations. Measured PM2.5 during the 2005 field campaign was exceeding several times the recent issued (November 2005) PM2.5 Mexican standard of 65 μg/m3.

  3. Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

    Directory of Open Access Journals (Sweden)

    Chen Dong

    2009-01-01

    Full Text Available Abstract This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD, energy-dispersive X-ray spectra (EDS, transmission electron microscopy (TEM, and high-resolution transmission electron microscopy (HRTEM. Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H2O2.

  4. Aqueous dispersions of few-layer-thick chemically modified magnesium diboride nanosheets by ultrasonication assisted exfoliation

    Science.gov (United States)

    Das, Saroj Kumar; Bedar, Amita; Kannan, Aadithya; Jasuja, Kabeer

    2015-01-01

    The discovery of graphene has led to a rising interest in seeking quasi two-dimensional allotropes of several elements and inorganic compounds. Boron, carbon’s neighbour in the periodic table, presents a curious case in its ability to be structured as graphene. Although it cannot independently constitute a honeycomb planar structure, it forms a graphenic arrangement in association with electron-donor elements. This is exemplified in magnesium diboride (MgB2): an inorganic layered compound comprising boron honeycomb planes alternated by Mg atoms. Till date, MgB2 has been primarily researched for its superconducting properties; it hasn’t been explored for the possibility of its exfoliation. Here we show that ultrasonication of MgB2 in water results in its exfoliation to yield few-layer-thick Mg-deficient hydroxyl-functionalized nanosheets. The hydroxyl groups enable an electrostatically stabilized aqueous dispersion and create a heterogeneity leading to an excitation wavelength dependent photoluminescence. These chemically modified MgB2 nanosheets exhibit an extremely small absorption coefficient of 2.9 ml mg−1 cm−1 compared to graphene and its analogs. This ability to exfoliate MgB2 to yield nanosheets with a chemically modified lattice and properties distinct from the parent material presents a fundamentally new perspective to the science of MgB2 and forms a first foundational step towards exfoliating metal borides. PMID:26041686

  5. G3 Assisted Rational Design of Chemical Sensor Array Using Carbonitrile Neutral Receptors

    Directory of Open Access Journals (Sweden)

    Yatimah Alias

    2013-10-01

    Full Text Available Combined computational and experimental strategies for the systematic design of chemical sensor arrays using carbonitrile neutral receptors are presented. Binding energies of acetonitrile, n-pentylcarbonitrile and malononitrile with Ca(II, Mg(II, Be(II and H+ have been investigated with the B3LYP, G3, CBS-QB3, G4 and MQZVP methods, showing a general trend H+ > Be(II > Mg(II > Ca(II. Hydrogen bonding, donor-acceptor and cation-lone pair electron simple models were employed in evaluating the performance of computational methods. Mg(II is bound to acetonitrile in water by 12.5 kcal/mol, and in the gas phase the receptor is more strongly bound by 33.3 kcal/mol to Mg(II compared to Ca(II. Interaction of bound cations with carbonitrile reduces the energies of the MOs involved in the proposed σ-p conjugated network. The planar malononitrile-Be(II complex possibly involves a π-network with a cationic methylene carbon. Fabricated potentiometric chemical sensors show distinct signal patterns that can be exploited in sensor array applications.

  6. Stratospheric Aerosol Measurements

    Science.gov (United States)

    Pueschel, Rudolf, F.; Gore, Warren J. (Technical Monitor)

    1998-01-01

    Stratospheric aerosols affect the atmospheric energy balance by scattering and absorbing solar and terrestrial radiation. They also can alter stratospheric chemical cycles by catalyzing heterogeneous reactions which markedly perturb odd nitrogen, chlorine and ozone levels. Aerosol measurements by satellites began in NASA in 1975 with the Stratospheric Aerosol Measurement (SAM) program, to be followed by the Stratospheric Aerosol and Gas Experiment (SAGE) starting in 1979. Both programs employ the solar occultation, or Earth limb extinction, techniques. Major results of these activities include the discovery of polar stratospheric clouds (PSCs) in both hemispheres in winter, illustrations of the impacts of major (El Chichon 1982 and Pinatubo 1991) eruptions, and detection of a negative global trend in lower stratospheric/upper tropospheric aerosol extinction. This latter result can be considered a triumph of successful worldwide sulfur emission controls. The SAGE record will be continued and improved by SAGE III, currently scheduled for multiple launches beginning in 2000 as part of the Earth Observing System (EOS). The satellite program has been supplemented by in situ measurements aboard the ER-2 (20 km ceiling) since 1974, and from the DC-8 (13 km ceiling) aircraft beginning in 1989. Collection by wire impactors and subsequent electron microscopic and X-ray energy-dispersive analyses, and optical particle spectrometry have been the principle techniques. Major findings are: (1) The stratospheric background aerosol consists of dilute sulfuric acid droplets of around 0.1 micrometer modal diameter at concentration of tens to hundreds of monograms per cubic meter; (2) Soot from aircraft amounts to a fraction of one percent of the background total aerosol; (3) Volcanic eruptions perturb the sulfuric acid, but not the soot, aerosol abundance by several orders of magnitude; (4) PSCs contain nitric acid at temperatures below 195K, supporting chemical hypotheses

  7. Ganges Valley Aerosol Experiment: Science and Operations Plan

    Energy Technology Data Exchange (ETDEWEB)

    Kotamarthi, VR

    2010-06-21

    The Ganges Valley region is one of the largest and most rapidly developing sections of the Indian subcontinent. The Ganges River, which provides the region with water needed for sustaining life, is fed primarily by snow and rainfall associated with Indian summer monsoons. Impacts of changes in precipitation patterns, temperature, and the flow of the snow-fed rivers can be immense. Recent satellite-based measurements have indicated that the upper Ganges Valley has some of the highest persistently observed aerosol optical depth values. The aerosol layer covers a vast region, extending across the Indo-Gangetic Plain to the Bay of Bengal during the winter and early spring of each year. The persistent winter fog in the region is already a cause of much concern, and several studies have been proposed to understand the economic, scientific, and societal dimensions of this problem. During the INDian Ocean EXperiment (INDOEX) field studies, aerosols from this region were shown to affect cloud formation and monsoon activity over the Indian Ocean. This is one of the few regions showing a trend toward increasing surface dimming and enhanced mid-tropospheric warming. Increasing air pollution over this region could modify the radiative balance through direct, indirect, and semi-indirect effects associated with aerosols. The consequences of aerosols and associated pollution for surface insolation over the Ganges Valley and monsoons, in particular, are not well understood. The proposed field study is designed for use of (1) the ARM Mobile Facility (AMF) to measure relevant radiative, cloud, convection, and aerosol optical characteristics over mainland India during an extended period of 9–12 months and (2) the G-1 aircraft and surface sites to measure relevant aerosol chemical, physical, and optical characteristics in the Ganges Valley during a period of 6–12 weeks. The aerosols in this region have complex sources, including burning of coal, biomass, and biofuels; automobile

  8. Significant atmospheric aerosol pollution caused by world food cultivation

    Science.gov (United States)

    Bauer, Susanne E.; Tsigaridis, Kostas; Miller, Ron

    2016-05-01

    Particulate matter is a major concern for public health, causing cancer and cardiopulmonary mortality. Therefore, governments in most industrialized countries monitor and set limits for particulate matter. To assist policy makers, it is important to connect the chemical composition and severity of particulate pollution to its sources. Here we show how agricultural practices, livestock production, and the use of nitrogen fertilizers impact near-surface air quality. In many densely populated areas, aerosols formed from gases that are released by fertilizer application and animal husbandry dominate over the combined contributions from all other anthropogenic pollution. Here we test reduction scenarios of combustion-based and agricultural emissions that could lower air pollution. For a future scenario, we find opposite trends, decreasing nitrate aerosol formation near the surface while total tropospheric loads increase. This suggests that food production could be increased to match the growing global population without sacrificing air quality if combustion emission is decreased.

  9. Decoration of vertical graphene with aerosol nanoparticles for gas sensing

    Science.gov (United States)

    Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

    2015-08-01

    A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

  10. Significant Atmospheric Aerosol Pollution Caused by World Food Cultivation

    Science.gov (United States)

    Bauer, Susanne E.; Tsigaridis, Kostas; Miller, Ron

    2016-01-01

    Particulate matter is a major concern for public health, causing cancer and cardiopulmonary mortality. Therefore, governments in most industrialized countries monitor and set limits for particulate matter. To assist policy makers, it is important to connect the chemical composition and severity of particulate pollution to its sources. Here we show how agricultural practices, livestock production, and the use of nitrogen fertilizers impact near-surface air quality. In many densely populated areas, aerosols formed from gases that are released by fertilizer application and animal husbandry dominate over the combined contributions from all other anthropogenic pollution. Here we test reduction scenarios of combustion-based and agricultural emissions that could lower air pollution. For a future scenario, we find opposite trends, decreasing nitrate aerosol formation near the surface while total tropospheric loads increase. This suggests that food production could be increased to match the growing global population without sacrificing air quality if combustion emission is decreased.

  11. [Remediation efficiency of lead-contaminated soil at an industrial site by ultrasonic-assisted chemical extraction].

    Science.gov (United States)

    Wang, Xin-jie; Huang, Jin-lou; Liu, Zhi-qiang; Yue, Xi

    2013-09-01

    This research chose five lead-contaminated sites of a lead-acid battery factory to analyze the speciation distribution and concentration of lead. Under the same conditions (0.1 mol x L(-1) EDTA,30 min, 25 degrees C), the removal effect of heavy metal was compared between ultrasonic-assisted chemical extraction (UCE) and conventional chemical extraction ( CCE), and the variation of lead speciation was further explored. The results showed that the lead removal efficiency of UCE was significantly better than CCE. The lead removal efficiency of WS, A, B, C and BZ was 10.06%, 48.29%, 48.69%, 53.28% and 36.26% under CCE. While the removal efficiency of the UCE was 22.42%, 69.31%, 71.00%, 74.49% and 71.58%, with the average efficiency higher by 22%. By comparing the speciation distribution of the two washing methods, it was found that the acid extractable content maintained or decreased after UCE, whereas it showed an increasing trend after CCE. The reduction effect of the reducible was as high as 98% by UCE. UCE also showed a more efficient reduction effect of the organic matter-sulfite bounded form and the residual form. Hence, it is feasible to improve the washing efficiency of heavy metal contained in soil by conducting the cleaning process with the help of ultrasonic wave, which is a simple and fast mean to remove lead from contaminated sites.

  12. Nuclear Magnetic Resonance-Assisted Prediction of Secondary Structure for RNA: Incorporation of Direction-Dependent Chemical Shift Constraints.

    Science.gov (United States)

    Chen, Jonathan L; Bellaousov, Stanislav; Tubbs, Jason D; Kennedy, Scott D; Lopez, Michael J; Mathews, David H; Turner, Douglas H

    2015-11-17

    Knowledge of RNA structure is necessary to determine structure-function relationships and to facilitate design of potential therapeutics. RNA secondary structure prediction can be improved by applying constraints from nuclear magnetic resonance (NMR) experiments to a dynamic programming algorithm. Imino proton walks from NOESY spectra reveal double-stranded regions. Chemical shifts of protons in GH1, UH3, and UH5 of GU pairs, UH3, UH5, and AH2 of AU pairs, and GH1 of GC pairs were analyzed to identify constraints for the 5' to 3' directionality of base pairs in helices. The 5' to 3' directionality constraints were incorporated into an NMR-assisted prediction of secondary structure (NAPSS-CS) program. When it was tested on 18 structures, including nine pseudoknots, the sensitivity and positive predictive value were improved relative to those of three unrestrained programs. The prediction accuracy for the pseudoknots improved the most. The program also facilitates assignment of chemical shifts to individual nucleotides, a necessary step for determining three-dimensional structure.

  13. Near-infrared absorptance enhancement and device application of nanostructured black silicon fabricated by metal-assist chemical etching

    Science.gov (United States)

    Huang, Lieyun; Zhong, Hao; Liao, Naiman; Long, Fei; Guo, Guohui; Li, Wei

    2016-11-01

    We use metal-assist chemical etching (MCE) method to fabricate nanostructured black silicon on the surface of C-Si. In our MCE process, a chemical reduction reaction of silver cation (Ag+) will happen on the surface of silicon substrate, and at the same time the silicon atoms around Ag particles are oxidized and dissolved, generating nanopores and finally forming a layer called black silicon on the top of the substrates. The nanopores have diameter and depth of about 400 nm and 2 μm, respectively. Furthermore, these modified surfaces show higher light absorptance in near-infrared range (800 to 2500 nm) compared to that of C-Si with polished surfaces, and the maximum light absorptance increases significantly up to 95% in the wavelength region of 400 to 2500 nm. The Si-PIN photoelectronic detector based on this type of black silicon, in which the black silicon layer is directly set as the photosensitive surface, has a substantial increase in responsivity with about 80 nm red shift of peak responsivity, particularly at near-infrared wavelengths, rising to 0.57 A/W at 1060 nm and 0.37 A/W at 1100 nm, respectively. Our recent novel results clearly indicate that nanostructured black silicon made by MCE has a potential application in near-infrared photoelectronic detectors.

  14. Preparation, characterisation and optimisation of lithium battery anodes consisting of silicon synthesised using Laser assisted Chemical Vapour Pyrolysis

    Science.gov (United States)

    Veliscek, Ziga; Perse, Lidija Slemenik; Dominko, Robert; Kelder, Erik; Gaberscek, Miran

    2015-01-01

    Suitability of silicon prepared using Laser assisted Chemical Vapour Pyrolysis (LaCVP) as a potential anode material in lithium batteries is systematically investigated. Its compositional, morphological, physical-chemical and electrochemical properties are compared to a current benchmark commercial silicon. Important differences in particle size and particle composition are found which, as shown, affect critically the rheological properties of the corresponding electrode slurries. In order to overcome the rheological problems of prepared nanosilicon, we introduce and optimise a spraying method instead of using the usual casting technique for slurry application. Interestingly, the optimised electrodes show similar electrochemical performance, regardless of the particle size or composition of nanosilicon. This unexpected result is explained by the unusually high resistance of electrochemical wiring in silicon-based electrodes (about 60 Ohm per 1 mg cm-2 of active material loading). Despite that, the optimised material still shows a capacity up to 1200 mA h g-1 at a relatively high loading of 1.6 mg cm-2 and after 20 cycles. On the other hand, by decreasing the loading to below ca. 0.9 mg cm-2 the wiring problems are effectively overcome and capacities close to theoretical values can be obtained.

  15. Tuning the Electrical Properties of Graphene via Nitrogen Plasma-Assisted Chemical Modification.

    Science.gov (United States)

    Jung, Min Wook; Song, Wooseok; Jung, Dae Sung; Lee, Sun Sook; Park, Chong-Yun; An, Ki-Seok

    2016-03-01

    The control in electrical properties of graphene is essentially required in order to realize graphenebased nanoelectronics. In this study, N-doped graphene was successfully obtained via nitrogen plasma treatment. Graphene was synthesized on copper foil using thermal chemical vapor deposition. After N2 plasma treatment, the G-band of the graphene was blueshifted and the intensity ratio of 2D- to G-bands decreased with increasing the plasma power. Pyrrolic-N bonding configuration induced by N2 plasma treatment was studied by X-ray photoelectron spectroscopy. Remarkably, electrical characterization including Hall measurement and I-V characteristics of the N-doped graphene exhibit semiconducting behavior as well as the n-type doping effect.

  16. Multi-wavelength Raman lidar, sun photometric and aircraft measurements in combination with inversion models for the estimation of the aerosol optical and physico-chemical properties over Athens, Greece

    Science.gov (United States)

    Mamouri, R. E.; Papayannis, A.; Amiridis, V.; Müller, D.; Kokkalis, P.; Rapsomanikis, S.; Karageorgos, E. T.; Tsaknakis, G.; Nenes, A.; Kazadzis, S.; Remoundaki, E.

    2012-07-01

    A novel procedure has been developed to retrieve, simultaneously, the optical, microphysical and chemical properties of tropospheric aerosols with a multi-wavelength Raman lidar system in the troposphere over an urban site (Athens, Greece: 37.9° N, 23.6° E, 200 m a.s.l.) using data obtained during the European Space Agency (ESA) THERMOPOLIS project, which took place between 15-31 July 2009 over the Greater Athens Area (GAA). We selected to apply our procedure for a case study of intense aerosol layers that occurred on 20-21 July 2009. The National Technical University of Athens (NTUA) EOLE 6-wavelength Raman lidar system has been used to provide the vertical profiles of the optical properties of aerosols (extinction and backscatter coefficients, lidar ratio) and the water vapor mixing ratio. An inversion algorithm was used to derive the mean aerosol microphysical properties (mean effective radius (reff), single-scattering albedo ω) and mean complex refractive index (m)) at selected heights in the 2-3 km height region. We found that reff was 0.14-0.4 (±0.14) μm, ω was 0.63-0.88 (±0.08) (at 532 nm) and m ranged from 1.44 (±0.10) + 0.01 (±0.01)i to 1.55 (±0.12) + 0.06 (±0.02)i, in good agreement (only for the reff values) with in situ aircraft measurements. The water vapor and temperature profiles were incorporated into the ISORROPIA II model to propose a possible in situ aerosol composition consistent with the retrieved m and ω values. The retrieved aerosol chemical composition in the 2-3 km height region gave a variable range of sulfate (0-60%) and organic carbon (OC) content (0-50%), although the OC content increased (up to 50%) and the sulfate content dropped (up to 30%) around 3 km height; the retrieved low ω value (0.63), indicates the presence of absorbing biomass burning smoke mixed with urban haze. Finally, the retrieved aerosol microphysical properties were compared with column-integrated sun photometer CIMEL data.

  17. Evaluation of chemical transport model predictions of primary organic aerosol for air masses classified by particle component-based factor analysis

    Directory of Open Access Journals (Sweden)

    C. A. Stroud

    2012-09-01

    Full Text Available Observations from the 2007 Border Air Quality and Meteorology Study (BAQS-Met 2007 in Southern Ontario, Canada, were used to evaluate predictions of primary organic aerosol (POA and two other carbonaceous species, black carbon (BC and carbon monoxide (CO, made for this summertime period by Environment Canada's AURAMS regional chemical transport model. Particle component-based factor analysis was applied to aerosol mass spectrometer measurements made at one urban site (Windsor, ON and two rural sites (Harrow and Bear Creek, ON to derive hydrocarbon-like organic aerosol (HOA factors. A novel diagnostic model evaluation was performed by investigating model POA bias as a function of HOA mass concentration and indicator ratios (e.g. BC/HOA. Eight case studies were selected based on factor