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Sample records for hg dry deposition

  1. Litterfall mercury dry deposition in the eastern USA

    Science.gov (United States)

    Martin R. Risch; John F. DeWild; David P. Krabbenhoft; Randall K. Kolka; Leiming. Zhang

    2012-01-01

    Mercury (Hg) in autumn litterfall frompredominately deciduous forestswas measured in 3 years of samples from 23 Mercury Deposition Network sites in 15 states across the eastern USA. Annual litterfall Hg dry depositionwas significantly higher (median 12.3 micrograms per square meter (µg/m2), range 3.5-23.4 µg/m2...

  2. SO2/Hg removal from flue gas by dry FGD

    Institute of Scientific and Technical Information of China (English)

    Wang Fan; Wang Hongmei; Zhang Fan; Zhu Jinwei; Tian Gang; Liu Yu; Mao Jixian

    2012-01-01

    To study the mechanism of SO2 and Hg removal from flue gas,an experimental packed bed reactor was designed to simulate the dry FGD,where a mixture of lime and fly ash in ratio 1∶3 w/w was used as the SO2 and Hg sorbent,and steam at temperature of 100 ℃ was applied for activation of the sorbent,while the activation time set to 20 min.The experimental factors including the SO2/Hg sorbent characteristics,50% breakthrough time for SO2/Hg removal,sorbent packed bed depth and reaction temperature were investigated.The experimental results show that after steam activation,the BET specific surface area and specific pore volume increased from 37.8 to 45.5 m2/g and from 0.42 to 0.51 cm3/g,respectively.With activation of the sorbent by steam,the 50% breakthrough times of SO2 and Hg removal increased from 34 to 42 min and from 23 to 45 min,respectively.When the packed bed depth was increased from 5 to 25 mm,the 50% breakthrough times for Hg and SO2 removal increased from 12 to 52 min and from 6 to 47 min,respectively.With the increase of the reaction temperature,the 50% breakthrough of SO2/Hg removal decreased accordingly.Steam activation can efficiently improve SO2/Hg removal simultaneously.

  3. Bioindication of volcanic mercury (Hg) deposition around Mt Etna (Sicily)

    Science.gov (United States)

    Martin, R.; Witt, M. L.; Sawyer, G. M.; Watt, S.; Bagnato, E.; Calabrese, S.; Aiuppa, A.; Delmelle, P.; Pyle, D. M.; Mather, T. A.

    2012-12-01

    Mt. Etna is a major natural source of Hg to the Mediterranean region. Total mercury concentrations, [Hg]tot, in Castanea sativa (sweet chestnut) leaves sampled 7-13 km from Etna's vents (during six campaigns in 2005-2011) were determined using atomic absorption spectroscopy. [Hg]tot in C. sativa was greatest on Etna's SE flank reflecting Hg deposition from the typically overhead volcanic plume. When adjusted for leaf age, [Hg]tot in C. sativa also increased with recent eruptive activity. [Hg]tot in C. sativa was not controlled by [Hg]tot in soils, which instead was greatest on the (upwind) NW flank and correlated strongly with soil organic matter (% Org). Our results suggest that at least ~1% of Hg emitted from Etna is deposited proximally, supporting recent measurement and model results which indicate that GEM (Hg0; the dominant form of Hg in high temperature magmatic gases) is oxidised rapidly to RGM and Hgp in ambient temperature volcanic plumes. Samples of C. sativa and soils were also collected in July and September 2012 alongside SO2 and acid gas diffusion tube samples. These new samples will enable us to investigate Hg accumulation over a single growth season with reference to the exposure of vegetation to volcanic gases and particles.

  4. The estimated six-year mercury dry deposition across North America

    Science.gov (United States)

    Zhang, Leiming; Wu, Zhiyong; Cheng, Irene; Wright, L. Paige; Olson, Mark L.; Gay, David A.; Risch, Martin R.; Brooks, Steven; Castro, Mark S.; Conley, Gary D.; Edgerton, Eric S.; Holsen, Thomas M.; Luke, Winston; Tordon, Robert; Weiss-Penzias, Peter

    2016-01-01

    Dry deposition of atmospheric mercury (Hg) to various land covers surrounding 24 sites in North America was estimated for the years 2009 to 2014. Depending on location, multiyear mean annual Hg dry deposition was estimated to range from 5.1 to 23.8 μg m–2 yr–1 to forested canopies, 2.6 to 20.8 μg m–2 yr–1 to nonforest vegetated canopies, 2.4 to 11.2 μg m–2 yr–1 to urban and built up land covers, and 1.0 to 3.2 μg m–2 yr–1 to water surfaces. In the rural or remote environment in North America, annual Hg dry deposition to vegetated surfaces is dominated by leaf uptake of gaseous elemental mercury (GEM), contrary to what was commonly assumed in earlier studies which frequently omitted GEM dry deposition as an important process. Dry deposition exceeded wet deposition by a large margin in all of the seasons except in the summer at the majority of the sites. GEM dry deposition over vegetated surfaces will not decrease at the same pace, and sometimes may even increase with decreasing anthropogenic emissions, suggesting that Hg emission reductions should be a long-term policy sustained by global cooperation.

  5. Investigating sources of gaseous oxidized mercury in dry deposition at three sites across Florida, USA

    Directory of Open Access Journals (Sweden)

    M. Sexauer Gustin

    2012-07-01

    Full Text Available During 2009–2010, the State of Florida established a series of air quality monitoring stations to collect data for development of a statewide total maximum daily load (TMDL for mercury (Hg. At three of these sites, located near Ft. Lauderdale (DVE, Pensacola (OLF, and Tampa Bay (TPA, passive samplers for the measurement of air Hg concentrations and surrogate surfaces for measurement of Hg dry deposition were deployed. While it is known that Hg in wet deposition in Florida is high compared to the rest of the United States, there is little information on Hg dry deposition. The objectives of the work were to: (1 investigate the utility of passive sampling systems for Hg in an area with low and consistent air concentrations as measured by the Tekran® mercury measurement system, (2 estimate dry deposition of gaseous oxidized Hg, and (3 investigate potential sources. This paper focuses on Objective 3. All sites were situated within 15 km of 1000 MW electricity generating plants (EGPs and major highways. Bi-weekly dry deposition and passive sampler Hg uptake were not directly correlated with the automated Tekran® system measurements, and there was limited agreement between these systems for periods of high deposition. Using diel, biweekly, and seasonal Hg observations, and ancillary data collected at each site, the potential sources of Hg deposited to surrogate surfaces were investigated. With this information, we conclude that there are three major processes/sources contributing to Hg dry deposition in Florida, with these varying as a function of location and time of year. These include: (1 in situ oxidation of locally and regionally derived Hg facilitated by mobile source emissions, (2 indirect and direct inputs of Hg from local EGPs, and (3 direct input of Hg associated with long range transport of air from the Northeastern United States. We also suggest based on the data collected with the Tekran® and passive sampling systems that different

  6. Atmospheric total gaseous mercury (TGM concentrations and wet and dry deposition of mercury at a high-altitude mountain peak in south China

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    H. Zhang

    2009-11-01

    Full Text Available China is regarded as the largest contributor of mercury (Hg to the global atmospheric Hg budget. However, concentration levels and depositions of atmospheric Hg in China are poorly known. Continuous measurements of atmospheric total gaseous mercury (TGM were carried out from May 2008 to May 2009 at the summit of Mt. Leigong in south China. Wet and dry deposition fluxes of Hg were also calculated following collection of precipitation, throughfall and litterfall. Atmospheric TGM concentrations averaged 2.80±1.51 ng m−3, which was highly elevated compared to global background values but much lower than semi-rural and industrial/urban areas in China, indicating great emissions of Hg in central, south and southwest China. Seasonal and diurnal variations of TGM were observed, which reflected variations in source intensity, deposition processes and meteorological factors. Wet deposition of Hg was quite low, while its dry deposition of Hg (litterfall + throughfall-direct wet deposition constituted a major portion of total deposition (~88% for total mercury (THg and 84% for methyl mercury (MeHg. This highlights the importance of vegetation to Hg atmospheric cycling. In a remote forest ecosystem of China, dry deposition of TGM, especially gaseous elemental mercury (GEM, was very important for the depletion of atmospheric Hg. Elevated TGM level in ambient air may accelerate the foliar uptake of Hg through air which may partly explain the elevated Hg dry deposition fluxes observed in Mt. Leigong.

  7. DRY DEPOSITION OF POLLUTANTS TO FORESTS

    Science.gov (United States)

    We report on the results of an extensive field campaign to measure dry deposition of ozone and sulfur dioxide to a sample of forest types in the United States. Measurements were made for full growing seasons over a deciduous forest in Pennsylvania and a mixed deciduous-conifer...

  8. Formation of PdHg by reaction of palladium thin film contacts deposited onto mercuric iodide ({alpha}-HgI{sub 2}) radiation detector crystals

    Energy Technology Data Exchange (ETDEWEB)

    Medlin, D.L. [Sandia National Labs., Livermore, CA (United States); Van Scyoc, J.M. [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Electrical and Computer Engineering; Gilbert, T.S. [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Electrical and Computer Engineering; Schlesinger, T.E. [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Electrical and Computer Engineering; Boehme, D. [Sandia National Labs., Livermore, CA (United States); Schieber, M. [Sandia National Labs., Livermore, CA (United States); Natarajan, M. [TN Technologies, Inc., Round Rock, TX (United States); James, R.B. [Sandia National Labs., Livermore, CA (United States)

    1996-10-01

    The microstructure and phase distribution of palladium thin films sputter deposited onto {alpha}-HgI{sub 2} for use as electrical contacts in radiation detectors are investigated using electron microscopy. Our results show a limited reaction to form palladium mercuride (PdHg). It is shown that the formation of PdHg via several reaction pathways is thermodynamically feasible. (orig.).

  9. On the dry deposition of submicron particles

    Energy Technology Data Exchange (ETDEWEB)

    Wesely, M. L.

    1999-10-08

    The air-surface exchange of particles can have a strong role in determining the amount, size, and chemical composition of particles in the troposphere. Here the authors consider only dry processes (deposition processes not directly aided by precipitation) and mostly address particles less than about 2 {micro}m in diameter (often referred to as submicron particles because most of such particles are less than 1 {micro}m in diameter). The processes that control the dry exchange of particulate material between the atmosphere and the surface of the Earth are numerous, highly varied, and sometimes poorly understood. As a result, determining which of the surface processes to parameterize or simulate in modeling the tropospheric mass budget of a particulate substance can be a significant challenge. Dry deposition, for example, can be controlled by a combination of Brownian diffusion, impaction, interception, and gravitational settling, depending on the size of the particles, the roughness of the surface on both micrometeorological and microscopic scales, the geometrical structure of vegetative canopies, and other surface characteristics such as wetness. Particles can be added to the lower atmosphere by resuspension from land surfaces and sea spray. The roles of rapid gas-to-particle conversion and growth or shrinkage of particles as a result of water condensation or evaporation in the lower few meters of the atmosphere can also have a significant impact on particle concentrations in the lower atmosphere. Here, a few micrometeorological observations and inferences on particle air-surface exchange are briefly addressed.

  10. Mercury in stream water at five Czech catchments across a Hg and S deposition gradient

    Science.gov (United States)

    Navrátil, Tomáš; Shanley, James B.; Rohovec, Jan; Oulehle, Filip; Krám, Pavel; Matoušková, Šárka; Tesař, Miroslav; Hojdová, Maria

    2015-01-01

    The Czech Republic was heavily industrialized in the second half of the 20th century but the associated emissions of Hg and S from coal burning were significantly reduced since the 1990s. We studied dissolved (filtered) stream water mercury (Hg) and dissolved organic carbon (DOC) concentrations at five catchments with contrasting Hg and S deposition histories in the Bohemian part of the Czech Republic. The median filtered Hg concentrations of stream water samples collected in hydrological years 2012 and 2013 from the five sites varied by an order of magnitude from 1.3 to 18.0 ng L− 1. The Hg concentrations at individual catchments were strongly correlated with DOC concentrations r from 0.64 to 0.93 and with discharge r from 0.48 to 0.75. Annual export fluxes of filtered Hg from individual catchments ranged from 0.11 to 13.3 μg m− 2 yr− 1 and were highest at sites with the highest DOC export fluxes. However, the amount of Hg exported per unit DOC varied widely; the mean Hg/DOC ratio in stream water at the individual sites ranged from 0.28 to 0.90 ng mg− 1. The highest stream Hg/DOC ratios occurred at sites Pluhův Bor and Jezeří which both are in the heavily polluted Black Triangle area. Stream Hg/DOC was inversely related to mineral and total soil pool Hg/C across the five sites. We explain this pattern by greater soil Hg retention due to inhibition of soil organic matter decomposition at the sites with low stream Hg/DOC and/or by precipitation of a metacinnabar (HgS) phase. Thus mobilization of Hg into streams from forest soils likely depends on combined effects of organic matter decomposition dynamics and HgS-like phase precipitation, which were both affected by Hg and S deposition histories.

  11. Comparison of Mercury Mass Loading in Streams to Wet and Dry Atmospheric Deposition in Watersheds of the Western US: Evidence for Non-Atmospheric Mercury Sources

    Science.gov (United States)

    Domagalski, J. L.; Majewski, M. S.; Alpers, C. N.; Eckley, C.

    2015-12-01

    Many streams in the western United States (US) are listed as impaired by mercury (Hg), and it is important to understand the magnitudes of the various sources in order to implement management strategies. Atmospheric deposition of Hg and can be a major source of aquatic contamination, along with mine wastes, and other sources. Prior studies in the eastern US have shown that streams deliver less than 50% of the atmospherically deposited Hg on an annual basis. In this study, we compared annual stream Hg loads for 20 watersheds in the western US to measured wet and modeled dry deposition. Land use varies from undisturbed to mixed (agricultural, urban, forested, mining). Data from the Mercury Deposition Network was used to estimate Hg input from precipitation. Dry deposition was not directly measured, but can be modeled using the Community Multi-scale Air Quality model. At an undeveloped watershed in the Rocky Mountains, the ratio of stream Hg load to atmospheric deposition was 0.2 during a year of average precipitation. In contrast, at the Carson River in Nevada, with known Hg contamination from historical silver mining with Hg amalgamation, stream export exceeded atmospheric deposition by a factor of 60, and at a small Sierran watershed with gold mining, the ratio was 70. Larger watersheds with mixed land uses, tend to have lower ratios of stream export relative to atmospheric deposition suggesting storage of Hg. The Sacramento River was the largest watershed for which Hg riverine loads were available with an average ratio of stream Hg export to atmospheric deposition of 0.10. Although Hg was used in upstream historical mining operations, the downstream river Hg load is partially mitigated by reservoirs, which trap sediment. This study represents the first compilation of riverine Hg loads in comparison to atmospheric deposition on a regional scale; the approach may be useful in assessing the relative importance of atmospheric and non-atmospheric Hg sources.

  12. An Artificial Turf-Based Surrogate Surface Collector for the Direct Measurement of Atmospheric Mercury Dry Deposition

    Science.gov (United States)

    This paper describes the development of a new artificial turf surrogate surface (ATSS) sampler for use in the measurement of mercury (Hg) dry deposition. In contrast to many existing surrogate surface designs, the ATSS utilizes a three-dimensional deposition surface that may more...

  13. Mass Dependent Fractionation of Hg Isotopes in Source Rocks, Mineral Deposits and Spring Waters of the California Coast Ranges, USA

    Science.gov (United States)

    Smith, C. N.; Kesler, S. E.; Blum, J. D.; Rytuba, J. J.

    2007-12-01

    We present here the first study of the isotopic composition of Hg in rocks, ore deposits, and active hydrothermal systems from the California Coast Ranges, one of Earth's largest Hg-depositing systems. The Franciscan Complex and Great Valley Sequence, which form the bedrock in the California Coast Ranges, are intruded and overlain by Tertiary volcanic rocks including the Clear Lake Volcanic Sequence. These rocks contain two types of Hg deposits, hot-spring deposits that form at shallow depths (geothermal systems that release Hg to the present surface. The Franciscan Complex and Great Valley Sequence contain clastic sedimentary rocks with higher concentrations of Hg than volcanic rocks of the Clear Lake Volcanic Field. Mean Hg isotope compositions for all three rock units are similar, although the range of values in Franciscan Complex rocks is greater than in either Great Valley or Clear Lake rocks. Hot spring and silica-carbonate Hg deposits have similar average isotopic compositions that are indistinguishable from averages for the three rock units, although δ202Hg values for the Hg deposits have a greater variance than the country rocks. Precipitates from dilute spring and saline thermal waters in the area have similarly large variance and a mean δ202Hg value that is significantly lower than the ore deposits and rocks. These observations indicate there is little or no isotopic fractionation during release of Hg from its source rocks into hydrothermal solutions. Isotopic fractionation does appear to take place during transport and concentration of Hg in deposits, especially in their uppermost parts. Boiling of hydrothermal fluids is likely the most important process causing of the observed Hg isotope fractionation. This should result in the release of Hg with low δ202Hg values into the atmosphere from the top of these hydrothermal systems and a consequent enrichment in heavy Hg isotopes in the upper crust through time.

  14. Dry deposition of sulfur to forests in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Akira; Sato, Kazuo; Fujita, Shin-ichi [Central Research Institute of Electric Power Industry, Tokyo (Japan)

    1996-12-31

    Dry deposition is an important input process of acidifying compounds to forest ecosystem. However, dry deposition to forest was largely unstudied in Japan, despite the fact that about 70% of the land is covered with forest. To assess the contribution of dry deposition to the total (wet + dry) input of sulfur to forest, we estimated dry deposition velocities and fluxes of sulfur to three different forest stands (cedar [Cryptomeria japonica], pine [Pinus densiflora], and oak [Quercus serrata]) located at Mt. Akagi in Gumma Prefecture, Japan. Micro meteorology above canopies, atmospheric concentrations, and throughfall fluxes were measured from October 1994 to September 1995. Deposition velocities of sulfur dioxide and particulate sulfate were determined by using the inferential method, based on the result of meteorological measurements. Dry deposition fluxes were calculated from the estimated deposition velocities and the result of concentration measurements. Dry deposition fluxes of sulfate for cedar, pine, and oak were estimated at 164 eq/ha/y, 143 eq/ha/y, and 131 eq/ha/y, respectively. The relative contribution of dry deposition ranged from 20% to 22% of the total sulfur deposition. However, these results might be underestimated because estimated fluxes were about 30% lower than observed net throughfall fluxes ([throughfall + stemflow] - precipitation) in cedar and pine forest stands.

  15. Anisotropic silver nanoparticles deposited on zeolite a for selective Hg2+ colorimetric sensing and antibacterial studies

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    Khorshidi Alireza

    2015-01-01

    Full Text Available Silver nanoparticles deposited on the surface of zeolite A were prepared via post ion-exchange reduction, and reduction-deposition methods. Formation of the silver nanoparticles on the surface of zeolite A was verified by surface plasmon spectra using diffuse reflectance spectroscopy and ultraviolet-visible spectroscopy. Morphology of the prepared samples was characterized by X-ray diffraction and scanning electron microscopy. Furthermore, silver nanoparticles deposited on the zeolite A, after fixation of Rhodamine B dye molecules over themselves, were successful in detecting Hg2+ ions selectively. After treatment with the so-obtained sensor, color change from colorless to pink was visible to the naked eye for the Hg2+ solution concentrations down to 1.0×10-8 mol.L-1. Antibacterial tests demonstrated the multifunctional application of the silver nanoparticles deposited on zeolite A.

  16. Simulated dry deposition of nitric acid near forest edges

    NARCIS (Netherlands)

    DeJong, JJM; Klaassen, W; Jong, J.J.M. de

    1997-01-01

    Dry deposition is simulated to understand and generalize observations of enhanced deposition of air pollution near forest edges. Nitric acid is taken as an example as its deposition velocity is often assumed to be determined by turbulent transport only. The simulations are based on the micro-meteoro

  17. The Kongsberg silver deposits, Norway: Ag-Hg-Sb mineralization and constraints for the formation of the deposits

    Science.gov (United States)

    Kotková, Jana; Kullerud, Kåre; Šrein, Vladimír; Drábek, Milan; Škoda, Radek

    2017-07-01

    The Kongsberg silver district has been investigated by microscopy and electron microprobe analysis, focusing primarily on the Ag-Hg-Sb mineralization within the context of the updated mineral paragenesis. The earliest mineralization stage is represented by sulfides, including acanthite, and sulfosalts. Native silver formed initially through breakdown of early Ag-bearing phases and later through influx of additional Ag-bearing fluids and silver remobilization. The first two generations of native silver were separated in time by the formation of Ni-Co-Fe sulfarsenides and the monoarsenide niccolite along rims of silver crystals. The presence of As-free sulfosalts and the absence of di- and tri-arsenides suggest a lower arsenic/sulfur activity ratio for the Kongsberg deposits compared to other five-element deposits. Native silver shows binary Ag-Hg and Ag-Sb solid solutions, in contrast to the ternary Ag-Hg-Sb compositions typical for other deposits of similar type. Antimonial silver together with allargentum, dyscrasite, and pyrargyrite was documented exclusively from the northern area of the district. Elsewhere, the only Sb-bearing minerals are polybasite and tetrahedrite/freibergite. Hg-rich silver (up to 21 wt% Hg) has been documented only in the central-western area. Myrmekite of freibergite and chalcopyrite reflects exsolution from an original Ag-poor tetrahedrite upon cooling, while myrmekite of pyrite and silver, forming through breakdown of low-temperature phases (argentopyrite or lenaite) upon heating, characterizes the Kongsberg silver district. Based on the stabilities of minerals and mineral assemblages, the formation of the silver mineralization can be constrained to temperatures between 180 and 250 °C.

  18. Sulfate dry deposition to red oak and tulip poplar leaves

    Energy Technology Data Exchange (ETDEWEB)

    Vandenberg, J.J. (US Environmental Protection Agency Research Triangle Park, NC (USA)); Knoerr, K.R. (Duke Univ Durham, NC (USA))

    1988-01-01

    Measurement of rates of atmospheric sulfate dry deposition to vegetation is necessary to assess biophysical relationships. However, micrometeorological measurement techniques have stringent site and equipment requirements and direct estimation techniques have procedural and contamination difficulties. This paper describes the development and testing of a leaf washing technique to directly measure the rate of sulfate dry deposition to hardwood forest vegetation. The leaf washing technique was developed by comparing the rate of removal of sulfur dry deposited to leaf surfaces with the rate and extent of leaching from the internal sulfur pool.

  19. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  20. MEASUREMENT AND MODELING OF THE DRY DEPOSITION OF PEROXIDES

    Science.gov (United States)

    Measurements of the dry deposition velocity (Vd) of hydrogen peroxide (H2O2) and total organic peroxides (ROOH) were made during four experiments at three forested sites. Details and uncertainties associated with the measurement of peroxide...

  1. RF magnetron sputtering deposition of CdTe passivation on HgCdTe

    Science.gov (United States)

    Rutkowski, Jaroslaw; Adamiec, Krzysztof; Rogalski, Antoni

    1998-04-01

    In this study, we report the RF magnetron sputtering growth and characterization of CdTe passivant on bulk n-type HgCdTe. Our investigations include the HgCdTe surface preparation and in-situ pretreatment, deposition-induced surface damage, interface charge, CdTe film stoichiometry, and thermal stability. The metal-insulator-semiconductor test structures are processed and their electrical properties are measured by capacitance-voltage characteristics. The heterostructures are also characterized by reflectance measurement. In order to investigate the passivation properties of CdTe/HgCdTe heterostructures, we have modeled the band diagram of abrupt CdTe/HgCdTe heterojunction. The effect of sputtering growth condition parameters is also reported. The sputtering CdTe layers, exhibit excellent dielectric, insulating and mechano- chemical properties, as well as interface properties. The interfaces are characterized by slight accumulation and a small hysteresis. A carefully controlled growth process and surface pretreatment tailored to the specific material are required in order to obtain near flat band conditions on n- type materials. Additional informations on surface limitations are obtained from analyzing the I-V characteristics of photodiodes with metal gates covering the p-n junction surface location.

  2. Dry deposition modelling of air pollutants over urban areas

    Science.gov (United States)

    Cherin, N.; Roustan, Y.; Seigneur, C.; Musson Genon, L.

    2012-04-01

    More than one-half of the world's inhabitants lives in urban areas. Consequently, the evolution of pollutants inside these urban areas are problems of great concern in air quality studies. Though the dry deposition fluxes of air pollutants, which are known to be significant in the neighborhood of sources of pollution, like urban areas, have not been modeled precisely until recently within urban areas. By reviewing the physics of the processes leading to the dry deposition of air pollutants, it is clear that atmosphere turbulence is crucial for dry deposition. Urban areas, and particularly buildings, are known to significantly impact flow fields and then by extension the dry deposition fluxes. Numerous urban schemes have been developed in the past decades to approximate the effect of the local scale urban elements on drag, heat flux and radiative budget. The most recent urban canopy models are based on quite simple geometries, but sufficiently close to represent the aerodynamic and thermal characteristics of cities. These canopy models are generally intended to parameterize aerodynamic and thermal fields, but not dry deposition. For dry deposition, the current classical "roughness" approach, uses only two representative parameters, z0 and d, namely the roughness length and the zero-plane displacement height to represent urban areas. In this work, an innovative dry deposition model based on the urban canyon concept, is proposed. It considers a single road, bordered by two facing buildings, which are treated separately. It accounts for sub-grid effects of cities, especially a better parameterization of the turbulence scheme, through the use of local mixing length and a more detailled description of the urban area and key parameters within the urban canopy. Three different flow regimes are distinguished in the urban canyon according to the height-to-width ratio: isolated roughness flow, wake interference flow and skimming flow regime. The magnitude of differences in

  3. Dry Deposition from Sahara Sources Regions of Western Africa

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    B. Douaiba

    2014-01-01

    Full Text Available Sahara dust storms during March 2004 have attracted much attention from the dust-research community due to their intensity, wide coverage, and endurance. In the present work, the dry deposition mechanisms of mineral dust are analysed during an event on the 3 March 2004 over the Northwest African coast. This particular case was chosen based on the strong dry removal that occurred, rendering it ideal for examining the deposition processes. The simulation of synoptic conditions and dry deposition of four dust particles including clay, small silt, large silt, and sand was performed with Eta model, coupled with a desert dust cycle module. The results have been compared with surface data from weather stations in North Africa, data of dry metals from stations located in Gran Canaria, and various satellite images such as European Organization for the Exploitation of Meteorological Satellites and Moderate Resolution Imaging Spectroradiometer for the period in question.

  4. Observations of atmospheric Hg species and depositions in remote areas of China

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    Feng X.

    2013-04-01

    Full Text Available From September 2007, we conducted continuous measurements of speciated atmospheric mercury (Hg and atmospheric mercury depositions at five remote sites in China. Four of these sites were involved in the Global Mercury Observation System (GMOS as ground-based stations. These stations were located in the northwest, southwest, northeast, and east part of China, respectively, which represent the regional atmospheric Hg budgets in different areas of China. The preliminary results showed that mean TGM concentrations were in the range of 1.60 – 2.88 ng m-3, with relatively higher levels observed at sites in Eastern China and Southwestern China and lower levels at sites in Northeastern and Northwestern China. TGM concentrations at remote sites of China were also higher than those reported from background sites in North America and Europe, and this is corresponding very well with the Chinese great anthropogenic Hg emissions. Gaseous oxidized mercury (GOM and particulate bounded mercury (PBM were in the ranges of 3.2 – 7.4 pg m−3 and 19.4 – 43.5 pg m-3, respectively. The preliminary result on precipitation showed mean precipitation THg concentrations were in the range of 2.7 – 18.0 ng L-1.

  5. Effects of the climate change on regional ozone dry deposition

    OpenAIRE

    Kolozsi-Komjáthy, E.; Mészáros, R.; Lagzi, I.

    2011-01-01

    This impact study investigates connections between the regional climate change and the tropospheric ozone deposition over different vegetations in Hungary due to the possible changes of atmospheric and environmental properties. The spatial and temporal variability of the dry deposition velocity of ozone was estimated for different time periods (1961–1990 for reference period and two future scenarios: 2021–2050 and 2071–2100). Simulations were performed with...

  6. Organic sedimentary deposits in Titan's dry lakebeds: Probable evaporite

    Science.gov (United States)

    Barnes, J.W.; Bow, J.; Schwartz, J.; Brown, R.H.; Soderblom, J.M.; Hayes, A.G.; Vixie, G.; Le, Mouelic S.; Rodriguez, S.; Sotin, C.; Jaumann, R.; Stephan, K.; Soderblom, L.A.; Clark, R.N.; Buratti, B.J.; Baines, K.H.; Nicholson, P.D.

    2011-01-01

    We report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near Titan's north pole in observations from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). We show evidence that the deposits are evaporitic, making Titan just the third known planetary body with evaporitic processes after Earth and Mars, and is the first that uses a solvent other than water. ?? 2011 Elsevier Inc.

  7. Chemical Bath Deposition of PbS:Hg2+ Nanocrystalline Thin Films

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    R. Palomino-Merino

    2013-01-01

    Full Text Available Nanocrystalline PbS thin films were prepared by Chemical Bath Deposition (CBD at 40 ± 2°C onto glass substrates and their structural and optical properties modified by in-situ doping with Hg. The morphological changes of the layers were analyzed using SEM and the X-rays spectra showing growth on the zinc blende (ZB face. The grain size determined by using X-rays spectra for undoped samples was found to be ~36 nm, whereas with the doped sample was 32–20 nm. Optical absorption spectra were used to calculate the Eg, showing a shift in the range 1.4–2.4 eV. Raman spectroscopy exhibited an absorption band ~135 cm−1 displaying only a PbS ZB structure.

  8. Hg1-xCdxTe vapor deposition on CdZnTe substrates by Closed Space Sublimation technique

    Science.gov (United States)

    Rubio, Sandra; Sochinskii, Nikolai V.; Repiso, Eva; Tsybrii, Zinoviia; Sizov, Fiodor; Plaza, Jose Luis; Diéguez, Ernesto

    2017-01-01

    Closed Space Sublimation (CSS) technique has been studied to deposit Hg1-xCdxTe polycrystalline films on CdZnTe substrates at the improved pressure-temperature conditions. The experimental results on film characterization suggest that the CSS optimal conditions are the argon atmospheric pressure (1013 mbar) and the deposition temperature in the range of 500-550 °C. These conditions provide macro-defect free Hg1-xCdxTe films with the uniform size and surface distribution of polycrystals.

  9. Aerosol dry deposition on canopies of plane obstacles

    Science.gov (United States)

    Petroff, A.; Zhang, L.

    2007-12-01

    A new model to describe aerosol transport and dry deposition on vegetative canopies has been proposed recently by Petroff et al. and applied to canopies of cylindrical obstacles such as coniferous forest (Petroff et al., 2007, Aerosol dry deposition on vegetative canopies. Part II: A new modeling approach and applications, submitted to Atmospheric Environment). In the present study, the approach is extended to canopies of plane obstacles such as grass, crop or broadleaf forest. The model takes into account the characteristics of the canopy, the aerosol and the aerodynamics. Deposition terms are modeled following an up-scaling procedure, which is based on the knowledge of collection dynamics on each individual obstacle and on the statistical distribution of these collecting elements. The statistical description applies to geometrical properties such as leaf characteristic length and orientation. Deposition mechanisms considered in this model include Brownian diffusion, interception, inertial impaction, turbulent impaction and gravitational settling. For interception, no adequate parameterisation is available in the literature to describe the collection on individual obstacle. Thus, an original parameterisation is derived for plane obstacle and is based on potential flow theory. Aerosol transport is described in a mono-dimensional configuration and neutral stratification of the atmosphere is assumed. Preliminary results indicate that the present model agrees with existing measurements data obtained both in wind-tunnel and on site.

  10. Dry deposition of large, airborne particles onto a surrogate surface

    Science.gov (United States)

    Kim, Eugene; Kalman, David; Larson, Timothy

    Simultaneous measurements of particle dry deposition flux and airborne number concentration in the open atmosphere were made using three different types of artificially generated particles in the size range 10-100 μm - perlite, diatomaceous earth and glass beads. A combination of gravimetric analysis, automated microscopy and sonic anemometry provided size-resolved estimates of both the inertial and gravitational components of the quasi-laminar layer particle deposition velocity, ( Vd) b, as a function of size. Eddy inertial deposition efficiency ( ηdI) was determined as a function of dimensionless eddy Stokes number (Stk e). In the range 3PNL-SA-6721, Pacific Northwest Laboratories, Richland, WA), used in several regulatory models, significantly under-predicted (up to seven times) ( Vd) b for large particles ( da>10 μm).

  11. Estimation of dry deposition fluxes of major inorganic species by canopy throughfall approach

    Institute of Scientific and Technical Information of China (English)

    JIN Lei; SHAO Min; ZENG Limin; ZHAO Dawei; TANG Dagang

    2006-01-01

    Dry deposition in China has not yet been intensively studied even though it constitutes an important pathway for acid deposition. The total deposition was monitored at Tieshanping catchment, a regional remote site in Chongqing City. The dry deposition loads of sulphur, calcium and nitrogen are estimated by using a canopy throughfall approach. The results indicate that the annual dry deposition loads of sulphur and calcium at Tieshanping site are much higher than those measured in forestry areas in other countries, while the dry deposition flux of nitrogen is at a comparable level. The dry deposition loads of sulphur, calcium and nitrogen are all higher than the wet deposition loads. Applying a canopy budget model has proven that the routine, simplified canopy throughfall approach may underestimate the dry deposition flux of nitrogen-containing species.

  12. Effect of SO2 Dry Deposition on Porous Dolomitic Limestones

    Science.gov (United States)

    Olaru, Mihaela; Aflori, Magdalena; Simionescu, Bogdana; Doroftei, Florica; Stratulat, Lacramioara

    2010-01-01

    The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100) and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA) were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units.

  13. Effect of SO2 Dry Deposition on Porous Dolomitic Limestones

    Directory of Open Access Journals (Sweden)

    Florica Doroftei

    2010-01-01

    Full Text Available The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100 and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units.

  14. Particle dry deposition to water surfaces: Processes and consequences

    DEFF Research Database (Denmark)

    Pryor, S.C.; Barthelmie, R.J.

    2000-01-01

    's oceans and seas is most significantly impacted by human activities. More than half of the world's population lives within 100 km of a coast and hence the overwhelming majority of anthropogenic fluxes to aquatic systems occur in the coastal zone. We discuss the particular challenges that arise from...... measurement requirements represent significant barriers to application to measurement of particle dry deposition fluxes although, as discussed, innovative solutions are now becoming available. In the final section, we examine meteorological controls on deposition to the coastal zone. This region of the world...... flux to coastal waters, atmosphere-surface exchange represents a significant component of the total flux and may be particularly critical during the summertime when both the riverine input and ambient nutrient concentrations are often at a minimum. In this chapter, we present an overview...

  15. Simulating ozone dry deposition at a boreal forest with a multi-layer canopy deposition model

    Science.gov (United States)

    Zhou, Putian; Ganzeveld, Laurens; Rannik, Üllar; Zhou, Luxi; Gierens, Rosa; Taipale, Ditte; Mammarella, Ivan; Boy, Michael

    2017-01-01

    A multi-layer ozone (O3) dry deposition model has been implemented into SOSAA (a model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to improve the representation of O3 concentration and flux within and above the forest canopy in the planetary boundary layer. We aim to predict the O3 uptake by a boreal forest canopy under varying environmental conditions and analyse the influence of different factors on total O3 uptake by the canopy as well as the vertical distribution of deposition sinks inside the canopy. The newly implemented dry deposition model was validated by an extensive comparison of simulated and observed O3 turbulent fluxes and concentration profiles within and above the boreal forest canopy at SMEAR II (Station to Measure Ecosystem-Atmosphere Relations II) in Hyytiälä, Finland, in August 2010. In this model, the fraction of wet surface on vegetation leaves was parametrised according to the ambient relative humidity (RH). Model results showed that when RH was larger than 70 % the O3 uptake onto wet skin contributed ˜ 51 % to the total deposition during nighttime and ˜ 19 % during daytime. The overall contribution of soil uptake was estimated about 36 %. The contribution of sub-canopy deposition below 4.2 m was modelled to be ˜ 38 % of the total O3 deposition during daytime, which was similar to the contribution reported in previous studies. The chemical contribution to O3 removal was evaluated directly in the model simulations. According to the simulated averaged diurnal cycle the net chemical production of O3 compensated up to ˜ 4 % of dry deposition loss from about 06:00 to 15:00 LT. During nighttime, the net chemical loss of O3 further enhanced removal by dry deposition by a maximum ˜ 9 %. Thus the results indicated an overall relatively small contribution of airborne chemical processes to O3 removal at this site.

  16. Characterizing dry deposition of mercury in urban runoff

    Science.gov (United States)

    Fulkerson, M.; Nnadi, F.N.; Chasar, L.S.

    2007-01-01

    Stormwater runoff from urban surfaces often contains elevated levels of toxic metals. When discharged directly into water bodies, these pollutants degrade water quality and impact aquatic life and human health. In this study, the composition of impervious surface runoff and associated rainfall was investigated for several storm events at an urban site in Orlando, Florida. Total mercury in runoff consisted of 58% particulate and 42% filtered forms. Concentration comparisons at the start and end of runoff events indicate that about 85% of particulate total mercury and 93% of particulate methylmercury were removed from the surface before runoff ended. Filtered mercury concentrations showed less than 50% reduction of both total and methylmercury from first flush to final flush. Direct comparison between rainfall and runoff at this urban site indicates dry deposition accounted for 22% of total inorganic mercury in runoff. ?? 2007 Springer Science+Business Media B.V.

  17. Monitoring dry deposition of gases and particles over a forest

    Science.gov (United States)

    Mennen, M. G.; van Putten, E. M.; Uiterwijk, J. W.; Hogenkamp, J. E. M.; Wiese, C. J.; Draaijers, G.; Erisman, J. W.; Otjes, R. P.; Wyers, G. P.

    1996-12-01

    Dry deposition fluxes of acidifying and eutrophying compounds are continuously determined at Speulder forest, a Douglas fir site in the centre of the Netherlands. The monitoring equipment, installed on a 36-m high tower, consists of a sonic anemometer, a cup anemometer, a wind vane, a Bowen ratio system, three temperature/r.h. sensors, and gas analyzers to measure gradients of SO 2, NO x and NH 3 and concentrations of HCl, HNO 2 and HNO 3. Particles are sampled in two size ranges (<2.5 mm and 2.5-10 mm) on filters, which are analysed for acidifying components and basic cations. Fluxes of SO 2, NO x and NH 3 are determined with the gradient method, while fluxes of the other components are estimated with the inferential method. Parameterizations of the surface resistance ( Rc) for gases are derived from measurements obtained during periods that meet criteria with respect to homogeneous fetch, stationary flow, etc. Parameterized Rc values are used to estimate fluxes during periods that don't fulfil these demands. In this way, yearly average fluxes can be determined. In 1995, the total deposition fluxes of SO x(=SO 2+SO 42-), NO y(=NO x+NO 3-+HNO 2+HNO 3) and NH x, (=NH 3+NH 4+) were 450, 630 and 1620 eq. ha -1 a -1, respectively.

  18. Accuracy of cuticular resistance parameterizations in ammonia dry deposition models

    Science.gov (United States)

    Schrader, Frederik; Brümmer, Christian; Richter, Undine; Fléchard, Chris; Wichink Kruit, Roy; Erisman, Jan Willem

    2016-04-01

    Accurate representation of total reactive nitrogen (Nr) exchange between ecosystems and the atmosphere is a crucial part of modern air quality models. However, bi-directional exchange of ammonia (NH3), the dominant Nr species in agricultural landscapes, still poses a major source of uncertainty in these models, where especially the treatment of non-stomatal pathways (e.g. exchange with wet leaf surfaces or the ground layer) can be challenging. While complex dynamic leaf surface chemistry models have been shown to successfully reproduce measured ammonia fluxes on the field scale, computational restraints and the lack of necessary input data have so far limited their application in larger scale simulations. A variety of different approaches to modelling dry deposition to leaf surfaces with simplified steady-state parameterizations have therefore arisen in the recent literature. We present a performance assessment of selected cuticular resistance parameterizations by comparing them with ammonia deposition measurements by means of eddy covariance (EC) and the aerodynamic gradient method (AGM) at a number of semi-natural and grassland sites in Europe. First results indicate that using a state-of-the-art uni-directional approach tends to overestimate and using a bi-directional cuticular compensation point approach tends to underestimate cuticular resistance in some cases, consequently leading to systematic errors in the resulting flux estimates. Using the uni-directional model, situations where low ratios of total atmospheric acids to NH3 concentration occur lead to fairly high minimum cuticular resistances, limiting predicted downward fluxes in conditions usually favouring deposition. On the other hand, the bi-directional model used here features a seasonal cycle of external leaf surface emission potentials that can lead to comparably low effective resistance estimates under warm and wet conditions, when in practice an expected increase in the compensation point due to

  19. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  20. Evaluation and intercomparison of five major dry deposition algorithms in North America

    Science.gov (United States)

    Dry deposition of various pollutants needs to be quantified in air quality monitoring networks as well as in chemical transport models. The inferential method is the most commonly used approach in which the dry deposition velocity (Vd) is empirically parameterized as a function o...

  1. Comparison of annual dry and wet deposition fluxes of selected pesticides in Strasbourg, France

    Energy Technology Data Exchange (ETDEWEB)

    Sauret, Nathalie [Marseilles University, Laboratoire Chimie Provence - UMR 6264, Campus Saint Charles, Case 29, 3 Place Victor Hugo, 13331 Marseilles Cedex 03 (France); Wortham, Henri [Marseilles University, Laboratoire Chimie Provence - UMR 6264, Campus Saint Charles, Case 29, 3 Place Victor Hugo, 13331 Marseilles Cedex 03 (France)], E-mail: Henri.Wortham@univ-provence.fr; Strekowski, Rafal [Marseilles University, Laboratoire Chimie Provence - UMR 6264, Campus Saint Charles, Case 29, 3 Place Victor Hugo, 13331 Marseilles Cedex 03 (France); Herckes, Pierre [Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ 85287-1604 (United States); Nieto, Laura Ines [Marseilles University, Laboratoire Chimie Provence - UMR 6264, Campus Saint Charles, Case 29, 3 Place Victor Hugo, 13331 Marseilles Cedex 03 (France)

    2009-01-15

    This work summarizes the results of a study of atmospheric wet and dry deposition fluxes of Deisopropyl-atrazine (DEA), Desethyl-atrazine (DET), Atrazine, Terbuthylazine, Alachlor, Metolachlor, Diflufenican, Fenoxaprop-p-ethyl, Iprodione, Isoproturon and Cymoxanil pesticides conducted in Strasbourg, France, from August 2000 through August 2001. The primary objective of this work was to calculate the total atmospheric pesticide deposition fluxes induced by atmospheric particles. To do this, a modified one-dimensional cloud water deposition model was used. All precipitation and deposition samples were collected at an urban forested park environment setting away from any direct point pesticide sources. The obtained deposition fluxes induced by atmospheric particles over a forested area showed that the dry deposition flux strongly contributes to the total deposition flux. The dry particle deposition fluxes are shown to contribute from 4% (DET) to 60% (cymoxanil) to the total deposition flux (wet + dry). - A modified one-dimensional cloud water deposition model is used to estimate the deposition fluxes of pesticides in the particle phase and compare the relative importance of dry and wet depositions.

  2. Influence of Rough Flow over Sea Surface on Dry Atmospheric Deposition Velocities

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2013-01-01

    Full Text Available A Meteorological model and a dry deposition module were used to estimate the effects of sea surface rough flow (SSRF over the sea surface on dry deposition velocities. The dry deposition turbulence resistance, Ra, and sub-layer resistance, Rb, decreased more than 10% and 5% due to SSRF, respectively. For example, for HNO3, the mean dry deposition velocities (Vd were 0.51 cm s-1 in January, 0.58 in April, 0.65 cm s-1 in July and 0.79 cm s-1 in October with only smooth flow over the sea surface. However, the SSRF increased the Vd of HNO3 by 5 - 20% in the east China seas. These results show that SSRF is an important factor in estimating surface roughness to further improve calculation of the dry deposition velocities over the ocean. Improvements in parameterization of sea roughness length will be a worthwhile effort in related future studies.

  3. The impact of drought on ozone dry deposition over eastern Texas

    Science.gov (United States)

    Huang, Ling; McDonald-Buller, Elena C.; McGaughey, Gary; Kimura, Yosuke; Allen, David T.

    2016-02-01

    Dry deposition represents a critical pathway through which ground-level ozone is removed from the atmosphere. Understanding the effects of drought on ozone dry deposition is essential for air quality modeling and management in regions of the world with recurring droughts. This work applied the widely used Zhang dry deposition algorithm to examine seasonal and interannual changes in estimated ozone dry deposition velocities and component resistances/conductances over eastern Texas during years with drought (2006 and 2011) as well as a year with slightly cooler temperatures and above average rainfall (2007). Simulated area-averaged daytime ozone dry deposition velocities ranged between 0.26 and 0.47 cm/s. Seasonal patterns reflected the combined seasonal variations in non-stomatal and stomatal deposition pathways. Daytime ozone dry deposition velocities during the growing season were consistently larger during 2007 compared to 2006 and 2011. These differences were associated with differences in stomatal conductances and were most pronounced in forested areas. Reductions in stomatal conductances under drought conditions were highly sensitive to increases in vapor pressure deficit and warmer temperatures in Zhang's algorithm. Reductions in daytime ozone deposition velocities and deposition mass during drought years were associated with estimates of higher surface ozone concentrations.

  4. Speciated particle dry deposition to the sea surface: Results from ASEPS '97

    DEFF Research Database (Denmark)

    Pryor, S.C.; Barthelmie, R.J.; Geernaert, L.L.S.

    1999-01-01

    It has been postulated that atmospheric pathways may comprise a significant source of nitrogen for aquatic ecosystems and excess atmospheric deposition to coastal areas may be a major cause of eutrophication. Dry deposition of nitrogen containing particles is a potential, but poorly quantified...... on Precipitation Scavenging and Atmosphere-Surface Exchange Processes. AMS, Richland, Washington, USA, 12pp.) model to calculate size-segregated dry deposition of particle inorganic nitrogen compounds to the western Baltic during the late Spring of 1997 based on data collected as part of the Air-Sea Exchange...... Process Study (ASEPS). The results show that over a 15 d period in April and May dry deposition fluxes varied between 30 and 400 mu g m(-2) d(-1) for nitrate and 1 and 120 mu g m(-2) d(-1) for ammonium. Sensitivity analyses run to assess the potential bounds on actual dry deposition indicate that...

  5. Reduction of Hg1 - xCdxTe native oxide during the SiNx deposition process

    Science.gov (United States)

    Sudo, G.; Kajihara, N.; Miyamoto, Y.; Tanikawa, K.

    1987-11-01

    Electron cyclotron resonance plasma chemical vapor deposition enables low-temperature SiNx deposition on Hg1-xCdxTe (MCT). The SiNx film has an excellent interface on MCT with a low surface state density of 1.0×1011 cm-2 eV-1 and a low fixed charge of -1.4×1011 cm-2. A detailed analysis by x-ray photoelectron spectroscopy and Auger electron spectroscopy spectra of Te, Cd, and Si at the SiNx/MCT interface indicated that the SiNx deposition reduces the naturally grown MCT native oxide. The oxygen taken from Te oxidizes SiH4 and produces silicon oxides which remain in the SiNx film. Since a chemical shift caused by oxidized Cd at the fresh surface of MCT is very slight, intentionally oxidized samples were used to confirm the above reaction. The analysis of the shape of the Si(2p) peak at the interface indicated that the silicon oxides are composed of SiO and SiO2. Thermodynamic considerations support such a mechanism.

  6. Characterization of Wet and Dry Deposition in the Downwind of Industrial Sources in a Dry Tropical Area

    Directory of Open Access Journals (Sweden)

    Raj K. Singh

    2001-01-01

    Full Text Available An atmospheric deposition study was conducted in the downwind of Shaktinagar Thermal Power Plant (STPP, Renusagar Thermal Power Plant (RTPP, and Anpara Thermal Power Plant (ATPP, at Singrauli region, Uttar Pradesh (UP, India to characterize dry and wet deposition in relation to different pollution loading. During the study period, dry and wet depositions and levels of gaseous pollutants (SO2 and NO2 were estimated across the sites. Dry deposition was collected on a monthly basis and wet deposition on an event basis. Depositions were analyzed for pH, nitrate (NO3�, ammonium (NH4+, and sulphate (SO42� contents. Dry deposition rate both collected as clearfall and throughfall varied between 0.15 to 2.28 and 0.33 to 3.48 g m�2 day�1, respectively, at control and maximally polluted sites. The pH of dry deposition varied from 5.81 to 6.89 during winter and 6.09 to 7.02 during summer across the sites. During the rainy season, the mean pH of clear wet deposition varied from 6.56 to 7.04 and throughfall varied from 6.81 to 7.22. The concentrations of NO2 and SO2 pollutants were highest during the winter season. Mean SO2 concentrations varied from 18 to 75 �g m�3 at control and differently polluted sites during the winter season. The variation in NO2 concentrations did not show a pattern similar to that of SO2. The highest NO2 concentration during the winter season was 50 �g m�3, observed near RTPP. NO2 concentration did not show much variation among different sites, suggesting that the sources of NO2 emission are evenly distributed along the sites. The concentrations of NH4+, NO3�, and SO42� ions in dry deposition were found to be higher in summer as compared to the winter season. In dry deposition (clearfall the concentrations of NH4+, NO3�, and SO42� varied from 0.13 to 1.0, 0.81 to 1.95, and 0.82 to 3.27 mg l�1, respectively, during winter. In wet deposition (clearfall, the above varied from 0.14 to 0.74, 0.81 to 1.82, and 0

  7. Atmospheric trace elements at Enewetak Atoll: 2. Transport to the ocean by wet and dry deposition

    Science.gov (United States)

    Arimoto, R.; Duce, R. A.; Ray, B. J.; Unni, C. K.

    1985-02-01

    The concentrations of trace elements in precipitation and dry deposition are presented for samples collected at Enewetak Atoll (11°N, 162° E) during SEAREX experiments in 1979. The concentrations of Al, Sc, Mn, Fe, Co, and Th in rain are dominated by crustal material, and for these elements, wet deposition evidently exceeds dry deposition. For most of these elements the present rates of atmospheric deposition at Enewetak are similar to their mean rate of accumulation in sediments over the past 5-10,000 years, suggesting that the air-to-sea exchange of particles is closely tied to the sedimentary cycle of the mid-Pacific. Noncrustal sources govern the concentrations of Pb, Zn, Cu, Se, and Cd in wet and dry deposition samples. Analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples, and even though these estimates do not necessarily reflect the dry deposition to the ocean surface, the results suggest that recycled sea spray often amounts to more than 50% of the total dry deposition of the enriched elements. Recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements. The net deposition rates of elements such as Cu and Zn are greater than or equal to their inputs from vertical mixing, but the net deposition of Pb clearly exceeds the input from upwelling. The current net deposition rates of the enriched elements are also similar to their rates of removal to sediments. These results indicate that air-sea exchange processes may significantly affect the chemistry of trace metals in the open ocean.

  8. Foliar loading and metabolic assimilation of dry deposited nitric acid air pollutants by trees.

    Science.gov (United States)

    Padgett, Pamela E; Cook, Hillary; Bytnerowicz, Andrzej; Heath, Robert L

    2009-01-01

    Dry deposition of nitric acid vapor (HNO(3)) is a major contributor to eutrophication of natural ecosystems. Although soil fertilization by nitrogen deposition is considered to be the primary pathway for changes in plant nutrient status and shifts in ecological structure, the aerial portion of plants offer many times the surface area in which to collect atmospheric HNO(3). As much as 60% of deposited nitrogen may be retained in the canopy and not land on the soil surface below. Although uptake and assimilation appears to contribute to retention, only a small percentage of dry deposition is recovered in assimilated N pools. To test the importance of biological activity on the process and measurements of dry deposition, we used controlled environmental chambers to compare deposition to living and freeze-dried foliage of four tree species using (15)N-labeled HNO(3). In living trees, assimilation was determined by (15)N incorporation into free amino acids and proteins in leaves and roots. From 10% to 60% of the retained HNO(3) was incorporated into the biologically active nitrogen pool. The remainder was bound to foliar surfaces in an insoluble form in either living or freeze-dried foliage. The importance of the boundary layer conditions emerged as a primary factor controlling dry deposition characteristics and measurements.Trade names and commercial enterprises or products are mentioned solely for information. No endorsements by the U.S. Department of Agriculture are implied.

  9. Dry deposition of sulphur on the Mpumalanga highveld: a pilot study using the inferential method

    CSIR Research Space (South Africa)

    Zunckel, M

    1996-10-01

    Full Text Available A pilot study which uses the inferential method to estimate dry deposition of sulphur on the central Mpumalanga highveld is discussed in this paper. Ambient concentrations of sulphur dioxide, particulates and micro-meteorological measurements from 2...

  10. Dry deposition of reduced nitrogen in the United States Pacific Northwest for 2002

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This spatial data set was created by the U.S. Geological Survey (USGS) to represent the amount of dry deposition of reduced nitrogen in the Pacific Northwest region...

  11. Dry deposition velocity of total suspended particles and meteorological influence in four locations in Guangzhou, China

    Institute of Scientific and Technical Information of China (English)

    Leifu Chen; Shaolin Peng; Jingang Liu; Qianqian Hou

    2012-01-01

    Dry deposition velocity of total suspended particles (TSP) is an effective parameter that describes the speed of atmospheric particulate matter deposit to the natural surface.It is also an important indicator to the capacity of atmosphere self-depuration.However,the spatial and temporal variations in dry deposition velocity of TSP at different urban landscapes and the relationship between dry deposition velocity and the meteorological parameters are subject to large uncertainties.We concurrently investigated this relationship at four different landscapes of Guangzhou,from October to December of 2009.The result of the average dry deposition velocity is (1.49 ±0.77),(1.44 ± 0.77),(1.13 ± 0.53) and (1.82 ± 0.82) cm/sec for urban commercial landscape,urban forest landscape,urban residential landscape and country landscape,respectively.This spatial variation can be explained by the difference of both particle size composition of TSP and meteorological parameters of sampling sites.Dry deposition velocity of TSP has a positive correlation with wind speed,and a negative correlation with temperature and relative humidity.Wind speed is the strongest factor that affects the magnitude of TSP dry deposition velocity,and the temperature is another considerable strong meteorological factor.We also find out that the relative humidity brings less impact,especially during the dry season.It is thus implied that the current global warming and urban heat island effect may lead to correlative changes in TSP dry deposition velocity,especially in the urban areas.

  12. Improved Formulations for Air-Surface Exchanges Related to National Security Needs: Dry Deposition Models

    Energy Technology Data Exchange (ETDEWEB)

    Droppo, James G.

    2006-07-01

    The Department of Homeland Security and others rely on results from atmospheric dispersion models for threat evaluation, event management, and post-event analyses. The ability to simulate dry deposition rates is a crucial part of our emergency preparedness capabilities. Deposited materials pose potential hazards from radioactive shine, inhalation, and ingestion pathways. A reliable characterization of these potential exposures is critical for management and mitigation of these hazards. A review of the current status of dry deposition formulations used in these atmospheric dispersion models was conducted. The formulations for dry deposition of particulate materials from am event such as a radiological attack involving a Radiological Detonation Device (RDD) is considered. The results of this effort are applicable to current emergency preparedness capabilities such as are deployed in the Interagency Modeling and Atmospheric Assessment Center (IMAAC), other similar national/regional emergency response systems, and standalone emergency response models. The review concludes that dry deposition formulations need to consider the full range of particle sizes including: 1) the accumulation mode range (0.1 to 1 micron diameter) and its minimum in deposition velocity, 2) smaller particles (less than .01 micron diameter) deposited mainly by molecular diffusion, 3) 10 to 50 micron diameter particles deposited mainly by impaction and gravitational settling, and 4) larger particles (greater than 100 micron diameter) deposited mainly by gravitational settling. The effects of the local turbulence intensity, particle characteristics, and surface element properties must also be addressed in the formulations. Specific areas for improvements in the dry deposition formulations are 1) capability of simulating near-field dry deposition patterns, 2) capability of addressing the full range of potential particle properties, 3) incorporation of particle surface retention/rebound processes, and

  13. Dry deposition and resuspension of particle-associated metals near a freeway in Los Angeles

    Science.gov (United States)

    Sabin, Lisa D.; Hee Lim, Jeong; Teresa Venezia, Maria; Winer, Arthur M.; Schiff, Kenneth C.; Stolzenbach, Keith D.

    Dry atmospheric deposition represents a potentially large source of pollutant metal contamination in urban stormwater runoff, yet there is a limited amount of research on the relationship between atmospheric emissions and water quality problems in urban areas. In Los Angeles, with air quality that ranks among the worst in the United States, significant quantities of toxic materials are released into the atmosphere every day, and paved road dust represents the largest source of particle-associated metal emissions to the atmosphere. In order to better understand the role of roadways as a source of localized metal deposition, we characterized the horizontal dry deposition patterns of chromium, copper, lead, nickel and zinc upwind and at increasing distances downwind of the I-405 Freeway in coastal Los Angeles. Dry deposition fluxes and atmospheric concentrations of these metals were highest at the site closest to the freeway, and reduced to approximately urban background concentrations between 10 and 150 m downwind of the freeway. Compared with urban background, atmospheric particle size distributions indicated the freeway was a significant source of these metals on large particles >6 μm in diameter, which deposit close to their source and account for the increased dry deposition flux rates observed near the freeway. The spatial pattern of measured deposition flux was well predicted by a relatively simple line-source Gaussian plume model modified to include particle deposition and resuspension. The model results indicated dilution by vertical dispersion of the plume was the most important mechanism regulating downwind concentrations and deposition.

  14. Atmospheric wet and dry deposition of trace elements at 10 sites in Northern China

    Science.gov (United States)

    Pan, Y. P.; Wang, Y. S.

    2015-01-01

    Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil or water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatiotemporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at 10 sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites, while the wet deposition exhibited less spatial variation. In addition, the seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for potassium, nickel, arsenic, lead, zinc, cadmium, selenium, silver and thallium, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution of the particles. We found that atmospheric inputs of copper, lead, zinc, cadmium, arsenic and

  15. Wet and dry deposition of atmospheric nitrogen at ten sites in Northern China

    Directory of Open Access Journals (Sweden)

    Y. P. Pan

    2012-01-01

    Full Text Available Emissions of reactive nitrogen (N species can affect surrounding ecosystems via atmospheric deposition. However, few long-term and multi-site measurements have focused on both the wet and the dry deposition of individual N species in large areas of Northern China. Thus, the magnitude of atmospheric deposition of various N species in Northern China remains uncertain. In this study, the wet and dry atmospheric deposition of different N species was investigated during a three-year observation campaign at ten selected sites in Northern China. The results indicate that N deposition levels in Northern China were high with a ten-site, three-year average of 60.6 kg N ha−1 yr−1. The deposition levels showed spatial and temporal variation in the range of 28.5–100.4 kg N ha−1 yr−1. Of the annual total deposition, 40% was deposited via precipitation, and the remaining 60% was comprised of dry-deposited forms. Compared with gaseous N species, particulate N species were not the major contributor of dry-deposited N; they contributed approximately 10% to the total flux. On an annual basis, oxidized species accounted for 21% of total N deposition, thereby implying that other forms of gaseous N, such as NH3, comprised a dominant portion of the total flux. The contribution of NO3 to N deposition was enhanced in certain urban and industrial areas. As expected, the total N deposition in Northern China was significantly larger than the values reported by national scale monitoring networks in Europe, North America and East Asia because of high rates of wet deposition and gaseous NH3 dry deposition. The results have three important implications. First, atmospheric N deposition in Northern China falls within the range of critical loads for temperate forests and grasslands, a threshold above which harmful ecological effects to specified parts of temperate ecosystems often

  16. Dry deposition parameterization of sulfur oxides in a chemistry and general circulation

    NARCIS (Netherlands)

    Ganzeveld, L.N.; Lelieveld, J.; Roelofs, G.J.

    1998-01-01

    A dry deposition scheme, originally developed to calculate the deposition velocities for the trace gases O3, NO2, NO, and HNO3 in the chemistry and general circulation European Centre Hamburg Model (ECHAM), is extended to sulfur dioxide (SO2) and sulfate (SO42-). In order to reduce some of the short

  17. Phenological controls on inter-annual variability in ozone dry deposition velocity

    Science.gov (United States)

    Clifton, Olivia; Fiore, Arlene; Munger, J. William; Shevliakova, Elena; Horowitz, Larry; Malyshev, Sergey; Griffin, Kevin

    2016-04-01

    Our understanding of ozone removal by northern mid-latitude temperate deciduous forests is largely based on short-term observational studies, and thus year-to-year variations of this sink have received little attention. The specific pathways for ozone dry deposition include stomatal uptake and other non-stomatal processes that are poorly understood. Given the importance of ozone dry deposition to model accurately the tropospheric ozone budget and regional air quality, an improved mechanistic understanding of this ozone sink is needed. We investigate here the physical and biological controls on inter-annual variations in seasonal and diurnal cycles of ozone dry deposition velocity using nine years of hourly observations of eddy covariance ozone flux and concentration measurements at Harvard Forest, a northern mid-latitude temperate deciduous forest. We also use coincident eddy covariance water vapor flux and sensible heat flux and other micrometeorological measurements to infer stomatal conductance in order to separate the impacts of stomatal versus non-stomatal pathways on ozone deposition. There is a difference of approximately a factor of two between minimum and maximum monthly daytime mean ozone dry deposition velocities at Harvard Forest. The highest summertime mean ozone dry deposition velocities occur during 1998 and 1999 (0.72 cm/s), and similar seasonal and diurnal cycles occur in both years. The similar dry deposition velocities during these two years, however, may reflect compensation between different processes as mean daytime summertime stomatal conductance during 1998 is roughly 1.5 times higher than for 1999, suggesting large year-to-year variations in non-stomatal as well as stomatal uptake of ozone. We partition the onset and decline of the growing season each year into different periods using spring and fall phenology observations at Harvard Forest. Combining the dry deposition velocities across years during each phenological period, we find that

  18. Isotopic Composition of Gaseous Elemental Mercury (Hg0) at Various Sites in Japan

    Science.gov (United States)

    Yamakawa, A.; Moriya, K.; Yoshinaga, J.

    2015-12-01

    Mercury (Hg) is a toxic heavy metal, which exists in various chemical forms in the environmental system. In the atmosphere, Hg exists in three forms (Hg0(g), Hg+2(g), and Hg(p)). Hg0(g) is the dominant species of atmospheric Hg, accounting for >95% of the total Hg in the atmosphere. Because Hg0(g) is highly volatile and has limited solubility in water, it cannot be easily removed by wet or dry deposition processes. Therefore, the residence time of Hg0(g) in the atmosphere is relatively long (1 to 2 years), allowing long-range transport from mercury emission source(s). Conversely, Hg+2(g) and Hg(p) are effectively removed from the atmosphere through wet and dry depositions. The determination of mercury source attribution using quantitative data is challenging because Hg0(g) may be deposited on an area upon oxidation to Hg+2(g) and associated with aerosols and particulates to form Hg(p) while the global cycling of Hg0(g). Over the last decade, the development of analytical methods of highly precise Hg isotopic measurements demonstrated mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in environmental samples. For instance, MDF of Hg isotopes is thought to occur during various natural and industrial Hg transformations. MIF of Hg isotopes is observed during abiotic reduction, photochemical and non-photochemical, and physical and chemical processes. Such processes lead to differences in the Hg isotopic composition of different emission sources, both natural and anthropogenic, and atmospheric processes (i.e., transportation, oxidation/reduction, deposition, and reemission). Therefore, Hg isotopic compositions could be used to trace the sources and processes of atmospheric Hg. For securing the reliability and accuracy of atmospheric Hg isotope data, the methods of collection, pretreatment, and isotopic measurement for Hg0(g) were developed to obtain high recovery yield of samples with no Hg isotopic fractionation during each

  19. Modeling dry deposition of reactive nitrogen in China with RAMS-CMAQ

    Science.gov (United States)

    Han, Xiao; Zhang, Meigen; Skorokhod, Andrei; Kou, Xingxia

    2017-10-01

    China has the world highest production of reactive nitrogen (Nr), and the Nr consumption increased sharply during the last decade. However, the potential environmental influence of dry nitrogen (N) deposition in China remains uncertain due to that the long-term measurement or remote sensing of various N species are difficult. This requires a better understanding of dry N deposition over China in its various forms and including magnitude and distribution features. Thus, the air quality modeling system RAMS-CMAQ was applied to simulate dry deposition of Nr over China from 2010 to 2014. The model results were then analyzed to investigate the long-term spatial and temporal distributions of major inorganic nitrogen (N) components (10 species) and selected organic N components (5 species). Comparisons between modeled and observed deposition rates and surface mass concentrations showed generally good agreement. Model results indicated a total dry N deposition budget of 9.31 Tg N yr-1 in China, including 4.29 Tg N yr-1 as NOy and 4.43 Tg N yr-1 as NH3. NOy was the main component of dry N deposition in the Beijing-Tianjin-Hebei area (0.31 Tg N yr-1), the Yangtze River Delta (0.29 Tg N yr-1), and the Pearl River Delta (0.09 Tg N yr-1), where the major megacity clusters of China are located. NH3 was the main component of dry N deposition in Shandong province (0.24 Tg N yr-1), Northeast China (0.46 Tg N yr-1), the Sichuan Basin (0.48 Tg N yr-1), and central China (0.95 Tg N yr-1), where the major agricultural regions are located. The highest values of the deposition flux for NH3 occurred in Shandong province (19.40 kg N ha-1 yr-1) and Beijing-Tianjin-Hebei (17.20 kg N ha-1 yr-1). The seasonal variation of total dry N deposition was obvious in the east part of China, and was higher in July and lower in January. The spatio-temporal variations and major sources of dry N deposition were strongly heterogeneous, implying that the comprehensive pollution control strategies should be

  20. Magma ascent, fragmentation and depositional characteristics of "dry" maar volcanoes: Similarities with vent-facies kimberlite deposits

    Science.gov (United States)

    Berghuijs, Jaap F.; Mattsson, Hannes B.

    2013-02-01

    Several maar craters within the Lake Natron-Engaruka monogenetic volcanic field (LNE-MVF) of northern Tanzania show compelling evidence for magmatic fragmentation and dry deposition. This is in contradiction of the common belief that most maars are formed through the explosive interaction between ascending magma and ground- or surface water. We here present a detailed study on the eruptive and depositional characteristics of the Loolmurwak and Eledoi maar volcanoes, two of the largest craters in the LNE-MVF, focusing on high-resolution stratigraphy, sedimentology, grain size distribution, pyroclast textures and morphologies, bulk geochemistry and mineral chemistry. At both maars, ejected material has been emplaced by a combination of pyroclastic surges and fallout. Indicators of phreatomagmatic fragmentation and wet deposition, such as impact sags, accretionary lapilli, vesiculated tuffs and plastering against obstacles, are absent in the deposits. Juvenile material predominantly occurs as fluidal-shaped vesicular melt droplets and contains no glass shards produced by the breakage of bubble walls. The Eledoi deposits comprise a large amount of inversely graded beds and lenses, which result from grain flow in a dry depositional environment. Preferential deposition of fine material toward the northern side of its crater can be related to effective wind winnowing in a dry eruption plume. This large variety of observations testifies to the dominance of magmatic fragmentation as well as dry deposition at the Loolmurwak and Eledoi maars, which is in line with what has been found for other structures in the LNE-MVF but contrasts with current ideas on maar formation. We infer that a volatile-rich, olivine melilitic magma was formed by small amounts of partial melting at upper mantle depths. With minimum average ascent rates of 5.3 m s- 1 for Loolmurwak and 26.2 m s- 1 for Eledoi, this magma rapidly moved toward the surface and exsolved a substantial amount of volatiles

  1. Dry deposition of particulate matter at an urban forest, wetland and lake surface in Beijing

    Science.gov (United States)

    Liu, Jiakai; Zhu, Lijuan; Wang, Huihui; Yang, Yilian; Liu, Jiatong; Qiu, Dongdong; Ma, Wu; Zhang, Zhenming; Liu, Jinglan

    2016-01-01

    The dry deposition of particular matters from atmosphere to ecosystems is an undesirable consequence of this pollution while the deposition process is also influenced by different land use types. In current study, concentration of fine particles, coarse particles and meteorological data were collected during the daytime in an artificial forest, wetland and a water surface in the Beijing Olympic Park. Dry deposition velocity, fluxes and vegetation collection were calculated by different models and the results were compared. The results show: (1) the deposition velocity onto the forest canopy was higher than which onto the wetland and the water surface and the velocity varied in different seasons; (2) the fine particles deposited most in the winter while the coarse particles was in the spring; (3) the vegetation collection rates of fine particles were lower than coarse particles, and the forest collected more PMs than the wetland plants.

  2. Modelling atmospheric dry deposition in urban areas using an urban canopy approach

    Directory of Open Access Journals (Sweden)

    N. Cherin

    2014-12-01

    Full Text Available Atmospheric dry deposition is typically modelled using an average roughness length, which depends on land use. This classical roughness-length approach cannot account for the spatial variability of dry deposition in complex settings such as urban areas. Urban canopy models have been developed to parametrise momentum and heat transfer. We extend this approach here to mass transfer and a new dry deposition model based on the urban canyon concept is presented. It uses a local mixing length parametrisation of turbulence within the canopy, and a description of the urban canopy via key parameters to provide spatially-distributed dry deposition fluxes. Three different flow regimes are distinguished in the urban canyon depending on the height-to-width ratio of built areas: isolated roughness flow, wake interference flow and skimming flow. Differences between the classical roughness-length model and the model developed here are investigated. Sensitivity to key parameters are discussed. This approach provides spatially-distributed dry deposition fluxes that depend on surfaces (streets, walls, roofs and flow regimes (recirculation and ventilation within the urban area.

  3. Modelling atmospheric dry deposition in urban areas using an urban canopy approach

    Directory of Open Access Journals (Sweden)

    N. Cherin

    2015-03-01

    Full Text Available Atmospheric dry deposition is typically modelled using an average roughness length, which depends on land use. This classical roughness-length approach cannot account for the spatial variability of dry deposition in complex settings such as urban areas. Urban canopy models have been developed to parametrise momentum and heat transfer. We extend this approach here to mass transfer, and a new dry deposition model based on the urban canyon concept is presented. It uses a local mixing-length parametrisation of turbulence within the canopy, and a description of the urban canopy via key parameters to provide spatially distributed dry deposition fluxes. Three different flow regimes are distinguished in the urban canyon depending on the height-to-width ratio of built areas: isolated roughness flow, wake interference flow and skimming flow. Differences between the classical roughness-length model and the model developed here are investigated. Sensitivity to key parameters are discussed. This approach provides spatially distributed dry deposition fluxes that depend on surfaces (streets, walls, roofs and flow regimes (recirculation and ventilation within the urban area.

  4. Dispersion and dry and wet deposition of PAHs in an atmospheric environment.

    Science.gov (United States)

    Ozaki, N; Nitta, K; Fukushima, T

    2006-01-01

    The atmospheric concentration and dry and wet deposition were measured for particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) from August to December in Higashi-Hiroshima City, Japan. PM concentration of fine particles (0.6-7 microm) was 5.7-75.1 micro m(-3), and coarse particles (> 7 microm) was 2.2-22.3 microg m(-3). Total PAHs concentration of fine particles was 0.14-16.3 ng m(-3), and coarse particles was 0.01-0.77 ng m(-3). Their concentration increased on non-rainy days and decreased rapidly on rainy days. For seasonal fluctuations of PAHs, their concentrations decreased from summer to winter, and the rate of decrease was more distinct for fine particles. For total (dry + wet) depositions, the PM flux was 1.9-11.2 mg m(-2) d(-1), and the total PAHs flux was 1.9-97.2 ng m(-3) d(-1). From these measurements, the yearly total loading of PAHs was estimated for the particle phase. Total loading was 28 microg m(-2) y(-1) for the dry deposition and 52 mg m(-2) y(-1) for the wet deposition. The loading of the wet deposition was comparable to those of the dry deposition for all ring numbers.

  5. Dry Deposition of Polycyclic Aromatic Hydrocarbons (PAHs) at a Suburban Site in Beijing, China

    Science.gov (United States)

    Zhang, Xincheng; Wang, Weiyu; Zhu, Xianlei

    2017-04-01

    A great amount of polycyclic aromatic hydrocarbons (PAHs) have been generated by industrial production, waste incineration and landfill, traffic and road dust etc. They are emitted into atmosphere and afterwards enter into water body and soil through deposition, resulting in wide distribution of PAHs in environment. However, the dry deposition of PAHs from atmosphere has not been well studied, especially in the aspects of its characteristics, environmental and health effects, sources and mechanism. This study measured PAHs dry deposition in the northwest suburban area of Beijing. Dry deposition samples (i.e. dustfall samples) were collected at the sampling site located in China University of Petroleum - Beijing in 2012-2016. And PAHs in the samples were determined by GC/MS. The dry deposition flux of 16 US EPA priority PAHs (ΣPAH16) was 2.58 μg/(m^2·d), which was lower than those in other regions of North China. Its seasonal variability was more significant than annual variability (p spring > autumn > summer. The amount of ΣPAH16 removed from the atmosphere by dry deposition process accounted for only 1.2% of their emissions, indicating that the atmosphere self-purification capacity was quite limited and emission reduction measures would play a key role in controlling PAHs air pollution. However, PAHs dry deposition would deteriorate soil quality since the content of ΣPAH16 in dustfall was 1-2 orders of magnitude higher than that in soil in the same area. Dermal exposure resulting from PAHs dry deposition was not the major route. The sources of PAHs dry deposition varied with seasons. The profile and specific ratios of PAHs showed that in winter, domestic coal combustion was the main source of PAHs with the contribution up to 77%; in spring and summer, the impact of coal combustion decreased and the contribution of vehicle exhaust increased to 30% - 45%; in fall, in addition to coal combustion and vehicle exhaust, the impact of biomass burning was observed

  6. Wet and dry nitrogen deposition in the central Sichuan Basin of China

    Science.gov (United States)

    Kuang, Fuhong; Liu, Xuejun; Zhu, Bo; Shen, Jianlin; Pan, Yuepeng; Su, Minmin; Goulding, Keith

    2016-10-01

    Reactive nitrogen (Nr) plays a key role in the atmospheric environment and its deposition has induced large negative impacts on ecosystem health and services. Five-year continuous in-situ monitoring of N deposition, including wet (total nitrogen (WTN), total dissolved nitrogen (WTDN), dissolved organic nitrogen (WDON), ammonium nitrogen (WAN) and nitrate nitrogen (WNN)) and dry (DNH3, DHNO3, DpNH4+, DpNO3- and DNO2) deposition, had been conducted since August 2008 to December 2013 (wet) and May 2011 to December 2013 (dry) in Yan-ting, China, a typical agricultural area in the central Sichuan Basin. Mean annual total N deposition from 2011 to 2013 was 30.8 kg N ha-1 yr-1, and speculated that of 2009 and 2010 was averaged 28.2 kg N ha-1 yr-1, respectively. Wet and dry N deposition accounted for 76.3% and 23.7% of annual N deposition, respectively. Reduced N (WAN, DNH3 and DpNH4+) was 1.7 times of oxidized N (WNN, DHNO3, DNO2 and DpNO3-) which accounted for 50.9% and 30.3% of TN, respectively. Maximum loadings of all N forms of wet deposition, gaseous NH3, HNO3 and particulate NH4+ in dry deposition occurred in summer and minimum loadings in winter. Whether monthly, seasonal or annual averaged, dissolved N accounted for more than 70% of the total. N deposition in the central Sichuan Basin increased during the sampling period, especially that of ammonium compounds, and has become a serious threat to local aquatic ecosystems, the surrounding forest and other natural or semi-natural ecosystems in the upper reaches of the Yangtze River.

  7. Observation- and model-based estimates of particulate dry nitrogen deposition to the oceans

    Science.gov (United States)

    Baker, Alex R.; Kanakidou, Maria; Altieri, Katye E.; Daskalakis, Nikos; Okin, Gregory S.; Myriokefalitakis, Stelios; Dentener, Frank; Uematsu, Mitsuo; Sarin, Manmohan M.; Duce, Robert A.; Galloway, James N.; Keene, William C.; Singh, Arvind; Zamora, Lauren; Lamarque, Jean-Francois; Hsu, Shih-Chieh; Rohekar, Shital S.; Prospero, Joseph M.

    2017-07-01

    Anthropogenic nitrogen (N) emissions to the atmosphere have increased significantly the deposition of nitrate (NO3-) and ammonium (NH4+) to the surface waters of the open ocean, with potential impacts on marine productivity and the global carbon cycle. Global-scale understanding of the impacts of N deposition to the oceans is reliant on our ability to produce and validate models of nitrogen emission, atmospheric chemistry, transport and deposition. In this work, ˜ 2900 observations of aerosol NO3- and NH4+ concentrations, acquired from sampling aboard ships in the period 1995-2012, are used to assess the performance of modelled N concentration and deposition fields over the remote ocean. Three ocean regions (the eastern tropical North Atlantic, the northern Indian Ocean and northwest Pacific) were selected, in which the density and distribution of observational data were considered sufficient to provide effective comparison to model products. All of these study regions are affected by transport and deposition of mineral dust, which alters the deposition of N, due to uptake of nitrogen oxides (NOx) on mineral surfaces. Assessment of the impacts of atmospheric N deposition on the ocean requires atmospheric chemical transport models to report deposition fluxes; however, these fluxes cannot be measured over the ocean. Modelling studies such as the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), which only report deposition flux, are therefore very difficult to validate for dry deposition. Here, the available observational data were averaged over a 5° × 5° grid and compared to ACCMIP dry deposition fluxes (ModDep) of oxidised N (NOy) and reduced N (NHx) and to the following parameters from the Tracer Model 4 of the Environmental Chemical Processes Laboratory (TM4): ModDep for NOy, NHx and particulate NO3- and NH4+, and surface-level particulate NO3- and NH4+ concentrations. As a model ensemble, ACCMIP can be expected to be more robust than

  8. Atmospheric dry deposition in the vicinity of the Salton Sea, California - I: Air pollution and deposition in a desert environment

    Science.gov (United States)

    Alonso, R.; Bytnerowicz, A.; Boarman, W.I.

    2005-01-01

    Air pollutant concentrations and atmospheric dry deposition were monitored seasonally at the Salton Sea, southern California. Measurements of ozone (O 3), nitric acid vapor (HNO3), ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2) and sulfur dioxide (SO 2) were performed using passive samplers. Deposition rates of NO 3-, NH4+, Cl-, SO 42-, Na+, K+ and Ca2+ to creosote bush branches and nylon filters as surrogate surfaces were determined for one-week long exposure periods. Maximum O3 values were recorded in spring with 24-h average values of 108.8 ??g m-3. Concentrations of NO and NO2 were low and within ranges of the non-urban areas in California (0.4-5.6 and 3.3-16.2 ??g m-3 ranges, respectively). Concentrations of HNO3 (2.0-6.7 ??g m-3) and NH 3 (6.4-15.7 ??g m-3) were elevated and above the levels typical for remote locations in California. Deposition rates of Cl-, SO42-, Na+, K+ and Ca2+ were related to the influence of sea spray or to suspended soil particles, and no strong enrichments caused by ions originated by human activities were detected. Dry deposition rates of NO3- and NH4+ were similar to values registered in areas where symptoms of nitrogen saturation and changes in species composition have been described. Deposition of nitrogenous compounds might be contributing to eutrophication processes at the Salton Sea. ?? 2005 Elsevier Ltd. All rights reserved.

  9. An Artificial Turf-Based Surrogate Surface Collector for the Direct Measurement of Atmospheric Mercury Dry Deposition

    Directory of Open Access Journals (Sweden)

    Naima L. Hall

    2017-02-01

    Full Text Available This paper describes the development of a new artificial turf surrogate surface (ATSS sampler for use in the measurement of mercury (Hg dry deposition. In contrast to many existing surrogate surface designs, the ATSS utilizes a three-dimensional deposition surface that may more closely mimic the physical structure of many natural surfaces than traditional flat surrogate surface designs (water, filter, greased Mylar film. The ATSS has been designed to overcome several complicating factors that can impact the integrity of samples with other direct measurement approaches by providing a passive system which can be deployed for both short and extended periods of time (days to weeks, and is not contaminated by precipitation and/or invalidated by strong winds. Performance characteristics including collocated precision, in-field procedural and laboratory blanks were evaluated. The results of these performance evaluations included a mean collocated precision of 9%, low blanks (0.8 ng, high extraction efficiency (97%–103%, and a quantitative matrix spike recovery (100%.

  10. An Artificial Turf-Based Surrogate Surface Collector for the Direct Measurement of Atmospheric Mercury Dry Deposition

    Science.gov (United States)

    Hall, Naima L.; Dvonch, Joseph Timothy; Marsik, Frank J.; Barres, James A.; Landis, Matthew S.

    2017-01-01

    This paper describes the development of a new artificial turf surrogate surface (ATSS) sampler for use in the measurement of mercury (Hg) dry deposition. In contrast to many existing surrogate surface designs, the ATSS utilizes a three-dimensional deposition surface that may more closely mimic the physical structure of many natural surfaces than traditional flat surrogate surface designs (water, filter, greased Mylar film). The ATSS has been designed to overcome several complicating factors that can impact the integrity of samples with other direct measurement approaches by providing a passive system which can be deployed for both short and extended periods of time (days to weeks), and is not contaminated by precipitation and/or invalidated by strong winds. Performance characteristics including collocated precision, in-field procedural and laboratory blanks were evaluated. The results of these performance evaluations included a mean collocated precision of 9%, low blanks (0.8 ng), high extraction efficiency (97%–103%), and a quantitative matrix spike recovery (100%). PMID:28208603

  11. Comparative study of Hg xCd 1-xTe films grown on CdTe thin films previously deposited from two different techniques

    Science.gov (United States)

    Ali, A.; Abbas Shah, N.; Maqsood, A.

    2009-04-01

    High quality cadmium telluride (CdTe) thin films were grown on glass substrates with two different techniques, two evaporation source (TES) and closed space sublimation (CSS). Further to the above mercury telluride (HgTe) was then deposited by using single source on both CdTe thin films for obtaining Hg xCd 1-xTe samples. The crystalline structure of the Hg xCd 1-xTe sample grown from CSS-CdTe showed the preferential (1 1 1) orientation with smoother and larger grain size than those of TES-CdTe. The optical transmission for TES-CdTe sample was above 90% in the 1000-1500 nm range whereas it was significantly below 80% for CSS-CdTe sample. The optical transmission for TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe was ˜60%. The resistivity at room temperature of TES-CdTe and CSS-CdTe was ˜3.33×10 9 Ω cm and ˜2.20×10 8 Ω cm, respectively, while the resistivity of TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe samples was ˜1.73 Ω cm and ˜5.34×10 5 Ω cm, respectively. The comparative study of ternary compound prepared with the above techniques has been carried out for the first time.

  12. Dry and wet deposition of polycyclic aromatic hydrocarbons and comparison with typical media in urban system of Shanghai, China

    Science.gov (United States)

    Wang, Qing; Liu, Min; Li, Ye; Liu, Yankun; Li, Shuwen; Ge, Rongrong

    2016-11-01

    Polycyclic aromatic hydrocarbons (PAHs) were studied in dry and wet deposition samples collected at urban and suburban sites of Shanghai, China from April 2014 to April 2015. Average wet deposition fluxes of PAHs were higher than dry deposition (62.6 ± 41.5 vs. 26.9 ± 14.4 μg/m2/day). However, dry deposition removed more PAHs than wet deposition (69% vs. 31%) due to much shorter durations of wet deposition. The highest dry and wet deposition fluxes were in fall and winter, respectively. The highest amount of dry deposition was in fall and the highest of wet deposition was in summer. The contribution of wet deposition to total deposited PAHs in Shanghai, East China was higher than that in northern China and lower than that in southern China. The difference can be explained by both precipitation amount and removal efficiency (washout ratio). Average dry deposition velocity and washout ratio of particle-associated PAHs were 5.2 cm/s and 5.8 × 104, respectively. Four sources of deposited PAHs were unraveled by positive matrix factorization (PMF) model: traffic, coal combustion, coking and volatilization, contributing 28.7%, 24.6%, 23.7% and 23.0%, respectively. More contribution of traffic and less coal combustion and volatilization were found at urban than at suburban site. As the connection between aerosol and surface soil, deposition had a different PAH composition from those in the two sides, containing more low MW PAHs. That arose the concern that dry deposition velocity and particle washout ratio could be overestimated if coarse particulate matter was excluded from the calculation. Although deposition has been considered as the predominant pathway of PAHs to urban surface system, the PAH composition in street dust differed drastically from that in deposition. This indicated that other sources (e.g. traffic) in urban system could have a greater contribution to PAHs than it had been identified in deposition samples.

  13. Silver nanoparticles deposited on amine-functionalized silica spheres and their amalgamation-based spectral and colorimetric detection of Hg(II) ions

    Energy Technology Data Exchange (ETDEWEB)

    Rameshkumar, Perumal; Manivannan, Shanmugam; Ramaraj, Ramasamy, E-mail: ramarajr@yahoo.com [Madurai Kamaraj University, Centre for Photoelectrochemistry, School of Chemistry (India)

    2013-05-15

    A facile synthetic method to decorate amine-functionalized silica spheres (SiO{sub 2}) by silver nanoparticles (Ag NPs) is reported. The transmission electron microscopic (TEM) images showed that spherical Ag NPs with an average particle size of 14 nm were deposited on 250 nm-sized SiO{sub 2} spheres (SiO{sub 2}/Ag NPs). The spectral and colorimetric detection of Hg(II) ions were carried out using the synthesized SiO{sub 2}/Ag NPs with an experimental detection limit of 5 {mu}M. It was found that the addition of Hg(II) ions (150 {mu}M) into the solution of SiO{sub 2}/Ag NPs completely quenched the SPR band of the Ag NPs due to the formation of anisotropic Ag amalgam crystals (AgHg). The selective detection of Hg(II) ions by SiO{sub 2}/Ag NPs in the presence of other environmentally relevant metal ions was also demonstrated using spectral and colorimetric methods.Graphical abstractAmine-functionalized silica spheres are decorated by in situ formation of silver nanoparticles and their spectral and colorimetric detection of Hg(II) ions is reported.

  14. Optimized plasma-deposited fluorocarbon coating for dry release and passivation of thin SU-8 cantilevers

    DEFF Research Database (Denmark)

    Keller, Stephan Urs; Häfliger, Daniel; Boisen, Anja

    2008-01-01

    Plasma-deposited fluorocarbon coatings are introduced as a convenient method for the dry release of polymer structures. In this method, the passivation process in a deep reactive ion etch reactor was used to deposit hydrophobic fluorocarbon films. Standard photolithography with the negative epoxy......-based photoresist SU-8 was used to fabricate polymer structures such as cantilevers and membranes on top of the nonadhesive release layer. The authors identify the plasma density as the main parameter determining the surface properties of the deposited fluorocarbon films. They show that by modifying the pressure...

  15. Effect of atmospheric electricity on dry deposition of airborne particles from atmosphere

    Science.gov (United States)

    Tammet, H.; Kimmel, V.; Israelsson, S.

    The electric mechanism of dry deposition is well known in the case of unattached radon daughter clusters that are unipolar charged and of high mobility. The problematic role of the electric forces in deposition of aerosol particles is theoretically examined by comparing the fluxes of particles carried by different deposition mechanisms in a model situation. The electric mechanism of deposition appears essential for particles of diameter 10-200 nm in conditions of low wind speed. The electric flux of fine particles can be dominant on the tips of leaves and needles even in a moderate atmospheric electric field of a few hundred V m -1 measured over the plane ground surface. The electric deposition is enhanced under thunderclouds and high voltage power lines. Strong wind suppresses the relative role of the electric deposition when compared with aerodynamic deposition. When compared with diffusion deposition the electric deposition appears less uniform: the precipitation particulate matter on the tips of leaves and especially on needles of top branches of conifer trees is much more intensive than on the ground surface and electrically shielded surfaces of plants. The knowledge of deposition geometry could improve our understanding of air pollution damage to plants.

  16. Modeling of Ammonia Dry Deposition to a Pocosin Landscape Downwind of a Large Poultry Facility

    Science.gov (United States)

    A semi-empirical bi-directional flux modeling approach is used to estimate NH3 air concentrations and dry deposition fluxes to a portion of the Pocosin Lakes National Wildlife Refuge (PLNWR) downwind of a large poultry facility. Meteorological patterns at PLNWR are such that som...

  17. Measurement of the dry deposition flux of NH3 on to coniferous forest

    NARCIS (Netherlands)

    Duyzer, J.H.; Verhagen, H.L.M.; Weststrate, J.H.; Bosveld, F.C.

    1992-01-01

    The dry deposition flux of NH3 to coniferous forest was determined by the micrometeorological gradient method using a 36m high tower. Aerodynamic characteristics of the site were studied, using a second tower erected in the forest 100m from the first. Fluxes and gradients of heat and momentum measur

  18. Micrometeorological measurement of the dry deposition flux of sulphate and nitrate aerosols to coniferous forest

    NARCIS (Netherlands)

    Wyers, G.P.; Duyzer, J.H.

    1997-01-01

    Dry deposition fluxes of sulphate and nitrate have been determined over a coniferous canopy using the aerodynamic gradient technique. Vertical concentration gradients of sulphate and nitrate were measured with filters; the gradient of ammonium bisulphate was measured with thermodenuders. Filter meas

  19. Modeling of Ammonia Dry Deposition to a Pocosin Landscape Downwind of a Large Poultry Facility

    Science.gov (United States)

    A semi-empirical bi-directional flux modeling approach is used to estimate NH3 air concentrations and dry deposition fluxes to a portion of the Pocosin Lakes National Wildlife Refuge (PLNWR) downwind of a large poultry facility. Meteorological patterns at PLNWR are such that som...

  20. Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition

    DEFF Research Database (Denmark)

    Rannik, Üllar; Zhou, Luxi; Zhou, Putian;

    2016-01-01

    of 10 days in May 2013 to a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive aerosol transformation. The aim of the study was to analyze and quantify the role of aerosol and ABL dynamics in the vertical transport...... of aerosols. It was of particular interest to what extent the fluxes above the canopy deviate from the particle dry deposition on the canopy foliage due to the above-mentioned processes. The model simulations revealed that the particle concentration change due to aerosol dynamics frequently exceeded...... the effect of particle deposition by even an order of magnitude or more. The impact was, however, strongly dependent on particle size and time. In spite of the fact that the timescale of turbulent transfer inside the canopy is much smaller than the timescales of aerosol dynamics and dry deposition, leading...

  1. Atmospheric deposition of nitrogen over Czech forests: refinement of estimation of dry deposition for unmeasured nitrogen species

    Science.gov (United States)

    Hunova, Iva; Stoklasova, Petra; Kurfurst, Pavel; Vlcek, Ondrej; Schovankova, Jana

    2014-05-01

    The accurate quantification of atmospheric deposition is very important for assessment of ambient air pollution impacts on ecosystems. Our contribution presents an advanced approach to improved quantification of atmospheric deposition of nitrogen over Czech forests, merging available measured data and model results. The ambient air quality monitoring in the Czech Republic is paid an appreciable attention (Hůnová, 2001) due to the fact, that in the recent past its territory belonged to the most polluted parts of Europe (Moldan and Schnoor, 1992). The time trends and spatial patterns of atmospheric deposition were published (Hůnová et al. 2004, Hůnová et al. 2014). Nevertheless, it appears that the atmospheric deposition of nitrogen, particularly the dry deposition, is likely to be underestimated due to unavailability of data of certain nitrogen species as HNO3(g) and NH3. It is known that HNO3(g) may contribute significantly to the dry deposition of nitrogen even in regions with relatively low concentrations (Flechard et al., 2011). We attempted to substitute unmeasured nitrogen species using an Eulerian photochemical dispersion model CAMx, the Comprehensive Air Quality Model with extensions (ESSS, 2011), coupled with a high resolution regional numeric weather prediction model Aladin (Vlček, Corbet, 2011). Preliminary results for 2008 indicate that dry deposition of nitrogen, so far based on detailed monitoring of ambient NOx levels, is underestimated substantially. The dry deposition of N/NOx in 2008 reported by Ostatnická (2009) was about 0.5 g.m-2.year-1 over 99.5 % of the nation-wide area, while the contribution of unmeasured nitrogen species estimated by CAMx model were much higher. To be specific, the dry deposition of N/HNO3(g) accounted for 1.0 g.m-2.year-1, and N/NH3 for 1.6 g.m-2.year-1. In contrast, the deposition of N/HONO (g) with 0.001 g.m-2.year-1, N/PAN with 0.007 g.m-2.year-1, particulate N/NO3- with 0.002 g.m-2.year-1, and particulate N/NH4

  2. The Measurement of Dry Deposition and Surface Runoff to Quantify Urban Road Pollution in Taipei, Taiwan

    Directory of Open Access Journals (Sweden)

    Jen-Yang Lin

    2013-10-01

    Full Text Available Pollutants deposited on road surfaces and distributed in the environment are a source of nonpoint pollution. Field data are traditionally hard to collect from roads because of constant traffic. In this study, in cooperation with the traffic administration, the dry deposition on and road runoff from urban roads was measured in Taipei City and New Taipei City, Taiwan. The results showed that the dry deposition is 2.01–5.14 g/m2·day and 78–87% of these solids are in the 75–300 µm size range. The heavy metals in the dry deposited particles are mainly Fe, Zn, and Na, with average concentrations of 34,978, 1,519 and 1,502 ppm, respectively. Elevated express roads show the highest heavy metal concentrations. Not only the number of vehicles, but also the speed of the traffic should be considered as factors that influence road pollution, as high speeds may accelerate vehicle wear and deposit more heavy metals on road surfaces. In addition to dry deposition, the runoff and water quality was analyzed every five minutes during the first two hours of storm events to capture the properties of the first flush road runoff. The sample mean concentration (SMC from three roads demonstrated that the first flush runoff had a high pollution content, notably for suspended solid (SS, chemical oxygen demand (COD, oil and grease, Pb, and Zn. Regular sweeping and onsite water treatment facilities are suggested to minimize the pollution from urban roads.

  3. Source-receptor relationship of wet and dry depositions of PAHs in Northeast Asia

    Science.gov (United States)

    Inomata, Yayoi; Kajino, Mizuo; Sato, Keiichi; Kurokawa, Junichi; Tang, Ning; Ohara, Toshimasa; Hayakawa, Kazuichi; Ueda, Hiromasa

    2016-04-01

    The spatial distribution of polycyclic aromatic hydrocarbons (PAHs) deposition by the source-receptor analysis over Northeast Asia was investigated by using an Eulerian regional-scale aerosol chemical model denoted as Regional Air Quality Model 2 for Persistent Organic Pollutants (RAQM2-POP version) at the year of 2005. We confirmed that the simulation was reproduced the PAH concentrations in precipitation based on comparison with observed and simulated concentrations. In this research, the domain was divided into six-source regions (Northern China, NCHN; Central China, CCHN; South China, SCHN; eastern Russia, ERUS; South Korea, SKOR; Japan, JPN) and three-receptor regions (Yellow Sea and East China Sea, ECS; the Sea of Japan, SOJ; northwestern Pacific Ocean, NWP). We focus on benzo[a]pyrene (BaP), which is the most carcinogenic species. The largest emission occurs on CCHN, following SCHN, NCHN, ERUS, SKOR, JPN. In the three Chinese domains and ERUS, the largest contribution to the dry and wet deposition is the domestic origin. In these domains, the wet deposition amount of BaP was 2-16 times larger than those of the dry deposition amount. The total deposition (wet+dry) amount was lower than those of the emission amount. In contrast, the total depositions are larger than the emissions from their own domains in the downwind region (SKOR, JPN), indicating a signature of long-range transport of PAH to the downwind regions. The relative contributions from the three Chinese domains and ERUS to the downwind region (KOR, JPN) are evaluated. For wet deposition in winter, the relative contribution from NCHN and CCHN (20-69%) are larger, whereas the relative contribution from CCHN, SCHN, RUS (13-57%) are larger in summer. These are controlled by the distribution of precipitation. For dry deposition, the relative contribution from NCHN and CCHN (28-49%) are large in winter season, whereas the relative contribution from the three Chinese domains and ERUS are decrease in summer

  4. Assessment of dry and wet atmospheric deposits of radioactive aerosols: application to Fukushima radiocaesium fallout.

    Science.gov (United States)

    Gonze, Marc-André; Renaud, Philippe; Korsakissok, Irène; Kato, Hiroaki; Hinton, Thomas G; Mourlon, Christophe; Simon-Cornu, Marie

    2014-10-07

    The Fukushima Dai-ichi nuclear accident led to massive atmospheric deposition of radioactive substances onto the land surfaces. The spatial distribution of deposits has been estimated by Japanese authorities for gamma-emitting radionuclides through either airborne monitoring surveys (since April 2011) or in situ gamma-ray spectrometry of bare soil areas (since summer 2011). We demonstrate that significant differences exist between the two surveys for radiocaesium isotopes and that these differences can be related to dry deposits through the use of physically based relationships involving aerosol deposition velocities. The methodology, which has been applied to cesium-134 and cesium-137 deposits within 80-km of the nuclear site, provides reasonable spatial estimations of dry and wet deposits that are discussed and compared to atmospheric numerical simulations from the Japanese Atomic Energy Agency and the French Institute of Radioprotection and Nuclear Safety. As a complementary approach to numerical simulations, this field-based analysis has the possibility to contribute information that can be applied to the understanding and assessment of dose impacts to human populations and the environment around Fukushima.

  5. Enhanced dry deposition of nitrogen pollution near coastlines: A case study covering the Chesapeake Bay estuary and Atlantic Ocean coastline

    Science.gov (United States)

    Loughner, Christopher P.; Tzortziou, Maria; Shroder, Shulamit; Pickering, Kenneth E.

    2016-12-01

    Atmospheric deposition of nitrogen pollution is one of the major sources of nitrogen to many terrestrial and aquatic ecosystems, worldwide. This modeling study suggests that coastlines frequently experience disproportionally high dry deposition of reactive nitrogen. High concentrations of air pollution from coastal cities often accumulate over adjacent estuaries and coastal waters due to low dry deposition rates over the water and a shallow marine boundary layer trapping marine emissions. As high concentrations of pollutants over the water are transported inland, enhanced dry deposition occurs onshore along the coastlines. Large spatial gradients in air pollutants and deposition totals are simulated along the coastline with decreasing concentrations/deposition as the distance from the water increases. As pollutants are transported onshore, air pollution mixing ratios near the surface decrease due to removal by dry deposition, vertical dilution due to deeper mixing layer heights, and decrease in friction velocity as a function of distance inland from the coastline. Ammonium nitrate formation near agricultural ammonia sources, sodium nitrate formation near coastal areas with atmospheric sea-salt loadings, and particulate growth via water uptake also contribute to large nitrate dry deposition totals at the coastline. Gradients in dry N deposition are evident over a monthly time scale and are enhanced during sea and bay breeze events. Current existing N-deposition monitoring networks do not capture the large spatial gradients of ammonium, nitrate, and nitric acid concentrations near coastlines predicted by the model due to the coarse spatial density distribution of monitoring sites.

  6. Wet and dry atmospheric depositions of inorganic nitrogen during plant growing season in the coastal zone of Yellow River Delta.

    Science.gov (United States)

    Yu, Junbao; Ning, Kai; Li, Yunzhao; Du, Siyao; Han, Guangxuan; Xing, Qinghui; Wu, Huifeng; Wang, Guangmei; Gao, Yongjun

    2014-01-01

    The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD) using automatic sampling equipment. The results showed that SO4 (2-) and Na(+) were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m(-2), in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3 (-)-N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4 (+)-N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3 (-)-N and NH4 (+)-N was ~31.38% and ~20.50% for the contents of NO3 (-)-N and NH4 (+)-N in 0-10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD.

  7. Silver nanoparticles deposited on amine-functionalized silica spheres and their amalgamation-based spectral and colorimetric detection of Hg(II) ions

    Science.gov (United States)

    Rameshkumar, Perumal; Manivannan, Shanmugam; Ramaraj, Ramasamy

    2013-05-01

    A facile synthetic method to decorate amine-functionalized silica spheres (SiO2) by silver nanoparticles (Ag NPs) is reported. The transmission electron microscopic (TEM) images showed that spherical Ag NPs with an average particle size of 14 nm were deposited on 250 nm-sized SiO2 spheres (SiO2/Ag NPs). The spectral and colorimetric detection of Hg(II) ions were carried out using the synthesized SiO2/Ag NPs with an experimental detection limit of 5 μM. It was found that the addition of Hg(II) ions (150 μM) into the solution of SiO2/Ag NPs completely quenched the SPR band of the Ag NPs due to the formation of anisotropic Ag amalgam crystals (AgHg). The selective detection of Hg(II) ions by SiO2/Ag NPs in the presence of other environmentally relevant metal ions was also demonstrated using spectral and colorimetric methods.

  8. The sources of trace element pollution of dry depositions nearby a drinking water source.

    Science.gov (United States)

    Guo, Xinyue; Ji, Hongbing; Li, Cai; Gao, Yang; Ding, Huaijian; Tang, Lei; Feng, Jinguo

    2017-02-01

    Miyun Reservoir is one of the most important drinking water sources for Beijing. Thirteen atmospheric PM sampling sites were established around this reservoir to analyze the mineral composition, morphological characteristics, element concentration, and sources of atmospheric PM pollution, using transmission electron microscope, X-ray diffraction, and inductively coupled plasma mass spectrometry analyses. The average monthly dry deposition flux of aerosols was 15.18 g/m(2), with a range of 5.78-47.56 g/m(2). The maximum flux season was winter, followed by summer, autumn, and spring. Zn and Pb pollution in this area was serious, and some of the sample sites had Cr, Co, Ni, and Cu pollution. Deposition fluxes of Zn/Pb in winter and summer reached 99.77/143.63 and 17.04/33.23 g/(hm(2) month), respectively. Principal component analysis showed two main components in the dry deposition; the first was Cr, Co, Ni, Cu, and Zn, and the other was Pb and Cd. Principal sources of the trace elements were iron mining and other anthropogenic activities in the surrounding areas and mountainous area north of the reservoir. Mineralogy analysis and microscopic conformation results showed many iron minerals and some unweathered minerals in dry deposition and atmospheric particulate matter, which came from an iron ore yard in the northern mountainous area of Miyun County. There was possible iron-rich dry deposition into Miyun Reservoir, affecting its water quality and harming the health of people living in areas around the reservoir and Beijing.

  9. Evaluating the relationship between wildfire extent and nitrogen dry deposition in a boreal forest in interior Alaska

    Science.gov (United States)

    Nagano, Hirohiko; Iwata, Hiroki

    2017-03-01

    Alaska wildfires may play an important role in nitrogen (N) dry deposition in Alaskan boreal forests. Here we used annual N dry deposition data measured by CASTNET at Denali National Park (DEN417) during 1999-2013, to evaluate the relationships between wildfire extent and N dry deposition in Alaska. We established six potential factors for multiple regression analysis, including burned area within 100 km of DEN417 (BA100km) and in other distant parts of Alaska (BAAK), the sum of indexes of North Atlantic Oscillation and Arctic Oscillation (OI), number of days with negative OI (OIday), precipitation (PRCP), and number of days with PRCP (PRCPday). Multiple regression analysis was conducted for both time scales, annual (using only annual values of factors) and six-month (using annual values of BAAK and BA100km, and fire and non-fire seasons' values of other four factors) time scales. Together, BAAK, BA100km, and OIday, along with PRCPday in the case of the six-month scale, explained more than 92% of the interannual variation in N dry deposition. The influence of BA100km on N dry deposition was ten-fold greater than from BAAK; the qualitative contribution was almost zero, however, due to the small BA100km. BAAK was the leading explanatory factor, with a 15 ± 14% contribution. We further calculated N dry deposition during 1950-2013 using the obtained regression equation and long-term records for the factors. The N dry deposition calculated for 1950-2013 revealed that an increased occurrence of wildfires during the 2000s led to the maximum N dry deposition exhibited during this decade. As a result, the effect of BAAK on N dry deposition remains sufficiently large, even when large possible uncertainties (>40%) in the measurement of N dry deposition are taken into account for the multiple regression analysis.

  10. Erosion and deposition in depth-averaged models of dense, dry, inclined, granular flows

    Science.gov (United States)

    Jenkins, James T.; Berzi, Diego

    2016-11-01

    We derive expressions for the rates of erosion and deposition at the interface between a dense, dry, inclined granular flow and an erodible bed. In obtaining these, we assume that the interface between the flowing grains and the bed moves with the speed of a pressure wave in the flow, for deposition, or with the speed of a disturbance through the contacting particles in the bed, for erosion. We employ the expressions for the rates of erosion and deposition to show that after an abrupt change in the angle of inclination of the bed the characteristic time for the motion of the interface is much shorter than the characteristic time of the flow. This eliminates the need for introducing models of erosion and deposition rate in the mass balance; and the instantaneous value of the particle flux is the same function of the instantaneous value of the flow depth as in a steady, uniform flow.

  11. Measurements of ammonia concentrations, fluxes and dry deposition velocities to a spruce forest 1991-1995

    DEFF Research Database (Denmark)

    Andersen, H.V.; Hovmand, M.F.; Hummelshøj, P.;

    1999-01-01

    at conditions with easterly winds, the air have passed central Jutland with large emission areas. Some of the relatively low deposition velocities or emissions were observed during conditions with low ammonia concentration and westerly winds. These observations might relate to a compensation point of the forest...... measuring period characterized by easterly winds with dry conditions and high ammonia concentrations, and the emissions might relate to evaporation from ammonia saturated surfaces or emission from mineralization in the forest soil. In general, relatively high net deposition velocities were observed during...

  12. Pharmaceutical aerosols deposition patterns from a Dry Powder Inhaler: Euler Lagrangian prediction and validation.

    Science.gov (United States)

    Ravi Kannan, Ravishekar; Przekwas, A J; Singh, Narender; Delvadia, Renishkumar; Tian, Geng; Walenga, Ross

    2017-04-01

    This study uses Computational Fluid Dynamics (CFD) to predict, analyze and validate the deposition patterns in a human lung for a Budesonide drug delivered from the Novolizer Dry Powder Inhaler device. We used a test case of known deposition patterns to validate our computational Euler Lagrangian-based deposition predictions. Two different lung models are used: (i) a basic ring-less trachea model and (ii) an advanced Human Zygote5 model. Unlike earlier attempts, the current simulations do not include the device in the computational domain. This greatly reduces the computational effort. To mimic the device, we model the inlet particle jet stream from the device as a spray entering the mouth in a conical fashion. Deposition studies in the various lung regions were performed. We were able to computationally predict and then demonstrate the enhanced deposition in the tracheal and first generation rings/ridges. The enhanced vorticity creation due to the ring structure and the geometrical design contributes to larger deposition in the Zygote5 model. These are in accord with existing data, unlike the ring-less model. Our validated results indicate the need to (i) introduce the ridges in the experimental casts and the CFD surface meshes to be anatomically consistent and obtain physiologically consistent depositions; (ii) introduce a factor to account for the recirculating lighter particles in empirical models.

  13. Lung deposition of salbutamol in healthy human subjects from the MAGhaler dry powder inhaler.

    Science.gov (United States)

    Newman, S; Malik, S; Hirst, R; Pitcairn, G; Heide, A; Pabst, J; Dinkelaker, A; Fleischer, W

    2002-12-01

    The MAGhaler (Mundipharma GmbH) is a multidose dry powder inhaler (DPI) containing a novel formulation of drug and lactose compacted by an isostatic pressing technique (GGU GmbH). On actuation, a precise dose is metered from a compacted ring-shaped drug tablet. In this study, the lung deposition of salbutamol from this device has been assessed. Ten healthy non-smoking subjects completed a two-way cross-over study assessing the pulmonary deposition of salbutamol (200 microg) from the MAGhaler at high (60 l/min) and low (30 l/min) peak inhaled flow rates (PIFRs), representing maximal and sub-maximal inspiratory efforts. The formulation was radiolabelled with 99mTc, and lung and oropharyngeal depositions were quantified by gamma scintigraphyThe mean (SD)% ofthe delivered dose deposited in the lungs was 26.4 (4.3)% at 60 l/min and 21.1 (5.1)% at 30 l/min (P < 0.05), corresponding to mean lung depositions of 52.8 and 42.2 microg salbutamol, respectively. The distribution of drug within different lung regions did not vary significantly with inhaled flow rate. The data provided proof of concept for the novel inhaler device and the innovative drug formulation. In comparison with previous deposition data obtained with other DPIs, the lung deposition was relatively high, relatively reproducible (coefficient of variation 16% at 60 l/min) and relatively insensitive to the change in peak inhaled flow rate.

  14. Atmospheric dry deposition of trace elements measured around the urban and industrially impacted NY-NJ harbor

    Science.gov (United States)

    Yi, Seung-Muk; Totten, Lisa A.; Thota, Sathyapriya; Yan, Shu; Offenberg, John H.; Eisenreich, Steven J.; Graney, Joseph; Holsen, Thomas M.

    Long-term direct trace metal dry deposition measurements were made during 2001 and 2002 at two sites near the NY/NJ Harbor Estuary in New Jersey: Jersey City (JC) and New Brunswick (NB). In addition intensive dry deposition and atmospheric size distribution (ASD) measurements were made between September 2001 and June 2002. Dry deposition samples were obtained using modified MIC-B wet deposition samplers which deployed knife-edge surrogate surfaces during dry periods. ASDs were measured with micro-orifice uniform deposit impactors (MOUDI) and coarse particle rotary impactors (CPRI). The fluxes of trace metals were found to be highest at the JC site and lowest at the NB site. The dry deposition fluxes ranged from 0.030 (Cd) to 3800 (Al) μg m -2 d -1 and 0.14 (Cd) to 8100 (Al) μg m -2 d -1at NB and JC sites, respectively. Metals of crustal origin were found mostly in the coarse particle fraction and anthropogenic metals were found mostly in the fine particle fraction. For the intensive experiments, overall dry deposition velocities of several trace metals were determined by dividing measured fluxes by measured concentrations in different particle size ranges. For most of the elements, the flux was highly correlated with PM 10 and coarse particle concentrations. The overall dry deposition velocities of crustal elements (Al and Mg) varied from 3.7 to 8.7 cm s -1 with correlation coefficients ranging from 0.50 to 0.84. The best-fit dry deposition velocities for anthropogenic elements (Cr, Mn, Zn, and Pb; Cu, Mo, and Ba; V and Ni) varied more than those for crustal elements (0.52-25 vs. 3.7-8.7 cm s -1). The dry deposition velocities for most elements obtained using three size ranges were statistically significant with R2 values ranging from 0.37 to 0.84 except for V and Ni (0.12).

  15. Influence of agricultural biomass burning on aerosol size distribution and dry deposition in southeastern Brazil.

    Science.gov (United States)

    Rocha, Gisele O; Allen, Andrew G; Cardoso, Arnaldo A

    2005-07-15

    The size distributed composition of ambient aerosols is used to explore seasonal differences in particle chemistry and to show that dry deposition fluxes of soluble species, including important plant nutrients, increase during periods of biomass (sugar cane trash) burning in São Paulo State, Brazil. Measurements were made at a single site centrally located in the State's sugar cane growing region but away from the immediate vicinity of burns, so that the airsampled was representative of the regional background. Calculation of ion equivalent balances showed that during burning periods smaller particles (Aitken and accumulation modes) were more acidic, containing higher concentrations of SO4(2-), oxalate, NO3-, HCOO-, CH3COO-, and CI-, but insufficient NH4+ and K+ to achieve neutrality. Larger particles showed an anion deficit due to the presence of unmeasured ions and comprised resuspended dusts modified by accumulation of nitrate, chloride, and organic anions. Increases of resuspended particles during the burning season were attributed to release of earlier deposits from the surfaces of burning vegetation as well as increased vehicle movement on unsurfaced roads. During winter months the relative contribution of combined emissions from road transport and industry diminished due to increased emissions from biomass combustion and other activities specifically associated with the harvest period. Positive increments in annual particulate dry deposition fluxes due to higher fluxes during the sugar cane harvest were 44.3% (NH4+), 42.1% (K+), 31.8% (Mg2+), 30.4% (HCOO-), 12.8% (CI-), 6.6% (CH3COO-), 5.2% (Ca2+), 3.8% (SO4(2-)), and 2.3% (NO3-). Na+ and oxalate fluxes were seasonally invariant. Annual aerosol dry deposition fluxes (kg ha(-1)) were 0.5 (Na+), 0.25 (NH4+), 0.39 (K+), 0.51 (Mg2+), 3.19 (Ca2+), 1.34 (Cl-), 4.47 (NO3-), 3.59 (SO4(2-)), 0.58 (oxalate), 0.71 (HCOO-), and 1.38 (CH3COO-). Contributions of this mechanism to combined aerosol dry deposition and

  16. Drying, phase separation, and deposition in droplets of sunset yellow chromonic liquid crystal

    Science.gov (United States)

    Gross, Adam; Davidson, Zoey S.; Huang, Yongyang; Still, Tim; Zhou, Chao; Yodh, A. G.

    We investigate the drying process and the final deposition patterns of multi-phase sessile droplets containing aqueous lyotropic chromonic liquid crystal (LC). The experiments employ a variety of optical techniques including profilometry, polarization optical microscopy and optical coherence microscopy. An unusual hierarchical LC assembly is observed during drying; in particular, LC mesogens are first formed at the start of drying and then compartments of isotropic, nematic and columnar phases arise. Nonuniform evaporation creates concentration gradients in droplets such that LC phases emerge from the outer edge of the drop and advance to the center over the course of drying. Distinct outward flows associated with the ``coffee-ring effect'' are seen initially, but the assembly of the mesogens creates viscosity, density, and surface tension gradients that effectively introduce new convective flows and complex LC phase boundaries within the drop. Finally, we show that the final deposit shape of chromonic materials changes with rate of evaporation. We gratefully acknowledge financial support through NSF DMR12-05463, MRSEC DMR11-20901, NASA NNX08AO0G, and NSF DBI-1455613.

  17. Observation- and model-based estimates of particulate dry nitrogen deposition to the oceans

    Directory of Open Access Journals (Sweden)

    A. R. Baker

    2017-07-01

    Full Text Available Anthropogenic nitrogen (N emissions to the atmosphere have increased significantly the deposition of nitrate (NO3− and ammonium (NH4+ to the surface waters of the open ocean, with potential impacts on marine productivity and the global carbon cycle. Global-scale understanding of the impacts of N deposition to the oceans is reliant on our ability to produce and validate models of nitrogen emission, atmospheric chemistry, transport and deposition. In this work,  ∼  2900 observations of aerosol NO3− and NH4+ concentrations, acquired from sampling aboard ships in the period 1995–2012, are used to assess the performance of modelled N concentration and deposition fields over the remote ocean. Three ocean regions (the eastern tropical North Atlantic, the northern Indian Ocean and northwest Pacific were selected, in which the density and distribution of observational data were considered sufficient to provide effective comparison to model products. All of these study regions are affected by transport and deposition of mineral dust, which alters the deposition of N, due to uptake of nitrogen oxides (NOx on mineral surfaces. Assessment of the impacts of atmospheric N deposition on the ocean requires atmospheric chemical transport models to report deposition fluxes; however, these fluxes cannot be measured over the ocean. Modelling studies such as the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP, which only report deposition flux, are therefore very difficult to validate for dry deposition. Here, the available observational data were averaged over a 5° × 5° grid and compared to ACCMIP dry deposition fluxes (ModDep of oxidised N (NOy and reduced N (NHx and to the following parameters from the Tracer Model 4 of the Environmental Chemical Processes Laboratory (TM4: ModDep for NOy, NHx and particulate NO3− and NH4+, and surface-level particulate NO3− and NH4+ concentrations. As a model ensemble, ACCMIP can be

  18. Mercury cadmium telluride (HgCdTe) passivation by advanced thin conformal Al2O3 films

    Science.gov (United States)

    Fu, Richard; Pattison, James; Chen, Andrew; Nayfeh, Osama

    2012-06-01

    HgCdTe passivation process must be performed at low temperature in order to reduce Hg depletion. Low temperature plasma enhanced atomic layer deposition (PE-ALD) is an emerging deposition technology for thin highly conformal films to meet the demand. Room temperature PE-ALD Al2O3 film's passivation on HgCdTe has been studied. Conformal film was investigated through SEM images of the Al2O3 film deposited onto high aspect ratio features dry etched into HgCdTe. Minority carrier lifetime was measured and compared by photoconductive decay transients of HgCdTe before and after deposition. Room temperature ALD Al2O3 film increased the minority carrier lifetime of HgCdTe.

  19. Combined effects of iron and copper from atmospheric dry deposition on ocean productivity

    Science.gov (United States)

    Wang, F. J.; Chen, Y.; Guo, Z. G.; Gao, H. W.; Mackey, K. R.; Yao, X. H.; Zhuang, G. S.; Paytan, A.

    2017-03-01

    Atmospheric deposition can provide nutrients and potential toxicants to marine ecosystem, hence affecting ocean net primary productivity (NPP). Nonetheless, the interactive effects of mixed aerosol components on phytoplankton have rarely been reported. Here we explored the combined effects of iron (Fe) and copper (Cu) on NPP over the East China Sea. In aerosol addition mesocosm experiments, phytoplankton growth was suppressed under high aerosol Cu but was increased when high Cu was accompanied by high Fe in aerosols. A time series of soluble aerosol Fe and Cu deposition was obtained and compared to regional chlorophyll a (Chl a) abundances from Moderate Resolution Imaging Spectroradiometer/Aqua. Strong positive correlations were observed between the dry flux ratios of soluble Fe/Cu and Chl a abundances in the large offshore area, whereas these variables were uncoupled in coastal regions where riverine input and upwelling dominated the biogeochemistry. Current work provides insight into the complex linkage between atmospheric deposition and marine productivity.

  20. Aerosol dry deposition on vegetative canopies. Part II: A new modelling approach and applications

    Science.gov (United States)

    Petroff, Alexandre; Mailliat, Alain; Amielh, Muriel; Anselmet, Fabien

    2008-05-01

    This paper presents a new approach for the modelling of aerosol dry deposition on vegetation. It follows a companion article, in which a review of the current knowledge highlights the need for a better description of the aerosol behaviour within the canopy [Petroff, A., Mailliat, A., Amielh, M., Anselmet, F., 2008. Aerosol dry deposition on vegetative canopies. Part I: Review of present knowledge. Atmospheric Environment, in press, doi:10.1016/j.atmosenv.2007.09.043]. Concepts from multi-phase flow studies are used for describing the canopy medium and deriving a time and space-averaged aerosol balance equation and the associated deposition terms. The closure of the deposition terms follows an up-scaling procedure based on the statistical distribution of the collecting elements. This aerosol transport model is then applied in a stationary and mono-dimensional configuration and takes into account the properties of the vegetation, the aerosol and the turbulent flow. Deposition mechanisms are Brownian diffusion, interception, inertial and turbulent impactions, and gravitational settling. For each of them, a parameterisation of the particle collection is derived and the quality of their predictions is assessed by comparison with wind-tunnel deposition measurements on coniferous twigs [Belot, Y., Gauthier, D., 1975. Transport of micronic particles from atmosphere to foliar surfaces. In: De Vries, D.A., Afgan, N.H. (Eds.), Heat and Mass Transfer in the Biosphere. Scripta Book, Washington, DC, pp. 583-591; Belot, Y., 1977. Etude de la captation des polluants atmosphériques par les végétaux. CEA, R-4786, Fontenay-aux-Roses; Belot, Y., Camus, H., Gauthier, D., Caput, C., 1994. Uptake of small particles by canopies. The Science of the Total Environment 157, 1-6]. Under a real canopy configuration, the predictions of the aerosol transport model compare reasonably well with detailed on-site deposition measurements of Aitken mode particles [Buzorius, G., Rannik, Ü., M

  1. Impact of future land cover changes on HNO3 and O3 surface dry deposition

    Directory of Open Access Journals (Sweden)

    T. Verbeke

    2015-07-01

    Full Text Available Dry deposition is a key component of surface–atmosphere exchange of compounds, acting as a sink for several chemical species. Meteorological factors, chemical properties of the trace gas considered and land surface properties are strong drivers of dry deposition efficiency and variability. Under both climatic and anthropogenic pressure, the vegetation distribution over the Earth has been changing a lot over the past centuries, and could be significantly altered in the future. In this study, we perform a modeling investigation of the potential impact of land-cover changes between present-day (2006 and the future (2050 on dry deposition rates, with special interest for ozone (O3 and nitric acid vapor (HNO3, two compounds which are characterized by very different physico-chemical properties. The 3-D chemistry transport model LMDz-INCA is used, considering changes in vegetation distribution based on the three future projections RCPs 2.6, 4.5 and 8.5. The 2050 RCP 8.5 vegetation distribution leads to a rise up to 7 % (+0.02 cm s−1 in VdO3 and a decrease of −0.06 cm s−1 in VdHNO3 relative to the present day values in tropical Africa, and up to +18 and −15 % respectively in Australia. When taking into account the RCP 4.5 scenario, which shows dramatic land cover change in Eurasia, VdHNO3 increases by up to 20 % (annual-mean value and reduces VdO3 by the same magnitude in this region. When analyzing the impact of dry deposition change on atmospheric chemical composition, our model calculates that the effect is lower than 1 ppb on annual mean surface ozone concentration, for both for the RCP8.5 and RCP2.6 scenarios. The impact on HNO3 surface concentrations is more disparate between the two scenarios, regarding the spatial repartition of effects. In the case of the RCP 4.5 scenario, a significant increase of the surface O3 concentration reaching locally up to 5 ppb (+5 % is calculated on average during the June–August period. This scenario

  2. Characteristics Of Atmospheric Dry Deposition Of Metals To The Region Of Lake Asan And Sapgyo, Korea

    Science.gov (United States)

    Han, J.; Shin, H.; Lee, M.; Lim, Y.; Seo, M.; Jung, I.

    2008-12-01

    Environment includes a multi-media such as air, surface water, soil, underground water and ecosystem. Some pollutants transfer among a multi-media, posing serious threat to humans, animals and plants. Pollutants released into the environment remain for long times and transport long distances while going through physical and chemical interactions such as transports between multi-media ; air, water and soil, deposition, and absorption and release from organisms. This study assessed the amount of heavy metals transferred from air to water and soil using dry deposition plate and water surface sampler during spring (June 13 ~ 21, 2007) and winter (October 23 ~ 30 in 2007) at 9 locations including Dangjin, Pyeongtaek and Asan. Micro-Orifice Uniform Deposit Impactor, MOUDI was used to confirm the size distribution. The measured heavy metal deposition flux was compared with the expectation obtained with deposition model. In addition, amount of heavy metal deposition at Asan and Sapgyo lakes were evaluated to verify the water pollution state driven by atmospheric deposition. Atmospheric dry deposition flux of metals are 133.92 microgram m-2 day-1, 44.01 microgram m-2 day-1, 0.915 microgram m-2 day-1, and 0.175 microgram m-2 day-1 during spring, and 72.86 microgram m-2 day- 1, 88.14 microgram m-2 day-1, 0.991 microgram m-2 day-1, and 0.189 microgram m-2 day-1 during fall, for lead, nickel, arsenic, and cadmium, respectively. It is required to re- calculation the dry deposition flux by land use type due to possibility of underestimating the flux in case of using grease surrogate surface having low surface roughness. The cadmium, lead, and arsenic size distribution was mono-modal with the peaks in the 0.65 ~ 1.1 micrometer size range in the fine mode showing sharp peak in the condensation submode especially for cadmium and lead because of effect of primary emission. The nickel size distribution was bimodal, a typical size distribution for an urban atmosphere, showing sharp

  3. Dry deposition of gaseous radioiodine and particulate radiocaesium onto leafy vegetables

    Energy Technology Data Exchange (ETDEWEB)

    Tschiersch, Jochen, E-mail: tschiersch@helmholtz-muenchen.de [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg (Germany); Shinonaga, Taeko [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstaedter Landstr. 1, 85764 Neuherberg (Germany); Heuberger, Heidi [TU Muenchen, Center of Life and Food Sciences Weihenstephan, Duernast 2, 85350 Freising (Germany)

    2009-10-15

    Radionuclides released to the atmosphere during dry weather (e.g. after a nuclear accident) may contaminate vegetable foods and cause exposure to humans via the food chain. To obtain experimental data for an appropriate assessment of this exposure path, dry deposition of radionuclides to leafy vegetables was studied under homogeneous and controlled greenhouse conditions. Gaseous {sup 131}I-tracer in predominant elemental form and particulate {sup 134}Cs-tracer at about 1 {mu}m diameter were used to identify susceptible vegetable species with regard to contamination by these radionuclides. The persistence was examined by washing the harvested product with water. The vegetables tested were spinach (Spinacia oleracea), butterhead lettuce (Lactuca sativa var. capitata), endive (Cichorium endivia), leaf lettuce (Lactuca sativa var. crispa), curly kale (Brassica oleracea convar. acephala) and white cabbage (Brassica oleracea convar. capitata). The variation of radionuclides deposited onto each vegetable was evaluated statistically using the non-parametric Kruskal-Wallis Test and the U-test of Mann-Whitney. Significant differences in deposited {sup 131}I and {sup 134}Cs activity concentration were found among the vegetable species. For {sup 131}I, the deposition velocity to spinach normalized to the biomass of the vegetation was 0.5-0.9 cm{sup 3} g{sup -1} s{sup -1} which was the highest among all species. The particulate {sup 134}Cs deposition velocity of 0.09 cm{sup 3} g{sup -1} s{sup -1} was the highest for curly kale, which has rough and structured leaves. The lowest deposition velocity was onto white cabbage: 0.02 cm{sup 3} g{sup -1} s{sup -1} (iodine) and 0.003 cm{sup 3} g{sup -1} s{sup -1} (caesium). For all species, the gaseous iodine deposition was significantly higher compared to the particulate caesium deposition. The deposition depends on the sensitive parameters leaf area, stomatal aperture, and plant morphology. Decontamination by washing with water was very

  4. Climate sensitivity of gaseous elemental mercury dry deposition to plants: impacts of temperature, light intensity, and plant species.

    Science.gov (United States)

    Rutter, Andrew P; Schauer, James J; Shafer, Martin M; Creswell, Joel; Olson, Michael R; Clary, Alois; Robinson, Michael; Parman, Andrew M; Katzman, Tanya L

    2011-01-15

    Foliar accumulations of gaseous elemental mercury (GEM) were measured in three plant species between nominal temperatures of 10 and 30 °C and nominal irradiances of 0, 80, and 170 W m(-2) (300 nm-700 nm) in a 19 m(3) controlled environment chamber. The plants exposed were as follows: White Ash (Fraxinus americana; WA); White Spruce (Picea glauca; WS); and Kentucky Bluegrass (Poa partensis; KYBG). Foliar enrichments in the mercury stable isotope ((198)Hg) were used to measure mercury accumulation. Exposures lasted for 1 day after which the leaves were digested in hot acid and the extracted mercury was analyzed with ICPMS. Resistances to accumulative uptake by leaves were observed to be dependent on both light and temperature, reaching minima at optimal growing conditions (20 °C; 170 W m(-2) irradiance between 300-700 nm). Resistances typically increased at lower (10 °C) and higher (30 °C) temperatures and decreased with higher intensities of irradiance. Published models were modified and used to interpret the trends in stomatal and leaf interior resistances to GEM observed in WA. The model captured the experimental trends well and revealed that stomatal and internal resistances were both important across much of the temperature range. At high temperatures, however, stomatal resistance dominated due to increased water vapor pressure deficits. The resistances measured in this study were used to model foliar accumulations of GEM at a northern US deciduous forest using atmospheric mercury and climate measurements made over the 2003 growing season. The results were compared to modeled accumulations for GEM, RGM, and PHg using published deposition velocities. Predictions of foliar GEM accumulation were observed to be a factor of 5-10 lower when the temperature and irradiance dependent resistances determined in this study were used in place of previously published data. GEM uptake by leaves over the growing season was shown to be an important deposition pathway (2

  5. A corrected formulation of the Multilayer Model (MLM) for inferring gaseous dry deposition to vegetated surfaces

    Science.gov (United States)

    Saylor, Rick D.; Wolfe, Glenn M.; Meyers, Tilden P.; Hicks, Bruce B.

    2014-08-01

    The Multilayer Model (MLM) has been used for many years to infer dry deposition fluxes from measured trace species concentrations and standard meteorological measurements for national networks in the U.S., including the U.S. Environmental Protection Agency's Clean Air Status and Trends Network (CASTNet). MLM utilizes a resistance analogy to calculate deposition velocities appropriate for whole vegetative canopies, while employing a multilayer integration to account for vertically varying meteorology, canopy morphology and radiative transfer within the canopy. However, the MLM formulation, as it was originally presented and as it has been subsequently employed, contains a non-physical representation related to the leaf-level quasi-laminar boundary layer resistance that affects the calculation of the total canopy resistance. In this note, the non-physical representation of the canopy resistance as originally formulated in MLM is discussed and a revised, physically consistent, formulation is suggested as a replacement. The revised canopy resistance formulation reduces estimates of HNO3 deposition velocities by as much as 38% during mid-day as compared to values generated by the original formulation. Inferred deposition velocities for SO2 and O3 are not significantly altered by the change in formulation (<3%). Inferred deposition loadings of oxidized and total nitrogen from CASTNet data may be reduced by 10-20% and 5-10%, respectively, for the Eastern U. S. when employing the revised formulation of MLM as compared to the original formulation.

  6. A Corrected Formulation of the Multilayer Model (MLM) for Inferring Gaseous Dry Deposition to Vegetated Surfaces

    Science.gov (United States)

    Saylor, Rick D.; Wolfe, Glenn M.; Meyers, Tilden P.; Hicks, Bruce B.

    2014-01-01

    The Multilayer Model (MLM) has been used for many years to infer dry deposition fluxes from measured trace species concentrations and standard meteorological measurements for national networks in the U.S., including the U.S. Environmental Protection Agency's Clean Air Status and Trends Network (CASTNet). MLM utilizes a resistance analogy to calculate deposition velocities appropriate for whole vegetative canopies, while employing a multilayer integration to account for vertically varying meteorology, canopy morphology and radiative transfer within the canopy. However, the MLM formulation, as it was originally presented and as it has been subsequently employed, contains a non-physical representation related to the leaf-level quasi-laminar boundary layer resistance that affects the calculation of the total canopy resistance. In this note, the non-physical representation of the canopy resistance as originally formulated in MLM is discussed and a revised, physically consistent, formulation is suggested as a replacement. The revised canopy resistance formulation reduces estimates of HNO3 deposition velocities by as much as 38% during mid-day as compared to values generated by the original formulation. Inferred deposition velocities for SO2 and O3 are not significantly altered by the change in formulation (less than 3%). Inferred deposition loadings of oxidized and total nitrogen from CASTNet data may be reduced by 10-20% and 5-10%, respectively, for the Eastern U. S. when employing the revised formulation of MLM as compared to the original formulation.

  7. Dry deposition profile of small particles within a model spruce canopy

    Energy Technology Data Exchange (ETDEWEB)

    Ould-Dada, Zitouni [Centre for Analytical Research in the Environment, (now EAS T.H. Huxley School), Imperial College of Science Technology and Medicine, Silwood Park, Ascot, SL57TE Berkshire (United Kingdom)

    2002-03-08

    Data on dry deposition of 0.82 {mu}m MMAD uranium particles to a small scale, 'model' Norway spruce (Picea abies) canopy have been determined by means of wind tunnel experiments. These are presented for both the total canopy and for five horizontal layers within the canopy. The results show a complex pattern of deposition within the canopy. The highest deposition velocity V{sub g} (0.19 cm s{sup -1}) was recorded for the topmost layer within the canopy (i.e. the layer in direct contact with the boundary layer) whereas the lowest V{sub g} (0.02 cm s{sup -1}) occurred at the soil surface. Vertical penetration of depositing aerosol through the canopy was influenced by variations in biomass, wind velocity and turbulence within the canopy. A total canopy V{sub g} of 0.5 cm s{sup -1} was obtained and this is in line with field measurements of V{sub g} reported in literature for both anthropogenic and radionuclide aerosols of similar size ranges. Extrapolation of wind tunnel data to 'real' forest canopies is discussed. The information presented here is of importance in predicting the likely contribution of dry deposition of aerosols to pollutant inputs to forest ecosystems, particularly in the context of radioactive aerosol releases from nuclear installations. The application of the present data may also be appropriate for other pollutant aerosols such as SO{sub 4}, NO{sub 3} and NH{sub 4}, which are characterised by particle sizes in the range used in this study.

  8. Emission characters of particulate concentrations and dry deposition studies for incense burning at a Taiwanese temple.

    Science.gov (United States)

    Fang, Guor-Cheng; Chu, Chia-Chium; Wu, Yuh-Shen; Fu, Peter Pi-Cheng

    2002-05-01

    Suspended particulate concentrations were measured at the Tzu Yun Yen temple in the Taichung region of Taiwan. The temple performs traditional incense burning. A universal sampler and a micro-orifice uniform deposited impactor (MOUDI) sampler with a dry deposition plate were used to measure the particulate concentrations. The results show that the average PM2.5/PM10 ratio was 74% during the incense burning period at this temple. In addition, the average suspended particulate (PM10) element concentration of anthropogenic element Zn (495 ng/m3) was higher than the other anthropogenic elements (Pb, Mn, Ni, and Cd). Furthermore, the average mass size distribution was bimodal with major peaks occurring at 0.32-0.56 microm and 5.6-10 microm during the incense burning period. The dry deposition velocities of Cd used fine particulates (PM2.5) and suspended particulate (PM10) mode were 1.86 and 0.99 cm/s in this study, respectively.

  9. Homogeneous matrix deposition on dried agar for MALDI imaging mass spectrometry of microbial cultures.

    Science.gov (United States)

    Hoffmann, Thomas; Dorrestein, Pieter C

    2015-11-01

    Matrix deposition on agar-based microbial colonies for MALDI imaging mass spectrometry is often complicated by the complex media on which microbes are grown. This Application Note demonstrates how consecutive short spray pulses of a matrix solution can form an evenly closed matrix layer on dried agar. Compared with sieving dry matrix onto wet agar, this method supports analyte cocrystallization, which results in significantly more signals, higher signal-to-noise ratios, and improved ionization efficiency. The even matrix layer improves spot-to-spot precision of measured m/z values when using TOF mass spectrometers. With this technique, we established reproducible imaging mass spectrometry of myxobacterial cultures on nutrient-rich cultivation media, which was not possible with the sieving technique. Graphical Abstract ᅟ.

  10. Homogeneous Matrix Deposition on Dried Agar for MALDI Imaging Mass Spectrometry of Microbial Cultures

    Science.gov (United States)

    Hoffmann, Thomas; Dorrestein, Pieter C.

    2015-11-01

    Matrix deposition on agar-based microbial colonies for MALDI imaging mass spectrometry is often complicated by the complex media on which microbes are grown. This Application Note demonstrates how consecutive short spray pulses of a matrix solution can form an evenly closed matrix layer on dried agar. Compared with sieving dry matrix onto wet agar, this method supports analyte cocrystallization, which results in significantly more signals, higher signal-to-noise ratios, and improved ionization efficiency. The even matrix layer improves spot-to-spot precision of measured m/z values when using TOF mass spectrometers. With this technique, we established reproducible imaging mass spectrometry of myxobacterial cultures on nutrient-rich cultivation media, which was not possible with the sieving technique.

  11. Atmospheric mercury simulation using the CMAQ model: formulation description and analysis of wet deposition results

    Science.gov (United States)

    Bullock, O. Russell; Brehme, Katherine A.

    The community multiscale air quality (CMAQ) modeling system has been adapted to simulate the emission, transport, transformation and deposition of atmospheric mercury (Hg) in three distinct forms: elemental Hg gas, reactive gaseous Hg, and particulate Hg. Emissions of Hg are currently defined from information published in the Environmental Protection Agency's Mercury Study Report to Congress. The atmospheric transport of these three forms of Hg is simulated in the same manner as for all other substances simulated by the CMAQ model to date. Transformations of Hg are simulated with four new chemical reactions within the standard CMAQ gaseous chemistry framework and a highly modified cloud chemistry mechanism which includes a compound-specific speciation for oxidized forms of Hg, seven new aqueous-phase Hg reactions, six aqueous Hg chemical equilibria, and a two-way mechanism for the sorption of dissolved oxidized Hg to elemental carbon particles. The CMAQ Hg model simulates the partitioning of reactive gaseous Hg between air and cloud water based on the Henry's constant for mercuric chloride. Henry's equilibrium is assumed for elemental Hg also. Particulate Hg is assumed to be incorporated into the aqueous medium during cloud nucleation. Wet and dry deposition is simulated for each of the three forms of Hg. Wet deposition rate is calculated based on precipitation information from the CMAQ meteorological processor and the physicochemical Hg speciation in the cloud chemistry mechanism. Dry deposition rate is calculated based on dry deposition velocity and air concentration information for each of the three forms of Hg. The horizontal modeling domain covers the central and eastern United States and adjacent southern Canada. An analysis of simulated Hg wet deposition versus weekly observations is performed. The results are described for two evaluation periods: 4 April-2 May 1995, and 20 June-18 July 1995.

  12. Measurements and modeling of emissions, dispersion and dry deposition of ammonia from swine facilities

    Science.gov (United States)

    Bajwa, Kanwardeep Singh

    Ammonia has recently gained importance for its increasing atmospheric concentrations and its role in the formation of aerosols. Studies have shown increasing atmospheric concentration levels of NH3 and NH 4+, especially in the regions of concentrated animal feeding operations. Atmospheric inputs of reduced nitrogen as ammonia and ammonium by dry and wet deposition may represent a substantial contribution to the acidification of semi natural ecosystems and could also affect sensitive coastal ecosystems and estuaries. The anaerobic lagoon and spray method, commonly used for waste storage and disposal in confined animal feeding operations (CAFO), is a significant source of ammonia emissions. An accurate emission model for ammonia from aqueous surfaces can help in the development of emission factors. Study of dispersion and dry deposition patterns of ammonia downwind of a hog farm will help us to understand how much ammonia gets dry deposited near the farm, and how remaining ammonia gets transported farther away. An experimental and modeling study is conducted of emissions, dispersion and dry deposition of ammonia taking one swine farm as a unit. Measurements of ammonia flux were made at 11 swine facilities in North Carolina using dynamic flow-through chamber system over the anaerobic waste treatment lagoons. Continuous measurements of ammonia flux, meteorological and lagoon parameters were made for 8-10 days at each farm during each of the warm and cold seasons. Ammonia concentrations were continuously measured in the chamber placed over the lagoon using a Thermo Environmental Instrument Incorporated (TECO) Model 17c chemiluminescnce ammonia analyzer. A similar ammonia analyzer was used to measure ammonia concentrations at selected locations on the farm. Barn emissions were measured using open-path Fourier transform infrared (OP-FTIR) spectroscopy. A 10 m meteorological tower was erected at each site to measure wind speed and direction, temperature, relative humidity

  13. Wet and dry atmospheric deposition on TiO{sub 2} coated glass

    Energy Technology Data Exchange (ETDEWEB)

    Chabas, Anne, E-mail: anne.chabas@lisa.univ-paris12.f [Laboratoire Interuniversitaire des Systemes Atmospheriques, Universite Paris 12, Universite Paris 7, CNRS, 61 avenue du General de Gaulle, 94010 Creteil (France); Gentaz, Lucile; Lombardo, Tiziana; Sinegre, Romain [Laboratoire Interuniversitaire des Systemes Atmospheriques, Universite Paris 12, Universite Paris 7, CNRS, 61 avenue du General de Gaulle, 94010 Creteil (France); Falcone, Roberto [Stazione Sperimentale del Vetro, Calle Briati 10, 30141 Murano, Venezia (Italy); Verita, Marco [Laboratorio di Analisi dei Materiali Antichi LAMA, Universita IUAV di Venezia, S. Polo 2648, 30125 Venezia (Italy); Cachier, Helene [Laboratoire des Sciences du Climat et de l' Environnement, CNRS-CEA, Orme des Merisiers, bat 701, 91191Gif sur Yvette (France)

    2010-12-15

    To prevent the soiling of glass window used in the built environment, the use TiO{sub 2} coated products appears an important application matter. To test the cleaning efficiency and the sustainability of self-cleaning glass, a field experiment was conducted under real life condition, on a site representative of the background urban pollution. Samples of float glass, used as reference, and commercialized TiO{sub 2} coated glasses were exposed to dry and wet atmospheric deposition during two years. The crossed optical, chemical and microscopic evaluations performed, after withdrawal, allowed highlighting a sensible difference between the reference and the self-cleaning substrate in terms of accumulation, nature, abundance and geometry of the deposit. This experiment conducted in real site emphasized on the efficacy of self-cleaning glass to reduce the maintenance cost. - This paper evaluates the self-cleaning glass efficiency highlighting its ability to prevent soiling and to be used as a mean of remediation.

  14. Proceedings of the NAPAP (National Acid Precipitation Assessment Program) workshop on dry deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, B.B.; Wesely, M.L.; Lindberg, S.E.; Bromberg, S.M. (eds.)

    1986-01-01

    Knowledge of dry deposition is limited by the inability to make the necessary measurements in other than special circumstances. The need to generate confidence in the available measurement techniques was emphasized. There is need for more frequent collocation of experiments and for more collaboration of researchers. Discussions among the specialist groups focused attention on the greatly dissimilar experimental constraints associated with different techniques. A summary of relevant considerations is given. Extreme difficulties arise when trying to conduct a side-by-side comparison of all of the available methods. In all cases there is need to improve measurement methods. This developmental effort is presently underway, but augmentation is required. The present focus on questions regarding so-called acidic deposition is too confining to permit a broad-based attack on the overall problem of air pollution in the context of energy and agricultural options. A program developed in response to questions concerning acidic deposition should not be expected to address questions arising in other contexts. The acid deposition concern is real and immediate, and if carefully arranged the research program generated to provide the most urgently desired answers could also constitute an entry into a longer-term investigation of broader issues. 34 refs., 3 tabs.

  15. Dry deposition model for a microscale aerosol dispersion solver based on the moment method

    CERN Document Server

    Šíp, Viktor

    2016-01-01

    A dry deposition model suitable for use in the moment method has been developed. Contributions from five main processes driving the deposition - Brownian diffusion, interception, impaction, turbulent impaction, and sedimentation - are included in the model. The deposition model was employed in the moment method solver implemented in the OpenFOAM framework. Applicability of the developed expression and the moment method solver was tested on two example problems of particle dispersion in the presence of a vegetation on small scales: a flow through a tree patch in 2D and a flow through a hedgerow in 3D. Comparison with the sectional method showed that the moment method using the developed deposition model is able to reproduce the shape of the particle size distribution well. The relative difference in terms of the third moment of the distribution was below 10\\% in both tested cases, and decreased away from the vegetation. Main source of this difference is a known overprediction of the impaction efficiency. When ...

  16. Quantifying particulate matter deposition in Niwot Ridge, Colorado: Collection of dry deposition using marble inserts and particle imaging using the FlowCAM

    Science.gov (United States)

    Goss, Natasha R.; Mladenov, Natalie; Seibold, Christine M.; Chowanski, Kurt; Seitz, Leslie; Wellemeyer, T. Barret; Williams, Mark W.

    2013-12-01

    Atmospheric wet and dry deposition are important sources of carbon for remote alpine lakes and soils. The carbon inputs from dry deposition in alpine National Atmospheric Deposition Program (NADP) collectors, including aeolian dust and biological material, are not well constrained due to difficulties in retaining particulate matter in the collectors. Here, we developed and tested a marble insert for dry deposition collection at the Niwot Ridge Long Term Ecological Research Station (NWT LTER) Soddie site (3345 m) between 24 May and 8 November 2011. We conducted laboratory tests of the insert's effect on particulate matter (PM) mass and non-purgeable organic carbon (DOC) and found that the insert did not significantly change either measurement. Thus, the insert may enable dry deposition collection of PM and DOC at NADP sites. We then developed a method for enumerating the collected wet and dry deposition with the Flow Cytometer and Microscope (FlowCAM), a dynamic-image particle analysis tool. The FlowCAM has the potential to establish morphology, which affects particle settling and retention, through particle diameter and aspect ratio. Particle images were used to track the abundance of pollen grains over time. Qualitative image examination revealed that most particles were biological in nature, such as intact algal cells and pollen. Dry deposition loading to the Soddie site as determined by FlowCAM measurements was highly variable, ranging from 100 to >230 g ha-1 d-1 in June-August 2011 and peaking in late June. No significant difference in diameter or aspect ratio was found between wet and dry deposition, suggesting fundamental similarities between those deposition types. Although FlowCAM statistics and identification of particle types proved insightful, our total-particle enumeration method had a high variance and underestimated the total number of particles when compared to imaging of relatively large volumes (60-125 mL) from a single sample. We recommend use of

  17. Heavy metals determination in dry surrogate depositions, characterization of an urban and a natural site

    Energy Technology Data Exchange (ETDEWEB)

    Barilli, L.; Olivieri, P. [ENEA, Centro Ricerche Ezio Clementel, Bologna (Italy). Dipt. Ambiente; Morselli, L.; Cecchini, M. [Bologna Univ., Bologna (Italy). Dipt. di Chmica Industriale e dei Materiali; Amorolo, R.; Di Carlo, V.; Francacaviglia, R.; Gataleta, L. [Istituto Sperimentale per la Nutrizione delle Piante, Rome (Italy)

    1999-10-01

    The present work describes a methodological approach for the assessment of the amount of several toxic heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) associated with atmospheric particulate matter in surrogate dry deposition. The aim of the study is the evaluation of heavy metal fluxes at ground level in surrogate dry deposition and the comparison between their estimated in two different stations over the period February-December 1997. A description is given of the complete procedure from sampling to data elaboration and results are reported with special attention to the comparative aspects of the two stations. [Italian] Nella presente nota viene descritto un approccio metodologico per la valutazione delle quantita' di alcuni metalli pesanti tossici (Cd, Cr, Cu, Ni, Pb, Zn) associati al particolato atmosferico, nella deposizione secca surrogata a livello del suolo allo scopo di valutare i flussi di metalli pesanti nella deposizione indicata e il confronto tra le due stazioni dal febbraio al dicembre 1997. Viene riportata la descrizione dell'intera procedura, dal campionamento all'elaborazione dei dati, e vengono riportati i risultati.

  18. Modeling and mapping of atmospheric mercury deposition in adirondack park, new york.

    Directory of Open Access Journals (Sweden)

    Xue Yu

    Full Text Available The Adirondacks of New York State, USA is a region that is sensitive to atmospheric mercury (Hg deposition. In this study, we estimated atmospheric Hg deposition to the Adirondacks using a new scheme that combined numerical modeling and limited experimental data. The majority of the land cover in the Adirondacks is forested with 47% of the total area deciduous, 20% coniferous and 10% mixed. We used litterfall plus throughfall deposition as the total atmospheric Hg deposition to coniferous and deciduous forests during the leaf-on period, and wet Hg deposition plus modeled atmospheric dry Hg deposition as the total Hg deposition to the deciduous forest during the leaf-off period and for the non-forested areas year-around. To estimate atmospheric dry Hg deposition we used the Big Leaf model. The average atmospheric Hg deposition to the Adirondacks was estimated as 17.4 [Formula: see text]g m[Formula: see text] yr[Formula: see text] with a range of -3.7-46.0 [Formula: see text]g m[Formula: see text] yr[Formula: see text]. Atmospheric Hg dry deposition (370 kg yr[Formula: see text] was found to be more important than wet deposition (210 kg yr[Formula: see text] to the entire Adirondacks (2.4 million ha. The spatial pattern showed a large variation in atmospheric Hg deposition with scattered areas in the eastern Adirondacks having total Hg deposition greater than 30 μg m(-2 yr(-1, while the southwestern and the northern areas received Hg deposition ranging from 25-30 μg m(-2 yr(-1.

  19. A modified micrometeorological gradient method for estimating O3 dry deposition over a forest canopy

    Directory of Open Access Journals (Sweden)

    Z. Y. Wu

    2015-01-01

    Full Text Available Small pollutant concentration gradients between levels above a plant canopy result in large uncertainties in estimated air–surface exchange fluxes when using existing micrometeorological gradient methods, including the aerodynamic gradient method (AGM and the modified Bowen-Ratio method (MBR. A modified micrometeorological gradient method (MGM is proposed in this study for estimating O3 dry deposition fluxes over a forest canopy using concentration gradients between a level above and a level below the canopy top, taking advantage of relatively large gradients between these levels due to significant pollutant uptake at top layers of the canopy. The new method is compared with the AGM and MBR methods and is also evaluated using eddy-covariance (EC flux measurements collected at the Harvard Forest Environmental Measurement Site, Massachusetts during 1993–2000. All the three gradient methods (AGM, MBR and MGM produced similar diurnal cycles of O3 dry deposition velocity (Vd(O3 to the EC measurements, with the MGM method being the closest in magnitude to the EC measurements. The multi-year average Vd(O3 differed significantly between these methods, with the AGM, MBR and MGM method being 2.28, 1.45 and 1.18 times of that of the EC. Sensitivity experiments identified several input parameters for the MGM method as first-order parameters that affect the estimated Vd(O3. A 10% uncertainty in the wind speed attenuation coefficient or canopy displacement height can cause about 10% uncertainty in the estimated Vd(O3. An unrealistic leaf area density vertical profile can cause an uncertainty of a factor of 2.0 in the estimated Vd(O3. Other input parameters or formulas for stability functions only caused an uncertainly of a few percent. The new method provides an alternative approach in monitoring/estimating long-term deposition fluxes of similar pollutants over tall canopies.

  20. Total atmospheric mercury deposition in forested areas in South Korea

    Science.gov (United States)

    Han, Jin-Su; Seo, Yong-Seok; Kim, Moon-Kyung; Holsen, Thomas M.; Yi, Seung-Muk

    2016-06-01

    In this study, mercury (Hg) was sampled weekly in dry and wet deposition and throughfall and monthly in litterfall, and as it was volatilized from soil from August 2008 to February 2010 to identify the factors influencing the amount of atmospheric Hg deposited to forested areas in a temperate deciduous forest in South Korea. For this location there was no significant correlation between the estimated monthly dry deposition flux (litterfall + throughfall - wet deposition) (6.7 µg m-2 yr-1) and directly measured dry deposition (9.9 µg m-2 yr-1) likely due primarily to Hg losses from the litterfall collector. Dry deposition fluxes in cold seasons (fall and winter) were lower than in warmer seasons (spring and summer). The volume-weighted mean (VWM) Hg concentrations in both precipitation and throughfall were highest in winter, likely due to increased scavenging by snow events. Since South Korea experiences abundant rainfall in summer, VWM Hg concentrations in summer were lower than in other seasons. Litterfall fluxes were highest in the late fall to early winter, when leaves were dropped from the trees (September to November). The cumulative annual Hg emission flux from soil was 6.8 µg m-2 yr-1. Based on these data, the yearly deposition fluxes of Hg calculated using two input approaches (wet deposition + dry deposition or throughfall + litterfall) were 6.8 and 3.6 µg m-2 yr-1, respectively. This is the first reported study which measured the amount of atmospheric Hg deposited to forested areas in South Korea, and thus our results provide useful information to compare against data related to Hg fate and transport in this part of the world.

  1. Atmospheric dry deposition of mineral dust to the Gulf of Aqaba, Red Sea: rate and trace elements.

    Science.gov (United States)

    Al-Taani, Ahmed A; Rashdan, Maen; Khashashneh, Safaa

    2015-03-15

    Atmospheric dry deposition to the Gulf of Aqaba (GoA) is particularly a significant source of trace elements. Amid desert regions, the Gulf receives high fluxes of mineral dust with an average rate of 34.68 g/m(2)/year measured in 2012. Patterns of dry deposition showed seasonal fluxes with highest rates observed in summer and lowest in winter. The observed variations were attributed to wind direction, timing of deposition and sources of dust. The average dry fluxes of Al, Fe, Mn, Cr, Cd, Cu, Pb and Zn were 551, 440, 10.29, 1.42, 0.04, 0.68, 1.42 and 4.02 mg/m(2)/year, respectively. While the dry deposition fluxes were enriched in Cd, Cu, Pb and Zn indicating their dominant anthropogenic sources, they appeared to be less influenced compared to the neighboring Mediterranean area and other industrial countries, but were similar to or slightly higher than those in remote areas. The enrichment values for Fe and Mn were low, consistent with their crustal origin. The fluxes of all elements suggested the impacts of both crustal (due to climate change) and anthropogenic sources became stronger in this region. The Sahara dust was probably a minor contributor to dry deposition in the GoA.

  2. Construction of a methodologically consistent time series of substance loads and their impacts in Germany. Pt. 1. Comparison of the calculated dry deposition fluxes for 2005 and 2020; Erstellung einer methodenkonsistenten Zeitreihe von Stoffeintraegen und ihren Wirkungen in Deutschland. T. 1. Comparison of the calculated dry deposition fluxes for 2005 and 2020. Genfer Luftreinhaltekonvention der UNECE

    Energy Technology Data Exchange (ETDEWEB)

    Wichink Kruit, Roy; Boersen, Gerbrand; Schaap, Martijn; Builtjes, Peter [TNO Niederlande, Utrecht (Netherlands)

    2013-01-15

    The LOTOS-EUROS model is used to determine the dry deposition flux. A comparison is made between the calculated dry deposition using the projected emissions in 2020 for Germany, accounting for the reductions under the current legislation, and the calculated dry deposition fluxes using the PAREST 2005 emission database.

  3. Dry Deposition Velocity Estimation for the Savannah River Site: Part 1 – Parametric Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Napier, Bruce A.

    2012-01-16

    Values for the dry deposition velocity of airborne particles were estimated with the GENII Version 2.10 computer code for the Savannah River site using assumptions about surface roughness parameters and particle size and density. Use of the GENII code is recommended by the U.S. Department of Energy for this purpose. Meteorological conditions evaluated include atmospheric stability classes D, E, and F and wind speeds of 0.5, 1.0, 1.5, and 3.0 m/s. Local surface roughness values ranging from 0.03 to 2 meters were evaluated. Particles with mass mean diameters of 1, 5, and 10 microns and densities of 1, 3, and 5 g/cm3 were evaluated.

  4. Dry Deposition, Surface Production and Dynamics of Aerosols in the Marine Boundary Layer

    DEFF Research Database (Denmark)

    Fairall, C.W.; Larsen, Søren Ejling

    1984-01-01

    A model of downward aerosol panicle flux characterized by dry deposition velocity, Vd, due to Slinn and Slinn (1980) is generalized to the case of nonzero surface concentration (absorbing surface with a surface source). A more general expression for the flux at some reference height is developed...... which includes Vd and an effective surface source strength, Si, which is a function of the true surface source strength, Si, and the particle transport properties below the reference height. The general expression for the surface flux is incorporated into a dynamic mixed layer model of the type...... developed by Davidson et al. (1983). This three layer model (diffusion sublayer, turbulent surface layer and mixed layer) is applied to an open ocean marine regime where boundary layer advection is ignored. The aerosol concentration in the boundary layer is considered to consist of sea salt particles...

  5. Depositing nanoparticles on a silicon substrate using a freeze drying technique

    Science.gov (United States)

    Sigehuzi, Tomoo

    2017-08-01

    For the microscopic observation of nanoparticles, an adequate sample preparation is an essential part of this task. Much research has been performed for usable preparation methods that will yield aggregate-free samples. A freeze drying technique, which only requires a -80 °C freezer and a freeze dryer, is shown to provide an on-substrate dispersion of mostly isolated nanoparticles. The particle density could be made sufficiently high for efficient observations using atomic force microscopy. Since this sandwich method is purely physical, it could be applied to deposit various nanoparticles independent of their surface chemical properties. Suspension film thickness, or the dimensionality of the suspension film, was shown to be crucial for the isolation of the particles. Silica nanoparticles were dispersed on a silicon substrate using this method and the sample properties were examined using atomic force microscopy.

  6. Dry deposition velocity of atmospheric nitrogen in a typical red soil agro-ecosystem in Southeastern China.

    Science.gov (United States)

    Zhou, Jing; Cui, Jian; Fan, Jian-ling; Liang, Jia-ni; Wang, Ti-jian

    2010-08-01

    Atmospheric dry deposition is an important nitrogen (N) input to farmland ecosystems. The main nitrogen compounds in the atmosphere include gaseous N (NH3, NO2, HNO3) and aerosol N (NH4+/NO3-). With the knowledge of increasing agricultural effects by dry deposition of nitrogen, researchers have paid great attention to this topic. Based on the big-leaf resistance dry deposition model, dry N deposition velocities (Vd) in a typical red soil agro-ecosystem, Yingtan, Jiangxi, Southeastern China, were estimated with the data from an Auto-Meteorological Experiment Station during 2004-2007. The results show that hourly deposition velocities (Vdh) were in the range of 0.17-0.34, 0.05-0.24, 0.57-1.27, and 0.05-0.41 cm/s for NH3, NO2, HNO3, and aerosol N, respectively, and the Vdh were much higher in daytime than in nighttime and had a peak value around noon. Monthly dry deposition velocities (Vdm) were in the range of 0.14-0.36, 0.06-0.18, and 0.07-0.25 cm/s for NH3, NO2, and aerosol N, respectively. Their minimum values appeared from June to August, while their maximum values occurred from February to March each year. The maximum value for HNO3 deposition velocities appeared in July each year, and Vdm(HNO3) ranged from 0.58 to 1.31 cm/s during the 4 years. As for seasonal deposition velocities (Vds), Vds(NH3), Vds(NO2), and Vds(aerosol N) in winter or spring were significantly higher than those in summer or autumn, while Vds(HNO3) in summer were higher than that in winter. In addition, there is no significant difference among all the annual means for deposition velocities (Vda). The average values for NH3, NO2, HNO3, and aerosol N deposition velocities in the 4 years were 0.26, 0.12, 0.81, and 0.16 cm/s, respectively. The model is convenient and feasible to estimate dry deposition velocity of atmospheric nitrogen in the typical red soil agro-ecosystem.

  7. The interconnection of wet and dry deposition and the alteration of deposition budgets due to incorporation of new process understanding in regional models

    Science.gov (United States)

    Dennis, R. L.; Bash, J. O.; Foley, K. M.; Gilliam, R.; Pinder, R. W.

    2013-12-01

    Deposition is affected by the chemical and physical processes represented in the regional models as well as source strength. The overall production and loss budget (wet and dry deposition) is dynamically connected and adjusts internally to changes in process representation. In addition, the scrubbing of pollutants from the atmosphere by precipitation is one of several processes that remove pollutants, creating a coupling with the atmospheric aqueous and gas phase chemistry that can influence wet deposition rates in a nonlinear manner. We explore through model sensitivities with the regional Community Multiscale Air Quality (CMAQ) model the influence on wet and dry deposition, and the overall continental nitrogen budget, of changes in three process representations in the model: (1) incorporation of lightning generated NO, (2) improved representation of convective precipitation, and (3) replacement of the typical unidirectional dry deposition of NH3 with a state of the science representation of NH3 bi-directional air-surface exchange. Results of the sensitivity studies will be presented. (1) Incorporation of lightning generated NO significantly reduces a negative bias in summer wet nitrate deposition, but is sensitive to the choice of convective parameterization. (2) Use of a less active trigger of convective precipitation in the WRF meteorological model to reduce summertime precipitation over prediction bias reduces the generation of NO from lightning. It also reduces the wet deposition of nitrate and increases the dry deposition of oxidized nitrogen, as well as changing (reducing) the surface level exposure to ozone. Improvements in the convective precipitation processes also result in more non-precipitating clouds leading to an increase in SO4 production through the aqueous pathway resulting in improvements in summertime SO4 ambient aerosol estimates.(3) Incorporation of state of the science ammonia bi-directional air surface exchange affects both the dry

  8. Spatial and seasonal variations of atmospheric sulfur concentrations and dry deposition at 16 rural and suburban sites in China

    Science.gov (United States)

    Luo, Xiaosheng; Pan, Yuepeng; Goulding, Keith; Zhang, Lin; Liu, Xuejun; Zhang, Fusuo

    2016-12-01

    The large emissions of sulfur dioxide (SO2) in China have raised worldwide concerns due to its contribution to acid rain and particulate pollution. Monitoring sulfur (S) concentrations and estimating its deposition are important for evaluating air quality and its effects on ecosystems and human health. To date atmospheric dry S deposition in China remains unclear due to the paucity of measurements, especially in rural regions where the ecosystems are sensitive to acid deposition. In this study, we monitored both SO2 and particulate SO42- (pSO42-) concentrations at 8 sites south and 8 sites north of the Huai River in rural and suburban parts of China between 2010 and 2012. The measured concentration of SO2 and pSO42- were combined with GEOS-Chem modeled dry deposition velocities to estimate dry S deposition inputs to the surfaces. SO2 and pSO42- concentrations were high from October/November to next March/April and they (esp. SO2) decreased sharply since March/April at the northern sites, reflecting elevated SO2 emissions by winter heating (which normally starts in October/November and ends in March/April in the north of the Huai River). However the southern sites did not show this trend. Annual dry deposition of SO2 plus pSO42- in this study ranged from 3.1 to 27.1 kg S ha-1 across all the sites in the year 2011 (except one site from May 2011 to April 2012) and showed large spatial variation. The sites in northern China had greater dry deposition due to the higher S concentrations compared with sites in southern China. We also found relatively low pSO42-/pNO3- ratios at most sites, reflecting NOx emissions had a larger influence than SO2 emissions on particle composition during the 2010-2012 period at the measurement sites. Our results suggest that dry S deposition is still important input to ecosystems in spite of slow reduction of Chinese national SO2 emissions since 2005. More research on both wet and dry S deposition and their impacts on the environment and

  9. Projecting Ammonia Dry Deposition Using Passive Samplers and a Bi-Directional Exchange Model

    Science.gov (United States)

    Robarge, W. P.; Walker, J. T.; Austin, R. E.

    2011-12-01

    Animal agriculture within the United States is known to be a source of ammonia (NH3) emissions. Dry deposition of NH3 to terrestrial ecosystems immediately surrounding large local sources of NH3 emissions (e.g. animal feeding operations) is difficult to measure, and is best estimated via models. Presented here are results for a semi-empirical modeling approach for estimating air-surface exchange fluxes of NH3 downwind of a large poultry facility (~ 3.5 million layers) using a bi-directional air-surface exchange model. The modeling domain is the western section of the Pocosin Lakes National Wildlife Refuge in Tyrrell, Washington, and Hyde Counties of eastern North Carolina in the South Atlantic Coastal Plain physiographic region. Vegetation within the modeling domain is primarily pocosin wetlands, characterized by acid (pH 3.6) peat soils and a thick canopy of shrub vegetation (leatherwood (Cyrilla racemiflora), inkberry (Ilex glabra), wax myrtle (Morella cerifera)). Land surrounding the refuge is primarily used for crop production: ~ 28%, 24%, and 45% agricultural in Tyrell, Hyde, and Washington counties, respectively. Ammonia air-surface exchange (flux) was calculated using a two-layer canopy compensation point model developed by Nemitz et al. (2001. Quart. J. Roy. Met. Soc. 127, 815 - 833.) as implemented by Walker et al. (2008. Atmos. Environ., 42, 3407 - 3418.), in which the competing processes of emission and deposition within the foliage-soil system were taken into account by relating the net canopy-scale NH3 flux to the net emission potential of the canopy (i.e., foliage and soil). Ammonia air concentrations were measured using ALPHA passive samplers (Center for Ecology and Hydrology, Edinburgh) along transects to the north and northeast of the poultry facility at distances of 800, 2000 and 3200 m, respectively. Samplers were deployed in duplicate at each location at a height of 5.8 m from July 2008 to July 2010 weekly during warm months and bi-weekly curing

  10. Emission and dry deposition of accumulation mode particles in the Amazon Basin

    Directory of Open Access Journals (Sweden)

    L. Ahlm

    2010-11-01

    Full Text Available Size-resolved vertical aerosol number fluxes of particles in the diameter range 0.25–2.5 μm were measured with the eddy covariance method from a 53 m high tower over the Amazon rain forest, 60 km NNW of Manaus, Brazil. This study focuses on data measured during the relatively clean wet season, but a shorter measurement period from the more polluted dry season is used as a comparison.

    Size-resolved net particle fluxes of the five lowest size bins, representing 0.25–0.45 μm in diameter, were in general dominated by deposition in more or less all wind sectors in the wet season. This is an indication that the source of primary biogenic aerosol particles may be small in this particle size range. Transfer velocities within this particle size range were observed to increase linearly with increasing friction velocity and increasing particle diameter.

    In the diameter range 0.5–2.5 μm, vertical particle fluxes were highly dependent on wind direction. In wind sectors where anthropogenic influence was low, net upward fluxes were observed. However, in wind sectors associated with higher anthropogenic influence, deposition fluxes dominated. The net upward fluxes were interpreted as a result of primary biogenic aerosol emission, but deposition of anthropogenic particles seems to have masked this emission in wind sectors with higher anthropogenic influence. The net emission fluxes were at maximum in the afternoon when the mixed layer is well developed, and were best correlated with horizontal wind speed according to the equation

    log10 F=0.48 · U+2.21

    where F is the net emission number flux of 0.5–2.5 μm particles [m−2 s−1] and U is the horizontal wind speed [ms−1] at the top of the tower.

  11. Carbonaceous species in atmospheric aerosols from the Krakow area (Malopolska District: carbonaceous species dry deposition analysis

    Directory of Open Access Journals (Sweden)

    Szramowiat Katarzyna

    2016-01-01

    Full Text Available Organic and elemental carbon content in PM10 was studied at three sites in Malopolska District representing the city centre (Krakow, rural/residential (Bialka and residential/industrial environments (Krakow. The PM10 samples were collected during the winter time study. The highest concentrations of carbonaceous species were observed in Skawina (36.9 μg·m-3 of OC and 9.6 μg·m-3 of EC. The lowest OC and EC concentrations were reported in Krakow (15.2 μg·m-3 and 3.9 μg·m-3, respectively. The highest concentration of carbonaceous species and the highest wind velocities in Skawina influenced the highest values of the dry deposition fluxes. Correlations between OC, EC and chemical constituents and meteorological parameters suggest that a Krakow was influenced by local emission sources and temperature inversion occurrence; b Bialka was under the influence of local emission sources and long-range transport of particles; c Skawina was impacted by local emission sources.

  12. Wear mechanism for spray deposited Al-Si/SiCp composites under dry sliding condition

    Institute of Scientific and Technical Information of China (English)

    滕杰; 李华培; 陈刚

    2015-01-01

    Al-Si/15%SiCp (volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy (OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10−220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

  13. The effect of dry and wet deposition of condensable vapors on secondary organic aerosols concentrations over the continental US

    Directory of Open Access Journals (Sweden)

    C. Knote

    2015-01-01

    Full Text Available The effect of dry and wet deposition of semi-volatile organic compounds (SVOCs in the gas phase on the concentrations of secondary organic aerosol (SOA is reassessed using recently derived water solubility information. The water solubility of SVOCs was implemented as a function of their volatility distribution within the WRF-Chem regional chemistry transport model, and simulations were carried out over the continental United States for the year 2010. Results show that including dry and wet removal of gas-phase SVOCs reduces annual average surface concentrations of anthropogenic and biogenic SOA by 48 and 63% respectively over the continental US. Dry deposition of gas-phase SVOCs is found to be more effective than wet deposition in reducing SOA concentrations (−40 vs. −8% for anthropogenics, and −52 vs. −11% for biogenics. Reductions for biogenic SOA are found to be higher due to the higher water solubility of biogenic SVOCs. The majority of the total mass of SVOC + SOA is actually deposited via the gas phase (61% for anthropogenics and 76% for biogenics. Results are sensitive to assumptions made in the dry deposition scheme, but gas-phase deposition of SVOCs remains crucial even under conservative estimates. Considering reactivity of gas-phase SVOCs in the dry deposition scheme was found to be negligible. Further sensitivity studies where we reduce the volatility of organic matter show that consideration of gas-phase SVOC removal still reduces average SOA concentrations by 31% on average. We consider this a lower bound for the effect of gas-phase SVOC removal on SOA concentrations. A saturation effect is observed for Henry's law constants above 108 M atm−1, suggesting an upper bound of reductions in surface level SOA concentrations by 60% through removal of gas-phase SVOCs. Other models that do not consider dry and wet removal of gas-phase SVOCs would hence overestimate SOA concentrations by roughly 50%. Assumptions about the water

  14. Signal and distribution of volatile Mercury (Hg0) in the Marine High Arctic During Polar Summer in the Sequel of Enhanced Atmospheric Deposition of HgⅡ

    Institute of Scientific and Technical Information of China (English)

    Jonas O. Sommar; Maria E. Andersson

    2008-01-01

    @@ 1 Introduction It has been elucidated that high levels of neurotoxic mercury (Hg) in the Arctic is related to a rapid, near-compete depletion of Hg0 (MDE) in the atmospheric boundary-layer occurring episodically during the Polar spring[1].

  15. Dry and wet "deposition" studies of the degradation of cement mortars

    Directory of Open Access Journals (Sweden)

    Martínez-Ramírez, S.

    1998-06-01

    Full Text Available The reaction of portland cement mortars with SO2 gaseous pollutant and artificial 'acid rain' solution has been examined using laboratory exposure chambers, with realistic presentation rates of pollutants. The mortar were previously carbonated to produce superficial carbonation. Two mortars with different w/c ratio and hence specific surface were prepared and exposed into the chambers. For dry deposition of SO2 pollutant gas, the important roles of water and water plus oxidant in increasing chemical reaction are readily revealed. Further, accessible porosity also increases reaction through increased times of reaction of pollutant with the mortars. Interestingly, in the absence of deliberate surface wetting, the presence of oxidant, ozone, leads to a reduction in the already limited extent of reaction. Wet deposition studies using artificial 'acid rain' solution result in gypsum formation, which is more extensive for mortars of increased w/c ratios.

    Se han realizado ensayos de laboratorio de simulación de los procesos ambientales de "deposición" seca y húmeda sobre morteros de cemento portland, estudiándose las reacciones que se producen con el contaminante SO2 ("deposición" seca y la disolución de 'lluvia acida' ("deposición" húmeda. Los morteros de cemento se carbonataron para favorecer la carbonatación superficial de los mismos. Se prepararon morteros con dos relaciones a/c con el fin de estudiar la influencia que la variable superficie específica tenía en el proceso de deterioro de dichos materiales. En los estudios de deposición seca con SO2 como gas agresivo se ha visto la importancia que el agua y el agua junto a un oxidante tienen en la reacción del contaminante con los componentes del mortero. La superficie específica Juega un papel importante, ya que al aumentar, aumenta la reacción con el contaminante. La reacción en presencia de oxidante, (SO2+O3

  16. Field measurements of dry deposition to spruce foliage and petri dishes in the black forest, F.R.G.

    Science.gov (United States)

    Shanley, James B.

    Dry deposition fluxes of Ca 2+, Mg 2+ , K +, Mn 2+, Pb 2+ and SO 2-4 to spruce foliage and petri dishes were measured in two high-elevation sites ( > 900 m) in the southern Black Forest, F.R.G., during 12 periods (2-7 days, each) from mid-September to mid-November, 1983, In situ extraction of deposited material from small spruce branches allowed repeated use of the same foliar collecting surfaces for a direct comparison of deposition between periods. Fluxes were corrected for leaching of internally cycled constituents using factors determined from serial extraction experiments. The ratio of flux to petri dishes vs foliage ( P/F) was > 1.0 for Ca 2+, Pb 2+ and SO 2-4, and somewhat < 1.0 but more constant for Mg 2+ . Temporal variations in dry deposition fluxes at an exposed site near the industrialized Rhine Valley correlated with variations in total air particulate concentrations at a nearby air quality station. Deposition rates were comparable in magnitude but different in temporal pattern at a remote site in the Black Forest interior. Fluxes at each site reached a minimum during the period of 4-9 November when a regional air inversion confined pollutants to the Rhine Valley below the study sites. High fluxes accompanied the inversion break-up.

  17. A Review on Modeling and Monitoring of Dust Dry Deposition%粉尘干沉降研究

    Institute of Scientific and Technical Information of China (English)

    李卓群; 张洁; 黄宁; 邵亚平; 郑晓静

    2011-01-01

    粉尘在地球系统中的循环是一个受到广泛关注的研究领域,而粉尘干沉降是该循环中的关键一环.从粉尘干沉降的基本特征入手,分析粉尘在大气边界层中的运动规律和地表收集粉尘的物理过程;结合颗粒性质,地表特征以及流场条件等因素,对粉尘干沉降的研究工作进行了简要的回顾;分析并比较了现有的粉尘干沉降方案和实验结果,对影响粉尘干沉降过程的主要因素进行了讨论.通过对已有工作的总结和分析,指出了粉尘干沉降研究中存在的主要问题及其发展趋势.%Dust dry deposition is a key component of the dust cycle in the earth system. In this review paper, we first outline the basic characteristics of dust motion in the atmospheric boundary layer and the dust collection processes at the surface. The effect of the physical features of the surface on the efficiency of dust collection is discussed. The dust dry deposition schemes are reviewed, considering dust property, surface character and wind field conditions. A summary of dry deposition schemes, measurements and model-measurement comparisons is then presented. The remaining challenges in dry deposition modeling and monitoring are discussed.

  18. Atmospheric deposition to forests in the eastern USA

    Science.gov (United States)

    Risch, Martin R.; DeWild, John F.; Gay, David A.; Zhang, Leiming; Boyer, Elizabeth W.; Krabbenhoft, David P.

    2017-01-01

    Atmospheric mercury (Hg) deposition to forests is important because half of the land cover in the eastern USA is forest. Mercury was measured in autumn litterfall and weekly precipitation samples at a total of 27 National Atmospheric Deposition Program (NADP) monitoring sites in deciduous and mixed deciduous-coniferous forests in 16 states in the eastern USA during 2007–2014. These simultaneous, uniform, repeated, annual measurements of forest Hg include the broadest area and longest time frame to date. The autumn litterfall-Hg concentrations and litterfall mass at the study sites each year were combined with annual precipitation-Hg data. Rates of litterfall-Hg deposition were higher than or equal to precipitation-Hg deposition rates in 70% of the annual data, which indicates a substantial contribution from litterfall to total atmospheric-Hg deposition. Annual litterfall-Hg deposition in this study had a median of 11.7 μg per square meter per year (μg/m2/yr) and ranged from 2.2 to 23.4 μg/m2/yr. It closely matched modeled dry-Hg deposition, based on land cover at selected NADP Hg-monitoring sites. Mean annual atmospheric-Hg deposition at forest study sites exhibited a spatial pattern partly explained by statistical differences among five forest-cover types and related to the mapped density of Hg emissions. Forest canopies apparently recorded changes in atmospheric-Hg concentrations over time because litterfall-Hg concentrations decreased year to year and litterfall-Hg concentrations were significantly higher in 2007–2009 than in 2012–2014. These findings reinforce reported decreases in Hg emissions and atmospheric elemental-Hg concentrations during this same time period. Methylmercury (MeHg) was detected in all litterfall samples at all sites, compared with MeHg detections in less than half the precipitation samples at selected sites during the study. These results indicate MeHg in litterfall is a pathway into the terrestrial food web where it can

  19. Quantification of Gaseous Elemental Mercury Dry Deposition to Environmental Surfaces using Mercury Stable Isotopes in a Controlled Environment

    Science.gov (United States)

    Rutter, A. P.; Schauer, J. J.; Shafer, M. M.; Olson, M.; Robinson, M.; Vanderveer, P.; Creswell, J. E.; Parman, A.; Mallek, J.; Gorski, P.

    2009-12-01

    Andrew P. Rutter (1) * *, James J, Schauer (1,2) *, Martin M. Shafer(1,2), Michael R. Olson (1), Michael Robinson (1), Peter Vanderveer (3), Joel Creswell (1), Justin L. Mallek (1), Andrew M. Parman (1) (1) Environmental Chemistry and Technology Program, 660 N. Park St, Madison, WI 53705. (2) Wisconsin State Laboratory of Hygiene, 2601 Agriculture Drive, Madison, WI 53718. (3) Biotron, University of Wisconsin - Madison, 2115 Observatory Drive, Madison, WI 53706 * Correspond author(jjschauer@wisc.edu) * *Presenting author (aprutter@wisc.edu) Abstract Gaseous elemental mercury (GEM) is the predominant component of atmospheric mercury outside of arctic depletion events, and locations where anthropogenic point sources are not influencing atmospheric concentrations. GEM constitutes greater than 99% of the mercury mass in most rural and remote locations. While dry and wet deposition of atmospheric mercury is thought to be dominated by oxidized mercury (a.k.a. reactive mercury), only small GEM uptake to environmental surfaces could impact the input of mercury to terrestrial and aquatic ecosystems. Dry deposition and subsequent re-emission of gaseous elemental mercury is a pathway from the atmosphere that remains only partially understood from a mechanistic perspective. In order to properly model GEM dry deposition and re-emission an understanding of its dependence on irradiance, temperature, and relative humidity must be measured and parameterized for a broad spectrum of environmental surfaces colocated with surrogate deposition surfaces used to make field based dry deposition measurements. Measurements of isotopically enriched GEM dry deposition were made with a variety of environmental surfaces in a controlled environment room at the University of Wisconsin Biotron. The experimental set up allowed dry deposition components which are not easily separated in the field to be decoupled. We were able to isolate surface transfer processes from variabilities caused by

  20. A Blue Spectral Shift of the Hemoglobin Soret Band Correlates with the Age (Time Since Deposition) of Dried Bloodstains

    Science.gov (United States)

    Hanson, Erin K.; Ballantyne, Jack

    2010-01-01

    The ability to determine the time since deposition of a bloodstain found at a crime scene could prove invaluable to law enforcement investigators, defining the time frame in which the individual depositing the evidence was present. Although various methods of accomplishing this have been proposed, none has gained widespread use due to poor time resolution and weak age correlation. We have developed a method for the estimation of the time since deposition (TSD) of dried bloodstains using UV-VIS spectrophotometric analysis of hemoglobin (Hb) that is based upon its characteristic oxidation chemistry. A detailed study of the Hb Soret band (λmax = 412 nm) in aged bloodstains revealed a blue shift (shift to shorter wavelength) as the age of the stain increases. The extent of this shift permits, for the first time, a distinction to be made between bloodstains that were deposited minutes, hours, days and weeks prior to recovery and analysis. The extent of the blue shift was found to be a function of ambient relative humidity and temperature. The method is extremely sensitive, requiring as little as a 1 µl dried bloodstain for analysis. We demonstrate that it might be possible to perform TSD measurements at the crime scene using a portable low-sample-volume spectrophotometer. PMID:20877468

  1. Long term precipitation chemistry and wet deposition in a remote dry savanna site in Africa (Niger

    Directory of Open Access Journals (Sweden)

    C. Galy-Lacaux

    2008-03-01

    VWM concentrations around the mean (1994–2005 presents fluctuations between ±5% and ±30% mainly attributed to the variations of sources strength associated with rainfall spatio-temporal distribution. From 1994 to 2005, the total mean wet deposition flux in the Sahelian region is 60.1 mmol.m−2.yr−1 and fluctuates around ±25%. Finally, Banizoumbou measurements, are compared to other long-term measurements of precipitation chemistry in the wet savanna of Lamto (Côte d'Ivoire and in the forested zone of Zoétélé (Cameroon. The total chemical loadings presents a strong negative gradient from the dry savanna to the forest (143.7, 100.2 to 86.6 μeq.l–1, associated with the gradient of terrigeneous compounds sources. The wet deposition fluxes present an opposite gradient, with 60.0 mmol.m−2.yr−1 in Banizoumbou, 108.6 mmol.m−2.yr–1 in Lamto and 162.9 mmol.m−2.yr−1 in Zoétélé, controlled by the rainfall gradient along the ecosystems transect.

  2. Long term precipitation chemistry and wet deposition in a remote dry savanna site in Africa (Niger

    Directory of Open Access Journals (Sweden)

    C. Galy-Lacaux

    2009-03-01

    , the total mean wet deposition flux in the Sahelian region is of 60.1 mmol.m−2.yr−1 ±25%. Finally, Banizoumbou measurements are compared to other long-term measurements of precipitation chemistry in the wet savanna of Lamto (Côte d'Ivoire and in the forested zone of Zoétélé (Cameroon. The total chemical loading presents a maximum in the dry savanna and a minimum in the forest (from 143.7, 100.2 to 86.6 μeq.l−1, associated with the gradient of terrigeneous sources. The wet deposition fluxes present an opposite trend, with 60.0 mmol.m−2.yr−1 in Banizoumbou, 108.6 mmol.m−2.yr−1 in Lamto and 162.9 mmol.m−2.yr−1 in Zoétélé, controlled by rainfall gradient along the ecosystems transect.

  3. Dry deposition of acidic air pollutants to tree leaves, determined by a modified leaf-washing technique

    Science.gov (United States)

    Watanabe, Mirai; Takamatsu, Takejiro; Koshikawa, Masami K.; Yamamura, Shigeki; Inubushi, Kazuyuki

    Dry deposition fluxes ( FL) of NO 3- and SO 42- to leaf surfaces were measured for Japanese red pine ( Pinus densiflora), Japanese cedar ( Cryptomeria japonica), Japanese cypress ( Chamaecyparis obtusa), and Japanese white oak ( Quercus myrsinaefolia), together with atmospheric concentrations ( CL) of NO x (NO + NO 2), T-NO 3 (gaseous HNO 3 + particulate NO 3-) and SO x (gaseous SO 2 + particulate SO 42-) around the leaves in a suburban area of Japan, using a modified leaf-washing technique. FL of NO 3- and SO 42- decreased as follows: pine >> cedar > cypress ≥ oak and pine >> cedar > oak ≥ cypress, respectively. FL of NO 3- for all tree species fluctuated synchronously with CL of T-NO 3. FL of SO 42- fluctuated with CL of SO x, but the dominant pollutant deposited (SO 2 or SO 42-) appeared to differ for different tree species. Dry deposition conductance ( KL) of T-NO 3 and SO x was derived as an FL/ CL ratio. Seasonal variations of KL likely reflect the gas/particle ratios of T-NO 3 and SO x, which were affected by meteorological conditions such as temperature. Dry deposition velocities ( Vd) of T-NO 3 and SO x were obtained as the mathematical product of annual mean KL and the total leaf surface areas in the forests. The comparison of Vd among tree species indicated that the loads of acidic air pollutants were higher to coniferous forests than broad-leaved forest because of the higher KL and/or larger leaf surface areas.

  4. Photocatalytic evaluation of self-assembled porous network structure of ferric oxide film fabricated by dry deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yunchan; Kim, Hyungsub; Lee, Geon-Yong; Pawar, Rajendra C.; Lee, Jai-Sung; Lee, Caroline Sunyong, E-mail: sunyonglee@hanyang.ac.kr

    2016-09-15

    Ferric oxide powder in the alpha phase (α-Fe{sub 2}O{sub 3}) was deposited on an aluminum oxide (Al{sub 2}O{sub 3}) substrate by a nanoparticle deposition system using the dry deposition method. X-ray diffraction (XRD) images confirmed that the phase of the deposited α-Fe{sub 2}O{sub 3} did not change. The deposited α-Fe{sub 2}O{sub 3} was characterized in terms of its microstructure using scanning electron microscopy (SEM). A porous network microstructure formed when small agglomerates of Fe{sub 2}O{sub 3} (SAF) were deposited. The deposition and formation mechanism of the microstructure were investigated using SEM and three-dimensional (3D) profile analysis. First, a dense coating layer formed when the film was thinner than the particle size. After that, as the film thickness increased to over 5 μm, the porous network structure formed by excavating the surface of the coating layer as it was bombarded by particles. Rhodamine B (RhB) was degraded after 6 h of exposure to the Fe{sub 2}O{sub 3} coating layer with SAF, which has good photocatalytic activity and a high porous network structure. The kinetic rate constants of the SAF and large agglomerates of Fe{sub 2}O{sub 3} (LAF) were calculated to be 0.197(h{sup −1}) and 0.128(h{sup −1}), respectively, based on the absorbance results. Using linear sweep voltammetry, we confirmed that the photoelectric effect occurred in the coating layer by measuring the resulting current under illuminated and dark conditions. - Graphical abstract: Self-assembled porous photocatalytic film fabricated by dry deposition method for water purification. - Highlights: • Different sizes of Fe{sub 2}O{sub 3} agglomerates were used to form porous network structure. • Fe{sub 2}O{sub 3} agglomerate particles were deposited using solvent-free process. • Self-assembled porous network microstructure formed better with small agglomerates of Fe{sub 2}O{sub 3}. • Fabricated porous network structure showed its potential to be used

  5. Dry-spray deposition of TiO2 for a flexible dye-sensitized solar cell (DSSC) using a nanoparticle deposition system (NPDS).

    Science.gov (United States)

    Kim, Min-Saeng; Chun, Doo-Man; Choi, Jung-Oh; Lee, Jong-Cheon; Kim, Yang Hee; Kim, Kwang-Su; Lee, Caroline Sunyong; Ahn, Sung-Hoon

    2012-04-01

    TiO2 powders were deposited on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates for application to the photoelectrode of a dye-sensitized solar cell (DSSC). In the conventional DSSC manufacturing process, a semiconductor oxide such as TiO2 powder requires a sintering process at higher temperature than the glass transition temperature (T(g)) of polymers, and thus utilization of flexible polymer substrates in DSSC research has been constrained. To overcome this restriction related to sintering, we used a nanoparticle deposition system (NPDS) that could produce a thin coating layer through a dry-spray method under atmospheric pressure at room temperature. The powder was sprayed through a slit-type nozzle having a 0.4 x 10 mm2 rectangular outlet. In order to determine the deposited TiO2 thickness, five kinds of TiO2 layered specimens were prepared, where the specimens have single and double layer structures. Deposited powders on the ITO coated PET substrates were observed using FE-SEM and a scan profiler The thicker TiO2 photoelectrode with a DSSC having a double layer structure showed higher energy efficiency than the single layer case. The highest fabricated flexible DSSC displayed a short circuit current density J(sc) = 1.99 mA cm(-2), open circuit voltage V(oc) = 0.71 V, and energy efficiency eta = 0.94%. These results demonstrate the possibility of utilizing the dry-spray method to fabricate a TiO2 layer on flexible polymer substrates at room temperature under atmospheric pressure.

  6. Size distribution of airborne particle-bound polybrominated diphenyl ethers and its implications for dry and wet deposition.

    Science.gov (United States)

    Luo, Pei; Ni, Hong-Gang; Bao, Lian-Jun; Li, Shao-Meng; Zeng, Eddy Y

    2014-12-01

    Size distribution of particles in part dictates the environmental behavior of particle-bound organic pollutants in the atmosphere. The present study was conducted to examine the potential mechanisms responsible for the distribution of organic pollutants in size fractionated particles and their environmental implications, using an e-waste recycling zone in South China as a case study. Size-fractionated atmospheric particles were collected at the heights of 1.5, 5, and 20 m near two residential apartments and analyzed for polybrominated diphenyl ethers (PBDEs). The concentrations of particle-bound ΣPBDE (sum of 18 PBDE congeners) were significantly greater at 5 and 20 m than those at 1.5 m. The size-fractionated distributions of airborne ΣPBDE displayed trimodal peaks in 0.10–0.18, 1.8–3.2, and 10–18 μm at 1.5 m but only an unimodal peak in 1.0–1.8 μm at 20 m height. Emission sources, resuspension of dust and soil, and volatility of PBDEs were important factors influencing the size distribution of particle-bound PBDEs. The dry deposition fluxes of particle-bound PBDE estimated from the measured data in the present study were approximately twice the estimated wet deposition fluxes, with a total deposition flux of 3000 ng m(–2) d(–1). The relative contributions of particles to dry and wet deposition fluxes were also size-dependent, e.g., coarse (aerodynamic diameters (Dp) > 1.8 μm) and fine (Dp deposition fluxes of PBDEs, respectively.

  7. Error estimations of dry deposition velocities of air pollutants using bulk sea surface temperature under common assumptions

    Science.gov (United States)

    Lan, Yung-Yao; Tsuang, Ben-Jei; Keenlyside, Noel; Wang, Shu-Lun; Arthur Chen, Chen-Tung; Wang, Bin-Jye; Liu, Tsun-Hsien

    2010-07-01

    It is well known that skin sea surface temperature (SSST) is different from bulk sea surface temperature (BSST) by a few tenths of a degree Celsius. However, the extent of the error associated with dry deposition (or uptake) estimation by using BSST is not well known. This study tries to conduct such an evaluation using the on-board observation data over the South China Sea in the summers of 2004 and 2006. It was found that when a warm layer occurred, the deposition velocities using BSST were underestimated within the range of 0.8-4.3%, and the absorbed sea surface heat flux was overestimated by 21 W m -2. In contrast, under cool skin only conditions, the deposition velocities using BSST were overestimated within the range of 0.5-2.0%, varying with pollutants and the absorbed sea surface heat flux was underestimated also by 21 W m -2. Scale analysis shows that for a slightly soluble gas (e.g., NO 2, NO and CO), the error in the solubility estimation using BSST is the major source of the error in dry deposition estimation. For a highly soluble gas (e.g., SO 2), the error in the estimation of turbulent heat fluxes and, consequently, aerodynamic resistance and gas-phase film resistance using BSST is the major source of the total error. In contrast, for a medium soluble gas (e.g., O 3 and CO 2) both the errors from the estimations of the solubility and aerodynamic resistance are important. In addition, deposition estimations using various assumptions are discussed. The largest uncertainty is from the parameterizations for chemical enhancement factors. Other important areas of uncertainty include: (1) various parameterizations for gas-transfer velocity; (2) neutral-atmosphere assumption; (3) using BSST as SST, and (4) constant pH value assumption.

  8. The impact of atmospheric dry deposition associated microbes on the southeastern Mediterranean Sea surface water following an intense dust storm

    Directory of Open Access Journals (Sweden)

    Eyal Rahav

    2016-07-01

    Full Text Available This study explores the potential impacts of microbes deposited into the surface seawater of the southeastern Mediterranean Sea (SEMS along with atmospheric particles on marine autotrophic and heterotrophic production. We compared in situ changes in autotrophic and heterotrophic microbial abundance and production rates before and during an intense dust storm event in early September 2015. Additionally, we measured the activity of microbes associated with atmospheric dry deposition (also referred to as airborne microbes in sterile SEMS water using the same particles collected during the dust storm. A high diversity of prokaryotes and a low diversity of autotrophic eukaryotic algae were delivered to surface SEMS waters by the storm. Autotrophic airborne microbial abundance and activity were low, contributing ~1% of natural abundance in SEMS water and accounting for 1-4% to primary production. Airborne heterotrophic bacteria comprised 30-50% of the cells and accounted for 13-42% of bacterial production. Our results demonstrate that atmospheric dry deposition may supply not only chemical constitutes but also microbes that can affect ambient microbial populations and their activity in the surface ocean. Airborne microbes may play a greater role in ocean biogeochemistry in the future in light of the expected enhancement of dust storm durations and frequencies due to climate change and desertification processes.

  9. An improved parameterisation of ozone dry deposition to the ocean and its impact in a global climate-chemistry model

    Science.gov (United States)

    Luhar, Ashok K.; Galbally, Ian E.; Woodhouse, Matthew T.; Thatcher, Marcus

    2017-03-01

    Schemes used to parameterise ozone dry deposition velocity at the oceanic surface mainly differ in terms of how the dominant term of surface resistance is parameterised. We examine three such schemes and test them in a global climate-chemistry model that incorporates meteorological nudging and monthly-varying reactive-gas emissions. The default scheme invokes the commonly used assumption that the water surface resistance is constant. The other two schemes, named the one-layer and two-layer reactivity schemes, include the simultaneous influence on the water surface resistance of ozone solubility in water, waterside molecular diffusion and turbulent transfer, and a first-order chemical reaction of ozone with dissolved iodide. Unlike the one-layer scheme, the two-layer scheme can indirectly control the degree of interaction between chemical reaction and turbulent transfer through the specification of a surface reactive layer thickness. A comparison is made of the modelled deposition velocity dependencies on sea surface temperature (SST) and wind speed with recently reported cruise-based observations. The default scheme overestimates the observed deposition velocities by a factor of 2-4 when the chemical reaction is slow (e.g. under colder SSTs in the Southern Ocean). The default scheme has almost no temperature, wind speed, or latitudinal variations in contrast with the observations. The one-layer scheme provides noticeably better variations, but it overestimates deposition velocity by a factor of 2-3 due to an enhancement of the interaction between chemical reaction and turbulent transfer. The two-layer scheme with a surface reactive layer thickness specification of 2.5 µm, which is approximately equal to the reaction-diffusive length scale of the ozone-iodide reaction, is able to simulate the field measurements most closely with respect to absolute values as well as SST and wind-speed dependence. The annual global oceanic deposition of ozone determined using this

  10. High mercury wet deposition at a “clean Air” site in Puerto Rico

    Science.gov (United States)

    Shanley, James B.; Engle, Mark A.; Scholl, Martha A.; Krabbenhoft, David P.; Brunette, Robert; Olson, Mark L.; Conroy, Mary E.

    2015-01-01

    Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds, during two complete years the site averaged 27.9 μg m–2 yr–1 wet Hg deposition, or about 30% more than Florida and the Gulf Coast, the highest deposition areas within the U.S. These high Hg deposition rates are driven in part by high rainfall, which averaged 2855 mm yr–1. The volume-weighted mean Hg concentration was 9.8 ng L–1, and was highest during summer and lowest during the winter dry season. Rainout of Hg (decreasing concentration with increasing rainfall depth) was minimal. The high Hg deposition was not supported by gaseous oxidized mercury (GOM) at ground level, which remained near global background concentrations (<10 pg m–3). Rather, a strong positive correlation between Hg concentrations and the maximum height of rain detected within clouds (echo tops) suggests that droplets in high convective cloud tops scavenge GOM from above the mixing layer. The high wet Hg deposition at this “clean air” site suggests that other tropical areas may be hotspots for Hg deposition as well.

  11. Parameterization of gaseous dry deposition in atmospheric chemistry models: Sensitivity to aerodynamic resistance formulations under statically stable conditions

    Science.gov (United States)

    Toyota, Kenjiro; Dastoor, Ashu P.; Ryzhkov, Andrei

    2016-12-01

    Turbulence controls the vertical transfer of momentum, heat and trace constituents in the atmospheric boundary layer. In the lowest 10% of this layer lies the surface boundary layer (SBL) where the vertical fluxes of transferred quantities have been successfully parameterized using the Monin-Obukhov similarity theory in weather forecast, climate and atmospheric chemistry models. However, there is a large degree of empiricism in the stability-correction parameterizations used to formulate eddy diffusivity and aerodynamic resistance particularly under strongly stable ambient conditions. Although the influence of uncertainties in stability-correction parameterizations on eddy diffusivity is actively studied in boundary-layer meteorological modeling, its impact on dry deposition in atmospheric chemistry modeling is not well characterized. In this study, we address this gap by providing the mathematical basis for the relationship between the formulations of vertical surface flux used in meteorological and atmospheric chemistry modeling communities, and by examining the sensitivity of the modeled dry deposition velocities in statically stable SBL to the choice of stability-correction parameterizations used in three operational and/or research environmental models (GEM/GEM-MACH, ECMWF IFS and CMAQ-MM5). Aerodynamic resistances (ra) calculated by the three sets of parameterizations are notably different from each other and are also different from those calculated by a "z-less" scaling formulation under strongly stable conditions (the bulk Richardson number > 0.2). Furthermore, we show that many atmospheric chemistry models calculate ra using formulations which are inconsistent with the derivation of micro-meteorological parameters. Finally, practical implications of the differences in stability-correction algorithms are discussed for the computations of dry deposition velocities of SO2, O3 and reactive bromine compounds for specific cases of stable SBL.

  12. Seasonal variations in metallic mercury (Hg0) vapor exchange over biannual wheat-corn rotation cropland in the North China Plain

    Science.gov (United States)

    Sommar, Jonas; Zhu, Wei; Shang, Lihai; Lin, Che-Jen; Feng, Xinbin

    2016-04-01

    Air-surface gas exchange of Hg0 was measured in five approximately bi-weekly campaigns (in total 87 days) over a wheat-corn rotation cropland located on the North China Plain (NCP) using the relaxed eddy accumulation (REA) technique. The campaigns were separated over the duration of a full-year period (2012-2013) aiming to capture the flux pattern over essential growing stages of the planting system with a low homogeneous topsoil Hg content ( ˜ 45 ng g-1). Contrasting pollution regimes influenced air masses at the site and corresponding Hg0 concentration means (3.3 in late summer to 6.2 ng m-3 in winter) were unanimously above the typical hemispheric background of 1.5-1.7 ng m-3 during the campaigns. Extreme values in bi-directional net Hg0 exchange were primarily observed during episodes of peaking Hg0 concentrations. In tandem with under-canopy chamber measurements, the above-canopy REA measurements provided evidence for a balance between Hg0 ground emissions and uptake of Hg0 by the developed canopies. During the wheat growing season covering ˜ 2 / 3 of the year at the site, net field-scale Hg0 emission prevailed for periods of active plant growth until canopy senescence (mean flux: 20.0 ng m-3), showing the dominance of Hg0 soil efflux during warmer seasons. In the final vegetative stage of corn and wheat, ground and above-canopy Hg0 flux displayed inversed daytime courses with a near mid-day maximum (emission) and minimum (deposition), respectively. In contrast to wheat, Hg0 uptake of the corn canopy at this stage offset ground Hg0 emissions with additional removal of Hg0 from the atmosphere. Differential uptake of Hg0 between wheat (C3 species) and corn (C4 species) foliage is discernible from estimated Hg0 flux (per leaf area) and Hg content in mature cereal leaves, being a factor of > 3 higher for wheat (at ˜ 120 ng g-1 dry weight). Furthermore, this study shows that intermittent flood irrigation of the air-dry field induced a short pulse of Hg0 emission

  13. Dry Deposition Velocity Estimation for the Savannah River Site: Part 2 -- Parametric and Site-Specific Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Napier, Bruce A.; Rishel, Jeremy P.; Cook, Kary M.

    2013-09-12

    Values for the dry deposition velocity of airborne particles were estimated with the GENII Version 2.10.1 computer code for the Savannah River site using assumptions about surface roughness parameters and particle size and density. Use of the GENII code is recommended by the U.S. Department of Energy for this purpose. Meteorological conditions evaluated include atmospheric stability classes D, E, and F and wind speeds of 0.5, 1.0, 1.5, and 2.0 m/s. Local surface roughness values ranging from 0.03 to 2 meters were evaluated. Particles with mass mean diameters of 1, 5, and 10 microns and densities of 1, 3, 4, and 5 g/cm3 were evaluated. Site specific meteorology was used to predict deposition velocity for Savannah River conditions for a range of distances from 670 to 11,500 meters.

  14. Synthesis and characterization of HgI2 nanoparticles for films nucleation

    Science.gov (United States)

    Barthaburu, María Pérez; Galain, Isabel; Mombrú, Maia; Aguiar, Ivana; Olivera, Alvaro; Pereira, Heinkel Bentos; Fornaro, Laura

    2017-01-01

    With the aim of controlling the first steps in HgI2 film growth onto amorphous substrates, we employed HgI2 nanoparticles for nucleation. Hg(NO3)2 and NaI were used for obtaining HgI2 in water with and without citric or oxalic acid as capping agents. These samples were then subjected to a hydrothermal treatment at a constant temperature of 120 ºC during 2 h. All samples were washed, centrifuged and dried. This method presents a facile route for obtaining HgI2 nanoparticles and is easily scalable. HgI2 tetragonal phase was confirmed by powder X-ray diffraction. Nanoparticles were characterized in their size and morphology by transmission electron microscopy and the capping agent presence was studied by infrared spectroscopy. HgI2 nanoparticles synthesized in octadecene, previously reported, as well as nanoparticles obtained in the present work, were used for nucleation onto amorphous substrates. They were deposited onto floating silica glass by spin coating and the morphology of the layer was studied by atomic force microscopy. The results we obtained are the first involving HgI2 nucleation by spin coating, and are very promising for improving the film growth orientation and therefore the current applications of this material, as well as for opening new ones.

  15. Quantifying the dry deposition of ammonia in ammonia-rich and ammonia-poor environments using a surrogate surface approach

    Science.gov (United States)

    Moumen, Nadjoua; Yi, Seung-Muk; Raymond, Heather A.; Han, YoungJi; Holsen, Thomas M.

    In this study, dry deposition samples were collected with both an aerodynamically smooth water surface (WSS) and a knife-edge surrogate surface (KSS) in Potsdam, NY, Solomons, MD, and at a farm in upstate NY intermittently between March 2000 and August 2001. The WSS and the citric acid-coated paper filter on the KSS were used to measure total ammonium deposition (NH 3 and p-NH 4+), while a greased Mylar disk on the KSS was used to measure particulate NH 4+ (p-NH 4+) deposition. An annular denuder system (ADS) was used to measure NH 3 gas phase and particulate NH 4+ concentrations. In side-by-side experiments with two WSSs, no statistical difference was found between simultaneously measured total ammonium deposition at any of the sites. Average total NH 3 fluxes measured with the WSS in Potsdam, Solomons, and at the farm were 3.1, 2.1, and 310 mg NH 4+ m -2 day -1, respectively. Similarly gaseous NH 3 fluxes measured with the citric acid-coated paper on the KSS were 3.6, 2.1, and 500 mg NH 4+m -2 day -1, respectively. The p-NH 4+ fluxes to the KSS-greased strip were negligible at all three locations. Fluxes measured by the citric acid paper filters were slightly greater than those measured with the WSS suggesting that the acidic dry surfaces had a higher affinity for ammonia than the water in the WSS. The average gas-phase ammonia concentrations in Potsdam, Solomons, MD and at the farm were 0.60×10 -3, 2.1×10 -3, and 0.25 mg NH 4+ m -3, respectively. The average ammonium concentrations were 0.50×10 -3, 1.2×10 -3, and 14×10 -3 mg NH 4+ m -3, respectively.

  16. The influence of regional circulation patterns on wet and dry mineral dust and sea salt deposition over Greenland

    Energy Technology Data Exchange (ETDEWEB)

    Hutterli, M.A. [University of Bern, Physics Institute, Bern (Switzerland); British Antarctic Survey, Physical Sciences Division, Cambridge (United Kingdom); Crueger, T. [Max-Planck-Institute for Meteorology, Hamburg (Germany); Fischer, H. [Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven (Germany); Andersen, K.K.; Siggaard-Andersen, M.L. [University of Copenhagen, Niels Bohr Institute, Copenhagen (Denmark); Raible, C.C.; Stocker, T.F. [University of Bern, Physics Institute, Bern (Switzerland); McConnell, J.R. [Desert Research Institute, Reno, NV (United States); Bales, R.C.; Burkhart, J.F. [University of California, Merced, Atwater, CA (United States)

    2007-05-15

    Annually resolved ice core records from different regions over the Greenland ice sheet (GrIS) are used to investigate the spatial and temporal variability of calcium (Ca{sup 2+}, mainly from mineral dust) and sodium (Na{sup +}, mainly from sea salt) deposition. Cores of high common inter-annual variability are grouped with an EOF analysis, resulting in regionally representative Ca{sup 2+} and Na{sup +} records for northeastern and central Greenland. Utilizing a regression and validation method with ERA-40 reanalysis data, these common records are associated with distinct regional atmospheric circulation patterns over the North American Arctic, Greenland, and Central to Northern Europe. These patterns are interpreted in terms of transport and deposition of the impurities. In the northeastern part of the GrIS sea salt records reflect the intrusion of marine air masses from southeasterly flow. A large fraction of the Ca{sup 2+} variability in this region is connected to a circulation pattern suggesting transport from the west and dry deposition. This pattern is consistent with the current understanding of a predominantly Asian source of the dust deposited over the GrIS. However, our results also indicate that a significant fraction of the inter-annual dust variability in NE and Central Greenland is determined by the frequency and intensity of wet deposition during the season of high atmospheric dust loading, rather than representing the variability of the Asian dust source and/or long-range transport to Greenland. The variances in the regional proxy records explained by the streamfunction patterns are high enough to permit reconstructions of the corresponding regional deposition regimes and the associated circulation patterns. (orig.)

  17. Dry deposition of sulphur at a high-altitude background station in South Africa

    CSIR Research Space (South Africa)

    Zunckel, M

    1999-10-01

    Full Text Available and cool nights were experienced during the summer campaign with convective afternoon or evening showers on six occasions. No rain fell during the typically dry winter campaign when cool days and cold nights were experienced. Mean global radiation for the 2...

  18. Overcoming Etch Challenges on a 6″ Hg1- x Cd x Te MBE on Si Wafer

    Science.gov (United States)

    Apte, Palash; Norton, Elyse; Robinson, Solomon

    2017-10-01

    The effect of increasing photoresist (PR) thickness on the inductively coupled plasma (ICP) dry etched characteristics of a 6″ (c.15 cm) molecular beam epitaxy Hg1- x Cd x Te/Si wafer is investigated. It is determined that the Hg1- x Cd x Te etch rate (ER) does not vary significantly with a change in the PR thickness. Also, the vertical ER of the PR is seen to be independent of the PR thickness, but the lateral ER is seen to reduce significantly with increased PR thickness. Indeed, very little reduction in the pixel mesa area post-dry etch is seen for the thicker PR. Consequently, the trench sidewall angle is also seen to vary as a function of the PR thickness. Since ICP is the more attractive choice for dry etching Hg1- x Cd x Te, this simple, cost-effective way to extend the capabilities of dry etching (larger mesa top area post-dry etch, ability to create tailor-made trench sidewall angles for optimal conformal passivation deposition, and potential for reduced dry etch damage) described here would allow for the fabrication of next generation infrared detectors with increased yield and reduced cost. Although similar results have been presented using the electron cyclotron resonance system to dry etch Hg1- x Cd x Te, to the best of our knowledge, this is the first time that such results have been presented using an ICP system.

  19. SEASONAL CHARACTERIZATION OF DUST DAYS,MASS CONCENTRATION AND DRY DEPOSITION OF ATMOSPHERIC AEROSOLS OVER QINGDAO, CHINA

    Institute of Scientific and Technical Information of China (English)

    Renjian Zhang; Mingxing Wang; Lifang Sheng; Yutaka Kanai; Atsuyuki Ohta

    2004-01-01

    The seasonal characterization of dust days, mass concentration and dry deposition of atmospheric aerosols were investigated using the historical data of dust days observed over Qingdao during the period from 1961 to 2001and ground-based aerosol sampling data collected in the period from May 2001 to November 2002. In Qingdao most of the dust days occurred in spring and in winter and no dust days existed in summer. The seasonal variation of the uplifting dust day over Qingdao was in phase with that analyzed over North China. The mean mass concentration of the total values and phase of the seasonal oscillation for fine particles were very similar to those for coarse particles except for the month March, during which the concentration of the coarse particles was about 4 times as high as that of the fine particles. Comparison between seasonal variation of mass concentration of aerosols and dust days indicated that high frequency of uplifting dust day was accompanied by high TSP mass concentration. The TSP mass concentration measured by the low-volume instrument was about 30% lower than that measured by high-volume instrument, though the two data sets are highly correlated (correlation coefficient=0.89). The dry deposition flux during the observation period from as that over Beijing.

  20. Neutral and ionic per- and polyfluoroalkyl substances (PFASs) in atmospheric and dry deposition samples over a source region (Tianjin, China).

    Science.gov (United States)

    Yao, Yiming; Chang, Shuai; Sun, Hongwen; Gan, Zhiwei; Hu, Hongwei; Zhao, Yangyang; Zhang, Yufen

    2016-05-01

    Per- and polyfluoroalkyl substances (PFASs) were detected in the atmosphere of a source region in Tianjin, China. Fluorotelomer alcohols (FTOHs) were the dominant neutral PFASs in the atmosphere with total concentrations of 93.6-131 pg/m(3) and 8:2 FTOH contributing the most, whereas perfluorooctane sulfonamide derivatives (PFOSAs) were two magnitudes lower or undetected. In comparison, ionic PFASs (perfluoroalkyl carboxyl acids (PFCAs)) in the atmosphere were detected at similar or even higher levels. At wastewater treatment plants (WWTPs), the air over influent was found with higher levels of FTOHs than over aeration tank and effluent; whereas in the air over the aeration tank, the concentrations of PFOSAs and nonvolatile ionic PFASs substantially increased, suggesting a possible direct release of ionic PFASs to the atmosphere besides the atmospheric conversion from volatile precursors. In the air phase, a low proportion (1-5%) of PFCAs was subjected to dry deposition in the source region. Interestingly, the dry-deposition-to-bulk-air ratios of PFCA analogues were the lowest at medium chain lengths (C8 and C9) and increased with either shorter or longer chain length. The extraordinary affinity of shorter-chain PFCAs (C6-C7) to particles was presumed to be due to their smaller molecular size favoring the interactions between the carboxyl head groups and specific sorption sites on particulate matter.

  1. The atmospheric pollution in the area of the Goczałkowice Reservoir changes based on wet and dry deposition

    Directory of Open Access Journals (Sweden)

    Mieczysław LEŚNIOK

    2014-11-01

    Full Text Available The Goczałkowice Reservoir was formed as a result of the accumulation of waters from the Vistula River caused by the construction of the earth dam of 2980 m in length between the town of Goczałkowice-Zdrój and Zabrzeg. It is located in Subcaprathia, near the Silesian Beskids mountain range (Outer Western Carpathians. Discussed reservoir was investigated in several environmental aspects. One of those researched elements was wet and dry pollution deposition in Integrated System Supporting Management and Protection of Water Reservoir (ZiZOZap.The research on wet and dry pollution deposition was carried out at two measurement points situated on the opposite sides of the Goczałkowice Reservoir. From the east side it was a station in Goczałkowice and from the west side a station in Frelichów (fig. 1.  The location of points allowed to assess influence of air masses from different directions and define sources of the pollutants.

  2. Estimation of the Total Dust Column and Dry Deposition Flux over the Yellow Sea, China Based on Shipboard Sun Photometer Measurements: Case Study

    Institute of Scientific and Technical Information of China (English)

    YANG Dong-Xu; LIU Yi; CHEN Wen-Zhong

    2010-01-01

    The total dust column and the dry deposition flux were calculated based on the optical properties that were measured by a shipboard sun photometer POM-01 MK Ⅱ in a cloud-free and nonfrontal dust condition on 24 April 2006. The total dust column was calculated by using an integration method of the particle size distribution; the mean value was 1.42±0.30 g m-2. A linear correlation between the total dust column and the aerosol optical depth (AOD) with a linear factor of 2.7 g m-2 over the Sahara was applied to calculate the total dust column in this study; the results were lower than these calculated by the integration method. A reasonable factor of 3.2 g m-2 was achieved by minimizing the standard deviation (SD) of the two methods. The two layers model, which includes the deposition processes of turbulent transfer, Brownian diffusion, impaction and gravitational settling over the sea's surface, was used to calculate the dry deposition flux; the mean value was 5.05±2.49 μg m-2 s-1. A correlation among the total dust column, dry deposition flux, AOD, and effective radius was discussed. The correlation between the total dust column and the AOD was better than that between the total dust column and the effective radius; however, the correlation between the dry deposition flux and the effective radius was better than that between the dry deposition flux and the AOD.

  3. Three air quality studies: Great Lakes ozone formation and nitrogen dry deposition; and Tucson aerosol chemical characterization

    Science.gov (United States)

    Foley, Theresa

    (arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, and nickel) in the southern Tucson metropolitan area. A Tucson company that uses beryllium oxide to manufacture thermally conductive ceramics has prompted strong citizen concern. This study found that the study area has good air quality with respect to PM10 and metals, with ambient concentrations meeting US Environmental Protection Agency and World Health Organization standards. Beryllium was detected only once (during a dust storm) and was ascribed to naturally-occurring beryllium in the suspended soil. The third paper (to be submitted to the Journal of Great Lakes Research) studies nitrogen dry deposition over Lake Michigan and Lake Superior. Numerous studies have shown that wet and dry deposition of nitrogen has contributed to the eutrophication of coastal waters and declining productivity of marine fisheries. Nitrogen dry deposition over the Great Lakes themselves, as opposed to the shorelines, has not been documented in the peer-reviewed literature. This paper calculates nitrogen dry deposition over Lake Michigan and Lake Superior, using aircraft measurements from the LADCO Aircraft Study, and finds that over-water, nitrogen dry deposition is a significant source of nitrogen to Lake Michigan and Lake Superior.

  4. Even low to medium nitrogen deposition impacts vegetation of dry, coastal dunes around the Baltic Sea

    NARCIS (Netherlands)

    Remke, E.; Brouwer, E.; Kooijman, A.; Blindow, I.; Esselink, H.; Roelofs, J.G.M.

    2009-01-01

    Coastal dunes around the Baltic Sea have received small amounts of atmospheric nitrogen and are rather pristine ecosystems in this respect. In 19 investigated dune sites the atmospheric wet nitrogen deposition is 3-8 kg N ha−1 yr−1. The nitrogen content of Cladonia portentosa appeared to be a suitab

  5. Effect of dry air on interface smoothening in reactive sputter deposited Co/Ti multilayer

    Science.gov (United States)

    Biswas, A.; Porwal, A.; Bhattacharya, Debarati; Prajapat, C. L.; Ghosh, Arnab; Nand, Mangla; Nayak, C.; Rai, S.; Jha, S. N.; Singh, M. R.; Bhattacharyya, D.; Basu, S.; Sahoo, N. K.

    2017-09-01

    Top surface roughness and interface roughness are one of the key elements which determine the performance of X-ray and neutron thin film multilayer devices. It has been observed that by mixing air with argon in sputtering ambience during deposition of Co layers, polarized neutron reflectivity (PNR) of Co/Ti supermirror polarizers can be improved substantially. Cross-sectional HRTEM measurement reveals that sharper interfaces in the supermirror can be achieved in case of deposition of the multilayer under mixed ambience of argon and air. In order to investigate this interface modification mechanism further, in this communication two sets of tri-layer Co/Ti/Co samples and 20-layer Co/Ti periodic multilayer samples have been prepared; in one set all the layers are deposited only under argon ambience and in the other set, Co layers are deposited under a mixed ambience of argon and air. These samples have been characterized by measuring specular and non-specular X-ray reflectivities (GIXR) with X-rays of 1.54 Å wavelength and polarized neutron reflectivity (PNR) with neutron of 2.5 Å wavelength at grazing angle of incidence. It has been observed that the X-ray and neutron specular reflectivities at Bragg peaks of 20 layer periodic multilayer increase when Co layers are deposited under mixed ambience of argon and air. The detail information regarding the effect of air on the interfaces and magnetic properties has been obtained by fitting the measured spectra. The above information has subsequently been supplemented by XRD and magnetic measurements on the samples. XPS and XANES measurements have also been carried out to investigate whether cobalt oxide or cobalt nitride layers are being formed due to use of air in sputtering ambience.

  6. Ring deposition of drying suspension droplets%溶液液滴蒸发变干的环状沉积

    Institute of Scientific and Technical Information of China (English)

    张文彬; 廖龙光; 于同旭; 纪爱玲

    2013-01-01

    Deposition of colloidal particles in a drying droplet is important in many scientific researches and technological applications. In this work, the ring deposition of drying droplets on a solid substrate is investigated experimentally at a microscopic level. A ring deposition is formed at the contact line as the water solution droplet containing SiO2 particles is drying, just like the formation of coffee ring. Contact line pinning is crucial to the ring deposition formation. There will be a replenish flow in the droplet towards the edge, and the particles are driven to the contact line, deposited on the substrate. As the particle mass fraction is large, the particles which are left inside the spot, when the droplet dries out, may form a single particle layer, packing in order. The contact angle of the droplet on glass substrate is very small, the SiO2 particles will gather at the rim of the droplet, which initially form a chain along the contact line. As more particles come to the rim, they are deposited in a line by line way to form a 2D close packing. Since the contact angle decreases with evaporation when the contact line is pinned, a capillary force between liquid surface and particles arises once the height of droplet surface near the contact line is lower than that of the particle, pushing the particles to move inward. The effect on the larger particles is more pronounced-it even leads to a separation of the particles, with the smaller ones at the outer side.%液体蒸发驱动的颗粒自组装现象在许多的工业技术中有重要应用。本文利用显微镜观测含有颗粒物质的液滴变干后留在固体表面的颗粒形成的环状沉积图案。采用微米粒径的SiO2小球水溶液液滴蒸发变干模拟咖啡环的形成过程,结果发现液滴蒸发过程中接触线的钉扎是环状沉积的必要条件。在液滴蒸发过程中颗粒随着补偿流不断的向液滴边缘移动,聚集在接触线处形成环。液滴蒸发变

  7. Development and validation of a size-resolved particle dry deposition scheme for application in aerosol transport models

    Directory of Open Access Journals (Sweden)

    A. Petroff

    2010-12-01

    Full Text Available A size-resolved particle dry deposition scheme is developed for inclusion in large-scale air quality and climate models where the size distribution and fate of atmospheric aerosols is of concern. The "resistance" structure is similar to what is proposed by Zhang et al. (2001, while a new "surface" deposition velocity (or surface resistance is derived by simplification of a one-dimensional aerosol transport model (Petroff et al., 2008b, 2009. Compared to Zhang et al.'s model, the present model accounts for the leaf size, shape and area index as well as the height of the vegetation canopy. Consequently, it is more sensitive to the change of land covers, particularly in the accumulation mode (0.1–1 micron. A drift velocity is included to account for the phoretic effects related to temperature and humidity gradients close to liquid and solid water surfaces. An extended comparison of this model with experimental evidence is performed over typical land covers such as bare ground, grass, coniferous forest, liquid and solid water surfaces and highlights its adequate prediction. The predictions of the present model differ from Zhang et al.'s model in the fine mode, where the latter tends to over-estimate in a significant way the particle deposition, as measured by various investigators or predicted by the present model. The present development is thought to be useful to modellers of the atmospheric aerosol who need an adequate parameterization of aerosol dry removal to the earth surface, described here by 26 land covers. An open source code is available in Fortran90.

  8. Plant hydraulic responses to long-term dry season nitrogen deposition alter drought tolerance in a Mediterranean-type ecosystem.

    Science.gov (United States)

    Pivovaroff, Alexandria L; Santiago, Louis S; Vourlitis, George L; Grantz, David A; Allen, Michael F

    2016-07-01

    Anthropogenic nitrogen (N) deposition represents a significant N input for many terrestrial ecosystems. N deposition can affect plants on scales ranging from photosynthesis to community composition, yet few studies have investigated how changes in N availability affect plant water relations. We tested the effects of N addition on plant water relations, hydraulic traits, functional traits, gas exchange, and leaf chemistry in a semi-arid ecosystem in Southern California using long-term experimental plots fertilized with N for over a decade. The dominant species were Artemisia california and Salvia mellifera at Santa Margarita Ecological Reserve and Adenostoma fasciculatum and Ceanothus greggii at Sky Oaks Field Station. All species, except Ceanothus, showed increased leaf N concentration, decreased foliar carbon to N ratio, and increased foliar N isotopic composition with fertilization, indicating that added N was taken up by study species, yet each species had a differing physiological response to long-term N addition. Dry season predawn water potentials were less negative with N addition for all species except Adenostoma, but there were no differences in midday water potentials, or wet season water potentials. Artemisia was particularly responsive, as N addition increased stem hydraulic conductivity, stomatal conductance, and leaf carbon isotopic composition, and decreased wood density. The alteration of water relations and drought resistance parameters with N addition in Artemisia, as well as Adenostoma, Ceanothus, and Salvia, indicate that N deposition can affect the ability of native Southern California shrubs to respond to drought.

  9. High concentrations and dry deposition of reactive nitrogen species at two sites in the North China Plain

    Energy Technology Data Exchange (ETDEWEB)

    Shen, J.L.; Tang, A.H.; Liu, X.J.; Fangmeier, A.; Goulding, K.T.W.; Zhang, F.S. [China Agricultural University, Beijing (China)

    2009-11-15

    Atmospheric concentrations of major reactive nitrogen (N{sub r}) species were quantified using passive samplers, denuders, and particulate samplers at Dongbeiwang and Quzhou, North China Plain (NCP) in a two-year study. Average concentrations of NH{sub 3}, NO{sub 2}, HNO{sub 3}, pNH{sub 4}{sup +} and pNO{sub 3}{sup -} were 12.0, 12.9, 0.6, 10.3, and 4.7 {mu} g N m{sup -3} across the two sites, showing different seasonal patterns of these N, species. For example, the highest NH{sub 3} concentration occurred in summer while NO{sub 2} concentrations were greater in winter, both of which reflected impacts of N fertilization (summer) and coal-fueled home heating (winter). Based on measured N{sub r} concentrations and their deposition velocities taken from the literature, annual N dry deposition was up to 55 kg N ha{sup -1}. Such high concentrations and deposition rates of N{sub r} species in the NCP indicate very serious air pollution from anthropogenic sources and significant atmospheric N input to crops.

  10. Development and validation of a size-resolved particle dry deposition scheme for applications in aerosol transport models

    Directory of Open Access Journals (Sweden)

    A. Petroff

    2010-08-01

    Full Text Available A size-resolved particle dry deposition scheme is developed, which has been designed for inclusion in large-scale air quality and climate models, where the size distribution and fate of the atmospheric aerosol is of concern. The "resistance" structure is similar to what is proposed by Zhang et al. (2001, 2003, while a new "surface" deposition velocity (or surface resistance is derived by simplification of a one-dimensional aerosol transport model (Petroff et al., 2008b, 2009. Collection efficiencies are given for the 26 Land Use Categories that decribe the earth surface. Validation of this model with existing measurements is performed on desert, grass, coniferous forest and liquid water surfaces. A comparison of this model with measurements on snow and ice is also given. Even though a qualitative agreement is reached, further size-segegated measurements are needed in order to confirm the model accuracy on this surface. The present analytical model provides more accurate predictions of the aerosol deposition on these surfaces than previous models.

  11. Mechanism of carbon deposit/removal in methane dry reforming on supported metal catalysts

    NARCIS (Netherlands)

    Nagaoka, K.; Seshan, K.; Lercher, J.A.; Aika, A.; Iglesia, E.; Spivey, J.J.; Fleisc, T.H.

    2001-01-01

    The greater resistance to coke deposition for Pt/ZrO2 compared to Pt/Al2O3 in the CH4/CO2 reaction has been attributed to the higher reactivity of coke with CO2 on Pt/ZrO2 [1]. Hence, in this communication, the reaction of coke derived from methane (CHx: which is an intermediated in the reforming re

  12. Mechanism of carbon deposit - removal in methane dry reforming on supported metal catalysts

    NARCIS (Netherlands)

    Nagaoka, K.; Nagaoka, K.; Seshan, Kulathuiyer; Lercher, J.A.; Aika, A.; Iglesia, E.; Spivey, J.J.; Fleisc, T.H.

    2001-01-01

    The greater resistance to coke deposition for Pt/ZrO2 compared to Pt/Al2O3 in the CH4/CO2 reaction has been attributed to the higher reactivity of coke with CO2 on Pt/ZrO2 [1]. Hence, in this communication, the reaction of coke derived from methane (CHx: which is an intermediated in the reforming re

  13. A multipoint (49 points) study of dry deposition of polycyclic aromatic hydrocarbons (PAHs) in Erzurum, Turkey by using surrogated snow surface samplers.

    Science.gov (United States)

    Bayraktar, Hanefi; Paloluoğlu, Cihan; Turalioğlu, Fatma S; Gaga, Eftade O

    2016-06-01

    Dry deposition of atmospheric 18 polycyclic aromatic hydrocarbon (PAH) components was investigated in the scope of the study by using surrogate snow samplers at 49 different sampling points in and around the city center of Erzurum, Turkey. Snow was sampled twice, the first of which was taken immediately after the first fresh snow cover and placed into aluminum trays to obtain dry deposition surface while the second sample was taken from the snow cover (accumulated snow) exposed to an 8-day dry deposition period and then analyzed and extracted. All the samples taken from the samplers were extracted using solid and liquid phase extraction and analyzed through GC-MS. It was observed that at the end of an 8-day dry period, snow samples enriched 5.5 times more in PAH components than the baseline. PAH deposition was determined to be influenced mainly by coal, mixed source, traffic, diesel fuel, and petrol fuel at 43, 27, 20, 8, and 2 % of sampling points, respectively. Local polluting sources were found to be effective on the spatial distribution of dry deposition of PAH components in urban area.

  14. Partitioning and granulometric distribution of metal leachate from urban traffic dry deposition particulate matter subject to acidic rainfall and runoff retention.

    Science.gov (United States)

    Sansalone, J; Ying, G

    2008-09-01

    Vehicular transportation coupled with urban hydrology is a significant source as well as vector of particulate matter (PM) and particulate-bound metal inventories in urban systems. This study examines the granulometric distribution of metals from dry deposition PM generated from 17 dryfall periods and equilibrium metal partitioning with runoff PM distribution from eight rainfall-runoff events at an urban inter-state watershed in Baton Rouge, LA. Dry deposition PM is a coarse non-uniform gradation with a d(50 m)=304 microm and a peak surface area at 106 microm. Results indicate acid rain is not a significant metal contributor to runoff but is capable of leaching metals from PM to runoff. Retained runoff partitioning resulted in particulate-bound predominance for As, Cd, Cr, Cu, Pb, and Zn while Ca and Mg remained predominately dissolved. The finer PM fraction (75 microm). This coarse fraction is also the most labile when exposed to acidic rainfall; generating up to 90% of the total metal mass leached from the entire PM gradation. Comparing dry deposition and runoff PM of equal mass and size gradation, retained runoff PM is enriched with metals (except Pb). Results indicate the labile coarse fraction of dry deposition PM can be a significant source of metal leaching while runoff PM (mobilized dry deposition PM) stored in a BMP can be metal-enriched with the potential for re-leaching or scour.

  15. GNAQPMS-Hg v1.0, a global nested atmospheric mercury transport model: model description, evaluation and application to trans-boundary transport of Chinese anthropogenic emissions

    Directory of Open Access Journals (Sweden)

    H. S. Chen

    2014-10-01

    Full Text Available Atmospheric mercury (Hg is a toxic pollutant and can be transported over the whole globe due to its long lifetime in the atmosphere. For the purpose of assessing Hg hemispheric transport and better characterizing regional Hg pollution, a global nested atmospheric Hg transport model (GNAQPMS-Hg has been developed. In GNAQPMS-Hg, the gas and aqueous phase Hg chemistry representing the transformation among three forms of Hg: elemental mercury (Hg(0, divalent mercury (Hg(II, and primary particulate mercury (Hg(P are calculated. A detailed description of the model, including mercury emissions, gas and aqueous phase chemistry, and dry and wet deposition is given in this study. Worldwide observations including extensive data in China have been collected for model evaluation. Comparison results show that the model reasonably simulates the global mercury budget and the spatial–temporal variation of surface mercury concentrations and deposition. Overall, model predictions of annual total gaseous mercury (TGM and wet deposition agree with observations within a factor of two, and within a factor of five for oxidized mercury and dry deposition. The model performs significantly better in North America and Europe than in East Asia. This can probably be attributed to the large uncertainties in emission inventories, coarse model resolution and to the inconsistency between the simulation and observation periods in East Asia. Compared to the global simulation, the nested simulation shows improved skill at capturing the high spatial variability of Hg concentrations and deposition over East Asia. In particular, the root mean square error (RMSE of simulated Hg wet deposition over East Asia is reduced by 24% in the nested simulation. Model sensitivity studies indicate that Chinese primary anthropogenic emissions account for 30 and 62% of surface mercury concentrations and deposition over China, respectively. Along the rim of the western Pacific, the contributions

  16. Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

    Science.gov (United States)

    Sprovieri, Francesca; Pirrone, Nicola; Bencardino, Mariantonia; D'Amore, Francesco; Angot, Helene; Barbante, Carlo; Brunke, Ernst-Günther; Arcega-Cabrera, Flor; Cairns, Warren; Comero, Sara; Diéguez, María del Carmen; Dommergue, Aurélien; Ebinghaus, Ralf; Feng, Xin Bin; Fu, Xuewu; Garcia, Patricia Elizabeth; Gawlik, Bernd Manfred; Hageström, Ulla; Hansson, Katarina; Horvat, Milena; Kotnik, Jože; Labuschagne, Casper; Magand, Olivier; Martin, Lynwill; Mashyanov, Nikolay; Mkololo, Thumeka; Munthe, John; Obolkin, Vladimir; Ramirez Islas, Martha; Sena, Fabrizio; Somerset, Vernon; Spandow, Pia; Vardè, Massimiliano; Walters, Chavon; Wängberg, Ingvar; Weigelt, Andreas; Yang, Xu; Zhang, Hui

    2017-02-01

    The atmospheric deposition of mercury (Hg) occurs via several mechanisms, including dry and wet scavenging by precipitation events. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, wet deposition samples were collected for approximately 5 years at 17 selected GMOS monitoring sites located in the Northern and Southern hemispheres in the framework of the Global Mercury Observation System (GMOS) project. Total mercury (THg) exhibited annual and seasonal patterns in Hg wet deposition samples. Interannual differences in total wet deposition are mostly linked with precipitation volume, with the greatest deposition flux occurring in the wettest years. This data set provides a new insight into baseline concentrations of THg concentrations in precipitation worldwide, particularly in regions such as the Southern Hemisphere and tropical areas where wet deposition as well as atmospheric Hg species were not investigated before, opening the way for future and additional simultaneous measurements across the GMOS network as well as new findings in future modeling studies.

  17. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    Directory of Open Access Journals (Sweden)

    U.S. Mbamara

    2016-06-01

    Full Text Available Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS and X-ray Diffraction (XRD. The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-face surfaces were examined to assess the wear dimension and failure mechanism. Both friction behavior and wear (in the ball counter-face were observed to be dependent on the crystallinity and thickness of the thin film coatings.

  18. Lecithin/TPGS-based spray-dried self-microemulsifying drug delivery systems: In vitro pulmonary deposition and cytotoxicity.

    Science.gov (United States)

    Ishak, Rania A H; Osman, Rihab

    2015-05-15

    The aim of the present work was to develop a new solid self-microemulsifying drug delivery system (SMEDDS) for the pulmonary delivery of the poorly water-soluble anti-cancer drug atorvastatin (AVT). Microemulsion (ME) was first developed using isopropyl myristate (IPM), a combination of 2 biocompatible surfactants: lecithin/d-α-tocopheryl polyethylene glycol succinate (TPGS) and ethanol as co-surfactant. Two types of lecithin with different phosphatidylcholine (PC) contents were compared. Phase diagram, physico-chemical characterization and stability studies were used to investigate ME region. Solid SMEDDS were then prepared by spray-drying the selected ME using a combination of carriers composed of sugars, leucine as dispersibility enhancer with or without polyethylene glycol (PEG) 6000. Yield, flow properties, particle size and in vitro pulmonary deposition were used to characterize the spray-dried powders. Reconstituted MEs were characterized in terms of morphology, particle size and size distribution. In vitro cytotoxicity study was undertaken on lung cancer cell line for the selected MEs and SD-SMEDDS formulae. Results showed that the most satisfactory MEs properties were obtained with 1:3 lecithin/TPGS, 1:1 lecithin/oil and 1:1 surfactant/co-surfactant ratios. A larger ME area was obtained with lecithin containing 100% PC compared to the less expensive lecithin containing 20% PC. By manipulating spray drying parameters, carrier composition and ratio of ME lipids to carrier, microparticles with more than 70% of respirable fraction could be prepared. The ME was efficiently recovered in simulated lung fluid even after removal of alcohol. The concurrent delivery of AVT with TPGS in solid SMEDDS greatly enhanced the cytotoxic activity on lung cancer cells. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Spreading and Deposit Characteristics of a Rapid Dry Granular Avalanche Across 3D Topography: Experimental Study

    Science.gov (United States)

    Wang, Yu-Feng; Xu, Qiang; Cheng, Qian-Gong; Li, Yan; Luo, Zhong-Xu

    2016-11-01

    Aiming to understand the propagation and deposit behaviours of a granular avalanche along a 3D complex basal terrain, a new 3D experimental platform in 1/400 scale was developed according to the natural terrain of the Xiejiadianzi rock avalanche, with a series of laboratory experiments being conducted. Through the conduction of these tests, parameters, including the morphological evolution of sliding mass, run-outs and velocities of surficial particles, thickness contour and centre of final deposit, equivalent frictional coefficient, and energy dissipation, are documented and analysed, with the geomorphic control effect, material grain size effect, drop angle effect, and drop distance effect on rock avalanche mobility being discussed primarily. From the study, some interesting conclusions for a better understanding of rock avalanche along a 3D complex basal topography are reached. (1) For the granular avalanche tested in this study, great differences between the evolutions of the debris along the right and left branch valleys were observed, with an obvious geomorphic control effect on avalanche mobility presented. In addition, some other interesting features, including groove-like trough and superelevation, were also observed under the control of the topographic interferences. (2) The equivalent frictional coefficients of the granular avalanches tested here range from 0.48 to 0.57, which is lower than that reached with a set-up composed of an inclined chute and horizontal plate and higher than that reached using a set-up composed of only an inclined chute. And the higher the drop angle and fine particle content, the higher the equivalent frictional coefficient. The effect of drop distance on avalanche mobility is minor. (3) For a granular avalanche, momentum transfer plays an important role in the motion of mass, which can accelerate the mobility of the front part greatly through delivering the kinetic energy of the rear part to the front.

  20. Dry-deposition measurements of sulfur dioxide to a spruce-fir forest in the Black Forest: a data report. Technical memo

    Energy Technology Data Exchange (ETDEWEB)

    McMillen, R.T.; Matt, D.R.; Hicks, B.B.; Womack, J.D.

    1987-02-01

    Measurements of dry deposition of SO/sub 2/ are reported for a forested site in the Black Forest of West Germany. The measurements were made using the eddy-correlation method about 10 meters above the top of a spruce forest that was already affected by Waldsterben. These measurements were conducted as one component of TULLA, a large sulfur mass-balance experiment. The dry-deposition measurements were successful during times when SO/sub 2/ concentrations were greater than 5 micro grams/cu m.

  1. ADVECTION - DIFFUSION NUMERICAL MODEL OF AN AIR POLLUTANT EMITTED FROM AN AREA SOURCE OF PRIMARY POLLUTANT WITH CHEMICAL REACTION AND DRY DEPOSITION

    Directory of Open Access Journals (Sweden)

    SUDHEER PAI K L

    2012-01-01

    Full Text Available A time dependent two dimensional advection-diffusion numerical model for primary pollutant with chemical reaction and dry deposition for an urban area is presented. The proposed numerical model takes into account of realistic form of variable wind velocity and eddy diffusivity profiles. The partial differential equation of primarypollutant is solved by using Crank-Nicolson implicit finite difference technique. The results are plotted for concentration of primary pollutant and the effect of chemical reaction and dry deposition on the dispersion of pollutant are analysed extensively.

  2. Deposition of nanostructured YSZ coating from spray-dried particles with no heat treatment

    Science.gov (United States)

    Zhao, Yan; Gao, Yang

    2015-08-01

    Ytrria stabilized zirconia (YSZ) nanoparticle agglomerates were fabricated by a spray dry method and were directly sprayed using atmospheric plasma spraying (APS) with a current of 300 A and 500 A. A commercially supplied nanostructured YSZ powder (sintered) was also sprayed under the same conditions for comparison. A scanning electron microscope (SEM), an optical microscope (OM) and X-ray diffraction (XRD) were utilized to characterize the feedstock powder and coatings. Weibull plots were used to analyze the performance of the nanostructured coatings. The lower 300 A operating current resulted in a higher portion of nanostructure retention at the expense of coating quality. An approximate 10% increase in porosity and a noticeable decrease in grain size (∼104 nm) were obtained by spraying non-heat treated agglomerates with a 500 A current. The thermal conductivity (400-600 °C) was evaluated using the one-dimensional, steady state Fourier's law of heat conduction. Next, lower thermal conductivity (∼1.3 W m-1 K-1 at 600 °C) was identified in coatings engineered at 500 A from agglomerated powder with no heat treatment.

  3. Effects of texture on salt precipitation dynamics and deposition patterns in drying porous media

    Science.gov (United States)

    Norouzi Rad, Mansoureh; Shokri, Nima

    2015-04-01

    Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, CO2 sequestration and water quality. Also excess of salt accumulation in soil may result in soil salinization which is a global problem adversely affecting vegetation, plant growth and crop production. Thus it is important to understand the parameters affecting salt transport and precipitation in porous media. We applied X-ray micro-tomography to investigate the dynamics of salt precipitation during evaporation from porous media as influenced by the particle and pore sizes. The packed beds were saturated with NaCl solution of 3 Molal and the time-lapse X-ray imaging was continued for one day. The results show that the presence of preferential evaporation sites (associated with fine pores) on the surface of the sand columns influences significantly the patterns and dynamics of NaCl precipitation (Norouzi Rad et al., 2013; Norouzi Rad and Shokri, 2014). They confirm the formation of an increasingly thick and discrete salt crust with increasing grain size in the sand column due to the presence of fewer fine pores (preferential precipitation sites) at the surface compared to the sand packs with finer grains. Fewer fine pores on the surface also results in shorter stage-1 precipitation for the columns with larger grain sizes. A simple model for the evolution of salt crust thickness based on this principle shows a good agreement with our experiments. Our results provide new insights regarding the physics of salt precipitation and its complex dynamics in porous media during evaporation. References Norouzi Rad, M., Shokri, N., Sahimi, M. (2013), Pore-Scale Dynamics of Salt Precipitation in Drying Porous Media, Phys. Rev. E, 88, 032404. Norouzi Rad, M., Shokri, N. (2014), Effects of grain angularity on NaCl precipitation in porous media during evaporation, Water Resour. Res

  4. Boring of full scale deposition holes using a novel dry blind boring method

    Energy Technology Data Exchange (ETDEWEB)

    Autio, J.; Kirkkomaeki, T. [Saanio and Riekkola Oy, Helsinki (Finland)

    1996-10-01

    Three holes the size of deposition holes (depth 7.5 m and diameter 1.5 m) were bored in the Research Tunnel at Olkiluoto, Finland. A novel full-face boring technique was used based on rotary crushing of rock and removal of crushed rock by vacuum flushing through the drill string. The purpose of the work was to demonstrate the feasibility of the technique. During the boring test procedures were carried out in order to determine the effect of changes in operating parameters on the performance of the boring machine and the quality of the hole. The boring method was found to be technically feasible and efficient. Evaluation of the quality of the hole included studies of the geometry of the hole, measurements of the surface roughness using a laser profilometer and study of excavation disturbances in the zone adjacent to the surface of the holes using two novel methods, He-gas diffusion and the {sup 14}C-polymethylmethacrylate methods. 43 refs.

  5. Mechanistic study of aerosol dry deposition on vegetated canopies; Etude mecaniste du depot sec d'aerosols sur les couverts vegetaux

    Energy Technology Data Exchange (ETDEWEB)

    Petroff, A

    2005-04-15

    The dry deposition of aerosols onto vegetated canopies is modelled through a mechanistic approach. The interaction between aerosols and vegetation is first formulated by using a set of parameters, which are defined at the local scale of one surface. The overall deposition is then deduced at the canopy scale through an up-scaling procedure based on the statistic distribution parameters. This model takes into account the canopy structural and morphological properties, and the main characteristics of the turbulent flow. Deposition mechanisms considered are Brownian diffusion, interception, initial and turbulent impaction, initially with coniferous branches and then with entire canopies of different roughness, such as grass, crop field and forest. (author)

  6. Seasonal and diurnal variations of Hg° over New England

    Directory of Open Access Journals (Sweden)

    J. D. Hegarty

    2007-11-01

    Full Text Available Factors influencing diurnal to interannual variability in Hg° over New England were investigated using multi-year measurements conducted by the AIRMAP program at the Thompson Farm (TF coastal site, an inland elevated site at Pac Monadnock (PM, and one summer of measurements on Appledore Island (AI in the Gulf of Maine. Mixing ratios of Hg° at TF showed distinct seasonality with maxima in March and minima in October. In comparison, Hg° at AI tracked the trend at TF but with higher minima, while at PM the diurnal and annual cycles were dampened. In winter, Hg° was correlated most strongly with CO and NOy, indicative of anthropogenic emissions as their primary source. Our analysis indicates that Hg° had a regional background level of ~160 fmol/mol, a summertime dry deposition velocity of ~0.20 cm s−1, and a ~16 day lifetime in the coastal boundary layer. The influence of oceanic emissions on ambient Hg° levels was identified using the Hg°-CHBr3 correlation at both TF and AI. Moreover, the lower Hg° levels and steeper decreasing warm season trend at TF (0.5–0.6 fmol/mol d−1 compared to PM (0.2–0.3 fmol/mol d−1 likely reflected the impact of marine halogen chemistry. Large interannual variability in warm season Hg° levels in 2004 versus 2005/2006 may be due to the role of precipitation patterns in influencing surface evasion of Hg°. In contrast, changes in wintertime maximum levels of Hg° were small compared to drastic reductions in CO, CO2, NOy, and SO2 from 2004/2005 to 2006/2007. These trends could be explained by a homogeneous surface distribution of Hg° over the North American continent in winter and/or rapid removal of mercury released from anthropogenic sources. We caution that during warmer winters, the Hg°-CO slope possibly reflects the ratio of Hg° loss relative to changes in CO more than their emission ratio.

  7. Seasonal and diurnal variations of Hg° over New England

    Directory of Open Access Journals (Sweden)

    J. D. Hegarty

    2008-03-01

    Full Text Available Factors influencing diurnal to interannual variability in Hg° over New England were investigated using multi-year measurements conducted by AIRMAP at the Thompson Farm (TF coastal site, an inland elevated site at Pac Monadnock (PM, and two month measurements on Appledore Island (AI in the Gulf of Maine. Mixing ratios of Hg° at TF showed distinct seasonality with maxima in March and minima in October. Hg° at AI tracked the trend at TF but with higher minima, while at PM the diurnal and annual cycles were dampened. In winter, Hg° was correlated most strongly with CO and NOy, indicative of anthropogenic emissions as their primary source. Our analysis indicates that Hg° had a regional background level of ~160 fmol/mol in winter, a dry deposition velocity of ~0.20 cm s−1 with a ~16 day lifetime in the coastal boundary layer in summer. The influence of oceanic emissions on ambient Hg° levels was identified using the Hg°-CHBr3 correlation at both TF and AI. Moreover, the lower Hg° levels and steeper decreasing warm season trend at TF (0.5–0.6 fmol/mol d−1 compared to PM (0.2–0.3 fmol/mol d−1 likely reflected the impact of marine halogen chemistry. Large interannual variability in warm season Hg° levels in 2004 versus 2005/2006 may be due to the role of precipitation patterns in influencing surface evasion of Hg°. In contrast, changes in wintertime maximum levels of Hg° were small compared to drastic reductions in CO, CO2, NOy, and SO2 from 2004/2005 to 2006/2007. These trends could be explained by a homogeneous distribution of Hg° over North American in winter due to its long lifetime and/or rapid removal of reactive mercury from anthropogenic sources. We caution that during warmer winters, the Hg°-CO slope possibly reflects Hg° loss relative to changes in CO more than their emission ratio.

  8. A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow

    Directory of Open Access Journals (Sweden)

    A. C. Hansen

    2015-09-01

    Full Text Available The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the effective thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for effective thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

  9. Simulating Dry Deposition Fluxes of PM10 and Particulate Inorganic Nitrogen over the Eastern China Seas During a Severe Asian Dust Event Using WRF-Chem Model

    Institute of Scientific and Technical Information of China (English)

    YAN Han; GAO Huiwang; YAO Xiaohong; WANG Zifa

    2012-01-01

    A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March,2002.The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom.The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system.The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event,respectively.However,the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea.Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March.The dust plume arrived in the Yellow Sea on 20 March,decreasing the particulate inorganic nitrogen in mass concentration accordingly.The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival,respectively.In contrast,when the dust plume crossed over the Yangtze Delta area,it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea,where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival.

  10. Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources

    Science.gov (United States)

    Domagalski, Joseph L.; Majewski, Michael S.; Alpers, Charles N.; Eckley, Chris S.; Eagles-Smith, Collin A.; Schenk, Liam N.; Wherry, Susan

    2016-01-01

    Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio > 1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (< 0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (< 0.1), whereas urbanized areas had higher ratios (0.34–1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg.

  11. Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources.

    Science.gov (United States)

    Domagalski, Joseph; Majewski, Michael S; Alpers, Charles N; Eckley, Chris S; Eagles-Smith, Collin A; Schenk, Liam; Wherry, Susan

    2016-10-15

    Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio>1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (<0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (<0.1), whereas urbanized areas had higher ratios (0.34-1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg.

  12. Long-term Hg pollution induced Hg tolerance in the terrestrial isopod Porcellio scaber (Isopoda, Crustacea).

    Science.gov (United States)

    Lapanje, A; Drobne, D; Nolde, N; Valant, J; Muscet, B; Leser, V; Rupnik, M

    2008-06-01

    The aim of our work was to assess the pollution-induced community tolerance (PICT) of isopod gut microbiota and pollution-induced isopod population tolerance (PIPT). Animals collected from a chronically Hg polluted and an unpolluted location were exposed for 14 days to 10microg Hg/g dry food under laboratory conditions. The lysosomal membrane stability, hepatopancreas epithelium thickness, feeding activity and animal bacterial gut microbiota composition were determined. The results confirm the hypothesis that the response to short-term Hg exposure differs for animals from the Hg polluted and the unpolluted field locations. The animals and their gut microbiota from the Hg polluted location were less affected by Hg in a short-term feeding experiment than those from the unpolluted environment. We discuss the pollution-induced population tolerance of isopods and their gut microbiota as a measure of effects of long-term environmental pollution. The ecological consequences of such phenomena are also discussed.

  13. Mechanisms and rates of atmospheric deposition of selected trace elements and sulfate to a deciduous forest watershed. [Roles of dry and wet deposition concentrations measured in Walker Branch Watershed

    Energy Technology Data Exchange (ETDEWEB)

    Lindberg, S.E.; Harriss, R.C.; Turner, R.R.; Shriner, D.S.; Huff, D.D.

    1979-06-01

    The critical links between anthropogenic emissions to the atmosphere and their effects on ecosystems are the mechanisms and rates of atmospheric deposition. The atmospheric input of several trace elements and sulfate to a deciduous forest canopy is quantified and the major mechanisms of deposition are determined. The study area was Walker Branch Watershed (WBW) in eastern Tennessee. The presence of a significant quantity of fly ash and dispersed soil particles on upward-facing leaf and flat surfaces suggested sedimentation to be a major mechanism of dry deposition to upper canopy elements. The agreement for deposition rates measured to inert, flat surfaces and to leaves was good for Cd, SO/sub 4//sup =/, Zn, and Mn but poor for Pb. The precipitation concentrations of H/sup +/, Pb, Mn, and SO/sub 4//sup =/ reached maximum values during the summer months. About 90% of the wet deposition of Pb and SO/sub 4//sup =/ was attributed to scavenging by in-cloud processes while for Cd and Mn, removal by in-cloud scavenging accounted for 60 to 70% of the deposition. The interception of incoming rain by the forest canopy resulted in a net increase in the concentrations of Cd, Mn, Pb, Zn, and SO/sub 4//sup =/ but a net decrease in the concentration of H/sup +/. The source of these elements in the forest canopy was primarily dry deposited aerosols for Pb, primarily internal plant leaching for Mn, Cd, and Zn, and an approximately equal combination of the two for SO/sub 4//sup =/. Significant fractions of the total annual elemental flux to the forest floor in a representative chestnut oak stand were attributable to external sources for Pb (99%), Zn (44%), Cd (42%), SO/sub 4//sup =/ (39%), and Mn (14%), the remainder being related to internal element cycling mechanisms. On an annual scale the dry deposition process constituted a significant fraction of the total atmospheric input. (ERB)

  14. Biotoxicity of Mars soils: 1. Dry deposition of analog soils on microbial colonies and survival under Martian conditions

    Science.gov (United States)

    Schuerger, Andrew C.; Golden, D. C.; Ming, Doug W.

    2012-11-01

    Six Mars analog soils were created to simulate a range of potentially biotoxic geochemistries relevant to the survival of terrestrial microorganisms on Mars, and included basalt-only (non-toxic control), salt, acidic, alkaline, aeolian, and perchlorate rich geochemistries. Experiments were designed to simulate the dry-deposition of Mars soils onto spacecraft surfaces during an active descent landing scenario with propellant engines. Six eubacteria were initially tested for tolerance to desiccation, and the spore-former Bacillus subtilis HA101 and non-spore former Enterococcus faecalis ATCC 29212 were identified to be strongly resistant (HA101) and moderately resistant (29212) to desiccation at 24 °C. Furthermore, tests with B. subtilis and E. faecalis demonstrated that at least 1 mm of Mars analog soil was required to fully attenuate the biocidal effects of a simulated Mars-normal equatorial UV flux. Biotoxicity experiments were conducted under simulated Martian conditions of 6.9 mbar, -10 °C, CO2-enriched anoxic atmosphere, and a simulated equatorial solar spectrum (200-1100 nm) with an optical depth of 0.1. For B. subtilis, the six analog soils were found, in general, to be of low biotoxicity with only the high salt and acidic soils exhibiting the capacity to inactivate a moderate number of spores (<1 log reductions) exposed 7 days to the soils under simulated Martian conditions. In contrast, the overall response of E. faecalis to the analog soils was more dramatic with between two and three orders of magnitude reductions in viable cells for most soils, and between six and seven orders of magnitude reductions observed for the high-salt soil. Results suggest that Mars soils are likely not to be overtly biotoxic to terrestrial microorganisms, and suggest that the soil geochemistries on Mars will not preclude the habitability of the Martian surface.

  15. Dry deposition and canopy uptake in Mediterranean holm-oak forests estimated with a canopy budget model: A focus on N estimations

    Science.gov (United States)

    Aguillaume, L.; Izquieta-Rojano, S.; García-Gómez, H.; Elustondo, D.; Santamaría, J. M.; Alonso, R.; Avila, A.

    2017-03-01

    Bulk/wet and throughfall fluxes of major compounds were measured from June 2011 to June 2013 at four Mediterranean holm-oak (Quercus ilex) forests in the Iberian Peninsula. Regression analysis between net throughfall fluxes and precipitation indicated that the best defined canopy process was leaching for K+ and uptake for NH4+ at all sites. A more variable response between sites was found for Na+, Ca2+, SO42- and Cl-, which suggests that the interplay of dry deposition, leaching and uptake at the canopy was different depending on site climate and air quality characteristics. A canopy budget model (CBM) was used to try to discriminate between the canopy processes and enable to estimate dry deposition and uptake fluxes at three of the sites that complied with the model specifications. To derive N uptake, an efficiency factor of NH4+vs. NO3- uptake (xNH4) corresponding to moles of NH4+ taken up for each NO3- mol, has to be determined. Up to now, a value of 6 has been proposed for temperate forests, but we lack information for Mediterranean forests. Experimental determination of N absorption on Quercus ilex seedlings in Spain suggests efficiency factors from 1 to 6. Based on these values, a sensitivity analysis for xNH4 was performed and the NH4sbnd N and NO3sbnd N modeled dry deposition was compared with dry deposition estimated with independent methods (inferential modeling and washing of branches). At two sites in NE Spain under a milder Mediterranean climate, the best match was obtained for xNH4 = 6, corroborating results from European temperate forests. Based on this value, total DIN deposition was 12-13 kg N ha-1 y-1 at these sites. However, for a site in central Spain under drier conditions, variation of the NH4+ efficiency factor had little effect on DD estimates (which ranged from 2 to 2.6 kg N ha-1 y-1 with varying xNH4); when added to wet deposition, this produced a total N deposition in the range 2.6-3.4 kg N ha-1 y-1. Dry deposition was the predominant

  16. Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

    OpenAIRE

    John Meynard M. Tengco; Bahareh Alsadat Tavakoli Mehrabadi; Yunya Zhang; Akkarat Wongkaew; John R. Regalbuto; Weidner, John W.; John R. Monnier

    2016-01-01

    Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED) of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) characterization of the base catalyst showed highly dispersed particles. A basic E...

  17. Dry deposition of gaseous elemental mercury to plants and soils using mercury stable isotopes in a controlled environment

    Science.gov (United States)

    Rutter, Andrew P.; Schauer, James J.; Shafer, Martin M.; Creswell, Joel E.; Olson, Michael R.; Robinson, Michael; Collins, Ryan M.; Parman, Andrew M.; Katzman, Tanya L.; Mallek, Justin L.

    2011-02-01

    Uptake of gaseous elemental mercury (Hg 0(g)) by three plant species and two soil types was measured using mercury vapor enriched in the 198 isotope ( 198Hg 0(g)). The plant species and soil types were: White Ash ( Fraxinus Americana; WA); White Spruce ( Picea Glauca; WS); Kentucky Bluegrass ( Poa Partensis; KYBG); Plano Silt Loam (4% organic matter; PSL); and Plainfield Sand/Sparta Loamy Sand (1.25-1.5% organic matter: PS). The plants and soils were exposed to isotopically enriched Hg 0(g) in a 19 m 3 controlled environment room for 7 days under optimal plant growth conditions (20 °C, 140 Wm -2 between 300 nm and 700 nm; 70% RH) and atmospherically relevant Hg 0(g) concentrations. Mercury was recovered from the samples using acidic digestions and surface leaches, and then analyzed for enrichments in 198Hg by ICPMS. The method was sensitivity enough that statistically significant enrichments in 198Hg were measured in the plant foliage at the end of Day 1. Whole leaf digestions and surface-selective leaches revealed that accumulative uptake was predominantly to the interior of the leaf under the conditions studied. Uptake fluxes for WA increased between the first and third days and remained constant thereafter (WA; Day 1 = 7 ± 2 × 10 -5 ng m -2 s -1; Days 3-7 = 1.3 ± 0.1 × 10 -4 ng m -2 s -1; where m 2 refers to one sided leaf area). KYBG demonstrated similar behavior although no Day 3 measurement was available (Day 1 = 7.5 ± 0.5 × 10 -5 ng m -2 s -1; Day 7 = 1.2 ± 0.1 × 10 -4 ng m -2 s -1). Fluxes to White Spruce were lower, with little difference between Days 1 and 3 followed by a decrease at Day 7 (WS; Days 1-3 = 5 ± 2 × 10 -5 ng m -2 s -1; Day 7 = 2.4 ± 0.2 × 10 -5 ng m -2 s -1). Uptake of Hg to soils was below the method detection limit for those media (PSL = 3 × 10 -2 ng m -2 s -1; PS = 3 × 10 -3 ng m -2 s -1) over the 7 day study period. Foliar resistances calculated for each species compared well to previous studies.

  18. Parallel measurements of organic and elemental carbon dry (PM1, PM2.5) and wet (rain, snow, mixed) deposition into the Baltic Sea.

    Science.gov (United States)

    Witkowska, Agnieszka; Lewandowska, Anita; Falkowska, Lucyna M

    2016-03-15

    Parallel studies on organic and elemental carbon in PM1 and PM2.5 aerosols and in wet deposition in various forms of its occurrence were conducted in the urbanised coastal zone of the Baltic Sea. The carbon load introduced into the sea water was mainly affected by the form of precipitation. Dry deposition load of carbon was on average a few orders of magnitude smaller than wet deposition. The suspended organic carbon was more effectively removed from the air with rain than snow, while an inverse relationship was found for elemental carbon. However the highest flux of water insoluble organic carbon was recorded in precipitation of a mixed nature. The atmospheric cleaning of highly dissolved organic carbon was observed to be the most effective on the first day of precipitation, while the hydrophobic elemental carbon was removed more efficiently when the precipitation lasted longer than a day.

  19. Chemical thermodynamics of Hg1201 and Hg1223 phases

    Science.gov (United States)

    Tsuchiya, Tetsuo; Fueki, Kazuo; Koyama, Tadashi

    1998-03-01

    The decomposition equilibrium of Hg1201 and Hg1223 was studied using a thermomicrobalance. A thermodynamic diagram representing the stability domains of Hg1201 and Hg1223 was constructed. Using the diagram, it was shown that Hg1201 is metastable at 800°C and that Hg1223 is stable at 660°C due to the formation of an atmosphere of mercury vapor and oxygen formed by the decomposition of excess HgO. Chemical analysis revealed that the valence of Hg is +2 regardless of the oxygen content. The dependence of Tc on the oxygen content was also studied.

  20. Microbial ecology of á-Proteobacteria ammonia-oxidizers along a concentration gradient of dry atmospheric nitrogen deposition in the San Bernadino Mountain Range.

    Science.gov (United States)

    Jordan, F. L.; Fenn, M. E.; Stein, L. Y.

    2002-12-01

    The fate of atmospherically-deposited nitrogen from industrial pollution is of major concern in the montane ecosystems bordering the South Coast California Air Basin. Nitrogen deposition rates in the more exposed regions of the San Bernardino Mountains (SBM) are among the highest in North America often exceeding 40 kg ha-1 year-1 in throughfall deposition of nitrate and ammonium (Fenn and Poth, 1999). Forest ecosystems with elevated N deposition generally exhibit elevated accumulation of soil nitrate, leaching and runoff, elevated emissions of nitrogenous gases, increased nitrification, and decreased litter decomposition rates. The role of nitrifying microbial populations, especially those taxonomically associated with the beta-Proteobacteria ammonia-oxidizers (AOB), will provide insight into nitrogen-cycling in these extremely N-saturated environments. Using 16S ribosomal DNA-based molecular techniques (16S rDNA clone library construction and Restriction Fragment Length Polymorphism), we are comparing AOB community diversity at 3 different locations along a natural atmospheric N-deposition concentration gradient in the SBM: from high at Camp Paviaka (CP), medium at Strawberry Peak (SP) to low at Dogwood (DW). As observed for wet N-deposition systems on the east coast, we hypothesized a negative correlation between AOB community diversity, abundance and function with nitrogen loading in the dry N deposition system of SBM. Nitrification potentials determined for the 3 sites along the N-deposition gradient were in the order of CP less than SP less than DW. Preliminary results indicate no correlation between diversity of AOB and increased nitrogen loading. Shannon-Weiner diversity indices calculated for ammonia-oxidizer RFLP group units were 2.22, 2.66 and 1.80 for CP, SP and DW, respectively.

  1. Climate-driven exceedance of total (wet + dry) nitrogen (N) + sulfur (S) deposition to forest soil over the conterminous U.S

    Science.gov (United States)

    Sun, Jian; Fu, Joshua S.; Lynch, Jason A.; Huang, Kan; Gao, Yang

    2017-06-01

    Nitrogen (N) and sulfur (S) depositions are much mitigated over the conterminous U.S. (CONUS) but deposition exceedance still exists on forest soil. In addition, the empirical approach is usually used but only provides a spatially constant critical load (CL). Therefore, the CL derived from steady-state mass balance equation is used to study the CL exceedance on forest soil over the CONUS. The multimodel mean (MMM) of global climate-chemistry models in 2000s indicates that total (wet + dry) N deposition alone over 10.32% of forest soil exceeds the CL, but a higher percent (30.16%) is observed by the N + S deposition, which highlights the necessity of considering S deposition. In 2050s, less CL-exceeded forest soil is projected and the exceedance amount is lower as well, mainly attributed to the strong reduction of projected NOX and SO2 emissions. By first projecting the future CL due to the climate change, the CL exceedance could further decrease as the air temperature is projected to increase rapidly and lead to higher CL in the future. The CL exceedance by N deposition alone is likely to be dominated by NOy in 2000s but NHX in 2050s because of the enhanced NH3 emission. Moreover, both in 2000s and 2050s, using the CL generated by different aggregation methods can cause up to 33 times difference between the corresponding CL exceedance. This suggests that several regions are under the marginal threat of either N or N + S deposition and different CL can influence the results significantly.

  2. Assessment of mobility and bio-availability of heavy metals in dry depositions of Asian dust and implications for environmental risk.

    Science.gov (United States)

    Lee, Pyeong-Koo; Choi, Byoung-Young; Kang, Min-Ju

    2015-01-01

    We assess the potential mobility and bio-availability of selected metals (As, Cd, Co, Cr, Cu, Ni, Mo, Pb, S, Zn, and Zr) in the dry depositions of Asian and non-Asian dust from the city of Daejeon, Korea. For this study, we applied Pb isotopes, total extraction and chemical sequential extraction methods to the dry depositions. In addition, microscopic analysis was performed using X-ray diffraction (XRD) and focused ion beam (FIB)-scanning electron microscopy (SEM-EDS). FIB-SEM cross-section observations and Pb isotope data showed a black carbon is an important carrier of associated heavy metals originating from China. A five-step sequential extraction performed on the dry depositions showed that S and Cd are the most abundant elements in the water-soluble and cation-exchangeable fraction. In addition, Zn and Pb appeared predominantly in the carbonate and reducible fractions. On the other hand, Cu, Mo and, to a lesser degree, As were significantly associated with the organic fraction, while Co, Ni, Cr and Zr were bound to the residual fraction. These results showed that S, Cd, Zn and Pb, which were highly concentrated in potentially mobile fractions, have potential environmental risk because potential changes in redox state and pH may remobilize these metals. In addition, the estimated remobilization concentrations of these metals were significant. Thus, this study shows that frequent and careful monitoring of S, Cd, Z, Pb and, to a lesser degree, Cu, Mo and As is very important for assessing environmental risk in Korea. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Monitoring ambient air pollutants and apply Woods' model in the prediction seasonal dry deposition at Chang-Hua (urban) and Kao-Mei (wetland) county, Taiwan.

    Science.gov (United States)

    Fang, Guor-Cheng; Chang, Chia-Ying

    2014-09-01

    The main purpose for this study was to monitor ambient air particles and metallic elements (Mn, Fe, Zn, Cr, Cu and Pb) in total suspended particulate (TSP) concentration and dry deposition. In addition, the calculated/measured dry deposition flux ratios of ambient air particles and metallic elements (Mn, Fe, Zn, Cr, Cu and Pb) were evaluated using Woods' model at urban and wetland areas for the 2009-2010 period. The results indicated that the mean highest concentrations of metallic elements Mn, Fe, Zn, Cr, Cu and Pb in TSP were found in Chang-Hua (urban) sampling site. And as for the two characteristic sampling sites, the Woods' model exhibits better dry deposition of particulates of 18 µm particle size than the rest of the other particle sizes at any sampling site in this study. The average calculated/measured flux ratios for two seasons (summer and fall) by using Woods model at 2.5, 10 and 18 µm particles sizes were also studied. The results indicated that the average calculated/measured flux ratios orders for two seasons of various particles sizes were all displayed as Fe > Mn > Zn > Cu > Cr > Pb > particle. And these calculated/measured flux ratios orders were Fe > Mn > Cu > Zn > Cr > Pb > particle and were Fe > Mn > Zn > Cu > Cr > particle > Pb, during spring and winter seasons, respectively. Finally, in the spring and summer seasons of Gao-Mei (wetland) sampling site, the average calculated/measured flux ratios using Woods' model was found to be 2.5, 10 and 18 µm, showing the order of the calculated/measured flux ratios to be Fe > Cu > Zn > Mn > Cr > Pb > particle. And the calculated/measured flux ratio orders were Fe > Zn > Mn > Cu > Cr > particle > Pb and were Fe > Cu > Zn > Mn > Cr > particle > Pb for fall and winter season, respectively.

  4. Influence of atmospheric dry deposition of inorganic nutrients on phytoplankton biomass in the coastal Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Yadav, K.; Sarma, V.V.S.S.; Rao, D.B.; DileepKumar, M.

    suggests that atmospheric deposition of nutrients enhances phytoplankton biomass in waters along the central east coast of India during the winter monsoon period, in particular, supporting the hypothesis stated above...

  5. Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

    Directory of Open Access Journals (Sweden)

    John Meynard M. Tengco

    2016-06-01

    Full Text Available Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD and scanning transmission electron microscopy (STEM characterization of the base catalyst showed highly dispersed particles. A basic ED bath containing PtCl62− as the Pt precursor, dimethylamine borane as reducing agent, and ethylenediamine as stabilizing agent successfully targeted deposition of Pt on Co particles. Simultaneous action of galvanic displacement and ED resulted in Pt-Co alloy formation observed in XRD and energy dispersive X-ray spectroscopy (XEDS mapping. In addition, fast deposition kinetics resulted in hollow shell Pt-Co alloy particles while particles with Pt-rich shell and Co-rich cores formed with controlled Pt deposition. Electrochemical evaluation of the Pt-Co/C catalysts showed lower active surface but much higher mass and surface activities for oxygen reduction reaction compared to a commercial Pt/C fuel cell catalyst.

  6. Determination of MeHg sources to fish in the St. Louis River, MN, USA, using Hg stable isotopes

    Science.gov (United States)

    Mercury contamination in the Great Lakes region has become a prevalent concern due to elevated methylmercury (MeHg) levels in fish. While atmospheric deposition of Hg is ubiquitous, releases from legacy point-sources give rise to numerous Areas of Concern (AOCs) across the Great ...

  7. Atmospheric particle dry deposition of major ions to the South Atlantic coastal area observed at Baía de Todos os Santos, Brazil

    Directory of Open Access Journals (Sweden)

    STELYUS L. MKOMA

    2014-03-01

    Full Text Available The coastal atmosphere adjacent to large urban areas can be strongly affected by the emission of air pollutants, among them, major ions species. In this study, the chemical composition and sources of carboxylates and other water-soluble ions in fine and coarse aerosols as well as estimates of particle dry deposition fluxes were studied at a tropical coastal site affected by an urban environment. The mean concentrations of the total carboxylates were 78 ng m–3 in fine fraction and 81 ng m–3 in coarse fraction of particulate matter (PM. The corresponding values for the total inorganic ions were 2143 ng m–3 and 4880 ng m–3 respectively. Main sources for fine particles were: (i photochemical formation of carboxylic acids in vapor phase and a posterior gas-to-particle conversion onto sea salt particles; (ii emissions from anthropic sources with long range transportation processes; and (iii the interchanging of volatile species among atmospheric phases. In turn, for coarse particles, the predominant sources were: (i gas-phase species and ab/adsorbed onto pre-existing particles afterwards; (ii primary emission of coarse particles from anthropogenic sources; and (iii sea salt spray and/or soil resuspension. Finally, particle dry deposition was a very important mechanism representing air-to-sea fluxes of major species.

  8. Quantifying the dry deposition of reactive nitrogen and sulfur containing species in remote areas using a surrogate surface analysis approach

    Science.gov (United States)

    Raymond, Heather A.; Yi, Seung-Muk; Moumen, Nadjoua; Han, YoungJi; Holsen, Thomas M.

    In this study, the fluxes of gaseous (HNO 3 and SO 2) and particulate (NO 3- and SO 42-) species were measured using two recently developed surrogate surfaces, the water surface sampler (WSS) and the knife-edge surrogate surface (KSS). Sampling was conducted in Potsdam, NY, Solomons, MD, and at a farm in upstate NY intermittently between March 2000 and August 2001. The KSS contained both Nylasorb filters and greased Mylar disks. No statistical difference was found between measured total nitrate and sulfate deposition in side-by-side experiments with two WSSs. Average total nitrate fluxes measured with the WSS and Nylasorb filter on the KSS in Potsdam, Solomons, and at the farm were 3.6, 6.2, 2.9 mg m -2 day -1 and 2.5, 6.7, 2.3 mg m -2 day -1, respectively. Solomons had the highest total nitrate flux probably due to its proximity to large urban industrialized areas including Washington, DC, and Baltimore, MD. Average gaseous HNO 3 fluxes measured with the WSS and Nylasorb filter on the KSS in Potsdam, Solomons, and at the farm (calculated by subtracting the fraction of particles deposited to the Mylar disk from the total deposition to the WSS and Nylasorb filter) were 2.4, 4.9, 1.9 mg m -2 day -1 and 1.3, 5.6, 1.3 mg m -2 day -1, respectively. In Potsdam, total nitrate deposition to the WSS was greater than to the Nylasorb filter whereas in Solomons the opposite was true. This increased flux at Solomons may be because nitrate salts were formed on the surface of the Nylasorb filter by reaction of HNO 3 with previously deposited sea salt aerosols. Average p-NO 3- fluxes to the greased Mylar for the three sampling sites were 1.3, 1.3, and 1.0 mg m -2 day -1. The measured SO 2 deposition velocity to the WSS in Potsdam and Solomons was 2.1 and 1.5 cm s -1, respectively, and agreed well with other studies. The deposition velocity for HNO 3 to the WSS measured in Potsdam (8.1 cm s -1) was greater than to the Nylasorb filter (4.6 cm s -1) whereas in Solomons the opposite

  9. High N, dry: Experimental nitrogen deposition exacerbates native shrub loss and nonnative plant invasion during extreme drought.

    Science.gov (United States)

    Valliere, Justin M; Irvine, Irina C; Santiago, Louis; Allen, Edith B

    2017-03-20

    Hotter, longer, and more frequent global change-type drought events may profoundly impact terrestrial ecosystems by triggering widespread vegetation mortality. However, severe drought is only one component of global change, and ecological effects of drought may be compounded by other drivers, such as anthropogenic nitrogen (N) deposition and nonnative plant invasion. Elevated N deposition, for example, may reduce drought tolerance through increased plant productivity, thereby contributing to drought-induced mortality. High N availability also often favors invasive, nonnative plant species, and the loss of woody vegetation due to drought may create a window of opportunity for these invaders. We investigated the effects of multiple levels of simulated N deposition on a Mediterranean-type shrubland plant community in southern California from 2011 to 2016, a period coinciding with an extreme, multi-year drought in the region. We hypothesized that N addition would increase native shrub productivity, but that this would increase susceptibility to drought and result in increased shrub loss over time. We also predicted that N addition would favor nonnatives, especially annual grasses, leading to higher biomass and cover of these species. Consistent with these hypotheses, we found that high N availability increased native shrub canopy loss and mortality, likely due to the higher productivity and leaf area and reduced water-use efficiency we observed in shrubs subject to N addition. As native shrub cover declined, we also observed a concomitant increase in cover and biomass of nonnative annuals, particularly under high levels of experimental N deposition. Together, these results suggest that the impacts of extended drought on shrubland ecosystems may be more severe under elevated N deposition, potentially contributing to the widespread loss of native woody species and vegetation type-conversion. This article is protected by copyright. All rights reserved.

  10. Geochemical investigation of dry- and wet-deposited dust during the same dust-storm event in Harbin, China: Constraint on provenance and implications for formation of aeolian loess

    Science.gov (United States)

    Xie, Yuanyun; Chi, Yunping

    2016-04-01

    A strong dust-storm event occurred in Harbin, China on May 11, 2011. The dry- and wet-deposited dust depositions in this dust-storm event, together with the surface sediments from the potential sources, were collected to study grain size distributions, carbonate content and carbon isotopic composition of carbonate, major element, trace element and rare earth elements (REE), and Sr-Nd isotopic compositions. The results indicate as follows. The dry-deposited dusts are characterized by bimodal grain-size distributions with a fine mode at 3.6 μm and a coarse mode at 28 μm whereas the wet-deposited dusts are indicative of unimodal grain-size modes with a fine mode at 6 μm. The dust-storm depositions are influenced to a certain extent by sedimentary sorting and are of a derivation from the recycled sediments. Based on identifying the immobility of element pairs before constraining sources of dust-storm deposits using geochemical elements, in conjunction with REE and especially Sr-Nd isotopic compositions, the primary and strengthening sources for the dust-storm event were detected, respectively. The Hunsandake Sandy Land as the primary source and the Horqin Sandy Land as the strengthening source were together responsible for the derivation of dust depositions during dust-storm event. The Hunsandake Sandy Land, however, contributes less dust to the dust-storm event in Harbin compared to the Horqin Sandy Land, and the Hulun Buir Sandy Land is undoubtedly excluded from being one of the sources for dust-storm depositions in Harbin. There are not notable differences in geochemical (especially Sr-Nd isotopic) compositions between dry- and wet-deposited dusts, indicating that the wet-deposited dust is of identical derivation to the dry-deposited dust. Based on our observations, it is of interest to suggest that fine and coarse particles in the CLP (Chinese Loess Plateau) loess possibly have the same sources.

  11. Atmospheric dry deposition of inorganic and organic nitrogen to the Bay of Bengal: Impact of continental outflow

    Digital Repository Service at National Institute of Oceanography (India)

    Srinivas, B.; Sarin, M.M.; Sarma, V.V.S.S.

    of nitrate in coarse continental aerosols. . Atmospheric Environment,, 18: 977-981. Zhang, Q. and Anastasio, C., 2003a. Conversion of Fogwater and Aerosol Organic Nitrogen to Ammonium, Nitrate, and NOx during Exposure to Simulated Sunlight and Ozone.... Chem., vol.127; 2011; 170–179 Atmospheric Deposition of Inorganic and Organic Nitrogen to the Bay of Bengal: Impact of Continental Outflow Bikkina Srinivas 1 , * M. M. Sarin 1 and V.V.S.S. Sarma 2 1 Physical Research Laboratory, Ahmedabad – 380...

  12. Long-term Hg pollution induced Hg tolerance in the terrestrial isopod Porcellio scaber (Isopoda, Crustacea)

    Energy Technology Data Exchange (ETDEWEB)

    Lapanje, A. [University of Ljubljana, Biotechnical Faculty, Department of Biology, Vecna pot 111, 1000 Ljubljana (Slovenia); Institute of Physical Biology, Veliko Mlacevo 59, 1290 Grosuplje (Slovenia)], E-mail: ales.lapanje@bf.uni-lj.si; Drobne, D. [University of Ljubljana, Biotechnical Faculty, Department of Biology, Vecna pot 111, 1000 Ljubljana (Slovenia); Nolde, N. [Institute Jozef Stefan, Department of Environmental Sciences, Jamova 39, 1000 Ljubljana (Slovenia); Valant, J. [University of Ljubljana, Biotechnical Faculty, Department of Biology, Vecna pot 111, 1000 Ljubljana (Slovenia); Muscet, B. [Institute of Physical Biology, Veliko Mlacevo 59, 1290 Grosuplje (Slovenia); Leser, V. [University of Ljubljana, Biotechnical Faculty, Department of Biology, Vecna pot 111, 1000 Ljubljana (Slovenia); Rupnik, M. [Institute of Public Health, Prvomajska 1, 2000 Maribor (Slovenia); Faculty of Medicine, University of Maribor, Slomskov trg 15, 2000 Maribor (Slovenia)

    2008-06-15

    The aim of our work was to assess the pollution-induced community tolerance (PICT) of isopod gut microbiota and pollution-induced isopod population tolerance (PIPT). Animals collected from a chronically Hg polluted and an unpolluted location were exposed for 14 days to 10 {mu}g Hg/g dry food under laboratory conditions. The lysosomal membrane stability, hepatopancreas epithelium thickness, feeding activity and animal bacterial gut microbiota composition were determined. The results confirm the hypothesis that the response to short-term Hg exposure differs for animals from the Hg polluted and the unpolluted field locations. The animals and their gut microbiota from the Hg polluted location were less affected by Hg in a short-term feeding experiment than those from the unpolluted environment. We discuss the pollution-induced population tolerance of isopods and their gut microbiota as a measure of effects of long-term environmental pollution. The ecological consequences of such phenomena are also discussed. - Isopods (Porcellio scaber) as well as their bacterial gut community from a mercury-polluted site are mercury tolerant.

  13. Mass Independent Fractionation of Hg Isotopes Preserved in the Precambrian

    Science.gov (United States)

    Thibodeau, A. M.; Bergquist, B. A.; Kah, L. C.; Ono, S.; Ghosh, S.; Hazen, R. M.

    2013-12-01

    Mercury (Hg) is a photochemically active, redox-sensitive, chalcophilic metal with complex biogeochemistry that displays a wide range of mass-dependent (MDF) and mass-independent (MIF) stable isotopic fractionation. In the past decade, Hg isotopes have emerged as important tracers of both the sources and cycling of Hg in the modern environment. However, their utility as environmental proxies in ancient rocks remains largely unexplored. The potential of Hg isotopes to inform Precambrian environments derives from the observation that Hg isotopes with odd atomic mass numbers (199Hg and 201Hg) undergo large MIF by the magnetic isotope effect (MIE) and smaller MIF through the nuclear volume effect (NVE). Small MIF produced via NVE has been observed for numerous transformations and is characterized by MIF ratios (Δ199Hg/Δ201Hg) of about 1.6. Large Hg-MIF driven by MIE has been observed during photochemical transformations and is characterized by Δ199Hg/Δ201Hg ratios between 1 and 1.3. This MIF signal is sensitive to a range of environmental conditions, including the amount and type of solar radiation, the presence and type of complexing organic ligands, and the Hg/dissolved organic carbon (DOC) ratio. Thus, it is hoped that Hg-MIF signals may indirectly record changes in atmospheric composition or seawater chemistry if preserved in marine sedimentary records. Previous work has clearly demonstrated that Hg-MIF signals are preserved in Archean and Paleoproterozoic marine shales and massive sulfide deposits. Here, we present evidence that such signals are also preserved in marine shales of mid-Proterozoic age, including the ~1.3 Ga Sulky formation (Dismal Lakes Group, NW Arctic), the ~1.45 Ga Greyson Shale (Belt Basin, Montana), and the ~1.5 Ga Katalsy formation (Kypry Group, Eastern European Platform). We observe that the Greyson shale and shales within the Sulky formation yield negative Hg-MIF with Δ199Hg/Δ201Hg ratios close to 1 and that Kaltasy group sediments

  14. Estimation of air to grass -dry and wet deposition rates, velocities, and mass interception factors for iodine for a postulated accidental scenario

    Energy Technology Data Exchange (ETDEWEB)

    Karunakara, N.; Ujwal, P.; Yashodhara, I.; Sudeep Kumara, K. [University Science Instrumentation Centre, Mangalore University (India); Geetha, P.V. [Nuclear Power Corporation of India Limited (India); Dileep, B.N.; Joshi, P.J. [Environmental Survey Laboratory, Kaiga Generating Station (India); Ravi, P.M. [Health Physics Division, Bhabha Atomic Research Centre (India)

    2014-07-01

    Air to grass radionuclide transfer parameters such as dry and wet deposition rates, velocities, and mass interception factors are important basic input parameters for the estimation of radiation dose to the public around a nuclear power plant. We have carried out a study on air to grass transfer of iodine for a postulated emergency situation. A walk-in environmental chamber was designed and fabricated with facilities for exposing the plants grown in pots to controlled levels of radionuclides/stable elements. The temperature, humidity, and airflow inside the environmental chamber can be controlled to required values. The chamber has the facility for generating artificial rainfall. Grass grown in pots was kept inside the environmental chamber. Stable iodine (elemental form) was sublimed and injected into the environmental chamber suddenly to generate known concentration of iodine in the air inside the chamber. This simulated an accidental release of iodine to the environment. The concentration of iodine in the air inside the chamber was monitored continuously by drawing air from the environmental chamber through a bubbling setup (bubbling air through 1% sodium carbonate solution) and the iodine was then separated chemically and the concentration was measured by UV-VIS spectrometry. The concentration of iodine inside the chamber was monitored for every 30 min. The grass was exposed to iodine for 3 h after which the leaves were sampled and analysed for iodine concentration. From the concentration values of iodine in air and grass - the dry deposition rate, deposition velocity, and mass interception rates were estimated. The dry deposition velocity of iodine varied in the range of 0.5x10{sup -5}-3.3x10{sup -5} m s{sup -1} with a mean value of 1.7x10{sup -5} m s{sup -1}. The mass interception factor varied in the range of 0.25-13 m{sup 2} kg{sup -1} with a mean value of 4.2 m{sup 2} kg{sup -1} with respect to fresh weight. The wet deposition velocity varied in the range

  15. Growth, Mineral Deposition, and Physiological Responses of Broiler Chickens Offered Honey in Drinking Water during Hot-Dry Season

    Directory of Open Access Journals (Sweden)

    Monsuru Oladimeji Abioja

    2012-01-01

    Full Text Available Growing broilers were offered either 0 (0H, 10 (10H, 20 mL (20H honey, or 0.5 g vitamin C/litre water (AA during hot-dry season. Honey had no significant (>0.05 effect on feed intake (FI, weight gain (WG, feed conversion ratio (FCR, water intake (WI, survival (SURV, dressed percentage (DRE, breast meat (BRE, gizzard (GIZ, drumstick (DRU, shank (SHA, thigh (THI, tibia volume (VOL, and magnesium (MAG. Effect of honey was significant (0.005. Higher dose of honey lowered PR and HR. Honey significantly (0.05 affected. 20H broilers had higher THY than 0H and 10H groups. In conclusion, honey did not affect growth but might improve broilers’ welfare when offered up to 20H during hot periods.

  16. Direct and Dry Deposited Single-Walled Carbon Nanotube Films Doped with MoO(x) as Electron-Blocking Transparent Electrodes for Flexible Organic Solar Cells.

    Science.gov (United States)

    Jeon, Il; Cui, Kehang; Chiba, Takaaki; Anisimov, Anton; Nasibulin, Albert G; Kauppinen, Esko I; Maruyama, Shigeo; Matsuo, Yutaka

    2015-07-01

    Organic solar cells have been regarded as a promising electrical energy source. Transparent and conductive carbon nanotube film offers an alternative to commonly used ITO in photovoltaics with superior flexibility. This communication reports carbon nanotube-based indium-free organic solar cells and their flexible application. Direct and dry deposited carbon nanotube film doped with MoO(x) functions as an electron-blocking transparent electrode, and its performance is enhanced further by overcoating with PSS. The single-walled carbon nanotube organic solar cell in this work shows a power conversion efficiency of 6.04%. This value is 83% of the leading ITO-based device performance (7.48%). Flexible application shows 3.91% efficiency and is capable of withstanding a severe cyclic flex test.

  17. Assessment of Hg contamination and exposure to miners and schoolchildren at a small-scale gold mining and recovery operation in Thailand.

    Science.gov (United States)

    Umbangtalad, S; Parkpian, P; Visvanathan, C; Delaune, R D; Jugsujinda, A

    2007-12-01

    Gold extracted by Hg-amalgamation process, which can cause both health and environmental problems, is widespread in South East Asia including Myanmar, Laos, Cambodia, and Thailand. Small-scale gold mining operations have been carried out since the year 2000 in Phanom Pha District, Phichit Province, Thailand. Since no data is available for evaluating Hg exposure, an investigation of mercury (Hg) contamination and exposure assessment was carried out at this mine site. Environmental monitoring illustrated the total Hg in water was as high as 4 microg/l while Hg in sediment ranged between 102 to 325 microg/kg dry weight. Both Hg deposition from the air (1.28 microg/100 cm(2)/day) and concentration in surface soil (20,960 microg/kg dry weight) were elevated in the area of amalgamation. The potential of Hg exposure to miners as well as to schoolchildren was assessed. The concentrations of Hg in urine of 79 miners who were directly (group I) or indirectly (group II) involved in the gold recovery operation were 32.02 and 20.04 microg/g creatinine, respectively, which did not exceed regulatory limits (35 microg/g creatinine). Hair Hg levels in both groups (group I and group II) also were not significantly higher than the non-exposed group. In terms of risk factors, gender and nature of food preparation and consumption were the two significant variables influencing the concentration of Hg in urine of miners (P < 0.05). A hazard quotient (HQ) was estimated based on the inorganic Hg exposure of individual miners. The HQ values of group I were in a range 16 to 218 times higher than the safety level set as 1. By comparison the group II HQ index was very low (0.03-0.39). The miners in group I who worked and ate food from this area experienced potentially high exposure to Hg associated with the mining process. In a second Hg exposure assessment, a group of 59 schoolchildren who attended an elementary school near the gold mine site was evaluated for Hg exposure. A slightly higher

  18. Hg-Mask Coronagraph

    Science.gov (United States)

    Bourget, P.; Veiga, C. H.; Vieira Martins, R.; Assus, P.; Colas, F.

    In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory of Rio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process near the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

  19. Radial line-scans as representative sampling strategy in dried-droplet laser ablation of liquid samples deposited on pre-cut filter paper disks

    Energy Technology Data Exchange (ETDEWEB)

    Nischkauer, Winfried [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna (Austria); Department of Analytical Chemistry, Ghent University, Ghent (Belgium); Vanhaecke, Frank [Department of Analytical Chemistry, Ghent University, Ghent (Belgium); Bernacchi, Sébastien; Herwig, Christoph [Institute of Chemical Engineering, Vienna University of Technology, Vienna (Austria); Limbeck, Andreas, E-mail: Andreas.Limbeck@tuwien.ac.at [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna (Austria)

    2014-11-01

    conventional liquid measurements, and by analyzing IAEA-153 reference material (Trace Elements in Milk Powder); a good agreement with the certified value for phosphorus was obtained. - Highlights: • Sample preparation via deposition of liquids on pre-cut filter disks. • Sample introduction via laser ablation of dried filters. • Representative sampling avoids bias. • Signal quantification via external calibration and aqueous standard solutions. • Alternative approach for quantifying P in challenging matrix.

  20. Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China.

    Science.gov (United States)

    Ma, Ming; Wang, Dingyong; Du, Hongxia; Sun, Tao; Zhao, Zheng; Wei, Shiqing

    2015-12-01

    Atmospheric mercury deposition by wet and dry processes contributes to the transformation of mercury from atmosphere to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to subtropical forests were identified in this study. Throughfall and open field precipitation samples were collected in 2012 and 2013 using precipitation collectors from forest sites located across Mt. Jinyun in southwest China. Samples were collected approximately every 2 weeks and analyzed for total (THg) and methyl mercury (MeHg). Forest canopy was the primary factor on THg and MeHg deposition. Simultaneously, continuous measurements of atmospheric gaseous elemental mercury (GEM) were carried out from March 2012 to February 2013 at the summit of Mt. Jinyun. Atmospheric GEM concentrations averaged 3.8 ± 1.5 ng m(-3), which was elevated compared with global background values. Sources identification indicated that both regional industrial emissions and long-range transport of Hg from central, northeast, and southwest China were corresponded to the elevated GEM levels. Precipitation deposition fluxes of THg and MeHg in Mt. Jinyun were slightly higher than those reported in Europe and North America, whereas total fluxes of MeHg and THg under forest canopy on Mt. Jiuyun were 3 and 2.9 times of the fluxes of THg in wet deposition in the open. Highly elevated litterfall deposition fluxes suggest that even in remote forest areas of China, deposition of atmospheric Hg(0) via uptake by vegetation leaf may be a major pathway for the deposition of atmospheric Hg. The result illustrates that areas with greater atmospheric pollution can be expected to have greater fluxes of Hg to soils via throughfall and litterfall.

  1. Dry powders based on PLGA nanoparticles for pulmonary delivery of antibiotics: modulation of encapsulation efficiency, release rate and lung deposition pattern by hydrophilic polymers.

    Science.gov (United States)

    Ungaro, Francesca; d'Angelo, Ivana; Coletta, Ciro; d'Emmanuele di Villa Bianca, Roberta; Sorrentino, Raffaella; Perfetto, Brunella; Tufano, Maria Antonietta; Miro, Agnese; La Rotonda, Maria Immacolata; Quaglia, Fabiana

    2012-01-10

    Although few experimental studies have been handled so far to exploit the potential of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) in the production of dry powders for antibiotic inhalation, there has been no comprehensive study on the role played by NP composition. In this work, we try to shed light on this aspect by designing and developing a pulmonary delivery system for antibiotics, such as tobramycin (Tb), based on PLGA NPs embedded in an inert microcarrier made of lactose, referred to as nano-embedded micro-particles (NEM). At nanosize level, helper hydrophilic polymers were used to impart the desired surface, bulk and release properties to PLGA NPs prepared by a modified emulsion-solvent diffusion technique. Results showed that poly(vinyl alcohol) (PVA) and chitosan (CS) are essential to optimise the size and modulate the surface properties of Tb-loaded PLGA NPs, whereas the use of alginate (Alg) allows efficient Tb entrapment within NPs and its release up to one month. Optimized formulations display good in vitro antimicrobial activity against P. aeruginosa planktonic cells. Furthermore, spray-drying of the NPs with lactose yielded NEM with peculiar but promising flow and aerosolization properties, while preserving the peculiar NP features. Nonetheless, in vivo biodistribution studies showed that PVA-modified Alg/PLGA NPs reached the deep lung, while CS-modified NPs were found in great amounts in the upper airways, lining lung epithelial surfaces. In conclusion, PLGA NP composition appears to play a crucial role in determining not only the technological features of NPs but, once processed in the form of NEM, also their in vitro/in vivo deposition pattern.

  2. Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

    Science.gov (United States)

    Zhao, Lei; Anderson, Christopher W. N.; Qiu, Guangle; Meng, Bo; Wang, Dingyong; Feng, Xinbin

    2016-04-01

    Rice paddy plantation is the dominant agricultural land use throughout Asia. Rice paddy fields have been identified as important sites for methylmercury (MeHg) production in the terrestrial ecosystem and a primary pathway of MeHg exposure to humans in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete rice-growing season at two different typical Hg-contaminated mining sites in Guizhou province, China: an abandoned site with a high Hg concentration in soil but a low concentration in the atmosphere and a current-day artisanal site with a low concentration in soil but a high concentration in the atmosphere. Our results showed that the flux of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg in soil; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg (IHg). Elevated MeHg concentrations and the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal site demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg in paddy water and surface soil is dependent on elevated Hg in the atmosphere and the consequential deposition of new Hg into a low-pH anoxic geochemical system. The absence of depth-dependent variability in the MeHg concentration in soil cores collected from the abandoned Hg mining site, consistent with the low concentration of Hg in the atmosphere and high pH of the paddy water and irrigation water, suggested that net production of MeHg at this site was limited. We propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

  3. Chemistry, transport and dry deposition of trace gases in the boundary layer over the tropical Atlantic Ocean and the Guyanas during the GABRIEL field campaign

    Directory of Open Access Journals (Sweden)

    A. Stickler

    2007-07-01

    Full Text Available We present a comparison of different Lagrangian and chemical box model calculations with measurement data obtained during the GABRIEL campaign over the tropical Atlantic Ocean and the Amazon rainforest in the Guyanas, October 2005. Lagrangian modelling of boundary layer (BL air constrained by measurements is used to derive a horizontal gradient (≈5.6 pmol/mol km−1 of CO from the ocean to the rainforest (east to west. This is significantly smaller than that derived from the measurements (16–48 pmol/mol km−1, indicating that photochemical production from organic precursors alone cannot explain the observed strong gradient. It appears that HCHO is overestimated by the Lagrangian and chemical box models, which include dry deposition but not exchange with the free troposphere (FT. The relatively short lifetime of HCHO implies substantial BL-FT exchange. The mixing-in of FT air affected by African and South American biomass burning at an estimated rate of 0.12 h−1 increases the CO and decreases the HCHO mixing ratios, improving agreement with measurements. A mean deposition velocity of 1.35 cm/s for H2O2 over the ocean as well as over the rainforest is deduced assuming BL-FT exchange adequate to the results for CO. The measured increase of the organic peroxides from the ocean to the rainforest (≈0.66 nmol/mol d−1 is significantly overestimated by the Lagrangian model, even when using high values for the deposition velocity and the entrainment rate. Our results point at either heterogeneous loss of organic peroxides and/or their radical precursors, underestimated photodissociation or missing reaction paths of peroxy radicals not forming peroxides in isoprene chemistry. We calculate a mean integrated daytime net ozone production (NOP in the BL of (0.2±5.9 nmol/mol (ocean and (2.4±2.1 nmol/mol (rainforest. The NOP strongly correlates with NO and has a positive tendency in

  4. Extrinsic lactose fines improve dry powder inhaler formulation performance of a cohesive batch of budesonide via agglomerate formation and consequential co-deposition.

    Science.gov (United States)

    Kinnunen, Hanne; Hebbink, Gerald; Peters, Harry; Huck, Deborah; Makein, Lisa; Price, Robert

    2015-01-15

    The aim of the study was to investigate how the fine particle content of lactose carriers prepared with different types of lactose fines regulates dry powder inhaler (DPI) formulation performance of a cohesive batch of micronised budesonide. Budesonide formulations (0.8 wt%) were prepared with three different lactose carriers (Lactohale (LH) LH100, 20 wt% LH210 in LH100 and 20 wt% LH300 in LH100). Fine particle fraction of emitted dose (FPFED) and mean mass aerodynamic diameter (MMAD) of budesonide was assessed with a Next Generation Impactor (NGI) using a Cyclohaler at 90 l/min. Morphological and chemical characteristics of particles deposited on Stage 2 were determined using a Malvern Morphologi G3-ID. The results indicate that increasing concentration of lactose fines (lactose particles were available the more agglomerates of budesonide and lactose were delivered to Stage 2. These results suggest drug-fines agglomerate formation is an important mechanism for how lactose fines improve and regulate DPI formulation performance.

  5. Spatial distribution and accumulation of Hg in soil surrounding a Zn/Pb smelter.

    Science.gov (United States)

    Wu, Qingru; Wang, Shuxiao; Wang, Long; Liu, Fang; Lin, Che-Jen; Zhang, Lei; Wang, Fengyang

    2014-10-15

    Nonferrous metal smelting is an important atmospheric mercury (Hg) emission source that has significant local and global impacts. To quantify the impact of Hg emission from non-ferrous metal smelter on the surrounding soil, an integrated model parameterizing the processes of smelter emission, air dispersion, atmospheric deposition and Hg accumulation in soil was developed. The concentrations of gaseous elemental Hg (GEM) around the smelter and the spatial distribution of Hg in the surrounding soil were measured and compared with the model results. Atmospheric deposition of Hg emitted from the smelter was identified as the main source of Hg accumulation in the surrounding soil. From 1960 to 2011, the smelter emitted approximately 105 t of Hg into the atmosphere, of which 15 t deposited locally and resulted in an increase of Hg concentration in soil from 0.12 to 1.77 mg kg(-1). A detailed examination of wind rose and model data suggested that the area within 1.0-1.5 km northwest and southeast of the smelter was most severely impacted. It was estimated that the smelter operation from 1969 to 1990, when large scale emission controls were not implemented, resulted in 6450 μg m(-2)yr(-1) of Hg net deposition and a model simulated increase of 0.40 mg kg(-1) of Hg accumulation in the soil. During the period from 1991 to 2011, atmospheric Hg emission from the smelter alone increased the average concentration in soil from 0.41 mg kg(-1) to 0.45 mg kg(-1). In the past 50 years, over 86% of Hg emitted from this smelter went into the global pool, indicating the importance of controlling Hg emissions from non-ferrous metal smelters.

  6. Dry Eye

    Science.gov (United States)

    ... Eye > Facts About Dry Eye Facts About Dry Eye This information was developed by the National Eye ... the best person to answer specific questions. Dry Eye Defined What is dry eye? Dry eye occurs ...

  7. Estimating mercury emission outflow from East Asia using CMAQ-Hg

    Directory of Open Access Journals (Sweden)

    C.-J. Lin

    2009-10-01

    Full Text Available East Asia contributes nearly 50% of the global anthropogenic mercury emissions into the atmosphere. Recently, there are concerns for the long-range transport of mercury from East Asia to North America, which may lead to enhanced dry and wet depositions in North America. In this study, we performed four monthly simulations (January, April, July and October in 2005 using CMAQ-Hg v4.6 in an East Asian model domain. Coupled with a mass balance analysis and a number of emission inventory scenarios, the chemical transport of atmospheric mercury, the seasonal mercury transport budgets and mercury emission outflow from the East Asian region were investigated. The total annual mercury deposition in the region for the modeling year is estimated to be 821 Mg, with 396 Mg contributed by wet deposition and 425 Mg contributed by dry deposition. Regional mercury transport budgets show strong seasonal variability, with a net removal of RGM (7~5 Mg mo−1 and PHg (13~21 Mg mo−1, and a net export of GEM (60~130 Mg mo−1 from the study domain. The annual outflow caused by the East Asian emission is estimated to be in the range of 1369~1671 Mg yr−1, primarily in the form of GEM. This represents about 75% of the total mercury emissions (anthropogenic and natural in the region. The emission outflow from this source region would contribute to 20~30% of mercury deposition in areas remote from anthropogenic emission sources.

  8. Hg localisation in Tillandsia usneoides L. (Bromeliaceae), an atmospheric biomonitor

    Energy Technology Data Exchange (ETDEWEB)

    Filho, G.M.A. [Instituto de Pesquisas Jardim Botanico do Rio de Janeiro (Brazil). Programa Zona Costeira; Andrade, L.R.; Farina, M. [Cidade Universitaria, Rio de Janeiro (Brazil). Instituto de Ciencias Biomedicas, Departamento de Anatomia; Malm, O. [Cidade Universitaria, Rio de Janeiro (Brazil). Instituto de Biofisica Carlos Chagas Filho, Laboratorio de Radioisotopos Eduardo Penna Franca

    2002-07-01

    The Spanish moss, Tillandsia usneoides, has been applied as an atmospheric biomonitor of Hg contamination, although the mechanism of metal plant accumulation has not been understood until now. In the present work, analytical scanning electron microscopy (SEM) was used to localize Hg in T. usneoides exposed to a Hg-air-contaminated area during 15 days. After this period, Hg was determined by the flow injection mercury system, and plants were prepared for SEM observation and energy-dispersive X-ray analysis. A concentration of 2702{+-}318{mu}g Hgg{sup -1} was determined in exposed plants. The presented microanalytical results demonstrated that Hg was partly associated with atmospheric particles deposited upon the plant surface, but it was highly absorbed by the scales, stem and leaves surfaces and less absorbed by epidermal cells of T. usneoides. No Hg was detected in mesophyll parenchyma or in vascular system cells. The great surface adsorption area provided by the scales, in addition to the characteristics of T. usneoides morphology, especially of the node region, are suggested to confer the great capability of T. usneoides in Hg holding. (author)

  9. Influences of land use and antecedent dry-weather period on pollution level and ecological risk of heavy metals in road-deposited sediment.

    Science.gov (United States)

    Zhang, Jin; Hua, Pei; Krebs, Peter

    2017-09-01

    Road-deposited sediment and its adsorbed pollutants have been regarded as significant sources of urban diffuse pollution. In this study, the solid-phase concentrations (mg/g), surface load (mg/m(2)) and chemical fractionation of zinc (Zn), copper (Cu) and cadmium (Cd) were determined. Geo-accumulation (Igeo) and ecological risk (RI) indexes were employed for metal risk assessment. Results show that the highest solid-phase concentrations of Zn and Cu were usually found at an industrial area. However, Cd had the highest solid-phase concentrations at a rural area, followed by a commercial area. The surface loads of Zn and Cu decreased along the city centre to city border gradient. However, Cd was distributed irregularly. In terms of chemical fractionation, the predominant components of Zn and Cd were identified in the unstable exchangeable fractions, indicating high potential ecological risks to the aquatic environments. Cu posed a comparably low risk due to the high proportions of the stable components of residual and oxidisable fractions. According to a two-dimensional hierarchical cluster analysis, Zn and Cu surface loads were dominantly influenced by the antecedent dry-weather period; Cd contents were strongly land-use type dependent. In addition, the enrichment capability was ranked as Zn > Cu > Cd determined by Igeo index. The sampling site dependent potential ecological risk was determined as rural area (R) > commercial city centre (W) > federal highway (B) > industrial area (I) > main road (S) > secondary road (A) by the RI index. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Hydrothermal synthesis of alpha- and beta-HgS nanostructures

    Science.gov (United States)

    Galain, Isabel; María, Pérez Barthaburu; Ivana, Aguiar; Laura, Fornaro

    2017-01-01

    We synthesized HgS nanostructures by the hydrothermal method in order to use them as electron acceptors in hybrid organic-inorganic solar cells. We employed different mercury sources (HgO and Hg(CH3COO)2) and polyvinylpyrrolidone (PVP) or hexadecanethiol (HDT) as stabilizing/capping agent for controlling size, crystallinity, morphology and stability of the obtained nanostructures. We also used thiourea as sulfur source, and a temperature of 180 °C during 6 h. Synthesized nanostructures were characterized by powder X-Ray Diffraction, Diffuse Reflectance Infrared Fourier Transform and Transmission Electron Microscopy. When PVP acts as stabilizing agent, the mercury source has influence on the size -but not in morphology- of the beta-HgS obtained nansostructures. HDT has control over nanostructures' size and depending on the relation Hg:HDT, we obtained a mixture of alpha and beta HgS which can be advantageous in the application in solar cells, due their absorption in different spectral regions. The smallest nanostructures obtained have a mean diameter of 20 nm when using HDT as capping agent. Also, we deposited the aforementioned nanostructures onto flat glass substrates by the spin coating technique as a first approach of an active layer of a solar cell. The depositions were characterized by atomic force microscopy. We obtained smaller particle deposition and higher particle density -but a lower area coverage (5%) - in samples with HDT as capping agent. This work presents promising results on nanostructures for future application on hybrid solar cells. Further efforts will be focused on the deposition of organic-inorganic layers.

  11. Mercury and methylmercury concentrations and litterfall mass in autumn litterfall samples collected at selected National Atmospheric Deposition Program sites in 2007-2009 and 2012-2015

    Science.gov (United States)

    Risch, Martin R.

    2017-01-01

    Mercury (Hg) is a persistent environmental contaminant and can accumulate and concentrate in food webs as methylmercury (MeHg), presenting a health risk to humans and wildlife. Multiyear monitoring and modeling studies have shown that atmospheric Hg in litterfall is an important form of Hg deposition to forests. Annual litterfall consists primarily of leaves with some amounts of needles, twigs bark, flowers, seeds, fruits, and nuts. Atmospheric Hg accumulates in leaves and reaches an annual maximum concentration at autumn leaf drop. This data set is derived from autumn litterfall collected at 30 selected National Atmospheric Deposition Program (NADP) Mercury Deposition Network (MDN) sites in deciduous and mixed deciduous-coniferous forests from 16 states in the eastern United States during 2007-2009 and 2012-2015. The NADP administered litterfall collection at the MDN sites. The U.S. Geological Survey (USGS) distributed sets of passive litterfall sample collectors to MDN site operators for systematic retrieval of samples during the 8 to 16 weeks of autumn leaf drop each year at each site. Samples were processed and analyzed at the USGS Mercury Research Laboratory where concentrations of Hg and MeHg and litterfall dry mass and sample moisture were determined. All sites did not have data for all years. Most sites had four Hg concentrations per year and a few sites had less than or more than four Hg concentrations in specific years. MeHg concentrations were determined in one composite sample per site in 2007 and 2012-2015. Litterfall mass was determined from 4 to 8 samples per site per year. Seven annual groups of data were compiled into this dataset. More information is available from the NADP at http://nadp.sws.uiuc.edu/

  12. The Upside to Hg-DOM Associations for Water Quality: Removal of Hg from Solution Using Coagulaion with Metal-Based Salts

    Science.gov (United States)

    Henneberry, Y.; Kraus, T. E.; Fleck, J.; Krabbenhoft, D. P.; Horwath, W. R.

    2011-12-01

    This study assessed the potential use of metal-based coagulants to remove dissolved mercury (Hg) from natural waters and provides information regarding the importance of Hg associations with the dissolved organic matter (DOM) fraction and metal hydroxides. Previous research indicated coagulants were not effective at removing Hg from solution; however those studies used high concentrations of Hg, which did not reflect naturally occurring concentrations of Hg. Filtered water collected from an agricultural drain in the Sacramento-San Joaquin Delta (Delta) was treated with three industrial-grade coagulants (ferric chloride, ferric sulfate, and polyaluminum chloride) to determine their efficacy in removing both inroganic (IHg) and methylmercury (MeHg) from the water column. The Delta suffers from elevated surface water Hg concentrations and as a result is listed as an imparied water body. Coagulants removed up to 85% of DOM from solution. In the absence of DOM, all three coagulants released IHg into solution, however in the presence of DOM the coagulants removed up to 97% of IHg and 80% of MeHg. Results suggest that the removal of Hg is mediated by DOM-coagulant interactions. There was a preferential association of IHg with the more aromatic, higher molecular weight fraction of DOM but no such relationship was found for MeHg. This study offers new fundamental insights regarding large-scale removal of Hg at environmentally relevant concentrations. Research using isotopically labeled Hg is providing insight into whether coagulation can remove recently added Hg (e.g. atmospheric deposition) from solution and whether once formed, the floc can remove additional Hg from the water column.

  13. Fluid flow in drying drops

    NARCIS (Netherlands)

    Gelderblom, H.

    2013-01-01

    When a suspension drop evaporates, it leaves behind a drying stain. Examples of these drying stains encountered in daily life are coffee or tea stains on a table top, mineral rings on glassware that comes out of the dishwasher, or the salt deposits on the streets in winter. Drying stains are also pr

  14. Modeling dry and wet deposition of sulfate, nitrate, and ammonium ions in Jiuzhaigou National Nature Reserve, China using a source-oriented CMAQ model: Part II. Emission sector and source region contributions.

    Science.gov (United States)

    Qiao, Xue; Tang, Ya; Kota, Sri Harsha; Li, Jingyi; Wu, Li; Hu, Jianlin; Zhang, Hongliang; Ying, Qi

    2015-11-01

    A source-oriented Community Multiscale Air Quality (CMAQ) model driven by the meteorological fields generated by the Weather Research and Forecasting (WRF) model was used to study the dry and wet deposition of nitrate (NO3(-)), sulfate (SO4(2-)), and ammonium (NH4(+)) ions in the Jiuzhaigou National Nature Reserve (JNNR), China from June to August 2010 and to identify the contributions of different emission sectors and source regions that were responsible for the deposition fluxes. Contributions from power plants, industry, transportation, domestic, biogenic, windblown dust, open burning, fertilizer, and manure management sources to deposition fluxes in JNNR watershed and four EANET sites are determined. In JNNR, 96%, 82%, and 87% of the SO4(2-), NO3(-) and NH4(+) deposition fluxes are in the form of wet deposition of the corresponding aerosol species. Industry and power plants are the two major sources of SO4(2-) deposition flux, accounting for 86% of the total wet deposition of SO4(2-), and industry has a higher contribution (56%) than that of power plants (30%). Power plants and industry are also the top sources that are responsible for NO3(-) wet deposition, and contributions from power plants (30%) are generally higher than those from industries (21%). The major sources of NH4(+) wet deposition flux in JNNR are fertilizer (48%) and manure management (39%). Source-region apportionment confirms that SO2 and NOx emissions from local and two nearest counties do not have a significant impact on predicted wet deposition fluxes in JNNR, with contributions less than 10%. While local NH3 emissions account for a higher fraction of the NH4(+) deposition, approximately 70% of NH4(+) wet deposition in JNNR originated from other source regions. This study demonstrates that S and N deposition in JNNR is mostly from long-range transport rather than from local emissions, and to protect JNNR, regional emission reduction controls are needed. Copyright © 2015 Elsevier B.V. All

  15. Dry and Wet Atmospheric Deposition of Nitrogen into Shaoguan, Guangdong Province%广东韶关地区大气氮干湿沉降特征研究

    Institute of Scientific and Technical Information of China (English)

    刘思言; 陈瑾; 卢平; 李来胜; 陈中颖

    2014-01-01

    2012年4月─2013年9月利用自动分离干湿沉降的采样器对广东省韶关市降雨和干沉降进行采集,分析样品降雨量、降尘量及氮营养盐干湿沉降浓度,计算各指标干湿沉降通量,利用沉降通量分析其影响因素及季节性变化趋势,为该地区大气氮沉降的通量预测及其环境管理提供支持,并为其生态环境中污染物的控制与减排提供科学依据。结果表明,观测期间总氮干沉降通量、湿沉降通量和总沉降通量平均值分别为47.73、295.7和310.5 kg·km-2·month-1。氨态氮、硝酸盐氮与有机氮干沉降通量平均值分别为17.39、12.98和17.37 kg·km-2·month-1,其湿沉降通量平均值分别为132.4、117.0和46.23 kg·km-2·month-1。总氮湿沉降通量占总氮总沉降通量平均比例为83.19%,说明总氮沉降通量以湿沉降为主。影响因素方面,总氮干沉降通量与降尘量无相关性;湿沉降受降雨量影响较大,所以受雨季影响,韶关地区4─6月总氮湿沉降负荷较大。成分组成上,干沉降中氨态氮平均占总氮比例35.48%,硝酸盐氮平均占27.96%,有机氮平均占36.55%,因此该地区氮营养盐干沉降中以氨态氮和有机氮为主;氮营养盐湿沉降以氨态氮和硝酸盐氮为主,氨态氮平均占总氮比例46.87%,硝酸盐氮平均占40.64%,有机氮平均比例为12.49%,说明该地区湿沉降同时受到农业活动和工业活动的影响。季节变化上,氮营养盐干沉降通量由大到小依次为冬季、春季、秋季、夏季,湿沉降通量春季较高,夏秋两季较低。%To help predicate the atmospheric nitrogen deposition fluxes and provide scientific basises for ecological environment pollution control and abatement assist environmental, the characteristics of atmospheric nitrogen deposition in Shaoguan, Guangdong Province were investigated. In the study, the dry and wet atmospheric nitrogen deposition samples

  16. Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA

    Directory of Open Access Journals (Sweden)

    C. Pearson

    2015-01-01

    Full Text Available Bi-weekly snowpack core samples were collected at seven sites along two elevation gradients in the Tahoe Basin during two consecutive snow years to evaluate total wintertime snowpack accumulation of nutrients and pollutants in a high elevation watershed of the Sierra Nevada. Additional sampling of wet deposition and detailed snow pit profiles was conducted the following year to compare wet deposition to snowpack storage and assess the vertical dynamics of snowpack chemicals. Results show that on average organic N comprised 48% of all snowpack N, while nitrate (NO3--N and TAN (total ammonia nitrogen made up 25 and 27%, respectively. Snowpack NO3--N concentrations were relatively uniform across sampling sites over the sampling seasons and showed little difference between seasonal wet deposition and integrated snow pit concentrations in agreement with previous studies that identify wet deposition as the dominant source of wintertime NO3--N deposition. However, vertical snow pit profiles showed highly variable concentrations of NO3--N within the snowpack indicative of additional deposition and in snowpack dynamics. Unlike NO3--N, snowpack TAN doubled towards the end of winter and in addition to wet deposition, had a strong dry deposition component. Organic N concentrations in snowpack were highly variable (from 35 to 70% and showed no clear temporal or spatial dependence throughout the season. Integrated snowpack organic N concentrations were up to 2.5 times higher than seasonal wet deposition, likely due to microbial immobilization of inorganic N as evident by coinciding increases of organic N and decreases of inorganic N, in deeper, aged snowpack. Spatial and temporal deposition patterns of snowpack P were consistent with particulate-bound dry deposition inputs and strong impacts from in-basin sources causing up to 6 times enrichment at urban locations compared to remote sites. Snowpack Hg showed little temporal variability and was dominated by

  17. Dielectric properties of Al2O3 coatings deposited via atmospheric plasma spraying and dry-ice blasting correlated with microstructural characteristics

    Science.gov (United States)

    Dong, Shujuan; Song, Bo; Liao, Hanlin; Coddet, Christian

    2015-01-01

    In this work, atmospheric plasma spraying combined with dry-ice blasting have been used to prepare alumina (Al2O3) coatings designed for insulating applications. The microstructural characteristics and dielectric properties of Al2O3 coatings were presented. The electrical insulating properties, i.e., dielectric strength and breakdown voltage, were investigated by dielectric breakdown test using direct current and alternating current. Relationships between dielectric properties and coating characteristics were discussed. The results showed that dry-ice blasting used during atmospheric plasma spray process allowed the production of coatings with better dielectric properties than those prepared without dry-ice blasting. The dielectric properties were correlated with the microstructural characteristics, not with phase composition.

  18. The redox processes in Hg-contaminated soils from Descoberto (Minas Gerais, Brazil): implications for the mercury cycle.

    Science.gov (United States)

    Windmöller, Cláudia C; Durão Júnior, Walter A; de Oliveira, Aline; do Valle, Cláudia M

    2015-02-01

    Investigations of the redox process and chemical speciation of Hg(II) lead to a better understanding of biogeochemical processes controlling the transformation of Hg(II) into toxic and bioaccumulative monomethyl mercury, mainly in areas contaminated with Hg(0). This study investigates the speciation and redox processes of Hg in soil samples from a small area contaminated with Hg(0) as a result of gold mining activities in the rural municipality of Descoberto (Minas Gerais, Brazil). Soil samples were prepared by adding Hg(0) and HgCl2 separately to dry soil, and the Hg redox process was monitored using thermodesorption coupled to atomic absorption spectrometry. A portion of the Hg(0) added was volatilized (up to 37.4±2.0%) or oxidized (from 36±7% to 88±16%). A correlation with Mn suggests that this oxidation is favored, but many other factors must be evaluated, such as the presence of microorganisms and the types of organic matter present. The interaction of Hg with the matrix is suggested to involve Hg(II)-complexes formed with inorganic and organic sulfur ligands and/or nonspecific adsorption onto oxides of Fe, Al and/or Mn. The kinetics of the oxidation reaction was approximated for two first-order reactions; the faster reaction was attributed to the oxidation of Hg(0)/Hg(I), and the slower reaction corresponded to Hg(I)/Hg(II). The second stage was 43-139 times slower than the first. The samples spiked with Hg(II) showed low volatilization and a shifting of the signal of Hg(II) to lower temperatures. These results show that the extent, rate and type of redox process can be adverse in soils. Descoberto can serve as an example for areas contaminated with Hg(0).

  19. Assessing anthropogenic sources of mercury in soil in Wanshan Hg mining area, Guizhou, China.

    Science.gov (United States)

    Dai, Zhihui; Feng, Xinbin; Zhang, Chao; Wang, Jingfu; Jiang, Taiming; Xiao, Houjun; Li, Yu; Wang, Xun; Qiu, Guangle

    2013-11-01

    Long-term mining and smelting activities brought a series of environmental issues into soils in Wanshan mercury (Hg) mining area (WMMA), Guizhou, China. Several studies have been published on the concentrations of Hg in local soils, but a comprehensive assessment of the mass of Hg in soil induced by anthropogenic activities, as presented in this paper, has not been previously conducted. Three districts of WMMA were chosen as the study areas. We summarized previous published data and sampled 14 typical soil profiles to analyze the spatial and vertical distributions of Hg in soil in the study areas. The regional geologic background, direct and indirect Hg deposition, and Hg-polluted irrigation water were considered as the main sources of Hg contaminations in local soils. Furthermore, the enrichment factor (EF) method was applied to assess the extent of anthropogenic input of Hg to soil. Titanium (Ti) was chosen to be the reference element to calculate the EF. Generally, the elevated values of EF were observed in the upper soil layers and close to mine wastes. The total budget of Hg in soil contributed from anthropogenic sources was estimated to be 1,227 t in arable soil and 75 t in natural soil. Our data showed that arable soil was the major sink of anthropogenic Hg in the study area.

  20. Chemical thermodynamics of the Hg1212 phase

    Science.gov (United States)

    Tsuchiya, Tetsuo; Fueki, Kazuo

    1997-02-01

    The single phase of Hg1212 was synthesized by the simple oxide method using starting materials containing HgO 16% in excess. Stability regions of Hg1212 and pure HgO were determined by measuring the decomposition temperature as a function of oxygen partial pressure, and thermodynamic diagrams showing the stability domains of HgO and Hg1212 were constructed. The thermodynamical condition of formation of Hg1212 was discussed using the diagrams. It was found by chemical analysis that the valence of Hg is always 2 + and the valence of Ce changes with the oxygen content. TC (zero) changed from 122 to 118 K when the oxygen content was increased from 6.10 to 6.22.

  1. A Tropical Paradox - High Mercury Deposition, but Low Mercury Bioaccumulation in Northeastern Puerto Rico

    Science.gov (United States)

    Shanley, J. B.; Marvin-DiPasquale, M. C.; Lane, O.; Arendt, W.; Hall, S. J.

    2016-12-01

    At a "clean air" trade winds site in tropical northeastern Puerto Rico, atmospheric total mercury (THg) deposition averaged 28 µg m-2 yr-1, higher than any site in the USA Mercury Deposition Network, driven by efficient capture of upper tropospheric Hg by high rain-forming clouds. The elevated THg in deposition is reflected in high THg concentrations and flux in streams, but assimilation into the local food web was quite low. There are few mammalian or freshwater fish predators on the island, but 30 faunal samples including fly larvae, freshwater shrimp, spiders, tadpoles, coqui frogs, anole lizards, a scorpion, and a boa constrictor had a median THg concentration of 0.032 µg g-1 (dry weight basis), with the three highest values (near 0.14 µg g-1) from spiders. Avian blood THg concentrations (n=31, from 8 species in various foraging guilds) were also quite low, ranging widely from 0.0002 to 0.032 µg g-1 wet weight, with a median of 0.0043 µg g-1. THg levels in biota were severalfold to more than an order of magnitude lower than comparable values in the continental U.S. These results were surprising given the high Hg inputs and watershed features that would seem to favor methylmercury (MeHg) production (Hg(II)-methylation) - high soil moisture with anoxic zones, ample organic matter and sulfur, and year-round warm temperatures. However, organic soil (0-10 cm) along a hillslope to riparian transect averaged only 0.45 ng/g MeHg, with an average MeHg/THg of only 0.34%. Incubations (n=6) to assess methylation and demethylation indicated that rate constants for demethylation were 6-60 fold greater than those for Hg(II)-methylation, and calculated potential rates of demethylation were 3-9 fold greater than those for Hg(II)-methylation. Thus, the apparent paradox may be resolved by the difference between these rates, whereby MeHg degradation outpaces MeHg production in surface soil and sediment. The interplay of these microbial processes shields the island food web

  2. New technique for quantification of elemental Hg in mine wastes and its implications for mercury evasion into the atmosphere.

    Science.gov (United States)

    Jew, Adam D; Kim, Christopher S; Rytuba, James J; Gustin, Mae S; Brown, Gordon E

    2011-01-15

    Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline α-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica-carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica-carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range.

  3. New technique for quantification of elemental hg in mine wastes and its implications for mercury evasion into the atmosphere

    Science.gov (United States)

    Jew, A.D.; Kim, C.S.; Rytuba, J.J.; Gustin, M.S.; Brown, Gordon E.

    2011-01-01

    Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline ??-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica-carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica-carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range. ?? 2011 American Chemical Society.

  4. Using Simple Science to Influence Corporate Responsibility—A Lesson from Mercury (Hg)

    Science.gov (United States)

    Filippelli, G. M.

    2016-12-01

    Mercury (Hg) is a powerful neurotoxin with wide environmental distribution. Typical population exposure to Hg comes from fish consumption, with fish being the final ecological endpoint of Hg magnification after a series of biogeochemical processes. The emission of Hg from coal-fired power plants has been strongly implicated as a key source of environmental Hg, and thus the target for various public policy initiatives in the US and abroad. We conducted a study of Hg distribution in surface soils over a broad area of central Indiana (US) to understand the major sources of Hg to local fish, and to assess the potential role of policy compliance in reducing Hg. We found a plume-like distribution pattern for soil Hg, with values exceeding 400 ppb Hg in the heart of the plume, and reducing to background concentration of about 30 ppb outside of the plume. The plume covered hundreds of square kilometers, was centered directly over the downtown area of Indianapolis (a city of roughly 1 million inhabitants), and could be roughly backtracked to a source in the southwest corner of the city, coincident with a large coal-fired utility plant that has the highest reported emissions of Hg in the area. Evidence of this link between a local source of Hg and net Hg deposition, with related implications for Hg runoff to local stream, biomagnification to fish, and fish consumption advisories was reported in regional newspapers and eventually published in scientific journals. But importantly, these findings were used by an NGO (the Beyond Coal campaign by Indiana branch of the Sierra Club) at a critical time to influence a decision by the owner of the power plant of whether to comply with the Hg policy rule by either adding higher technology scrubbing technologies to the plant or simply to convert the plant over to natural gas as the fuel source (a costlier choice upfront). The utility chose the latter option, and with the permanent elimination of Hg emissions, the net measurable effects

  5. Radial line-scans as representative sampling strategy in dried-droplet laser ablation of liquid samples deposited on pre-cut filter paper disks

    Science.gov (United States)

    Nischkauer, Winfried; Vanhaecke, Frank; Bernacchi, Sébastien; Herwig, Christoph; Limbeck, Andreas

    2014-11-01

    Nebulising liquid samples and using the aerosol thus obtained for further analysis is the standard method in many current analytical techniques, also with inductively coupled plasma (ICP)-based devices. With such a set-up, quantification via external calibration is usually straightforward for samples with aqueous or close-to-aqueous matrix composition. However, there is a variety of more complex samples. Such samples can be found in medical, biological, technological and industrial contexts and can range from body fluids, like blood or urine, to fuel additives or fermentation broths. Specialized nebulizer systems or careful digestion and dilution are required to tackle such demanding sample matrices. One alternative approach is to convert the liquid into a dried solid and to use laser ablation for sample introduction. Up to now, this approach required the application of internal standards or matrix-adjusted calibration due to matrix effects. In this contribution, we show a way to circumvent these matrix effects while using simple external calibration for quantification. The principle of representative sampling that we propose uses radial line-scans across the dried residue. This compensates for centro-symmetric inhomogeneities typically observed in dried spots. The effectiveness of the proposed sampling strategy is exemplified via the determination of phosphorus in biochemical fermentation media. However, the universal viability of the presented measurement protocol is postulated. Detection limits using laser ablation-ICP-optical emission spectrometry were in the order of 40 μg mL- 1 with a reproducibility of 10 % relative standard deviation (n = 4, concentration = 10 times the quantification limit). The reported sensitivity is fit-for-purpose in the biochemical context described here, but could be improved using ICP-mass spectrometry, if future analytical tasks would require it. Trueness of the proposed method was investigated by cross-validation with

  6. Impacts of Activated Carbon Amendment on Hg Methylation, Demethylation and Microbial Activity in Marsh Soils

    Science.gov (United States)

    Gilmour, C. C.; Ghosh, U.; Santillan, E. F. U.; Soren, A.; Bell, J. T.; Butera, D.; McBurney, A. W.; Brown, S.; Henry, E.; Vlassopoulos, D.

    2015-12-01

    In-situ sorbent amendments are a low-impact approach for remediation of contaminants in sediments, particular in habitats like wetlands that provide important ecosystem services. Laboratory microcosm trials (Gilmour et al. 2013) and early field trials show that activated carbon (AC) can effectively increase partitioning of both inorganic Hg and methylmercury to the solid phase. Sediment-water partitioning can serve as a proxy for Hg and MeHg bioavailability in soils. One consideration in using AC in remediation is its potential impact on organisms. For mercury, a critical consideration is the potential impact on net MeHg accumulation and bioavailability. In this study, we specifically evaluated the impact of AC on rates of methylmercury production and degradation, and on overall microbial activity, in 4 different Hg-contaminated salt marsh soils. The study was done over 28 days in anaerobic, sulfate-reducing slurries. A double label of enriched mercury isotopes (Me199Hg and inorganic 201Hg) was used to separately follow de novo Me201Hg production and Me199Hg degradation. AC amendments decreased both methylation and demethylation rate constants relative to un-amended controls, but the impact on demethylation was stronger. The addition of 5% (dry weight) regenerated AC to soil slurries drove demethylation rate constants to nearly zero; i.e. MeHg sorption to AC almost totally blocked its degradation. The net impact was increased solid phase MeHg concentrations in some of the soil slurries with the highest methylation rate constants. However, the net impact of AC amendments was to increase MeHg (and inorganic Hg) partitioning to the soil phase and decrease concentrations in the aqueous phase. AC significantly decreased aqueous phase inorganic Hg and MeHg concentrations after 28 days. Overall, the efficacy of AC in reducing aqueous MeHg was highest in the soils with the highest MeHg concentrations. The AC addition did not significantly impact microbial activity, as

  7. A Comparison of Mathematical Models of Fish Mercury Concentration as a Function of Atmospheric Mercury Deposition Rate and Watershed Characteristics

    Science.gov (United States)

    Smith, R. A.; Moore, R. B.; Shanley, J. B.; Miller, E. K.; Kamman, N. C.; Nacci, D.

    2009-12-01

    Mercury (Hg) concentrations in fish and aquatic wildlife are complex functions of atmospheric Hg deposition rate, terrestrial and aquatic watershed characteristics that influence Hg methylation and export, and food chain characteristics determining Hg bioaccumulation. Because of the complexity and incomplete understanding of these processes, regional-scale models of fish tissue Hg concentration are necessarily empirical in nature, typically constructed through regression analysis of fish tissue Hg concentration data from many sampling locations on a set of potential explanatory variables. Unless the data sets are unusually long and show clear time trends, the empirical basis for model building must be based solely on spatial correlation. Predictive regional scale models are highly useful for improving understanding of the relevant biogeochemical processes, as well as for practical fish and wildlife management and human health protection. Mechanistically, the logical arrangement of explanatory variables is to multiply each of the individual Hg source terms (e.g. dry, wet, and gaseous deposition rates, and residual watershed Hg) for a given fish sampling location by source-specific terms pertaining to methylation, watershed transport, and biological uptake for that location (e.g. SO4 availability, hill slope, lake size). This mathematical form has the desirable property that predicted tissue concentration will approach zero as all individual source terms approach zero. One complication with this form, however, is that it is inconsistent with the standard linear multiple regression equation in which all terms (including those for sources and physical conditions) are additive. An important practical disadvantage of a model in which the Hg source terms are additive (rather than multiplicative) with their modifying factors is that predicted concentration is not zero when all sources are zero, making it unreliable for predicting the effects of large future reductions in

  8. Sources and cycling of mercury in the paleo Arctic Ocean from Hg stable isotope variations in Eocene and Quaternary sediments

    Science.gov (United States)

    Gleason, J. D.; Blum, J. D.; Moore, T. C.; Polyak, L.; Jakobsson, M.; Meyers, P. A.; Biswas, A.

    2017-01-01

    Mercury stable isotopic compositions were determined for marine sediments from eight locations in the Arctic Ocean Basin. Mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg stable isotopes were recorded across a variety of depositional environments, water depths, and stratigraphic ages. δ202Hg (MDF) ranges from -2.34‰ to -0.78‰; Δ199Hg (MIF) from -0.18‰ to +0.12‰; and Δ201Hg (MIF) from -0.29‰ to +0.05‰ for the complete data set (n = 33). Holocene sediments from the Chukchi Sea and Morris Jesup Rise record the most negative Δ199Hg values, while Pleistocene sediments from the Central Arctic Ocean record the most positive Δ199Hg values. The most negative δ202Hg values are recorded in Pleistocene sediments. Eocene sediments (Lomonosov Ridge) show some overlap in their Hg isotopic compositions with Quaternary sediments, with a sample of the Arctic Ocean PETM (56 Ma) most closely matching the average Hg isotopic composition of Holocene Arctic marine sediments. Collectively, these data support a terrestrially-dominated Hg source input for Arctic Ocean sediment through time, although other sources, as well as influences of sea ice, atmospheric mercury depletion events (AMDEs), and anthropogenic Hg (in core top samples) on Hg isotopic signatures must also be considered.

  9. Influence of the diameter of single-walled carbon nanotube bundles on the optoelectronic performance of dry-deposited thin films

    Directory of Open Access Journals (Sweden)

    Kimmo Mustonen

    2012-10-01

    Full Text Available The optoelectronic performance of thin films of single-walled carbon nanotubes (SWCNTs was studied with respect to the properties of both individual nanotubes and their bundles. The SWCNTs were synthesized in a hot wire generator aerosol reactor, collected by gas filtration and dry-transferred onto various substrates. By thus completely avoiding liquid dispersion steps, we were able to avoid any artifacts from residual surfactants or sonication. We found that bundle lengths determined the thin-film performance, as would be expected for highly resistive bundle–bundle junctions. However, we found no evidence that contact resistances were affected by the bundle diameters, although they did play a secondary role by simply affecting the absorption. The individual SWCNT diameters and their graphitization level as gauged by the Raman D band intensity did not show any clear correlation with the overall performance.

  10. Influence of the diameter of single-walled carbon nanotube bundles on the optoelectronic performance of dry-deposited thin films.

    Science.gov (United States)

    Mustonen, Kimmo; Susi, Toma; Kaskela, Antti; Laiho, Patrik; Tian, Ying; Nasibulin, Albert G; Kauppinen, Esko I

    2012-01-01

    The optoelectronic performance of thin films of single-walled carbon nanotubes (SWCNTs) was studied with respect to the properties of both individual nanotubes and their bundles. The SWCNTs were synthesized in a hot wire generator aerosol reactor, collected by gas filtration and dry-transferred onto various substrates. By thus completely avoiding liquid dispersion steps, we were able to avoid any artifacts from residual surfactants or sonication. We found that bundle lengths determined the thin-film performance, as would be expected for highly resistive bundle-bundle junctions. However, we found no evidence that contact resistances were affected by the bundle diameters, although they did play a secondary role by simply affecting the absorption. The individual SWCNT diameters and their graphitization level as gauged by the Raman D band intensity did not show any clear correlation with the overall performance.

  11. Spatially Modeling the Impact of Terrain on Wind Speed and Dry Particle Deposition Across Lake Perris in Southern California to Determine In Situ Sensor Placement

    Science.gov (United States)

    Brooks, A. N.

    2014-12-01

    While developed countries have implemented engineering techniques and sanitation technologies to keep water resources clean from runoff and ground contamination, air pollution and its contribution of harmful contaminants to our water resources has yet to be fully understood and managed. Due to the large spatial and temporal extent and subsequent computational intensity required to understand atmospheric deposition as a pollutant source, a geographic information system (GIS) was utilized. This project developed a multi-step workflow to better define the placement of in situ sensors on Lake Perris in Southern California. Utilizing a variety of technologies including ArcGIS 10.1 with 3D and Spatial Analyst extensions and WindNinja, the impact of terrain on wind speed and direction was simulated and the spatial distribution of contaminant deposition across Lake Perris was calculated as flux. Specifically, the flux of particulate matter (PM10) at the air - water interface of a lake surface was quantified by season for the year of 2009. Integrated Surface Hourly (ISH) wind speed and direction data and ground station air quality measurements from the California Air Resources Board were processed and integrated for use within ModelBuilder. Results indicate that surface areas nearest Alessandro Island and the dam of Lake Perris should be avoided when placing in situ sensors. Furthermore, the location of sensor placement is dependent on seasonal fluctuations of PM10 which can be modeled using the techniques used in this study.

  12. Hg and As Minerals in Fluid Inclusions from the Williams Mine, Hemlo, and Their Genetic Implications

    Institute of Scientific and Technical Information of China (English)

    LU HUANZHANG(卢焕章); JAYANTA. GUHA; DON. C. HARRIS

    2002-01-01

    The Hemlo mineralization is enigmatic compared to general Archean lode gold deposits based on the fact that it is characterized by an exotic mineralogy containing elements such as As, Hg, Sb, Ba, V and Mo. The genetic concepts range from syngenetic to epigenetic types of mineralization. This reconnaissance study was designed to examine the relationship of Hg-As minerals with respect to fluid inclusions in the Williams mine (formerly known as the Page Williams mine) covering the A and C ore zones.

  13. Sessile nanofluid droplet drying.

    Science.gov (United States)

    Zhong, Xin; Crivoi, Alexandru; Duan, Fei

    2015-03-01

    Nanofluid droplet evaporation has gained much audience nowadays due to its wide applications in painting, coating, surface patterning, particle deposition, etc. This paper reviews the drying progress and deposition formation from the evaporative sessile droplets with the suspended insoluble solutes, especially nanoparticles. The main content covers the evaporation fundamental, the particle self-assembly, and deposition patterns in sessile nanofluid droplet. Both experimental and theoretical studies are presented. The effects of the type, concentration and size of nanoparticles on the spreading and evaporative dynamics are elucidated at first, serving the basis for the understanding of particle motion and deposition process which are introduced afterward. Stressing on particle assembly and production of desirable residue patterns, we express abundant experimental interventions, various types of deposits, and the effects on nanoparticle deposition. The review ends with the introduction of theoretical investigations, including the Navier-Stokes equations in terms of solutions, the Diffusion Limited Aggregation approach, the Kinetic Monte Carlo method, and the Dynamical Density Functional Theory. Nanoparticles have shown great influences in spreading, evaporation rate, evaporation regime, fluid flow and pattern formation of sessile droplets. Under different experimental conditions, various deposition patterns can be formed. The existing theoretical approaches are able to predict fluid dynamics, particle motion and deposition patterns in the particular cases. On the basis of further understanding of the effects of fluid dynamics and particle motion, the desirable patterns can be obtained with appropriate experimental regulations.

  14. Accumulation of heavy metals in dietary vegetables and cultivated soil horizon in organic farming system in relation to atmospheric deposition in a seasonally dry tropical region of India.

    Science.gov (United States)

    Pandey, J; Pandey, Usha

    2009-01-01

    Increasing consciousness about future sustainable agriculture and hazard free food production has lead organic farming to be a globally emerging alternative farm practice. We investigated the accumulation of air-borne heavy metals in edible parts of vegetables and in cultivated soil horizon in organic farming system in a low rain fall tropical region of India. The factorial design of whole experiment consisted of six vegetable crops (tomato, egg plant, spinach, amaranthus, carrot and radish) x two treatments (organic farming in open field and organic farming in glasshouse (OFG)) x seven independent harvest of each crop. The results indicated that except for Pb, atmospheric deposition of heavy metals increased consistently on time scale. Concentrations of heavy metals in cultivated soil horizon and in edible parts of open field grown vegetables increased over time and were significantly higher than those recorded in OFG plots. Increased contents of heavy metals in open field altered soil porosity, bulk density, water holding capacity, microbial biomass carbon, substrate-induced respiration, alkaline phosphatase and fluorescein diacetate hydrolytic activities. Vegetable concentrations of heavy metal appeared in the order Zn > Pb > Cu > Ni > Cd and were maximum in leaves (spinach and amaranths) followed by fruits (tomato and egg plant) and minimum in roots (carrot and radish). Multiple regression analysis indicated that the major contribution of most heavy metals to vegetable leaves was from atmosphere. For roots however, soil appeared to be equally important. The study suggests that if the present trend of atmospheric deposition is continued, it will lead to a destabilizing effect on this sustainable agricultural practice and will increase the dietary intake of toxic metals.

  15. Effects of urbanization on mercury deposition and accumulation in New England.

    Science.gov (United States)

    Chalmers, Ann T; Krabbenhoft, David P; Van Metre, Peter C; Nilles, Mark A

    2014-09-01

    We compare total mercury (HgT) loading and methylmercury (MeHg) accumulation in streams and lakes from an urbanized area (Boston, Massachusetts) to rural regions of southern New Hampshire and Maine. The maximum HgT loading, as indicated by HgT atmospheric deposition, HgT emissions, and sediment HgT concentrations, did not coincide with maximum MeHg concentrations in fish. Urbanized ecosystems were areas of high HgT loading but had low MeHg concentrations in fish. Controls on MeHg production and accumulation appeared to be related primarily to HgT loading in undeveloped areas, while ecosystem sensitivity to MeHg formation appeared to be more important in regulating accumulation of MeHg in the urban area.

  16. Estimates of power deposited via cesium/barium beta and gamma radiation captured in components of a Hanford cesium chloride capsule and by components of overpacked capsules placed in an interim dry storage facility

    Energy Technology Data Exchange (ETDEWEB)

    Roetman, V.E., Westinghouse Hanford

    1996-12-23

    The deposition of power in Hanford cesium chloride capsules and in the components of design concepts for overpacking and interim storage were determined as requested (Randklev, 1996a). The power deposition results from the selective capture of gamma and beta radiation coming from the decay of the 137CS isotope in the CsCl contained in the capsules. The following three cases were analyzed: (a) a single CsCl capsule, (b) an overpack containing eight CsCl capsules, and (c) an infinite square array of such overpacks as placed in tubes of a interim dry storage facility. The power deposition was expressed as watts per gram for each of the respective physical design components in these three cases. Per the analyses request and guidance (Randklev 1996a), the primary analysis objective was to characterize, for each case, the power deposition across the radial cross-section at the expected axial position of maximum deposition. As requested, this primary part of the analysis work was done using choices for component dimension and material properties that would reasonably characterize the maximum deposition profile across the salt (CsCl) and the inner capsule barrier of the double walled metal capsule system used to construct the Hanford capsules. The secondary objective was to further evaluate the deposition behavior relative to the influence of axial position. The guidance (Randklev 1996a) also requested 1797 an analysis case that involved a lag-storage pit in a hot-cell, in which a cylindrical metal basket from a transportation cask would be used to position several capsules in the lag-storage pit. Although the basic model for the lag storage concept evaluation was essentially completed by the end of FY-96, the analysis was not run because of the need to prioritize and limit the work scope due to funding limitations for FY-97. The specific purpose for performing the subject set of analyses (Randklev 1996a) is to obtain power deposition values (i.e., per the decay of T37cs

  17. Hg transfer from contaminated soils to plants and animals

    NARCIS (Netherlands)

    Rodrigues, S.M.; Henriques, B.; Reis, A.T.; Duarte, A.C.; Pereira, E.; Romkens, P.F.A.M.

    2012-01-01

    Understanding the transfer of mercury (Hg) from soil to crops is crucial due to Hg toxicity and Hg occurrence in terrestrial systems. Previous research has shown that available Hg in soils contributes to plant Hg levels. Plant Hg concentrations are related to soil conditions and plant characteristic

  18. Salt-marsh plants as potential sources of Hg0 into the atmosphere

    Science.gov (United States)

    Canário, João; Poissant, Laurier; Pilote, Martin; Caetano, Miguel; Hintelmann, Holger; O'Driscoll, Nelson J.

    2017-03-01

    To assess the role of salt-marsh plants on the vegetation-atmospheric Hg0 fluxes, three salt marsh plant species, Halimione portulacoides, Sarcocornia fruticosa and Spartina maritima were selected from a moderately contaminated site in the Tagus estuary during May 2012. Total mercury in stems and leaves for each plant as well as total gaseous mercury and vegetation-air Hg0 fluxes were measured over two continuous days. Mercury fluxes were estimated with a dynamic flux Tedlar® bag coupled to a high-resolution automated mercury analyzer (Tekran 2537A). Other environmental parameters such as air temperature, relative humidity and net solar radiation were also measured aside. H. portulacoides showed the highest total mercury concentrations in stems and leaves and the highest average vegetation-air Hg0 flux (0.48 ± 0.40 ng Hg m-2 h-1). The continuous measurements converged to a daily pattern for all plants, with enhanced fluxes during daylight and lower flux during the night. It is noteworthy that throughout the measurements a negative flux (air-vegetation) was never observed, suggesting the absence of net Hg0 deposition. Based on the above fluxes and the total area occupied by each species we have estimated the total amount of Hg0 emitted from this salt-marsh plants. A daily emission of 1.19 mg Hg d-1 was predicted for the Alcochete marsh and 175 mg Hg d-1 for the entire salt marsh area of the Tagus estuary.

  19. Electrolytically deposited Cadmium Selenide Films for Photovoltaic Applications

    Directory of Open Access Journals (Sweden)

    Palaiologopoulou M. D.

    2012-10-01

    Full Text Available CdSe films were electrodeposited on pure nickel substrates. The nickel substrate was polished to a mirror finish by Al2O3 paste, etched in 10% HCl solution for 40 s and rinsed thoroughly by de-ionized water. The deposition bath contained solutions with excessive Cd2+ (0.2M from CdSO4 and small amounts of SeO2 (1x10-3 M. The pH of the bath was adjusted to a value of 2.2 at RT by adding 10% H2SO4. The bath was first thermostated at the required temperature, which varied from 55°C to 65°C. Plating was accomplished at deposition potential 1000 mV (vs. Hg/Hg2SO4. The films formed had a uniform thickness and it was found to be approximately 2.0 μm thick (for 20 min electrodeposition process. The produced CdSe films were characterized by X-Ray diffraction and SEM. The induced semiconductor doping effect by thermal annealing in pure dry nitrogen gas was also investigated. Gold contacts were placed on top of the CdSe films, either by evaporation, or mechanically. Depending on the deposition parameters the electrical characteristics of the Ni/CdSe/Au structures may exhibit rectification properties. The optical excitation of the structure was investigated for various CdSe thicknesses.

  20. An ozone budget for the UK: using measurements from the national ozone monitoring network; measured and modelled meteorological data, and a 'big-leaf' resistance analogy model of dry deposition

    Energy Technology Data Exchange (ETDEWEB)

    Coyle, M.; Smith, R.; Fowler, D

    2003-05-01

    A method of calculating a mass budget for O{sub 3} in the UK boundary layer is presented which shows that the spatial scale of the UK is small relative to the footprint of the atmosphere influenced by UK emissions. - Data from the UK national air-quality monitoring network are used to calculate an annual mass budget for ozone (O{sub 3}) production and loss in the UK boundary layer during 1996. Monthly losses by dry deposition are quantified from 1 kmx1 km scale maps of O{sub 3} concentration and O{sub 3} deposition velocities based on a 'big-leaf' resistance analogy. The quantity of O{sub 3} deposition varies from {approx}50 Gg-O{sub 3} month{sup -1} in the winter to over 200 Gg-O{sub 3} month{sup -1} in the summer when vegetation is actively absorbing O{sub 3}. The net O{sub 3} production or loss in the UK boundary layer is found by selecting days when the UK is receiving 'clean' Atlantic air from the SW to NW. In these conditions, the difference in O{sub 3} concentration observed at Mace Head and a rural site on the east coast of the UK indicates the net O{sub 3} production or loss within the UK boundary layer. A simple box model is then used to convert the concentration difference into a mass. The final budget shows that for most of the year the UK is a net sink for O{sub 3} (-25 to -800 Gg-O{sub 3} month{sup -1}) with production only exceeding losses in the photochemically active summer months (+45 Gg-O{sub 3} month{sup -1})

  1. Microbial Oxidation of Hg(0) - Its Effect on Hg Stable Isotope Fractionation and Methylmercury Production

    Energy Technology Data Exchange (ETDEWEB)

    Yee, Nathan [Rutgers Univ., New Brunswick, NJ (United States); Barkay, Tamar [Rutgers Univ., New Brunswick, NJ (United States); Reinfelder, John [Rutgers Univ., New Brunswick, NJ (United States)

    2016-06-28

    Mercury (Hg) associated with mixed waste generated by nuclear weapons manufacturing has contaminated vast areas of the Oak Ridge Reservation (ORR). Neurotoxic methylmercury (MeHg) has been formed from the inorganic Hg wastes discharged into headwaters of East Fork Poplar Creek (EFPC). Thus, understanding the processes and mechanisms that lead to Hg methylation along the flow path of EFPC is critical to predicting the impacts of the contamination and the design of remedial action at the ORR. In part I of our project, we investigated Hg(0) oxidation and methylation by anaerobic bacteria. We discovered that the anaerobic bacterium Desulfovibrio desulfuricans ND132 can oxidize elemental mercury [Hg(0)]. When provided with dissolved elemental mercury, D. desulfuricans ND132 converts Hg(0) to Hg(II) and neurotoxic methylmercury [MeHg]. We also demonstrated that diverse species of subsurface bacteria oxidizes dissolved elemental mercury under anoxic conditions. The obligate anaerobic bacterium Geothrix fermentans H5, and the facultative anaerobic bacteria Shewanella oneidensis MR-1 and Cupriavidus metallidurans AE104 can oxidize Hg(0) to Hg(II) under anaerobic conditions. In part II of our project, we established anaerobic enrichment cultures and obtained new bacterial strains from the DOE Oak Ridge site. We isolated three new bacterial strains from subsurface sediments collected from Oak Ridge. These isolates are Bradyrhizobium sp. strain FRC01, Clostridium sp. strain FGH, and a novel Negativicutes strain RU4. Strain RU4 is a completely new genus and species of bacteria. We also demonstrated that syntrophic interactions between fermentative bacteria and sulfate-reducing bacteria in Oak Ridge saprolite mediate iron reduction via multiple mechanisms. Finally, we tested the impact of Hg on denitrification in nitrate reducing enrichment cultures derived from subsurface sediments from the Oak Ridge site, where nitrate is a major contaminant. We showed that there is an inverse

  2. Microbial Oxidation of Hg(0) - Its Effect on Hg Stable Isotope Fractionation and Methylmercury Production

    Energy Technology Data Exchange (ETDEWEB)

    Yee, Nathan [Rutgers Univ., New Brunswick, NJ (United States); Barkay, Tamar [Rutgers Univ., New Brunswick, NJ (United States); Reinfelder, John [Rutgers Univ., New Brunswick, NJ (United States)

    2016-06-28

    Mercury (Hg) associated with mixed waste generated by nuclear weapons manufacturing has contaminated vast areas of the Oak Ridge Reservation (ORR). Neurotoxic methylmercury (MeHg) has been formed from the inorganic Hg wastes discharged into headwaters of East Fork Poplar Creek (EFPC). Thus, understanding the processes and mechanisms that lead to Hg methylation along the flow path of EFPC is critical to predicting the impacts of the contamination and the design of remedial action at the ORR. In part I of our project, we investigated Hg(0) oxidation and methylation by anaerobic bacteria. We discovered that the anaerobic bacterium Desulfovibrio desulfuricans ND132 can oxidize elemental mercury [Hg(0)]. When provided with dissolved elemental mercury, D. desulfuricans ND132 converts Hg(0) to Hg(II) and neurotoxic methylmercury [MeHg]. We also demonstrated that diverse species of subsurface bacteria oxidizes dissolved elemental mercury under anoxic conditions. The obligate anaerobic bacterium Geothrix fermentans H5, and the facultative anaerobic bacteria Shewanella oneidensis MR-1 and Cupriavidus metallidurans AE104 can oxidize Hg(0) to Hg(II) under anaerobic conditions. In part II of our project, we established anaerobic enrichment cultures and obtained new bacterial strains from the DOE Oak Ridge site. We isolated three new bacterial strains from subsurface sediments collected from Oak Ridge. These isolates are Bradyrhizobium sp. strain FRC01, Clostridium sp. strain FGH, and a novel Negativicutes strain RU4. Strain RU4 is a completely new genus and species of bacteria. We also demonstrated that syntrophic interactions between fermentative bacteria and sulfate-reducing bacteria in Oak Ridge saprolite mediate iron reduction via multiple mechanisms. Finally, we tested the impact of Hg on denitrification in nitrate reducing enrichment cultures derived from subsurface sediments from the Oak Ridge site, where nitrate is a major contaminant. We showed that there is an inverse

  3. Dry and wet atmospheric deposition of organic carbon in coastal and water areas of the northeastern part of the Sea of Azov

    Science.gov (United States)

    Sorokina, V. V.; Soier, V. G.

    2016-09-01

    The paper reports on new data focusing on organic carbon contained in aeolian material and precipitation falling on coastal and water areas of the northeastern part of the Sea of Azov. Atmospheric deposition was sampled in 2006-2014. The particulate organic carbon content varied from 4 to 27% in aeolian dust samples. The concentration of the organic carbon dissolved in rainwater was from 1.6 to 4.3 mg C/L, and from 0.9 to 16.6 mg C/L in snow. The particulate organic carbon content varied from 2 to 43% in snow. Intensity of aeolian dust settling decreased from 178 to 33 mg/m2 per day with distance from a source of dust; in contrast, the relative content of organic matter increased. In a spring-summer season the aeolian organic carbon fluxes varied from 12 to 18 mg C/m2 per day in Rostov-on-Don, from 28 to 48 mg C/m2 per day on the Gulf of Taganrog coast, and from 20 to 80 mg C/m2 per day in the water area of the Gulf of Taganrog.

  4. The influence of carrier roughness on adhesion, content uniformity and the in vitro deposition of terbutaline sulphate from dry powder inhalers.

    Science.gov (United States)

    Flament, Marie-Pierre; Leterme, Pierre; Gayot, Anne

    2004-05-01

    The aim of this study was to establish a correlation between carrier characteristics and the dispersibility of drug from the blend. The influence of the roughness of a commonly used carrier material, lactose monohydrate, on the adhesion, dose uniformity, and aerodynamic properties of a model drug, terbutaline sulphate was investigated. Evaluation of adhesion was carried out with a mechanical sieve and an Alpine air-jet sieve. For the characterisation of lactose roughness, we used image analysis software. Aerodynamic evaluation of fine particle dose and emitted dose was obtained using a twin stage impinger. The study with the mechanical sieve demonstrated that at least 60% of drug adheres to lactose. The Alpine air-jet sieve assays showed there was a correlation between drug separation from a carrier by sieving and that obtained from longer in vitro deposition studies. Adhesion, blend homogeneity and stability are related to the surface roughness of the lactose used as carrier. There is a linear relationship between the parameters "fine particle fraction" and "roughness". A compromise between homogeneity and drug liberation must be found: a certain roughness is necessary to allow for drug adhesion and blend homogeneity, but if too high it will prevent drug liberation after inhalation.

  5. Atmospheric Deposition: Sampling Procedures, Analytical Methods, and Main Recent Findings from the Scientific Literature

    Directory of Open Access Journals (Sweden)

    M. Amodio

    2014-01-01

    Full Text Available The atmosphere is a carrier on which some natural and anthropogenic organic and inorganic chemicals are transported, and the wet and dry deposition events are the most important processes that remove those chemicals, depositing it on soil and water. A wide variety of different collectors were tested to evaluate site-specificity, seasonality and daily variability of settleable particle concentrations. Deposition fluxes of POPs showed spatial and seasonal variations, diagnostic ratios of PAHs on deposited particles, allowed the discrimination between pyrolytic or petrogenic sources. Congener pattern analysis and bulk deposition fluxes in rural sites confirmed long-range atmospheric transport of PCDDs/Fs. More and more sophisticated and newly designed deposition samplers have being used for characterization of deposited mercury, demonstrating the importance of rain scavenging and the relatively higher magnitude of Hg deposition from Chinese anthropogenic sources. Recently biological monitors demonstrated that PAH concentrations in lichens were comparable with concentrations measured in a conventional active sampler in an outdoor environment. In this review the authors explore the methodological approaches used for the assessment of atmospheric deposition, from the analysis of the sampling methods, the analytical procedures for chemical characterization of pollutants and the main results from the scientific literature.

  6. Dry Etching

    DEFF Research Database (Denmark)

    Stamate, Eugen; Yeom, Geun Young

    2016-01-01

    Production of large-area flat panel displays (FPDs) involves several pattern transfer and device fabrication steps that can be performed with dry etching technologies. Even though the dry etching using capacitively coupled plasma is generally used to maintain high etch uniformity, due to the need...... for the higher processing rates in FPDs, high-density plasma processing tools that can handle larger-area substrate uniformly are more intensively studied especially for the dry etching of polysilicon thin films. In the case of FPD processing, the current substrate size ranges from 730 × 920 mm (fourth...... generation) to 2,200 × 2,500 mm (eighth generation), and the substrate size is expected to increase further within a few years. This chapter aims to present relevant details on dry etching including the phenomenology, materials to be etched with the different recipes, plasma sources fulfilling the dry...

  7. Growth, properties and applications of HgCdTe

    Science.gov (United States)

    Schmit, J. L.

    1983-12-01

    This paper provides primarily a review of the methods used to grow HgCdTe with a summary of some of its basic properties and applications. Methods of crystal growth fall generally into three classes: growth from the melt, from solution and from the vapor phase. All three methods have been and are being used to grow HgCdTe. The high vapor pressure of HgCdTe at the melting point, combined with a large segregation coefficient, have effectively limited the use of Czochralski or zone melting techniques, but two melt growth techniques have survived: (1) a variation of Bridgman growth called quench-anneal wherein a dendritic crystal is formed by quenching the melt and is homogenized by solid state recrystallization below the melting point, (2) a variation of freezing from a large volume called slush-growth wherein a melt is held in a temperature gradient for several weeks while a crystal grows. Growth from solution has taken the form of liquid phase epitaxy (LPE) on CdTe with the LPE systems including growth from Hg-rich, HgTe-rich and Te-rich solutions and using tipping, vertical dipping, vertical sliding and horizontal sliding. Vapor phase growth is very promising but is not yet in production. Techniques include growth by isothermal close spaced epitaxy in which HgTe is transported isothermally by chemical potential onto CdTe, molecular beam epitaxy (MBE) in which elements are evaporated in a high vacuum, and metal organic chemical vapor deposition (MOCVD) in which some of the metal atoms are carried to the substrate bound to organic radicals before being freed by pyrolysis. In all these methods, control of Hg pressure is a major concern. The fundamental properties discussed briefly are those of prime interest to detector manufacturers: energy gap ( Eg), intrinsic carrier concentration ( ni), and electrical activity of dopants. A reasonable fit to the Eg data from ˜ 20 papers is given by Eg = -0.302+1.93x+5.35×10 -4T(1-2x)-0.810x 2+0.832x 3. This gap, combined with k

  8. Fabrication and morphology of (Hg,Re)-1212 thin films on LaAlO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Su, J.H.; Sastry, P.V.P.S.S.; Schwartz, J

    2003-04-15

    Superconducting (Hg,Re)Ba{sub 2}CaCu{sub 2}O{sub y} ((Hg,Re)-1212) thin films have been prepared on single crystal substrates of LaAlO{sub 3} by reacting laser deposited ReBaCaCuO precursor films with CaHgO{sub 2} in sealed quartz tubes. The effects of the deposition parameters such as laser fluence and substrate temperature, on surface morphology and microstructure were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM observations revealed that a granular structure was seen in the precursor films deposited at lower energy (less than 200 mJ) and disappeared at higher energy (250 mJ). SEM investigation on final reacted films showed that the precursor films deposited at 250 deg. C resulted in a well-connected and uniformly dense microstructure, whereas the films deposited at lower or higher temperatures were porous and non-uniform.

  9. Barrier formation at graded HgTe/CdTe heterojunctions

    Science.gov (United States)

    Goren, D.; Asa, G.; Nemirovsky, Y.

    1996-11-01

    Numerical calculations of graded HgTe/CdTe heterojunction (HJ) band diagrams at equilibrium are presented and discussed. The calculations are performed in the entire compositional range (0HJs are examined as a function of the graded region width and the graded region doping profiles. The graded region width and doping profiles were found to be the two main factors that determine whether barriers are formed as well as their shape and magnitude. The calculated results indicate that epitaxial ohmic HgTe contacts to extrinsic CdTe are possible, provided that the graded region is wider than one micron, and that it has the same doping type as the doping of the substrate with equal or higher absolute value. Further numerical calculations take into consideration the possible existence of distributed interface charges in the graded region of the HJ. It is shown that by assuming a classical transport over the potential barrier, the effective graded interface charge can be determined from the zero bias differential resistance of the HJ. Experimental transport measurements of metalorganic chemical vapor deposition (MOCVD) grown HgTe/p-CdTe graded HJs show a varying degree of rectification, indicating variations in the graded interface charge distributions which result from different MOCVD growth conditions.

  10. Analysis on Input of Atmospheric Nitrogen Dry Deposition in Urumqi%乌鲁木齐市区大气氮素干沉降的输入性分析

    Institute of Scientific and Technical Information of China (English)

    张伟; 刘学军; 胡玉昆; 李凯辉; 沈健林; 骆晓声; 宋韦

    2011-01-01

    Atmospheric concentrations of NH3,NO2,particulate NH+4(PNH+4) and NO-3(PNO-3) were measured from the samples collected with passive samplers and particulate samplers in Urumqi and its suburbs during the period from August 2009 to March 2010 to estimate atmospheric dry deposition of nitrogen(N) in this region.The results show that NH3 concentration at the Institute of Soil and Fertilizer Research(ISFR,suburban site) was higher than that at the Xinjiang Institute of Ecology and Geography(XIEG,urban site),while the concentrations of other atmospheric reactive N compositions(NO2,particulate NH+4 and NO-3) were higher at XIEG than those at ISFR.The mean concentrations of NH3-N,NO2-N,PNH+4-N,PNO-3-N and PM10(particulate matters with aerodynamic diameter less than 10 μm) at XIEG were 4.49,4.31,2.52,11.84 and 225 μg/m3,and those at ISFR were 4.63,2.32,2.34,7.59 and 188 μg/m3,respectively.Based on the measured concentrations and the dry deposition velocities cited from the references,it was estimated that the atmospheric dry deposition of N was 28.7 kg/(hm2·a) during the sampling period at XIEG and 21.6 kg/(hm2·a) at ISFR,in which the proportion of NHx(NH3+ PNH+4) accounted for 65.7% at XIEG and 69.4% at ISFR,NH3 was dominant during the period from August to November,and PNH+4 was dominant during the period from December to next March.%2009年8月至2010年3月在乌鲁木齐市及城郊,通过大气颗粒物采样器、气体被动采样器对大气氮素干沉降进行连续性监测。结果表明:除NH3浓度值ISFR(土肥所)高于XIEG(生地所)外,其他活性氮成分的浓度XIEG均大于ISFR。NO2-N,NH3-N(气态),PNO 3--N,PNH 4+-N(气溶胶态)和PM10(空气动力学当量直径在10μm以下的颗粒物)在监测点XIEG的平均浓度为4.31,4.49,2.52,11.84,224.66μg/m3,在ISFR的监测值为2.32,4.63,2.34,7.

  11. Distribution and air-sea exchange of mercury (Hg) in polluted marine environments

    Science.gov (United States)

    Bagnato, E.; Sprovieri, M.; Bitetto, M.; Bonsignore, M.; Calabrese, S.; Di Stefano, V.; Oliveri, E.; Parello, F.; Mazzola, S.

    2012-04-01

    measured during the first cruise ranges from about 110 to 1500 ng · m-2day-1. This range is 1-2 order of magnitude higher than most of marine environments (Pacific Ocean, Mediterranean Sea, Artic Ocean) and some important polluted marine areas, such as the Tokyo Bay (19-259 ng · m-2day-1)b and the Yellow Sea (156-722 ng · m-2day-1)c. Further estimates on Hg atmospheric deposition flux (wet and dry) and biomonitoring are required for finally assessing a mass balance of Hg in Augusta basin. aLindberg et al., 2007. A Journal of the Human Environment, 3, 19-33. bNarukawa et al., 2006. Journal of Oceanography, 62, 249-257. cCi et al., 2011. Atmosphere Chemistry and Physics, 11, 2881-2892.

  12. MBE Growth and Transfer of HgCdTe Epitaxial Films from InSb Substrates

    Science.gov (United States)

    de Lyon, T. J.; Rajavel, R. D.; Nosho, B. Z.; Terterian, S.; Beliciu, M. L.; Patterson, P. R.; Chang, D. T.; Boag-O'Brien, M. F.; Holden, B. T.; Jacobs, R. N.; Benson, J. D.

    2010-07-01

    An investigation of the heteroepitaxial growth of HgCdTe films onto InSb(211)B substrates is reported. High-quality HgCdTe(211)B single-crystal films have been successfully deposited onto InSb(211)B substrates and have been characterized with x-ray diffraction rocking curve analysis, etch pit density analysis, and surface void defect mapping. X-ray rocking curve (422) reflection full-width at half-maximum of 60 arcsec has been obtained for 7- μm-thick x = 0.22 HgCdTe epitaxial films, and etch pit densities of 3 × 106 cm-2 to 3 × 107 cm-2 have been observed. A significant reduction in HgCdTe void defect densities to 100 cm-2 to 200 cm-2 has been observed on InSb, including a complete absence of large “void cluster” defects that are often observed for growth on CdZnTe. Wafer bow induced by the growth of HgCdTe on InSb is less than 1 μm for 2-inch-diameter substrates. Significant diffusion of In into HgCdTe is observed for HgCdTe/InSb wafers that are subjected to Hg anneals at 250°C to 300°C. A preliminary investigation of the transfer of HgCdTe films from InSb onto Si substrates has also been undertaken, using an adhesive wafer bonding approach evaluated with scanning acoustic microscopy. The infrared transmission characteristics of the bonding adhesive have been investigated with respect to postgrowth annealing procedures to establish the compatibility of the bonding approach with HgCdTe device processing and detector operation.

  13. In situ compositional control of advanced HgCdTe-based IR detectors

    Science.gov (United States)

    Almeida, L. A.; Dinan, J. H.

    1999-05-01

    The application of a feedback control system for maintaining a desired compositional profile during Hg 1- xCd xTe epitaxy is reported. A spectroscopic ellipsometer monitored the optical properties of Hg 1- xCd xTe films during deposition by molecular beam epitaxy. A library of optical constants was established from in situ measurements of multiple layers of varying composition. The compositions were subsequently determined ex situ using Fourier transform infrared spectroscopy. This work represents an extension of the compositional range of this control system to measure the x-values of Hg 1- xCd xTe sensitive to long-, mid-, and short-wavelength infrared (LWIR, MWIR, and SWIR) radiation (0.16CdTe effusion cell. The application of this control system is demonstrated by measuring the compositional profile of a three layer Hg 1- xCd xTe structure suitable for use as an MWIR/SWIR detector.

  14. Low-Roughness Plasma Etching of HgCdTe Masked with Patterned Silicon Dioxide

    Science.gov (United States)

    Ye, Z. H.; Hu, W. D.; Yin, W. T.; Huang, J.; Lin, C.; Hu, X. N.; Ding, R. J.; Chen, X. S.; Lu, W.; He, L.

    2011-08-01

    A novel mask technique utilizing patterned silicon dioxide films has been exploited to perform mesa etching for device delineation and electrical isolation of HgCdTe third-generation infrared focal-plane arrays (IRFPAs). High-density silicon dioxide films were deposited at temperature of 80°C, and a procedure for patterning and etching of HgCdTe was developed by standard photolithography and wet chemical etching. Scanning electron microscopy (SEM) showed that the surfaces of inductively coupled plasma (ICP) etched samples were quite clean and smooth. Root-mean-square (RMS) roughness characterized by atomic force microscopy (AFM) was less than 1.5 nm. The etching selectivity between a silicon dioxide film and HgCdTe in the samples masked with patterned silicon dioxide films was greater than 30:1. These results show that the new masking technique is readily available and promising for HgCdTe mesa etching.

  15. Engineering steps for optimizing high temperature LWIR HgCdTe photodiodes

    Science.gov (United States)

    Madejczyk, Pawel; Gawron, Waldemar; Martyniuk, Piotr; Keblowski, Artur; Pusz, Wioletta; Pawluczyk, Jaroslaw; Kopytko, Malgorzata; Rutkowski, Jaroslaw; Rogalski, Antoni; Piotrowski, Jozef

    2017-03-01

    The authors report on energy gap engineering solutions to improve the high-temperature performance of long-wave infrared (LWIR) HgCdTe photodiodes. Metalorganic chemical vapour deposition (MOCVD) technology with a wide range of composition and donor/acceptor doping and without ex-situ post grown annealing seems to be an excellent tool for HgCdTe heterostructure epitaxial growth. The heterojunction HgCdTe photovoltaic device based on epitaxial graded gap structures integrated with Auger-suppression is a magnificent solution for high operating temperature (HOT) infrared detectors. The thickness, composition and doping of HgCdTe heterostructure were optimized with respect to photoelectrical parameters like dark current, the responsivity and the response time. In this paper we focus on graded interface abruptness in the progressive optimization.

  16. Emission Spectra of Working Mixtures of a HgBr/HgCl Excimer Lamp

    Science.gov (United States)

    Malinin, A. N.; Guĭvan, N. N.; Shimon, L. L.

    2000-12-01

    A study of emission spectra of a gas-discharge plasma produced in a HgBr/HgCl excimer lamp, which is filled with multicomponent working mixtures at atmospheric pressure (HgBr2 and HgCl2 with additions of molecular nitrogen and xenon), are reported. A gas-discharge plasma was produced by high-frequency (pulses ˜100 ns long with a repetition rate of up to 2000 Hz) barrier and surface discharges, which took place simultaneously. Emission of HgBr* and HgCl* excimer molecules, the second positive system of molecular oxygen, and helium and xenon lines in the UV, visible, and IR spectral regions was observed. The strongest emission of HgBr* and HgCl* molecules (the emission intensities were in the ratio 10:1) was observed in the HgBr2: HgCl2: N2: He mixture. Regularities in spectral and integrated characteristics of gas-discharge plasma emission are discussed.

  17. century drying

    Science.gov (United States)

    Cook, Benjamin I.; Smerdon, Jason E.; Seager, Richard; Coats, Sloan

    2014-11-01

    Global warming is expected to increase the frequency and intensity of droughts in the twenty-first century, but the relative contributions from changes in moisture supply (precipitation) versus evaporative demand (potential evapotranspiration; PET) have not been comprehensively assessed. Using output from a suite of general circulation model (GCM) simulations from phase 5 of the Coupled Model Intercomparison Project, projected twenty-first century drying and wetting trends are investigated using two offline indices of surface moisture balance: the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Evapotranspiration Index (SPEI). PDSI and SPEI projections using precipitation and Penman-Monteith based PET changes from the GCMs generally agree, showing robust cross-model drying in western North America, Central America, the Mediterranean, southern Africa, and the Amazon and robust wetting occurring in the Northern Hemisphere high latitudes and east Africa (PDSI only). The SPEI is more sensitive to PET changes than the PDSI, especially in arid regions such as the Sahara and Middle East. Regional drying and wetting patterns largely mirror the spatially heterogeneous response of precipitation in the models, although drying in the PDSI and SPEI calculations extends beyond the regions of reduced precipitation. This expansion of drying areas is attributed to globally widespread increases in PET, caused by increases in surface net radiation and the vapor pressure deficit. Increased PET not only intensifies drying in areas where precipitation is already reduced, it also drives areas into drought that would otherwise experience little drying or even wetting from precipitation trends alone. This PET amplification effect is largest in the Northern Hemisphere mid-latitudes, and is especially pronounced in western North America, Europe, and southeast China. Compared to PDSI projections using precipitation changes only, the projections incorporating both

  18. Source attribution and process analysis for atmospheric mercury in East China simulated by CMAQ-Hg

    Science.gov (United States)

    Zhu, J.; Wang, T.; Bieser, J.; Matthias, V.

    2015-04-01

    The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), particulate bound mercury (PBM) and mercury deposition in East China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg) modeling system run with nested grid resolution of 27 km. Natural source (NAT) and six categories of anthropogenic mercury sources (ANTH) including cement production (CEM), domestic life (DOM), industrial boilers (IND), metal production (MET), coal-fired power plants (PP) and traffic (TRA) were considered for source apportionment. NAT was responsible for 36.6% of annual averaged GEM concentration which was regard as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentration with a contribution of 86.7 and 79.1% respectively. Among ANTH, IND was the largest contributor for GOM (57.5%) and PBM (34.4%) so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by > 30% contribution to GEM concentration and wet deposition. The contribution from nine processes consisting of emissions (EMIS), gas-phase chemical production/loss (CHEM), horizontal advection (HADV), vertical advection (ZADV), horizontal advection (HDIF), vertical diffusion (VDIF), dry deposition (DDEP), cloud processes (CLDS) and aerosol processes (AERO) were calculated for processes analysis with their comparison in urban and non-urban regions of Yangtze River Delta (YRD). EMIS and VDIF affected surface GEM and PBM concentration most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m-3 reduced in the surface of urban and non-urban areas respectively in a whole day. Diurnal profile variation of processes

  19. Source attribution and process analysis for atmospheric mercury in eastern China simulated by CMAQ-Hg

    Science.gov (United States)

    Zhu, J.; Wang, T.; Bieser, J.; Matthias, V.

    2015-08-01

    The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), particulate bound mercury (PBM) and mercury deposition in eastern China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg) modeling system run with a nested domain. Natural sources (NAT) and six categories of anthropogenic mercury sources (ANTH) including cement production (CEM), domestic life (DOM), industrial boilers (IND), metal production (MET), coal-fired power plants (PP) and traffic (TRA) were considered for source apportionment. NAT were responsible for 36.6 % of annual averaged GEM concentration, which was regarded as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentrations with contributions of 86.7 and 79.1 %, respectively. Among ANTH, IND were the largest contributor for GOM (57.5 %) and PBM (34.4 %) so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by a > 30 % contribution to GEM concentration and wet deposition. The contributions from nine processes - consisting of emissions (EMIS), gas-phase chemical production/loss (CHEM), horizontal advection (HADV), vertical advection (ZADV), horizontal advection (HDIF), vertical diffusion (VDIF), dry deposition (DDEP), cloud processes (CLDS) and aerosol processes (AERO) - were calculated for process analysis with their comparison in urban and non-urban regions of the Yangtze River delta (YRD). EMIS and VDIF affected surface GEM and PBM concentrations most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m-3 reduced in the surface of urban and non-urban areas, respectively, in 1 day. The diurnal profile variation of

  20. Source attribution and process analysis for atmospheric mercury in East China simulated by CMAQ-Hg

    Directory of Open Access Journals (Sweden)

    J. Zhu

    2015-04-01

    Full Text Available The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM, gaseous oxidized mercury (GOM, particulate bound mercury (PBM and mercury deposition in East China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg modeling system run with nested grid resolution of 27 km. Natural source (NAT and six categories of anthropogenic mercury sources (ANTH including cement production (CEM, domestic life (DOM, industrial boilers (IND, metal production (MET, coal-fired power plants (PP and traffic (TRA were considered for source apportionment. NAT was responsible for 36.6% of annual averaged GEM concentration which was regard as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentration with a contribution of 86.7 and 79.1% respectively. Among ANTH, IND was the largest contributor for GOM (57.5% and PBM (34.4% so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by > 30% contribution to GEM concentration and wet deposition. The contribution from nine processes consisting of emissions (EMIS, gas-phase chemical production/loss (CHEM, horizontal advection (HADV, vertical advection (ZADV, horizontal advection (HDIF, vertical diffusion (VDIF, dry deposition (DDEP, cloud processes (CLDS and aerosol processes (AERO were calculated for processes analysis with their comparison in urban and non-urban regions of Yangtze River Delta (YRD. EMIS and VDIF affected surface GEM and PBM concentration most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m−3 reduced in the surface of urban and non-urban areas respectively in a whole day. Diurnal profile variation of processes

  1. HgTe-CdTe SUPERLATTICES

    OpenAIRE

    Smith, D; Mcgill, T.

    1984-01-01

    We report on a theoretical study of the electronic properties of HgTe-CdTe superlattices. The band gap as a function of layer thickness, effective masses normal to the layer plane and tunneling length are compared to the corresponding (Hg, Cd)Te alloys. We find that the superlattice possesses a number of properties that may make it superior to the corresponding alloy as an infrared material.

  2. Hg0 absorption in potassium persulfate solution

    Institute of Scientific and Technical Information of China (English)

    YE Qun-feng; WANG Cheng-yun; WANG Da-hui; SUN Guan; XU Xin-hua

    2006-01-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg0) by potassium persulfate (KPS) catalyzed by Ag+was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg0 concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg0 were studied. The results showed that the removal efficiency of Hg0 increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg0 was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO3. High Hg0 concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed.

  3. 沙尘传输路径上气溶胶浓度与干沉降通量的粒径分布特征%Size-Dependent Mass and Dry Deposition Fluxes of Atmospheric Aerosols along Dust Transport Routes

    Institute of Scientific and Technical Information of China (English)

    闫涵; 高会旺; 姚小红; 石金辉; 于超

    2012-01-01

    Using the size-segregated measurements of atmospheric aerosols collected in Beijing and Qingdao in China and Fukuoka in Japan during the spring of 2002, the size distributions of the mass of atmospheric aerosols with aerodynamic diameter (Dp) ≤ 11 μm (PM11) along dust transport routes are investigated. The size distribution of these aerosols in mass concentration during non-dust periods exhibits a bimodal pattern, i. e. , a fine modes with Dp< 2.1 μm and a coarse mode between 2.1 μm and 11 μm. On the other hand, the size distribution of these aerosols in mass concentration during dust periods attempts to exhibit a uni-modal pattern in the coarse particle size range. The coarse mode diameter decreases with the distance from the dust source zone to the west and east coast oi the Yellow Sea during the heavy dust periods. It is not case in regular dust periods. The size-dependent dry deposition fluxes oi the aerosols over the Yellow Sea in springtime are estimated using an improved Williams' modeL The dry deposition fluxes increase with the increasing size in the coarse particle size range during the non-dust and dust periods. It appears that no evident variations occurred in the fine mode. The estimated PM11 fluxes over the Yellow Sea during the dust and non-dust periods range from 31.70 to 58.59 mg m-2d-1 and ranged from 8. 33 to 15.94 mg · m-2 · d-1, respectively. Although the dry deposition fluxes of the coarse particles increase evidently during dust periods, the relative contributions of the coarse particles to that of PM11 do not change significantly regardless of the occurrence of and absence of dust events. The authors find that coarse particles are the main contributor to the PM11 dry deposition in springtime over the Yellow Sea, the percentage reaches over 94. 2%.%利用2002年春季中国北京、青岛和日本福冈3个地区的分级气溶胶浓度资料,结合改进的Williams模型,分析了沙尘传输路径上空气动力学直径≤11

  4. Spatial Distribution of Mercury (Hg Concentration in Agricultural Soil and Its Risk Assessment on Food Safety in China

    Directory of Open Access Journals (Sweden)

    Shanqian Wang

    2016-08-01

    Full Text Available Soil mercury (Hg pollution in some areas of China is a serious problem and has aroused a lot of attention on a local scale. However, there are few studies on Hg pollution on a national scale. This study collected 444 published papers during 2005–2015 on Hg concentrations in agricultural soil throughout China, under seven land uses, namely: dry land, paddy field, vegetable field, tea garden, orchard, traditional Chinese medicine field and tobacco field, to assess the spatial distribution of Hg concentration and evaluate its influence on food safety. The averaged Hg concentration (0.108 mg/kg was higher than its background (0.065 mg/kg, but much lower than the guidelines (GB15618-1995 II for crop production. The spatial distribution of Hg throughout China showed great variability, with some hotspots due to Hg related mining and smelting activities. According to the Environment Quality Standard for soil in China (GB15618-1995 II, 4.2% of agricultural soil should be abandoned due to Hg pollution, and 2.0% faced a high risk of Hg pollution.

  5. Identification of contamination in a lake sediment core using Hg and Pb isotopic compositions, Lake Ballinger, Washington, USA

    Science.gov (United States)

    Gray, John E.; Pribil, Michael J.; Van Metre, Peter C.; Borrok, David M.; Thapalia, Anita

    2013-01-01

    Concentrations and isotopic compositions of Hg and Pb were measured in a sediment core collected from Lake Ballinger, near Seattle, Washington, USA. Lake Ballinger has been affected by input of metal contaminants emitted from the Tacoma smelter, which operated from 1887 to 1986 and was located about 53 km south of the lake. Concentrations and loadings of Hg and Pb in Lake Ballinger increased by as much as three orders of magnitude during the period of smelting as compared to the pre-smelting period. Concentrations and loadings of Hg and Pb then decreased by about 55% and 75%, respectively, after smelting ended. Isotopic compositions of Hg changed considerably during the period of smelting (δ202Hg = −2.29‰ to −0.38‰, mean −1.23‰, n = 9) compared to the pre-smelting period (δ202Hg = −2.91‰ to −2.50‰, mean −2.75‰, n = 4). Variations were also observed in 206Pb/207Pb and 208Pb/207Pb isotopic compositions during these periods. Data for Δ199Hg and Δ201Hg indicate mass independent fractionation (MIF) of Hg isotopes in Lake Ballinger sediment during the smelting and post-smelting period and suggest MIF in the ore smelted, during the smelting process, or chemical modification at some point in the past. Negative values for Δ199Hg and Δ201Hg for the pre-smelting period are similar to those previously reported for soil, peat, and lichen, likely suggesting some component of atmospheric Hg. Variations in the concentrations and isotopic compositions of Hg and Pb were useful in tracing contaminant sources and the understanding of the depositional history of sedimentation in Lake Ballinger.

  6. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  7. Investigation of Hg uptake and transport between paddy soil and rice seeds combining Hg isotopic composition and speciation

    Directory of Open Access Journals (Sweden)

    C. Feng

    2016-02-01

    Full Text Available Abstract Human consumption of rice constitutes a potential toxicological risk in mercury (Hg polluted areas such as Hg mining regions in China. It is recognized to be an important source of Hg for the local human diet considering the efficient bioaccumulation of methylmercury (MeHg in rice seed. To assess Hg sources and uptake pathways to the rice plants, Hg speciation and isotopic composition were investigated in rice seeds and their corresponding paddy soils from different locations within the Wanshan Hg mining area (Guizhou Province, China. A large variation of Hg speciation is observed in rice seeds and paddy soils irrespective of the sampling location. Mass dependent fractionation (MDF of Hg in rice seeds differs by up to ∼4.0 ‰ in δ202Hg values, while mass independent fractionation (MIF of Hg isotopes remains constant (Δ199Hg ∼ 0‰. Hg isotopic composition in rice seeds covaries with that of paddy soils but exhibits lighter isotopic signature (δ202Hg. Such isotopic offset is mainly attributed to plant uptake and translocation processes. Also, seeds containing higher MeHg (MeHg/total Hg > 50% have significantly heavier Hg isotopes suggesting that MeHg uptake and transport to the seed in such rice plants is facilitated compared to inorganic Hg.

  8. Dry cell battery poisoning

    Science.gov (United States)

    Batteries - dry cell ... Acidic dry cell batteries contain: Manganese dioxide Ammonium chloride Alkaline dry cell batteries contain: Sodium hydroxide Potassium hydroxide Lithium dioxide dry cell batteries ...

  9. Zuotai and HgS differ from HgCl2 and methyl mercury in Hg accumulation and toxicity in weanling and aged rats.

    Science.gov (United States)

    Zhang, Bin-Bin; Li, Wen-Kai; Hou, Wei-Yu; Luo, Ya; Shi, Jing-Zhen; Li, Cen; Wei, Li-Xin; Liu, Jie

    2017-09-15

    Mercury sulfides are used in Ayurvedic medicines, Tibetan medicines, and Chinese medicines for thousands of years and are still used today. Cinnabar (α-HgS) and metacinnabar (β-HgS) are different from mercury chloride (HgCl2) and methylmercury (MeHg) in their disposition and toxicity. Whether such scenario applies to weanling and aged animals is not known. To address this question, weanling (21d) and aged (450d) rats were orally given Zuotai (54% β-HgS, 30mg/kg), HgS (α-HgS, 30mg/kg), HgCl2 (34.6mg/kg), or MeHg (MeHgCl, 3.2mg/kg) for 7days. Accumulation of Hg in kidney and liver, and the toxicity-sensitive gene expressions were examined. Animal body weight gain was decreased by HgCl2 and to a lesser extent by MeHg, but unaltered after Zuotai and HgS. HgCl2 and MeHg produced dramatic tissue Hg accumulation, increased kidney (kim-1 and Ngal) and liver (Ho-1) injury-sensitive gene expressions, but such changes are absent or mild after Zuotai and HgS. Aged rats were more susceptible than weanling rats to Hg toxicity. To examine roles of transporters in Hg accumulation, transporter gene expressions were examined. The expression of renal uptake transporters Oat1, Oct2, and Oatp4c1 and hepatic Oatp2 was decreased, while the expression of renal efflux transporter Mrp2, Mrp4 and Mdr1b was increased following HgCl2 and MeHg, but unaffected by Zuotai and HgS. Thus, Zuotai and HgS differ from HgCl2 and MeHg in producing tissue Hg accumulation and toxicity, and aged rats are more susceptible than weanling rats. Transporter expression could be adaptive means to reduce tissue Hg burden. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Controls on mercury and methylmercury deposition for two watersheds in Acadia National Park, Maine

    Science.gov (United States)

    Johnson, K.B.; Haines, T.A.; Kahl, J.S.; Norton, S.A.; Amirbahman, A.; Sheehan, K.D.

    2007-01-01

    Throughfall and bulk precipitation samples were collected for two watersheds at Acadia National Park, Maine, from 3 May to 16 November 2000, to determine which landscape factors affected mercury (Hg) deposition. One of these watersheds, Cadillac Brook, burned in 1947, providing a natural experimental design to study the effects of forest type on deposition to forested watersheds. Sites that face southwest received the highest Hg deposition, which may be due to the interception of cross-continental movement of contaminated air masses. Sites covered with softwood vegetation also received higher Hg deposition than other vegetation types because of the higher scavenging efficiency of the canopy structure. Methyl mercury (MeHg) deposition was not affected by these factors. Hg deposition, as bulk precipitation and throughfall was lower in Cadillac Brook watershed (burned) than in Hadlock Brook watershed (unburned) because of vegetation type and watershed aspect. Hg and MeHg inputs were weighted by season and vegetation type because these two factors had the most influence on deposition. Hg volatilization was not determined. The total Hg deposition via throughfall and bulk precipitation was 9.4 ??g/m2/year in Cadillac Brook watershed and 10.2 ??g/m2/year in Hadlock Brook watershed. The total MeHg deposition via throughfall and bulk precipitation was 0.05 ??g/m2/year in Cadillac Brook watershed and 0.10 ??g/m2/year in Hadlock Brook watershed. ?? Springer Science + Business Media B.V. 2006.

  11. Spatial-temporal dynamics and sources of total Hg in a hydroelectric reservoir in the Western Amazon, Brazil.

    Science.gov (United States)

    Pestana, I A; Bastos, W R; Almeida, M G; de Carvalho, D P; Rezende, C E; Souza, C M M

    2016-05-01

    Damming rivers to construct hydroelectric reservoirs results in a series of impacts on the biogeochemical Hg cycle. For example, modifying the hydrodynamics of a natural watercourse can result in the suspension and transport of Hg deposits in the water column, which represents an exposure risk for biota. The objective of this study was to evaluate the influences of seasonality on the dispersion of total Hg in the Hydroelectric Power Plant (HPP)-Samuel Reservoir (Porto Velho/Brazil). Sampling campaigns were performed during the three following hydrological periods characteristic of the region: low (Oct/2011), ebbing (May/2012), and high (Feb/2013) water. Sediment profiles, suspended particulate matter (SPM), and aquatic macrophytes (Eicchornia crassipes and Oryza spp.) were collected, and their Hg concentrations and isotopic and elemental C and N signatures were determined. The drainage basin significantly influenced the SPM compositions during all the periods, with a small autochthonous influence from the reservoir during the low water. The highest SPM Hg concentrations inside the reservoir were observed during the high water period, suggesting that the hydrodynamics of this environment favor the suspension of fine SPM, which has a higher Hg adsorption capacity. The Hg concentrations in the sediment profiles were ten times lower than those in the SPM, indicating that large particles with low Hg concentrations were deposited to form the bottom sediment. Hg concentrations were higher in aquatic macrophyte roots than in their leaves and appeared to contribute to the formation of SPM during the low water period. In this environment, Hg transport mainly occurs in SPM from the Jamari River drainage basin, which is the primary source of Hg in this environment.

  12. Local probing of Hg neighboorhood in HgBa$_{2}$CuO$_{4+\\delta}$

    CERN Document Server

    Correia, J G; Loureiro, S M; Toulemonde, P; Le Floc'h, S; Bordet, P; Capponi, J J; Gatt, R; Tröger, W; Ctortecka, B; Butz, T; Haas, H; Marques, J G; Soares, J C

    2000-01-01

    Electric field gradients (EFG) on mercury sites of the Hg1201 high-TC superconductors were measured with the perturbed angular correlation (PAC) technique. In Hg1201 samples where PAC detects higher oxygen content the EFGs have decreased to lower values indicating an elongation of the Hg-apical oxygen dumb-bell. On the same samples the asymmetry parameter of the EFG becomes non-zero below 100 K, showing that the charge distribution near the Hg-apical oxygen chain becomes non-axially symmetric at low temperature.

  13. Complexation of Hg with phytochelatins is important for plant Hg tolerance.

    Science.gov (United States)

    Carrasco-Gil, Sandra; Alvarez-Fernández, Ana; Sobrino-Plata, Juan; Millán, Rocío; Carpena-Ruiz, Ramón O; Leduc, Danika L; Andrews, Joy C; Abadía, Javier; Hernández, Luís E

    2011-05-01

    Three-week-old alfalfa (Medicago sativa), barley (Hordeum vulgare) and maize (Zea mays) were exposed for 7 d to 30 µm of mercury (HgCl(2) ) to characterize the Hg speciation in root, with no symptoms of being poisoned. The largest pool (99%) was associated with the particulate fraction, whereas the soluble fraction (SF) accounted for a minor proportion (phytochelatins (PCs) in root SF, which was particularly varied in alfalfa (eight ligands and five stoichiometries), a species that also accumulated homophytochelatins. Spatial localization of Hg in alfalfa roots by microprobe synchrotron X-ray fluorescence spectroscopy showed that most of the Hg co-localized with sulphur in the vascular cylinder. Extended X-ray Absorption Fine Structure (EXAFS) fingerprint fitting revealed that Hg was bound in vivo to organic-S compounds, i.e. biomolecules containing cysteine. Albeit a minor proportion of total Hg, Hg-PCs complexes in the SF might be important for tolerance to Hg, as was found with Arabidopsis thaliana mutants cad2-1 (with low glutathione content) and cad1-3 (unable to synthesize PCs) in comparison with wild type plants. Interestingly, high-performance liquid chromatography-electrospray ionization-time of flight analysis showed that none of these mutants accumulated Hg-biothiol complexes.

  14. Dry release of suspended nanostructures

    DEFF Research Database (Denmark)

    Forsén, Esko Sebastian; Davis, Zachary James; Dong, M.;

    2004-01-01

    A dry release method for fabrication of suspended nanostructures is presented. The technique has been combined with an anti-stiction treatment for fabrication of nanocantilever based nanoelectromechanical systems (NEMS). The process combines a dry release method, using a supporting layer of photo......A dry release method for fabrication of suspended nanostructures is presented. The technique has been combined with an anti-stiction treatment for fabrication of nanocantilever based nanoelectromechanical systems (NEMS). The process combines a dry release method, using a supporting layer......, the technique enables long time storage and transportation of produced devices without the risk of stiction. By combining the dry release method with a plasma deposited anti-stiction coating both fabrication induced stiction, which is mainly caused by capillary forces originating from the dehydration...

  15. Atmospheric wet deposition of mercury and other trace elements in Pensacola, Florida

    Directory of Open Access Journals (Sweden)

    W. M. Landing

    2010-05-01

    Full Text Available In an effort to understand and quantify the impact of local, regional, and far-distant atmospheric mercury sources to rainfall mercury deposition in the Pensacola, Florida watershed, a program of event-based rainfall sampling was started in late 2004. Modified Aerochem-Metrics wet/dry rainfall samplers were deployed at three sites in the region around the Crist coal-fired power plant and event-based samples were collected continuously for three years. Samples were analyzed for total Hg and a suite of trace elements including Al, As, Ba, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Sb, Se, Si, Sn, Sr, Th, U, V, and Zn. Nutrients (ammonia and nitrate and major anions (chloride and sulfate were also measured on each sample. Multivariate statistical methods were used to sort these tracers into factors that represent potential source categories contributing to the rainfall chemistry. As, Hg, Sb, Se, Sn, and non sea-salt sulfate were all significantly correlated (R>0.6 with one factor which we interpret as an anthropogenic source term reflecting input from coal combustion throughout the southeastern US. Using ratios of total Hg to volatile elements, we estimate that 22–33% of the rainfall Hg results from coal combustion in the southeastern US with the majority coming from the global background.

  16. Magnetic fields of HgMn stars

    CERN Document Server

    Hubrig, S; Ilyin, I; Korhonen, H; Schoeller, M; Savanov, I; Arlt, R; Castelli, F; Curto, G Lo; Briquet, M; Dall, T H

    2012-01-01

    The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. We re-analyse available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD65949 and the hotter analog of HgMn stars, the PGa star HD19400, using FORS2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. We downloaded from the ESO archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudina...

  17. HgCdTe barrier infrared detectors

    Science.gov (United States)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  18. Dry Mouth

    Science.gov (United States)

    ... Use a fluoride rinse or brush-on fluoride gel before bedtime. See your dentist at least twice yearly to have your teeth examined and plaque removed, to help prevent tooth decay. Several herbal remedies have been used historically to treat dry ...

  19. Complexation of Hg with phytochelatins is important for plant Hg tolerance

    National Research Council Canada - National Science Library

    CARRASCO‐GIL, SANDRA; ÁLVAREZ‐FERNÁNDEZ, ANA; SOBRINO‐PLATA, JUAN; MILLÁN, ROCÍO; CARPENA‐RUIZ, RAMÓN O; LEDUC, DANIKA L; ANDREWS, JOY C; ABADÍA, JAVIER; HERNÁNDEZ, LUÍS E

    2011-01-01

    Three‐week‐old alfalfa ( Medicago sativa ), barley ( Hordeum vulgare ) and maize ( Zea mays ) were exposed for 7 d to 30  µ m of mercury (HgCl 2 ) to characterize the Hg speciation in root, with no symptoms of being poisoned...

  20. Temporal Characteristics of Emission of Working Mixtures of a HgBr/HgCl Excimer Lamp

    Science.gov (United States)

    Malinin, A. N.; Guĭvan, N. N.; Shimon, L. L.; Polyak, A. V.; Zubrilin, N. G.; Shchedrin, A. I.

    2001-12-01

    Results of a study of temporal characteristics of the emission of gas-discharge plasma of atmospheric pressure in multicomponent mixtures (mercury dibromide and dichloride with helium and additions of molecular nitrogen and xenon) of working media of HgBr/HgCl excimer lamps are presented. Gas-discharge plasma was produced and components of the working mixture were excited by high-frequency barrier and surface discharges occurring simultaneously. The repetition rate of the pumping pulse and its duration are 1000 Hz and ˜100 ns, respectively. It is found that the amplitude and the length of emission pulses and their trailing edge are modified in HgBr2: HgCl2: Xe: He and HgBr2: HgCl2: N2: He mixtures when xenon and molecular nitrogen are added, as compared to a HgBr2: HgCl2: He mixture. Regularities observed in temporal characteristics of gas-discharge plasma emission are discussed.

  1. Ground-state potential energy curves of LiHg, NaHg, and KHg revisited

    Science.gov (United States)

    Thiel, Linda; Hotop, Hartmut; Meyer, Wilfried

    2003-11-01

    We present the results of large-scale CCSD(T) calculations on the potential energy curves for the ground states of LiHg, NaHg, and KHg. In these calculations, the Hg20+ core is simulated by a pseudopotential which has been adjusted to reproduce experimental excitation and ionization energies of the Hg atom at the coupled-cluster level. Moreover, we apply a weighted multiproperty fitting procedure to determine reliable potentials for LiHg, NaHg, and KHg which reproduce the available experimental results. In the case of LiHg, this best-fit potential is based solely on experimental data and its agreement with our calculated potential supports our computational procedure. For NaHg and KHg the experimental data had to be complemented by theoretical results in order to fix a best-fit potential. Our potentials and those proposed previously are evaluated by comparing calculated scattering cross sections and vibrational energy levels with the available experimental data.

  2. Quasiparticle excitations in superdeformed {sup 192}Hg

    Energy Technology Data Exchange (ETDEWEB)

    Lauritsen, T.; Carpenter, M.P.; Janssens, R.V.F. [and others

    1995-08-01

    The nucleus {sup 192}Hg plays a pivotal role for superdeformation in the mass 190 region, since calculations of single-particle levels show large shell-gaps for the superdeformed (SD) shape at N = 112 and Z = 80. As a result, {sup 192}Hg is referred to as the doubly magic SD nucleus for the A = 190 region. In previous studies, only one superdeformed band was observed in this nucleus, and this fact was cited as indirect evidence that large shell gaps do indeed exist at the proposed particle numbers.

  3. Electric field gradients in Hg compounds

    DEFF Research Database (Denmark)

    Arcisauskaité, Vaida; Knecht, Stefan; Sauer, Stephan P. A.

    2012-01-01

    We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved by compar......We examine the performance of Density Functional Theory (DFT) approaches based on the Zeroth-Order Regular Approximation (ZORA) Hamiltonian (with and without inclusion of spinorbit coupling) for predictions of electric ¿eld gradients (EFGs) at the heavy atom Hg nucleus. This is achieved...

  4. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Written By: Kierstan Boyd Reviewed By: ... your eyes do not produce enough tears, it is called dry eye. Dry eye is also when ...

  5. Changes in Sport Fish Mercury Concentrations from Food Web Shifts Suggest Partial Decoupling from Atmospheric Deposition in Two Colorado Reservoirs.

    Science.gov (United States)

    Wolff, Brian A; Johnson, Brett M; Lepak, Jesse M

    2017-02-01

    Partial decoupling of mercury (Hg) loading and observed Hg concentrations ([Hg]) in biotic and abiotic samples has been documented in aquatic systems. We studied two Colorado reservoirs to test whether shifts in prey for sport fish would lead to changes in [Hg] independent of external atmospheric Hg deposition. We compared sport fish total mercury concentrations ([T-Hg]) and macroinvertebrate (chironomids and crayfish) methylmercury concentrations ([MeHg]) before and after food web shifts occurred in both reservoirs. We also monitored wet atmospheric Hg deposition and sediment [T-Hg] and [MeHg] at each reservoir. We found rapid shifts in Hg bioaccumulation in each reservoir's sport fish, and these changes could not be attributed to atmospheric Hg deposition. Our study shows that trends in atmospheric deposition, environmental samples (e.g., sediments), and samples of species at the low trophic levels (e.g., chironomids and crayfish) may not accurately reflect conditions that result in fish consumption advisories for high trophic level sport fish. We suggest that in the short-term, monitoring fish [Hg] is necessary to adequately protect human health because natural and anthropogenic perturbations to aquatic food-webs that affect [Hg] in sport fish will continue regardless of trends in atmospheric deposition.

  6. Growing rice aerobically markedly decreases mercury accumulation by reducing both Hg bioavailability and the production of MeHg.

    Science.gov (United States)

    Wang, Xun; Ye, Zhihong; Li, Bing; Huang, Linan; Meng, Mei; Shi, Jianbo; Jiang, Guibin

    2014-01-01

    Rice consumption represents a major route of mercury (Hg) and methylmercury (MeHg) exposure for those living in certain areas of inland China. In this study we investigated the effects of water management on bioavailable Hg, MeHg, and sulfate-reducing bacteria (SRB, abundance and community composition) in rhizosphere soil, and total Hg (THg) and MeHg in rice plants grown under glasshouse and paddy field conditions. Aerobic conditions greatly decreased the amount of THg and MeHg taken up by rice plants and affected their distribution in different plant tissues. There were positive correlations between bioavailable Hg and THg in brown rice and roots and between numbers of SRB and MeHg in brown rice, roots, and rhizosphere soil. Furthermore, the community composition of SRB was dramatically influenced by the water management regimes. Our results demonstrate that the greatly reduced bioavailability of Hg and production of MeHg are due to decreased SRB numbers and proportion of Hg methylators in the rhizosphere under aerobic conditions. These are the main reasons for the reduced Hg and MeHg accumulation in aerobically grown rice. Water management is indicated as an effective measure that can be used to reduce Hg and MeHg uptake by rice plants from Hg-contaminated paddy fields.

  7. Effect of Mercury Deposition on Mercury Content and Distribution in Rye Grass

    Institute of Scientific and Technical Information of China (English)

    WEISHIQIANG; J.SOMMAR; 等

    1997-01-01

    A grass(Italian rye grass)experiment with complete desing of three factos(Hg,grass and exposure)and two levels(with and withou the factor tested)was carried out in Goeteborg,Sweden from May to September,1995,toward understanding the effect of mercury deposition on plant Hg content and its distribution.It has been found that besides the two general pathways of Hg absorption,i.e.root uptake and foliar absorption,mercury deposition can aslo signifcantly incease Hg content and total load in grass.Such effects seem to be confined only within the above-ground parts of grass plant.Estimate has been made to make clear of the contributions of different pathways to Hg Content and total Hg load in the upper part of grass.Results showed that the contribution of Hg deposition accounted for 27%-32%,of Hg content in the above-ground parts of grass plant without adding Hg to the soil.decreasing with the increase of soil and/or air Hg concentrations.The increment of Hg load in the upper part of grass plant caused by Hg deposition during an interval of two weeks varied between 0.01-0.07μg pt-1,contributing to 17%-48% of the total Hg load in grass plant exposed.

  8. Behavior of solid matters and heavy metals during conductive drying process of sewage sludge

    Directory of Open Access Journals (Sweden)

    Jianping Luo

    2016-12-01

    Full Text Available Behavior of solid matters and heavy metals during conductive drying process of sewage sludge was evaluated in a sewage sludge disposal center in Beijing, China. The results showed most of solid matters could be retained in the dried sludge after drying. Just about 3.1% of solid matters were evaporated with steam mainly by the form of volatile fatty acids. Zn was the dominant heavy metal in the sludge, followed by Cu, Cr, Pb, Ni, Hg, and Cd. The heavy metals in the condensate were all below the detection limit except Hg. Hg in the condensate accounted for less than 0.1% of the total Hg. It can be concluded that most of the heavy metals are also retained in the dried sludge during the drying process, but their bioavailability could be changed significantly. The results are useful for sewage sludge utilization and its condensate treatment.

  9. 40 CFR 60.45Da - Standard for mercury (Hg).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for mercury (Hg). 60.45Da... for mercury (Hg). (a) For each coal-fired electric utility steam generating unit other than an IGCC... gases that contain mercury (Hg) emissions in excess of each Hg emissions limit in paragraphs...

  10. MBE Growth and Characterization of Hg Based Compounds and Heterostructures

    Science.gov (United States)

    2002-06-03

    The molecular beam epitaxy ( MBE ) growth of Mercury Cadmium Telluride (Hg(1-x)Cd(x)Te) alloys and type III HgTe/Hg(1-x)Cd(x)Te heterostructures has...been discussed, including similarities and differences between the (0 0 1) and (1 1 2)Beta orientations. Furthermore, the MBE growth of HgTe-based

  11. Phenylselenolate Mercury Alkyl Compounds, PhSeHgMe and PhSeHgEt: Molecular Structures, Protolytic Hg-C Bond Cleavage and Phenylselenolate Exchange.

    Science.gov (United States)

    Yurkerwich, Kevin; Quinlivan, Patrick J; Rong, Yi; Parkin, Gerard

    2016-01-08

    The phenylselenolate mercury alkyl compounds, PhSeHgMe and PhSeHgEt, have been structurally characterized by X-ray diffraction, thereby demonstrating that both compounds are monomeric with approximately linear coordination geometries; the mercury centers do, nevertheless, exhibit secondary Hg•••Se intermolecular interactions that serve to increase the coordination number in the solid state. The ethyl derivative, PhSeHgEt, undergoes facile protolytic cleavage of the Hg-C bond to release ethane at room temperature, whereas PhSeHgMe exhibits little reactivity under similar conditions. Interestingly, the cleavage of the Hg-C bond of PhSeHgEt is also more facile than that of the thiolate analogue, PhSHgEt, which demonstrates that coordination by selenium promotes protolytic cleavage of the mercury-carbon bond. The phenylselenolate compounds PhSeHgR (R = Me, Et) also undergo degenerate exchange reactions with, for example, PhSHgR and RHgCl. In each case, the alkyl groups preserve coupling to the (199)Hg nuclei, thereby indicating that the exchange process involves metathesis of the Hg-SePh/Hg-X groups rather than metathesis of the Hg-R/Hg-R groups.

  12. The application of 199Hg NMR and 199mHg perturbed angular correlation (PAC) spectroscopy to define the biological chemistry of HgII

    DEFF Research Database (Denmark)

    Iranzo, Olga; Thulstrup, Peter Waaben; Ryu, Seung-baek;

    2007-01-01

    H values and at peptide/HgII ratios of 3:1 with an unusual trigonal thiolate coordination mode. The resulting HgII complexes are good water-soluble models for HgII binding to the protein MerR. We have carried out a parallel study using 199Hg NMR and 199mHg perturbed angular correlation (PAC) spectroscopy...... to characterize the distinct species that are generated under different pH conditions and peptide TRI L9C/HgII ratios. These studies prove for the first time the formation of [Hg{(TRI L9C)2-(TRI L9C H)}], a dithiolate-HgII complex in the hydrophobic interior of the three-stranded coiled coil (TRI L9C)3. 199Hg NMR...... and 199mHg PAC data demonstrate that this dithiolate-HgII complex is different from the dithiolate [Hg(TRI L9C)2], and that the presence of third -helix, containing a protonated cysteine, breaks the symmetry of the coordination environment present in the complex [Hg(TRI L9C)2]. As the pH is raised...

  13. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; Gonzalez, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have fai...

  14. Mercury speciation in wet deposition samples collected from a coastal area of Minamata Bay

    Science.gov (United States)

    Marumoto, Kohji; Matsuyama, Akito

    2014-04-01

    To better understand the methylation and demethylation of mercury (Hg) in the atmosphere, monomethyl mercury (MMHg) concentrations in wet deposition samples collected in the Minamata Bay area from September, 2009 to August, 2010 were determined. The concentrations of total Hg (dissolved Hg + particulate Hg) and dissolved reactive Hg were also measured. The volume-weighted mean concentrations of dissolved MMHg and total Hg were 0.061 and 5.9 ng L-1, respectively. Almost 90% of total Hg was in the dissolved phase and dissolved reactive Hg was the dominant Hg species in the wet deposition. The wet deposition fluxes of total Hg and reactive Hg increased in the rainy season (summer and fall), while the concentrations and wet deposition fluxes of MMHg were higher in winter and spring than in summer. Factors affecting this seasonal variation of MMHg were also considered. The MMHg in wet depositions may be decomposed by the increased levels of UV radiation in summer months, although MMHg can also be emitted from anthropogenic and biogenic sources and/or produced by photochemical reactions. Long-range transport from the Asian continent may also contribute to the seasonal variation of the wet MMHg deposition flux.

  15. Relationship Between Soil Properties and Different Fractions of Soil Hg

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing, China. Results showed that clay (< 2 m) could increase water-soluble Hg (r = 0.700*). Soil organic matter (OM) could enhance the increase of elemental Hg (r = 0.674*). The higher the base saturation percentage (BSP), the more the residual Hg (r = 0.684*). Organic Hg, the sum of acid-soluble organic Hg. and alkali-soluble Hg, was positively affected by silt (2~20μm) but negatively affected by pH, with the direct path coefficients amounting to 1.0487 and 0.5121, respectively. The positive effect of OM and negative effect of BSP on organic Hg were the most significant, with the direct path coefficients being 0.7614 and -0.8527, respectively. The indirect effect of clay (< 2 μm) via BSP (path coefficient = 0.4186) was the highest, showing that the real influencing factor in the effect of clay (< 2 μm) on acid-soluble organic Hg was BSP. Since the available Hg fraction, water-soluble Hg, was positively affected by soil clay content, and the quite immobile and not bioavailable residual Hg by soil BSP, suitable reduction of clay content and increase of BSP would be of much help to reduce the Hg availability and Hg activity in Hg-contaminated soils.

  16. Particulate-phase mercury emissions from biomass burning and impact on resulting deposition: a modelling assessment

    Science.gov (United States)

    De Simone, Francesco; Artaxo, Paulo; Bencardino, Mariantonia; Cinnirella, Sergio; Carbone, Francesco; D'Amore, Francesco; Dommergue, Aurélien; Feng, Xin Bin; Gencarelli, Christian N.; Hedgecock, Ian M.; Landis, Matthew S.; Sprovieri, Francesca; Suzuki, Noriuki; Wängberg, Ingvar; Pirrone, Nicola

    2017-02-01

    Mercury (Hg) emissions from biomass burning (BB) are an important source of atmospheric Hg and a major factor driving the interannual variation of Hg concentrations in the troposphere. The greatest fraction of Hg from BB is released in the form of elemental Hg (Hg0(g)). However, little is known about the fraction of Hg bound to particulate matter (HgP) released from BB, and the factors controlling this fraction are also uncertain. In light of the aims of the Minamata Convention to reduce intentional Hg use and emissions from anthropogenic activities, the relative importance of Hg emissions from BB will have an increasing impact on Hg deposition fluxes. Hg speciation is one of the most important factors determining the redistribution of Hg in the atmosphere and the geographical distribution of Hg deposition. Using the latest version of the Global Fire Emissions Database (GFEDv4.1s) and the global Hg chemistry transport model, ECHMERIT, the impact of Hg speciation in BB emissions, and the factors which influence speciation, on Hg deposition have been investigated for the year 2013. The role of other uncertainties related to physical and chemical atmospheric processes involving Hg and the influence of model parametrisations were also investigated, since their interactions with Hg speciation are complex. The comparison with atmospheric HgP concentrations observed at two remote sites, Amsterdam Island (AMD) and Manaus (MAN), in the Amazon showed a significant improvement when considering a fraction of HgP from BB. The set of sensitivity runs also showed how the quantity and geographical distribution of HgP emitted from BB has a limited impact on a global scale, although the inclusion of increasing fractions HgP does limit Hg0(g) availability to the global atmospheric pool. This reduces the fraction of Hg from BB which deposits to the world's oceans from 71 to 62 %. The impact locally is, however, significant on northern boreal and tropical forests, where fires are

  17. One-step green synthesis and characterization of plant protein-coated mercuric oxide (HgO) nanoparticles: antimicrobial studies

    Science.gov (United States)

    Das, Amlan Kumar; Marwal, Avinash; Sain, Divya; Pareek, Vikram

    2015-03-01

    The present study demonstrates the bioreductive green synthesis of nanosized HgO using flower extracts of an ornamental plant Callistemon viminalis. The flower extracts of Callistemon viminalis seem to be environmentally friendly, so this protocol could be used for rapid production of HgO. Till date, there is no report of synthesis of nanoparticles using flower extract of Callistemon viminalis. Mercuric acetate was taken as the metal precursor in the present experiment. The flower extract was found to act as a reducing as well as a stabilizing agent. The phytochemicals present in the flower extract act as reducing agent which include proteins, saponins, phenolic compounds, phytosterols, and flavonoids. FT-IR spectroscopy confirmed that the extract had the ability to act as a reducing agent and stabilizer for HgO nanoparticles. The formation of the plant protein-coated HgO nanoparticles was first monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of HgO nanoparticles by exhibiting the typical surface plasmon absorption maxima at 243 nm. The average particle size formed ranges from 2 to 4 nm. The dried form of synthesized nanoparticles was further characterized using TGA, XRD, TEM, and FTIR spectroscopy. FT-IR spectra of synthesized HgO nanoparticles were performed to identify the possible bio-molecules responsible for capping and stabilization of nanoparticles, which confirm the formation of plant protein-coated HgO nanoparticles that is further corroborated by TGA study. The optical band gap of HgO nanoparticle was measured to be 2.48 eV using cutoff wavelength which indicates that HgO nanoparticles can be used in metal oxide semiconductor-based photovoltaic cells. A possible core-shell structure of the HgO nanobiocomposite has been proposed.

  18. Hg/HgO electrode and hydrogen evolution potentials in aqueous sodium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Nickell, Ryan A.; Zhu, Wenhua H.; Payne, Robert U.; Cahela, Donald R.; Tatarchuk, Bruce J. [Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, 230 Ross Hall, Auburn University, Auburn, AL 36849 (United States)

    2006-10-27

    The Hg/HgO electrode is usually utilized as a reference electrode in alkaline solution such as for development of an alkaline hydrogen electrode. The reference electrode provides a suitable reference point but is available from few commercial vendors and suffers from inadequate documentation on potential in varying electrolytes. A new numerical method uses activity, activity coefficients, and a few correlated empirical equations to determine the potential values in both dilute and concentrated sodium hydroxide solutions at temperatures of 0-90{sup o}C and at concentrations of 0.100-12.8mol kg{sub H{sub 2}O}{sup -1}. The computed potentials of the Hg/HgO electrodes versus a normal hydrogen electrode (NHE) at 25{sup o}C and 1atm are 0.1634V for 0.100m, 0.1077V for 1.00m, and 0.0976V for 1.45m NaOH solutions. The Hg/HgO reduction potential further changes to -0.0751V versus NHE and hydrogen evolution potential changes to -0.9916V versus NHE in a solution of 30.0wt.% NaOH at 80{sup o}C. The calculated values are compared with the measured data at 25 and 75{sup o}C. The experimental data agree well with the numerical values computed from the theoretical and empirical equations. (author)

  19. Hg/HgO electrode and hydrogen evolution potentials in aqueous sodium hydroxide

    Science.gov (United States)

    Nickell, Ryan A.; Zhu, Wenhua H.; Payne, Robert U.; Cahela, Donald R.; Tatarchuk, Bruce J.

    The Hg/HgO electrode is usually utilized as a reference electrode in alkaline solution such as for development of an alkaline hydrogen electrode. The reference electrode provides a suitable reference point but is available from few commercial vendors and suffers from inadequate documentation on potential in varying electrolytes. A new numerical method uses activity, activity coefficients, and a few correlated empirical equations to determine the potential values in both dilute and concentrated sodium hydroxide solutions at temperatures of 0-90 °C and at concentrations of 0.100-12.8 mol k gH2O-1 . The computed potentials of the Hg/HgO electrodes versus a normal hydrogen electrode (NHE) at 25 °C and 1 atm are 0.1634 V for 0.100m, 0.1077 V for 1.00m, and 0.0976 V for 1.45m NaOH solutions. The Hg/HgO reduction potential further changes to -0.0751 V versus NHE and hydrogen evolution potential changes to -0.9916 V versus NHE in a solution of 30.0 wt.% NaOH at 80 °C. The calculated values are compared with the measured data at 25 and 75 °C. The experimental data agree well with the numerical values computed from the theoretical and empirical equations.

  20. Mercury stable isotope signatures of world coal deposits and historical coal combustion emissions.

    Science.gov (United States)

    Sun, Ruoyu; Sonke, Jeroen E; Heimbürger, Lars-Eric; Belkin, Harvey E; Liu, Guijian; Shome, Debasish; Cukrowska, Ewa; Liousse, Catherine; Pokrovsky, Oleg S; Streets, David G

    2014-07-01

    Mercury (Hg) emissions from coal combustion contribute approximately half of anthropogenic Hg emissions to the atmosphere. With the implementation of the first legally binding UNEP treaty aimed at reducing anthropogenic Hg emissions, the identification and traceability of Hg emissions from different countries/regions are critically important. Here, we present a comprehensive world coal Hg stable isotope database including 108 new coal samples from major coal-producing deposits in South Africa, China, Europe, India, Indonesia, Mongolia, former USSR, and the U.S. A 4.7‰ range in δ(202)Hg (-3.9 to 0.8‰) and a 1‰ range in Δ(199)Hg (-0.6 to 0.4‰) are observed. Fourteen (p coal Hg emissions tracing. A revised coal combustion Hg isotope fractionation model is presented, and suggests that gaseous elemental coal Hg emissions are enriched in the heavier Hg isotopes relative to oxidized forms of emitted Hg. The model explains to first order the published δ(202)Hg observations on near-field Hg deposition from a power plant and global scale atmospheric gaseous Hg. Yet, model uncertainties appear too large at present to permit straightforward Hg isotope source identification of atmospheric forms of Hg. Finally, global historical (1850-2008) coal Hg isotope emission curves were modeled and indicate modern-day mean δ(202)Hg and Δ(199)Hg values for bulk coal emissions of -1.2 ± 0.5‰ (1SD) and 0.05 ± 0.06‰ (1SD).

  1. Characteristics and Source Apportionment of Water-soluble Ions in Dry Deposition in the Summer and Autumn of Nanjing%南京夏秋季节大气干沉降水溶性离子特征及来源分析

    Institute of Scientific and Technical Information of China (English)

    秦阳; 朱彬; 邹嘉南; 庞博

    2016-01-01

    A total of 84 effective dry deposition samples were collected from July to October, 2014 in Nanjing, and the chemical composition and source apportionment of water-soluble ions dry deposition in the summer and autumn season were discussed. The results indicated that the average pH was 6. 2, and the dry deposition samples usually appeared neutral. Ca2 + and NH +4 were the major cations and their average daily concentrations were 115. 7 μeq•L - 1 and 31. 2 μeq•L - 1 ,accounting for 68. 3% and 18. 6% of total cations, respectively. SO2 -4 , Cl - and NO2 -3 were the main anions, and their average daily concentrations were 30. 4, 20. 7 and 18. 7μeq•L - 1 , a total of 89. 2% of the total anions, respectively. High temperature and humidity of meteorological factors and contaminated air mass affected dry deposition. Local air mass had greater impact on dry deposition pollution, which indicated that dry deposition pollution had local property. In summer and autumn seasons in Nanjing, the stationary sources had more contributions to atmospheric dry deposition of water-soluble ions than mobile sources, while the environmental control measures for the Nanjing Youth Olympic Games had greater effect on stationary sources than mobile sources. Studies of the origins of major ions indicated that SO2 -4 and NO2 -3 were mostly attributed by the anthropogenic activities, and Cl - was mainly from ocean sources, while K + and Mg2 + were mostly from the terrestrial input.%本研究利用采集的2014年7~10月南京地区84个有效干沉降样品,探讨了南京夏秋季节大气干沉降中水溶性离子的化学组成及其来源.结果表明南京夏秋季干沉降样品平均 pH 为6.2,干沉降偏中性. Ca2+和 NH +4是主要的阳离子,日均浓度分别为115.7μeq•L -1和31.2μeq•L -1,分别占阳离子总量的68.3%和18.6%.阴离子以 SO2-4、 Cl -和 NO2-3为主,日均浓度为30.4、20.7和18.7μeq•L -1,共占总阴离子的89.2%.干沉降浓度变

  2. A Micrometeorological Perspective on Deposition

    DEFF Research Database (Denmark)

    Jensen, Niels Otto

    1981-01-01

    An expression for the dry deposition velocity is given in terms of constant flux layer scaling. Numerical values of upper bounds on the deposition velocity is given for a typical situation. Some remarks are then offered on the relative merits of various ways in which the combined diffusion...

  3. MBE HgCdTe heterostructure detectors

    Science.gov (United States)

    Schulman, Joel N.; Wu, Owen K.

    1990-01-01

    HgCdTe has been the mainstay for medium (3 to 5 micron) and long (10 to 14 micron) wavelength infrared detectors in recent years. Conventional growth and processing techniques are continuing to improve the material. However, the additional ability to tailor composition and placement of doped layers on the tens of angstroms scale using molecular beam epitaxy (MBE) provides the opportunity for new device physics and concepts to be utilized. MBE-based device structures to be discussed here can be grouped into two categories: tailored conventional structures and quantum structures. The tailored conventional structures are improvements on familiar devices, but make use of the ability to create layers of varying composition, and thus band gap, at will. The heterostructure junction can be positioned independently of doping p-n junctions. This allows the small band gap region in which the absorption occurs to be separated from a larger band gap region in which the electric field is large and where unwanted tunneling can occur. Data from hybrid MBE/liquid phase epitaxy (LPE)/bulk structures are given. Quantum structures include the HgTe-CdTe superlattice, in which the band gap and transport can be controlled by alternating thin layers (tens of angstroms thick) of HgTe and CdTe. The superlattice has been shown to exhibit behavior which is non-alloy like, including very high hole mobilities, two-dimensional structure in the absorption coefficient, resonant tunneling, and anisotropic transport.

  4. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Eye Symptoms Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Written By: Kierstan Boyd ... your vision. Privacy Policy Related New Dry Eye Treatment is a Tear-Jerker Jul 21, 2017 Three ...

  5. Can Nassarius reticulatus be used as a bioindicator for Hg contamination? Results from a longitudinal study of the Portuguese coastline.

    Science.gov (United States)

    Coelho, J P; Pimenta, J; Gomes, R; Barroso, C M; Pereira, M E; Pardal, M A; Duarte, A

    2006-06-01

    The focus of this work is to explore the use of the netted whelk, Nassarius reticulatus (L.), as an indicator of mercury (Hg) contamination, by assessing the concentration of Hg in the sediments and in the whelk along the entire Portuguese coast. Total Hg concentrations ranged from below the detection limit (0.01 ng absolute mercury) up to 0.87 mg kg(-1) dry weight (dwt) in sediments and between 0.06 and 1.02 mg kg(-1) (dwt) for organisms, with no significant differences between males and females. Although organic mercury was not detected in the sediments, it represented, on average, 52% of the total Hg in the whelk tissues, and as high as 88% in some cases, suggesting mercury accumulation from dietary intake. Significant negative correlations were found between the total Hg concentrations in the sediments and the log(10) of Hg concentrations in whelk tissues males (r=-0.64; P<0.01) and females (r=-0.52; P<0.01) indicating that the species is a poor indicator of Hg contamination. Nevertheless, since the highest concentrations of organic mercury in the whelk tissues were found in the least contaminated areas, this species must be highly relevant in the trophic web, namely on the possible biomagnification of mercury. The high dietary mercury accumulation from feeding on carrion and the low bioavailability of mercury to whelks in estuarine sediments may be the basis of the mercury accumulation pattern in N. reticulatus.

  6. Atmospheric deposition of mercury in Atlantic Forest and ecological risk to soil fauna

    Science.gov (United States)

    Cristhy Buch, Andressa; Cabral Teixeira, Daniel; Fernandes Correia, Maria Elizabeth; Vieira Silva-Filho, Emmanoel

    2014-05-01

    The increasing levels of mercury (Hg) found in the atmosphere nowadays has a great contribution from anthropogenic sources and has been a great concern in the past two decades in industrialized countries. Brazil is the seventh country with the highest rate of mercury in the atmosphere. Certainly, the petroleum refineries have significant contribution, seen that 100 million m3 of crude oil are annually processed. These refineries contribute with low generation of solid waste; however, a large fraction of Hg can be emitted to the atmosphere. There are sixteen refineries in Brazil, three of them located in the state of Rio de Janeiro. The Hg is a toxic and hazardous trace element, naturally found in the earth crust. The major input of Hg to ecosystems is through atmospheric deposition (wet and dry), being transported in the atmosphere over large distances. The forest biomes are of great importance in the atmosphere/soil cycling of elemental Hg through foliar uptake and subsequent transfer to the soil through litterfall, which play an important role as Hg sink. The Atlantic Forest of Brazil is the greater contributor of fauna and flora biodiversity in the world and, according to recent studies, this biome has the highest concentrations of mercury in litter in the world, as well as in China, at Subtropical Forest. Ecotoxicological assessments can predict the potential ecological risk of Hg toxicity in the soil can lead to impact the soil fauna and indirectly other trophic levels of the food chain within one or more ecosystems. This study aims to determine mercury levels that represent risks to diversity and functioning of soil fauna in tropical forest soils. The study is conducted in two forest areas inserted into conservation units of Rio de Janeiro state. One area is located next to an important petroleum refinery in activity since fifty-two years ago, whereas the other one is located next to other refinery under construction (beginning activities in 2015), which will

  7. The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, Laura S., E-mail: lsaylors@umich.edu [University of Michigan, Department of Earth and Environmental Sciences, 1100 N. University Ave., Ann Arbor, MI 48109 (United States); Blum, Joel D. [University of Michigan, Department of Earth and Environmental Sciences, 1100 N. University Ave., Ann Arbor, MI 48109 (United States); Dvonch, J. Timothy [University of Michigan, Air Quality Laboratory, 1415 Washington Heights, Ann Arbor, MI 48109 (United States); Gratz, Lynne E. [University of Washington-Bothell, 18115 Campus Way NE, Bothell, WA 98011 (United States); Landis, Matthew S. [U.S. EPA, Office of Research and Development, Research Triangle Park, NC 27709 (United States)

    2015-01-01

    The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) present human health and environmental concerns. Although it is known that local and regional sources of these metals contribute to deposition in the Great Lakes region, it is difficult to trace emissions from point sources to impacted sites. Recent studies suggest that metal isotope ratios may be useful for distinguishing between and tracing source emissions. We measured Pb, strontium (Sr), and Hg isotope ratios in daily precipitation samples that were collected at seven sites across the Great Lakes region between 2003 and 2007. Lead isotope ratios ({sup 207}Pb/{sup 206}Pb = 0.8062 to 0.8554) suggest that Pb deposition was influenced by coal combustion and processing of Mississippi Valley-Type Pb ore deposits. Regional differences in Sr isotope ratios ({sup 87}Sr/{sup 86}Sr = 0.70859 to 0.71155) are likely related to coal fly ash and soil dust. Mercury isotope ratios (δ{sup 202}Hg = − 1.13 to 0.13‰) also varied among the sites, likely due to regional differences in coal isotopic composition, and fractionation occurring within industrial facilities and in the atmosphere. These data represent the first combined characterization of Pb, Sr, and Hg isotope ratios in precipitation collected across the Great Lakes region. We demonstrate the utility of multiple metal isotope ratios in parallel with traditional trace element multivariate statistical modeling to enable more complete pollution source attribution. - Highlights: • We measured Pb, Sr, and Hg isotopes in precipitation from the Great Lakes region. • Pb isotopes suggest that deposition was impacted by coal combustion and metal production. • Sr isotope ratios vary regionally, likely due to soil dust and coal fly ash. • Hg isotopes vary due to fractionation occurring within facilities and the atmosphere. • Isotope results support conclusions of previous trace element receptor modeling.

  8. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Español Eye Health / Eye Health A-Z Dry Eye Sections What Is Dry Eye? Dry Eye Symptoms ... Dry Eye Dry Eye Treatment What Is Dry Eye? Written By: Kierstan Boyd Reviewed By: Brenda Pagan- ...

  9. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Español Eye Health / Eye Health A-Z Dry Eye Sections What Is Dry Eye? Dry Eye Symptoms ... Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué Es el Ojo Seco? ...

  10. Long-distance transport of Hg, Sb, and As from a mined area, conversion of Hg to methyl-Hg, and uptake of Hg by fish on the Tiber River basin, west-central Italy

    Science.gov (United States)

    Gray, John E.; Rimondi, Valentina; Costagliola, Pilario; Vaselli, Orlando; Lattanzi, Pierfranco

    2014-01-01

    Stream sediment, stream water, and fish were collected from a broad region to evaluate downstream transport and dispersion of mercury (Hg) from inactive mines in the Monte Amiata Hg District (MAMD), Tuscany, Italy. Stream sediment samples ranged in Hg concentration from 20 to 1,900 ng/g, and only 5 of the 17 collected samples exceeded the probable effect concentration for Hg of 1,060 ng/g, above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in Tiber River sediment varied from 0.12 to 0.52 ng/g, and although there is no established guideline for sediment methyl-Hg, these concentrations exceeded methyl-Hg in a regional baseline site (Sb (Sb) and for protection against chronic effects to aquatic wildlife (150 μg/L for As and 5.6 μg/L for Sb). Concentrations of Hg in freshwater fish muscle ranged from 0.052–0.56 μg/g (wet weight), mean of 0.17 μg/g, but only 17 % (9 of 54) exceeded the 0.30 μg/g (wet weight) USEPA fish muscle guideline recommended to protect human health. Concentrations of Hg in freshwater fish in this region generally decreased with increasing distance from the MAMD, where fish with the highest Hg concentrations were collected more proximal to the MAMD, whereas all fish collected most distal from Hg mines contained Hg below the 0.30 μg/g fish muscle guideline. Data in this study indicate some conversion of inorganic Hg to methyl-Hg and uptake of Hg in fish on the Paglia River, but less methylation of Hg and Hg uptake by freshwater fish in the larger Tiber River.

  11. Hg Vetical Transference in Soil—Water System

    Institute of Scientific and Technical Information of China (English)

    GUOYIJUN; MOUSUSEN; 等

    1998-01-01

    Hg vertial transference in soil-water system was studied by analyzing Hg vertical ditribution in soil column after adding Hg and one of the two leacheates,deionzied water or acid rain,into soil column.The results indicated that Hg was hardly transferable in puple soil.About 86%-88% of the total soil Hg was distributed in the top layer (0-2cm) and to Hg was detected in the leakage when the purple soil column was leached by deionized water and simulated acid rain.But Hg was more movalbe in yellow soil with only about 20%-22% of the total soil Hg distributed in the top layer (0-2cm),and about 17%-25% washed out from the soil column by deionized water and simulted acid rain,Incremant in soil bulk density colud reduce Hg leaching,thus the more the Hg kept in soil,the less the Hg leached into underground water,Deionized water and acid rain almost played the same role in leaching Hg.Bentioint was most effecient in preventing Hg from vertcal transferring in the soil coulumn.

  12. Assessing the Emission Sources of Atmospheric Mercury in Wet Deposition Across Illinois, USA

    Directory of Open Access Journals (Sweden)

    Gratz L. E.

    2013-04-01

    Full Text Available From August 2007 to August 2009, we collected event-based precipitation samples for mercury (Hg and trace element analysis at four sites in Illinois, USA. The objectives of these measurements were to quantify the levels of Hg wet deposition across the state, and to assess the contributions to Hg in precipitation from major local and regional emission sources. The measurement sites were located in Chicago, Peoria, Nilwood, and Carbondale, IL. We were not able to identify a clear spatial gradient in Hg wet deposition among the sites. At all four locations we frequently observed Hg concentrations in precipitation > 25 ng/L, while each site received > 10 μg/m2 of Hg wet deposition annually, suggesting a substantial impact from local and regional anthropogenic emission sources. We applied the multivariate statistical receptor model Positive Matrix Factorization (PMF to the measured Hg and trace element wet deposition amounts at the four sites. The results suggested that 60-83% of total Hg deposition at each site could be attributed to coal combustion emissions. Although we identified other source signatures in the precipitation composition, including cement manufacturing, metal smelting / waste incineration, and iron-steel production, these sources contributed substantially less to the measured amounts of Hg wet deposition. We also applied the hybrid receptor model Quantitative Transport Bias Analysis (QTBA to the Hg wet deposition data from each site to identify the major source regions associated with the measured values. Results suggested that sources in the Chicago/Gary, St. Louis, and Ohio River Valley urban/industrial areas had a substantial impact on Hg wet deposition, strongly supporting the conclusion that local and regional coal combustion was the largest source of Hg wet deposition in Illinois.

  13. Automated product recovery in a Hg-196 photochemical isotope separation process

    Science.gov (United States)

    Grossman, M.W.; Speer, R.

    1992-07-21

    A method of removing deposited product from a photochemical reactor used in the enrichment of [sup 196]Hg has been developed and shown to be effective for rapid re-cycling of the reactor system. Unlike previous methods relatively low temperatures are used in a gas and vapor phase process of removal. Importantly, the recovery process is understood in a quantitative manner so that scaling design to larger capacity systems can be easily carried out. 2 figs.

  14. [Monitoring nitrogen deposition on temperate grassland in Inner Mongolia].

    Science.gov (United States)

    Zhang, Ju; Kang, Rong-hua; Zhao, Bin; Huang, Yong-mei; Ye, Zhi-xiang; Duan, Lei

    2013-09-01

    Nitrogen deposition on temperate steppe was monitored from November 2011 to October 2012 in Taipusi County, Inner Mongolia. The dry deposition of gaseous nitrogen compounds was calculated based on online-monitored atmospheric concentrations of NH3 and NO2 and dry deposition velocity simulated by CMAQ model. The wet deposition, dry deposition of particle, and throughfall deposition were also estimated by collecting rainfall, dust fall, and throughfall samples and the chemical analysis of NH4+ and NO3-concentrations. Results showed that the total deposition of nitrogen was up to 3.43 g x (m2 x a)(-1), which might be harmful to the ecosystem. The wet deposition accounted for about 44% of the total deposition, while dry deposition of gases and particle accounted for 38% and 18%, respectively. Since the deposition contributed more than wet deposition, a great attention should be paid on dry deposition monitoring. However, the very simple method for total deposition monitoring based on throughfall seemed not suitable for grassland because the monitored throughfall deposition was much lower than the total deposition. In addition, reduced nitrogen (NH4+ and NH3) contributed to 71% of the total deposition, while oxidation nitrogen (NO3- and NO2) was only 29%. Therefore, NH3 emission reduction should be considered as important as nitrogen oxides (NO3x) for controlling nitrogen deposition.

  15. Process of [sup 196]Hg enrichment

    Science.gov (United States)

    Grossman, M.W.; Mellor, C.E.

    1993-04-27

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of [sup 196]Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  16. Process of .sup.196 Hg enrichment

    Science.gov (United States)

    Grossman, Mark W.; Mellor, Charles E.

    1993-01-01

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of .sup.196 Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  17. Magnetic fields of HgMn stars

    DEFF Research Database (Denmark)

    Hubrig, S.; González, J. F.; Ilyin, I.

    2012-01-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have...... failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims. We re-analyse the available spectropolarimetric material...

  18. Study of Energy Consumption of Potato Slices During Drying Process

    Directory of Open Access Journals (Sweden)

    Hafezi Negar

    2015-06-01

    Full Text Available One of the new methods of food drying using infrared heating under vacuum is to increase the drying rate and maintain the quality of dried product. In this study, potato slices were dried using vacuum-infrared drying. Experiments were performed with the infrared lamp power levels 100, 150 and 200 W, absolute pressure levels 20, 80, 140 and 760 mmHg, and with three thicknesses of slices 1, 2 and 3 mm, in three repetitions. The results showed that the infrared lamp power, absolute pressure and slice thickness have important effects on the drying of potato. With increasing the radiation power, reducing the absolute pressure (acts of vacuum in the dryer chamber and also reducing the thickness of potato slices, drying time and the amount of energy consumed is reduced. In relation to thermal utilization efficiency, results indicated that with increasing the infrared radiation power and decreasing the absolute pressure, thermal efficiency increased.

  19. Of Variability, or its Absence, in HgMn Stars

    CERN Document Server

    Turcotte, S

    2003-01-01

    Current models and observations of variability in HgMn stars disagree. We present here the models that argue for pulsating HgMn stars with properties similar to those of Slowly Pulsating B Stars. The lack of observed variable HgMn stars suggests that some physical process is missing from the models. Some possibilities are discussed.

  20. Atmospheric wet and litterfall mercury deposition at urban and rural sites in China

    Science.gov (United States)

    Fu, Xuewu; Yang, Xu; Lang, Xiaofang; Zhou, Jun; Zhang, Hui; Yu, Ben; Yan, Haiyu; Lin, Che-Jen; Feng, Xinbin

    2016-09-01

    Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 and 12.6 ± 6.5 µg m-2 yr-1, respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m-2 yr-1, higher than the wet deposition fluxes by a factor of 3.9 to 8.7 and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric Hg in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that wash out a smaller amount of GOM and PBM during precipitation events.

  1. Hg contents in soils and olive-tree (Olea Europea, L.) leaves from an area affected by elemental mercury pollution (Jódar, SE Spain).

    Science.gov (United States)

    López-Berdonces, Miguel Angel; María Esbrí, José; Amorós, José Angel; Lorenzo, Saturnino; Fernández-Calderón, Sergio; Higueras, Pablo; Perez-de-los-Reyes, Caridad

    2014-05-01

    Data from soil and olive tree leaves around a decommissioned chlor-alkali plant are presented in this communication. The factory was active in the period 1977-1991, producing during these years a heavily pollution of Guadalquivir River and hydrargyrism in more than local 45 workers. It is located at 7 km South of Jódar, a locality with some 12,120 inhabitants. Mercury usage was general in this type of plants, but at present it is being replaced by other types of technologies, due to the risks of mercury usage in personal and environment. A soil geochemistry survey was carried out in the area, along with the analysis of olive-tree leaves (in the plots with this culture) from the same area. 73 soil samples were taken at two different depths (0-15 cm and 15-30 cm), together with 41 olive tree samples. Mercury content of geologic and biologic samples was determined by means of Atomic Absorption Spectrometry with Zeeman Effect, using a Lumex RA-915+ device with the RP-91C pyrolysis attachment. Air surveys were carried our using a RA-915M Lumex portable analytical device. Soil mercury contents were higher in topsoil than in the deeper soil samples, indicating that incorporation of mercury was due to dry and wet deposition of mercury vapors emitted from the plant. Average content in topsoil is 564.5 ng g-1. Hg contents in olive-tree leaves were in the range 46 - 453 ng g-1, with an average of 160.6 ng g-1. This level is slightly lower than tolerable level for agronomic crops established by Kabata-Pendias (2001) in 200 ng g-1. We have also compared soil and leaf contents for each sampling site, finding a positive and significant correlation (R=0.49), indicating that Hg contents in the leaves are linked to Hg contents in the soils. BAC (Bioaccumulation Absorption Coefficient, calculated as ratio between soil and leaf concentration) is 0.28 (consistent with world references, BAC = 0.7), considered "medium" in comparison with other mineral elements. Main conclusions of this

  2. HgZnTe-based detectors for LWIR NASA applications

    Science.gov (United States)

    Patten, Elizabeth A.; Kalisher, Murray H.

    1990-01-01

    The initial goal was to grow and characterize HgZnTe and determine if it indeed had the advantageous properties that were predicted. Researchers grew both bulk and liquid phase epitaxial HgZnTe. It was determined that HgZnTe had the following properties: (1) microhardness at least 50 percent greater than HgCdTe of equivalent bandgap; (2) Hg annealing rates of at least 2 to 4 times longer than HgCdTe; and (3) higher Hg vacancy formation energies. This early work did not focus on one specific composition (x-value) of HgZnTe since NASA was interested in HgZnTe's potential for a variety of applications. Since the beginning of 1989, researchers have been concentrating, however, on the liquid phase growth of very long wavelength infrared (VLWIR) HgZnTe (cutoff approx. equals 17 microns at 65K) to address the requirements of the Earth Observing System (EOS). Since there are no device models to predict the advantages in reliability one can gain with increased microhardness, surface stability, etc., one must fabricate HgZnTe detectors and assess their relative bake stability (accelerated life test behavior) compared with HgCdTe devices fabricated in the same manner. Researchers chose to fabricate HIT detectors as a development vehicle for this program because high performance in the VLWIR has been demonstrated with HgCdTe HIT detectors and the HgCdTe HIT process should be applicable to HgZnTe. HIT detectors have a significant advantage for satellite applications since these devices dissipate much less power than conventional photoconductors to achieve the same responsivity.

  3. Fully relativistic coupled cluster and DFT study of electric field gradients at Hg in 199Hg compounds

    DEFF Research Database (Denmark)

    Arcisauskaité, Vaida; Knecht, Stefan; Sauer, Stephan P. A.

    2012-01-01

    We investigate the magnitude and interplay of relativistic and electron correlation effects on the electric field gradient (EFG) at the position of Hg in linear and bent HgL2 (L=CH3, Cl, Br, I) and trigonal planar [HgCl3]- complexes using four-component relativistic Dirac-Coulomb (DC) and non...

  4. The Chevrel phase HgMo6S8

    Directory of Open Access Journals (Sweden)

    Michel Potel

    2009-05-01

    Full Text Available The crystal structure of HgMo6S8, mercury(II hexamolybdenum octasulfide, is based on (Mo6S8S6 cluster units (overline{3} symmetry interconnected through interunit Mo—S bonds. The Hg2+ cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic overline{3} and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg0.973 (3Mo6S8.

  5. Assessing the emission sources of atmospheric mercury in wet deposition across Illinois.

    Science.gov (United States)

    Gratz, Lynne E; Keeler, Gerald J; Morishita, Masako; Barres, James A; Dvonch, J Timothy

    2013-03-15

    From August 4, 2007 to August 31, 2009, we collected event-based precipitation samples for mercury (Hg) and trace element analyses at four sites in Illinois (IL), USA. The objectives of these measurements were to quantify Hg wet deposition across the state, and to assess the contributions to Hg in precipitation from major local and regional emission sources. Monitoring sites were located, from north to south, in Chicago, Peoria, Nilwood, and Carbondale, IL. Measurements from these four sites demonstrated that a clear spatial gradient in Hg wet deposition was not evident across the state. Each site received>10μgm(-2) of Hg wet deposition annually, and these observed values were comparable to annual Hg wet deposition measurements from other event-based precipitation monitoring sites in source-impacted areas of the Midwestern U.S. We applied the multivariate statistical receptor model, Positive Matrix Factorization (EPA PMF v3.0), to the measured Hg and trace element wet deposition amounts at the four sites. Results suggested that 50% to 74% of total Hg wet deposition at each site could be attributed to coal combustion emissions. The other source signatures identified in the precipitation compositions included cement manufacturing, mixed metal smelting/waste incineration, iron-steel production, and a phosphorus source. We also applied a hybrid receptor model, Quantitative Transport Bias Analysis (QTBA), to the Hg wet deposition datasets to identify the major source regions associated with the measured values. The calculated QTBA probability fields suggested that transport from urban/industrial areas, such as Chicago/Gary, St. Louis, and the Ohio River Valley, resulted in some of the highest estimated event-based Hg wet deposition amounts at the four sites (potential mass transfer of up to 0.32μgm(-2)). The combined application of PMF and QTBA supported the hypothesis that local and regional coal combustion was the largest source of Hg wet deposition in Illinois.

  6. Controlling Factors of Long-Term Trends in Mercury Wet Deposition and Precipitation Concentrations at Huntington Wildlife Forest

    Science.gov (United States)

    Ye, Z.; Mao, H.; Driscoll, C. T.

    2015-12-01

    Observations from the Mercury Deposition Network (MDN) at Huntington Wildlife Forest (HWF) suggested that a significant decline (r2 = 0.34, p = 0.03) from 2000 to 2013 in volume weighted mean (VWM) Hg concentrations in precipitation was linked to Hg emission decreases in the United States, especially in the Northeast and Midwest, and yet Hg wet deposition has remained fairly constant over the past two decades. The present study aimed to investigate the climatic, terrestrial, and anthropogenic factors that influenced the decadal pattern in Hg wet deposition in upstate NY. In spring and summer, when Hg wet deposition was the strongest, significant positive correlation (r2 = 0.89, p < 0.0001 in spring; r2 = 0.58, p = 0.002 in summer) of Hg wet deposition with precipitation was found. Increases in precipitation during these seasons could offset the decreasing of Hg concentration in precipitation. Besides, springtime positive correlation (r2 = 0.35, p = 0.02) between precipitation and the North Atlantic Oscillation (NAO) index together with geopotential height and wind speed analysis indicated that large-scale dynamical forcing was likely an important factor influencing the long term trend in springtime Hg wet deposition at HWF. To further quantify the roles of meteorological and anthropogenic factors in Hg wet deposition, the Community Multiscale Air Quality (CMAQ) model was employed using an algorithm depicting state-of-the-art Hg chemistry mechanism and up-to-date Hg emission inventories evaluated with MDN and Atmospheric Mercury Network (AMNet) measurement data. CMAQ simulations with a constant vs. realistic meteorological conditions for multiple warm seasons (including spring and summer) were used to characterize and quantify the impacts of inter-annual variability of precipitation and atmospheric circulation on Hg wet deposition. In addition, contributions to Hg wet deposition from decreases in anthropogenic emissions in NYS and nation-wide were quantified from

  7. Superdeformation studies in {sup 191}Hg

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, M.P.; Janssens, R.V.F.; Crowell, B. [and others

    1995-08-01

    Superdeformation in the A {approximately} 190 region was first observed in {sup 191}Hg from an experiment performed at ATLAS using the Argonne Notre Dame {gamma}-ray facility. We recently revisited the study of superdeformation in this nucleus using Gammasphere and the {sup 160}Gd({sup 36}S,5n) and {sup 174}Yb({sup 22}Ne,5n) reactions at 172 and 120 MeV in order to populate and measure states in the second well. The goal of the experiment was to identify new bands in the data, and thus allow us to gain understanding on the relative placement of single particle orbitals near the N = 112 SD shell gap. From an analysis of the data, the three previously identified SD bands were extended, and their feeding into the yrast states delineated. Two new SD bands were observed and preliminary evidence for a third new band was obtained as well.

  8. First survey of atmospheric heavy metal deposition in Kosovo using moss biomonitoring.

    Science.gov (United States)

    Maxhuni, Albert; Lazo, Pranvera; Kane, Sonila; Qarri, Flora; Marku, Elda; Harmens, Harry

    2016-01-01

    Bryophytes act as bioindicators and bioaccumulators of metal deposition in the environment. The atmospheric deposition of Cd, Cr, Cu, Fe, Hg, Ni, Mn, Pb, and Zn in Kosovo was investigated by using carpet-forming moss species (Pseudocleropodium purum and Hypnum cupressiforme) as bioindicators. This research is part of the European moss survey coordinated by the ICP Vegetation, an International Cooperative Programme reporting on the effects of air pollution on vegetation to the UNECE Convention on Long-range Transboundary Air Pollution. Sampling was performed during the summer of 2011 at 25 sampling sites homogenously distributed over Kosovo. Unwashed, dried samples were digested by using wet digestion in Teflon tubes. The concentrations of metal elements were determined by atomic absorption spectrometry (AAS) equipped with flame and/or furnace systems. The heavy metal concentration in mosses reflected local emission sources. The data obtained in this study were compared with those of similar studies in neighboring countries and Europe (2010-2014 survey). The geographical distribution maps of the elements over the sampled territory were constructed using geographic information system (GIS) technology. The concentrations of Cr, Ni, Pb, and Zn were higher than the respective median values of Europe, suggesting that the zones with heavy vehicular traffic and industry emission input are important emitters of these elements. Selected zones are highly polluted particularly by Cd, Pb, Hg, and Ni. The statistical analyses revealed that a strong correlation exists between the Pb and Cd content in mosses, and the degree of pollution in the studied sites was assessed.

  9. Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico).

    Science.gov (United States)

    Ruelas-Inzunza, J; Green-Ruiz, C; Zavala-Nevárez, M; Soto-Jiménez, M

    2011-08-15

    With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06 μg g ⁻¹ dry weight) and Cr (0.01 μg g⁻¹) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56 μg g⁻¹) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65 μg g⁻¹) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05 μg g⁻¹) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09 μg g⁻¹) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20 μg g⁻¹) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4 μg g⁻¹) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (pseason. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34 kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68 kg of prawns relative to levels of Cd, Hg and Pb, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Effects of mercury deposition and coniferous forests on the mercury contamination of fish in the South Central United States.

    Science.gov (United States)

    Drenner, Ray W; Chumchal, Matthew M; Jones, Christina M; Lehmann, Christopher M B; Gay, David A; Donato, David I

    2013-02-05

    Mercury (Hg) is a toxic metal that is found in aquatic food webs and is hazardous to human and wildlife health. We examined the relationship between Hg deposition, land coverage by coniferous and deciduous forests, and average Hg concentrations in largemouth bass (Micropterus salmoides)-equivalent fish (LMBE) in 14 ecoregions located within all or part of six states in the South Central U.S. In 11 ecoregions, the average Hg concentrations in 35.6-cm total length LMBE were above 300 ng/g, the threshold concentration of Hg recommended by the U.S. Environmental Protection Agency for the issuance of fish consumption advisories. Percent land coverage by coniferous forests within ecoregions had a significant linear relationship with average Hg concentrations in LMBE while percent land coverage by deciduous forests did not. Eighty percent of the variance in average Hg concentrations in LMBE between ecoregions could be accounted for by estimated Hg deposition after adjusting for the effects of coniferous forests. Here we show for the first time that fish from ecoregions with high atmospheric Hg pollution and coniferous forest coverage pose a significant hazard to human health. Our study suggests that models that use Hg deposition to predict Hg concentrations in fish could be improved by including the effects of coniferous forests on Hg deposition.

  11. Can graphene make better HgCdTe infrared detectors?

    Directory of Open Access Journals (Sweden)

    Shi Yanli

    2011-01-01

    Full Text Available Abstract We develop a simple and low-cost technique based on chemical vapor deposition from which large-size graphene films with 5-10 graphene layers can be produced reliably and the graphene films can be transferred easily onto HgCdTe (MCT thin wafers at room temperature. The proposed technique does not cause any thermal and mechanical damages to the MCT wafers. It is found that the averaged light transmittance of the graphene film on MCT thin wafer is about 80% in the mid-infrared bandwidth at room temperature and 77 K. Moreover, we find that the electrical conductance of the graphene film on the MCT substrate is about 25 times larger than that of the MCT substrate at room temperature and 77 K. These experimental findings suggest that, from a physics point of view, graphene can be utilized as transparent electrodes as a replacement for metal electrodes while producing better and cheaper MCT infrared detectors.

  12. Relationship Between Soil Properties and Different Fractions of Soil Hg

    Institute of Scientific and Technical Information of China (English)

    WUHONGTAO; YUGUIFEN; 等

    2001-01-01

    Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing,China,Results showed that clay(<2m) could increase water-soluble Hg(r=0.700*).Soil organic matter (OM) could enhance the increase of elemental Hg(r=0.674*),The higher the base saturation percentage (BSP) ,the more the residual Hg(R=0.684*) .Organic Hg,the sum of said-soluble organic He and alkali-soluble Hg,was positively affected by silt(2-20μm)but negatively affected by pH,with the direct path coefficients amounting to 1.0487 and 0.5121,respectively .The positive effect of OM and negative effect of BSP on organic Hg were the most significant ,with the direct path coefficients being 0.7614 and -0.8527,respectively. The indirect effect of clay(<2μm) iva BSP (path coefficient=0.4186) was the highest,showing that the real influencing factor in the effect of clay(<2μm) via BSP (path coefficient=0.4186) was the highest,showing that the real influencing factor in the effect of clay(<2μm) on acid-soluble organic Hw was BSP.since the available Hg fraction,water-soluble Hg,was positively affected by soil clay content,and the quite immobile and not bioavailable residual Hg by soil BSP,suitable reduction of clay content and increase of BSP would be of much help to reduce the Hg availability and Hg activity in Hg-contaminated soils.

  13. Short-term post-wildfire dry-ravel processes in a chaparral fluvial system

    Science.gov (United States)

    Florsheim, Joan L.; Chin, Anne; O'Hirok, Linda S.; Storesund, Rune

    2016-01-01

    Dry ravel, the transport of sediment by gravity, transfers material from steep hillslopes to valley bottoms during dry conditions. Following wildfire, dry ravel greatly increases in the absence of vegetation on hillslopes, thereby contributing to sediment supply at the landscape scale. Dry ravel has been documented as a dominant hillslope erosion mechanism following wildfire in chaparral environments in southern California. However, alteration after initial deposition is not well understood, making prediction of post-fire flood hazards challenging. The majority of Big Sycamore Canyon burned during the May 2013 Springs Fire leaving ash and a charred layer that covered hillslopes and ephemeral channels. Dry-ravel processes following the fire produced numerous deposits in the hillslope-channel transition zone. Field data focus on: 1) deposition from an initial post-wildfire dry-ravel pulse; and 2) subsequent alteration of dry ravel deposits over a seven-month period between September 2013 and April 2014. We quantify geomorphic responses in dry ravel deposits including responses during the one small winter storm that generated runoff following the fire. Field measurements document volumetric changes after initial post-wildfire deposition of sediment derived from dry ravel. Erosion and deposition mechanisms that occurred within dry-ravel deposits situated in the hillslope-channel transition zone included: 1) mobilization and transport of a portion or the entire deposit by fluvial erosion; 2) rilling on the surface of the unconsolidated deposits; 3) deposition on deposits via continued hillslope sediment supply; and 4) mass wasting that transfers sediment within deposits where surface profiles are near the angle of repose. Terrestrial LiDAR scanning point clouds were analyzed to generate profiles quantifying depth of sediment erosion or deposition over remaining dry ravel deposits after the first storm season. This study contributes to the understanding of potential

  14. Comparative assessment of Azolla pinnata and Vallisneria spiralis in Hg removal from G.B. Pant Sagar of Singrauli Industrial region, India.

    Science.gov (United States)

    Rai, Prabhat Kumar; Tripathi, B D

    2009-01-01

    The aim of the present work was to monitor the Hg pollution in water and sediments of G.B. Pant Sagar located in Singrauli Industrial Region, India and to suggest the efficient aquatic plants for its phytoremediation. The study assessed the comparative potential of a free floating water fern Azolla pinnata and submerged aquatic macrophyte Vallisneria spiralis to purify waters polluted by Hg. Six days laboratory experiments have been conducted to mark the percentage removal of Hg at initial concentration of 0.1, 0.5, 1.0 and 3.0 mg L(-1). The percentage removal of Hg was higher for A. pinnata (80-94%) than V. spiralis (70-84%). Likewise, the Hg accumulated in dry mass was much higher for A. pinnata and a high correlation (R(2) = 0.91 for A. pinnata and 0.99 for V. spiralis) was obtained between applied Hg doses and accumulated amounts in biomass. A concentration dependent decrease in chlorophyll a, protein, RNA, DNA and nutrients (NO(3-) and PO(4)(3-)) uptake was detected in A. pinnata and V. spiralis due to Hg toxicity. The decrease was more prominent in Azolla than Vallisneria. The results recommended the use of A. pinnata and V. spiralis to ameliorate the industrial effluents (thermal power, chlor-alkali and coal mine effluent) contaminated with Hg.

  15. Hg and As Minerals in Fluid Inclusions from the Williams Mine,Hemlo,and Their Genetic Implications

    Institute of Scientific and Technical Information of China (English)

    卢焕章; ANDDON.C.HARRIS

    2002-01-01

    The Hemlo mineralization is enigmatic compared to general Archean lode gold deposits based on the fact that is characterized by an exotic mineralogy containing elements such as As,Hg,Sb,Ba,V and Mo.The genetic concepts range from syngenetc to epigenetic types of mineralization.This reconnaissance study was designed to examine the relationshp of Hg-As minerals with respect of fluid inclusions in the Williams mine(formerly known as the Page Williams mine)covering the A and C ore zones.

  16. Hirabayashi, Satoshi; Kroll, Charles N.; Nowak, David J. 2011. Component-based development and sensitivity analyses of an air pollutant dry deposition model. Environmental Modelling & Software. 26(6): 804-816.

    Science.gov (United States)

    Satoshi Hirabayashi; Chuck Kroll; David Nowak

    2011-01-01

    The Urban Forest Effects-Deposition model (UFORE-D) was developed with a component-based modeling approach. Functions of the model were separated into components that are responsible for user interface, data input/output, and core model functions. Taking advantage of the component-based approach, three UFORE-D applications were developed: a base application to estimate...

  17. Oxidative stress in MeHg-induced neurotoxicity

    Energy Technology Data Exchange (ETDEWEB)

    Farina, Marcelo, E-mail: farina@ccb.ufsc.br [Departamento de Bioquimica, Centro de Ciencias Biologicas, Universidade Federal de Santa Catarina, Florianopolis, SC (Brazil); Aschner, Michael [Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (United States); Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN (United States); Rocha, Joao B.T., E-mail: jbtrocha@yahoo.com.br [Departamento de Quimica, Centro de Ciencias Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, RS (Brazil)

    2011-11-15

    Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have been reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically

  18. Modeling interactions of Hg(II) and bauxitic soils.

    Science.gov (United States)

    Weerasooriya, Rohan; Tobschall, Heinz J; Bandara, Atula

    2007-11-01

    The adsorptive interactions of Hg(II) with gibbsite-rich soils (hereafter SOIL-g) were modeled by 1-pK surface complexation theory using charge distribution multi-site ion competition model (CD MUSIC) incorporating basic Stern layer model (BSM) to account for electrostatic effects. The model calibrations were performed for the experimental data of synthetic gibbsite-Hg(II) adsorption. When [NaNO(3)] > or = 0.01M, the Hg(II) adsorption density values, of gibbsite, Gamma(Hg(II)), showed a negligible variation with ionic strength. However, Gamma(Hg(II)) values show a marked variation with the [Cl(-)]. When [Cl(-)] > or = 0.01M, the Gamma(Hg(II)) values showed a significant reduction with the pH. The Hg(II) adsorption behavior in NaNO(3) was modeled assuming homogeneous solid surface. The introduction of high affinity sites, i.e., >Al(s)OH at a low concentration (typically about 0.045 sites nm(-2)) is required to model Hg(II) adsorption in NaCl. According to IR spectroscopic data, the bauxitic soil (SOIL-g) is characterized by gibbsite and bayerite. These mineral phases were not treated discretely in modeling of Hg(II) and soil interactions. The CD MUSIC/BSM model combination can be used to model Hg(II) adsorption on bauxitic soil. The role of organic matter seems to play a role on Hg(II) binding when pH>8. The Hg(II) adsorption in the presence of excess Cl(-) ions required the selection of high affinity sites in modeling.

  19. Lithography process for patterning HgI2 photonic devices

    Science.gov (United States)

    Mescher, Mark J.; James, Ralph B.; Hermon, Haim

    2004-11-23

    A photolithographic process forms patterns on HgI.sub.2 surfaces and defines metal sublimation masks and electrodes to substantially improve device performance by increasing the realizable design space. Techniques for smoothing HgI.sub.2 surfaces and for producing trenches in HgI.sub.2 are provided. A sublimation process is described which produces etched-trench devices with enhanced electron-transport-only behavior.

  20. Epitaxial growth of HgTe by a MOVPE process

    Energy Technology Data Exchange (ETDEWEB)

    Irvine, S.J.C.; Mullin, J.B.; Royle, A. (Royal Signals and Radar Establishment, Malvern (UK))

    1982-03-01

    Epitaxial layers of HgTe have been grown onto insulating CdTe substrates by the pyrolysis of (C/sub 2/H/sub 5/)/sub 2/Te in the presence of Hg vapour using a H/sub 2/ flow system. Temperature-dependent Hall effect and conductivity measurements have shown that the electrical properties of the layers are comparable with good quality bulk HgTe.

  1. Possibilities of mercury removal in the dry flue gas cleaning lines of solid waste incineration units.

    Science.gov (United States)

    Svoboda, Karel; Hartman, Miloslav; Šyc, Michal; Pohořelý, Michael; Kameníková, Petra; Jeremiáš, Michal; Durda, Tomáš

    2016-01-15

    Dry methods of the flue gas cleaning (for HCl and SO2 removal) are useful particularly in smaller solid waste incineration units. The amount and forms of mercury emissions depend on waste (fuel) composition, content of mercury and chlorine and on the entire process of the flue gas cleaning. In the case of high HCl/total Hg molar ratio in the flue gas, the majority (usually 70-90%) of mercury is present in the form of HgCl2 and a smaller amount in the form of mercury vapors at higher temperatures. Removal of both main forms of mercury from the flue gas is dependent on chemical reactions and sorption processes at the temperatures below approx. 340 °C. Significant part of HgCl2 and a small part of elemental Hg vapors can be adsorbed on fly ash and solid particle in the air pollution control (APC) processes, which are removed in dust filters. Injection of non-impregnated active carbon (AC) or activated lignite coke particles is able to remove mainly the oxidized Hg(2+) compounds. Vapors of metallic Hg(o) are adsorbed relatively weakly. Much better chemisorption of Hg(o) together with higher sorbent capacity is achieved by AC-based sorbents impregnated with sulfur, alkali poly-sulfides, ferric chloride, etc. Inorganic sorbents with the same or similar chemical impregnation are also applicable for deeper Hg(o) removal (over 85%). SCR catalysts convert part of Hg(o) into oxidized compounds (HgO, HgCl2, etc.) contributing to more efficient Hg removal, but excess of NH3 has a negative effect. Both forms, elemental Hg(o) and HgCl2, can be converted into HgS particles by reacting with droplets/aerosol of poly-sulfides solutions/solids in flue gas. Mercury captured in the form of water insoluble HgS is more advantageous in the disposal of solid waste from APC processes. Four selected options of the dry flue gas cleaning with mercury removal are analyzed, assessed and compared (in terms of efficiency of Hg-emission reduction and costs) with wet methods and retrofits for more

  2. Experiments with a New 201Hg+ Ion Clock

    Science.gov (United States)

    Burt, E. A.; Taghavi-Larigani, S.; Lea, S. N.; Prestage, J. D.; Tjoelker, R. L.

    2009-04-01

    In this paper we describe a new clock based on 201Hg+. All previous mercury ion clocks have been based on 199Hg+. We have recently completed construction of the 201Hg+ clock and will describe modifications to the design of our existing 199Hg+ clocks to accommodate the new isotope. We will also describe initial spectroscopic measurements of the hyperfine manifold, and possible future experiments. One experiment could place a limit on variations in the strong interaction fundamental constant ratio mq/ΛQCD.REFID="9789812838223_0043FN001">

  3. PENCEMARAN LOGAM BERAT MERKURI (Hg PADA AIRTANAH

    Directory of Open Access Journals (Sweden)

    Thomas Triadi Putranto

    2012-02-01

    Full Text Available The earth consists largely of water because the land area is smaller than the ocean. Human beings on this earthcan not escape the need for water. Water is the main requirement for the process of life on the earth.Relatively clean water that is coveted by men, whether for purposes of daily life, for industrial purposes, for thecleanliness of city sanitation, as well as for agricultural purposes and so forth. Heavy metal pollution is a veryserious issue to be handled, because of adverse environmental and ecosystem in general. Heavy metallic elementis the element which has a density of more than 5 gr/cm3. Hg has a density of 13.55 gr/cm3. Disaster is anoutbreak of Minamata mercury poisoning in people who eat fish contaminated by mercury in Minamata Japan,and this event is known as Minamata Disease. Efforts to tackle the heavy metal pollution can actually be doneusing a chemical process or by microorganism such as microbes and bacteria.

  4. Hg-coordination studies of oligopeptides containing cysteine, histidine and tyrosine by $^{199m}$Hg-TDPAC

    CERN Document Server

    Ctortecka, B; Mallion, S; Butz, T; Hoffmann, R

    1999-01-01

    In order to study the interaction of histidine- and tyrosine- containing peptide chains with Hg(II), the nuclear quadrupole interaction (NQI) of /sup 199m/Hg in the Hg complexes of the oligopeptides alanyl-alanyl-histidyl-alanyl-alanine-amid (AAHAA-NH /sub 2/) and alanyl-alanyl-tyrosyl-alanyl-alanine-amid (AAYAA-NH/sub 2/) was determined by time differential perturbed angular correlation and is compared with previous data on alanyl-alanyl-cysteyl-alanyl- alanyl (AACAA-OH). The /sup 199m/Hg-NQIs depend on the oligopeptide to Hg(II) stoichiometry and indicate that two-fold and four-fold coordinations occur for the bound Hg(II). (12 refs).

  5. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>20070291 Gong Ping (Northern Fujian Geological Party, Shaozou 354000) Discussion on Geological Characteristics and Control Factors of the Shimen Au-polymetallic Deposit in Zhenghe County, Fujian Province (Geology of Fujian, ISSN1001-3970, CN38-1080/P, 25(1), 2006, p.18-24, 2 illus., 2 tables, 1 ref.) Key words: gold deposits, polymetallic deposits, Fujian Province

  6. Contribution of Atmospheric Nitrogen Compounds to N Deposition in a Broadleaf Forest of Southern China

    Institute of Scientific and Technical Information of China (English)

    HU Zheng-Yi; XU Cheng-Kai; ZHOU Li-Na; SUN Ben-Hua; HE Yuan-Qiu; ZHOU Jing; CAO Zhi-Hong

    2007-01-01

    A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH3, NH4-N, NO3-N, and NO2) and contribution of three sources (gas, rainwater, and particles) to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha-1, with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds (NH+4 and NH3) were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.

  7. ROE Total Nitrogen Deposition 1989-1991

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset identifies the amount of wet, dry, and total deposition of nitrogen in kilograms per hectare from 1989 to 1991 at a set of point locations across the...

  8. ROE Total Sulfur Deposition 1989-1991

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset identifies the amount of wet, dry, and total deposition of sulfur in kilograms per hectare from 1989 to 1991 at a set of point locations across the...

  9. ROE Total Nitrogen Deposition 2011-2013

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset identifies the amount of wet, dry, and total deposition of nitrogen in kilograms per hectare from 2011 to 2013 at a set of point locations across the...

  10. ROE Total Sulfur Deposition 2011-2013

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset identifies the amount of wet, dry, and total deposition of sulfur in kilograms per hectare from 2011 to 2013 at a set of point locations across the...

  11. Characterization of soil fauna under the influence of mercury atmospheric deposition in Atlantic Forest, Rio de Janeiro, Brazil.

    Science.gov (United States)

    Buch, Andressa Cristhy; Correia, Maria Elizabeth Fernandes; Teixeira, Daniel Cabral; Silva-Filho, Emmanoel Vieira

    2015-06-01

    The increasing levels of mercury (Hg) found in the atmosphere arising from anthropogenic sources, have been the object of great concern in the past two decades in industrialized countries. Brazil is the seventh country with the highest rate of mercury in the atmosphere. The major input of Hg to ecosystems is through atmospheric deposition (wet and dry), being transported in the atmosphere over large distances. The forest biomes are of strong importance in the atmosphere/soil cycling of elemental Hg through foliar uptake and subsequent transference to the soil through litter, playing an important role as sink of this element. Soil microarthropods are keys to understanding the soil ecosystem, and for such purpose were characterized by the soil fauna of two Units of Forest Conservation of the state of the Rio de Janeiro, inwhich one of the areas suffer quite interference from petrochemicals and industrial anthropogenic activities and other area almost exempts of these perturbations. The results showed that soil and litter of the Atlantic Forest in Brazil tend to stock high mercury concentrations, which could affect the abundance and richness of soil fauna, endangering its biodiversity and thereby the functioning of ecosystems. Copyright © 2015. Published by Elsevier B.V.

  12. Effect of salinity and temperature on the adsorption of Hg(II) from aqueous solutions by a Ca-montmorillonite.

    Science.gov (United States)

    Green-Ruiz, C

    2009-01-01

    Use of clay minerals for removing mercury is an effective technology for the treatment of industrial wastewaters and can become an effective tool for the remediation of coastal ecosystems polluted with this metal. Calcic montmorillonite was employed for adsorbing Hg(II) ions from aqueous solutions at different conditions of salinity (0, 20 and 35 g NaCl L(-1)), temperature (15, 25 and 35 degrees C), and initial concentrations (0.25, 0.50, 1.00, 2.50, 5.00 and 10.00 mg Hg L(-1)). It was observed that 0.4 g dry weight of montmorillonite removed from 0.02 mg g(-1) (at 0.25 mg L(-1) of Hg(II)) to 0.68 mg g(-1) (at 10.0 mg L(-1) of Hg(II)) at 25 degrees C, salinity of 0 g NaCl L(-1) and pH of 6. The initial concentration of Hg(II) and salinity had an effect on the behaviour of the adsorption process, which was temperature independent. The data fit well the Freundlich adsorption isotherm, indicating that heterogeneous conditions prevail in this process.

  13. Comparison of total Hg results in sediment samples from Rio Grande reservoir determine by NAA and CV AAS

    Energy Technology Data Exchange (ETDEWEB)

    Franklin, Robson L., E-mail: robsonf@cetesbnet.sp.gov.br [Centro Tecnologico de Saneamento Basico (ELAI/CETESB), SP, Sao Paulo (Brazil). Laboratorio de Quimica Inorganica; Bevilacqua, Jose Eduardo [Centro Tecnologico de Saneamento Basico (CETESB), SP, Sao Paulo (Brazil). UNIFIEO - Centro Universitario FIEO; Favaro, Deborah I.T., E-mail: defavaro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Laboratorio de Analise por Ativacao Neutronica (LAN/CRPq)

    2011-07-01

    The Rio Grande reservoir is located in the Metropolitan area of Sao Paulo and it is used for recreation purposes and as source water for drinking water production. During the last decades has been detected mercury contamination in the sediments of this reservoir, mainly in the eastern part, near the main affluent of the reservoir, in the Rio Grande da Serra and Ribeirao Pires counties. In the present study bottom sediment samples were collected in four different sites into four sampling campaigns during the period of September 2008 to January 2010. The samples were dried at room temperature, ground and passed through a 2 mm sieve. Total Hg determination in the sediment samples was carried out by two different analytical techniques: neutron activation analysis (NAA) and cold vapor atomic absorption spectrometry (CV AAS). The methodology validation, in terms of precision and accuracy, was performed by reference materials, and presented a recovery of 83 to 108%. The total Hg results obtained by both analytical techniques ranged from 3 to 71 mg kg-1 and were considered similar by statistical analysis, even though NAA technique furnishes the total concentration while CV AAS using the 3015 digestion procedure characterizes only the bioavailable Hg. These results confirm that both analytical techniques were suitable to detect the Hg concentration levels in the Rio Grande sediments studied. The Hg levels in the sediment of the Rio Grande reservoir confirm the anthropogenic origin for this element in this ecosystem. (author)

  14. Isotope geochemistry of mercury in source rocks, mineral deposits and spring deposits of the California Coast Ranges, USA

    Science.gov (United States)

    Smith, Christopher N.; Kesler, Stephen E.; Blum, Joel D.; Rytuba, James J.

    2008-05-01

    We present here the first study of the isotopic composition of mercury in rocks, ore deposits, and active spring deposits from the California Coast Ranges, a part of Earth's crust with unusually extensive evidence of mercury mobility and enrichment. The Franciscan Complex and Great Valley Sequence, which form the bedrock in the California Coast Ranges, are intruded and overlain by Tertiary volcanic rocks including the Clear Lake Volcanic Sequence. These rocks contain two types of mercury deposits, hot-spring deposits that form at shallow depths (geothermal areas continue to precipitate Hg and Au and are modern analogues to the fossil hydrothermal systems preserved in the ore deposits. The Franciscan Complex and Great Valley Sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the Clear Lake Volcanic Field. Mean mercury isotopic compositions ( δ202Hg) for all three rock units are similar, although the range of values in Franciscan Complex rocks is greater than in either Great Valley or Clear Lake rocks. Hot spring and silica-carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units, although δ202Hg values for the mercury deposits have a greater variance than the country rocks. Precipitates from spring and geothermal waters in the area have similarly large variance and a mean δ202Hg value that is significantly lower than the ore deposits and rocks. These observations indicate that there is little or no isotopic fractionation (< ± 0.5‰) during release of mercury from its source rocks into hydrothermal solutions. Isotopic fractionation does appear to take place during transport and concentration of mercury in deposits, however, especially in their uppermost parts. Boiling of hydrothermal fluids, separation of a mercury-bearing CO 2 vapor or reduction and volatilization of Hg (0) in the near-surface environment are likely the

  15. Real-time control of HgCdTe growth by organometallic vapor phase epitaxy using spectroscopic ellipsometry

    Science.gov (United States)

    Murthy, Srikanteswara Dakshina; Bhat, Ishwara; Johs, Blaine; Pittal, Shakil; He, Ping

    1995-09-01

    The use of spectroscopic ellipsometry for monitoring the vapor phase epitaxial growth of mercury cadmium telluride (Hg1-xCdxTe) in real-time is demonstrated. The ellipsometer is used to perform system identification of the chemical vapor deposition reactor used for the growth of CdTe and to measure the response of the reactor to different growth conditions. The dynamic behavior of the reactor is also studied by evaluating the gas transport delay. The optical constants of Hg1-xCdxTe are determined at the growth temperature for different compositions. In-situ real-time composition control is performed during the growth of Hg1-xCdxTe. The required target compositions are attained by the ellipsometer and appropriate corrections are also made by the controller when a noise input in the form of a temperature variation is introduced.

  16. Analysis of IMP-grown Cd sub x Hg sub 1-x Te using helium ion RBS

    Energy Technology Data Exchange (ETDEWEB)

    Avery, A.J.; Diskett, D.J. (Royal Military Coll. of Science, Shrivenham, Swindon (United Kingdom)); Gough, J.S.; Young, M.L. (Royal Signals and Radar Establishment, Malvern (United Kingdom))

    1992-02-01

    Epitaxial layers of Cd{sub x}Hg{sub 1-x}Te may be grown by the IMP (interdiffused multilayer process) technique in which alternate layers of CdTe and HgTe are deposited by metalorganic vapour phase epitaxy and interdiffused at the growth temperature. The infrared optical properties of the layers are critically dependent upon the value of x which may be tailored by controlling the relative thickness of the CdTe and HgTe sublayers. This paper describes the application of helium ion RBS to the study of the completeness of interdiffusion between sublayers and the application of channelling to the study of their crystalline quality. (orig.).

  17. Phytoremediation of Hg and Cd from industrial effluents using an aquatic free floating macrophyte Azolla pinnata.

    Science.gov (United States)

    Rai, Prabhat Kumar

    2008-01-01

    The level of heavy metal pollution in Singrauli, an industrial region in India, was assessed and the phytoremediation capacity of a small water fern, Azolla pinnata R.BR (Azollaceae), was observed to purify waters polluted by two heavy metals, i.e., mercury (Hg) and cadmium (Cd) under a microcosm condition. Azolla pinnata is endemic to India and is an abundant and easy-growing free-floating water fern usually found in the rice fields, polluted ponds, and reservoirs of India. The fern was grown in 24 40-L aquariums containing Hg2+ and Cd2+ ions each in concentrations of 0.5, 1.0, and 3.0 mgL(-1) during the course of this study. The study revealed an inhibition of Azolla pinnata growth by 27.0-33.9% with the highest in the presence of Hg (II) ions at 0.5 mgL(-1) in comparison to the control After 13 days of the experiment, metal contents in the solution were decreased up to 70-94%. In the tissues of Azolla pinnata, the concentration of selected heavy metals during investigation was recorded between 310 and 740 mgKg(-1) dry mass, with the highest levelfoundfor Cd (II) treatment at 3.0 mgL(-1) containing a metal solution.

  18. Solubility of deposited airborne heavy metals

    Science.gov (United States)

    Cizmecioglu, Sibel C.; Muezzinoglu, Aysen

    2008-09-01

    Toxic effects of heavy metals in water and soil environments are important. Quantifying the heavy metal concentrations and their solubilities in dry and wet deposition samples is part of atmospheric research. Soluble fractions of the deposited air pollutants are important in food chain mechanisms as heavy metals may cause ecotoxic impacts. In this study, the solubilities of Cr, Cd, Pb, Cu, Zn, and Ni were investigated in deposition samples for total, dissolved, and suspended fractions after collection in a surrogate, water-surface sampler in Izmir, Turkey, during October 2003 to June 2004. To find overall solubility of each metal in dry and wet deposition samples, concentrations in soluble and suspended phases of aqueous solutions were analyzed separately. Ratios between total and dissolved forms and the metals in the same forms were analyzed and evaluated statistically. It was found that the deposited metal fluxes were significantly correlated in wet deposition with the highest correlation between Cd and Pb in the soluble and total forms. Comparatively smaller correlations were found between these metal fluxes in dry deposition samples. Results of this study showed the importance of metal pollution, especially ecotoxic properties of heavy metals in wet deposition far more than dry deposition.

  19. Net deposition of mercury to the Antarctic Plateau enhanced by sea salt.

    Science.gov (United States)

    Han, Yeongcheol; Huh, Youngsook; Hur, Soon Do; Hong, Sungmin; Chung, Ji Woong; Motoyama, Hideaki

    2017-04-01

    Photochemically driven mercury (Hg) exchange between the atmosphere and the Antarctic Plateau snowpack has been observed. An imbalance in bidirectional flux causes a fraction of Hg to remain in the snowpack perennially, but the factors that control the amount of Hg sequestered on the Antarctic Plateau are not fully understood. We analyzed sub-annual variations in total Hg (HgT) deposition to Dome Fuji over the period of 1986-2010 using cold vapor inductively coupled plasma mass spectrometry and compared concentrations with those of sea salt components (Na(+) and Cl(-)). HgT ranged from 0.12 to 5.19pgg(-1) (n=78) and was relatively high when the Na(+) concentrations were high in the same or underlying snow layers. A significant correlation (r=0.7) was found between the annual deposition fluxes of HgT and Na(+). Despite different origins and behavior of Hg and sea salt, the near-synchronous increases in the concentrations and correlation between the fluxes suggest that sea salt can intervene in the air-snow Hg exchange and promote the net deposition of Hg in the Antarctic Plateau.

  20. Effect of Soil texture on Photosynthetic traits and the deposition of Dry matter accumulation of peanut%土壤质地对花生光合特性及干物质积累分配的影响

    Institute of Scientific and Technical Information of China (English)

    贾立华; 王月福; 陈安余; 冯锴

    2013-01-01

    The paper explored the effect of soil texture on photosynthetic traits and detribution of dry matter accumulation of peanut,in order to explicit the suitable soil texture appropriated for high-yielding peanut cultivation.The soil texture including Sandy soil,Clay and Loam,and the experiment were implemented in box plant method.The results showed that the early period of peanut growth and development is Sandy soil>Loam>Clay and the later period is Loam>Sandy soil>Clay on Leaf area per plant,Functional leaf chlorophyll content,Net photosynthetic rate and Distribution of dry matter accumulation of peanut.Sandy soil is in favor of early period of photosynthetic matter accumulation,Loam is in favor of whole period,and Clay is not conductive to the whole period.Loam is more suitable than Clay and Sandy soil on distribution ratio of peanut organ dry matter accumulation.Loam has a higher pod yield than Sandy soil and Clay.%为了明确适合花生生长获得高产的土壤类型,采用箱栽的方法,研究了不同质地土壤(砂土、壤土、粘土)对花生光合特性及干物质积累分配的影响.结果表明,花生单株叶面积、功能叶叶绿素SPAD值、净光合速率和植株总干物质重在生育前期表现为砂土>壤土>粘土,在生育后期则表现为壤土>砂土>粘土.砂土有利于花生前期光合物质积累,壤土则在整个生育期内均有利于花生光合物质积累,而粘土则在整个生育期内均不利于花生光合物质积累.壤土花生各器官干物质分配比例较粘土和砂土合理.壤土的荚果产量显著高于砂土和粘土.

  1. Tracing anthropogenic Hg and Pb input using stable Hg and Pb isotope ratios in sediments of the central Portuguese Margin

    NARCIS (Netherlands)

    Mil-Holmens, M.; Blum, J.; Canário, J.; Caetano, M.; Costa, A.M.; Lebreiro, S.M.; Trancoso, M.; Richter, T.O.; de Stigter, H.; Johnson, M.; Branco, V.; Cesário, R.; Mouro, F.; Mateus, M.; Boer, W.; Melo, Z.

    2013-01-01

    Three short marine sediment cores from the Cascais Submarine Canyon (CSC; cores 252-32 and 252-35) and the Estremadura Spur (core 252-16) on the central Portuguese Margin were analysed for Hg, Pb, Al, and Mn concentrations, and both Pb and Hg stable isotope compositions, in order to reconstruct tren

  2. Energy Efficient Textile Drying

    OpenAIRE

    Brunzell, Lena

    2006-01-01

    Traditionally, textiles were dried outdoors with the wind and the sun enhancing the drying process. Tumble dryers offer a fast and convenient way of drying textiles independent of weather conditions. Tumble dryers, however, consume large amounts of electrical energy. Over 4 million tumble dryers are sold each year in Europe and a considerable amount of energy is used for drying of clothes. Increasing energy costs and the awareness about environmental problems related to a large energy use has...

  3. Use of hg-electroplated-pt ultramicroelectrode for determining elemental sulphur in naphtha samples.

    Science.gov (United States)

    de Andrade, Carlos Eduardo; de Souza, Flávia C; Fernandes, Daniella R; Machado, Sérgio A S; D'Elia, Eliane

    2012-01-01

    This paper describes the applicability of a Hg-electroplated-Pt ultramicroelectrode in the quantification of elemental sulphur in naphtha samples by square-wave voltammetry. A reproducible deposition methodology was studied and is reported in this paper. This methodology is innovative and relies on the quality of the mercury stock solution to obtain reproducible surfaces required for the analytical methodology. All analyses were performed using a Hg-electroplated-Pt ultramicroelectrode (Hg-Pt UME) due to the low sensibility of such devices to ohmic drops in resistive solutions. The responses of the peak areas in voltammetric experiments were linear in all of the range studied. The method developed here is accurate and reproducible, with a detection limit of 0.010 mg L(-1) and a good recovery range for both standard solutions of elemental sulphur (85 to 99%) and real naphtha sample (79%). These results attest to the potential for the application of this electroanalytical methodology in determining elemental sulphur in naphtha samples containing mercaptans and disulphides.

  4. Use of Hg-Electroplated-Pt Ultramicroelectrode for Determining Elemental Sulphur in Naphtha Samples

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo de Andrade

    2012-01-01

    Full Text Available This paper describes the applicability of a Hg-electroplated-Pt ultramicroelectrode in the quantification of elemental sulphur in naphtha samples by square-wave voltammetry. A reproducible deposition methodology was studied and is reported in this paper. This methodology is innovative and relies on the quality of the mercury stock solution to obtain reproducible surfaces required for the analytical methodology. All analyses were performed using a Hg-electroplated-Pt ultramicroelectrode (Hg-Pt UME due to the low sensibility of such devices to ohmic drops in resistive solutions. The responses of the peak areas in voltammetric experiments were linear in all of the range studied. The method developed here is accurate and reproducible, with a detection limit of 0.010 mg L−1 and a good recovery range for both standard solutions of elemental sulphur (85 to 99% and real naphtha sample (79%. These results attest to the potential for the application of this electroanalytical methodology in determining elemental sulphur in naphtha samples containing mercaptans and disulphides.

  5. A 6,000-years record of atmospheric mercury accumulation in the high Arctic from peat deposits on Bathurst Island, Nunavut, Canada

    DEFF Research Database (Denmark)

    Givelet, N.; Roos-Barraclough, F.; Goodsite, M. E.

    2003-01-01

    There is a growing interest in the atmospheric transport, deposition, and accumulation of anthropogenic Hg in the Arctic. To quantify the impact of industrial Hg emissions, the natural rate of atmospheric Hg accumulation must be known. Mercury concentration measurements and age dating of peat fro...

  6. Anthropogenic mercury deposition in Flin Flon Manitoba and the Experimental Lakes Area Ontario (Canada): A multi-lake sediment core reconstruction.

    Science.gov (United States)

    Wiklund, Johan A; Kirk, Jane L; Muir, Derek C G; Evans, Marlene; Yang, Fan; Keating, Jonathan; Parsons, Matthew T

    2017-02-18

    High-resolution records of anthropogenic mercury (Hg) deposition were constructed from 9 lakes located 5-75km from the Flin Flon, Manitoba smelter (formerly one of North America's largest atmospheric Hg point sources) and 5 lakes in Experimental Lakes Area (ELA), Ontario; a region remote from major Hg point sources. Anthropogenic Hg deposition, as both a flux and inventory, was determined after accounting for lake-specific natural Hg background concentrations, changes in sedimentation and sediment focusing. Results show that records of anthropogenic flux and inventory of Hg were remarkably consistent among the ELA lakes, but varied by 2 orders of magnitude among Flin Flon lakes. The relation between Hg inventories (normalized for prevailing wind direction) and distance from the smelter was used to estimate the total Hg fallout within a 50km radius in 5year time-steps, thus providing a quantitative spatial-temporal Hg depositional history for the Flin Flon region. The same relation solved for 8 cardinal directions weighted by the inverse of the previously applied wind direction normalization generates a map of Hg inventory and deposition on the landscape (Supplementary video). This novel application of sediment core data constructs a landscape model and allows for a visualization of contaminant deposition with respect to a point major source in both space and time. The propensity for Hg to undergo long-range, even global transport explains why Hg deposition within 50km of Flin Flon was ~11% of estimated releases. That is until smelter releases were reduced >10-fold (post-2000), after which observed deposition exceeded smelter releases, suggesting landscape re-emission/remobilization of legacy Hg is a major ongoing regional source of Hg.

  7. Review of Gaussian diffusion-deposition models

    Energy Technology Data Exchange (ETDEWEB)

    Horst, T.W.

    1979-01-01

    The assumptions and predictions of several Gaussian diffusion-deposition models are compared. A simple correction to the Chamberlain source depletion model is shown to predict ground-level airborne concentrations and dry deposition fluxes in close agreement with the exact solution of Horst.

  8. Impact of climate change on mercury concentrations and deposition in the eastern United States.

    Science.gov (United States)

    Megaritis, Athanasios G; Murphy, Benjamin N; Racherla, Pavan N; Adams, Peter J; Pandis, Spyros N

    2014-07-15

    The global-regional climate-air pollution modeling system (GRE-CAPS) was applied over the eastern United States to study the impact of climate change on the concentration and deposition of atmospheric mercury. Summer and winter periods (300 days for each) were simulated, and the present-day model predictions (2000s) were compared to the future ones (2050s) assuming constant emissions. Climate change affects Hg(2+) concentrations in both periods. On average, atmospheric Hg(2+) levels are predicted to increase in the future by 3% in summer and 5% in winter respectively due to enhanced oxidation of Hg(0) under higher temperatures. The predicted concentration change of Hg(2+) was found to vary significantly in space due to regional-scale changes in precipitation, ranging from -30% to 30% during summer and -20% to 40% during winter. Particulate mercury, Hg(p) has a similar spatial response to climate change as Hg(2+), while Hg(0) levels are not predicted to change significantly. In both periods, the response of mercury deposition to climate change varies spatially with an average predicted increase of 6% during summer and 4% during winter. During summer, deposition increases are predicted mostly in the western parts of the domain while mercury deposition is predicted to decrease in the Northeast and also in many areas in the Midwest and Southeast. During winter mercury deposition is predicted to change from -30% to 50% mainly due to the changes in rainfall and the corresponding changes in wet deposition.

  9. An investigation for the HgCdTe cleaning process

    Science.gov (United States)

    Lan, Tian-Yi; Wang, Nili; Zhao, Shuiping; Liu, Shi-Jia; Li, Xiang-Yang

    2014-11-01

    A new cleaning process for HgCdTe was designed - which used the improved SC-1,SC-2 and Br2- C2H5OH solutions as the main cleaning fluid and applied mega sound waves in the cleaning process. By analyzing the test results carried out on the HgCdTe surface, it was found that the material of HgCdTe for the application of new cleaning process was better than the one for the application of conventional cleaning process in the minority carrier lifetime, residual organic contamination, responsivity and specific detectivity.

  10. Doping and Diffusion in HgCdTe

    Science.gov (United States)

    1991-01-28

    In’i, -InT. Te - 1.8 ( - 3 .5 )h ( + 2.9 - 6/) TeT1’- Tej . 4 Hg rich HgCdTe Hg - 1.8 + 1.2 + 1.4 - 2p H - ’g, - H g j.. ’TI - tetrahedral position...A. Anderson, Appl. Phys. Lett. 53, 11.81 (1988). B. D. Patterson, Rev. Mod. Phys. 60, 69 (1988). 60 V. A. Singh , C. Weigel, J. W. Corbett, and L. M

  11. Review:Resuspension of wall deposits in spray dryers

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.

  12. Dry vacuum pumps

    Science.gov (United States)

    Sibuet, R.

    2008-05-01

    For decades and for ultimate pressure below 1 mbar, oil-sealed Rotary Vane Pumps have been the most popular solution for a wide range of vacuum applications. In the late 80ies, Semiconductor Industry has initiated the development of the first dry roughing pumps. Today SC applications are only using dry pumps and dry pumping packages. Since that time, pumps manufacturers have developed dry vacuum pumps technologies in order to make them attractive for other applications. The trend to replace lubricated pumps by dry pumps is now spreading over many other market segments. For the Semiconductor Industry, it has been quite easy to understand the benefits of dry pumps, in terms of Cost of Ownership, process contamination and up-time. In this paper, Technology of Dry pumps, its application in R&D/industries, merits over conventional pumps and future growth scope will be discussed.

  13. HgI{sub 2} detector fabrication; Construccion de detectores de HgI{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, M.; Perez, J. M.

    1996-07-01

    The aim of the present work is to describe the steps followed to fabricate an ionizing radiation detector based on synthetic mercuric iodide monocrystal layers. Firstly, the crystalline orientation method has been describe, which is needed before the layer cutting perpendicularly to the (001) crystallographic. It is also defined the proceeding to crystal face finishing by a mechanical polishing and subsequent chemical etching. then, the metal electrode deposition and the view connection has been explained. Finally, the technique followed to encapsulate the detector with a polymeric thin film deposition has been described. (Author) 10 refs.

  14. Deposição e acúmulo de matéria seca e nutrientes em serapilheira em um bosque de sabiá (Mimosa caesalpiniifolia Benth. Litter dry mass and nutrient deposition and accumulation in a sabiá (Mimosa caesalpiniifolia Benth. woodlot

    Directory of Open Access Journals (Sweden)

    Rinaldo Luiz Caraciolo Ferreira

    2007-02-01

    collected monthly from October 2000 to September 2001, and separated into leaves, twigs, flowers, pods and mixed portions. Undecomposed organic mantle was randomly sampled nearby collector boxes, to a total of 20 monthly samples, from which a 0.30 x 0.30 m composed sample was collected. The collected material was also hand separated into leaves, twigs, flowers, pods and mixed portions. All collected material was dried at 60°C until constant weight was achieved. Highest monthly litter deposition and leaf and pod fractions occurred in October, probably due to initiation of dry period. Litter deposition and stock were estimated at 7830.44 kg.ha-1.year-1 and 8906.9 kg.ha-1, respectively, with the leaf fraction dominating. Leaf fraction was the richest in nutrient content.

  15. Uptake of HgCl{sub 2} and MeHgCl in an insect cell line (Aedes albopictus C6/36)

    Energy Technology Data Exchange (ETDEWEB)

    Braeckman, B.; Cornelis, R.; Rzeznik, U.; Raes, H. [Univ. of Ghent (Belgium)

    1998-10-01

    The authors studied the uptake mechanism of mercuric chloride (Hg) and methylmercuric chloride (MeHg) in Aedes albopictus C6/36 cells. The uptake kinetics, together with the effect of temperature and a metabolic inhibitor (2,4-dinitrophenol) on the mercury accumulation, were examined. Both amounts of internalized Hg and MeHg increased linearly with the extracellular concentration. Initially, the influx rate was high for both metal species but MeHg was found to accumulate seven times faster than Hg. At longer exposure times it leveled off for Hg, while for MeHg, the intracellular concentration decreased. Hg toxicity was not significantly influenced by elevated temperatures; in contrast there was a marked decrease of the LC{sub 50/24 h} value for MeHg. On the other hand, Hg accumulation was temperature dependent but MeHg was not. The different toxicity and uptake rate of both mercury compounds can be explained in terms of membrane permeability and target site. For Hg the main target seems to be the plasma membrane, while MeHg readily crosses this barrier and reacts with intracellular targets. 2,4-Dinitrophenol had no effect on the accumulation of Hg but that of MeHg was doubled.

  16. Results Of Hg Speciation Testing On DWPF SMECT-1, SMECT-3, And SMECT-5 Samples

    Energy Technology Data Exchange (ETDEWEB)

    Bannochie, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-01-07

    The Savannah River National Laboratory (SRNL) was tasked with preparing and shipping samples for Hg speciation by Eurofins Frontier Global Sciences, Inc. in Seattle, WA on behalf of the Savannah River Remediation (SRR) Mercury Task Team. The thirteenth shipment of samples was designated to include Defense Waste Processing Facility (DWPF) Slurry Mix Evaporator Condensate Tank (SMECT) from Sludge Receipt and Adjustment Tank (SRAT) Batch 736 and 738 samples. Triplicate samples of each material were prepared for this shipment. Each replicate was analyzed for seven Hg species: total Hg, total soluble (dissolved) Hg, elemental Hg [Hg(0)], ionic (inorganic) Hg [Hg(I) and Hg(II)], methyl Hg [CH3Hg-X, where X is a counter anion], ethyl Hg [CH3CH2-Hg-X, where X is a counter anion], and dimethyl Hg [(CH3)2Hg]. The difference between the total Hg and total soluble Hg measurements gives the particulate Hg concentration, i.e. Hg adsorbed to the surface of particulate matter in the sample but without resolution of the specific adsorbed species. The average concentrations of Hg species in the aqueous samples derived from Eurofins reported data corrected for dilutions performed by SRNL are tabulated.

  17. Quantum Calorimeters Based on HgCdTe Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA's next generation of x-ray observation missions require x-ray calorimeters with superior energy resolution. Semimetallic HgTe has already proven itself as an...

  18. Enrichment of Pb, Hg and Cr in cultured carp otolith

    African Journals Online (AJOL)

    AJL

    2012-01-26

    Jan 26, 2012 ... record the pollution condition at the sampling time. ... aquatic organisms are aquatic algae, zooplankton .... element cannot show that Hg concentration in otolith ..... from Atlantic croaker along an estuarine pollution gradient.

  19. Quantum Calorimeters Based on HgCdTe Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA's next generation of x-ray observation missions require x-ray calorimeters with superior energy resolution. Semimetallic HgTe has already proven itself as an...

  20. Properties of Light Hg, Pb and Po Isotopes

    CERN Document Server

    Muntian, I

    2003-01-01

    Quality of mass description for three different theoretical mass models is studied. Masses and deformations for Po, Pb and Hg isotopes are compared with experimental data. Gap in the proton single particle energy spectrum is discussed.

  1. Horizontal Branch stars as AmFm/HgMn stars

    CERN Document Server

    Michaud, G

    2008-01-01

    Recent observations and models for horizontal branch stars are briefly described and compared to models for AmFm stars. The limitations of those models are emphasized by a comparison to observations and models for HgMn stars.

  2. Interaction of Hg Atom with Bare Si(111) Surface

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-Jun; LIU Ying

    2006-01-01

    To evaluate the interaction between Hg atom and bare Si(111) surface, three types of silicon cluster models of Si4H7, Si7H10 and Si16H20 together with their Hg complexes were studied by using hybrid (U)B3LYP density functional theory method. Optimized geometries and energies for Hg atom on different adsorption sites indicate that: 1) the binding energies at different adsorption sites are small (ranging from ~3 to 8 kJ/mol dependent on the adsorption sites), suggesting a weak interaction between Hg atom and silicon surface; 2) the most favorable adsorption site is the on top (T) site. By analyzing their natural bonding orbitals, the possible reason of this difference is suggested.

  3. Atmospheric wet deposition of mercury and other trace elements in Pensacola, Florida

    Directory of Open Access Journals (Sweden)

    W. M. Landing

    2009-12-01

    Full Text Available To understand and quantify the impact of local, regional, and distant atmospheric mercury sources to rainfall mercury deposition in the Pensacola, Florida watershed, a program of event-based rainfall sampling was started in late 2004. Modified Aerochem-Metrics wet/dry rainfall samplers were deployed at three sites in the region around the Crist coal-fired power plant and event-based samples were collected continuously for three years. Samples were analyzed for total mercury, volatile elements As, Se, and Sn, and a suite of trace elements including Al, Bi, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ho, Ga, Gd, La, Li, Lu, Mg, Mn, Na, Nb, Nd, Ni, P, Pb, Pr, Rb, Sb, Sc, Si, Sm, Sr, Tb, Th, Ti, Tm, U, V, Y, Yb, and Zn. Nutrients and major ions were also measured on each sample.

    Multivariate statistical methods are used to sort these tracers into factors that represent potential source components that contribute to the rainfall chemistry. Hg, As, Se, Sn, Sb, and non sea-salt sulfate were all significantly correlated with one anthropogenic factor. Using various Hg/element ratios, we can estimate that 22–33% of the rainfall mercury in the region results from coal combustion.

  4. Cardiac dysfunction in HgCl2-induced nephrotic syndrome.

    Science.gov (United States)

    Moreira-Rodrigues, Mónica; Henriques-Coelho, Tiago; Moura, Cláudia; Vasques-Nóvoa, Francisco; Sampaio-Maia, Benedita; Pestana, Manuel; Leite-Moreira, Adelino F

    2010-03-01

    The experimental model of HgCl(2) injection is characterized by a systemic autoimmune disease which leads to the development of nephrotic syndrome (NS). NS seems to be accompanied by cardiovascular alterations, since patients with NS present an increased incidence in cardiac disease. The aim of our work was to study the effects of HgCl(2)-induced NS on myocardial function and morphometry. Normotensive Brown-Norway rats were injected with HgCl(2) (1 mg/kg, HgCl(2) group; n = 6, subcutaneous) or the vehicle (control group; n = 6, subcutaneous) on days 0, 2, 4, 7, 9 and 11. The animals were placed in metabolic cages for evaluation of urinary excretion of noradrenaline, sodium, total proteins, albumin and creatinine. Fourteen and 21 days after the first HgCl(2) injection, left ventricle (LV) hemodynamics was evaluated through pressure micromanometers in basal and isovolumetric heartbeats. The heart and gastrocnemius muscle weights and tibial length were also examined. In an additional group of animals cardiac dimensions and ejection fraction were assessed by echocardiography and LV apoptosis and fibrosis were studied. HgCl(2)-injected rats presented proteinuria, albuminuria, hyperlipidemia, anemia, sodium retention and ascites at day 14. These alterations were accompanied by LV hemodynamic changes only in isovolumetric heartbeats. Similarly, on day 21, HgCl(2)-injected rats presented proteinuria, albuminuria, hyperlipidemia, anemia, but no sodium retention or ascites. These animals presented LV systolic and diastolic dysfunction in both basal and isovolumetric heartbeats, as well as cardiac atrophy, LV fibrosis and an increase in myocyte apoptosis. In conclusion, HgCl(2)-induced NS is accompanied by LV dysfunction and can be a promising model for studying the link between NS and cardiac disease.

  5. Searching for Line Profile Variability in HgMn Stars

    CERN Document Server

    Turcotte, S; Knoglinger, P

    2002-01-01

    Spectra of four non-magnetic chemically peculiar late B type stars (HgMn) stars are analysed to detect periodic spectral line variations (LPVs). A procedure developed to study LPVs in Slowly Pulsating B stars has been adopted as pulsational properties of HgMn stars should be expected to be similar. In the preliminary results discussed here no conclusive evidence for periodic LPVs was uncovered. A more sensitive re-analysis of the data is under way.

  6. First observation of excited states in 173Hg93

    CERN Document Server

    O'Donnell, D; Scholey, C; Bianco, L; Capponi, L; Carroll, R J; Darby, I G; Donosa, L; Drummond, M; Ertugral, F; Greenlees, P T; Grahn, T; Hauschild, K; Herzan, A; Jakobsson, U; Jones, P; Joss, D T; Julin, R; Juutinen, S; Ketelhut, S; Labiche, M; Leino, M; Lopez-Martens, A; Mullholland, K; Nieminen, P; Peura, P; Rahkila, P; Rinta-Antila, S; Ruotsalainen, P; Sandzelius, M; Saren, J; Saygi, B; Simpson, J; Sorri, J; Thornthwaite, A; Uusitalo, J

    2012-01-01

    The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of gamma rays decaying from excited states are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighbouring neutron-deficient Hg nuclei. In addition to the gamma-ray spectroscopy, the alpha decay of this nucleus has been measured yielding superior precision to earlier measurements.

  7. Crystal structure of K[Hg(SCN)3] - a redetermination.

    Science.gov (United States)

    Weil, Matthias; Häusler, Thomas

    2014-09-01

    The crystal structure of the room-temperature modification of K[Hg(SCN)3], potassium tri-thio-cyanato-mercurate(II), was redetermined based on modern CCD data. In comparison with the previous report [Zhdanov & Sanadze (1952 ▶). Zh. Fiz. Khim. 26, 469-478], reliability factors, standard deviations of lattice parameters and atomic coordinates, as well as anisotropic displacement parameters, were revealed for all atoms. The higher precision and accuracy of the model is, for example, reflected by the Hg-S bond lengths of 2.3954 (11), 2.4481 (8) and 2.7653 (6) Å in comparison with values of 2.24, 2.43 and 2.77 Å. All atoms in the crystal structure are located on mirror planes. The Hg(2+) cation is surrounded by four S atoms in a seesaw shape [S-Hg-S angles range from 94.65 (2) to 154.06 (3)°]. The HgS4 polyhedra share a common S atom, building up chains extending parallel to [010]. All S atoms of the resulting (1) ∞[HgS2/1S2/2] chains are also part of SCN(-) anions that link these chains with the K(+) cations into a three-dimensional network. The K-N bond lengths of the distorted KN7 polyhedra lie between 2.926 (2) and 3.051 (3) Å.

  8. Self-powered sensor for trace Hg2+ detection.

    Science.gov (United States)

    Wen, Dan; Deng, Liu; Guo, Shaojun; Dong, Shaojun

    2011-05-15

    A self-powered electrochemical sensor has been facilely designed for sensitive detection of Hg(2+) based on the inhibition of biocatalysis process of enzymatic biofuel cell (BFC) for the first time. The as-prepared one-compartment BFC, which was consisted of alcohol dehydrogenase supported on single-walled carbon nanohorns-based mediator system as the anode and bilirubin oxidase as the cathodic biocatalyst, generated an open circuit potential (V(oc)) of 636 mV and a maximum power density of 137 μW cm(-2). It was interestingly found that the presence of Hg(2+) would affect the performance of the constructed BFC (e.g., V(oc)). Taking advantage of the inhibitive effect of Hg(2+), a novel self-powered Hg(2+) sensor has been developed, which showed a linear range of 1-500 nM (R(2) = 0.999) with a detection limit of 1 nM at room temperature. In addition, this BFC-type sensor exhibited good selectivity for Hg(2+) against other common environmental metal ions, and the feasibility of the method for Hg(2+) detection in actual water samples (i.e., tap, ground, and lake water) was demonstrated with satisfactory results.

  9. NONMETALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>20102406 Chen Gang(China University of Geosciences,Beijing 100083,China);Li Fengming Discussion on Geological Characteristics and Genesis of Yuquanshan Graphite Deposit of Xinjiang(Xinjiang Geology,ISSN1000-8845,CN65-1092/P,27(4),2009,p.325-329,4 illus.,4 tables,5 refs.)Key words:graphite deposit,XinjiangYuquanshan graphite deposit of Xinjiang occurs in mica-quartz schist of Xingeer Information which belongs to Xinditate Group of Lower Pt in Kuluketage Block of Tarim paleo-continent,and experiences two mineralizing periods of

  10. Effect of Hg, As and Pb on biomass production, photosynthetic rate, nutrients uptake and phytochelatin induction in Pfaffia glomerata.

    Science.gov (United States)

    Gupta, D K; Huang, H G; Nicoloso, F T; Schetinger, M R; Farias, J G; Li, T Q; Razafindrabe, B H N; Aryal, N; Inouhe, M

    2013-11-01

    Plantlets of Pfaffia glomerata (Spreng.) were exposed for 28 days to three different metal/metalloid (Hg, Pb and As) with different levels (Hg 1; As 25, 50, 100 and Pb 100 and 400 μM) to analyze the possible phytochelatin initiation and affects on growth and photosynthetic pigments vis-à-vis metal accumulation potential of plants. The plantlets showed significant Hg, As and Pb accumulation in roots (150, 1267.67 and 2129 μg g(-1) DW respectively); however, a low root to shoot metal translocation was observed. It was interesting to note that all tested macronutrient (Mg, K, Ca) was higher in shoots and just opposite in case of micronutrients (Cu, Fe, Zn), was recorded highest in roots. The growth of plantlets (analyzed in terms of length and dry weight) was negatively affected by various metal treatments. In addition, the level of photosynthetic pigments alters significantly in response to all metal/metalloid treatment. In response to all tested metal/metalloids in plants only As induced phytochelatins (PC2, PC3 and PC4) in roots, and in shoots, GSH was observed in all tested metal/metalloids. In conclusion, P. glomerata plantlets could not cooperatively induce phytochelatins under any of Hg and Pb levels.

  11. Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania).

    Science.gov (United States)

    Bravo, Andrea G; Loizeau, Jean-Luc; Dranguet, Perrine; Makri, Stamatina; Björn, Erik; Ungureanu, Viorel Gh; Slaveykova, Vera I; Cosio, Claudia

    2016-06-01

    Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl(-) concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out.

  12. Drying and energy technologies

    CERN Document Server

    Lima, A

    2016-01-01

    This book provides a comprehensive overview of essential topics related to conventional and advanced drying and energy technologies, especially motivated by increased industry and academic interest. The main topics discussed are: theory and applications of drying, emerging topics in drying technology, innovations and trends in drying, thermo-hydro-chemical-mechanical behaviors of porous materials in drying, and drying equipment and energy. Since the topics covered are inter- and multi-disciplinary, the book offers an excellent source of information for engineers, energy specialists, scientists, researchers, graduate students, and leaders of industrial companies. This book is divided into several chapters focusing on the engineering, science and technology applied in essential industrial processes used for raw materials and products.

  13. Vacuum-assisted microwave drying characteristics of green bell pepper

    Directory of Open Access Journals (Sweden)

    Vivek Kumar

    2017-04-01

    Full Text Available Chopped green bell pepper pieces were blanched (95 °C, 5 min and chemically pretreated (1% potassium metabisulphite solution, 25 min at room temperature before drying in hot air dryer (HAD at various temperature ranges (60 – 80 °C. Three vacuum levels (200, 400, 600 mm Hg and microwave power levels (100, 200, 300 W were also used to dry green bell pepper samples in a vacuum assisted microwave (VAM (2.45 GHz, 0.8 kW dryer. VAM drying methods offered a maximum reduction by four to five times in drying time as compared to that in HAD. The logarithmic model was found to have the best fit based on high R2 and small values of reduced χ2 and RMSE.  VAM method has higher values for effective moisture diffusivity (Deff and lower values for activation energy (Ea, in comparison to the HAD method. 

  14. NONMETALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>20140876 Gao Junbo(College of Resources and Environmental Engineering,Guizhou University,Guiyang 550025,China);Yang Ruidong Study on the Strontium Isotopic Composition of Large Devonian Barite Deposits from Zhenning,Guizhou Province(Geochimica,

  15. Ambient Dried Aerogels

    Science.gov (United States)

    Jones, Steven M.; Paik, Jong-Ah

    2013-01-01

    A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

  16. Ocean Dynamics: Vietnam DRI

    Science.gov (United States)

    2014-09-30

    Dynamics: Vietnam DRI Robert Pinkel Marine Physical Laboratory Scripps Institution of Oceanography La Jolla California 92093-0213 Phone: (858) 534...DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Ocean Dynamics: Vietnam DRI 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM...cycle.. The Thorpe-scale estimates are local to Site III. South China Sea Process Cruise 2014 Under Vietnam DRI funding, Researcher Drew Lucas

  17. NONMETALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>20122457 Cai Jianshe ( Fujian Institute of Geological Survey and Drawing,Fuzhou 350011,China ) On the Geologic Characteristics and Genesis of the Longtangsi Fluorite Deposit in Pucheng County,Fujian Province ( Geology of Fujian,ISSN1001-3970,CN35-1080 / P,30 ( 4 ), 2011,p.301-306,3illus.,1table,6 refs.,with English abstract ) Key words:fluorspar deposit,Fujian Province

  18. Hg $L_{3}$ edge absorption study of the $HgBa_{2}CuO_{4}\\delta$ superconductor

    CERN Document Server

    Ziyu, Wu; Bianconi, A

    2001-01-01

    The HgBa/sub 2/CuO/sub 4+ delta / superconductor has been studied by high resolution Hg L/sub 3/ X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectrum has been simulated by full multiple-scattering calculations in order to explore the origin of different features in the experimental spectrum. The experimental Hg L/sub 3/-edge spectrum could be well reproduced by considering a cluster of 85 atoms, containing 10 shells, within a radius of about 7 AA from the central Hg atom. The low energy spectral feature in the XANES spectrum is found to be due to a transition from the Hg p states to the electronic states hybridized with higher shell Ba atoms. This implies that the transition features in the Hg L/sub 3/- edge XANES are strongly influenced by medium range order effects unlike the case of L/sub 3/ edge of 3d transition metals where short- range order is enough to describe the main transition features. (25 refs).

  19. Hg SOIL GAS AND Hg SOIL DISTRIBUTION AROUND FORMER „ZRINSKI“ MINE ON MT. MEDVEDNICA, CROATIA

    Directory of Open Access Journals (Sweden)

    Nataša Jug

    2008-12-01

    Full Text Available The purpose of this study is to present the field and laboratory researches, statistical analyses and graphical displays of the results of Hg soil gas and Hg soil distribution in the area around former mining site „Zrinski“ on Mt. Medvednica. The values of overall Hg concentrations in the soil gas show lognormal distribution, and their spatial distribution outlines the connection with the present Pb-Ag-Zn mineralization and confirms anthropogenic origin of uneven landscape relief (waste rock clusters. Regression analysis of the dependence between Hg contents in the soil gas and the distance from the mine entrance (correlation coefficient r also points to the considerable spatial dependence. Hg soil contents show as well distribution similar to lognormal, and there is a slight correlation when compared with Hg soil gas content. Concentrations are mostly within background values, except in the immediate vicinity of the mine entrance where the values are significantly higher due to the mineralization influence concentrated in the waste-rock clusters. Soil pollution caused by mercury is of local character with the spreading tendency to the south-west because of the dominant relief influence. Mercury found in the soil of the research location derives from the present mineral body and former mining activities, while possible anthropogenic atmospheric inputs from remote sources can not be proven on the basic of conducted research studies (the paper is published in Croatian.

  20. Dry etching for microelectronics

    CERN Document Server

    Powell, RA

    1984-01-01

    This volume collects together for the first time a series of in-depth, critical reviews of important topics in dry etching, such as dry processing of III-V compound semiconductors, dry etching of refractory metal silicides and dry etching aluminium and aluminium alloys. This topical format provides the reader with more specialised information and references than found in a general review article. In addition, it presents a broad perspective which would otherwise have to be gained by reading a large number of individual research papers. An additional important and unique feature of this book

  1. Atmospheric nitrogen budget in Sahelian dry savannas

    Directory of Open Access Journals (Sweden)

    C. Delon

    2010-03-01

    Full Text Available The atmospheric nitrogen budget depends on emission and deposition fluxes both as reduced and oxidized nitrogen compounds. In this study, a first attempt at estimating the Sahel nitrogen budget for the year 2006 is made, through measurements and simulations at three stations from the IDAF network situated in dry savanna ecosystems. Dry deposition fluxes are estimated from measurements of NO2, HNO3 and NH3 gaseous concentrations and from simulated dry deposition velocities, and wet deposition fluxes are calculated from NH4+ and NO3 concentrations in samples of rain. Emission fluxes are estimated including biogenic emission of NO from soils (an Artificial Neural Network module has been inserted into the ISBA-SURFEX surface model, emission of NOx and NH3 from domestic fires and biomass burning, and volatilization of NH3 from animal excreta. Uncertainties are calculated for each contribution of the budget.

    This study uses original and unique data from remote and hardly-ever-explored regions.The monthly evolution of oxidized N compounds shows that emission and deposition increase at the beginning of the rainy season because of large emissions of biogenic NO (pulse events. Emission of oxidized compounds is dominated by biogenic emission from soils (domestic fires and biomass burning of oxidized compounds account for 0 to 13% at the most at the annual scale, depending on the station, whereas emission of NH3 is dominated by the process of volatilization from soils. At the annual scale, the average gaseous dry deposition accounts for 47% of the total estimated deposition flux, for both oxidized and reduced compounds. The average estimated wet plus dry deposition flux in dry savanna ecosystems is 7.5±1.8 kgN ha−1 yr−1, with approximately 30% attributed to oxidized compounds, and the rest attributed

  2. Deposition of HgTe by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-04-01

    Full Text Available and Received 17 November 2005; received in revised 0022-0728/$ - see front matter � 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jelechem.2006.02.006 l atomic layer epitaxy (EC-ALE) n Jayaraju a, Stephen M. Cox b, Mathe a, John L. Stickney a... (1983). [7] N.H. Karam, R.G. Wolfson, I.B. Bhat, H. Ehsani, S.K. Ghandhi, Thin Solid Films 225 (1993) 261. [8] M.A.M. Seyam, A. Elfalaky, Vacuum 57 (2000) 31–41. [9] C. Janowitz, N. Orlowski, R. Manzke, Z. Golacki, J. Alloy. Compd. 328 (2001) 84...

  3. Historical atmospheric mercury emissions and depositions in North America compared to mercury accumulations in sedimentary records

    Science.gov (United States)

    Pirrone, Nicola; Allegrini, Ivo; Keeler, Gerald J.; Nriagu, Jerome O.; Rossmann, Ronald; Robbins, John A.

    Gold and silver production in North America (included United States, Canada and Mexico) released a large amount of mercury to the atmosphere until well into this century when mercury (Hg) amalgamation was replaced by cyanide concentration. Since then, emissions from industries have been the dominant anthropogenic sources of atmospheric Hg in North America as a whole. Past Hg emissions from gold and silver extractions in North America during the 1800s do not show a clear evidence of atmospheric deposition occurred at the coring sites considered in this study. Estimated atmospheric emissions of Hg in North America peaked in 1879 (at about 1708 t yr -1) and 1920 (at about 940 t yr -1), primarily due to Hg emissions from gold and silver mining. After the Great Economic Depression (1929) Hg emissions peaked again in the 1947 (274 t yr -1), in 1970 (325 t yr -1) and in 1989 (330 t yr -1) as result of increased Hg emissions from industrial sources, though improvements in the emissions control technology in United States and Canada have been substantial. Estimates of total atmospheric deposition fluxes of Hg to water and terrestrial receptors were in the range of 14.3-19.8 μg m -2 yr -1 in North America as a whole, and averaged 135 μg m -2 yr -1 (global background + local emissions) in the Great Lakes. These values were in good agreement with recent estimates reported in literature. The comparison of atmospheric Hg deposition fluxes with Hg accumulation rates in sediment cores suggests that atmospheric deposition was the major source of Hg entering the lakes system at coring sites, however, important contributions to Lake Ontario sediment cores sites from 1940 to 1970 were likely originated from local point sources (i.e. direct discharges).

  4. Four-year record of mercury wet deposition in one typical industrial city in southwest China

    Science.gov (United States)

    Qin, Caiqing; Wang, Yongmin; Peng, Yulong; Wang, Dingyong

    2016-10-01

    During the period from December 2010 to November 2014, long-term monitoring of Hg wet deposition was conducted at three sites in Chongqing. The four-year volume-weighted mean concentrations (VWC) of total mercury (THg) and methylmercury (MeHg) in precipitation were 34.25 ng L-1 and 0.48 ng L-1, respectively. The average annual wet deposition fluxes were 37.83 ± 11.53 μg m-2 yr-1 for THg and 0.61 ± 0.19 μg m-2 yr-1 for MeHg. Besides, the average proportion of MeHg in THg was 1.41%. These data were well ahead of values observed in most of other areas. The annual VWC of Hg rose remarkably in 2012 and then reached a plateau or climbed mildly in the following 2 years, while its annual wet deposition fluxes saw an upward trend throughout the whole period. In addition, the high figures of Hg concentration were generally found in the non-monsoon seasons, but its elevated wet deposition fluxes normally appeared in the rainy seasons. These characteristics of inter-annual and seasonal changes for VWC and fluxes were observed at every sampling site in this study as well. Besides, there were significantly spatial distributions for VWC and fluxes of THg in the descending order of the downtown (NA), the suburban (BB) and the controlled site (JY). While for MeHg, BB had the largest values, followed by NA and JY. So apart from THg load, the formation of MeHg was influenced by other factors in Chongqing, like the concentration of reactive mercury (RHg) in precipitation. Additionally, particulate bound mercury (PHg) is the dominant form among various Hg species, and atmospheric Hg is effectively eliminated during the initial period of the rain event and the below-cloud scavenging is the predominant mechanism contributing Hg to precipitation.

  5. Superconducting Hg-Based Mixed Oxides and Oxyfluorides

    Science.gov (United States)

    Antipov, E. V.

    2000-09-01

    Syntheses under high pressure and under controlled mercury and oxygen partial pressures of different members of the HgBa2Can-1CunO2n+2+δ series have been developed. There are two main parameters influencing Tc in this family: width of a perovskite slab (n) and concentration (δ) of the extra oxygen located in the Hg layer. The increase of Tc with n occurs until the third member, while after that it decreases. All the members of the series exhibit similar cupola shaped dependencies of Tc vs. δ. Strongly overdoped high members of the series with n = 3-5 were prepared only using high pressure technique and BaO2 as an internal oxidizer. Neutron powder diffraction experiments were carried out for monophase oxygenated HgBa2CuO4F4+δ and fluorinated HgBa2CuO4Fδ samples with different extra oxygen or fluorine content and Tc values. Fluorinated series also exhibits the cupola -like behavior for the Tc vs. δ dependence. NPD showed twice the amount of extra fluorine in comparison with those for the oxygenated Hg-1201 phases with close Tc's. The exchange of the extra oxygen by double amount of fluorine causes shortening of the apical Cu-O distances, while the in-plane ones, as well as Tc, do not vary. The influence of the external pressure on the structure and Tc of Hg-1201 strongly depends on the doping level. The increase of the extra oxygen content on going from underdoped to overdoped state results in the larger compression of the apical Cu-O and Ba-OHg distances while the HgO2 dumbbell as well as the distance between Ba and O from the (CuO2) layers becomes practically pressure independent. These results together with the data for fluorinated materials allow to elucidate the crucial structural features responsible for the Tc variation under high pressure.

  6. Natural and anthropogenic variations in atmospheric mercury deposition during the Holocene near Quelccaya Ice Cap, Peru

    Science.gov (United States)

    Beal, Samuel A.; Kelly, Meredith A.; Stroup, Justin S.; Jackson, Brian P.; Lowell, Thomas V.; Tapia, Pedro M.

    2014-04-01

    Mercury (Hg) is a toxic metal that is transported globally through the atmosphere. Emissions of Hg from mineral reservoirs and recycling between soil/biomass, oceans, and the atmosphere are fundamental to the global Hg cycle, yet past emissions from anthropogenic and natural sources are not fully constrained. We use a sediment core from Yanacocha, a headwater lake in southeastern Peru, to study the anthropogenic and natural controls on atmospheric Hg deposition during the Holocene. From 12.3 to 3.5 ka, Hg fluxes in the record are relatively constant (mean ± 1σ: 1.4 ± 0.6 µg m-2 a-1). Past Hg deposition does not correlate with changes in regional temperature and precipitation or with most large volcanic events that occurred regionally (~300-400 km from Yanacocha) and globally. In 1450 B.C. (3.4 ka), Hg fluxes abruptly increased and reached the Holocene-maximum flux (6.7 µg m-2 a-1) in 1200 B.C., concurrent with a ~100 year peak in Fe and chalcophile metals (As, Ag, Tl) and the presence of framboidal pyrite. Continuously elevated Hg fluxes from 1200 to 500 B.C. suggest a protracted mining-dust source near Yanacocha that is identical in timing to documented pre-Incan cinnabar mining in central Peru. During Incan and Colonial time (A.D. 1450-1650), Hg deposition remains elevated relative to background levels but lower relative to other Hg records from sediment cores in central Peru, indicating a limited spatial extent of preindustrial Hg emissions. Hg fluxes from A.D. 1980 to 2011 (4.0 ± 1.0 µg m-2 a-1) are 3.0 ± 1.5 times greater than preanthropogenic fluxes.

  7. Mercury (Hg) burden in children: The impact of dental amalgam

    Energy Technology Data Exchange (ETDEWEB)

    Al-Saleh, Iman, E-mail: iman@kfshrc.edu.sa [Biological and Medical Research Department, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211 (Saudi Arabia); Al-Sedairi, Al anoud [Department of Zoology, College of Science, King Saud University, PO Box: 24452, Riyadh 11495 (Saudi Arabia)

    2011-07-15

    The risks and benefits of using mercury (Hg) in dental amalgam have long been debated. This study was designed to estimate Hg body burden and its association with dental amalgam fillings in 182 children (ages: 5-15 years) living in Taif City. Hg was measured in urine (UHg), hair (HHg) and toenails (NHg) by the Atomic Absorption Spectrophotometer with Vapor Generator Accessory system. Urinary Hg levels were calculated as both micrograms per gram creatinine ({mu}g/g creatinine) and micrograms per liter ({mu}g/L). We found that children with amalgam fillings (N = 106) had significantly higher UHg-C levels than children without (N = 76), with means of 3.763 {mu}g/g creatinine versus 3.457 {mu}g/g creatinine, respectively (P = 0.019). The results were similar for UHg (P = 0.01). A similar pattern was also seen for HHg, with means of 0.614 {mu}g/g (N = 97) for children with amalgam versus 0.242 {mu}g/g (N = 74) for those without amalgam fillings (P = 0). Although the mean NHg was higher in children without amalgam (0.222 {mu}g/g, N = 61) versus those with (0.163 {mu}g/g, N = 101), the relationship was not significant (P = 0.069). After adjusting for many confounders, the multiple logistic regression model revealed that the levels of UHg-C and HHg were 2.047 and 5.396 times higher, respectively, in children with dental amalgam compared to those without (P < 0.01). In contrast, a significant inverse relationship was seen between NHg levels and dental amalgam fillings (P = 0.003). Despite the controversy surrounding the health impact of dental amalgam, this study showed some evidence that amalgam-associated Hg exposure might be related with symptoms of oral health, such as aphthous ulcer, white patches, and a burning-mouth sensation. Further studies are needed to reproduce these findings. The present study showed that significant numbers of children with or without amalgam had Hg levels exceeding the acceptable reference limits. The detrimental neurobehavioral and

  8. Overcoming phytoremediation limitations. A case study of Hg contaminated soil

    Science.gov (United States)

    Barbafieri, Meri

    2013-04-01

    Phytoremediation is a broad term that comprises several technologies to clean up water and soil. Despite the numerous articles appearing in scientific journals, very few field applications of phytoextraction have been successfully realized. The research here reported on Phytoextraction, the use the plant to "extract" metals from contaminated soil, is focused on implementations to overcome two main drawbacks: the survival of plants in unfavorable environmental conditions (contaminant toxicity, low fertility, etc.) and the often lengthy time it takes to reduce contaminants to the requested level. Moreover, to overcome the imbalance between the technology's potential and its drawbacks, there is growing interest in the use of plants to reduce only the fraction that is the most hazardous to the environment and human health, that is to target the bioavailable fractions of metals in soil. Bioavailable Contaminant Stripping (BCS) would be a remediation approach focused to remove the bioavailable metal fractions. BCS have been used in a mercury contaminated soil from Italian industrial site. Bioavailable fractions were determined by sequential extraction with H2O and NH4Cl.Combined treatments of plant hormone and thioligand to strength Hg uptake by crop plants (Brassica juncea and Helianthus annuus) were tested. Plant biomass, evapotranspiration, Hg uptake and distribution following treatments were compared. Results indicate the plant hormone, cytokinine (CK) foliar treatment, increased evapotranspiration rate in both tested plants. The Hg uptake and translocation in both tested plants increased with simultaneous addition of CK and TS treatments. B. juncea was the most effective in Hg uptake. Application of CK to plants grown in TS-treated soil lead to an increase in Hg concentration of 232% in shoots and 39% in roots with respect to control. While H. annuus gave a better response in plant biomass production, the application of CK to plants grown in TS-treated soil lead to

  9. Dry-Mass Sensing for Microfluidics

    CERN Document Server

    Müller, T; Knowles, T P J

    2014-01-01

    We present an approach for interfacing an electromechanical sensor with a microfluidic device for the accurate quantification of the dry mass of analytes within microchannels. We show that depositing solutes onto the active surface of a quartz crystal microbalance by means of an on-chip microfluidic spray nozzle and subsequent solvent removal provides the basis for the real-time determination of dry solute mass. Moreover, this detection scheme does not suffer from the decrease in the sensor quality factor and the viscous drag present if the measurement is performed in a liquid environment, yet allows solutions to be analysed. We demonstrate the sensitivity and reliability of our approach by controlled deposition of nanogram levels of salt and protein from a micrometer-sized channel.

  10. Methionine stimulates motor impairment and cerebellar mercury deposition in methylmercury-exposed mice.

    Science.gov (United States)

    Zimmermann, Luciana T; dos Santos, Danúbia B; Colle, Dirleise; dos Santos, Alessandra A; Hort, Mariana A; Garcia, Solange C; Bressan, Lucas Paines; Bohrer, Denise; Farina, Marcelo

    2014-01-01

    Methylmercury (MeHg) is a highly toxic environmental contaminant that produces neurological and developmental impairments in animals and humans. Although its neurotoxic properties have been widely reported, the molecular mechanisms by which MeHg enters the cells and exerts toxicity are not yet completely understood. Taking into account that MeHg is found mostly bound to sulfhydryl-containing molecules such as cysteine in the environment and based on the fact that the MeHg-cysteine complex (MeHg-S-Cys) can be transported via the L-type neutral amino acid carrier transport (LAT) system, the potential beneficial effects of L-methionine (L-Met, a well known LAT substrate) against MeHg (administrated as MeHg-S-Cys)-induced neurotoxicity in mice were investigated. Mice were exposed to MeHg (daily subcutaneous injections of MeHg-S-Cys, 10 mg Hg/kg) and/or L-Met (daily intraperitoneal injections, 250 mg/kg) for 10 consecutive days. After treatments, the measured hallmarks of toxicity were mostly based on behavioral parameters related to motor performance, as well as biochemical parameters related to the cerebellar antioxidant glutathione (GSH) system. MeHg significantly decreased motor activity (open-field test) and impaired motor performance (rota-rod task) compared with controls, as well as producing disturbances in the cerebellar antioxidant GSH system. Interestingly, L-Met administration did not protect against MeHg-induced behavioral and cerebellar changes, but rather increased motor impairments in animals exposed to MeHg. In agreement with this observation, cerebellar levels of mercury (Hg) were higher in animals exposed to MeHg plus L-Met compared to those only exposed to MeHg. However, this event was not observed in kidney and liver. These results are the first to demonstrate that L-Met enhances cerebellar deposition of Hg in mice exposed to MeHg and that this higher deposition may be responsible for the greater motor impairment observed in mice simultaneously

  11. Hg soil pollution around the Flix chlor-alkali plant

    Science.gov (United States)

    Esbrí, José Maria; López-Berdoces, Miguel Angel; Martínez-Coronado, Alba; Fernández-Calderon, Sergio; Díez, Sergi; León Higueras, Pablo

    2014-05-01

    meander, downstream the town area. Mercury seems to be partially available to plants, especially in the CAP surrounding area, where total mercury levels in olive leaves reach maximum values of 1.27 mg kg-1, and average concentration is 0.48 mg kg-1, higher than tolerable level for agronomic crops establish by Kabata-Pendias (2010) in 0.2 mg kg-1. Although correlation coefficients between Hgsoil-Hgplants are low, is possible to characterize plant absorption by logistic curves. Main conclusions of this work are: i) A fraction of mercury vapor emitted by CAP has been deposited on local soils by wet and dry deposition; ii) Mercury in local soils seems to be bioavailable for plants as highlights mercury levels in olive trees; iii) In this work we have identified risks areas with polluted soils.

  12. Spectroscopic variability and magnetic fields of HgMn stars

    CERN Document Server

    Hubrig, S; Ilyin, I; Korhonen, H; Savanov, I S; Dall, T; Schoeller, M; Cowley, C R; Briquet, M; Arlt, R

    2011-01-01

    The discovery of exotic abundances, chemical inhomogeneities, and weak magnetic fields on the surface of late B-type primaries in spectroscopic binaries has important implications not only for our understanding of the formation mechanisms of stars with Hg and Mn peculiarities themselves, but also for the general understanding of B-type star formation in binary systems. The origin of the abundance anomalies observed in late B-type stars with HgMn peculiarity is still poorly understood. The connection between HgMn peculiarity and membership in binary and multiple systems is supported by our observations during the last decade. The important result achieved in our studies of a large sample of HgMn stars is the finding that most HgMn stars exhibit spectral variability of various chemical elements, proving that the presence of an inhomogeneous distribution on the surface of these stars is a rather common characteristic and not a rare phenomenon. Further, in the studied systems, we found that all components are che...

  13. Bioaccumulation of Hg in the mushroom Pleurotus ostreatus

    Energy Technology Data Exchange (ETDEWEB)

    Bressa, G.; Cima, L.; Costa, P.

    1988-10-01

    The possibility of utilizing industrial, urban, and other wastes for the growth of a product which is directly edible by humans is fascinating. However, it is possible that many wastes containing toxic substances, for example, heavy metals, could reach the food chain and produce adverse effects on human health. To this end, we studied the possibility of bioaccumulation of Hg by a mushroom, Pleurotus ostreatus, grown on an artificial compost containing this element. Concentrations of 0.05, 0.1, and 0.2 mg/kg of Hg as Hg(NO/sub 3/)/sub 2/.H/sub 2/O were added to three groups of the same compost, successively inoculated with the mycelia of the mushroom. Higher concentrations strongly reduced the growth of the mycelia and therefore were not utilized. The concentrations of Hg in the substrate and in the mushroom were evaluated by AAS. The range of the accumulation factor was found to be 65-140, i.e., very marked. This finding suggests that the cultivation of P. ostreatus on substrates containing Hg from industrial and urban wastes could involve possible risks to human health.

  14. Are there tangled magnetic fields on HgMn stars?

    CERN Document Server

    Kochukhov, O; Piskunov, N; Jeffers, S V; Johns-Krull, C M; Keller, C U; Rodenhuis, M; Snik, F; Stempels, H C; Valenti, J A

    2013-01-01

    Several recent spectrophotometric studies failed to detect significant global magnetic fields in late-B HgMn chemically peculiar stars, but some investigations have suggested the presence of strong unstructured or tangled fields in these objects. We used detailed spectrum synthesis analysis to search for evidence of tangled magnetic fields in high-quality observed spectra of 8 slowly rotating HgMn stars and one normal late-B star. We also evaluated recent sporadic detections of weak longitudinal magnetic fields in HgMn stars based on the moment technique. Our analysis of the Zeeman broadening of magnetically sensitive spectral lines reveals no evidence of tangled magnetic fields in any of the studied HgMn or normal stars. We infer upper limits of 200-700 G for the mean magnetic field modulus -- much smaller than the field strengths implied by studies based on differential magnetic line intensification and quadratic field diagnostics. The new HARPSpol longitudinal field measurements for the extreme HgMn star H...

  15. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    Science.gov (United States)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  16. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Dry Eye ... Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué Es el Ojo Seco? Written By: Kierstan ...

  17. Chemical cycling and deposition of atmospheric mercury in polar regions: review of recent measurements and comparison with models

    Science.gov (United States)

    Angot, Hélène; Dastoor, Ashu; De Simone, Francesco; Gårdfeldt, Katarina; Gencarelli, Christian N.; Hedgecock, Ian M.; Langer, Sarka; Magand, Olivier; Mastromonaco, Michelle N.; Nordstrøm, Claus; Pfaffhuber, Katrine A.; Pirrone, Nicola; Ryjkov, Andrei; Selin, Noelle E.; Skov, Henrik; Song, Shaojie; Sprovieri, Francesca; Steffen, Alexandra; Toyota, Kenjiro; Travnikov, Oleg; Yang, Xin; Dommergue, Aurélien

    2016-08-01

    Mercury (Hg) is a worldwide contaminant that can cause adverse health effects to wildlife and humans. While atmospheric modeling traces the link from emissions to deposition of Hg onto environmental surfaces, large uncertainties arise from our incomplete understanding of atmospheric processes (oxidation pathways, deposition, and re-emission). Atmospheric Hg reactivity is exacerbated in high latitudes and there is still much to be learned from polar regions in terms of atmospheric processes. This paper provides a synthesis of the atmospheric Hg monitoring data available in recent years (2011-2015) in the Arctic and in Antarctica along with a comparison of these observations with numerical simulations using four cutting-edge global models. The cycle of atmospheric Hg in the Arctic and in Antarctica presents both similarities and differences. Coastal sites in the two regions are both influenced by springtime atmospheric Hg depletion events and by summertime snowpack re-emission and oceanic evasion of Hg. The cycle of atmospheric Hg differs between the two regions primarily because of their different geography. While Arctic sites are significantly influenced by northern hemispheric Hg emissions especially in winter, coastal Antarctic sites are significantly influenced by the reactivity observed on the East Antarctic ice sheet due to katabatic winds. Based on the comparison of multi-model simulations with observations, this paper discusses whether the processes that affect atmospheric Hg seasonality and interannual variability are appropriately represented in the models and identifies research gaps in our understanding of the atmospheric Hg cycling in high latitudes.

  18. NONMETALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20110947 Chen Xinglong(Guizhou Bureau of Nonferrous Metal and Nuclear Geology,Guiyang 550005,China);Gong Heqiang Endowment Factors and Development & Utilization Strategy of Bauxite Resource in North Guizhou Province(Guizhou Geology,ISSN1000-5943,CN52-1059/P,27(2),2010,p.106-110,6 refs.,with English abstract)Key words:bauxite deposit,Guizhou Province20110948 Dang Yanxia(Mineral Resource & Reservoir Evaluation Center,Urumiq 830000,China);Fan Wenjun Geological Features and a Primary Study of Metallogenesis of the Wucaiwang Zeolite Deposit,Fuyun County(Xinjiang Geology,ISSN1000-8845,CN65-1092/P,28(2),2010,p.167-170,2 illus.,1 table,5 refs.)Key words:zeolite deposit,Xinjiang Nearly all zeolite deposits in the world result from low-temperature-alteration of glass-bearing volcanic rocks.The southern slope of the Kalamali Mountain is one of the regions where medium to acid volcanics are major lithological type,thus it is a preferred area to look for zeolite deposit.The Wucaiwang zeolite ore district consists of mainly acid volcanic-clastic rocks.

  19. Dry imaging cameras

    Directory of Open Access Journals (Sweden)

    I K Indrajit

    2011-01-01

    Full Text Available Dry imaging cameras are important hard copy devices in radiology. Using dry imaging camera, multiformat images of digital modalities in radiology are created from a sealed unit of unexposed films. The functioning of a modern dry camera, involves a blend of concurrent processes, in areas of diverse sciences like computers, mechanics, thermal, optics, electricity and radiography. Broadly, hard copy devices are classified as laser and non laser based technology. When compared with the working knowledge and technical awareness of different modalities in radiology, the understanding of a dry imaging camera is often superficial and neglected. To fill this void, this article outlines the key features of a modern dry camera and its important issues that impact radiology workflow.

  20. Developing Depositional Models for Mercury Contaminated Floodplain Deposits Using Geomorphic Mapping and GIS in South River, Virginia

    Science.gov (United States)

    Barbieri, A.; Pizzuto, J.; O'Neal, M. A.; Rhoades, E.

    2007-12-01

    Mercury was introduced into the South River from the 1930s to the 1950s from an industrial plant in Waynesboro, Virginia. Mercury contamination in fish tissue continues to exceed acceptable levels. The contaminated sediments in the river's floodplains are probably the present source of mercury to the South River ecosystem. Locating and determining the extent and depositional history of these deposits are important for understanding the mercury cycle in the river as well as for remediation plans. The South River is a sinuous, single thread alluvial river with frequent bedrock exposures along its bed and banks. Overbank deposits are discontinuous and thin. Rates of lateral migration by the South River are extremely low, averaging 0.02 m/yr, and the river has been influenced by mill dams along a 19 km study reach. This 19 km section of the 37 km river reach was selected for the study because of its high concentration of Hg. Six different categories of floodplain deposits dating from 1937-2005 have been identified throughout the river using studies of historical aerial photographs in a GIS framework, field mapping, dendro- and radionuclide dating, grain size and Hg analysis. Not surprisingly, traditional depositional models of meandering rivers do not apply. Floodplain depositional units include mill dam deposits, point bar/bench deposits, concave bank bench deposits, islands, cattle deposits, and tributary confluences deposits. The most important deposits for sequestering historic mercury are those that also store the most silt and clay. These include mill dam deposits, point bar/bench deposits, concave bank deposits, and tributary confluence deposits. Many of these deposits represent reservoirs of mercury-contaminated sediments that could supply significant amounts of mercury into the river presently and in the future.

  1. Evaluation and development of soil values for the pathway 'soil to plant'. Significance of mercury evaporation for the burden of plants; Ueberpruefung und Fortentwicklung der Bodenwerte fuer den Boden-Pflanze-Pfad. Teilbericht 2: Evaporation von Quecksilber aus kontaminierten Boeden und deren Bedeutung fuer die Hg-Aufnahme von Kulturpflanzen

    Energy Technology Data Exchange (ETDEWEB)

    Schlueter, K.; Gaeth, S.

    2001-10-01

    In cooperation with the Ad-hoc working group 'Transfer of heavy metals from soil to plant' of the Laenderarbeitsgemeinschaft Bodenschutz (LABO) the significance of mercury evaporation for the deduction of threshold values in respect of the impact via the pathway soil to plant was investigated. Mercury contamination of food- and feeding stuff plants was examined with special emphasis. For these purposes a lab experiment including three different soils with varying initial mercury load (background level, geogenic and anthropogenic contamination) and two different plant species (parsley and spinach) was carried out under defined conditions in closed lysimeters. Mercury uptake via the roots was minimised since the plants grew in isolated customary substrate which showed a low concentration of mercury. Thus, only the surrounding soil evaporated mercury. The concentrations of mercury in the plants in the background level treatment (0.1 mg Hg/kg dry soil) were 0.15 mg/kg dry matter (spinach). The treatment with anthropogenic contaminated soil (111 mg Hg/kg dry soil) resulted in concentrations in the two plants of 2.0 and 2.6 mg/kg dry matter, respectively. A comparable order of magnitude was achieved in the geogenic contaminated treatment (34 mg Hg/kg dry soil) with 2.1 mg/kg dry matter (spinach) and 0.44 mg/kg dry matter (parsley). Experiments conducted with radioactive {sup 203}Hg showed in each case Hg-tracer in the leaves, in the stem and in the roots, indicating a translocation within the plant from leaf to root. By means of a comprehensive literature study the state of the art for Hg-evaporation and Hg-uptake of plants was compiled. Comparing the experimental results with data derived from literature, the Hg-concentrations found are confirmed by results of other authors. (orig.) [German] In fachlicher Zusammenarbeit mit der Ad-hoc-Arbeitsgruppe 'Schwermetalltransfer Boden/Pflanze' der Laenderarbeitsgemeinschaft Bodenschutz (LABO) wurde fuer die

  2. Atmospheric Sulfur Deposition for a Red Soil Broadleaf Forest in Southern China

    Institute of Scientific and Technical Information of China (English)

    XU Cheng-Kai; HU Zheng-Yi; CAI Zu-Cong; WANG Ti-Jian; HE Yuan-Qiu; CAO Zhi-Hong

    2004-01-01

    A two-year study in a typical red soil region of Southern China was conducted to determine 1) the dry deposition velocity (Vd) for SO2 and particulate SO2 4- above a broadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of various fractions in the total. Using a resistance model based on continuous hourly meteorological data, atmospheric dry sulfur deposition in a forest was estimated according to Vd and concentrations of both atmospheric SO2 and particulate SO24-. Meanwhile, wet S deposition was estimated based on rainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the dry sulfur deposition flux in the forest resulted from SO2 dry deposition.In addition, the observed dry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO2 in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO2 in 2002. Also,dry SO2 deposition was the dominant fraction of deposited atmospheric sulfur in forests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO2 deposition should be considered when estimating sulfur balance in forest ecological systems.

  3. Scale formation in deluged dry cooling systems

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, D.R.

    1976-05-01

    Deluging of air-cooled heat exchangers with water during warm periods holds the promise of increasing heat rejection capability and reducing the cost of dry cooling. One of the principal uncertainties in the use of the deluge concept is the tendency toward deposition of solids from the delugate. Small amounts of calcium carbonate scale may significantly reduce the cooling efficiency of a deluged system by reducing the heat transfer coefficient and interfering with delugate flow. Thus the question of delugate water quality is of major importance in evaluating scale formation and its effect on heat transfer in the deluged dry cooling system. The paper discusses, in relation to the deluged dry cooling system, the importance of scale prevention, the theory of scale formation and application of this theory to the deluged system, the problems of delugate evaporation, and delugate treatment required to prevent scaling.

  4. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>20091594 Bao Yafan(The Third Geologic Survey of Jilin Province,Siping 136000,China);Liu Yanjun Relations between Bashenerxi Granite,West Dongkunlun and Baiganhu Tungsten-Tin Deposit(Jilin Geology,ISSN1001-2427,CN22-1099/P,27(3),2008,p.56-59,67,5 illus.,2 tables,7 refs.,with English abstract)Key words:tungsten ores,tin ores,monzogranite,Kunlun Mountains20091595 Chen Fuwen(Yichang Institute of Geology and Mineral Resources,China Geological Survey,Yichang 443003,China);Dai Pingyun Metallogenetic and Isotopic Chronological Study on the Shenjiaya Gold Deposit in Xuefeng Mountains,Hunan Province(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,82(7),2008,p.906-911,3 illus.,2 tables,30 refs.)Key words:gold ores,HunanThe Shenjiaya gold deposit is a representative one

  5. Crystal structure of Hg2SO4 – a redetermination

    Directory of Open Access Journals (Sweden)

    Matthias Weil

    2014-09-01

    Full Text Available The crystal structure of mercury(I sulfate (or mercurous sulfate, Hg2SO4, was re-determined based on modern CCD data. In comparison with the previous determination from Weissenberg film data [Dorm (1969. Acta Chem. Scand. 23, 1607–1615], all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles [e.g. Hg—Hg = 2.5031 (7 compared to 2.500 (3Å]. The structure consists of alternating rows along [001] of Hg22+ dumbbells (generated by inversion symmetry and SO42− tetrahedra (symmetry 2. The dumbbells are linked via short O—Hg—Hg—O bonds to the sulfate tetrahedra into chains extending parallel to [20-1]. More remote O—Hg—Hg—O bonds connect these chains into a three-dimensional framework.

  6. Characterization studies of purified HgI{sub 2} precursors

    Energy Technology Data Exchange (ETDEWEB)

    Schieber, M. E-mail: Schieber@vms.huji.ac.il; Zuck, A.; Sanguinetti, S.; Montalti, M.; Braiman, M.; Melekhov, L.; Nissenbaum, J.; Grilli, E.; Guzzi, M.; Turchetta, R.; Dulinski, W.; Husson, D.; Riester, J.L

    1999-06-01

    The ability of HgI{sub 2} powders, used as precursors in mercuric iodide crystal growth, to produce high-quality detectors may be predicted by non-destructive methods like photoluminescence. In fact, it is possible to correlate the presence and the intensity ratio of specific bands in the photoluminescence spectrum of a HgI{sub 2} crystal to its impurity content and stoichiometry. These quantities determine the detector grade that may be achieved using that starting material. Nine different HgI{sub 2} precursors, obtained by different purification methods, have been characterized. The lowest impurity content is achieved via poly-ethylene treatment, which gives also a powder of relatively good stoichiometric quality.

  7. Atmospheric Sulfur Deposition on Farmland in East China

    Institute of Scientific and Technical Information of China (English)

    WANG Ti-Jian; YANG Hao-Ming; GAO Li-Jie; ZHANG Yan; HU Zheng-Yi; XU Cheng-Kai

    2005-01-01

    Atmospheric sulfur deposition onto typical farmland in East China was investigated using both field measurements and numerical modeling. The field measurements were conducted at the Experiment Station of Red Soil Ecology, Chinese Academy of Sciences, 10 km from Yingtan, Jiangxi Province, East China, between November 1998 and October 1999, and at the Changshu Ecological Experiment Station, Chinese Academy of Sciences, in a rapidly developing region of Jiangsu Province, East China, between April 2001 and March 2002. The regional acid deposition model system (RegADMS), in which the dry deposition velocities of SO2 and sulfate aerosols (SO42-) were estimated using a big-leaf resistance analogy model, was applied to simulate air sulfur deposition over East China and sulfur deposition onto lands of different use types in East China. The wet scavenging coefficients were parameterized in terms of precipitation rate, and the effect of sub-grid processes due to inhomogeneous land use on dry deposition velocity was also included. Results of the field measurements showed that over 83% of the total sulfur deposition at the Yingtan site was dry deposition, while at the Changshu site42% was dry deposition. The total sulfur deposition was much larger at the Yingtan site than at the Changshu site, which suggested contrasting air pollution and meteorological situations. The modeling results revealed that the total annual sulfur deposition over East China was 1.88 Mt, of which 72.8% was deposited onto farmland, and dry deposition accounted for 43% of the total sulfur deposited. The modeling results were generally in agreement with those from the observations.Overall, this study suggested that atmospheric sulfur deposition played an important role in the soil sulfur balance, which could have a significant effect on agricultural ecosystems in the study region.

  8. [Experimental Research of Hg (II) Removal from Aqueous Solutions of HgCl2 with Nano-TiO2].

    Science.gov (United States)

    Zhou, Xiong; Zhang, Jin-yang; Wang, Ding-yong; Qin, Cai-qing; Xu, Feng; Luo Cheng-zhong; Yang, Xi

    2016-01-15

    Mercury removal from aqueous solutions of HgCl2 was studied by indoor simulation experiments, and the effects of three different diameter of particles of Nano-TiO2 ( Nano-Titanium Dioxide) at different dosage, pH, adsorption time and the initial concentration of Hg2+ on the mercury adsorption from simulated wastewater were investigated. The single factor experiments showed that the optimal conditions were: 7.5 g x L(-1) of 5 nm TiO2 or 2.0 g x L(-1) of 100 nm TiO2, pH 8.0, initial concentration of Hg2+ 15 x mg x L(-1) adsorption time 5 min, and under these conditions the adsorption rates reached 99.5% and 99.3%, relatively. When the content of 25 nm TiO2 was 10 g x L(-1), and the other conditions were pH 8.0, initial concentration of Hg2+ 15 mg x L(-1), adsorption time 60 min, the adsorption rate was 62.8%. The Hg(II) removal effects of the TiO2 particles with different diameters followed the order of 100 nm TiO2 > 5 nm TiO2 > 25 nm TiO2. Component adsorption results showed that the 5 nm TiO2 component adsorption effect was superior to its single adsorption effect, while there was little difference between 100 nm TiO2 component adsorption effect and its single adsorption effect. The results of orthogonal experiments indicated that the influencing factors of the adsorption rate followed the order of pH > the initial concentration of Hg2+ > time > dosage. The optimal experiment scheme was: pH 8.0, a dosage of 100 nm Nano-TiO2 of 2.0 g x L(-1) an initial Hg2+ concentration of 25 mg x L(-1) and adsorption time of 10 min. Under the experimental conditions, the maximum adsorption rate reached 99.9%, at the same time, the equilibrium concentration of Hg(II) was 0.033 mg x L(-1) adsorptive capacity was 26.95 mg x g(-1). The adsorption isotherm was in line with the Langmuir isotherm equation, indicating that the Hg(II) uptake by 100 nm Nano-TiO2 was typical monolayer adsorption.

  9. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20111705 An Junbo(Team 603,Bureau of Nonferrous Metals Geological Exploration of Jilin Province,Hunchun 133300,China);Xu Renjie Geological Features and Ore Genesis of Baishilazi Scheelite Deposit in Yanbian Area(Jilin Geology,ISSN1001-2427,CN22-1099/P,29(3),2010,p.39-43,2 illus.,2 tables,7 refs.)Key words:tungsten ores,Jilin ProvinceThe Baishilazi scheelite deposit is located in contacting zone between the marble of the Late Palaeozoic Qinglongcun Group and the Hercynian biotite granite.The vein and lenticular major ore body is obviously controlled by NE-extending faults and con

  10. Mercury (Hg) burden in children: the impact of dental amalgam.

    Science.gov (United States)

    Al-Saleh, Iman; Al-Sedairi, Al Anoud

    2011-07-15

    The risks and benefits of using mercury (Hg) in dental amalgam have long been debated. This study was designed to estimate Hg body burden and its association with dental amalgam fillings in 182 children (ages: 5-15 years) living in Taif City. Hg was measured in urine (UHg), hair (HHg) and toenails (NHg) by the Atomic Absorption Spectrophotometer with Vapor Generator Accessory system. Urinary Hg levels were calculated as both micrograms per gram creatinine (μg/g creatinine) and micrograms per liter (μg/L). We found that children with amalgam fillings (N=106) had significantly higher UHg-C levels than children without (N=76), with means of 3.763 μg/g creatinine versus 3.457 μg/g creatinine, respectively (P=0.019). The results were similar for UHg (P=0.01). A similar pattern was also seen for HHg, with means of 0.614 μg/g (N=97) for children with amalgam versus 0.242 μg/g (N=74) for those without amalgam fillings (P=0). Although the mean NHg was higher in children without amalgam (0.222 μg/g, N=61) versus those with (0.163 μg/g, N=101), the relationship was not significant (P=0.069). After adjusting for many confounders, the multiple logistic regression model revealed that the levels of UHg-C and HHg were 2.047 and 5.396 times higher, respectively, in children with dental amalgam compared to those without (Pdental amalgam fillings (P=0.003). Despite the controversy surrounding the health impact of dental amalgam, this study showed some evidence that amalgam-associated Hg exposure might be related with symptoms of oral health, such as aphthous ulcer, white patches, and a burning-mouth sensation. Further studies are needed to reproduce these findings. The present study showed that significant numbers of children with or without amalgam had Hg levels exceeding the acceptable reference limits. The detrimental neurobehavioral and/or nephrotoxic effects of such an increased Hg on children should be a cause of concern, and further investigation is warranted. Our

  11. Crystal Growth of Solid Solution HgCdTe Alloys

    Science.gov (United States)

    Lehoczky, Sandor L.

    1997-01-01

    The growth of homogenous crystals of HgCdTe alloys is complicated by the large separation between their liquidus and solidus temperatures. Hg(1-x)Cd(x)Te is representative of several alloys which have electrical and optical properties that can be compositionally tuned for a number of applications. Limitations imposed by gravity during growth and results from growth under reduced conditions are described. The importance of residual accelerations was demonstrated by dramatic differences in compositional distribution observed for different attitudes of the space shuttle that resulted in different steady acceleration components.

  12. Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury.

    Science.gov (United States)

    Perrot, Vincent; Masbou, Jeremy; Pastukhov, Mikhail V; Epov, Vladimir N; Point, David; Bérail, Sylvain; Becker, Paul R; Sonke, Jeroen E; Amouroux, David

    2016-02-01

    In the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ(202)Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼ 3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ(199)Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposure.

  13. Atmospheric nitrogen budget in Sahelian dry savannas

    Directory of Open Access Journals (Sweden)

    C. Delon

    2009-06-01

    Full Text Available The atmospheric nitrogen budget depends on emission and deposition fluxes both as reduced and oxidized nitrogen compounds. In this study, a first attempt at estimating the Sahel nitrogen budget for the year 2006 is made, through measurements and simulations at three stations from the IDAF network situated in dry savanna ecosystems. Dry deposition fluxes are estimated from measurements of NO2, HNO3 and NH3 gaseous concentrations, and wet deposition fluxes are calculated from NH4+ and NO3 concentrations in samples of rain. Emission fluxes are estimated including biogenic emission of NO from soils (an Artificial Neural Network module has been inserted into the ISBA-SURFEX surface model, emission of NOx and NH3 from domestic fires and biomass burning, and volatilization of NH3 from animal excreta.

    This study uses original and unique data from remote and hardly-ever-explored regions. The monthly evolution of oxidized N compounds shows that deposition increases at the beginning of the rainy season because of large emissions of biogenic NO (pulse events. Emission of oxidized compounds is dominated by biogenic emission from soils (domestic fires and biomass burning account for 27% at the most, depending on the station, whereas emission of NH3 is dominated by the process of volatilization. Deposition fluxes are dominated by gaseous dry deposition processes (58% of the total, for both oxidized and reduced compounds. The average deposition flux in dry savanna ecosystems ranges from 8.6 to 10.9 kgN ha−1 yr−1, with 30% attributed to oxidized compounds, and the other 70% attributed to NHx. The average emission flux ranges from 7.8 to 9.7 kgN ha−1 yr−1, dominated by NH3 volatilization (67% and biogenic emission from soils (24%. The annual budget is then

  14. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>20090243 Chen Zhibin (Hebei Institute of Geological Survey, Shijiazhuang 050081, China) Ore-Controlling Factors of the Beichagoumen Ag-Polymetallic Deposits in Northern Hebei Province (Geological Survey and Research, ISSN1672-4135, CN12-1353/P, 31(1), 2008, p.1-5, 3 illus., 10 refs.)

  15. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>20131565 Cai Lianyou(No.332 Geological Team,Bureau of Geology and Mineral Resources Exploration of Anhui Province,Huangshan 245000,China);Weng Wangfei Geological Characteristics and Genesis Analysis of Guocun Navajoite Deposit in South Anhui Province(Mineral Resources and Geology,

  16. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>20102341 Bao Peisheng(Institute of Geology,Chinese Academy of Geological Science,Beijing 100037,China)Further Discussion on the Genesis of the Podiform Chromite Deposits in the Ophiolites-Questioning about the Rock:Melt Interaction Metallogeny(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,28(12),2009,p.1741-1761

  17. NONMETALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    <正>20131601 Gao Junbo(College of Resources and Environmental Engineering,Guizhou University,Guiyang 550003,China);Yang Ruidong Hydrothermal Venting-Flowing Sedimentation Characteristics of Devonian Barite Deposits from Leji,Zhenning County,Guizhou Province(Acta Sedimentologica Sinica,ISSN1000-0550,CN62-1038/P,30(3),

  18. Stripping with dry ice

    Science.gov (United States)

    Malavallon, Olivier

    1995-04-01

    Mechanical-type stripping using dry ice (solid CO2) consists in blasting particles of dry ice onto the painted surface. This surface can be used alone or in duplex according to type of substrate to be treated. According to operating conditions, three physical mechanisms may be involved when blasting dry ice particles onto a paint system: thermal shock, differential thermal contraction, and mechanical shock. The blast nozzle, nozzle travel speed, blast angle, stripping distance, and compressed air pressure and media flow rate influence the stripping quality and the uniformity and efficiency obtained.

  19. A 20-year simulated climatology of global dust aerosol deposition.

    Science.gov (United States)

    Zheng, Yu; Zhao, Tianliang; Che, Huizheng; Liu, Yu; Han, Yongxiang; Liu, Chong; Xiong, Jie; Liu, Jianhui; Zhou, Yike

    2016-07-01

    Based on a 20-year (1991-2010) simulation of dust aerosol deposition with the global climate model CAM5.1 (Community Atmosphere Model, version 5.1), the spatial and temporal variations of dust aerosol deposition were analyzed using climate statistical methods. The results indicated that the annual amount of global dust aerosol deposition was approximately 1161±31Mt, with a decreasing trend, and its interannual variation range of 2.70% over 1991-2010. The 20-year average ratio of global dust dry to wet depositions was 1.12, with interannual variation of 2.24%, showing the quantity of dry deposition of dust aerosol was greater than dust wet deposition. High dry deposition was centered over continental deserts and surrounding regions, while wet deposition was a dominant deposition process over the North Atlantic, North Pacific and northern Indian Ocean. Furthermore, both dry and wet deposition presented a zonal distribution. To examine the regional changes of dust aerosol deposition on land and sea areas, we chose the North Atlantic, Eurasia, northern Indian Ocean, North Pacific and Australia to analyze the interannual and seasonal variations of dust deposition and dry-to-wet deposition ratio. The deposition amounts of each region showed interannual fluctuations with the largest variation range at around 26.96% in the northern Indian Ocean area, followed by the North Pacific (16.47%), Australia (9.76%), North Atlantic (9.43%) and Eurasia (6.03%). The northern Indian Ocean also had the greatest amplitude of interannual variation in dry-to-wet deposition ratio, at 22.41%, followed by the North Atlantic (9.69%), Australia (6.82%), North Pacific (6.31%) and Eurasia (4.36%). Dust aerosol presented a seasonal cycle, with typically strong deposition in spring and summer and weak deposition in autumn and winter. The dust deposition over the northern Indian Ocean exhibited the greatest seasonal change range at about 118.00%, while the North Atlantic showed the lowest seasonal

  20. Atmospheric chemistry of mercury in Antarctica and the role of cryptogams to assess deposition patterns in coastal ice-free areas.

    Science.gov (United States)

    Bargagli, R

    2016-11-01

    Mercury in the Antarctic troposphere has a distinct chemistry and challenging long-term measurements are needed for a better understanding of the atmospheric Hg reactions with oxidants and the exchanges of the various mercury forms among air-snow-sea and biota. Antarctic mosses and lichens are reliable biomonitors of airborne metals and in short time they can give useful information about Hg deposition patterns. Data summarized in this review show that although atmospheric Hg concentrations in the Southern Hemisphere are lower than those in the Northern Hemisphere, Antarctic cryptogams accumulate Hg at levels in the same range or higher than those observed for related cryptogam species in the Arctic, suggesting an enhanced deposition of bioavailable Hg in Antarctic coastal ice-free areas. In agreement with the newest findings in the literature, the Hg bioaccumulation in mosses and lichens from a nunatak particularly exposed to strong katabatic winds can be taken as evidence for a Hg contribution to coastal ecosystems by air masses from the Antarctic plateau. Human activities on the continent are mostly concentrated in coastal ice-free areas, and the deposition in these areas of Hg from the marine environment, the plateau and anthropogenic sources raises concern. The use of Antarctic cryptogams as biomonitors will be very useful to map Hg deposition patterns in costal ice-free areas and will contribute to a better understanding of Hg cycling in Antarctica and its environmental fate in terrestrial ecosystems.

  1. Significant interaction effects from sulfate deposition and climate on sulfur concentrations constitute major controls on methylmercury production in peatlands

    Science.gov (United States)

    Åkerblom, Staffan; Bishop, Kevin; Björn, Erik; Lambertsson, Lars; Eriksson, Tobias; Nilsson, Mats B.

    2013-02-01

    Transformation of inorganic mercury (Hg) to methyl mercury (MeHg) in peatlands is a key process in making boreal catchments a source of MeHg to freshwater ecosystems. Due to the importance of sulfur-reducing bacteria (SRB) for this process, past atmospheric deposition of sulfate (SO42-) may have increased net terrestrial Hg methylation. A long-term (14-year) factorial design field experiment was used to investigate the effect of enhanced SO42- deposition and raised temperature using a greenhouse (GH) treatment (air temperature˜+4 °C; soil temperature 20 cm below mire surface ˜+2 °C) on sulfur (S) turnover, net Hg methylation, MeHg and total Hg concentrations in a boreal mire in northern Sweden. Of the SO42--S added during 14 years, 50% was retained in the plots without GH treatment while the combination of SO42- addition and GH treatment resulted in 15% S retention. The addition of SO42- (7-fold ambient SO42--deposition) increased (p important than the concentration of Hg for the production of MeHg in this boreal landscape. These results also show that long-term chronic SO42- deposition at rates similar to those found in polluted areas of Europe and North America increase the capacity of wetlands to methylate Hg and store MeHg, which can ultimately be released to streams and lakes. This study also, for the first time, indicates that the enhancing effect of SO42- on the production of MeHg might be counteracted by increased temperature.

  2. Variations in stable isotope fractionation of Hg in food webs of Arctic lakes.

    Science.gov (United States)

    Gantner, Nikolaus; Hintelmann, Holger; Zheng, Wang; Muir, Derek C

    2009-12-15

    Biotic and abiotic fractionation of mercury (Hg) isotopes has recently been shown to occur in aquatic environments. We determined isotope ratios (IRs) of Hg in food webs (zooplankton, chironomids, Arctic char) and sediments of 10 Arctic lakes from four regions and investigated the extent of Hg isotope fractionation. Hg IRs were analyzed by multicollector inductively coupled plasma mass spectrometry (MC-ICP/MS). Hg mass independent fractionation (MIF; Delta(199)Hg) and mass dependent fractionation (MDF; delta(202)Hg) were calculated and compared among samples. IRs of Hg in sediment were characterized mainly by MDF and low MIF (Delta(199)Hg -0.37 to 0.74 per thousand). However, all biota showed evidence of MIF, most pronounced in zooplankton (Delta(199)Hg up to 3.40 per thousand) and char (Delta(199)Hg up to 4.87 per thousand). Zooplankton takes up highly fractionated MeHg directly from the water column, while benthic organisms are exposed to sedimentary Hg, which contains less fractionated Hg. As evidenced by delta(13)C measurements, benthic chironomids make up a large proportion of char diet, explaining in part why MIF(char) meteor impact crater lake (Pingualuk) reflects a "pure" atmospheric Hg signature, which is modified only by aqueous in-lake processes. All other lakes are also affected by terrestrial Hg inputs and sediment processes.