Comparison of Efficiencies and Mechanisms of Catalytic Ozonation of Recalcitrant Petroleum Refinery Wastewater by Ce, Mg, and Ce-Mg Oxides Loaded Al2O3

Directory of Open Access Journals (Sweden)

Chunmao Chen

2017-02-01

Full Text Available The use of catalytic ozonation processes (COPs for the advanced treatment of recalcitrant petroleum refinery wastewater (RPRW is rapidly expanding. In this study, magnesium (Mg, cerium (Ce, and Mg-Ce oxide-loaded alumina (Al2O3 were developed as cost efficient catalysts for ozonation treatment of RPRW, having performance metrics that meet new discharge standards. Interactions between the metal oxides and the Al2O3 support influence the catalytic properties, as well as the efficiency and mechanism. Mg-Ce/Al2O3 (Mg-Ce/Al2O3-COP reduced the chemical oxygen demand by 4.7%, 4.1%, 6.0%, and 17.5% relative to Mg/Al2O3-COP, Ce/Al2O3-COP, Al2O3-COP, and single ozonation, respectively. The loaded composite metal oxides significantly increased the hydroxyl radical-mediated oxidation. Surface hydroxyl groups (–OHs are the dominant catalytic active sites on Al2O3. These active surface –OHs along with the deposited metal oxides (Mg2+ and/or Ce4+ increased the catalytic activity. The Mg-Ce/Al2O3 catalyst can be economically produced, has high efficiency, and is stable under acidic and alkaline conditions.

Impacts of Climate Change on Surface Ozone and Intercontinental Ozone Pollution: A Multi-Model Study

Science.gov (United States)

Doherty, R. M.; Wild, O.; Shindell, D. T.; Zeng, G.; MacKenzie, I. A.; Collins, W. J.; Fiore, A. M.; Stevenson, D. S.; Dentener, F. J.; Schultz, M. G.;

Band-Bending of Ga-Polar GaN Interfaced with Al2O3 through Ultraviolet/Ozone Treatment.

Science.gov (United States)

Kim, Kwangeun; Ryu, Jae Ha; Kim, Jisoo; Cho, Sang June; Liu, Dong; Park, Jeongpil; Lee, In-Kyu; Moody, Baxter; Zhou, Weidong; Albrecht, John; Ma, Zhenqiang

2017-05-24

Understanding the band bending at the interface of GaN/dielectric under different surface treatment conditions is critically important for device design, device performance, and device reliability. The effects of ultraviolet/ozone (UV/O 3 ) treatment of the GaN surface on the energy band bending of atomic-layer-deposition (ALD) Al 2 O 3 coated Ga-polar GaN were studied. The UV/O 3 treatment and post-ALD anneal can be used to effectively vary the band bending, the valence band offset, conduction band offset, and the interface dipole at the Al 2 O 3 /GaN interfaces. The UV/O 3 treatment increases the surface energy of the Ga-polar GaN, improves the uniformity of Al 2 O 3 deposition, and changes the amount of trapped charges in the ALD layer. The positively charged surface states formed by the UV/O 3 treatment-induced surface factors externally screen the effect of polarization charges in the GaN, in effect, determining the eventual energy band bending at the Al 2 O 3 /GaN interfaces. An optimal UV/O 3 treatment condition also exists for realizing the "best" interface conditions. The study of UV/O 3 treatment effect on the band alignments at the dielectric/III-nitride interfaces will be valuable for applications of transistors, light-emitting diodes, and photovoltaics.

Improve observation-based ground-level ozone spatial distribution by compositing satellite and surface observations: A simulation experiment

Science.gov (United States)

Zhang, Yuzhong; Wang, Yuhang; Crawford, James; Cheng, Ye; Li, Jianfeng

2018-05-01

Obtaining the full spatial coverage of daily surface ozone fields is challenging because of the sparsity of the surface monitoring network and the difficulty in direct satellite retrievals of surface ozone. We propose an indirect satellite retrieval framework to utilize the information from satellite-measured column densities of tropospheric NO2 and CH2O, which are sensitive to the lower troposphere, to derive surface ozone fields. The method is applicable to upcoming geostationary satellites with high-quality NO2 and CH2O measurements. To prove the concept, we conduct a simulation experiment using a 3-D chemical transport model for July 2011 over the eastern US. The results show that a second order regression using both NO2 and CH2O column densities can be an effective predictor for daily maximum 8-h average ozone. Furthermore, this indirect retrieval approach is shown to be complementary to spatial interpolation of surface observations, especially in regions where the surface sites are sparse. Combining column observations of NO2 and CH2O with surface site measurements leads to an improved representation of surface ozone over simple kriging, increasing the R2 value from 0.53 to 0.64 at a surface site distance of 252 km. The improvements are even more significant with larger surface site distances. The simulation experiment suggests that the indirect satellite retrieval technique can potentially be a useful tool to derive the full spatial coverage of daily surface ozone fields if satellite observation uncertainty is moderate.

Inhaled ozone (O3)-induces changes in serum metabolomic and liver transcriptomic profiles in rats

International Nuclear Information System (INIS)

Miller, Desinia B.; Karoly, Edward D.; Jones, Jan C.; Ward, William O.; Vallanat, Beena D.; Andrews, Debora L.; Schladweiler, Mette C.; Snow, Samantha J.; Bass, Virginia L.; Richards, Judy E.; Ghio, Andrew J.; Cascio, Wayne E.; Ledbetter, Allen D.; Kodavanti, Urmila P.

2015-01-01

Air pollution has been linked to increased incidence of diabetes. Recently, we showed that ozone (O 3 ) induces glucose intolerance, and increases serum leptin and epinephrine in Brown Norway rats. In this study, we hypothesized that O 3 exposure will cause systemic changes in metabolic homeostasis and that serum metabolomic and liver transcriptomic profiling will provide mechanistic insights. In the first experiment, male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or O 3 at 0.25, 0.50, or 1.0 ppm, 6 h/day for two days to establish concentration-related effects on glucose tolerance and lung injury. In a second experiment, rats were exposed to FA or 1.0 ppm O 3 , 6 h/day for either one or two consecutive days, and systemic metabolic responses were determined immediately after or 18 h post-exposure. O 3 increased serum glucose and leptin on day 1. Glucose intolerance persisted through two days of exposure but reversed 18 h-post second exposure. O 3 increased circulating metabolites of glycolysis, long-chain free fatty acids, branched-chain amino acids and cholesterol, while 1,5-anhydroglucitol, bile acids and metabolites of TCA cycle were decreased, indicating impaired glycemic control, proteolysis and lipolysis. Liver gene expression increased for markers of glycolysis, TCA cycle and gluconeogenesis, and decreased for markers of steroid and fat biosynthesis. Genes involved in apoptosis and mitochondrial function were also impacted by O 3 . In conclusion, short-term O 3 exposure induces global metabolic derangement involving glucose, lipid, and amino acid metabolism, typical of a stress–response. It remains to be examined if these alterations contribute to insulin resistance upon chronic exposure. - Highlights: • Ozone, an ubiquitous air pollutant induces acute systemic metabolic derangement. • Serum metabolomic approach provides novel insights in ozone-induced changes. • Ozone exposure induces leptinemia, hyperglycemia, and glucose intolerance

The effect of ozone on nicotine desorption from model surfaces:evidence for heterogeneous chemistry

Energy Technology Data Exchange (ETDEWEB)

Destaillats, Hugo; Singer, Brett C.; Lee, Sharon K.; Gundel, LaraA.

2005-05-01

Assessment of secondhand tobacco smoke exposure using nicotine as a tracer or biomarker is affected by sorption of the alkaloid to indoor surfaces and by its long-term re-emission into the gas phase. However, surface chemical interactions of nicotine have not been sufficiently characterized. Here, the reaction of ozone with nicotine sorbed to Teflon and cotton surfaces was investigated in an environmental chamber by monitoring nicotine desorption over a week following equilibration in dry or humid air (65-70 % RH). The Teflon and cotton surfaces had N{sub 2}-BET surface areas of 0.19 and 1.17 m{sup 2} g{sup -1}, and water mass uptakes (at 70 % RH) of 0 and 7.1 % respectively. Compared with dry air baseline levels in the absence of O{sub 3}, gas phase nicotine concentrations decrease, by 2 orders of magnitude for Teflon after 50 h at 20-45 ppb O{sub 3}, and by a factor of 10 for cotton after 100 h with 13-15 ppb O{sub 3}. The ratios of pseudo first-order rate constants for surface reaction (r) to long-term desorption (k) were r/k = 3.5 and 2.0 for Teflon and cotton surfaces, respectively. These results show that surface oxidation was competitive with desorption. Hence, oxidative losses could significantly reduce long-term re-emissions of nicotine from indoor surfaces. Formaldehyde, N-methylformamide, nicotinaldehyde and cotinine were identified as oxidation products, indicating that the pyrrolidinic N was the site of electrophilic attack by O{sub 3}. The presence of water vapor had no effect on the nicotine-O{sub 3} reaction on Teflon surfaces. By contrast, nicotine desorption from cotton in humid air was unaffected by the presence of ozone. These observations are consistent with complete inhibition of ozone-nicotine surface reactions in an aqueous surface film present in cotton but not in Teflon surfaces.

Nicotiana tabacum as model for ozone - plant surface reactions

Science.gov (United States)

Jud, Werner; Fischer, Lukas; Wohlfahrt, Georg; Tissier, Alain; Canaval, Eva; Hansel, Armin

2015-04-01

Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. The ensuing injuries have been related to the uptake of ozone through the stomatal pores and oxidative effects damaging the internal leaf tissue. A striking question of current research is the environment and plant specific partitioning of ozone loss between gas phase, stomatal or plant surface sink terms. Here we show results from ozone fumigation experiments using various Nicotiana Tabacum varieties, whose surfaces are covered with different amounts of unsaturated diterpenoids exuded by their glandular trichomes. Exposure to elevated ozone levels (50 to 150 ppbv) for 5 to 15 hours in an exceptionally clean cuvette system did neither result in a reduction of photosynthesis nor caused any visible leaf damage. Both these ozone induced stress effects have been observed previously in ozone fumigation experiments with the ozone sensitive tobacco line Bel-W3. In our case ozone fumigation was accompanied by a continuous release of oxygenated volatile organic compounds, which could be clearly associated to their condensed phase precursors for the first time. Gas phase reactions of ozone were avoided by choosing a high enough gas exchange rate of the plant cuvette system. In the case of the Ambalema variety, that is known to exude only the diterpenoid cis-abienol, ozone fumigation experiments yield the volatiles formaldehyde and methyl vinyl ketone (MVK). The latter could be unequivocally separated from isomeric methacrolein (MACR) by the aid of a Selective Reagent Ion Time-of-Flight Mass Spectrometer (SRI-ToF-MS), which was switched every six minutes from H3O+ to NO+ primary ion mode and vice versa. Consistent with the picture of an ozone protection mechanism caused by reactive diterpenoids at the leaf surface are the results from dark-light experiments. The ozone loss obtained from the

A simple UV-ozone surface treatment to enhance photocatalytic performance of TiO 2 loaded polymer nanofiber membranes

KAUST Repository

Dilpazir, S.

2016-01-29

Homogeneously dispersed titanium dioxide loaded polyacrylonitrile nanofiber membranes with increased active mass loading, Ti3+ surface defects and hydrophilicity were fabricated by combining electrospinning and UV-ozone surface treatment. The photocatalytic activity improved by a factor of ∼2 and the kinetics of photodegradation switched from pseudo-first order to pseudo-second order with increasing TiO2 content with a maximum rate constant of 20.7 h-1. © The Royal Society of Chemistry 2016.

Using satellite data to guide emission control strategies for surface ozone pollution

Science.gov (United States)

Jin, X.; Fiore, A. M.

2017-12-01

Surface ozone (O3) has adverse effects on public health, agriculture and ecosystems. As a secondary pollutant, ozone is not emitted directly. Ozone forms from two classes of precursors: NOx and VOCs. We use satellite observations of formaldehyde (a marker of VOCs) and NO2 (a marker of NOx) to identify areas which would benefit more from reducing NOx emissions (NOx-limited) versus areas where reducing VOC emissions would lead to lower ozone (VOC-limited). We use a global chemical transport model (GEOS-Chem) to develop a set of threshold values that separate the NOx-limited and VOC-limited conditions. Combining these threshold values with a decadal record of satellite observations, we find that U.S. cities (e.g. New York, Chicago) have shifted from VOC-limited to NOx-limited ozone production regimes in the warm season. This transition reflects the NOx emission controls implemented over the past decade. Increasing NOx sensitivity implies that regional NOx emission control programs will improve O3 air quality more now than it would have a decade ago.

Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

KAUST Repository

Kulkarni, Pavan S.

2016-09-24

Four distinct nocturnal surface ozone (NSO) enhancement events were observed, with NSO concentration exceeding 80μg/m3, at multiple ozone (O3) monitoring stations (32 sites) in January, November and December between year 2000–2010, in Portugal. The reasonable explanation for the observed bimodal pattern of surface ozone with enhanced NSO concentration during nighttime has to be transport processes, as the surface ozone production ceases at nighttime. Simultaneous measurements of O3 at multiple stations during the study period in Portugal suggest that horizontal advection alone cannot explain the observed NSO enhancement. Thus, detailed analysis of the atmospheric conditions, simulated with the Weather Research and Forecasting (WRF) model, were performed to evaluate the atmospheric mechanisms responsible for NSO enhancement in the region. Simulations revealed that each event occurred as a result of one or the combination of different atmospheric processes such as, passage of a cold front followed by a subsidence zone; passage of a moving surface trough, with associated strong horizontal wind speed and vertical shear; combination of vertical and horizontal transport at the synoptic scale; formation of a low level jet with associated vertical mixing below the jet stream. The study confirmed that large-scale flow pattern resulting in enhanced vertical mixing in the nocturnal boundary layer, plays a key role in the NSO enhancement events, which frequently occur over Portugal during winter months. © 2016 Elsevier Ltd

Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

KAUST Repository

Kulkarni, Pavan S.; Dasari, Hari Prasad; Sharma, Ashish; Bortoli, D.; Salgado, Rui; Silva, A.M.

2016-01-01

Four distinct nocturnal surface ozone (NSO) enhancement events were observed, with NSO concentration exceeding 80μg/m3, at multiple ozone (O3) monitoring stations (32 sites) in January, November and December between year 2000–2010, in Portugal. The reasonable explanation for the observed bimodal pattern of surface ozone with enhanced NSO concentration during nighttime has to be transport processes, as the surface ozone production ceases at nighttime. Simultaneous measurements of O3 at multiple stations during the study period in Portugal suggest that horizontal advection alone cannot explain the observed NSO enhancement. Thus, detailed analysis of the atmospheric conditions, simulated with the Weather Research and Forecasting (WRF) model, were performed to evaluate the atmospheric mechanisms responsible for NSO enhancement in the region. Simulations revealed that each event occurred as a result of one or the combination of different atmospheric processes such as, passage of a cold front followed by a subsidence zone; passage of a moving surface trough, with associated strong horizontal wind speed and vertical shear; combination of vertical and horizontal transport at the synoptic scale; formation of a low level jet with associated vertical mixing below the jet stream. The study confirmed that large-scale flow pattern resulting in enhanced vertical mixing in the nocturnal boundary layer, plays a key role in the NSO enhancement events, which frequently occur over Portugal during winter months. © 2016 Elsevier Ltd

Inhaled ozone (O{sub 3})-induces changes in serum metabolomic and liver transcriptomic profiles in rats

Energy Technology Data Exchange (ETDEWEB)

Miller, Desinia B. [Curriculum in Toxicology, University of North Carolina-Chapel Hill, Chapel Hill, NC (United States); Karoly, Edward D.; Jones, Jan C. [Metabolon Incorporation, Durham, NC (United States); Ward, William O.; Vallanat, Beena D.; Andrews, Debora L. [Research Cores Unit, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC (United States); Schladweiler, Mette C.; Snow, Samantha J. [Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC (United States); Bass, Virginia L. [Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC (United States); Richards, Judy E.; Ghio, Andrew J.; Cascio, Wayne E.; Ledbetter, Allen D. [Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC (United States); Kodavanti, Urmila P., E-mail: kodavanti.urmila@epa.gov [Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC (United States)

2015-07-15

Air pollution has been linked to increased incidence of diabetes. Recently, we showed that ozone (O{sub 3}) induces glucose intolerance, and increases serum leptin and epinephrine in Brown Norway rats. In this study, we hypothesized that O{sub 3} exposure will cause systemic changes in metabolic homeostasis and that serum metabolomic and liver transcriptomic profiling will provide mechanistic insights. In the first experiment, male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or O{sub 3} at 0.25, 0.50, or 1.0 ppm, 6 h/day for two days to establish concentration-related effects on glucose tolerance and lung injury. In a second experiment, rats were exposed to FA or 1.0 ppm O{sub 3}, 6 h/day for either one or two consecutive days, and systemic metabolic responses were determined immediately after or 18 h post-exposure. O{sub 3} increased serum glucose and leptin on day 1. Glucose intolerance persisted through two days of exposure but reversed 18 h-post second exposure. O{sub 3} increased circulating metabolites of glycolysis, long-chain free fatty acids, branched-chain amino acids and cholesterol, while 1,5-anhydroglucitol, bile acids and metabolites of TCA cycle were decreased, indicating impaired glycemic control, proteolysis and lipolysis. Liver gene expression increased for markers of glycolysis, TCA cycle and gluconeogenesis, and decreased for markers of steroid and fat biosynthesis. Genes involved in apoptosis and mitochondrial function were also impacted by O{sub 3}. In conclusion, short-term O{sub 3} exposure induces global metabolic derangement involving glucose, lipid, and amino acid metabolism, typical of a stress–response. It remains to be examined if these alterations contribute to insulin resistance upon chronic exposure. - Highlights: • Ozone, an ubiquitous air pollutant induces acute systemic metabolic derangement. • Serum metabolomic approach provides novel insights in ozone-induced changes. • Ozone exposure induces leptinemia

Variations of surface ozone concentration across the Klang Valley, Malaysia

Science.gov (United States)

Latif, Mohd Talib; Huey, Lim Shun; Juneng, Liew

2012-12-01

Hourly air quality data covering the period 2004-2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August. Analysis of daily variations in surface O3 and the precursors - NO, NO2, CO, NMHC and UVb, indicate that the surface O3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NOx, particularly through tritration processes. Although results from our study suggested that NMHCs may influence the maximum O3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O3 around the Klang Valley. HYSPLIT back trajectories (-72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O3 in the study area. Results show that 47% of the high O3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast.

OZONE PRECURSORS, SOURCE REGIONS, AND O(3) FORMATION DURING THE TEXAQS 2000 STUDY

International Nuclear Information System (INIS)

DAUM, P.H.; KLEINMAN, L.I.; BRECHTEL, F.; LEE, Y.N.; NUNNERMACKER, L.J.; SPRINGSTON, S.R.; WEINSTEIN-LLOYD, J.

2001-01-01

The DOE G-1 aircraft made flights on 14 days during the TexAQS 2000 study. On 7 of those days, the aircraft encountered highly localized plumes exhibiting O(sub 3) concentrations in excess of 150 ppb; on some days, peak O(sub 3) concentrations were in excess of 200 ppb. These ozone plumes were rapidly formed with an efficiency (O(sub 3) per NO(sub x) molecule consumed) much higher (7-20) than observed in other urban areas (3-4), and were frequently associated with high concentrations ( and gt;20 ppb) of secondary hydrocarbon species such as formaldehyde. Back trajectory analysis showed that the plumes were invariably associated with emissions from one or more of the large industrial complexes clustered about the Houston Ship Channel and Galveston Bay. Very high hydrocarbon reactivities were found in the vicinity of these facilities during morning flights. These hydrocarbon reactivities, in combination with local NO(sub x) emissions, were large enough to support instantaneous O(sub 3) production rates as high as 200 ppb/h. It is hypothesized that the combination of nitrogen oxides and hydrocarbon emissions emanating from this complex of industries provided a potent mixture of chemicals that caused the rapid formation of very high concentrations of ozone which, depending on the prevailing meteorology, could cause exceedance of the NAAQS ozone standard anywhere in the Houston metropolitan area

Significant increase of surface ozone at a rural site, north of eastern China

Directory of Open Access Journals (Sweden)

Z. Ma

2016-03-01

Full Text Available Ozone pollution in eastern China has become one of the top environmental issues. Quantifying the temporal trend of surface ozone helps to assess the impacts of the anthropogenic precursor reductions and the likely effects of emission control strategies implemented. In this paper, ozone data collected at the Shangdianzi (SDZ regional atmospheric background station from 2003 to 2015 are presented and analyzed to obtain the variation in the trend of surface ozone in the most polluted region of China, north of eastern China or the North China Plain. A modified Kolmogorov–Zurbenko (KZ filter method was performed on the maximum daily average 8 h (MDA8 concentrations of ozone to separate the contributions of different factors from the variation of surface ozone and remove the influence of meteorological fluctuations on surface ozone. Results reveal that the short-term, seasonal and long-term components of ozone account for 36.4, 57.6 and 2.2 % of the total variance, respectively. The long-term trend indicates that the MDA8 has undergone a significant increase in the period of 2003–2015, with an average rate of 1.13 ± 0.01 ppb year−1 (R2 = 0.92. It is found that meteorological factors did not significantly influence the long-term variation of ozone and the increase may be completely attributed to changes in emissions. Furthermore, there is no significant correlation between the long-term O3 and NO2 trends. This study suggests that emission changes in VOCs might have played a more important role in the observed increase of surface ozone at SDZ.

Evaluation of The Surface Ozone Concentrations In Greater Cairo Area With Emphasis On Helwan, Egypt

International Nuclear Information System (INIS)

Ramadan, A.; Kandil, A.T.; Abd Elmaged, S.M.; Mubarak, I.

2011-01-01

Various biogenic and anthropogenic sources emit huge quantities of surface ozone. The main purpose of this study is to evaluate the surface ozone levels present at Helwan area in order to improve the knowledge and understanding troposphere processes. Surface Ozone has been measured at 2 sites at Helwan; these sites cover the most populated area in Helwan. Ozone concentration is continuously monitored by UV absorption photometry using the equipment O 3 41 M UV Photometric Ozone Analyzer. The daily maximum values of the ozone concentration in the greater Cairo area have approached but did not exceeded the critical levels during the year 2008. Higher ozone concentrations at Helwan are mainly due to the transport of ozone from regions further to the north of greater Cairo and to a lesser extent of ozone locally generated by photochemical smog process. The summer season has the largest diurnal variation, with the tendency of the daily ozone maxima occur in the late afternoon. The night time concentration of ozone was significantly higher at Helwan because there are no fast acting sinks, destroying ozone since the average night time concentration of ozone is maintained at 40 ppb at the site. No correlation between the diurnal total suspended particulate (TSP) matter and the diurnal cumulative ozone concentration was observed during the Khamasin period

Ozone production in the reaction of T2 and O2 gas: A comparison of experimental results and model predictions

International Nuclear Information System (INIS)

Failor, R.A.; Souers, P.C.; Magnotta, F.

1992-01-01

Ozone, predicted to be an important intermediate species in T 2 oxidation, was monitored in situ by UV absorption spectroscopy for 0.01-1.0 mol % T 2 in O 2 (1 atm, 298 K). These are the first measurements of a tritium oxidation reaction intermediate. The experimental results were compared with the predictions of the author's comprehensive model of tritium oxidation. The experimentally determined temporal variation in ozone concentration is qualitatively reproduced by the model. As predicted, the measured initial rate of ozone production varied linearly with the initial T 2 concentration ([T 2 ] o ), but with a value one-third of that predicted. The steady-state ozone concentration ([O 3 ] ss ) a factor of 4 larger than predicted for a 1.0% T 2 -O 2 mixture. Addition of H 2 to the T 2 O 2 mixture, to differentiate between the radiolytic and chemical behavior of the tritium, produced a decrease in [O 3 ] ss which was larger than predicted. Changing the reaction cell surface-to-volume ratio showed indications of minor surface removal of ozone. No reasonable variation in model input parameters brought both the predicted initial ozone production rates and steady-state concentrations of ozone into agreement with the experimental results. Though qualitative agreement was achieved, further studies, with emphasis on surface effects, are necessary to explain quantitative differences and gain a greater understanding of the oxidation mechanism. 27 refs., 11 figs., 4 tabs

Future heat waves and surface ozone

Science.gov (United States)

Meehl, Gerald A.; Tebaldi, Claudia; Tilmes, Simone; Lamarque, Jean-Francois; Bates, Susan; Pendergrass, Angeline; Lombardozzi, Danica

2018-06-01

A global Earth system model is used to study the relationship between heat waves and surface ozone levels over land areas around the world that could experience either large decreases or little change in future ozone precursor emissions. The model is driven by emissions of greenhouse gases and ozone precursors from a medium-high emission scenario (Representative Concentration Pathway 6.0–RCP6.0) and is compared to an experiment with anthropogenic ozone precursor emissions fixed at 2005 levels. With ongoing increases in greenhouse gases and corresponding increases in average temperature in both experiments, heat waves are projected to become more intense over most global land areas (greater maximum temperatures during heat waves). However, surface ozone concentrations on future heat wave days decrease proportionately more than on non-heat wave days in areas where ozone precursors are prescribed to decrease in RCP6.0 (e.g. most of North America and Europe), while surface ozone concentrations in heat waves increase in areas where ozone precursors either increase or have little change (e.g. central Asia, the Mideast, northern Africa). In the stabilized ozone precursor experiment, surface ozone concentrations increase on future heat wave days compared to non-heat wave days in most regions except in areas where there is ozone suppression that contributes to decreases in ozone in future heat waves. This is likely associated with effects of changes in isoprene emissions at high temperatures (e.g. west coast and southeastern North America, eastern Europe).

Characteristics of surface ozone in Agra, a sub-urban site in Indo ...

Indian Academy of Sciences (India)

Nidhi Verma

2018-04-09

Apr 9, 2018 ... In the present study, measurements of surface ozone (O3) and its precursors (NO and NO2) were carried out at a ...... from road traffic in Great Britain; Atmos. Environ. 54 ... L, Doddridge B G and Holben B N 1997 The impact of.

Experimental study of surface dielectric barrier discharge in air and its ozone production

International Nuclear Information System (INIS)

Pekárek, Stanislav

2012-01-01

For surface dielectric barrier discharge in air we studied the effects of frequency of the driving voltage on dissipated power, asymmetry of amplitudes of the discharge voltage, discharge UV emission, ozone production, ozone production of the discharge with TiO 2 and of the discharge in magnetic field. We found that for a particular voltage the dissipated power is higher for the frequency of the driving voltage of 26.3 kHz than for the frequency of 10.9 kHz; peak values of the positive half-periods of the discharge voltage are higher than peak values of the negative half-periods; intensity of the discharge UV emissions for wavelengths of 320-420 nm is for both frequencies a linear function of power; maximum ozone concentration for the frequency of the driving voltage of 26.3 kHz is obtained with smaller power than for the frequency of 10.9 kHz; placement of TiO 2 particles into the discharge chamber increases for both frequencies of the driving voltage maximum ozone concentration produced by the discharge and for the frequency of the driving voltage of 26.3 kHz increases ozone production yield. Finally, there is no observable effect of magnetic field on concentration of ozone produced by the discharge as well as on production yield. (paper)

Health burdens of surface ozone in the UK for a range of future scenarios

OpenAIRE

Heal, Mathew R.; Heaviside, Clare; Doherty, Ruth M.; Vieno, Massimo; Stevenson, David S.; Vardoulakis, Sotiris

2013-01-01

Exposure to surface ozone (O3), which is influenced by emissions of precursor chemical species, meteorology and population distribution, is associated with excess mortality and respiratory morbidity. In this study, the EMEP-WRF atmospheric chemistry transport model was used to simulate surface O3 concentrations at 5 km horizontal resolution over the British Isles for a baseline year of 2003, for three anthropogenic emissions scenarios for 2030, and for a + 5 °C increase in air temperature on ...

Effects of UV-Ozone Treatment on Sensing Behaviours of EGFETs with Al2O3 Sensing Film

Directory of Open Access Journals (Sweden)

Cuiling Sun

2017-12-01

Full Text Available The effects of UV-ozone (UVO treatment on the sensing behaviours of extended-gate field-effect transistors (EGFETs that use Al2O3 as the sensing film have been investigated. The Al2O3 sensing films are UVO-treated with various duration times and the corresponding EGFET sensing behaviours, such as sensitivity, hysteresis, and long-term stability, are electrically evaluated under various measurement conditions. Physical analysis is also performed to characterize the surface conditions of the UVO-treated sensing films using X-ray photoelectron spectroscopy and atomic force microscopy. It is found that UVO treatment effectively reduces the buried sites in the Al2O3 sensing film and subsequently results in reduced hysteresis and improved long-term stability of EGFET. Meanwhile, the observed slightly smoother Al2O3 film surface post UVO treatment corresponds to decreased surface sites and slightly reduced pH sensitivity of the Al2O3 film. The sensitivity degradation is found to be monotonically correlated with the UVO treatment time. A treatment time of 10 min is found to yield an excellent performance trade-off: clearly improved long-term stability and reduced hysteresis at the cost of negligible sensitivity reduction. These results suggest that UVO treatment is a simple and facile method to improve the overall sensing performance of the EGFETs with an Al2O3 sensing film.

SPIROMETRIC RESPONSE TO OZONE (O3) IN YOUNG ADULTS AS A FUNCTION OF BODY MAASS INDEX (BMI)

Science.gov (United States)

Recent studies in murine models of obesity have shown enhanced responsiveness to ozone in obese vs. lean mice. To assess whether previous human ozone exposure data from our laboratory support an effect of BMI on the spirometric response to ozone we analyzed the post-O3 percent de...

Plasmachemical and heterogeneous processes in ozonizers with oxygen activation by a dielectric barrier discharge

Energy Technology Data Exchange (ETDEWEB)

Mankelevich, Yu. A., E-mail: ymankelevich@mics.msu.su; Voronina, E. N.; Poroykov, A. Yu.; Rakhimov, T. V.; Voloshin, D. G.; Chukalovsky, A. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

2016-10-15

Plasmachemical and heterogeneous processes of generation and loss of ozone in the atmosphericpressure dielectric barrier discharge in oxygen are studied theoretically. Plasmachemical and electronic kinetics in the stage of development and decay of a single plasma filament (microdischarge) are calculated numerically with and without allowance for the effects of ozone vibrational excitation and high initial ozone concentration. The developed analytical approach is applied to determine the output ozone concentration taking into account ozone heterogeneous losses on the Al{sub 2}O{sub 3} dielectric surface. Using the results of quantummechanical calculations by the method of density functional theory, a multistage catalytic mechanism of heterogeneous ozone loss based on the initial passivation of a pure Al{sub 2}O{sub 3} surface by ozone and the subsequent interaction of O{sub 3} molecules with the passivated surface is proposed. It is shown that the conversion reaction 2O{sub 3} → 3O{sub 2} of a gas-phase ozone molecule with a physically adsorbed ozone molecule can result in the saturation of the maximum achievable ozone concentration at high specific energy depositions, the nonstationarity of the output ozone concentration, and its dependence on the prehistory of ozonizer operation.

What is Eating Ozone? Thermal Reactions between SO2 And O3: Implications for Icy Environments

Science.gov (United States)

Loeffler, Mark J.; Hudson, Reggie L.

2016-01-01

Laboratory studies are presented, showing for the first time that thermally driven reactions in solid H2O+SO2+O3 mixtures can occur below 150 K, with the main sulfur-containing product being bisulfate (HSO4(-)). Using a technique not previously applied to the low-temperature kinetics of either interstellar or solar system ice analogs, we estimate an activation energy of 32 kJ per mol for HSO4(-) formation. These results show that at the temperatures of the Jovian satellites, SO2 and O3 will efficiently react making detection of these molecules in the same vicinity unlikely. Our results also explain why O3 has not been detected on Callisto and why the SO2 concentration on Callisto appears to be highest on that world's leading hemisphere. Furthermore, our results predict that the SO2 concentration on Ganymede will be lowest in the trailing hemisphere, where the concentration of O3 is the highest. Our work suggests that thermal reactions in ices play a much more important role in surface and sub-surface chemistry than generally appreciated, possibly explaining the low abundance of sulfur-containing molecules and the lack of ozone observed in comets and interstellar ices.

Responses of Surface Ozone Air Quality to Anthropogenic Nitrogen Deposition

Science.gov (United States)

Zhang, L.; Zhao, Y.; Tai, A. P. K.; Chen, Y.; Pan, Y.

2017-12-01

Human activities have substantially increased atmospheric deposition of reactive nitrogen to the Earth's surface, inducing unintentional effects on ecosystems with complex environmental and climate consequences. One consequence remaining unexplored is how surface air quality might respond to the enhanced nitrogen deposition through surface-atmosphere exchange. We combine a chemical transport model (GEOS-Chem) and a global land model (Community Land Model) to address this issue with a focus on ozone pollution in the Northern Hemisphere. We consider three processes that are important for surface ozone and can be perturbed by addition of atmospheric deposited nitrogen: emissions of biogenic volatile organic compounds (VOCs), ozone dry deposition, and soil nitrogen oxide (NOx) emissions. We find that present-day anthropogenic nitrogen deposition (65 Tg N a-1 to the land), through enhancing plant growth (represented as increases in vegetation leaf area index (LAI) in the model), could increase surface ozone from increased biogenic VOC emissions, but could also decrease ozone due to higher ozone dry deposition velocities. Meanwhile, deposited anthropogenic nitrogen to soil enhances soil NOx emissions. The overall effect on summer mean surface ozone concentrations show general increases over the globe (up to 1.5-2.3 ppbv over the western US and South Asia), except for some regions with high anthropogenic NOx emissions (0.5-1.0 ppbv decreases over the eastern US, Western Europe, and North China). We compare the surface ozone changes with those driven by the past 20-year climate and historical land use changes. We find that the impacts from anthropogenic nitrogen deposition can be comparable to the climate and land use driven surface ozone changes at regional scales, and partly offset the surface ozone reductions due to land use changes reported in previous studies. Our study emphasizes the complexity of biosphere-atmosphere interactions, which can have important

Sex differences in diet and inhaled ozone (O3) induced metabolic impairment

Science.gov (United States)

APS 2015 abstract Sex differences in diet and inhaled ozone (O3) induced metabolic impairment U.P. Kodavanti1, V.L. Bass2, M.C. Schladweiler1, C.J. Gordon3, K.A. Jarema1, P. Phillips1, A.D. Ledbetter1, D.B. Miller4, S. Snow5, J.E. Richards1. 1 EPHD, NHEERL, USEPA, Research Triang...

Investigating ozone-induced decomposition of surface-bound permethrin for conditions in aircraft cabins.

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Coleman, B K; Wells, J R; Nazaroff, W W

2010-02-01

The reaction of ozone with permethrin can potentially form phosgene. Published evidence on ozone levels and permethrin surface concentrations in aircraft cabins indicated that significant phosgene formation might occur in this setting. A derivatization technique was developed to detect phosgene with a lower limit of detection of 2 ppb. Chamber experiments were conducted with permethrin-coated materials (glass, carpet, seat fabric, and plastic) exposed to ozone under cabin-relevant conditions (150 ppb O(3), 4.5/h air exchange rate, means of material-balance modeling indicates that the upper limit on the phosgene level in aircraft cabins resulting from this chemistry is approximately 1 microg/m(3) or approximately 0.3 ppb. It was thus determined that phosgene formation, if it occurs in aircraft cabins, is not likely to exceed relevant, health-based phosgene exposure guidelines. Phosgene formation from ozone-initiated oxidation of permethrin in the aircraft cabin environment, if it occurs, is estimated to generate levels below the California Office of Environmental Health Hazard Assessment acute reference exposure level of 4 microg/m(3) or approximately 1 ppb.

Solar photolysis of ozone to singlet D oxygen atoms, O(1D)

International Nuclear Information System (INIS)

Blackburn, T.E.

1984-01-01

Ground level solar photolysis rate coefficients (jO 3 ) were measured for the photolysis of ozone by sunlight, (O 3 + hnu( 2 + O( 1 D)). The O( 1 D) atoms produced react with nitrous oxide (N 2 O) carrier gas to form higher oxides of nitrogen (NOx). Computer model predictions show that these are mainly N 2 O 5 and NO 3 . Seventy five days of data were taken during the summer of 1983, at Ann Arbor, Michigan, and are presented in the appendix. Over 390 clear air jO 3 values are correlated with effective ozone column densities, and 500 nm aerosol optical depths. The solar direct beam component of ozone photolysis was measured for the different aerosol optical depths, over two entire days from sun-up to sun-down. Temperature dependence of jO 3 was measured from 10 0 C to 39 0 C with good agreement to models. Comparison of jO 3 versus global and ultraviolet radiation are made under various ozone column densities and aerosol optical depths. A jO 3 -photometer was built using an interference filter to pass only ozone photolyzing light. Improvements to instrumental parts are shown for balloon and aircraft flyable payloads

Ozone adsorption on carbon nanoparticles

Science.gov (United States)

Chassard, Guillaume; Gosselin, Sylvie; Visez, Nicolas; Petitprez, Denis

2014-05-01

Carbonaceous particles produced by incomplete combustion or thermal decomposition of hydrocarbons are ubiquitous in the atmosphere. On these particles are adsorbed hundreds of chemical species. Those of great concern to health are polycyclic aromatic hydrocarbons (PAHs). During atmospheric transport, particulate PAHs react with gaseous oxidants. The induced chemical transformations may change toxicity and hygroscopicity of these potentially inhalable particles. The interaction between ozone and carbon particles has been extensively investigated in literature. However ozone adsorption and surface reaction mechanisms are still ambiguous. Some studies described a fast catalytic decomposition of ozone initiated by an atomic oxygen chemisorption followed by a molecular oxygen release [1-3]. Others suggested a reversible ozone adsorption according to Langmuir-type behaviour [4,5]. The aim of this present study is a better understanding of ozone interaction with carbon surfaces. An aerosol of carbon nanoparticles was generated by flowing synthetic air in a glass tube containing pure carbon (primary particles studied. Accordingly to literature, it has been observed that the number of gas-phase ozone molecules lost per unit particle surface area tends towards a plateau for high ozone concentration suggesting a reversible ozone adsorption according to a Langmuir mechanism. We calculated the initial reaction probability between O3 and carbon particles.An initial uptake coefficient of 1.10-4 was obtained. Similar experiments were realized by selecting the particles size with a differential mobility analyser. We observed a strong size-dependent increase in reactivity with the decrease of particles size. This result is relevant for the health issues. Indeed the smallest particles are most likely to penetrate deep into the lungs. Competitive reactions between ozone and other species like H2O or atomic oxygen were also considered. Oxygen atoms were generated by photolysis of O3

Impacts of urban land-surface forcing on ozone air quality in the Seoul metropolitan area

Directory of Open Access Journals (Sweden)

Y.-H. Ryu

2013-02-01

Full Text Available Modified local meteorology owing to heterogeneities in the urban–rural surface can affect urban air quality. In this study, the impacts of urban land-surface forcing on ozone air quality during a high ozone (O₃ episode in the Seoul metropolitan area, South Korea, are investigated using a high-resolution chemical transport model (CMAQ. Under fair weather conditions, the temperature excess (urban heat island significantly modifies boundary layer characteristics/structures and local circulations. The modified boundary layer and local circulations result in an increase in O₃ levels in the urban area of 16 ppb in the nighttime and 13 ppb in the daytime. Enhanced turbulence in the deep urban boundary layer dilutes pollutants such as NO_x, and this contributes to the elevated O₃ levels through the reduced O₃ destruction by NO in the NO_x-rich environment. The advection of O₃ precursors over the mountains near Seoul by the prevailing valley-breeze circulation in the mid- to late morning results in the build-up of O₃ over the mountains in conjunction with biogenic volatile organic compound (BVOC emissions there. As the prevailing local circulation in the afternoon changes to urban-breeze circulation, the O₃-rich air masses over the mountains are advected over the urban area. The urban-breeze circulation exerts significant influences on not only the advection of O₃ but also the chemical production of O₃ under the circumstances in which both anthropogenic and biogenic (natural emissions play important roles in O₃ formation. As the air masses that are characterized by low NO_x and high BVOC levels and long OH chain length are advected over the urban area from the surroundings, the ozone production efficiency increases in the urban area. The relatively strong vertical mixing in the urban boundary layer embedded in the

Potential energy surface, dipole moment surface and the intensity calculations for the 10 μm, 5 μm and 3 μm bands of ozone

Science.gov (United States)

Polyansky, Oleg L.; Zobov, Nikolai F.; Mizus, Irina I.; Kyuberis, Aleksandra A.; Lodi, Lorenzo; Tennyson, Jonathan

2018-05-01

Monitoring ozone concentrations in the Earth's atmosphere using spectroscopic methods is a major activity which undertaken both from the ground and from space. However there are long-running issues of consistency between measurements made at infrared (IR) and ultraviolet (UV) wavelengths. In addition, key O3 IR bands at 10 μm, 5 μm and 3 μm also yield results which differ by a few percent when used for retrievals. These problems stem from the underlying laboratory measurements of the line intensities. Here we use quantum chemical techniques, first principles electronic structure and variational nuclear-motion calculations, to address this problem. A new high-accuracy ab initio dipole moment surface (DMS) is computed. Several spectroscopically-determined potential energy surfaces (PESs) are constructed by fitting to empirical energy levels in the region below 7000 cm-1 starting from an ab initio PES. Nuclear motion calculations using these new surfaces allow the unambiguous determination of the intensities of 10 μm band transitions, and the computation of the intensities of 10 μm and 5 μm bands within their experimental error. A decrease in intensities within the 3 μm is predicted which appears consistent with atmospheric retrievals. The PES and DMS form a suitable starting point both for the computation of comprehensive ozone line lists and for future calculations of electronic transition intensities.

Synergistic Effect of Copper and Cobalt in Cu-Co-O Composite Nanocatalyst for Catalytic Ozonation

International Nuclear Information System (INIS)

Dong, Yuming; Wu, Lina; Wang, Guangli; Zhao, Hui; Jiang, Pingping; Feng, Cuiyun

2013-01-01

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state

Effects of conventional ozonation and electro-peroxone pretreatment of surface water on disinfection by-product formation during subsequent chlorination.

Science.gov (United States)

Mao, Yuqin; Guo, Di; Yao, Weikun; Wang, Xiaomao; Yang, Hongwei; Xie, Yuefeng F; Komarneni, Sridhar; Yu, Gang; Wang, Yujue

2018-03-01

The electro-peroxone (E-peroxone) process is an emerging ozone-based electrochemical advanced oxidation process that combines conventional ozonation with in-situ cathodic hydrogen peroxide (H 2 O 2 ) production for oxidative water treatment. In this study, the effects of the E-peroxone pretreatment on disinfection by-product (DBP) formation from chlorination of a synthetic surface water were investigated and compared to conventional ozonation. Results show that due to the enhanced transformation of ozone (O 3 ) to hydroxyl radicals (OH) by electro-generated H 2 O 2 , the E-peroxone process considerably enhanced dissolved organic carbon (DOC) abatement and significantly reduced bromate (BrO 3 - ) formation compared to conventional ozonation. However, natural organic matter (NOM) with high UV 254 absorbance, which is the major precursors of chlorination DBPs, was less efficiently abated during the E-peroxone process than conventional ozonation. Consequently, while both conventional ozonation and the E-peroxone process substantially reduced the formation of DBPs (trihalomethanes and haloacetic acids) during post-chlorination, higher DBP concentrations were generally observed during chlorination of the E-peroxone pretreated waters than conventional ozonation treated. In addition, because of conventional ozonation or the E-peroxone treatment, DBPs formed during post-chlorination shifted to more brominated species. The overall yields of brominated DBPs exhibited strong correlations with the bromide concentrations in water. Therefore, while the E-peroxone process can effectively suppress bromide transformation to bromate, it may lead to higher formation of brominated DBPs during post-chlorination compared to conventional ozonation. These results suggest that the E-peroxone process can lead to different DBP formation and speciation during water treatment trains compared to conventional ozonation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Response of the global surface ozone distribution to Northern Hemisphere sea surface temperature changes: implications for long-range transport

Science.gov (United States)

Yi, Kan; Liu, Junfeng; Ban-Weiss, George; Zhang, Jiachen; Tao, Wei; Cheng, Yanli; Tao, Shu

2017-07-01

The response of surface ozone (O3) concentrations to basin-scale warming and cooling of Northern Hemisphere oceans is investigated using the Community Earth System Model (CESM). Idealized, spatially uniform sea surface temperature (SST) anomalies of ±1 °C are individually superimposed onto the North Pacific, North Atlantic, and North Indian oceans. Our simulations suggest large seasonal and regional variability in surface O3 in response to SST anomalies, especially in the boreal summer. The responses of surface O3 associated with basin-scale SST warming and cooling have similar magnitude but are opposite in sign. Increasing the SST by 1 °C in one of the oceans generally decreases the surface O3 concentrations from 1 to 5 ppbv. With fixed emissions, SST increases in a specific ocean basin in the Northern Hemisphere tend to increase the summertime surface O3 concentrations over upwind regions, accompanied by a widespread reduction over downwind continents. We implement the integrated process rate (IPR) analysis in CESM and find that meteorological O3 transport in response to SST changes is the key process causing surface O3 perturbations in most cases. During the boreal summer, basin-scale SST warming facilitates the vertical transport of O3 to the surface over upwind regions while significantly reducing the vertical transport over downwind continents. This process, as confirmed by tagged CO-like tracers, indicates a considerable suppression of intercontinental O3 transport due to increased tropospheric stability at lower midlatitudes induced by SST changes. Conversely, the responses of chemical O3 production to regional SST warming can exert positive effects on surface O3 levels over highly polluted continents, except South Asia, where intensified cloud loading in response to North Indian SST warming depresses both the surface air temperature and solar radiation, and thus photochemical O3 production. Our findings indicate a robust linkage between basin-scale SST

Response of the global surface ozone distribution to Northern Hemisphere sea surface temperature changes: implications for long-range transport

Directory of Open Access Journals (Sweden)

K. Yi

2017-07-01

Full Text Available The response of surface ozone (O3 concentrations to basin-scale warming and cooling of Northern Hemisphere oceans is investigated using the Community Earth System Model (CESM. Idealized, spatially uniform sea surface temperature (SST anomalies of ±1 °C are individually superimposed onto the North Pacific, North Atlantic, and North Indian oceans. Our simulations suggest large seasonal and regional variability in surface O3 in response to SST anomalies, especially in the boreal summer. The responses of surface O3 associated with basin-scale SST warming and cooling have similar magnitude but are opposite in sign. Increasing the SST by 1 °C in one of the oceans generally decreases the surface O3 concentrations from 1 to 5 ppbv. With fixed emissions, SST increases in a specific ocean basin in the Northern Hemisphere tend to increase the summertime surface O3 concentrations over upwind regions, accompanied by a widespread reduction over downwind continents. We implement the integrated process rate (IPR analysis in CESM and find that meteorological O3 transport in response to SST changes is the key process causing surface O3 perturbations in most cases. During the boreal summer, basin-scale SST warming facilitates the vertical transport of O3 to the surface over upwind regions while significantly reducing the vertical transport over downwind continents. This process, as confirmed by tagged CO-like tracers, indicates a considerable suppression of intercontinental O3 transport due to increased tropospheric stability at lower midlatitudes induced by SST changes. Conversely, the responses of chemical O3 production to regional SST warming can exert positive effects on surface O3 levels over highly polluted continents, except South Asia, where intensified cloud loading in response to North Indian SST warming depresses both the surface air temperature and solar radiation, and thus photochemical O3 production. Our findings indicate a robust linkage

Productions of Volatile Organic Compounds (VOCs) in Surface Waters from Reactions with Atmospheric Ozone

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Hopkins, Frances; Bell, Thomas; Yang, Mingxi

2017-04-01

Ozone (O3) is a key atmospheric oxidant, greenhouse gas and air pollutant. In marine environments, some atmospheric ozone is lost by reactions with aqueous compounds (e.g. dissolved organic material, DOM, dimethyl sulfide, DMS, and iodide) near the sea surface. These reactions also lead to formations of volatile organic compounds (VOCs). Removal of O3 by the ocean remains a large uncertainty in global and regional chemical transport models, hampering coastal air quality forecasts. To better understand the role of the ocean in controlling O3 concentrations in the coastal marine atmosphere, we designed and implemented a series of laboratory experiments whereby ambient surface seawater was bubbled with O3-enriched, VOC-free air in a custom-made glass bubble equilibration system. Gas phase concentrations of a range of VOCs were monitored continuously over the mass range m/z 33 - 137 at the outflow of the bubble equilibrator by a proton transfer reaction - mass spectrometer (PTR-MS). Gas phase O3 was also measured at the input and output of the equilibrator to monitor the uptake due to reactions with dissolved compounds in seawater. We observed consistent productions of a variety of VOCs upon reaction with O3, notably isoprene, aldehydes, and ketones. Aqueous DMS is rapidly removed from the reactions with O3. To test the importance of dissolved organic matter precursors, we added increasing (milliliter) volumes of Emiliania huxleyi culture to the equilibrator filled with aged seawater, and observed significant linear increases in gas phase concentrations of a number of VOCs. Reactions between DOM and O3 at the sea-air interface represent a potentially significant source of VOCs in marine air and a sink of atmospheric O3.

Ozone Transport Aloft Drives Surface Ozone Maxima Across the Mojave Desert

Science.gov (United States)

VanCuren, R. A.

2014-12-01

A persistent layer of polluted air in the lower free troposphere over the Mojave Desert (California and Nevada) drives spring and summer surface ozone maxima as deep afternoon mixing delivers ozone and ozone precursors to surface measurement sites 200 km or more downwind of the mountains that separate the deserts from the heavily populated coastal areas of California. Pollutants in this elevated layer derive from California source regions (the Los Angeles megacity region and the intensive agricultural region of the San Joaquin Valley), and from long-range transport from Asia. Recognition of this poorly studied persistent layer explains and expands the significance of previously published reports of ozone and other pollutants observed in and over the Mojave Desert, resolves an apparent paradox in the timing of ozone peaks due to transport from the upwind basins, and provides a new perspective on the long-range downwind impacts of megacity pollution plumes.

Synthesis of Co3O4 nanosheets via electrodeposition followed by ozone treatment and their application to high-performance supercapacitors

Science.gov (United States)

Kung, Chung-Wei; Chen, Hsin-Wei; Lin, Chia-Yu; Vittal, R.; Ho, Kuo-Chuan

2012-09-01

A thin film of Co3O4 nanosheets is electrodeposited on a flexible Ti substrate by a one-step potentiostatic method, followed by an UV-ozone treatment for 30 min. The films before and after the UV-ozone treatment are characterized with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The film is composed of Co(OH)2 before UV-ozone treatment, and of Co3O4 after the treatment. The morphologies of both films are examined by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The obtained films are composed of nanosheets, and there is no change in their sheet-like morphology before and after the UV-ozone treatment. When applied for a supercapacitor, the Co3O4 modified Ti electrode (Co3O4/Ti) shows a far higher capacitance than that of the Co(OH)2 modified Ti electrode. The electrodeposition time and NaOH concentration in the electrolyte are optimized. A remarkably high specific capacitance of 1033.3 F g-1 is obtained for the Co3O4 thin film at a charge-discharge current density of 2.5 A g-1. The long-term stability data shows that there is still 77% of specific capacitance remaining after 3000 repeated charge-discharge cycles. The high specific capacitance and long-term stability suggest the potential use of Co3O4/Ti for making a flexible supercapacitor.

Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce (Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

International Nuclear Information System (INIS)

Percy, Kevin E.; Manninen, Sirkku; Haeberle, Karl-Heinz; Heerdt, C.; Werner, H.; Henderson, Gary W.; Matyssek, Rainer

2009-01-01

We examined the effect of ozone (O 3 ) on Norway spruce (Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2x ambient O 3 ranged from 64.5 to 74.2 μl O 3 l -1 h AOT40, and 117.1 to 123.2 nl O 3 l -1 4th highest daily maximum 8-h average O 3 concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased (P = 0.011) under 2x O 3 . Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year (P = 0.004) and O 3 treatment (P = 0.029). Secondary alcohols were reduced by 9.1% under 2x O 3 . Exposure to 2x O 3 increased (P = 0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O 3 on wax biosynthesis. These results demonstrate O 3 -induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees. - Free-air ozone exposure induced changes in needle wax characteristics of mature Picea abies.

Impact of Future Emissions and Climate Change on Surface Ozone over China

Science.gov (United States)

Ma, C. T.; Westervelt, D. M.; Fiore, A. M.; Rieder, H. E.; Kinney, P.; Wang, S.; Correa, G. J. P.

2017-12-01

China's immense ambient air pollution problem and world-leading greenhouse gas emissions place it at the forefront of global efforts to address these related environmental concerns. Here, we analyze the impact of ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) future emissions scenarios representative of current legislation (CLE) and maximum technically feasible emissions reductions (MFR) on surface ozone (O3) concentrations over China in the 2030s and 2050s, in the context of a changing climate. We use a suite of simulations performed with the NOAA Geophysical Fluid Dynamics Laboratory's AM3 global chemistry-climate model. To estimate the impact of climate change in isolation on Chinese air quality, we hold emissions of air pollutants including O3 precursors fixed at 2015 levels but allow climate (global sea surface temperatures and sea ice cover) to change according to decadal averages for the years 2026-2035 and 2046-2055 from a three-member ensemble of GFDL-CM3 simulations under the RCP8.5 high warming scenario. Evaluation of the present-day simulation (2015 CLE) with observations from 1497 chiefly urban air quality monitoring stations shows that simulated surface O3 is positively biased by 26 ppb on average over the domain of China. Previous studies, however, have shown that the modeled ozone response to changes in NOx emissions over the Eastern United States mirrors the magnitude and structure of observed changes in maximum daily average 8-hour (MDA8) O3 distributions. Therefore, we use the model's simulated changes for the 2030s and 2050s to project changes in policy-relevant MDA8 O3 concentrations. We find an overall increase in MDA8 O3 for CLE scenarios in which emissions of NOx precursors are projected to increase, and under MFR scenarios, an overall decrease, with the highest changes occurring in summertime for both 2030 and 2050 MFR. Under climate change alone, the model simulates a mean summertime decrease of 1.3 ppb

Adsorption-controlled growth of ferroelectric PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} films for nonvolatile memory applications by MBE

Energy Technology Data Exchange (ETDEWEB)

Theis, C.D.; Yeh, J.; Schlom, D.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Hawley, M.E.; Brown, G.W. [Los Alamos National Lab., NM (United States). Center for Materials Science

1997-09-01

Epitaxial PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} thin films have been grown on (100) SrTiO{sub 3} and (100) LaAlO{sub 3} substrates by reactive molecular beam epitaxy (MBE). Titanium is supplied to the film in the form of shuttered bursts each containing a one monolayer dose of titanium atoms for the growth of PbTiO{sub 3} and three monolayers for the growth of Bi{sub 4}Ti{sub 3}O{sub 12}. Lead, bismuth, and ozone are continuously supplied to the surface of the depositing film. Growth of phase pure, c-axis oriented epitaxial films with bulk lattice constants is achieved using an overpressure of these volatile species. With the proper choice of substrate temperature (600--650 C) and ozone background pressure (P{sub O{sub 3}} = 2 {times} 10{sup {minus}5} Torr), the excess of the volatile metals and ozone desorb from the surface of the depositing film leaving a phase-pure stoichiometric crystal. The smooth PbTiO{sub 3} surface morphology revealed by atomic force microscopy (AFM) suggests that the PbTiO{sub 3} films grow in a layer-by-layer fashion. In contrast the Bi{sub 4}Ti{sub 3}O{sub 12} films contain islands which evolve either continuously or around screw dislocations via a spiral-type growth mechanism.

Combined use of O3/H2O2 and O3/Mn2+ in flotation of dairy wastewater

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Marta Cristina Silva Carvalho

2018-05-01

Full Text Available This work investigated the degradation of organic matter present in synthetic dairy wastewater by the combination of ozonation (ozone (O3/hydrogen peroxide (H2O2 and catalytic ozonation (ozone (O3/manganese (Mn2+ associated with dispersed air flotation process. The effect of independent factors such as O3 concentration, pH and H2O2 and Mn2+ concentration was evaluated. For the flotation/O3/H2O2 treatment, the significant variables (p ≤ 0.05 were: O3 concentration (linear and quadratic effect, H2O2 concentration linear and quadratic effect, pH values (linear and quadratic effect and interaction O3 concentration versus pH. For catalytic ozonation, it was observed that the significant variable was the linear effect of O3 concentration. According to the desirability function, it was concluded that the optimal condition for the treatment of flotation/O3/H2O2 can be obtained in acidic solution using O3 concentrations greater than 42.9 mg L-1 combined with higher concentrations of H2O2 to 1071.5 mg L-1. On other hand, at pH values higher than 9.0, the addition of O3 may be neglected when using higher concentrations than 1071.5 mg L-1 of H2O2. For flotation/ozonation catalyzed by Mn2+, it was observed that metal addition did not affect treatment, resulting in an optimum condition: 53.8 mg L-1 of O3 and pH 3.6.

Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce (Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

Energy Technology Data Exchange (ETDEWEB)

Percy, Kevin E., E-mail: kpercy@nbnet.nb.c [Natural Resources Canada, Canadian Forest Service-Atlantic Forestry Centre, 1350 Regent Street, Fredericton, NB, E3B 5P7 (Canada); Manninen, Sirkku [Department of Biological and Environmental Sciences, P.O. Box 56, University of Helsinki, 00014 Helsinki (Finland); Department of Biology, P.O. Box 3000, University of Oulu, 90014 Oulu (Finland); Haeberle, Karl-Heinz [Ecophysiology of Plants, Department of Ecology, Technische Universitaet Muenchen, Am Hochanger 13, 85354 Freising (Germany); Heerdt, C.; Werner, H. [Ecoclimatology, Department of Ecology, Technische Universitaet Muenchen, Am Hochanger 13, 85354 Freising (Germany); Henderson, Gary W. [Natural Resources Canada, Canadian Forest Service-Atlantic Forestry Centre, 1350 Regent Street, Fredericton, NB, E3B 5P7 (Canada); Matyssek, Rainer [Ecophysiology of Plants, Department of Ecology, Technische Universitaet Muenchen, Am Hochanger 13, 85354 Freising (Germany)

2009-05-15

We examined the effect of ozone (O{sub 3}) on Norway spruce (Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2x ambient O{sub 3} ranged from 64.5 to 74.2 mul O{sub 3} l{sup -1} h AOT40, and 117.1 to 123.2 nl O{sub 3} l{sup -1} 4th highest daily maximum 8-h average O{sub 3} concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased (P = 0.011) under 2x O{sub 3}. Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year (P = 0.004) and O{sub 3} treatment (P = 0.029). Secondary alcohols were reduced by 9.1% under 2x O{sub 3}. Exposure to 2x O{sub 3} increased (P = 0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O{sub 3} on wax biosynthesis. These results demonstrate O{sub 3}-induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees. - Free-air ozone exposure induced changes in needle wax characteristics of mature Picea abies.

OZONE PRODUCTION EFFICIENCY AND NOX DEPLETION IN AN URBAN PLUME: INTERPRETATION OF FIELD OBSERVATIONS AND IMPLICATIONS FOR EVALUATING O3-NOX-VOC SENSITIVITY

Science.gov (United States)

Ozone production efficiency (OPE) can be defined as the number of ozone (O3) molecules photochemically produced by a molecule of NOx (NO + NO2) before it is lost from the NOx - O3 cycle. Here, we consider observational and modeling techniques to evaluate various operational defi...

Ozone production process in pulsed positive dielectric barrier discharge

Science.gov (United States)

Ono, Ryo; Oda, Tetsuji

2007-01-01

The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O2 + M → O3 + M, is estimated to be 2.5 × 10-34 cm6 s-1.

Ozone production process in pulsed positive dielectric barrier discharge

International Nuclear Information System (INIS)

Ono, Ryo; Oda, Tetsuji

2007-01-01

The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O 2 + M → O 3 + M, is estimated to be 2.5 x 10 -34 cm 6 s -1

Tropospheric Ozone Assessment Report: Database and Metrics Data of Global Surface Ozone Observations

Directory of Open Access Journals (Sweden)

Martin G. Schultz

2017-10-01

Full Text Available In support of the first Tropospheric Ozone Assessment Report (TOAR a relational database of global surface ozone observations has been developed and populated with hourly measurement data and enhanced metadata. A comprehensive suite of ozone data products including standard statistics, health and vegetation impact metrics, and trend information, are made available through a common data portal and a web interface. These data form the basis of the TOAR analyses focusing on human health, vegetation, and climate relevant ozone issues, which are part of this special feature. Cooperation among many data centers and individual researchers worldwide made it possible to build the world's largest collection of 'in-situ' hourly surface ozone data covering the period from 1970 to 2015. By combining the data from almost 10,000 measurement sites around the world with global metadata information, new analyses of surface ozone have become possible, such as the first globally consistent characterisations of measurement sites as either urban or rural/remote. Exploitation of these global metadata allows for new insights into the global distribution, and seasonal and long-term changes of tropospheric ozone and they enable TOAR to perform the first, globally consistent analysis of present-day ozone concentrations and recent ozone changes with relevance to health, agriculture, and climate. Considerable effort was made to harmonize and synthesize data formats and metadata information from various networks and individual data submissions. Extensive quality control was applied to identify questionable and erroneous data, including changes in apparent instrument offsets or calibrations. Such data were excluded from TOAR data products. Limitations of 'a posteriori' data quality assurance are discussed. As a result of the work presented here, global coverage of surface ozone data for scientific analysis has been significantly extended. Yet, large gaps remain in the surface

Effects of El Niño on Summertime Ozone Air Quality in the Eastern United States

Science.gov (United States)

Shen, Lu; Mickley, Loretta J.

2017-12-01

We investigate the effect of El Niño on maximum daily 8 h average surface ozone over the eastern United States in summer during 1980-2016. El Niño can influence the extratropical climate through the propagation of stationary waves, leading to (1) reduced transport of moist, clean air into the middle and southern Atlantic states and greater subsidence, reduced precipitation, and increased surface solar radiation in this region, as well as (2) intensified southerly flow into the south central states, which here enhances flux of moist and clean air. As a result, each standard deviation increase in the Niño 1 + 2 index is associated with an increase of 1-2 ppbv ozone in the Atlantic states and a decrease of 0.5-2 ppbv ozone in the south central states. These influences can be predicted 4 months in advance. We show that U.S. summertime ozone responds differently to eastern-type El Niño events compared to central-type events.

Effect of calcium-ozone treatment on chemical and biological properties of polyethylene terephthalate.

Science.gov (United States)

Rashid, Ahmed Nafis; Tsuru, Kanji; Ishikawa, Kunio

2015-05-01

Ozone (O3 ) treatment of polyethylene terephthalate (PET) in distilled water was performed in the presence and absence of calcium (Ca(2+) ). PET was oxidized and thus carboxylic and hydroxyl functional groups were introduced on its surface after O3 treatment, regardless of the presence or absence of Ca(2+) . In the case of O3 treatment with Ca(2+) , PET surface was modified with Ca(2+) . Ca(2+) immobilization was confirmed by X-ray photoelectron spectrometric analysis. Hydrophilicity was investigated by measuring contact angles (CA). CA of PET decreased significantly after ozonation. Surface topography of PET before and after ozone treatment was observed by scanning electron microscopy, and showed no morphological changes. In vitro studies showed enhanced rat bone marrow cell responses on the O3 -treated PET surface. Ca(2+) -O3 oxidation at 37°C for 6 h is expected to be an effective method to fabricate PET with good biocompatibility. © 2014 Wiley Periodicals, Inc.

Modulations of stratospheric ozone by volcanic eruptions

Science.gov (United States)

Blanchette, Christian; Mcconnell, John C.

1994-01-01

We have used a time series of aerosol surface based on the measurements of Hofmann to investigate the modulation of total column ozone caused by the perturbation to gas phase chemistry by the reaction N2O5(gas) + H2O(aero) yields 2HNO3(gas) on the surface of stratospheric aerosols. We have tested a range of values for its reaction probability, gamma = 0.02, 0.13, and 0.26 which we compared to unperturbed homogeneous chemistry. Our analysis spans a period from Jan. 1974 to Oct. 1994. The results suggest that if lower values of gamma are the norm then we would expect larger ozone losses for highly enhanced aerosol content that for larger values of gamma. The ozone layer is more sensitive to the magnitude of the reaction probability under background conditions than during volcanically active periods. For most conditions, the conversion of NO2 to HNO3 is saturated for reaction probability in the range of laboratory measurements, but is only absolutely saturated following major volcanic eruptions when the heterogeneous loss dominates the losses of N2O5. The ozone loss due to this heterogeneous reaction increases with the increasing chlorine load. Total ozone losses calculated are comparable to ozone losses reported from TOMS and Dobson data.

Operational surface UV radiation product from GOME-2 and AVHRR/3 data

OpenAIRE

J. Kujanpää; N. Kalakoski

2015-01-01

The surface ultraviolet (UV) radiation product, version 1.20, generated operationally in the framework of the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is described. The product is based on the total ozone column derived from the measurements of the second Global Ozone Monitoring Experiment (GOME-2) instrument aboard EUMETSA...

Ozone production process in pulsed positive dielectric barrier discharge

Energy Technology Data Exchange (ETDEWEB)

Ono, Ryo [High Temperature Plasma Center, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 227-8568 (Japan); Oda, Tetsuji [Department of Electrical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan)

2007-01-07

The ozone production process in a pulsed positive dielectric barrier discharge (DBD) is studied by measuring the spatial distribution of ozone density using a two-dimensional laser absorption method. DBD occurs in a 6 mm point-to-plane gap with a 1 mm-thick glass plate placed on the plane electrode. First, the propagation of DBD is observed using a short-gated ICCD camera. It is shown that DBD develops in three phases: primary streamer, secondary streamer and surface discharge phases. Next, the spatial distribution of ozone density is measured. It is shown that ozone is mostly produced in the secondary streamer and surface discharge, while only a small amount of ozone is produced in the primary streamer. The rate coefficient of the ozone production reaction, O + O{sub 2} + M {yields} O{sub 3} + M, is estimated to be 2.5 x 10{sup -34} cm{sup 6} s{sup -1}.

Evaluating A Priori Ozone Profile Information Used in TEMPO Tropospheric Ozone Retrievals

Science.gov (United States)

Johnson, Matthew S.; Sullivan, John T.; Liu, Xiong; Newchurch, Mike; Kuang, Shi; McGee, Thomas J.; Langford, Andrew O'Neil; Senff, Christoph J.; Leblanc, Thierry; Berkoff, Timothy;

Evaluating A Priori Ozone Profile Information Used in TEMPO Tropospheric Ozone Retrievals

Science.gov (United States)

Johnson, M. S.; Sullivan, J. T.; Liu, X.; Newchurch, M.; Kuang, S.; McGee, T. J.; Langford, A. O.; Senff, C. J.; Leblanc, T.; Berkoff, T.; Gronoff, G.; Chen, G.; Strawbridge, K. B.

2016-12-01

Ozone (O3) is a greenhouse gas and toxic pollutant which plays a major role in air quality. Typically, monitoring of surface air quality and O3 mixing ratios is primarily conducted using in situ measurement networks. This is partially due to high-quality information related to air quality being limited from space-borne platforms due to coarse spatial resolution, limited temporal frequency, and minimal sensitivity to lower tropospheric and surface-level O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite is designed to address these limitations of current space-based platforms and to improve our ability to monitor North American air quality. TEMPO will provide hourly data of total column and vertical profiles of O3 with high spatial resolution to be used as a near-real-time air quality product. TEMPO O3 retrievals will apply the Smithsonian Astrophysical Observatory profile algorithm developed based on work from GOME, GOME-2, and OMI. This algorithm uses a priori O3 profile information from a climatological data-base developed from long-term ozone-sonde measurements (tropopause-based (TB) O3 climatology). It has been shown that satellite O3 retrievals are sensitive to a priori O3 profiles and covariance matrices. During this work we investigate the climatological data to be used in TEMPO algorithms (TB O3) and simulated data from the NASA GMAO Goddard Earth Observing System (GEOS-5) Forward Processing (FP) near-real-time (NRT) model products. These two data products will be evaluated with ground-based lidar data from the Tropospheric Ozone Lidar Network (TOLNet) at various locations of the US. This study evaluates the TB climatology, GEOS-5 climatology, and 3-hourly GEOS-5 data compared to lower tropospheric observations to demonstrate the accuracy of a priori information to potentially be used in TEMPO O3 algorithms. Here we present our initial analysis and the theoretical impact on TEMPO retrievals in the lower troposphere.

The response of surface ozone to climate change over the Eastern United States

Directory of Open Access Journals (Sweden)

P. N. Racherla

2008-02-01

Full Text Available We investigate the response of surface ozone (O₃ to future climate change in the eastern United States by performing simulations corresponding to present (1990s and future (2050s climates using an integrated model of global climate, tropospheric gas-phase chemistry, and aerosols. A future climate has been imposed using ocean boundary conditions corresponding to the IPCC SRES A2 scenario for the 2050s decade. Present-day anthropogenic emissions and CO₂/CH₄ mixing ratios have been used in both simulations while climate-sensitive emissions were allowed to vary with the simulated climate. The severity and frequency of O₃ episodes in the eastern U.S. increased due to future climate change, primarily as a result of increased O₃ chemical production. The 95th percentile O₃ mixing ratio increased by 5 ppbv and the largest frequency increase occured in the 80–90 ppbv range; the US EPA's current 8-h ozone primary standard is 80 ppbv. The increased O₃ chemical production is due to increases in: 1 natural isoprene emissions; 2 hydroperoxy radical concentrations resulting from increased water vapor concentrations; and, 3 NO_x concentrations resulting from reduced PAN. The most substantial and statistically significant (p<0.05 increases in episode frequency occurred over the southeast and midatlantic U.S., largely as a result of 20% higher annual-average natural isoprene emissions. These results suggest a lengthening of the O₃ season over the eastern U.S. in a future climate to include late spring and early fall months. Increased chemical production and shorter average lifetime are two consistent features of the seasonal response of surface O₃, with increased dry deposition loss rates contributing most to the reduced lifetime in all seasons except summer. Significant interannual variability is observed in the frequency of O₃

Decadal changes in summertime reactive oxidized nitrogen and surface ozone over the Southeast United States

Science.gov (United States)

Li, Jingyi; Mao, Jingqiu; Fiore, Arlene M.; Cohen, Ronald C.; Crounse, John D.; Teng, Alex P.; Wennberg, Paul O.; Lee, Ben H.; Lopez-Hilfiker, Felipe D.; Thornton, Joel A.; Peischl, Jeff; Pollack, Ilana B.; Ryerson, Thomas B.; Veres, Patrick; Roberts, James M.; Neuman, J. Andrew; Nowak, John B.; Wolfe, Glenn M.; Hanisco, Thomas F.; Fried, Alan; Singh, Hanwant B.; Dibb, Jack; Paulot, Fabien; Horowitz, Larry W.

2018-02-01

Widespread efforts to abate ozone (O3) smog have significantly reduced emissions of nitrogen oxides (NOx) over the past 2 decades in the Southeast US, a place heavily influenced by both anthropogenic and biogenic emissions. How reactive nitrogen speciation responds to the reduction in NOx emissions in this region remains to be elucidated. Here we exploit aircraft measurements from ICARTT (July-August 2004), SENEX (June-July 2013), and SEAC4RS (August-September 2013) and long-term ground measurement networks alongside a global chemistry-climate model to examine decadal changes in summertime reactive oxidized nitrogen (RON) and ozone over the Southeast US. We show that our model can reproduce the mean vertical profiles of major RON species and the total (NOy) in both 2004 and 2013. Among the major RON species, nitric acid (HNO3) is dominant (˜ 42-45 %), followed by NOx (31 %), total peroxy nitrates (ΣPNs; 14 %), and total alkyl nitrates (ΣANs; 9-12 %) on a regional scale. We find that most RON species, including NOx, ΣPNs, and HNO3, decline proportionally with decreasing NOx emissions in this region, leading to a similar decline in NOy. This linear response might be in part due to the nearly constant summertime supply of biogenic VOC emissions in this region. Our model captures the observed relative change in RON and surface ozone from 2004 to 2013. Model sensitivity tests indicate that further reductions of NOx emissions will lead to a continued decline in surface ozone and less frequent high-ozone events.

Interactions of aqueous NOM with nanoscale TiO2: implications for ceramic membrane filtration-ozonation hybrid process.

Science.gov (United States)

Kim, Jeonghwan; Shan, Wenqian; Davies, Simon H R; Baumann, Melissa J; Masten, Susan J; Tarabara, Volodymyr V

2009-07-15

The combined effect of pH and calcium on the interactions of nonozonated and ozonated natural organic matter (NOM) with nanoscale TiO2 was investigated. The approach included characterization of TiO2 nanoparticles and NOM, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling of NOM-TiO2 and NOM-NOM interactions, batch study on the NOM adsorption onto TiO2 surface, and bench-scale study on the treatment of NOM-containing feed waters using a hybrid process that combines ozonation and ultrafiltration with a 5 kDa ceramic (TiO2 surface) membrane. It was demonstrated that depending on pH and TiO2 loading, the adsorption of NOM species is controlled by either the availability of divalent cations or by preozonation of NOM. XDLVO surface energy analysis predicts NOM adsorption onto TiO2 in the ozone-controlled regime but not in the calcium-controlled regime. In both regimes, short-range NOM-NOM and NOM-TiO2 interactions were governed by acid-base and van der Waals forces, whereas the role of electrostatic forces was relatively insignificant. Ozonation increased the surface energy of NOM, contributing to the hydrophilic repulsion component of the NOM-NOM and NOM-TiO2 interactions. In the calcium-controlled regime, neither NOM-TiO2 nor NOM-NOM interaction controlled adsorption. Non-XDLVO interactions such as intermolecular bridging by calcium were hypothesized to be responsible for the observed adsorption behavior. Adsorption data proved to be highly predictive of the permeate flux performance.

Ozone-surface reactions in five homes: surface reaction probabilities, aldehyde yields, and trends.

Science.gov (United States)

Wang, H; Morrison, G

2010-06-01

Field experiments were conducted in five homes during three seasons (summer 2005, summer 2006 and winter 2007) to quantify ozone-initiated secondary aldehyde yields, surface reaction probabilities, and trends any temporal over a 1.5-year interval. Surfaces examined include living room carpets, bedroom carpets, kitchen floors, kitchen counters, and living room walls. Reaction probabilities for all surfaces for all seasons ranged from 9.4 x 10(-8) to 1.0 x 10(-4). There were no significant temporal trends in reaction probabilities for any surfaces from summer 2005 to summer 2006, nor over the entire 1.5-year period, indicating that it may take significantly longer than this period for surfaces to exhibit any 'ozone aging' or lowering of ozone-surface reactivity. However, all surfaces in three houses exhibited a significant decrease in reaction probabilities from summer 2006 to winter 2007. The total yield of aldehydes for the summer of 2005 were nearly identical to that for summer of 2006, but were significantly higher than for winter 2007. We also observed that older carpets were consistently less reactive than in newer carpets, but that countertops remained consistently reactive, probably because of occupant activities such as cooking and cleaning. Ozone reactions taking place at indoor surfaces significantly influence personal exposure to ozone and volatile reaction products. These field studies show that indoor surfaces only slowly lose their ability to react with ozone over several year time frames, and that this is probably because of a combination of large reservoirs of reactive coatings and periodic additions of reactive coatings in the form of cooking, cleaning, and skin-oil residues. When considering exposure to ozone and its reaction products and in the absence of dramatic changes in occupancy, activities or furnishings, indoor surface reactivity is expected to change very slowly.

Relative impacts of worldwide tropospheric ozone changes and regional emission modifications on European surface-ozone levels

International Nuclear Information System (INIS)

Szopa, S.; Hauglustaine, D.A.

2007-01-01

Multi-scale models were applied to assess the surface ozone changes in 2030. Several emission scenarios are considered, ranging from (a) a pessimistic anthropogenic emission increase to (b) an optimistic decrease of emissions, and including (c) a realistic scenario that assumes the implementation of control legislations [CLE]. The two extreme scenarios lead respectively to homogeneous global increase and decrease of surface ozone, whereas low and inhomogeneous changes associated with a slight global increase of ozone are found for the CLE scenario. Over western Europe, for the CLE scenario, the benefit of European emission reduction is significantly counterbalanced by increasing global ozone levels. Considering warmer conditions over Europe and future emission modifications, the human health exposure to surface ozone is found to be significantly worsened. (authors)

Optimization of stabilized leachate treatment using ozone/persulfate in the advanced oxidation process

International Nuclear Information System (INIS)

Abu Amr, Salem S.; Aziz, Hamidi Abdul; Adlan, Mohd Nordin

2013-01-01

Highlights: ► Ozone and persulfate reagent (O 3 /S 2 O 8 2- ) was used to treat stabilized leachate. ► Central composite design (CCD) with response surface methodology (RSM) was applied. ► Operating variables including ozone and persulfate dosage, pH variance, and reaction time. ► Optimum removal of COD, color, and NH 3 –N was 72%, 96%, and 76%, respectively. ► A good value of ozone consumption (OC) obtained with 0.60 (kg O 3 /kg COD). - Abstract: The objective of this study was to investigate the performance of employing persulfate reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and persulfate dosages, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities ( 3 –N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 210 min, 30 g/m 3 ozone, 1 g/1 g COD 0 /S 2 O 8 2- ratio, and pH 10. The experimental results were corresponded well with predicted models (COD, color, and NH 3 –N removal rates of 72%, 96%, and 76%, respectively, and 0.60 (kg O 3 /kg COD OC). The results obtained in the stabilized leachate treatment were compared with those from other treatment processes, such as ozone only and persulfate S 2 O 8 2- only, to evaluate its effectiveness. The combined method (i.e., O 3 /S 2 O 8 2- ) achieved higher removal efficiencies for COD, color, and NH 3 –N compared with other studied applications. Furthermore, the new method is more efficient than ozone/Fenton in advanced oxidation process in the treatment of the same studied leachate

Effect of dissolved ozone or ferric ions on photodegradation of thiacloprid in presence of different TiO2 catalysts

International Nuclear Information System (INIS)

Cernigoj, Urh; Stangar, Urska Lavrencic; Jirkovsky, Jaromir

2010-01-01

Combining TiO 2 photocatalysis with inorganic oxidants (such as O 3 and H 2 O 2 ) or transition metal ions (Fe 3+ , Cu 2+ and Ag + ) often leads to a synergic effect. Electron transfer between TiO 2 and the oxidant is usually involved. Accordingly, the degree of synergy could be influenced by TiO 2 surface area. With this in mind, the disappearance of thiacloprid, a neonicotinoid insecticide, was studied applying various photochemical AOPs and different TiO 2 photocatalysts. In photocatalytic ozonation experiments, synergic effect of three different TiO 2 photocatalysts was quantified. Higher surface area resulted in a more pronounced synergic effect but an increasing amount of TiO 2 did not influence the degree of the synergy. This supports the theory that the synergy is a consequence of adsorption of ozone on the TiO 2 surface. No synergy was observed in photocatalytic degradation of thiacloprid in the presence of dissolved iron(III) species performed under varied experimental conditions (concentration, age of iron(III) solution, different TiO 2 films, usage of TiO 2 slurries). This goes against the literature for different organic compounds (i.e., monuron). It indicates different roles of iron(III) in the photodegradation of different organic molecules. Moreover, TiO 2 surface area did not affect photodegradation efficiency in iron(III)-based experiments which could confirm absence of electron transfer between TiO 2 photocatalyst and iron(III).

How to most effectively expand the global surface ozone observing network

Science.gov (United States)

Sofen, E. D.; Bowdalo, D.; Evans, M. J.

2016-02-01

Surface ozone observations with modern instrumentation have been made around the world for more than 40 years. Some of these observations have been made as one-off activities with short-term, specific science objectives and some have been made as part of wider networks which have provided a foundational infrastructure of data collection, calibration, quality control, and dissemination. These observations provide a fundamental underpinning to our understanding of tropospheric chemistry, air quality policy, atmosphere-biosphere interactions, etc. brought together eight of these networks to provide a single data set of surface ozone observations. We investigate how representative this combined data set is of global surface ozone using the output from a global atmospheric chemistry model. We estimate that on an area basis, 25 % of the globe is observed (34 % land, 21 % ocean). Whereas Europe and North America have almost complete coverage, other continents, Africa, South America, Australia, and Asia (12-17 %) show significant gaps. Antarctica is surprisingly well observed (78 %). Little monitoring occurs over the oceans, with the tropical and southern oceans particularly poorly represented. The surface ozone over key biomes such as tropical forests and savanna is almost completely unmonitored. A chemical cluster analysis suggests that a significant number of observations are made of polluted air masses, but cleaner air masses whether over the land or ocean (especially again in the tropics) are significantly under-observed. The current network is unlikely to see the impact of the El Niño-Southern Oscillation (ENSO) but may be capable of detecting other planetary-scale signals. Model assessment and validation activities are hampered by a lack of observations in regions where the models differ substantially, as is the ability to monitor likely changes in surface ozone over the next century. Using our methodology we are able to suggest new sites which would help to close

A novel tropopause-related climatology of ozone profiles

NARCIS (Netherlands)

Sofieva, V.F.; Tamminen, J.; Kyrola, E.; Mielonen, T.; Veefkind, J.P.; Hassler, B.; Bodeker, G.E.

2014-01-01

A new ozone climatology, based on ozonesonde and satellite measurements, spanning the altitude region between the earth's surface and ~60 km is presented (TpO3 climatology). This climatology is novel in that the ozone profiles are categorized according to calendar month, latitude and local

Three-dimensional MnO{sub 2} porous hollow microspheres for enhanced activity as ozonation catalysts in degradation of bisphenol A

Energy Technology Data Exchange (ETDEWEB)

Tan, Xiuqin; Wan, Yifeng; Huang, Yajing [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275 (China); He, Chun, E-mail: hechun@mail.sysu.edu.cn [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275 (China); Zhang, Zaili; He, Zhuoyan; Hu, Lingling; Zeng, Jiawei [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275 (China); Shu, Dong, E-mail: dshu@scnu.edu.cn [Key Lab of Technology on Electrochemical Energy Storage and Power Generation in Guangdong Universities, School of Chemistry and Environment, South China Normal University, Guangzhou, 510006 (China)

2017-01-05

Highlights: • 3D MnO{sub 2} porous hollow microspheres (PHMSs) are prepared by a self-template process. • MnO{sub 2} PHMSs with excellent adsorption and catalytic ozonation performance for BPA. • MnO{sub 2} PHMSs show enhanced activity due to hollow-mesoporous shell spherical structure. • O{sub 2}{sup −} and ·OH are reactive species to induce effective catalytic ozonation of BPA. - Abstract: Three-dimensional (3D) MnO{sub 2} porous hollow microspheres (δ- and α- MnO{sub 2} PHMSs), with high adsorption and catalytic ozonation performance, were synthesized by a self-template (MnCO{sub 3} microspheres) process at room temperature. The synthesized MnO{sub 2} PHMSs were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area. The results showed that PHMSs exhibit the excellent adsorption ability and catalytic activity owning to their hollow spherical structure, mesoporous shell and well-defined interior voids, leading to the strong adsorption for bisphenol A (BPA) and the retention of O{sub 3} molecules on catalyst. Moreover, the catalytic performance of α-MnO{sub 2} PHMSs was better than that of δ-MnO{sub 2} PHMSs which was attributed to the richer lattice oxygen of α-MnO{sub 2} PHMSs to accelerate O{sub 3} decomposition by producing more reactive oxidative species. The degradation efficiency of BPA using 3D α-MnO{sub 2} PHMSs was more than 90% in the presence of ozone within 30 min reaction time. The probe tests for reactive oxidative species (ROSs) displayed that BPA degradation by catalytic ozonation is dominated by ·O{sub 2}{sup −} and ·OH in our present study. Furthermore, the organic compounds as intermediates of the degradation process were identified by LC/MS.

Characteristics of tropospheric ozone depletion events in the Arctic spring: analysis of the ARCTAS, ARCPAC, and ARCIONS measurements and satellite BrO observations

Directory of Open Access Journals (Sweden)

J.-H. Koo

2012-10-01

Full Text Available Arctic ozone depletion events (ODEs are caused by halogen catalyzed ozone loss. In situ chemistry, advection of ozone-poor air mass, and vertical mixing in the lower troposphere are important factors affecting ODEs. To better characterize the ODEs, we analyze the combined set of surface, ozonesonde, and aircraft in situ measurements of ozone and bromine compounds during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS, the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC, and the Arctic Intensive Ozonesonde Network Study (ARCIONS experiments (April 2008. Tropospheric BrO columns retrieved from satellite measurements and back trajectory calculations are also used to investigate the characteristics of observed ODEs. In situ observations from these field experiments are inadequate to validate tropospheric BrO columns derived from satellite measurements. In view of this difficulty, we construct an ensemble of tropospheric column BrO estimates from two satellite (OMI and GOME-2 measurements and with three independent methods of calculating stratospheric BrO columns. Furthermore, we select analysis methods that do not depend on the absolute magnitude of column BrO, such as time-lagged correlation analysis of ozone and tropospheric column BrO, to understand characteristics of ODEs. Time-lagged correlation analysis between in situ (surface and ozonesonde measurements of ozone and satellite derived tropospheric BrO columns indicates that the ODEs are due to either local halogen-driven ozone loss or short-range (∼1 day transport from nearby regions with ozone depletion. The effect of in situ ozone loss is also evident in the diurnal variation difference between low (10th and 25th percentiles and higher percentiles of surface ozone concentrations at Alert, Canada. Aircraft observations indicate low-ozone air mass transported from adjacent high-BrO regions. Correlation analyses of ozone

Generation of ozone by pulsed corona discharge over water surface in hybrid gas-liquid electrical discharge reactor

Energy Technology Data Exchange (ETDEWEB)

Lukes, Petr [Department of Pulse Plasma Systems, Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 3, PO Box 17, 182 21 Prague 8 (Czech Republic); Clupek, Martin [Department of Pulse Plasma Systems, Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 3, PO Box 17, 182 21 Prague 8 (Czech Republic); Babicky, Vaclav [Department of Pulse Plasma Systems, Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 3, PO Box 17, 182 21 Prague 8 (Czech Republic); Janda, Vaclav [Department of Water Technology and Environmental Engineering, Institute of Chemical Technology, Technicka 5, 160 28 Prague 6 (Czech Republic); Sunka, Pavel [Department of Pulse Plasma Systems, Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 3, PO Box 17, 182 21 Prague 8 (Czech Republic)

2005-02-07

Ozone formation by a pulse positive corona discharge generated in the gas phase between a planar high voltage electrode made from reticulated vitreous carbon and a water surface with an immersed ground stainless steel plate electrode was investigated under various operating conditions. The effects of gas flow rate (0.5-3 litre min{sup -1}), discharge gap spacing (2.5-10 mm), applied input power (2-45 W) and gas composition (oxygen containing argon or nitrogen) on ozone production were determined. Ozone concentration increased with increasing power input and with increasing discharge gap. The production of ozone was significantly affected by the presence of water vapour formed through vaporization of water at the gas-liquid interface by the action of the gas phase discharge. The highest energy efficiency for ozone production was obtained using high voltage pulses of approximately 150 ns duration in Ar/O{sub 2} mixtures with the maximum efficiency (energy yield) of 23 g kW h{sup -1} for 40% argon content.

Generation of ozone by pulsed corona discharge over water surface in hybrid gas-liquid electrical discharge reactor

International Nuclear Information System (INIS)

Lukes, Petr; Clupek, Martin; Babicky, Vaclav; Janda, Vaclav; Sunka, Pavel

2005-01-01

Ozone formation by a pulse positive corona discharge generated in the gas phase between a planar high voltage electrode made from reticulated vitreous carbon and a water surface with an immersed ground stainless steel plate electrode was investigated under various operating conditions. The effects of gas flow rate (0.5-3 litre min -1 ), discharge gap spacing (2.5-10 mm), applied input power (2-45 W) and gas composition (oxygen containing argon or nitrogen) on ozone production were determined. Ozone concentration increased with increasing power input and with increasing discharge gap. The production of ozone was significantly affected by the presence of water vapour formed through vaporization of water at the gas-liquid interface by the action of the gas phase discharge. The highest energy efficiency for ozone production was obtained using high voltage pulses of approximately 150 ns duration in Ar/O 2 mixtures with the maximum efficiency (energy yield) of 23 g kW h -1 for 40% argon content

Ab initio hybrid DFT calculations of BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surfaces

Energy Technology Data Exchange (ETDEWEB)

Eglitis, Roberts I., E-mail: rieglitis@gmail.com

2015-12-15

Highlights: • Surface energies for AO{sub 3}-term (111) surfaces are larger than for Ti (Zr)-term surfaces. • A increase of Ti−O (Zr−O) bond covalency near the ABO{sub 3} (111) surface relative to the bulk is observed. • The ABO{sub 3} (111) surface energy is larger than the earlier calculated (001) surface energy. • Band gap for PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surfaces becomes smaller, but for BaTiO{sub 3} (111) larger with respect to the bulk . - Abstract: The results of ab initio calculations for polar BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surfaces using the CRYSTAL code are presented. By means of the hybrid B3LYP approach, the surface relaxation has been calculated for two possible B (B = Ti or Zr) or AO{sub 3} (A = Ba, Pb or Sr) BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surface terminations. According to performed B3LYP calculations, all atoms of the first surface layer, for both terminations, relax inwards. The only exception is a small outward relaxation of the PbO{sub 3}-terminated PbTiO{sub 3} (111) surface upper layer Pb atom. B3LYP calculated surface energies for BaO{sub 3}, PbO{sub 3}, SrO{sub 3} and PbO{sub 3}-terminated BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surfaces are considerably larger than the surface energies for Ti (Zr)-terminated (111) surfaces. Performed B3LYP calculations indicate a considerable increase of Ti−O (Zr−O) chemical bond covalency near the BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surface relative to the BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} bulk. Calculated band gaps at the Γ-point near the PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} (111) surfaces are reduced, but near BaTiO{sub 3} (111) surfaces increased, with respect to the BaTiO{sub 3}, PbTiO{sub 3}, SrZrO{sub 3} and PbZrO{sub 3} bulk band gap at the Γ-point values.

Decadal changes in summertime reactive oxidized nitrogen and surface ozone over the Southeast United States

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J. Li

2018-02-01

Full Text Available Widespread efforts to abate ozone (O3 smog have significantly reduced emissions of nitrogen oxides (NOx over the past 2 decades in the Southeast US, a place heavily influenced by both anthropogenic and biogenic emissions. How reactive nitrogen speciation responds to the reduction in NOx emissions in this region remains to be elucidated. Here we exploit aircraft measurements from ICARTT (July–August 2004, SENEX (June–July 2013, and SEAC4RS (August–September 2013 and long-term ground measurement networks alongside a global chemistry–climate model to examine decadal changes in summertime reactive oxidized nitrogen (RON and ozone over the Southeast US. We show that our model can reproduce the mean vertical profiles of major RON species and the total (NOy in both 2004 and 2013. Among the major RON species, nitric acid (HNO3 is dominant (∼ 42–45 %, followed by NOx (31 %, total peroxy nitrates (ΣPNs; 14 %, and total alkyl nitrates (ΣANs; 9–12 % on a regional scale. We find that most RON species, including NOx, ΣPNs, and HNO3, decline proportionally with decreasing NOx emissions in this region, leading to a similar decline in NOy. This linear response might be in part due to the nearly constant summertime supply of biogenic VOC emissions in this region. Our model captures the observed relative change in RON and surface ozone from 2004 to 2013. Model sensitivity tests indicate that further reductions of NOx emissions will lead to a continued decline in surface ozone and less frequent high-ozone events.

Improved Pt/Au and W/Pt/Au Schottky contacts on n-type ZnO using ozone cleaning

International Nuclear Information System (INIS)

Ip, K.; Gila, B.P.; Onstine, A.H.; Lambers, E.S.; Heo, Y.W.; Baik, K.H.; Norton, D.P.; Pearton, S.J.; Kim, S.; LaRoche, J.R; Ren, F.

2004-01-01

UV-ozone cleaning prior to metal deposition of either e-beam Pt contacts or sputtered W contacts on n-type single-crystal ZnO is found to significantly improve their rectifying characteristics. Pt contacts deposited directly on the as-received ZnO surface are Ohmic but show rectifying behavior with ozone cleaning. The Schottky barrier height of these Pt contacts was 0.70 eV, with ideality factor of 1.5 and a saturation current density of 6.2x10 -6 A cm -2 . In contrast, the as-deposited W contacts are Ohmic, independent of the use of ozone cleaning. Postdeposition annealing at 700 deg. C produces rectifying behavior with Schottky barrier heights of 0.45 eV for control samples and 0.49 eV for those cleaned with ozone exposure. The improvement in rectifying properties of both the Pt and W contacts is related to removal of surface carbon contamination from the ZnO

Mechanism for enhanced degradation of clofibric acid in aqueous by catalytic ozonation over MnO{sub x}/SBA-15

Energy Technology Data Exchange (ETDEWEB)

Sun, Qiangqiang; Wang, Yu [School of Chemistry & Environment, South China Normal University, Guangzhou 510006 (China); Li, Laisheng, E-mail: llsh@scnu.edu.cn [School of Chemistry & Environment, South China Normal University, Guangzhou 510006 (China); Bing, Jishuai [Key Laboratory of Aquatic Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Wang, Yingxin; Yan, Huihua [School of Chemistry & Environment, South China Normal University, Guangzhou 510006 (China)

2015-04-09

Highlights: • Clofibric acid (CA) is efficiently mineralized by O{sub 3}/MnO{sub x}/SBA-15. • Adsorption of CA and its intermediates on MnO{sub x}/SBA-15 is proved unimportant. • Initiation of hydroxyl radicals (·OH) is enhanced in O{sub 3}/MnO{sub x}/SBA-15. • Uniformly distributed MnO{sub x} accounts for the high activity of MnO{sub x}/SBA-15. • Degradation routes of CA in ozonation alone and catalytic ozonation are proposed. - Abstract: Comparative experiments were conducted to investigate the catalytic ability of MnO{sub x}/SBA-15 for the ozonation of clofibric acid (CA) and its reaction mechanism. Compared with ozonation alone, the degradation of CA was barely enhanced, while the removal of TOC was significantly improved by catalytic ozonation (O{sub 3}/MnO{sub x}/SBA-15). Adsorption of CA and its intermediates by MnO{sub x}/SBA-15 was proved unimportant in O{sub 3}/MnO{sub x}/SBA-15 due to the insignificant adsorption of CA and little TOC variation after ceasing ozone in stopped-flow experiment. The more remarkably inhibition effect of sodium bisulfite (NaHSO{sub 3}) on the removal of TOC in catalytic ozonation than in ozonation alone elucidated that MnO{sub x}/SBA-15 facilitated the generation of hydroxyl radicals (·OH), which was further verified by electron spin-resonance spectroscopy (ESR). Highly dispersed MnO{sub x} on SBA-15 were believed to be the main active component in MnO{sub x}/SBA-15. Some intermediates were indentified and different degradation routes of CA were proposed in both ozonation alone and catalytic ozonation. The amounts of small molecular carboxylic acids (i.e., formic acid (FA), acetic acid (AA) and oxalic acid (OA)) generated in catalytic ozonation were lower than in ozonation alone, resulting from the generation of more ·OH.

Overview of surface ozone variability in East Asia-North Pacific region during IGAC/APARE (1994--1996).

Science.gov (United States)

Lam, K S; Wang, T J; Wang, T; Tang, J; Kajii, Y; Liu, C M; Shim, S G

2004-01-01

Surface ozone (O3) was measured at Oki Island (Japan), Cheju Island (South Korea), Lanyu Island (Taiwan Province, China), Cape D'Aguilar (Hong Kong SAR) and Lin'an, Longfenshan, Waliguan (China mainland) during January 1994--December 1996 as a component of IGAC/APARE (International Global Atmospheric Chemistry/East Asia-North Pacific Regional Experiment). This paper gave a joint discussion on the observational results at these stations over the study region. Investigations showed that the average of surface O3 mixing ratios at the seven sites are 47.9+/-15.8, 48.1+/-17.9, 30.2+/-16.4, 31.6+/-17.5, 36.3+/-17.5, 34.8+/-11.5 and 48.2+/-9.5 ppbv, respectively. Significant diurnal variations of surface O3 have been observed at Oki, Cheju, D'Aguilar, Lin'an and Longfenshan. Their annual averaged diurnal differences range from 8 to 23 ppbv and differ in each season. Surface O3 at Lanyu and Waliguan do not show strong diurnal variability. Seasonal cycles of surface O3 showed difference at the temperate and the subtropical remote sites. Oki has a summer minimum-spring maximum, while Lanyu has a summer minimum-autumn maximum. The suburban sites at D'Aguilar and Lin'an report high-level O3 in autumn and low level O3 in summer. Surface O3 remains-high in autumn and low in winter at the rural site Longfenshan. For the global background station Waliguan, surface O3 exhibits a broad spring-summer maximum and autumn-winter minimum. The backward air trajectories to these sites have shown different pathways of long-range transport of air pollution from East Asia Continent to North Pacific Ocean. Surface O3 was found to be strongly and positively correlated with CO at Oki and Lanyu, especially in spring and autumn, reflecting the substantial photochemical buildup of O3 on a regional scale. It is believed that the regional sources of pollution in East Asia have enhanced the average surface O3 concentrations in the background atmosphere of North Pacific.

Degradation of the ammonia wastewater in aqueous medium with ozone in combination with mesoporous TiO2 catalytic

Science.gov (United States)

Liu, Zhiwu; Qiu, Jianping; Zheng, Chaocan; Li, Liqing

2017-03-01

TiO2 mesoporous nanomaterials are now widely used in catalytic ozone technology. In this paper, the market P25 as precursor hydrothermal method to prepare TiO2 mesoporous materials, ozone catalyst material characterization by transmission electron microscopy, surface area analyzers, and X-ray diffraction technique and found that nanotubes, nanosheets, nanorods through characterization results, nano-particles of different morphology and anatase and rutile proportion of the ozone catalytic material can be controlled by the calcination temperature and the temperature of hot water to give, and with the hot water temperature and calcination temperature, the catalyst becomes small aperture size larger catalyst crystalline phase from anatase to rutile gradually shift. Catalytic materials have been prepared by the Joint ozone degradation of ammonia wastewater to evaluate mesoporous TiO2 nanomaterials ozone catalytic performance, the results showed that: ammonia wastewater removal efficiency of various catalytic materials relatively separate ozone and markets P25 effects are significantly improved, and TiO2 nanotubes cooperate with ozone degradation ammonia wastewater highest efficiency, in addition, rutile TiO2 catalysts, the more the better the performance of their ozone catalysis.

Effects of ozone-vegetation coupling on surface ozone air quality via biogeochemical and meteorological feedbacks

Science.gov (United States)

Sadiq, Mehliyar; Tai, Amos P. K.; Lombardozzi, Danica; Martin, Maria Val

2017-02-01

Tropospheric ozone is one of the most hazardous air pollutants as it harms both human health and plant productivity. Foliage uptake of ozone via dry deposition damages photosynthesis and causes stomatal closure. These foliage changes could lead to a cascade of biogeochemical and biogeophysical effects that not only modulate the carbon cycle, regional hydrometeorology and climate, but also cause feedbacks onto surface ozone concentration itself. In this study, we implement a semi-empirical parameterization of ozone damage on vegetation in the Community Earth System Model to enable online ozone-vegetation coupling, so that for the first time ecosystem structure and ozone concentration can coevolve in fully coupled land-atmosphere simulations. With ozone-vegetation coupling, present-day surface ozone is simulated to be higher by up to 4-6 ppbv over Europe, North America and China. Reduced dry deposition velocity following ozone damage contributes to ˜ 40-100 % of those increases, constituting a significant positive biogeochemical feedback on ozone air quality. Enhanced biogenic isoprene emission is found to contribute to most of the remaining increases, and is driven mainly by higher vegetation temperature that results from lower transpiration rate. This isoprene-driven pathway represents an indirect, positive meteorological feedback. The reduction in both dry deposition and transpiration is mostly associated with reduced stomatal conductance following ozone damage, whereas the modification of photosynthesis and further changes in ecosystem productivity are found to play a smaller role in contributing to the ozone-vegetation feedbacks. Our results highlight the need to consider two-way ozone-vegetation coupling in Earth system models to derive a more complete understanding and yield more reliable future predictions of ozone air quality.

Effect of ozone treatment on the optical and electrical properties of HfSiO thin films

International Nuclear Information System (INIS)

Geng, Yang; Yang, Wen; Zhu, Shang-Bin; Zhang, Yuan; Sun, Qing-Qing; Lu, Hong-Liang; Zhang, David Wei

2014-01-01

The effect of room temperature ozone oxidation treatment on thin HfSiO film grown by atomic layer deposition (ALD) has been investigated. The optical and electrical properties with different post-ozone oxidation time were characterized. The evolution of ozone interacting with HfSiO films was clearly illuminated. Ozone can repair the lossy chemical bonds and vacancies, resulting in the improvement of packing density and polarizability of HfSiO films. With more ozone entering the HfSiO films, the refractive index, dielectric constant, and interfacial properties can be greatly upgraded. Furthermore, the frequency dispersion of ALD-HfSiO film can be improved after O 3 treatment time for 8 min. (orig.)

Seasonal and spatial variability of surface ozone over China: contributions from background and domestic pollution

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Y. Wang

2011-04-01

Full Text Available Both observations and a 3-D chemical transport model suggest that surface ozone over populated eastern China features a summertime trough and that the month when surface ozone peaks differs by latitude and region. Source-receptor analysis is used to quantify the contributions of background ozone and Chinese anthropogenic emissions on this variability. Annual mean background ozone over China shows a spatial gradient from 55 ppbv in the northwest to 20 ppbv in the southeast, corresponding with changes in topography and ozone lifetime. Pollution background ozone (annual mean of 12.6 ppbv shows a minimum in the summer and maximum in the spring. On the monthly-mean basis, Chinese pollution ozone (CPO has a peak of 20–25 ppbv in June north of the Yangtze River and in October south of it, which explains the peaks of surface ozone in these months. The summertime trough in surface ozone over eastern China can be explained by the decrease of background ozone from spring to summer (by −15 ppbv regionally averaged over eastern China. Tagged simulations suggest that long-range transport of ozone from northern mid-latitude continents (including Europe and North America reaches a minimum in the summer, whereas ozone from Southeast Asia exhibits a maximum in the summer over eastern China. This contrast in seasonality provides clear evidence that the seasonal switch in monsoonal wind patterns plays a significant role in determining the seasonality of background ozone over China.

Surface ozone in China: present-day distribution and long-term changes

Science.gov (United States)

Xu, X.; Lin, W.; Xu, W.

2017-12-01

Reliable knowledge of spatio-temporal variations of surface ozone is highly needed to assess the impacts of ozone on human health, ecosystem and climate. Although regional distributions and trends of surface ozone in European and North American countries have been well characterized, little is known about the variability of surface ozone in many other countries, including China, where emissions of ozone precursors have been changing rapidly in recent decades. Here we present the first comprehensive description of present-day (2013-2017) distribution and long-term changes of surface ozone in mainland China. Recent ozone measurements from China's air quality monitoring network (AQMN) are analyzed to show present-day distributions of a few ozone exposure metrics for urban environment. Long-term measurements of ozone at six background sites, a rural site and an urban are used to study the trends of ozone in background, rural and urban air, respectively. The average levels of ozone at the AQMN sites (mainly urban) are close to those found at many European and North American sites. However, ozone at most of the sites shows very large diurnal and seasonal variations so that ozone nonattainment can occur in many cities, particularly those in the North China Plain (NCP), the south of Northeast China (NEC), the Yangtze River Delta (YRD), the Pearl River Delta (PRD), and the Sichuan Basin-Chongqing region (SCB). In all these regions, particularly in the NCP, the maximum daily 8-h average (MDA8) ozone concentration can significantly exceed the national limit (75 ppb). High annual sum of ozone means over 35 ppb (SOMO35) exist mainly in the NCP, NEC and YRD, with regional averages over 4000 ppb·d. Surface ozone has significantly increased at Waliguan (a baseline site in western China) and Shangdianzi (a background site in the NCP), and decreased in winter and spring at Longfengshan (a background site in Northeast China). No clear trend can be derived from long-term measurements

Removal of diethyl phthalate from water solution by adsorption, photo-oxidation, ozonation and advanced oxidation process (UV/H2O2, O3/H2O2 and O3/activated carbon)

International Nuclear Information System (INIS)

Medellin-Castillo, Nahum A.; Ocampo-Pérez, Raúl; Leyva-Ramos, Roberto; Sanchez-Polo, Manuel; Rivera-Utrilla, José; Méndez-Díaz, José D.

2013-01-01

The objective of this work was to compare the effectiveness of conventional technologies (adsorption on activated carbon, AC, and ozonation) and technologies based on advanced oxidation processes, AOPs, (UV/H 2 O 2 , O 3 /AC, O 3 /H 2 O 2 ) to remove phthalates from aqueous solution (ultrapure water, surface water and wastewater). Diethyl phthalate (DEP) was chosen as a model pollutant because of its high water solubility (1080 mg/L at 293 K) and toxicity. The activated carbons showed a high adsorption capacity to adsorb DEP in aqueous solution (up to 858 mg/g), besides the adsorption mechanism of DEP on activated carbon is governed by dispersive interactions between π electrons of its aromatic ring with π electrons of the carbon graphene planes. The photodegration process showed that the pH solution does not significantly affect the degradation kinetics of DEP and the first-order kinetic model satisfactorily fitted the experimental data. It was observed that the rate of decomposition of DEP with the O 3 /H 2 O 2 and O 3 /AC systems is faster than that with only O 3 . The technologies based on AOPs (UV/H 2 O 2 , O 3 /H 2 O 2 , O 3 /AC) significantly improve the degradation of DEP compared to conventional technologies (O 3 , UV). AC adsorption, UV/H 2 O 2 , O 3 /H 2 O 2 , and O 3 /AC showed a high yield to remove DEP; however, the disadvantage of AC adsorption is its much longer time to reach maximum removal. The best system to treat water (ultrapure and natural) polluted with DEP is the O 3 /AC one since it achieved the highest DEP degradation and TOC removal, as well as the lower water toxicity. -- Highlights: ► Activated carbons showed a high adsorption capacity (up to 858 mg/g) to remove DEP. ► The pH solution did not significantly affect the photodegradation kinetics of DEP. ► The O 3 /H 2 O 2 and O 3 /AC systems were more efficient than O 3 to degrade DEP. ► The generation of HO • from O 3 was enhanced by ACs, mainly by those of basic nature. ► O

Validation of MIPAS IMK/IAA V5R_O3_224 ozone profiles

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A. Laeng

2014-11-01

Full Text Available We present the results of an extensive validation program of the most recent version of ozone vertical profiles retrieved with the IMK/IAA (Institute for Meteorology and Climate Research/Instituto de Astrofísica de Andalucía MIPAS (Michelson Interferometer for Passive Atmospheric Sounding research level 2 processor from version 5 spectral level 1 data. The time period covered corresponds to the reduced spectral resolution period of the MIPAS instrument, i.e., January 2005–April 2012. The comparison with satellite instruments includes all post-2005 satellite limb and occultation sensors that have measured the vertical profiles of tropospheric and stratospheric ozone: ACE-FTS, GOMOS, HALOE, HIRDLS, MLS, OSIRIS, POAM, SAGE II, SCIAMACHY, SMILES, and SMR. In addition, balloon-borne MkIV solar occultation measurements and ground-based Umkehr measurements have been included, as well as two nadir sensors: IASI and SBUV. For each reference data set, bias determination and precision assessment are performed. Better agreement with reference instruments than for the previous data version, V5R_O3_220 (Laeng et al., 2014, is found: the known high bias around the ozone vmr (volume mixing ratio peak is significantly reduced and the vertical resolution at 35 km has been improved. The agreement with limb and solar occultation reference instruments that have a known small bias vs. ozonesondes is within 7% in the lower and middle stratosphere and 5% in the upper troposphere. Around the ozone vmr peak, the agreement with most of the satellite reference instruments is within 5%; this bias is as low as 3% for ACE-FTS, MLS, OSIRIS, POAM and SBUV.

Dobson spectrophotometer ozone measurements during international ozone rocketsonde intercomparison

Science.gov (United States)

Parsons, C. L.

1980-01-01

Measurements of the total ozone content of the atmosphere, made with seven ground based instruments at a site near Wallops Island, Virginia, are discussed in terms for serving as control values with which the rocketborne sensor data products can be compared. These products are profiles of O3 concentration with altitude. By integrating over the range of altitudes from the surface to the rocket apogee and by appropriately estimating the residual ozone amount from apogee to the top of the atmosphere, a total ozone amount can be computed from the profiles that can be directly compared with the ground based instrumentation results. Dobson spectrophotometers were used for two of the ground-based instruments. Preliminary data collected during the IORI from Dobson spectrophotometers 72 and 38 are presented. The agreement between the two and the variability of total ozone overburden through the experiment period are discussed.

Preliminary SEM Observations on the Surface of Elastomeric Impression Materials after Immersion or Ozone Disinfection

Science.gov (United States)

Prombonas, Anthony; Yannikakis, Stavros; Karampotsos, Thanasis; Katsarou, Martha-Spyridoula; Drakoulis, Nikolaos

2016-01-01

Introduction Surface integrity of dental elastomeric impression materials that are subjected to disinfection is of major importance for the quality of the final prosthetic restorations. Aim The aim of this qualitative Scanning Electronic Microscopy (SEM) study was to reveal the effects of immersion or ozone disinfection on the surface of four dental elastomeric impression materials. Materials and Methods Four dental elastomeric impression material brands were used (two vinyl polysiloxane silicones, one polyether, and one vinyl polyether silicone). Total of 32 specimens were fabricated, eight from each impression material. Specimens were immersion (0.525% sodium hypochlorite solution or 0.3% benzalkonium chloride solution) or ozone disinfected or served as controls and examined with SEM. Results Surface degradation was observed on several speci-mens disinfected with 0.525% sodium hypochlorite solution. Similar wavy-wrinkling surface structures were observed in almost all specimens, when treated either with 0.3% benzalkonium chloride solution or ozone. Conclusion The SEM images obtained from this study revealed that both immersion disinfectants and ozone show similar impression material surface alterations. Ozone seems to be non-inferior as compared to immersion disinfectants, but superior as to environmental protection. PMID:28208993

Analysis of observed surface ozone in the dry season over Eastern Thailand during 1997-2012

Science.gov (United States)

Assareh, Nosha; Prabamroong, Thayukorn; Manomaiphiboon, Kasemsan; Theramongkol, Phunsak; Leungsakul, Sirakarn; Mitrjit, Nawarat; Rachiwong, Jintarat

2016-09-01

This study analyzed observed surface ozone (O3) in the dry season over a long-term period of 1997-2012 for the eastern region of Thailand and incorporated several technical tools or methods in investigating different aspects of O3. The focus was the urbanized and industrialized coastal areas recently recognized as most O3-polluted areas. It was found that O3 is intensified most in the dry-season months when meteorological conditions are favorable to O3 development. The diurnal variations of O3 and its precursors show the general patterns of urban background. From observational O3 isopleth diagrams and morning ratios of non-methane volatile organic compounds (NMVOC) and nitrogen oxides (NOx), the chemical regime of O3 formation was identified as VOC-sensitive, and the degree of VOC sensitivity tends to increase over the years, suggesting emission control on VOC to be suitable for O3 management. Both total oxidant analysis and back-trajectory modeling (together with K-means clustering) indicate the potential role of regional transport or influence in enhancing surface O3 level over the study areas. A meteorological adjustment with generalized linear modeling was performed to statistically exclude meteorological effects on the variability of O3. Local air-mass recirculation factor was included in the modeling to support the coastal application. The derived trends in O3 based on the meteorological adjustment were found to be significantly positive using a Mann-Kendall test with block bootstrapping.

Surface ozone concentrations in Europe: Links with the regional-scale atmospheric circulation

Science.gov (United States)

Davies, T. D.; Kelly, P. M.; Low, P. S.; Pierce, C. E.

1992-06-01

Daily surface ozone observations from 1978 (1976 for some analyses) to 1988 for Bottesford (United Kingdom), Cabauw, Kloosterburen (The Netherlands), Hohenpeissenberg, Neuglobsow, Hamburg, and Arkona (Germany) are used to analyze links between surface ozone variations and the atmospheric circulation. A daily Europe-wide synoptic classification highlights marked differences between surface ozone/meteorology relationships in summer and winter. These relationships are characterized by correlations between daily surface ozone concentrations at each station and a local subregional surface pressure gradient (a wind speed index). Although there are geographical variations, which are explicable in terms of regional climatology, there are distinct annual cycles. In summer, the surface ozone/wind speed relationship exhibits the expected negative sign; however, in winter, the relationship is, in the main, strongly positive, especially at those stations which are more influenced by the vigorous westerlies. Spring and autumn exhibit negative, positive, or transitional (between summer and winter) behavior, depending on geographical position. It is suggested that these relationships reflect the importance of vertical exchange from the free troposphere to the surface in the nonsummer months. Composite surface pressure patterns and surface pressure anomaly (from the long-term mean) patterns associated with high surface ozone concentrations on daily and seasonal time scales are consistent with the surface ozone/wind speed relationships. Moreover, they demonstrate that high surface ozone concentrations, in a climatological time frame, can be associated with mean surface pressure patterns which have a synoptic reality and are robust. Such an approach may be useful in interpreting past variations in surface ozone and may help to isolate the effect of human activity. It is also possible that assessments can be made of the effect of projected future changes in the atmospheric circulation

Characteristics of Surface Ozone in Agra, a Sub-urban site in Indo ...

Indian Academy of Sciences (India)

65

Ozone (O3) is a secondary pollutant which has an important effect on air quality, climate. 49 change and atmospheric chemistry (Solomon et al., 2000; Sitch et al., 2007). Depending on its. 50 location in the atmosphere, O3 can influence human health and climate; in the stratosphere, O3. 51 filters out detrimental ultraviolet ...

Catalytic ozonation of oxalate with a cerium supported palladium oxide: An efficient degradation not relying on hydroxyl radical oxidation

KAUST Repository

Zhang, Tao; Li, Weiwei; Croue, Jean-Philippe

2011-01-01

The cerium supported palladium oxide (PdO/CeO 2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO 2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO 2 of the catalyst forming surface complexes, and 2) O 3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O 2), and O 2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO 2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter. © 2011 American Chemical Society.

Catalytic ozonation of oxalate with a cerium supported palladium oxide: An efficient degradation not relying on hydroxyl radical oxidation

KAUST Repository

Zhang, Tao

2011-11-01

The cerium supported palladium oxide (PdO/CeO 2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO 2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO 2 of the catalyst forming surface complexes, and 2) O 3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O 2), and O 2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO 2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter. © 2011 American Chemical Society.

Detoxification and repair process of ozone injury: From O3 uptake to gene expression adjustment

International Nuclear Information System (INIS)

Castagna, A.; Ranieri, A.

2009-01-01

Plants react to O 3 threat by setting up a variety of defensive strategies involving the co-ordinated modulation of stress perception, signalling and metabolic responses. Although stomata largely controls O 3 uptake, differences in O 3 tolerance cannot always be ascribed to changes in stomatal conductance but cell protective and repair processes should be taken into account. O 3 -driven ROS production in the apoplast induces a secondary, active, self-propagating generation of ROS, whose levels must be finely tuned, by many enzymatic and non-enzymatic antioxidant systems, to induce gene activation without determining uncontrolled cell death. Additional signalling molecules, as ethylene, jasmonic and salicylic acid are also crucial to determine the spreading and the containment of leaf lesions. The main recent results obtained on O 3 sensing, signal transduction, ROS formation and detoxification mechanisms are here discussed. - A dissection of the complex network of interacting mechanisms which determine the cell fate under ozone stress.

Impact of East Asian Summer Monsoon on Surface Ozone Pattern in China

Science.gov (United States)

Li, Shu; Wang, Tijian; Huang, Xing; Pu, Xi; Li, Mengmeng; Chen, Pulong; Yang, Xiu-Qun; Wang, Minghuai

2018-01-01

Tropospheric ozone plays a key role in regional and global atmospheric and climate systems. In East Asia, ozone can be affected both in concentration level and spatial pattern by typical monsoon climate. This paper uses three different indices to identify the strength of East Asian summer monsoon (EASM) and explores the possible impact of EASM intensity on the ozone pattern through synthetic and process analysis. The difference in ozone between three strong and three weak monsoon years was analyzed using the simulations from regional climate model RegCM4-Chem. It was found that EASM intensity can significantly influence the spatial distribution of ozone in the lower troposphere. When EASM is strong, ozone in the eastern part of China (28°N - 42° N) is reduced, but the inverse is detected in the north and south. The surface ozone difference ranges from -7 to 7 ppbv during the 3 months (June to August) of the EASM, with the most obvious difference in August. Difference of the 3 months' average ozone ranges from -3.5 to 4 ppbv. Process analysis shows that the uppermost factor controlling ozone level during summer monsoon seasons is the chemistry process. Interannual variability of EASM can impact the spatial distribution of ozone through wind in the lower troposphere, cloud cover, and downward shortwave radiation, which affect the transport and chemical formation of ozone. The phenomenon should be addressed when considering the interaction between ozone and the climate in East Asia region.

Effects of black carbon and boundary layer interaction on surface ozone in Nanjing, China

Directory of Open Access Journals (Sweden)

J. Gao

2018-05-01

Full Text Available As an important solar radiation absorbing aerosol, the effect of black carbon (BC on surface ozone, via reducing photolysis rate, has been widely discussed by offline model studies. However, BC–boundary layer (BL interactions also influence surface ozone. Using the online model simulations and process analysis, we demonstrate the significant impact of BC–BL interaction on surface ozone in Nanjing. The absorbing effect of BC heats the air above the BL and suppresses and delays the development of the BL, which eventually leads to a change in surface ozone via a change in the contributions from chemical and physical processes (photochemistry, vertical mixing and advection. For chemical processes, the suppression of the BL leads to large amounts of ozone precursors being confined below the BL which has an increased effect on ozone chemical production and offsets the decrease caused by the reduction of the photolysis rate, thus enhancing ozone chemical formation from 10:00 to 12:00 LT. Furthermore, changes in physical processes, especially the vertical mixing process, show a more significant influence on surface ozone. The weakened turbulence, caused by the suppressed BL, entrains much less ozone aloft down to the surface. Finally, summing-up the changes in the processes, surface ozone reduces before noon and the maximum reduction reaches 16.4 ppb at 12:00 LT. In the afternoon, the changes in chemical process are small which inconspicuously influence surface ozone. However, change in the vertical mixing process still influences surface ozone significantly. Due to the delayed development of the BL, there are obvious ozone gradients around the top of BL. Therefore, high concentrations of ozone aloft can still be entrained down to the surface which offsets the reduction of surface ozone. Comparing the changes in the processes, the change in vertical mixing plays the most important role in impacting surface ozone. Our results highlight the

Effects of black carbon and boundary layer interaction on surface ozone in Nanjing, China

Science.gov (United States)

Gao, Jinhui; Zhu, Bin; Xiao, Hui; Kang, Hanqing; Pan, Chen; Wang, Dongdong; Wang, Honglei

2018-05-01

As an important solar radiation absorbing aerosol, the effect of black carbon (BC) on surface ozone, via reducing photolysis rate, has been widely discussed by offline model studies. However, BC-boundary layer (BL) interactions also influence surface ozone. Using the online model simulations and process analysis, we demonstrate the significant impact of BC-BL interaction on surface ozone in Nanjing. The absorbing effect of BC heats the air above the BL and suppresses and delays the development of the BL, which eventually leads to a change in surface ozone via a change in the contributions from chemical and physical processes (photochemistry, vertical mixing and advection). For chemical processes, the suppression of the BL leads to large amounts of ozone precursors being confined below the BL which has an increased effect on ozone chemical production and offsets the decrease caused by the reduction of the photolysis rate, thus enhancing ozone chemical formation from 10:00 to 12:00 LT. Furthermore, changes in physical processes, especially the vertical mixing process, show a more significant influence on surface ozone. The weakened turbulence, caused by the suppressed BL, entrains much less ozone aloft down to the surface. Finally, summing-up the changes in the processes, surface ozone reduces before noon and the maximum reduction reaches 16.4 ppb at 12:00 LT. In the afternoon, the changes in chemical process are small which inconspicuously influence surface ozone. However, change in the vertical mixing process still influences surface ozone significantly. Due to the delayed development of the BL, there are obvious ozone gradients around the top of BL. Therefore, high concentrations of ozone aloft can still be entrained down to the surface which offsets the reduction of surface ozone. Comparing the changes in the processes, the change in vertical mixing plays the most important role in impacting surface ozone. Our results highlight the great impacts BC

Some recent results of Russian measurements of surface ozone in Antarctica. A meteorological interpretation

Energy Technology Data Exchange (ETDEWEB)

Gruzdev, A.N.; Elokhov, A.S.; Makarov, O.V.; Mokhov, I.I. (Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Atmospheric Physics)

1993-01-01

Surface ozone measurements were carried out at Molodezhnaya and Mirny stations in spring 1987-autumn 1988. The data show an annual variation with a summer minimum at 15 ppbv value. The striking feature of the surface ozone record is two types of day-to-day variability. One of the types is characterized by large day-to-day variations with about 10 ppbv magnitude. The likely mechanism of such variations is the vertical transport induced by cyclonic activity. The other type occurs in synoptically quiet periods (frequent in summer) when the day-to-day ozone variations are significant but not so large. The most likely mechanism of these variations is the slope katabatic wind which transports ozone from inside the Antarctic continent. The latitudinal distribution of surface ozone for this period, measured aboard an aircraft, showed a slight increase towards Vostok station. (26 refs., 3 figs.).

Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

Science.gov (United States)

Martin, Randall V.; Fiore, Arlene M.; VanDonkelaar, Aaron

2004-01-01

We present a novel capability in satellite remote sensing with implications for air pollution control strategy. We show that the ratio of formaldehyde columns to tropospheric nitrogen dioxide columns is an indicator of the relative sensitivity of surface ozone to emissions of nitrogen oxides (NO(x) = NO + NO2) and volatile organic compounds (VOCs). The diagnosis from these space-based observations is highly consistent with current understanding of surface ozone chemistry based on in situ observations. The satellite-derived ratios indicate that surface ozone is more sensitive to emissions of NO(x) than of VOCs throughout most continental regions of the Northern Hemisphere during summer. Exceptions include Los Angeles and industrial areas of Germany. A seasonal transition occurs in the fall when surface ozone becomes less sensitive to NOx and more sensitive to VOCs.

3D analysis of high ozone production rates observed during the ESCOMPTE campaign

Science.gov (United States)

Coll, Isabelle; Pinceloup, Stéphanie; Perros, Pascal E.; Laverdet, Gérard; Le Bras, Georges

2005-03-01

The development of environmental policies to reduce the ozone levels around large agglomerations requires a good understanding of the development of ozone episodes. In particular, it is necessary to know the location and photochemical activity of the plume where ozone is formed. Measurement campaigns make it possible not only to characterize the concentration fields of ozone and its precursors but also to identify the zones of strong ozone production, by means of specific measurements and kinetic calculations. The combination of the observation-based data with numerical simulations allows to better characterize photochemical pollution. This paper presents a study carried out within the ESCOMPTE program and based on the determination of ozone production rates by experimental and numerical methods: ground measurements of peroxy radicals, NO x at a rural site, airborne measurements of NO X and O 3, Eulerian modeling. The reported case is of particular interest since it corresponds to an episode with very different photochemical situations. The diurnal variations of the peroxy radical concentration are analyzed in relation to those of ozone and its precursors. Ozone production rates— P(O 3)-are studied over one particular day. The results show particularly high concentrations of RO 2+HO 2 at ground level (up to 200 pptv) under the influence of the urban and industrial plume, but also highlight very high production rates of ozone (60 to 80 ppbv h -1) a few tens of kilometers from the sources. The results show satisfactory agreement between the various approaches. Modeling provides a four-dimensional (4D) description of the plumes, in particular the relation between the ozone precursor concentrations and P(O 3) on the ground.

Surface chemistry of a pine-oil cleaner and other terpene mixtures with ozone on vinyl flooring tiles.

Science.gov (United States)

Ham, Jason E; Wells, J Raymond

2011-04-01

Indoor environments are dynamic reactors where consumer products (such as cleaning agents, deodorants, and air fresheners) emit volatile organic compounds (VOCs) that can subsequently interact with indoor oxidants such as ozone (O(3)), hydroxyl radicals, and nitrate radicals. Typically, consumer products consist of mixtures of VOCs and semi-VOCs which can react in the gas-phase or on surfaces with these oxidants to generate a variety of oxygenated products. In this study, the reaction of a pine-oil cleaner (POC) with O(3) (100ppb) on a urethane-coated vinyl flooring tile was investigated at 5% and 50% relative humidity. These results were compared to previous α-terpineol+O(3) reactions on glass and vinyl surfaces. Additionally, other terpene and terpene alcohol mixtures were formulated to understand the emission profiles as seen in the POC data. Results showed that the α-terpineol+O(3) reaction products were the prominent species that were also observed in the POC/O(3) surface experiments. Furthermore, α-terpineol+O(3) reactions generate the largest fraction of oxygenated products even in equal mixtures of other terpene alcohols. This finding suggests that the judicial choice of terpene alcohols for inclusion in product formulations may be useful in reducing oxidation product emissions. Published by Elsevier Ltd.

Percutaneous intradiscal ozone (O3)-injection: an experimental study in canines

International Nuclear Information System (INIS)

Yu Zhijian; He Xiaofeng; Chen Yong; Zeng Qingle; Liu Chihong; Zhao Zhongqing; Lu Yong; Li Yanhao

2002-01-01

Objective: To evaluate the influence of ozone on normal nucleus pulpous and the safety of intradiscal ozone-injection for the treatment of herniated lumbar disc. Methods: Ozone was injected into selected lumbar discs (3 ml) and the para-spinal space (7 ml) with 20 G Chiba needle under fluoroscopy in five canines. The ozone concentration was 30 μg/ml and 50 μg/ml respectively. Two discs were selected for each concentration. Total 20 discs were injected. Three of the canines were given one-time ozone-injection and were sacrificed for pathology one week, one month and two months respectively after the procedure, and the other two canines were given two-time ozone-injection and were sacrificed one month and two months respectively after the procedure. The specimens including nucleus pulpous, end-plate, spinal cord, nerve root, and greater psoas muscle were observed macroscopically and microscopically. Results: No serious behavior abnormalities were observed in all animals. The atrophy of nucleus pulpous could be observed one month after ozone-injection due to significant reduction of water and extensive proliferation of collagenous fiber. The influence on the atrophy of nucleus pulpous demonstrated no apparent difference between the selected two concentrations of ozone, but was more apparent with two-time injection than that with one-time injection. The end-plates increased slightly or moderately in thickness in 16 simples and a few of fibers in greater psoas muscle suffered slight atrophy in 5 samples. Conclusion: It is suggested that percutaneous intradiscal ozone-injection is a safe method, and can cause gradual atrophy of nucleus pulpous. This study provides the evidence of the feasibility and value of this procedure's application in clinics

Retrieval of Surface Ozone from UV-MFRSR Irradiances using Deep Learning

Science.gov (United States)

Chen, M.; Sun, Z.; Davis, J.; Zempila, M.; Liu, C.; Gao, W.

2017-12-01

High concentration of surface ozone is harmful to humans and plants. USDA UV-B Monitoring and Research Program (UVMRP) uses Ultraviolet (UV) version of Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR) to measure direct, diffuse, and total irradiances every three minutes at seven UV channels (i.e. 300, 305, 311, 317, 325, 332, and 368 nm channels with 2 nm full width at half maximum). Based on the wavelength dependency of aerosol optical depths, there have been plenty of literatures exploring retrieval methods of total column ozone from UV-MFRSR measurements. However, few has explored the retrieval of surface ozone. The total column ozone is the integral of the multiplication of ozone concentration (varying by height and time) and cross section (varying by wavelength and temperature) over height. Because of the distinctive values of ozone cross section in the UV region, the irradiances at seven UV channels have the potential to resolve the ozone concentration at multiple vertical layers. If the UV irradiances at multiple time points are considered together, the uncertainty or the vertical resolution of ozone concentrations can be further improved. In this study, the surface ozone amounts at the UVMRP station located at Billings, Oklahoma are estimated from the adjacent (i.e. within 200 miles) US Environmental Protection Agency (EPA) surface ozone observations using the spatial analysis technique. Then, the (direct normal) irradiances of UVMRP at one or more time points as inputs and the corresponding estimated surface ozone from EPA as outputs are fed into a pre-trained (dense) deep neural network (DNN) to explore the hidden non-linear relationship between them. This process could improve our understanding of their physical/mathematical relationship. Finally, the optimized DNN is tested with the preserved 5% of the dataset, which are not used during training, to verify the relationship.

Convection links biomass burning to increased tropical ozone: However, models will tend to overpredict O3

Science.gov (United States)

Chatfield, Robert B.; Delany, Anthony C.

1990-10-01

Biomass burning throughout the inhabited portions of the tropics generates precursors which lead to significant local atmospheric ozone pollution. Several simulations show how this smog could be only an easily observed, local manifestation of a much broader increase in tropospheric ozone. We illustrate basic processes with a one-dimensional time-dependent model that is closer to true meteorological motions than commonly used eddy diffusion models. Its application to a representative region of South America gives reasonable simulations of the local pollutants measured there. Three illustrative simulations indicate the importance of dilution, principally due to vertical transport, in increasing the efficiency of ozone production, possibly enough for high ozone to be apparent on a very large, intercontinental scale. In the first, cook-then-mix, simulation the nitrogen oxides and other burning-produced pollutants are confined to a persistently subsident fair weather boundary layer for several days, and the resultant ozone is found to have only a transient influence on the whole column of tropospheric ozone. In the second, mix-then-cook, simulation the effect of typical cumulonimbus convection, which vents an actively polluted boundary layer, is to make a persistent increase in the tropical ozone column. Such a broadly increased ozone column is observed over the the populated "continental" portion of the tropics. A third simulation averages all emission, transport, and deposition parameters, representing one column in a global tropospheric model that does not simulate individual weather events. This "oversmoothing" simulation produces 60% more ozone than observed or otherwise modeled. Qualitatively similar overprediction is suggested for all models which average significantly in time or space, as all need do. Clearly, simulating these O3 levels will depend sensitively on knowledge of the timing of emissions and transport.

Characteristics of Surface Ozone in Agra, a Sub-urban site in Indo ...

Indian Academy of Sciences (India)

65

Department of Chemistry, Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra. 4. 282110, India ... location in the atmosphere, O3 can influence human health and climate; in the stratosphere, O3. 51 ...... ozone exposure: reconciling science and standard setting in the United States, Europe, and Asia;. 582.

The effect of ozone and open air factor on surface-attached and biofilm environmental Listeria monocytogenes.

Science.gov (United States)

Nicholas, R; Dunton, P; Tatham, A; Fielding, L

2013-08-01

The effects of gaseous ozone and open air factor (OAF) on environmental Listeria monocytogenes attached to three common food contact surfaces were investigated. Listeria monocytogenes on different food contact surfaces was treated with ozone and OAF. Microbiological counts, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed. Ozone at 10 ppm gave <1-log reduction when L. monocytogenes was attached to stainless steel, while 45 ppm gave a log reduction of 3.41. OAF gave better log reductions than 10 ppm ozone, but lower log reductions than 45 ppm. Significant differences were found between surfaces. Biofilm organisms were significantly more resistant than those surface attached on stainless steel. SEM and AFM demonstrated different membrane and cell surface modifications following ozone or OAF treatment. The strain used demonstrated higher resistance to ozone than previous studies. This may be due to the fact that it was isolated from a food manufacturing premises that used oxidizing disinfectants. OAF was more effective at reducing the levels of the organism than an ozone concentration of 10 ppm. Pathogen management strategies must account for resistance of environmental strains when validating cleaning and disinfection. OAF has shown potential for surface decontamination compared with ozone. SEM and AFM are valuable tools for determining mechanisms of action of antimicrobial agents. © 2013 The Society for Applied Microbiology.

Oxygen vacancies enabled enhancement of catalytic property of Al reduced anatase TiO{sub 2} in the decomposition of high concentration ozone

Energy Technology Data Exchange (ETDEWEB)

Ding, Yanhua; Zhang, Xiaolei [Shanghai Institute of Technology, Shanghai 200235 (China); Chen, Li [East China Normal University, Shanghai 200062 (China); Wang, Xiaorui [Shanghai Institute of Technology, Shanghai 200235 (China); Zhang, Na, E-mail: nzhang@sit.edu.cn [Shanghai Institute of Technology, Shanghai 200235 (China); Liu, Yufeng [Shanghai Institute of Technology, Shanghai 200235 (China); Fang, Yongzheng, E-mail: fyz1003@sina.com [Shanghai Institute of Technology, Shanghai 200235 (China)

2017-06-15

The catalytic decomposition of gaseous ozone (O{sub 3}) is investigated using anatase TiO{sub 2} (A-TiO{sub 2}) and Aluminum-reduced A-TiO{sub 2} (ARA-TiO{sub 2}) at high concentration and high relative humidity (RH) without light illumination. Compared with the pristine A-TiO{sub 2}, the ARA-TiO{sub 2} sample possesses a unique crystalline core-amorphous shell structure. It is proved to be an excellent solar energy “capture” for solar thermal collectors due to lots of oxygen vacancies. The results indicate that the overall decomposition efficiency of O{sub 3} without any light irradiation has been greatly improved from 4.8% on A-TiO{sub 2} to 100% on ARA-TiO{sub 2} under the RH=100% condition. The ozone conversion over T500/ARA-TiO{sub 2} catalyst is still maintained at 95% after a 72 h test under the reaction condition of 18.5 g/m{sup 3} ozone initial concentration, and RH=90%. The results can be explained that T500/ARA-TiO{sub 2} possesses the largest amorphous contour, the lowest crystallinity, the most surface-active Ti{sup 3+}/T{sup i4+}couples, and the most oxygen vacancies. This result opens a new door to widen the application of TiO{sub 2} in the thermal-catalytic field. - Graphical abstract: The anatase-TiO{sub 2} with various oxidation states and oxygen vacancies have been obtained by aluminum-reduction, and the decomposition efficiency of O{sub 3} has been greatly improved from 4.8% to 100% without irradiation under the RH=100% condition. - Highlights: • The decomposition of gaseous ozone over Al reduced TiO2 (ARA-TiO{sub 2}) is firstly reported. • The decomposition efficiency is up to 100% without any light irradiation on ARA-TiO{sub 2} under RH=100% condition. • The ozone conversion is maintained at 95% after a 72 h test, when C{sub inlet}=18.5 g/m{sup 3} and RH=90%.

Effect of solar radiation on surface ozone in Cairo

Energy Technology Data Exchange (ETDEWEB)

Rizk, H F.S. [National Research Centre, Air Pollution Research Dept., Cairo (Egypt)

1992-04-01

Measurements of surface ozone content over an urban area in Cairo were conducted during a year, May 1989 to April 1990, while solar radiation at the same area was measured. Low and high concentrations of ozone are compared with those recommended by the WHO expert committee regarding the daily cycle of ozone concentration. 15 refs.

On the O2(a1Δ) quenching by vibrationally excited ozone

Science.gov (United States)

Azyazov, V. N.; Mikheyev, P. A.; Heaven, M. C.

2010-09-01

The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen (O2(a)) in electric discharge. It is important to understand the mechanisms by which O2(a) is quenched in these devices. To gain understanding of this mechanisms quenching of O2(a) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a) quenching were followed by observing the 1268 nm fluorescence of the O2 a --> X transition. Fast quenching of O2(a) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

Ozone (O{sub 3}) elicits neurotoxicity in spinal cord neurons (SCNs) by inducing ER Ca{sup 2+} release and activating the CaMKII/MAPK signaling pathway

Energy Technology Data Exchange (ETDEWEB)

Li, Yun; Lin, Xiaowen; Zhao, XueJun; Xie, Juntian; JunNan, Wang; Sun, Tao; Fu, Zhijian, E-mail: zhijian_fu@163.com

2014-11-01

Ozone (O{sub 3}) is widely used in the treatment of spinal cord related diseases. Excess or accumulation of this photochemical air can however be neurotoxic. In this study, in vitro cultured Wister rat spinal cord neurons (SCNs) were used to investigate the detrimental effects and underlying mechanisms of O{sub 3}. Ozone in a dose-dependent manner inhibited cell viability at a range of 20 to 500 μg/ml, with the dose at 40 μg/ml resulting in a decrease of cell viability to 75%. The cell death after O{sub 3} exposure was related to endoplasmic reticulum (ER) calcium (Ca{sup 2+}) release. Intracellular Ca{sup 2+} chelator, ER stabilizer (inositol 1,4,5-trisphosphate receptor (IP3R) antagonist and ryanodine receptor (RyR) antagonist) and calcium/calmodulin-dependent protein kinase II (CaMKII) antagonist could effectively block Ca{sup 2+} mobilization and inhibit cell death following 40 μg/ml O{sub 3} exposure. In addition, ER Ca{sup 2+} release due to O{sub 3} exposure enhanced phospho-p38 and phospho-JNK levels and apoptosis of SCNs through activating CaMKII. Based on these results, we confirm that ozone elicits neurotoxicity in SCNs via inducing ER Ca{sup 2+} release and activating CaMKII/MAPK signaling pathway. Therefore, physicians should get attention to the selection of treatment concentrations of oxygen/ozone. And, approaches, such as chelating intracellular Ca{sup 2+} and stabilizing neuronal Ca{sup 2+} homeostasis could effectively ameliorate the neurotoxicity of O{sub 3}. - Highlights: • Exposure to O{sub 3} can reduce the viability of SCNs and cause the cell death. • Exposure to O{sub 3} can trigger RyR and IP3R dependent intracellular Ca{sup 2+} release. • Exposure to O{sub 3} can enhance the phospho-CaMKII, phospho-JNK and phospho-p38 levels.

Ozone and meteorological boundary-layer conditions at Summit, Greenland, during 3-21 June 2000

Energy Technology Data Exchange (ETDEWEB)

Helmig, D.; Boulter, J.; David, D.; Birks, J.W.; Cullen, N.J.; Steffen, K. [University of Colorado, Boulder, CO (United States). Cooperative Institute for Research in Environmental Sciences; Johnson, B.J.; Oltmans, S.J. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Climate Monitoring and Diagnostics Laboratory

2002-06-01

The temporal and spatial distributions of boundary-layer ozone were studied during June 2000 at Summit, Greenland, using surface-level measurements and vertical profiling from a tethered balloon platform. Three weeks of continuous ozone surface data, 133 meteorological vertical profile data and 82 ozone vertical profile data sets were collected from the surface to a maximum altitude of 1400 m above ground. The lower atmosphere at Summit was characterized by the prevalence of strong stable conditions with strong surface temperature inversions. These inversions reversed to neutral to slightly unstable conditions between {approx} 9.00 and 18.00 h local time with the formation of shallow mixing heights of {approx} 70-250 m above the surface. The surface ozone mixing ratio ranged from 39 to 68 ppbv and occasionally had rapid changes of up to 20 ppb in 12 h. The diurnal mean ozone mixing ratio showed diurnal trends indicating meteorological and photochemical controls of surface ozone. Vertical profiles were within the range of 37-76 ppb and showed strong stratification in the lower troposphere. A high correlation of high ozone/low water vapor air masses indicated the transport of high tropospheric/low stratospheric air into the lower boundary layer. An {approx} 0.1-3 ppb decline of the ozone mixing ratio towards the surface was frequently observed within the neutrally stable mixed layer during midday hours. These data suggest that the boundary-layer ozone mixing ratio and ozone depletion and deposition to the snowpack are influenced by the boundary-layer ozone mixing ratio and ozone depletion and deposition to the snowpack are influenced by photochemical processes and/or transport phenomena that follow diurnal dependencies. With 37 ppb of ozone being the lowest mixing ratio measured in all data no evidence was seen for the occurrence of ozone depletion episodes similar to those that have been reported within the boundary layer at coastal Arctic sites during springtime

Spatial clustering and meteorological drivers of summer ozone in Europe

Science.gov (United States)

Carro-Calvo, Leopoldo; Ordóñez, Carlos; García-Herrera, Ricardo; Schnell, Jordan L.

2017-04-01

We present a regionalization of summer near-surface ozone (O3) in Europe. For this purpose we apply a K-means algorithm on a gridded MDA8 O3 (maximum daily average 8-h ozone) dataset covering a European domain [15° W - 30° E, 35°-70° N] at 1° x 1° horizontal resolution for the 1998-2012 period. This dataset was compiled by merging observations from the European Monitoring and Evaluation Programme (EMEP) and the European Environment Agency's air quality database (AirBase). The K-means method allows identifying sets of different regions where the O3 concentrations present coherent spatiotemporal patterns and are thus expected to be driven by similar meteorological factors. After some testing, 9 regions were selected: the British Isles, North-Central Europe, Northern Scandinavia, the Baltic countries, the Iberian Peninsula, Western Europe, South-Central Europe, Eastern Europe and the Balkans. For each region we examine the synoptic situations associated with elevated ozone extremes (days exceeding the 95th percentile of the summer MDA8 O3 distribution). Our analyses reveal that there are basically two different kinds of regions in Europe: (a) those in the centre and south of the continent where ozone extremes are associated with elevated temperature within the same region and (b) those in northern Europe where ozone extremes are driven by southerly advection of air masses from warmer, more polluted areas. Even when the observed patterns were initially identified only for days registering high O3 extremes, all summer days can be projected on such patterns to identify the main modes of meteorological variability of O3. We have found that such modes are partly responsible for the day-to-day variability in the O3 concentrations and can explain a relatively large fraction (from 44 to 88 %, depending on the region) of the interannual variability of summer mean MDA8 O3 during the period of analysis. On the other hand, some major teleconnection patterns have been tested

Detoxification and repair process of ozone injury: From O{sub 3} uptake to gene expression adjustment

Energy Technology Data Exchange (ETDEWEB)

Castagna, A., E-mail: castagna@agr.unipi.i [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy); Ranieri, A., E-mail: aranieri@agr.unipi.i [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy)

2009-05-15

Plants react to O{sub 3} threat by setting up a variety of defensive strategies involving the co-ordinated modulation of stress perception, signalling and metabolic responses. Although stomata largely controls O{sub 3} uptake, differences in O{sub 3} tolerance cannot always be ascribed to changes in stomatal conductance but cell protective and repair processes should be taken into account. O{sub 3}-driven ROS production in the apoplast induces a secondary, active, self-propagating generation of ROS, whose levels must be finely tuned, by many enzymatic and non-enzymatic antioxidant systems, to induce gene activation without determining uncontrolled cell death. Additional signalling molecules, as ethylene, jasmonic and salicylic acid are also crucial to determine the spreading and the containment of leaf lesions. The main recent results obtained on O{sub 3} sensing, signal transduction, ROS formation and detoxification mechanisms are here discussed. - A dissection of the complex network of interacting mechanisms which determine the cell fate under ozone stress.

Variability of surface ozone with cloud coverage over Kolkata, India

Indian Academy of Sciences (India)

Critical analysis of experimental surface ozone data and cloud coverage is reported over Kolkata during the period January 2011 to December 2011. Significant relationship between these two parameters is observed. Analysis shows that the trend of surface ozone concentration and cloud coverage follow opposite ...

Coincident Observations of Surface Ozone and NMVOCs over Abu Dhabi

Science.gov (United States)

Abbasi, Naveed; Majeed, Tariq; Iqbal, Mazhar; Tarasick, David; Davies, Jonathan; Riemer, Daniel; Apel, Eric

2016-07-01

The vertical profiles of ozone are measured coincidently with non-methane volatile organic compounds (NMVOCs) at the meteorological site located at the Abu Dhabi international airport (latitude 24.45N; longitude 54.22E) during the years 2012 - 2014. Some of the profiles show elevated surface ozone >95 ppbv during the winter months (December, January and February). The ground-level NMVOCs obtained from the gas chromatography-flame ionization detection/mass spectrometry system also show elevated values of acetylene, ethane, propane, butane, pentane, benzene, and toluene. NMVOCs and ozone abundances in other seasons are much lower than the values in winter season. NMVOCs are emitted from an extensive number of sources in urban environments including fuel production, distribution, and consumption, and serve as precursor of ozone. Transport sources contribute a substantial portion of the NMVOC burden to the urban atmosphere in developed regions. Abu Dhabi is located at the edge of the Arabian Gulf and is highly affected by emissions from petrochemical industries in the neighboring Gulf region. The preliminary results indicate that wintertime enhancement in ozone is associated with large values of NMVOCs at Abu Dhabi. The domestic production of surface ozone is estimated from the combination of oxygen recombination and NMVOCs and compared with the data. It is estimated that about 40-50% of ozone in Abu Dhabi is transported from the neighbouring petrochemical industries. We will present ozone sounding and NMVOCs data and our model estimates of surface ozone, including a discussion on the high levels of the tropospheric ozone responsible for contaminating the air quality in the UAE. This work is supported by National Research Foundation, UAE.

Reaction of a phospholipid monolayer with gas-phase ozone at the air-water interface: measurement of surface excess and surface pressure in real time.

Science.gov (United States)

Thompson, Katherine C; Rennie, Adrian R; King, Martin D; Hardman, Samantha J O; Lucas, Claire O M; Pfrang, Christian; Hughes, Brian R; Hughes, Arwel V

2010-11-16

The reaction between gas-phase ozone and monolayers of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, on aqueous solutions has been studied in real time using neutron reflection and surface pressure measurements. The reaction between ozone and lung surfactant, which contains POPC, leads to decreased pulmonary function, but little is known about the changes that occur to the interfacial material as a result of oxidation. The results reveal that the initial reaction of ozone with POPC leads to a rapid increase in surface pressure followed by a slow decrease to very low values. The neutron reflection measurements, performed on an isotopologue of POPC with a selectively deuterated palmitoyl strand, reveal that the reaction leads to loss of this strand from the air-water interface, suggesting either solubilization of the product lipid or degradation of the palmitoyl strand by a reactive species. Reactions of (1)H-POPC on D(2)O reveal that the headgroup region of the lipids in aqueous solution is not dramatically perturbed by the reaction of POPC monolayers with ozone supporting degradation of the palmitoyl strand rather than solubilization. The results are consistent with the reaction of ozone with the oleoyl strand of POPC at the air-water interface leading to the formation of OH radicals. The highly reactive OH radicals produced can then go on to react with the saturated palmitoyl strands leading to the formation of oxidized lipids with shorter alkyl tails.

Electronic properties and surface reactivity of SrO-terminated SrTiO3 and SrO-terminated iron-doped SrTiO3.

Science.gov (United States)

Staykov, Aleksandar; Tellez, Helena; Druce, John; Wu, Ji; Ishihara, Tatsumi; Kilner, John

2018-01-01

Surface reactivity and near-surface electronic properties of SrO-terminated SrTiO 3 and iron doped SrTiO 3 were studied with first principle methods. We have investigated the density of states (DOS) of bulk SrTiO 3 and compared it to DOS of iron-doped SrTiO 3 with different oxidation states of iron corresponding to varying oxygen vacancy content within the bulk material. The obtained bulk DOS was compared to near-surface DOS, i.e. surface states, for both SrO-terminated surface of SrTiO 3 and iron-doped SrTiO 3 . Electron density plots and electron density distribution through the entire slab models were investigated in order to understand the origin of surface electrons that can participate in oxygen reduction reaction. Furthermore, we have compared oxygen reduction reactions at elevated temperatures for SrO surfaces with and without oxygen vacancies. Our calculations demonstrate that the conduction band, which is formed mainly by the d-states of Ti, and Fe-induced states within the band gap of SrTiO 3 , are accessible only on TiO 2 terminated SrTiO 3 surface while the SrO-terminated surface introduces a tunneling barrier for the electrons populating the conductance band. First principle molecular dynamics demonstrated that at elevated temperatures the surface oxygen vacancies are essential for the oxygen reduction reaction.

Evaluating a Space-Based Indicator of Surface Ozone-NO x -VOC Sensitivity Over Midlatitude Source Regions and Application to Decadal Trends.

Science.gov (United States)

Jin, Xiaomeng; Fiore, Arlene M; Murray, Lee T; Valin, Lukas C; Lamsal, Lok N; Duncan, Bryan; Boersma, K Folkert; De Smedt, Isabelle; Abad, Gonzalo Gonzalez; Chance, Kelly; Tonnesen, Gail S

2017-10-16

Determining effective strategies for mitigating surface ozone (O 3 ) pollution requires knowledge of the relative ambient concentrations of its precursors, NO x , and VOCs. The space-based tropospheric column ratio of formaldehyde to NO 2 (FNR) has been used as an indicator to identify NO x -limited versus NO x -saturated O 3 formation regimes. Quantitative use of this indicator ratio is subject to three major uncertainties: (1) the split between NO x -limited and NO x -saturated conditions may shift in space and time, (2) the ratio of the vertically integrated column may not represent the near-surface environment, and (3) satellite products contain errors. We use the GEOS-Chem global chemical transport model to evaluate the quantitative utility of FNR observed from the Ozone Monitoring Instrument over three northern midlatitude source regions. We find that FNR in the model surface layer is a robust predictor of the simulated near-surface O 3 production regime. Extending this surface-based predictor to a column-based FNR requires accounting for differences in the HCHO and NO 2 vertical profiles. We compare four combinations of two OMI HCHO and NO 2 retrievals with modeled FNR. The spatial and temporal correlations between the modeled and satellite-derived FNR vary with the choice of NO 2 product, while the mean offset depends on the choice of HCHO product. Space-based FNR indicates that the spring transition to NO x -limited regimes has shifted at least a month earlier over major cities (e.g., New York, London, and Seoul) between 2005 and 2015. This increase in NO x sensitivity implies that NO x emission controls will improve O 3 air quality more now than it would have a decade ago.

WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms

Directory of Open Access Journals (Sweden)

A. Sharma

2017-12-01

Full Text Available We evaluate numerical simulations of surface ozone mixing ratios over the south Asian region during the pre-monsoon season, employing three different emission inventories in the Weather Research and Forecasting model with Chemistry (WRF-Chem with the second-generation Regional Acid Deposition Model (RADM2 chemical mechanism: the Emissions Database for Global Atmospheric Research – Hemispheric Transport of Air Pollution (EDGAR-HTAP, the Intercontinental Chemical Transport Experiment phase B (INTEX-B and the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS. Evaluation of diurnal variability in modelled ozone compared to observational data from 15 monitoring stations across south Asia shows the model ability to reproduce the clean, rural and polluted urban conditions over this region. In contrast to the diurnal average, the modelled ozone mixing ratios during noontime, i.e. hours of intense photochemistry (11:30–16:30 IST – Indian Standard Time – UTC +5:30, are found to differ among the three inventories. This suggests that evaluations of the modelled ozone limited to 24 h average are insufficient to assess uncertainties associated with ozone buildup. HTAP generally shows 10–30 ppbv higher noontime ozone mixing ratios than SEAC4RS and INTEX-B, especially over the north-west Indo-Gangetic Plain (IGP, central India and southern India. The HTAP simulation repeated with the alternative Model for Ozone and Related Chemical Tracers (MOZART chemical mechanism showed even more strongly enhanced surface ozone mixing ratios due to vertical mixing of enhanced ozone that has been produced aloft. Our study indicates the need to also evaluate the O3 precursors across a network of stations and the development of high-resolution regional inventories for the anthropogenic emissions over south Asia accounting for year-to-year changes to further reduce uncertainties in modelled ozone over this region.

WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms

Science.gov (United States)

Sharma, Amit; Ojha, Narendra; Pozzer, Andrea; Mar, Kathleen A.; Beig, Gufran; Lelieveld, Jos; Gunthe, Sachin S.

2017-12-01

We evaluate numerical simulations of surface ozone mixing ratios over the south Asian region during the pre-monsoon season, employing three different emission inventories in the Weather Research and Forecasting model with Chemistry (WRF-Chem) with the second-generation Regional Acid Deposition Model (RADM2) chemical mechanism: the Emissions Database for Global Atmospheric Research - Hemispheric Transport of Air Pollution (EDGAR-HTAP), the Intercontinental Chemical Transport Experiment phase B (INTEX-B) and the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS). Evaluation of diurnal variability in modelled ozone compared to observational data from 15 monitoring stations across south Asia shows the model ability to reproduce the clean, rural and polluted urban conditions over this region. In contrast to the diurnal average, the modelled ozone mixing ratios during noontime, i.e. hours of intense photochemistry (11:30-16:30 IST - Indian Standard Time - UTC +5:30), are found to differ among the three inventories. This suggests that evaluations of the modelled ozone limited to 24 h average are insufficient to assess uncertainties associated with ozone buildup. HTAP generally shows 10-30 ppbv higher noontime ozone mixing ratios than SEAC4RS and INTEX-B, especially over the north-west Indo-Gangetic Plain (IGP), central India and southern India. The HTAP simulation repeated with the alternative Model for Ozone and Related Chemical Tracers (MOZART) chemical mechanism showed even more strongly enhanced surface ozone mixing ratios due to vertical mixing of enhanced ozone that has been produced aloft. Our study indicates the need to also evaluate the O3 precursors across a network of stations and the development of high-resolution regional inventories for the anthropogenic emissions over south Asia accounting for year-to-year changes to further reduce uncertainties in modelled ozone over this region.

Sequential disinfection of E. coli O157:H7 on shredded lettuce leaves by aqueous chlorine dioxide, ozonated water, and thyme essential oil

Science.gov (United States)

Singh, Nepal; Singh, Rakesh K.; Bhunia, Arun K.; Stroshine, Richard L.; Simon, James E.

2001-03-01

There have been numerous studies on effectiveness of different sanitizers for microbial inactivation. However, results obtained from different studies indicate that microorganism cannot be easily removed from fresh cut vegetables because of puncture and cut surfaces with varying surface topographies. In this study, three step disinfection approach was evaluated for inactivation of E. coli O157:H7 on shredded lettuce leaves. Sequential application of thyme oil, ozonated water, and aqueous chlorine dioxide was evaluated in which thyme oil was applied first followed by ozonated water and aqueous chlorine dioxide. Shredded lettuce leaves inoculated with cocktail culture of E. coli O157:H7 (C7927, EDL 933 and 204 P), were washed with ozonated water (15 mg/l for 10min), aqueous chlorine dioxide (10 mg/l,for 10min) and thyme oil suspension (0.1%, v/v for 5min). Washing of lettuce leaves with ozonated water, chlorine dioxide and thyme oil suspension resulted in 0.44, 1.20, and 1.46 log reduction (log10 cfu/g), respectively. However, the sequential treatment achieved approximately 3.13 log reductions (log10 cfu/g). These results demonstrate the efficacy of sequential treatments in decontaminating shredded lettuce leaves containing E. coli O157:H7.

Why do Models Overestimate Surface Ozone in the Southeastern United States?

Science.gov (United States)

Travis, Katherine R.; Jacob, Daniel J.; Fisher, Jenny A.; Kim, Patrick S.; Marais, Eloise A.; Zhu, Lei; Yu, Karen; Miller, Christopher C.; Yantosca, Robert M.; Sulprizio, Melissa P.; Thompson, Anne M.; Wennberg, Paul O.; Crounse, John D.; St Clair, Jason M.; Cohen, Ronald C.; Laughner, Joshua L.; Dibb, Jack E.; Hall, Samuel R.; Ullmann, Kirk; Wolfe, Glenn M.; Pollack, Illana B.; Peischl, Jeff; Neuman, Jonathan A.; Zhou, Xianliang

2018-01-01

Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°×0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30–60%, dependent on the assumption of the contribution by soil NOx emissions. Upper tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft, and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 8±13 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease

Why do models overestimate surface ozone in the Southeast United States?

Directory of Open Access Journals (Sweden)

K. R. Travis

2016-11-01

Full Text Available Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx  ≡  NO + NO2 and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°  ×  0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI for NOx from the US Environmental Protection Agency (EPA is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30–60 %, dependent on the assumption of the contribution by soil NOx emissions. Upper-tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 6 ± 14 ppb relative to observed surface ozone in the Southeast US. Ozonesondes

Why do Models Overestimate Surface Ozone in the Southeastern United States?

Science.gov (United States)

Travis, Katherine R.; Jacob, Daniel J.; Fisher, Jenny A.; Kim, Patrick S.; Marais, Eloise A.; Zhu, Lei; Yu, Karen; Miller, Christopher C.; Yantosca, Robert M.; Sulprizio, Melissa P.;

Springtime high surface ozone events over the western United States: Quantifying the role of stratospheric intrusions

Science.gov (United States)

Fiore, A. M.; Lin, M.; Cooper, O. R.; Horowitz, L. W.; Naik, V.; Levy, H.; Langford, A. O.; Johnson, B. J.; Oltmans, S. J.; Senff, C. J.

2011-12-01

As the National Ambient Air Quality (NAAQS) standard for ozone (O_{3}) is lowered, it pushes closer to policy-relevant background levels (O_{3} concentrations that would exist in the absence of North American anthropogenic emissions), making attainment more difficult with local controls. We quantify the Asian and stratospheric components of this North American background, with a primary focus on the western United States. Prior work has identified this region as a hotspot for deep stratospheric intrusions in spring. We conduct global simulations at 200 km and 50 km horizontal resolution with the GFDL AM3 model, including a stratospheric O_{3} tracer and two sensitivity simulations with anthropogenic emissions from Asia and North America turned off. The model is evaluated with a suite of in situ and satellite measurements during the NOAA CalNex campaign (May-June 2010). The model reproduces the principle features in the observed surface to near tropopause distribution of O_{3} along the California coast, including its latitudinal variation and the development of regional high-O_{3} episodes. Four deep tropopause folds are diagnosed and we find that the remnants of these stratospheric intrusions are transported to the surface of Southern California and Western U.S. Rocky Mountains, contributing 10-30 ppbv positive anomalies relative to the simulated campaign mean stratospheric component in the model surface layer. We further examine the contribution of North American background, including its stratospheric and Asian components, to the entire distribution of observed MDA8 O_{3} at 12 high-elevation CASTNet sites in the Mountain West. We find that the stratospheric O_{3} tracer constitutes 50% of the North American background, and can enhance surface maximum daily 8-hour average (MDA8) O_{3} by 20 ppb when observed surface O_{3} is in the range of 60-80 ppbv. Our analysis highlights the potential for natural sources such as deep stratospheric intrusions to contribute

Surface ozone seasonality under global change: Influence from dry deposition and isoprene emissions at northern mid-latitudes

Science.gov (United States)

Clifton, O.; Paulot, F.; Fiore, A. M.; Horowitz, L. W.; Malyshev, S.; Shevliakova, E.; Correa, G. J. P.; Lin, M.

2017-12-01

Identifying the contributions of nonlinear chemistry and transport to observed surface ozone seasonal cycles over land using global models relies on an accurate representation of ozone uptake by vegetation (dry deposition). It is well established that in the absence of ozone precursor emission changes, a warming climate will increase surface ozone in polluted regions, and that a rise in temperature-dependent isoprene emissions would exacerbate this "climate penalty". However, the influence of changes in ozone dry deposition, expected to evolve with climate and land use, is often overlooked in air quality projections. With a new scheme that represents dry deposition within the NOAA GFDL dynamic vegetation land model (LM3) coupled to the NOAA GFDL atmospheric chemistry-climate model (AM3), we simulate the impact of 21st century climate and land use on ozone dry deposition and isoprene emissions. This dry deposition parameterization is a version of the Wesely scheme, but uses parameters explicitly calculated by LM3 that respond to climate and land use (e.g., stomatal conductance, canopy interception of water, leaf area index). The parameterization includes a nonstomatal deposition dependence on humidity. We evaluate climatological present-day seasonal cycles of ozone deposition velocities and abundances with those observed at northern mid-latitude sites. With a set of 2010s and 2090s decadal simulations under a high climate warming scenario (RCP8.5) and a sensitivity simulation with well-mixed greenhouse gases following RCP8.5 but air pollutants held at 2010 levels (RCP8.5_WMGG), we examine changes in surface ozone seasonal cycles. We build on our previous findings, which indicate that strong reductions in anthropogenic NOx emissions under RCP8.5 cause the surface ozone seasonal cycle over the NE USA to reverse, shifting from a summer peak at present to a winter peak by 2100. Under RCP8.5_WMGG, we parse the separate effects of climate and land use on ozone dry

Enhanced photocatalytic ozonation of organics by g-C3N4 under visible light irradiation

International Nuclear Information System (INIS)

Liao, Gaozu; Zhu, Dongyun; Li, Laisheng; Lan, Bingyan

2014-01-01

Highlights: • g-C 3 N 4 is employed as active catalyst in the photocatalytic ozonation system. • The more negative conduction band of g-C 3 N 4 benefits the transfer of electrons. • The synergistic effect between photocatalysis and ozonation is promoted by g-C 3 N 4 . • Enhanced degradation of oxalic acid and biphenol A is achieved via g-C 3 N 4 /Vis/O 3 . - Abstract: Graphitic carbon nitride (g-C 3 N 4 ) was employed as the active photocatalyst in the photocatalytic ozonation coupling system in the present study. g-C 3 N 4 was prepared by directly heating thiourea in air at 550 °C. XRD, FT-IR, UV–vis was used to characterize the structure and optical property. Oxalic acid and bisphenol A were selected as model substances for photocatalytic ozonation reactions to evaluate the catalytic ability of g-C 3 N 4 (g-C 3 N 4 /Vis/O 3 ). The results showed that the degradation ratio of oxalic acid with g-C 3 N 4 /Vis/O 3 was 65.2% higher than the sum of ratio when it was individually decomposed by g-C 3 N 4 /Vis and O 3 . The TOC removal of biphenol A with g-C 3 N 4 /Vis/O 3 was 2.17 times as great as the sum of the ratio when using g-C 3 N 4 /Vis and O 3 . This improvement was attributed to the enhanced synergistic effect between photocatalysis and ozonation by g-C 3 N 4 . Under visible light irradiation, the photo-generated electrons produced on g-C 3 N 4 facilitated the electrons transfer owing to the more negative conduction band potential (−1.3 V versus NHE). It meant that the photo-generated electrons could be trapped by ozone and reaction with it more easily. Subsequently, the yield of hydroxyl radicals was improved so as to enhance the organics degradation efficiency. This work indicated that metal-free g-C 3 N 4 could be an excellent catalyst for mineralization of organic compounds in waste control

Insights into the Electronic Structure of Ozone and Sulfur Dioxide from Generalized Valence Bond Theory: Bonding in O3 and SO2.

Science.gov (United States)

Takeshita, Tyler Y; Lindquist, Beth A; Dunning, Thom H

2015-07-16

There are many well-known differences in the physical and chemical properties of ozone (O3) and sulfur dioxide (SO2). O3 has longer and weaker bonds than O2, whereas SO2 has shorter and stronger bonds than SO. The O-O2 bond is dramatically weaker than the O-SO bond, and the singlet-triplet gap in SO2 is more than double that in O3. In addition, O3 is a very reactive species, while SO2 is far less so. These disparities have been attributed to variations in the amount of diradical character in the two molecules. In this work, we use generalized valence bond (GVB) theory to characterize the electronic structure of ozone and sulfur dioxide, showing O3 does indeed possess significant diradical character, whereas SO2 is effectively a closed shell molecule. The GVB results provide critical insights into the genesis of the observed difference in these two isoelectronic species. SO2 possesses a recoupled pair bond dyad in the a"(π) system, resulting in SO double bonds. The π system of O3, on the other hand, has a lone pair on the central oxygen atom plus a pair of electrons in orbitals on the terminal oxygen atoms that give rise to a relatively weak π interaction.

Observation of enhanced ozone in an electrically active storm over Socorro, NM: Implications for ozone production from corona discharges

Science.gov (United States)

Minschwaner, K.; Kalnajs, L. E.; Dubey, M. K.; Avallone, L. M.; Sawaengphokai, P. C.; Edens, H. E.; Winn, W. P.

2008-09-01

Enhancements in ozone were observed between about 3 and 10 km altitude within an electrically active storm in central New Mexico. Measurements from satellite sensors and ground-based radar show cloud top pressures between 300 and 150 mb in the vicinity of an ozonesonde launched from Socorro, NM, and heavy precipitation with radar reflectivities exceeding 50 dBZ. Data from a lightning mapping array and a surface electric field mill show a large amount of electrical activity within this thunderstorm. The observed ozone enhancements are large (50% above the mean) and could have resulted from a number of possible processes, including the advection of polluted air from the urban environments of El Paso and Juarez, photochemical production by lightning-generated NOx from aged thunderstorm outflow, downward mixing of stratospheric air, or local production from within the thunderstorm. We find that a large fraction of the ozone enhancement is consistent with local production from corona discharges, either from cloud particles or by corona associated with lightning. The implied global source of ozone from thunderstorm corona discharge is estimated to be 110 Tg O3 a-1 with a range between 40 and 180 Tg O3 a-1. This value is about 21% as large as the estimated ozone production rate from lightning NOx, and about 3% as large as the total chemical production rate of tropospheric ozone. Thus while the estimated corona-induced production of ozone may be significant on local scales, it is unlikely to be as important to the global ozone budget as other sources.

Catalytic ozonation of fenofibric acid over alumina-supported manganese oxide

Energy Technology Data Exchange (ETDEWEB)

Rosal, Roberto, E-mail: roberto.rosal@uah.es [Departamento de Quimica Analitica e Ingenieria Quimica, Universidad de Alcala, E-28771 Alcala de Henares (Spain); Gonzalo, Maria S.; Rodriguez, Antonio; Garcia-Calvo, Eloy [Departamento de Quimica Analitica e Ingenieria Quimica, Universidad de Alcala, E-28771 Alcala de Henares (Spain)

2010-11-15

The catalytic ozonation of fenofibric acid was studied using activated alumina and alumina-supported manganese oxide in a semicontinuous reactor. The rate constants at 20 deg. C for the non-catalytic reaction of fenofibric acid with ozone and hydroxyl radicals were 3.43 {+-} 0.20 M{sup -1} s{sup -1} and (6.55 {+-} 0.33) x 10{sup 9} M{sup -1} s{sup -1}, respectively. The kinetic constant for the catalytic reaction between fenofibric acid and hydroxyl radicals did not differ significantly from that of homogeneous ozonation, either using Al{sub 2}O{sub 3} or MnO{sub x}/Al{sub 2}O{sub 3}. The results showed a considerable increase in the generation of hydroxyl radicals due to the use of catalysts even in the case of catalytic runs performed using a real wastewater matrix. Both catalysts promoted the decomposition of ozone in homogeneous phase, but the higher production of hydroxyl radicals corresponded to the catalyst with more activity in terms of ozone decomposition. We did not find evidence of the catalysts having any effect on rate constants, which suggests that the reaction may not involve the adsorption of organics on catalyst surface.

Sensitivity of the OMI ozone profile retrieval (OMO3PR) to a priori assumptions

NARCIS (Netherlands)

Mielonen, T.; De Haan, J.F.; Veefkind, J.P.

2014-01-01

We have assessed the sensitivity of the operational OMI ozone profile retrieval (OMO3PR) algorithm to a number of a priori assumptions. We studied the effect of stray light correction, surface albedo assumptions and a priori ozone profiles on the retrieved ozone profile. Then, we studied how to

Electrical properties of GaN-based metal-insulator-semiconductor structures with Al2O3 deposited by atomic layer deposition using water and ozone as the oxygen precursors

Science.gov (United States)

Kubo, Toshiharu; Freedsman, Joseph J.; Iwata, Yasuhiro; Egawa, Takashi

2014-04-01

Al2O3 deposited by atomic layer deposition (ALD) was used as an insulator in metal-insulator-semiconductor (MIS) structures for GaN-based MIS-devices. As the oxygen precursors for the ALD process, water (H2O), ozone (O3), and both H2O and O3 were used. The chemical characteristics of the ALD-Al2O3 surfaces were investigated by x-ray photoelectron spectroscopy. After fabrication of MIS-diodes and MIS-high-electron-mobility transistors (MIS-HEMTs) with the ALD-Al2O3, their electrical properties were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The threshold voltage of the C-V curves for MIS-diodes indicated that the fixed charge in the Al2O3 layer is decreased when using both H2O and O3 as the oxygen precursors. Furthermore, MIS-HEMTs with the H2O + O3-based Al2O3 showed good dc I-V characteristics without post-deposition annealing of the ALD-Al2O3, and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.

Effect of Climate Change on Surface Ozone over North America, Europe, and East Asia

Science.gov (United States)

Schnell, Jordan L.; Prather, Michael J.; Josse, Beatrice; Naik, Vaishali; Horowitz, Larry W.; Zeng, Guang; Shindell, Drew T.; Faluvegi, Greg

2016-01-01

The effect of future climate change on surface ozone over North America, Europe, and East Asia is evaluated using present-day (2000s) and future (2100s) hourly surface ozone simulated by four global models. Future climate follows RCP8.5, while methane and anthropogenic ozone precursors are fixed at year-2000 levels. Climate change shifts the seasonal surface ozone peak to earlier in the year and increases the amplitude of the annual cycle. Increases in mean summertime and high-percentile ozone are generally found in polluted environments, while decreases are found in clean environments. We propose climate change augments the efficiency of precursor emissions to generate surface ozone in polluted regions, thus reducing precursor export to neighboring downwind locations. Even with constant biogenic emissions, climate change causes the largest ozone increases at high percentiles. In most cases, air quality extreme episodes become larger and contain higher ozone levels relative to the rest of the distribution.

Surface Level Ozone and its Adverse Effects on Crops and Forests: A Need for an Interdisciplinary Understanding

Directory of Open Access Journals (Sweden)

Sagar V. Krupa

2001-01-01

Full Text Available Surface level ozone (O3 is clearly a global scale problem with regard to its adverse effects on crops, forests and native, terrestrial plant ecosystems. Photochemists and meteorologists are continuing to define the chemistry and physics of the prevalence of O3 at the ground level. Similarly, plant scientists in the U.S. and Europe have examined the effects of O3 on crops and tree seedlings or saplings through large-scale studies. Examples include the U.S. National Crop Loss Assessment Network (NCLAN, the U.S. EPA’s (Environmental Protection Agency’s San Bernardino National Forest Photochemical Oxidant Study, European Open-top Chambers Programme (EOTCP, and several ongoing EU (European Union projects. In addition, there have been studies on mature tree responses through field measurements and by simulation modeling.

Bay breeze climatology at two sites along the Chesapeake bay from 1986-2010: Implications for surface ozone.

Science.gov (United States)

Stauffer, Ryan M; Thompson, Anne M

Hourly surface meteorological measurements were coupled with surface ozone (O 3 ) mixing ratio measurements at Hampton, Virginia and Baltimore, Maryland, two sites along the Chesapeake Bay in the Mid-Atlantic United States, to examine the behavior of surface O 3 during bay breeze events and quantify the impact of the bay breeze on local O 3 pollution. Analyses were performed for the months of May through September for the years 1986 to 2010. The years were split into three groups to account for increasingly stringent environmental regulations that reduced regional emissions of nitrogen oxides (NO x ): 1986-1994, 1995-2002, and 2003-2010. Each day in the 25-year record was marked either as a bay breeze day, a non-bay breeze day, or a rainy/cloudy day based on the meteorological data. Mean eight hour (8-h) averaged surface O 3 values during bay breeze events were 3 to 5 parts per billion by volume (ppbv) higher at Hampton and Baltimore than on non-bay breeze days in all year periods. Anomalies from mean surface O 3 were highest in the afternoon at both sites during bay breeze days in the 2003-2010 study period. In conjunction with an overall lowering of baseline O 3 after the 1995-2002 period, the percentage of total exceedances of the Environmental Protection Agency (EPA) 75 ppbv 8-h O 3 standard that occurred on bay breeze days increased at Hampton for 2003-2010, while remaining steady at Baltimore. These results suggest that bay breeze circulations are becoming more important to causing exceedance events at particular sites in the region, and support the hypothesis of Martins et al. (2012) that highly localized meteorology increasingly drives air quality events at Hampton.

Hydrological controls on the tropospheric ozone greenhouse gas effect

Directory of Open Access Journals (Sweden)

Le Kuai

2017-03-01

Full Text Available The influence of the hydrological cycle in the greenhouse gas (GHG effect of tropospheric ozone (O3 is quantified in terms of the O3longwave radiative effect (LWRE, which is defined as the net reduction of top-of-atmosphere flux due to total tropospheric O3absorption. The O3LWRE derived from the infrared spectral measurements by Aura’s Tropospheric Emission Spectrometer (TES show that the spatiotemporal variation of LWRE is relevant to relative humidity, surface temperature, and tropospheric O3column. The zonally averaged subtropical LWRE is ~0.2 W m-2higher than the zonally averaged tropical LWRE, generally due to lower water vapor concentrations and less cloud coverage at the downward branch of the Hadley cell in the subtropics. The largest values of O3LWRE over the Middle East (>1 W/m2 are further due to large thermal contrasts and tropospheric ozone enhancements from atmospheric circulation and pollution. Conversely, the low O3LWRE over the Inter-Tropical Convergence Zone (on average 0.4 W m-2 is due to strong water vapor absorption and cloudiness, both of which reduce the tropospheric O3absorption in the longwave radiation. These results show that changes in the hydrological cycle due to climate change could affect the magnitude and distribution of ozone radiative forcing.

Atomic layer deposition and post-growth thermal annealing of ultrathin MoO3 layers on silicon substrates: Formation of surface nanostructures

Science.gov (United States)

Liu, Hongfei; Yang, Ren Bin; Yang, Weifeng; Jin, Yunjiang; Lee, Coryl J. J.

2018-05-01

Ultrathin MoO3 layers have been grown on Si substrates at 120 °C by atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo(CO)6] and ozone (O3) as the Mo- and O-source precursors, respectively. The ultrathin films were further annealed in air at Tann = 550-750 °C for 15 min. Scanning-electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy have been employed to evaluate the morphological and elemental properties as well as their evolutions upon annealing of the thin films. They revealed an interfacial SiOx layer in between the MoO3 layer and the Si substrate; this SiOx layer converted into SiO2 during the annealing; and the equivalent thickness of the MoO3 (SiO2) layer decreased (increased) with the increase in Tann. Particles with diameters smaller than 50 nm emerged at Tann = 550 °C and their sizes (density) were reduced (increased) by increasing Tann to 650 °C. A further increase of Tann to 750 °C resulted in telephone-cord-like MoO3 structures, initiated from isolated particles on the surface. These observations have been discussed and interpreted based on temperature-dependent atomic interdiffusions, surface evaporations, and/or melting of MoO3, which shed new light on ALD MoO3 towards its electronic applications.

Meteorologically-adjusted trend analysis of surface observed ozone at three monitoring sites in Delhi, India: 2007-2011

Science.gov (United States)

Biswas, J.; Farooqui, Z.; Guttikunda, S. K.

2012-12-01

It is well known that meteorological parameters have significant impact on surface ozone concentrations. Therefore it is important to remove the effects of meteorology on ozone concentrations to correctly estimate long-term trends in ozone levels due to the alterations in precursor emissions. This is important for the development of effectual control strategies. In this study surface observed ozone trends in New Delhi are analyzed using Komogorov-Zurbenko (KZ) filter, US EPA ozone adjustment due to weather approach and the classification and regression tree method. The statistical models are applied to the ozone data at three observational sites in New Delhi metropolitan areas, 1) Income Tax Office (ITO) 2) Sirifort and 3) Delhi College of Engineering (DCE). The ITO site is located adjacent to a traffic crossing, Sirifort is an urban site and the DCE site is located in a residential area. The ITO site is also influenced by local industrial emissions. DCE has higher ozone levels than the other two sites. It was found that ITO has lowest ozone concentrations amongst the three sites due to ozone titrating due to industrial and on-road mobile NOx emissions. The statistical methods employed can assess ozone trends at these sites with a high degree of confidence and the results can be used to gauge the effectiveness of control strategies on surface ozone levels in New Delhi.

Bromide Sources and Loads in Swiss Surface Waters and Their Relevance for Bromate Formation during Wastewater Ozonation.

Science.gov (United States)

Soltermann, Fabian; Abegglen, Christian; Götz, Christian; von Gunten, Urs

2016-09-20

Bromide measurements and mass balances in the catchments of major Swiss rivers revealed that chemical industry and municipal waste incinerators are the most important bromide sources and account for ∼50% and ∼20%, respectively, of the ∼2000 tons of bromide discharged in the Rhine river in 2014 in Switzerland. About 100 wastewater treatment plants (WWTPs) will upgrade their treatment for micropollutant abatement in the future to comply with Swiss regulations. An upgrade with ozonation may lead to unintended bromate formation in bromide-containing wastewaters. Measured bromide concentrations were industry). Wastewater ozonation formed little bromate at specific ozone doses of ≤0.4 mg O3/mg DOC, while the bromate yields were almost linearly correlated to the specific ozone dose for higher ozone doses. Molar bromate yields for typical specific ozone doses in wastewater treatment (0.4-0.6 mg O3/mg DOC) are ≤3%. In a modeled extreme scenario (in which all upgraded WWTPs release 10 μg L(-1) of bromate), bromate concentrations increased by major Swiss rivers and by several micrograms per liter in receiving water bodies with a high fraction of municipal wastewater.

Acute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II Diabetes

Science.gov (United States)

Abstract for Society of Toxicology, March 22-25, 2015, San Diego, CAAcute Ozone (O3) Exposure Accelerates Diet-Induced Pulmonary Injury and Metabolic Alterations in a Rat Model of Type II DiabetesS.J. Snow1,3, D. Miller2, V. Bass2, M. Schladweiler3, A. Ledbetter3, J. Richards3, C...

The impacts of surface ozone pollution on winter wheat productivity in China – An econometric approach

International Nuclear Information System (INIS)

Yi, Fujin; Jiang, Fei; Zhong, Funing; Zhou, Xun; Ding, Aijun

2016-01-01

The impact of surface ozone pollution on winter wheat yield is empirically estimated by considering socio-economic and weather determinants. This research is the first to use an economic framework to estimate the ozone impact, and a unique county-level panel is employed to examine the impact of the increasing surface ozone concentration on the productivity of winter wheat in China. In general, the increment of surface ozone concentration during the ozone-sensitive period of winter wheat is determined to be harmful to its yield, and a conservative reduction of ozone pollution could significantly increase China's wheat supply. - Highlights: • We examine the impacts of the surface ozone exposure on winter wheat yield in China. • An econometric method is used to measure the ozone impacts. • The results conclude that surface ozone is harmful to winter wheat yield in China. • We confirm that stress conditions such as drought and air particles can mitigate the adverse effect of ozone. - Surface ozone pollution is harmful to winter wheat yield in China by considering socio-economic determinants, weather, and other stress conditions like drought and air particles.

Influence of power supply on the generation of ozone and degradation of phenol in a surface discharge reactor

International Nuclear Information System (INIS)

Zhao, Yan; Shang, Kefeng; Duan, Lijuan; Li, Yue; An, Jiutao; Zhang, Chunyang; Lu, Na; Wu, Yan; Li, Jie

2013-01-01

A surface Dielectric Barrier Discharge (DBD) reactor was utilized to degrade phenol in water. Different power supplies applied to the DBD reactor affect the discharge modes, the formation of chemically active species and thus the removal efficiency of pollutants. It is thus important to select an optimized power supply for the DBD reactor. In this paper, the influence of the types of power supplies including alternate current (AC) and bipolar pulsed power supply on the ozone generation in a surface discharge reactor was measured. It was found that compared with bipolar pulsed power supply, higher energy efficiency of O 3 generation was obtained when DBD reactor was supplied with 50Hz AC power supply. The highest O 3 generation was approximate 4 mg kJ −1 ; moreover, COD removal efficiency of phenol wastewater reached 52.3% after 3 h treatment under an AC peak voltage of 2.6 kV.

Influence of power supply on the generation of ozone and degradation of phenol in a surface discharge reactor

Science.gov (United States)

Zhao, Yan; Shang, Kefeng; Duan, Lijuan; Li, Yue; An, Jiutao; Zhang, Chunyang; Lu, Na; Li, Jie; Wu, Yan

2013-03-01

A surface Dielectric Barrier Discharge (DBD) reactor was utilized to degrade phenol in water. Different power supplies applied to the DBD reactor affect the discharge modes, the formation of chemically active species and thus the removal efficiency of pollutants. It is thus important to select an optimized power supply for the DBD reactor. In this paper, the influence of the types of power supplies including alternate current (AC) and bipolar pulsed power supply on the ozone generation in a surface discharge reactor was measured. It was found that compared with bipolar pulsed power supply, higher energy efficiency of O3 generation was obtained when DBD reactor was supplied with 50Hz AC power supply. The highest O3 generation was approximate 4 mg kJ-1 moreover, COD removal efficiency of phenol wastewater reached 52.3% after 3 h treatment under an AC peak voltage of 2.6 kV.

California Baseline Ozone Transport Study (CABOTS): Ozonesonde Measurements

Science.gov (United States)

Eiserloh, A. J., Jr.; Chiao, S.; Spitze, J.; Cauley, S.; Clark, J.; Roberts, M.

2016-12-01

Because the EPA recently lowered the ambient air quality standard for the 8-hr average of ozone (O3) to70 ppbv, California must continue to achieve significant reductions in ozone precursor emissions and prepare for new State Implementation Plans (SIP) to demonstrate how ground-level ambient ozone will be reduced below the new health-based standard. Prior studies suggest that background levels of ozone traveling across the Pacific Ocean can significantly influence surface ozone throughout California, particularly during the spring. Evidence has been presented indicating that background levels of ozone continue to increase in the western United States over the recent few decades, implying more ozone exceedances in the future. To better understand the contributions of the external natural and anthropogenic pollution sources as well as atmospheric processes for surface ozone concentrations in California during the spring and summer months, the California Baseline Ozone Transport Study (CABOTS) has been established. One major goal of CABOTS is to implement near daily ozonesonde measurements along the California Coast to quantify background ozone aloft before entering the State during high ozone season. CABOTS has been ongoing from May through August of 2016 launching ozonesondes from Bodega Bay and Half Moon Bay, California. The temporal progression of ozonesonde measurements and subsequent analysis of the data will be discussed with a focus on the contribution of background ozone to surface ozone sites inland as well as likely origins of layers aloft. Comparisons of current ozonesondes versus prior ozonesonde studies of California will also be performed. A few selected cases of high ozone layers moving onshore from different sources will be discussed as well.

The dynamics of ozone generation and mode transition in air surface micro-discharge plasma at atmospheric pressure

International Nuclear Information System (INIS)

Shimizu, Tetsuji; Zimmermann, Julia L; Morfill, Gregor E; Sakiyama, Yukinori; Graves, David B

2012-01-01

We present the transient, dynamic behavior of ozone production in surface micro-discharge (SMD) plasma in ambient air. Ultraviolet absorption spectroscopy at 254 nm was used to measure the time development of ozone density in a confined volume. We observed that ozone density increases monotonically over 1000 ppm for at least a few minutes when the input power is lower than ∼0.1 W/cm 2 . Interestingly, when input power is higher than ∼0.1 W/cm 2 , ozone density starts to decrease in a few tens of seconds at a constant power density, showing a peak ozone density. A model calculation suggests that the ozone depletion at higher power density is caused by quenching reactions with nitrogen oxides that are in turn created by vibrationally excited nitrogen molecules reacting with O atoms. The observed mode transition is significantly different from classical ozone reactors in that the transition takes place over time at a constant power. In addition, we observed a positive correlation between time-averaged ozone density and the inactivation rate of Escherichia coli on adjacent agar plates, suggesting that ozone plays a key role in inactivating bacteria under the conditions considered here. (paper)

Impact of the 2008 Global Recession on Air Quality over the United States: Implications for Surface Ozone Levels from Changes in NOx Emissions

Science.gov (United States)

Tong, Daniel; Pan, Li; Chen, Weiwei; Lamsal, Lok; Lee, Pius; Tang, Youhua; Kim, Hyuncheol; Kondragunta, Shobha; Stajner, Ivanka

2016-01-01

Satellite and ground observations detected large variability in nitrogen oxides (NOx) during the 2008 economic recession, but the impact of the recession on air quality has not been quantified. This study combines observed NOx trends and a regional chemical transport model to quantify the impact of the recession on surface ozone (O3) levels over the continental United States. The impact is quantified by simulating O3 concentrations under two emission scenarios: business-as-usual (BAU) and recession. In the BAU case, the emission projection from the Cross-State Air Pollution Rule is used to estimate the would-be NOx emission level in 2011. In the recession case, the actual NO2 trends observed from Air Quality System ground monitors and the Ozone Monitoring Instrument on the Aura satellite are used to obtain realistic changes in NOx emissions. The model prediction with the recession effect agrees better with ground O3 observations over time and space than the prediction with the BAU emission. The results show that the recession caused a 12ppbv decrease in surface O3 concentration over the eastern United States, a slight increase (0.51ppbv) over the Rocky Mountain region, and mixed changes in the Pacific West. The gain in air quality benefits during the recession, however, could be quickly offset by the much slower emission reduction rate during the post-recession period.

Ozone-mist spray sterilization for pest control in agricultural management

Science.gov (United States)

Ebihara, Kenji; Mitsugi, Fumiaki; Ikegami, Tomoaki; Nakamura, Norihito; Hashimoto, Yukio; Yamashita, Yoshitaka; Baba, Seiji; Stryczewska, Henryka D.; Pawlat, Joanna; Teii, Shinriki; Sung, Ta-Lun

2013-02-01

We developed a portable ozone-mist sterilization system to exterminate pests (harmful insects) in agricultural field and greenhouse. The system is composed of an ozone generator, an ozone-mist spray and a small container of ozone gas. The ozone generator can supply highly concentrated ozone using the surface dielectric barrier discharge. Ozone-mist is produced using a developed nozzle system. We studied the effects of ozone-mist spray sterilization on insects and agricultural plants. The sterilization conditions are estimated by monitoring the behavior of aphids and observing the damage of the plants. It was shown that aphids were exterminated in 30 s without noticeable damages of the plant leaves. The reactive radicals with strong oxidation potential such as hydroxyl radical (*OH), hydroperoxide radical (*HO2), the superoxide ion radical (*O2‒) and ozonide radical ion (*O3‒) can increase the sterilization rate for aphids. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Ozone and ozone injury on plants in and around Beijing, China

International Nuclear Information System (INIS)

Wan, Wuxing; Manning, W.J.; Wang, Xiaoke; Zhang, Hongxing; Sun, Xu; Zhang, Qianqian

2014-01-01

Ozone (O 3 ) levels were assessed for the first time with passive samplers at 10 sites in and around Beijing in summer 2012. Average O 3 concentrations were higher at locations around Beijing than in the city center. Levels varied with site locations and ranged from 22.5 to 48.1 ppb and were highest at three locations. Hourly O 3 concentrations exceeded 40 ppb for 128 h and 80 ppb for 17 h from 2 to 9 in August at one site, where it had a real-time O 3 analyzer. Extensive foliar O 3 injury was found on 19 species of native and cultivated trees, shrubs, and herbs at 6 of the 10 study sites and the other 2 sites without passive sampler. This is the first report of O 3 foliar injury in and around Beijing. Our results warrant an extensive program of O 3 monitoring and foliar O 3 injury assessment in and around Beijing. - Highlights: • Plants have been threatened by high O 3 concentration in and around Beijing, China. • 19 plant species are reported as obvious ambient O 3 injury symptoms in Beijing. • The O 3 injury symptoms occur more often where ambient O 3 concentration is higher. • The results warrant more extensive and long-term study of ambient O 3 in China. - First report of ozone incidence and ozone injury on plants in and around Beijing, China

Ozone and nitrogen oxides in surface air in Russia: TROICA experiments.

Science.gov (United States)

Pankratova, N.; Elansky, N.; Belikov, I.; Shumskiy, R.

2009-04-01

The results of measurements of surface ozone and nitrogen oxides concentrations over the continental regions of Russia are discussed. The measurements were done during 10 TROICA experiments (Transcontinental Observations Into the Chemistry of the Atmosphere). The TROICA experiment started in 1995. By the present moment ten expeditions along the Trans-Siberian railroad from Moscow to Vladivostok (around 9300 km) are carried out. We separate data sets into unpolluted and polluted areas to study temporal and spatial features. Moreover we analyzed cities (more then 100 cities). About 50% of all data corresponds to unpolluted conditions. The data collected are used in an analysis of the physical and chemical processes occurring over continental Russia. In this work the estimations of seasonal and daily ozone and NOx distribution were made. The seasonal distribution of ozone for TROICA experiments concentration considerably differs from ozone distribution at Mace Head (Ireland) and Hohenpeissenberg (Germany) stations and well agrees with the ozone distribution at Zotino (Russia, East Siberia). The same concerns also a daily variability. The ozone concentration gradient is presented. Ozone concentration gradually increases in the eastward direction. Its result of the air transport from polluted regions of Europe and ozone depletions, oxidations of CH4 in Siberia, forest fires in Siberia and around Baikal Lake, regional transport of burning products from Northern China. Significant factor of ozone increasing is stratospheric-tropospheric exchange. It appears in TROICA-3 experiment. During several hours ozone concentration was more then 60 ppbv. The areas of photochemical ozone generation in polluted air are also detected. We estimate anthropogenic and natural factors, which are responsible for sharp ozone concentration increasing. Acknowledgments. The work was supported by International Science and Technology Center (ISTC) under contract No. 2770 and by Russian Basic

The Impact of Iodide-Mediated Ozone Deposition and Halogen Chemistry on Surface Ozone Concentrations Across the Continental United States

Science.gov (United States)

The air quality of many large coastal areas in the United States is affected by the confluence of polluted urban and relatively clean marine airmasses, each with distinct atmospheric chemistry. In this context, the role of iodide-mediated ozone (O3) deposition over seawater and m...

Residential indoor air quality guideline : ozone

International Nuclear Information System (INIS)

2010-01-01

Ozone (O 3 ) is a colourless gas that reacts rapidly on surfaces and with other constituents in the air. Sources of indoor O 3 include devices sold as home air cleaners, and some types of office equipment. Outdoor O 3 is also an important contributor to indoor levels of O 3 , depending on the air exchange rate with indoor environments. This residential indoor air quality guideline examined factors that affect the introduction, dispersion and removal of O 3 indoors. The health effects of prolonged exposure to O 3 were discussed, and studies conducted to evaluate the population health impacts of O 3 were reviewed. The studies demonstrated that there is a significant association between ambient O 3 and adverse health impacts. Exposure guidelines for residential indoor air quality were discussed. 14 refs.

The impacts of surface ozone pollution on winter wheat productivity in China--An econometric approach.

Science.gov (United States)

Yi, Fujin; Jiang, Fei; Zhong, Funing; Zhou, Xun; Ding, Aijun

2016-01-01

The impact of surface ozone pollution on winter wheat yield is empirically estimated by considering socio-economic and weather determinants. This research is the first to use an economic framework to estimate the ozone impact, and a unique county-level panel is employed to examine the impact of the increasing surface ozone concentration on the productivity of winter wheat in China. In general, the increment of surface ozone concentration during the ozone-sensitive period of winter wheat is determined to be harmful to its yield, and a conservative reduction of ozone pollution could significantly increase China's wheat supply. Copyright © 2015 Elsevier Ltd. All rights reserved.

Molecular storage of ozone in a clathrate hydrate: an attempt at preserving ozone at high concentrations.

Directory of Open Access Journals (Sweden)

Takahiro Nakajima

Full Text Available This paper reports an experimental study of the formation of a mixed O(3+ O(2+ CO(2 hydrate and its frozen storage under atmospheric pressure, which aimed to establish a hydrate-based technology for preserving ozone (O(3, a chemically unstable substance, for various industrial, medical and consumer uses. By improving the experimental technique that we recently devised for forming an O(3+ O(2+ CO(2 hydrate, we succeeded in significantly increasing the fraction of ozone contained in the hydrate. For a hydrate formed at a system pressure of 3.0 MPa, the mass fraction of ozone was initially about 0.9%; and even after a 20-day storage at -25°C and atmospheric pressure, it was still about 0.6%. These results support the prospect of establishing an economical, safe, and easy-to-handle ozone-preservation technology of practical use.

Evaluation of oxygenation time in SmBa2Cu3O7-δ superconductors ceramics in air and ozone atmospheres

International Nuclear Information System (INIS)

Viana, P.R.P; Cunha, A.G.

2010-01-01

High temperature superconductors (HTSC) represent a major milestone in science. During the preparation of superconductors, oxygenation plays a key role, because oxygenation determines the distribution of charge carriers in these plans through the superconducting Cu-O and hence superconductivity. This paper proposes the preparation of polycrystalline superconductors using the ceramic method, and the step of oxygenation made with ozone gas (O 3 ). Ozone exerts chemical pressure on the compound, which has oxygen vacancies in its structure after the step of synthesis. The work was performed by varying the time between oxygenation 20, 40, 80 and 160 hours, with samples going through a process of oxygenation at 350 deg C after the step of synthesis. This study evaluates the time effect as oxygen can improve the superconducting properties such as resistivity and magnetic susceptibility. (author)

DO3SE model applicability and O3 flux performance compared to AOT40 for an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma').

Science.gov (United States)

Assis, Pedro I L S; Alonso, Rocío; Meirelles, Sérgio T; Moraes, Regina M

2015-07-01

Phytotoxic ozone (O3) levels have been recorded in the Metropolitan Region of São Paulo (MRSP). Flux-based critical levels for O3 through stomata have been adopted for some northern hemisphere species, showing better accuracy than with accumulated ozone exposure above a threshold of 40 ppb (AOT40). In Brazil, critical levels for vegetation protection against O3 adverse effects do not exist. The study aimed to investigate the applicability of O3 deposition model (Deposition of Ozone for Stomatal Exchange (DO3SE)) to an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma') under the MRSP environmental conditions, which are very unstable, and to assess the performance of O3 flux and AOT40 in relation to O3-induced leaf injuries. Stomatal conductance (g s) parameterization for 'Paluma' was carried out and used to calculate different rate thresholds (from 0 to 5 nmol O3 m(-2) projected leaf area (PLA) s(-1)) for the phytotoxic ozone dose (POD). The model performance was assessed through the relationship between the measured and modeled g sto. Leaf injuries were analyzed and associated with POD and AOT40. The model performance was satisfactory and significant (R (2) = 0.56; P < 0.0001; root-mean-square error (RMSE) = 116). As already expected, high AOT40 values did not result in high POD values. Although high POD values do not always account for more injuries, POD0 showed better performance than did AOT40 and other different rate thresholds for POD. Further investigation is necessary to improve our model and also to check if there is a critical level of ozone in which leaf injuries arise. The conclusion is that the DO3SE model for 'Paluma' is applicable in the MRSP as well as in temperate regions and may contribute to future directives.

Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

Energy Technology Data Exchange (ETDEWEB)

Morrison, Glenn Charles [Univ. of California, Berkeley, CA (United States)

1999-12-01

In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10

Ozone biomonitoring in Pakistan using tobacco cultivar Bel-W3

International Nuclear Information System (INIS)

Kafiatullah, A.; Shamsi, S.R.A.

2012-01-01

The present study depicts a comparison of ozone (O/sub 3/) concentrations over a decade time (1993-94 to 2006) using plant biomonitoring and continuous ozone monitors techniques in Lahore city of Pakistan. The variations in O/sub 3/ levels were assessed at city centre, suburbs and semi-rural/rural locations in and around the city of Lahore by using American O/sub 3/-sensitive tobacco biomonitor plant ( Nicotiana tabaccum L. cv. Bel-W3) for the first time in Pakistan during 1993 and 1994 seasons through weekly assessment of visible damage to leaves. Results for both 1993 and 1994 seasons indicated significant differences between sites in the mean 6-h O/sub 3/ concentrations with a range of over 20 ppb and 15 ppb across the sites in 1993 and 1994, respectively. An inverse relationship between the levels of NO/sub 2/ and O/sub 3/ was found during investigation. The highest O/sub 3/ levels of 75-80 ppb were found at rural areas and the lowest at city centre sites. The extent of O/sub 3/ injury on the tobacco cv. Bel-W3 leaves reflected the trends seen in O/sub 3/ concentrations. The highest and lowest leaf injury indices of 18-27% and 5-7% occurred at the rural and city centre sites, respectively. Results for 2006 season indicated the highest seasonal mean O/sub 3/ concentration of 100 ppb in semi-rural areas compared with city centre sites (68 ppb). The highest 26% and 20% increase in O/sub 3/ levels was observed at rural/semi-rural and city centre sites, respectively when compared with 1993 O/sub 3/ survey. Application of O/sub 3/ biomonitoring technique proved very cost-effective and feasible for the estimation of atmospheric O/sub 3/ levels in South East Asian regions like Pakistan where shortage of electric supply, trained man power and poverty is already playing havoc. (author)

Caffeine degradation in water by gamma irradiation, ozonation and ozonation/gamma irradiation

Directory of Open Access Journals (Sweden)

Torun Murat

2014-03-01

Full Text Available Aqueous solutions of caffeine were treated with ozone and gamma irradiation. The amounts of remaining caffeine were determined after solid phase extraction as a function of absorbed dose and ozonation time. In addition to this, some important parameters such as inorganic ions, chemical oxygen demand (COD dissolved oxygen and total acidity changes were followed. Caffeine (50 ppm is found to be completely decomposed at 3.0 kGy and 1.2 kGy doses in the absence of H2O2 and in 1.20 mM H2O2 solutions, respectively. In the case of gamma irradiation after ozonation, 50 ppm caffeine was removed at 0.2 kGy when the solution was ozonized for 100 s at a rate of 10 g O3 h-1 in 400 mL 50 ppm paracetamol solution.

Artificial O3 formation during fireworks

Science.gov (United States)

Fiedrich, M.; Kurtenbach, R.; Wiesen, P.; Kleffmann, J.

2017-09-01

In several previous studies emission of ozone (O3) during fireworks has been reported, which was attributed to either photolysis of molecular oxygen (O2) or nitrogen dioxide (NO2) by short/near UV radiation emitted during the high-temperature combustion of fireworks. In contrast, in the present study no O3 formation was observed using a selective O3-LOPAP instrument during the combustion of pyrotechnical material in the laboratory, while a standard O3 monitor using UV absorption showed extremely high O3 signals. The artificial O3 response of the standard O3 monitor was caused by known interferences associated with high levels of co-emitted VOCs and could also be confirmed in field measurements during New Year's Eve in the city of Wuppertal, Germany. The present results help to explain unreasonably high ozone levels documented during ambient fireworks, which are in contradiction to the fast titration of O3 by nitrogen monoxide (NO) in the night-time atmosphere.

Inhaled ozone (O3)-induces changes in serum metabolomic and liver transcriptomic profiles in rats☆

Science.gov (United States)

Miller, Desinia B.; Karoly, Edward D.; Jones, Jan C.; Ward, William O.; Vallanat, Beena D.; Andrews, Debora L.; Schladweiler, Mette C.; Snow, Samantha J.; Bass, Virginia L.; Richards, Judy E.; Ghio, Andrew J.; Cascio, Wayne E.; Ledbetter, Allen D.; Kodavanti, Urmila P.

2016-01-01

Air pollution has been linked to increased incidence of diabetes. Recently, we showed that ozone (O3) induces glucose intolerance, and increases serum leptin and epinephrine in Brown Norway rats. In this study, we hypothesized that O3 exposure will cause systemic changes in metabolic homeostasis and that serum metabolomic and liver transcriptomic profiling will provide mechanistic insights. In the first experiment, male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or O3 at 0.25, 0.50, or 1.0 ppm, 6 h/day for two days to establish concentration-related effects on glucose tolerance and lung injury. In a second experiment, rats were exposed to FA or 1.0 ppm O3, 6 h/day for either one or two consecutive days, and systemic metabolic responses were determined immediately after or 18 h post-exposure. O3 increased serum glucose and leptin on day 1. Glucose intolerance persisted through two days of exposure but reversed 18 h-post second exposure. O3 increased circulating metabolites of glycolysis, long-chain free fatty acids, branched-chain amino acids and cholesterol, while 1,5-anhydroglucitol, bile acids and metabolites of TCA cycle were decreased, indicating impaired glycemic control, proteolysis and lipolysis. Liver gene expression increased for markers of glycolysis, TCA cycle and gluconeogenesis, and decreased for markers of steroid and fat biosynthesis. Genes involved in apoptosis and mitochondrial function were also impacted by O3. In conclusion, short-term O3 exposure induces global metabolic derangement involving glucose, lipid, and amino acid metabolism, typical of a stress–response. It remains to be examined if these alterations contribute to insulin resistance upon chronic exposure. PMID:25838073

Characteristics of UV-MicroO3 Reactor and Its Application to Microcystins Degradation during Surface Water Treatment

Directory of Open Access Journals (Sweden)

Guangcan Zhu

2015-01-01

Full Text Available The UV-ozone (UV-O3 process is not widely applied in wastewater and potable water treatment partly for the relatively high cost since complicated UV radiation and ozone generating systems are utilized. The UV-microozone (UV-microO3, a new advanced process that can solve the abovementioned problems, was introduced in this study. The effects of air flux, air pressure, and air humidity on generation and concentration of O3 in UV-microO3 reactor were investigated. The utilization of this UV-microO3 reactor in microcystins (MCs degradation was also carried out. Experimental results indicated that the optimum air flux in the reactor equipped with 37 mm diameter quartz tube was determined to be 18∼25 L/h for efficient O3 generation. The air pressure and humidity in UV-microO3 reactor should be low enough in order to get optimum O3 output. Moreover, microcystin-RR, YR, and LR (MC-RR, MC-YR, and MC-LR could be degraded effectively by UV-microO3 process. The degradation of different MCs was characterized by first-order reaction kinetics. The pseudofirst-order kinetic constants for MC-RR, MC-YR, and MC-LR degradation were 0.0093, 0.0215, and 0.0286 min−1, respectively. Glucose had no influence on MC degradation through UV-microO3. The UV-microO3 process is hence recommended as a suitable advanced treatment method for dissolved MCs degradation.

Damages of surface ozone: evidence from agricultural sector in China

Science.gov (United States)

Yi, Fujin; McCarl, Bruce A.; Zhou, Xun; Jiang, Fei

2018-03-01

This study measures the damages that surface ozone pollution causes within the Chinese agricultural sector under 2014 conditions. It also analyzes the agricultural benefits of ozone reductions. The analysis is done using a partial equilibrium model of China’s agricultural sector. Results indicate that there are substantial, spatially differentiated damages that are greatest in ozone-sensitive crop growing areas with higher ozone concentrations. The estimated damage to China’s agricultural sector range is between CNY 1.6 trillion and 2.2 trillion, which for comparison is about one fifth of 2014 agricultural revenue. When considering concentration reduction we find a 30% ozone reduction yields CNY 678 billion in sectoral benefits. These benefits largely fall to consumers with producers losing as the production gains lead to lower prices.

Investigating the influence of long-range transport on surface O{sub 3} in Nevada, USA, using observations from multiple measurement platforms

Energy Technology Data Exchange (ETDEWEB)

Fine, Rebekka, E-mail: rebekkafine@gmail.com [Department of Natural Resources and Environmental Science, University of Nevada-Reno, Reno, NV (United States); Miller, Matthieu B. [Department of Natural Resources and Environmental Science, University of Nevada-Reno, Reno, NV (United States); Yates, Emma L.; Iraci, Laura T. [Atmospheric Science Branch, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Gustin, Mae Sexauer, E-mail: mgustin@cabnr.unr.edu [Department of Natural Resources and Environmental Science, University of Nevada-Reno, Reno, NV (United States)

2015-10-15

The current United States (US) National Ambient Air Quality Standard (NAAQS) for O{sub 3} (75 ppb) is expected to be revised to between 60 and 70 ppb. As the NAAQS becomes more stringent, characterizing the extent of O{sub 3} and precursors transported into the US is increasingly important. Given the high elevation, complex terrain, and location in the Intermountain West, the State of Nevada is ideally situated to intercept air transported into the US. Until recently, measurements of O{sub 3} and associated pollutants were limited to areas in and around the cities of Las Vegas and Reno. In 2011, the Nevada Rural Ozone Initiative began and through this project 13 surface monitoring sites were established. Also in 2011, the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) began making routine aircraft measurements of O{sub 3} and other greenhouse gases in Nevada. The availability of aircraft and surface measurements in a relatively rural, remote setting in the Intermountain West presented a unique opportunity to investigate sources contributing to the O{sub 3} observed in Nevada. Our analyses indicate that stratosphere to troposphere transport, long-range transport of Asian pollution, and regional emissions from urban areas and wildfires influence surface observations. The complexity of sources identified here along with the fact that O{sub 3} frequently approaches the threshold being considered for a revised NAAQS indicate that interstate and international cooperation will be necessary to achieve compliance with a more stringent regulatory standard. Further, on a seasonal basis we found no significant difference between daily 1-h maximum O{sub 3} at surface sites, which ranged in elevation from 888 to 2307 m, and aircraft measurements of O{sub 3} < 2500 m which suggests that similar processes influence daytime O{sub 3} across rural Nevada and indicates that column measurements from Railroad Valley, NV are useful in understanding these processes. - Highlights: �

How to most effectively expand the global surface ozone observing network

Directory of Open Access Journals (Sweden)

E. D. Sofen

2016-02-01

Full Text Available Surface ozone observations with modern instrumentation have been made around the world for more than 40 years. Some of these observations have been made as one-off activities with short-term, specific science objectives and some have been made as part of wider networks which have provided a foundational infrastructure of data collection, calibration, quality control, and dissemination. These observations provide a fundamental underpinning to our understanding of tropospheric chemistry, air quality policy, atmosphere–biosphere interactions, etc. brought together eight of these networks to provide a single data set of surface ozone observations. We investigate how representative this combined data set is of global surface ozone using the output from a global atmospheric chemistry model. We estimate that on an area basis, 25 % of the globe is observed (34 % land, 21 % ocean. Whereas Europe and North America have almost complete coverage, other continents, Africa, South America, Australia, and Asia (12–17 % show significant gaps. Antarctica is surprisingly well observed (78 %. Little monitoring occurs over the oceans, with the tropical and southern oceans particularly poorly represented. The surface ozone over key biomes such as tropical forests and savanna is almost completely unmonitored. A chemical cluster analysis suggests that a significant number of observations are made of polluted air masses, but cleaner air masses whether over the land or ocean (especially again in the tropics are significantly under-observed. The current network is unlikely to see the impact of the El Niño–Southern Oscillation (ENSO but may be capable of detecting other planetary-scale signals. Model assessment and validation activities are hampered by a lack of observations in regions where the models differ substantially, as is the ability to monitor likely changes in surface ozone over the next century. Using our methodology we are able to suggest new

Effect of UV/ozone treatment on the nanoscale surface properties of gold implanted polyethylene

Energy Technology Data Exchange (ETDEWEB)

Kisić, Danilo; Nenadović, Miloš [INS Vinca, Laboratory of Atomic Physics, University of Belgrade, Mike Alasa 12-14, 11001 Belgrade (Serbia); Štrbac, Svetlana [ICTM Institute of Electrochemistry, University of Belgrade, Njegoseva 12, 11001 Belgrade (Serbia); Adnadjević, Borivoj [Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade (Serbia); Rakočević, Zlatko, E-mail: zlatkora@vinca.rs [INS Vinca, Laboratory of Atomic Physics, University of Belgrade, Mike Alasa 12-14, 11001 Belgrade (Serbia)

2014-07-01

The effect of ultraviolet (UV) ozone treatment on the surface properties of gold implanted high density polyethylene (HDPE) was investigated at a nanoscale using Atomic Force Microscopy (AFM). HDPE samples were modified by the implantation of gold ions at a dose of 5 × 10{sup 15} ions/cm{sup 2}, using energies of 50, 100, 150, and 200 keV, and subsequently treated with UV/ozone. AFM surface topography images revealed that after UV/ozone treatment, the surface roughness of all Au/HDPE samples increased, while Power Spectral Density function increased only for samples implanted using higher energies, with a maximum for 150 keV. The chemical surface composition was homogenous in all cases, which was evidenced by the appearance of single peaks in the histograms obtained from the phase AFM images. For UV/ozone treated samples, the shift of the peaks positions in the histograms to the higher values of the phase lag with respect to untreated ones indicated the decrease of surface hardness. Besides, a significant change of fractal dimension of surface grains is observed after UV/ozone treatment.

Removal of diethyl phthalate from water solution by adsorption, photo-oxidation, ozonation and advanced oxidation process (UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2} and O{sub 3}/activated carbon)

Energy Technology Data Exchange (ETDEWEB)

Medellin-Castillo, Nahum A. [Centro de Investigacion y Estudios de Posgrado, Facultad de Ingenieria, Universidad Autonoma de San Luis Potosi, Av. Dr. M. Nava No.6, San Luis de Potosi, 78290 (Mexico); Ocampo-Perez, Raul [Centro de Investigacion y Estudios de Posgrado, Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi, 78290 (Mexico); Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Leyva-Ramos, Roberto [Centro de Investigacion y Estudios de Posgrado, Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi, 78290 (Mexico); Sanchez-Polo, Manuel [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Rivera-Utrilla, Jose, E-mail: jrivera@ugr.es [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Mendez-Diaz, Jose D. [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain)

2013-01-01

The objective of this work was to compare the effectiveness of conventional technologies (adsorption on activated carbon, AC, and ozonation) and technologies based on advanced oxidation processes, AOPs, (UV/H{sub 2}O{sub 2}, O{sub 3}/AC, O{sub 3}/H{sub 2}O{sub 2}) to remove phthalates from aqueous solution (ultrapure water, surface water and wastewater). Diethyl phthalate (DEP) was chosen as a model pollutant because of its high water solubility (1080 mg/L at 293 K) and toxicity. The activated carbons showed a high adsorption capacity to adsorb DEP in aqueous solution (up to 858 mg/g), besides the adsorption mechanism of DEP on activated carbon is governed by dispersive interactions between {pi} electrons of its aromatic ring with {pi} electrons of the carbon graphene planes. The photodegration process showed that the pH solution does not significantly affect the degradation kinetics of DEP and the first-order kinetic model satisfactorily fitted the experimental data. It was observed that the rate of decomposition of DEP with the O{sub 3}/H{sub 2}O{sub 2} and O{sub 3}/AC systems is faster than that with only O{sub 3}. The technologies based on AOPs (UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2}, O{sub 3}/AC) significantly improve the degradation of DEP compared to conventional technologies (O{sub 3}, UV). AC adsorption, UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2}, and O{sub 3}/AC showed a high yield to remove DEP; however, the disadvantage of AC adsorption is its much longer time to reach maximum removal. The best system to treat water (ultrapure and natural) polluted with DEP is the O{sub 3}/AC one since it achieved the highest DEP degradation and TOC removal, as well as the lower water toxicity. -- Highlights: Black-Right-Pointing-Pointer Activated carbons showed a high adsorption capacity (up to 858 mg/g) to remove DEP. Black-Right-Pointing-Pointer The pH solution did not significantly affect the photodegradation kinetics of DEP. Black

Investigation of In-Package Ozonation: The Effectiveness of Ozone to Inactive Salmonella enteritidis on Raw, Shell Eggs

Directory of Open Access Journals (Sweden)

Austin Donner

2011-01-01

Full Text Available Food production, handling, and distribution practices pose a constant threat to the quality and safety of food products. The objective of this research is to evaluate an innovative in-package ozonation process to reduce Salmonella enteritidis on raw, shell eggs. Previous research has shown that in-package ozonation eliminates contaminants from outside sources, reduces pathogens, and extends shelf life. In this study, raw, shell eggs were inoculated with Salmonella enteritidis and exposed to ozonation treatment. Microbial recoveries were then tested to determine bacterial reductions. Measurements included: relative humidity (34 percent at 5oC, surface temperatures (oC, ozone concentrations, bacterial reductions of Salmonella enteritidis, and quality assessment of eggs (Haugh Unit [HU], color, pH, and weight. After a 24-hour storage period, all treated samples indicated 3 log10 reductions on average (previous research has achieved up to 6log10. These results show effective in-package ozonation treatment reducing Salmonella enteritidis on raw, shell eggs without significant effect on measured egg quality over time. Benefits of in-package ozonation include no heating, low power requirements (less or equal to 50 Watts, short treatment time (seconds to minutes, and adaptability into existing processes. Given its ability to ensure the safety and longevity of food products, this technology has great potential for utilization in the food processing industry.

Hybrid HF-DFT comparative study of SrZrO{sub 3} and SrTiO{sub 3}(001) surface properties

Energy Technology Data Exchange (ETDEWEB)

Evarestov, R.A.; Bandura, A.V.; Alexandrov, V.E. [Department of Quantum Chemistry, St. Petersburg State University, 26 Universitetskii Prospekt, Stary Petergof, 198504 St. Petersburg (Russian Federation)

2006-10-15

Hybrid HF-DFT LCAO simulations of SrZrO{sub 3} and SrTiO{sub 3}(001) surface properties are performed in a single-slab model framework. The SrZrO{sub 3}(001) surface was studied by an ab initio method for the first time. Three slab models with different surface terminations including up to 8 atomic planes were used for calculation of the various surface characteristics (surface energies, atomic charges, density of electronic states). The dependence of the results on the chosen model and on the kind of d-element is analyzed. The dissimilarity in the surface oxygen atom contributions to the total density of states of two crystals is attributed to the more ionic nature of Zr-O bonds compared to Ti-O bonds. It is found that in the case of SrZrO{sub 3} the electronic density is biased towards the SrO-terminated surface and this surface should be more basic in nature than the SrO surface of SrTiO{sub 3} crystal. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Enhanced ozone production in a pulsed dielectric barrier discharge plasma jet with addition of argon to a He-O2 flow gas

Science.gov (United States)

Sands, Brian; Ganguly, Biswa; Scofield, James

2013-09-01

Ozone production in a plasma jet DBD driven with a 20-ns risetime unipolar pulsed voltage can be significantly enhanced using helium as the primary flow gas with an O2 coflow. The overvolted discharge can be sustained with up to a 5% O2 coflow at pulse repetition frequency at 13 kV applied voltage. Ozone production scales with the pulse repetition frequency up to a ``turnover frequency'' that depends on the O2 concentration, total gas flow rate, and applied voltage. For example, peak ozone densities >1016 cm-3 were measured with 3% O2 admixture and discharge current and 777 nm O(5 P) emission, but decreased ozone production and is followed by a transition to a filamentary discharge mode. The addition of argon at concentrations >=5% reduces the channel conductivity and shifts the turnover frequency to higher frequencies. This results in increased ozone production for a given applied voltage and gas flow rate. Time-resolved Ar(1s5) and He(23S1) metastable densities were acquired along with discharge current and ozone density measurements to gain insight into the mechanisms of optimum ozone production.

Surface and catalytic properties of MoO3/Al2O3 system doped with Co3O4

International Nuclear Information System (INIS)

Zahran, A.A.; Shaheen, W.M.; El-Shobaky, G.A.

2005-01-01

Thermal solid-solid interactions in cobalt treated MoO 3 /Al 2 O 3 system were investigated using X-ray powder diffraction. The solids were prepared by wet impregnation method using Al(OH) 3 , ammonium molybdate and cobalt nitrate solutions, drying at 100 deg. C then calcination at 300, 500, 750 and 1000 deg. C. The amount of MoO 3 , was fixed at 16.67 mol% and those of cobalt oxide were varied between 2.04 and 14.29 mol% Co 3 O 4 . Surface and catalytic properties of various solid samples precalcined at 300 and 500 deg. C were studied using nitrogen adsorption at -196 deg. C, conversion of isopropanol at 200-500 deg. C and decomposition of H 2 O 2 at 30-50 deg. C. The results obtained revealed that pure mixed solids precalcined at 300 deg. C consisted of AlOOH and MoO 3 phases. Cobalt oxide-doped samples calcined at the same temperature consisted also of AlOOH, MoO 3 and CoMoO 4 compounds. The rise in calcination temperature to 500 deg. C resulted in complete conversion of AlOOH into very poorly crystalline γ-Al 2 O 3 . The further increase in precalcination temperature to 750 deg. C led to the formation of Al 2 (MoO 4 ) 3 , κ-Al 2 O 3 besides CoMoO 4 and un-reacted portion of Co 3 O 4 in the samples rich in cobalt oxide. Pure MoO 3 /Al 2 O 3 preheated at 1000 deg. C composed of MoO 3 -αAl 2 O 3 solid solution (acquired grey colour). The doped samples consisted of the same solid solution together with CoMoO 4 and CoAl 2 O 4 compounds. The increase in calcination temperature of pure and variously doped solids from 300 to 500 deg. C increased their specific surface areas and total pore volume which suffered a drastic decrease upon heating at 750 deg. C. Doping the investigated system with small amounts of cobalt oxide (2.04 and 4 mol%) followed by heating at 300 and 500 deg. C increased its catalytic activity in H 2 O 2 decomposition. This increase, measured at 300 deg. C, attained 25.4- and 12.9-fold for the solids precalcined at 300 and 500 deg. C, respectively

Semiconductor Sensors Application for Definition of Factor of Ozone Heterogeneous Destruction on Teflon Surface

Directory of Open Access Journals (Sweden)

Nataliya V. Finogenova

2003-12-01

Full Text Available In our paper we present the results of our research, which was carried out by means of semiconductor sensor techniques (SCS, which allowed evaluating heterogeneous death-rate of ozone (γ Teflon surface. When ozone concentration is near to Ambient Air Standard value, γ is assessed to be equal to 6,57*10-7. High technique response provide possibility to determine ozone contents in the air media and the percentage of ozone, decomposed on the communication surfaces and on the surfaces of installation in the low concentration range (1–100 ppb.

Landfill leachate treatment with ozone and ozone/hydrogen peroxide systems

International Nuclear Information System (INIS)

Tizaoui, Chedly; Bouselmi, Latifa; Mansouri, Loubna; Ghrabi, Ahmed

2007-01-01

In the search for an efficient and economical method to treat a leachate generated from a controlled municipal solid waste landfill site (Jebel Chakir) in the region of greater Tunis in Tunisia, ozone alone and ozone combined with hydrogen peroxide were studied. The leachate was characterised by high COD, low biodegradability and intense dark colour. A purpose-built reactor, to avoid foaming, was used for the study. It was found that ozone efficacy was almost doubled when combined with hydrogen peroxide at 2 g/L but higher H 2 O 2 concentrations gave lower performances. Enhancement in the leachate biodegradability from about 0.1 to about 0.7 was achieved by the O 3 /H 2 O 2 system. Insignificant changes in pH that may due to buffering effect of bicarbonate was found. A small decrease in sulphate concentrations were also observed. In contrast, chloride concentration declined at the beginning of the experiment then increased to reach its initial value. Estimates of the operating costs were made for comparison purposes and it was found that the O 3 /H 2 O 2 system at 2 g/L H 2 O 2 gave the lowest cost of about 3.1 TND (∼2.3 USD)/kg COD removed

Enhanced photocatalytic ozonation of organics by g-C{sub 3}N{sub 4} under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Liao, Gaozu, E-mail: liaogaozu@m.scnu.edu.cn; Zhu, Dongyun; Li, Laisheng, E-mail: llsh@scnu.edu.cn; Lan, Bingyan

2014-09-15

Highlights: • g-C{sub 3}N{sub 4} is employed as active catalyst in the photocatalytic ozonation system. • The more negative conduction band of g-C{sub 3}N{sub 4} benefits the transfer of electrons. • The synergistic effect between photocatalysis and ozonation is promoted by g-C{sub 3}N{sub 4}. • Enhanced degradation of oxalic acid and biphenol A is achieved via g-C{sub 3}N{sub 4}/Vis/O{sub 3}. - Abstract: Graphitic carbon nitride (g-C{sub 3}N{sub 4}) was employed as the active photocatalyst in the photocatalytic ozonation coupling system in the present study. g-C{sub 3}N{sub 4} was prepared by directly heating thiourea in air at 550 °C. XRD, FT-IR, UV–vis was used to characterize the structure and optical property. Oxalic acid and bisphenol A were selected as model substances for photocatalytic ozonation reactions to evaluate the catalytic ability of g-C{sub 3}N{sub 4} (g-C{sub 3}N{sub 4}/Vis/O{sub 3}). The results showed that the degradation ratio of oxalic acid with g-C{sub 3}N{sub 4}/Vis/O{sub 3} was 65.2% higher than the sum of ratio when it was individually decomposed by g-C{sub 3}N{sub 4}/Vis and O{sub 3}. The TOC removal of biphenol A with g-C{sub 3}N{sub 4}/Vis/O{sub 3} was 2.17 times as great as the sum of the ratio when using g-C{sub 3}N{sub 4}/Vis and O{sub 3}. This improvement was attributed to the enhanced synergistic effect between photocatalysis and ozonation by g-C{sub 3}N{sub 4}. Under visible light irradiation, the photo-generated electrons produced on g-C{sub 3}N{sub 4} facilitated the electrons transfer owing to the more negative conduction band potential (−1.3 V versus NHE). It meant that the photo-generated electrons could be trapped by ozone and reaction with it more easily. Subsequently, the yield of hydroxyl radicals was improved so as to enhance the organics degradation efficiency. This work indicated that metal-free g-C{sub 3}N{sub 4} could be an excellent catalyst for mineralization of organic compounds in waste control.

The zonal structure of tropical O3 and CO as observed by the Tropospheric Emission Spectrometer in November 2004 – Part 2: Impact of surface emissions on O3 and its precursors

Directory of Open Access Journals (Sweden)

G. Osterman

2009-06-01

Full Text Available The impact of surface emissions on the zonal structure of tropical tropospheric ozone and carbon monoxide is investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions.Vertical ozone profiles from the Tropospheric Emission Spectrometer (TES and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ network show elevated concentrations of ozone over Indonesia and Australia (60–70 ppb in the lower troposphere against the backdrop of the well-known zonal "wave-one" pattern with ozone concentrations of (70–80 ppb centered over the Atlantic . Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT CO profiles (Jones et al., 2009. These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30–40% over Indonesia. The response of the free tropospheric chemical state to the changes in these emissions is investigated for ozone, CO, NOx, and PAN. Model simulations indicate that ozone over Indonesian/Australian is sensitive to regional changes in surface emissions of NOx but relatively insensitive to lightning NOx. Over sub-equatorial Africa and South America, free tropospheric NOx was reduced in response to increased surface emissions potentially muting ozone production.

Optimization of artificial neural network models through genetic algorithms for surface ozone concentration forecasting.

Science.gov (United States)

Pires, J C M; Gonçalves, B; Azevedo, F G; Carneiro, A P; Rego, N; Assembleia, A J B; Lima, J F B; Silva, P A; Alves, C; Martins, F G

2012-09-01

This study proposes three methodologies to define artificial neural network models through genetic algorithms (GAs) to predict the next-day hourly average surface ozone (O(3)) concentrations. GAs were applied to define the activation function in hidden layer and the number of hidden neurons. Two of the methodologies define threshold models, which assume that the behaviour of the dependent variable (O(3) concentrations) changes when it enters in a different regime (two and four regimes were considered in this study). The change from one regime to another depends on a specific value (threshold value) of an explanatory variable (threshold variable), which is also defined by GAs. The predictor variables were the hourly average concentrations of carbon monoxide (CO), nitrogen oxide, nitrogen dioxide (NO(2)), and O(3) (recorded in the previous day at an urban site with traffic influence) and also meteorological data (hourly averages of temperature, solar radiation, relative humidity and wind speed). The study was performed for the period from May to August 2004. Several models were achieved and only the best model of each methodology was analysed. In threshold models, the variables selected by GAs to define the O(3) regimes were temperature, CO and NO(2) concentrations, due to their importance in O(3) chemistry in an urban atmosphere. In the prediction of O(3) concentrations, the threshold model that considers two regimes was the one that fitted the data most efficiently.

Slow electrons kill the ozone

International Nuclear Information System (INIS)

Maerk, T.

2001-01-01

A new method and apparatus (Trochoidal electron monochromator) to study the interactions of electrons with atoms, molecules and clusters was developed. Two applications are briefly reported: a) the ozone destruction in the atmosphere is caused by different reasons, a new mechanism is proposed, that slow thermal electrons are self added to the ozone molecule (O 3 ) with a high frequency, then O 3 is destroyed ( O 3 + e - → O - + O 2 ); b) another application is the study of the binding energy of the football molecule C60. (nevyjel)

Reclaimed water quality during simulated ozone-managed aquifer recharge hybrid

KAUST Repository

Yoon, Min

2014-06-17

A synergistic hybrid of two treatment processes, managed aquifer recharge (MAR) combined with ozonation, was proposed for wastewater reclamation and water reuse applications. Batch reactor and soil-column experiments were performed to evaluate reclaimed water quality using various chemical and bacterial analyses. The ozone process was optimized at low ozone dose (0.5 mg O3/mg DOC) based on the control of N-nitrosodimethylamine (<5 ng L-1) and bromate (<10 μg L-1), and applied prior to (i.e., O3-MAR) and after MAR (i.e., MAR-O3). This work demonstrates that effluent organic matter (EfOM) and trace organic contaminants (TOrCs) are effectively removed during the hybrid process of MAR combined ozonation, compared to MAR only. Based on fluorescence excitation-emission matrices analyses, both MAR and ozonation reduce soluble microbial (protein-like) products while only ozonation contributes in reducing humic and fulvic substances. Even at low ozone dose of 0.5 mg O3/mg DOC, the O3-MAR hybrid significantly reduced UV absorbance by ≥2 m-1, BDOC by ≥64 %, and total (Σ) TOrC concentrations by ≥70 % in the effluent water quality. However, no significant improvement (<10 %) in the removal of Σ16 TOrC concentrations was observed for the increased ozone dose at 1.0 mg O3/mg DOC during MAR combined ozonation processes. Overall, O3-MAR was effective by 10-30 % in treating effluent water than MAR based on DOC, UV254 nm EfOM, TOrC and bacterial analyses. In addition, MAR-O3 was better than O3-MAR for the reduction of fluorescence (close MQ), TOrCs (≥74 %) and total bacteria cell concentrations (>3 log reduction). Therefore, implementing MAR prior to ozonation appears to remove the bio-amenable compounds that react rapidly with ozone, thereby reducing oxidant demand and treatment efficiency. © 2014 Springer-Verlag Berlin Heidelberg.

Ketoprofen removal by O3 and O3/UV processes: Kinetics, transformation products and ecotoxicity

International Nuclear Information System (INIS)

Illés, Erzsébet; Szabó, Emese; Takács, Erzsébet; Wojnárovits, László; Dombi, András; Gajda-Schrantz, Krisztina

2014-01-01

Ozonation (O 3 ) and its combination with ultraviolet radiation (O 3 /UV) were used to decompose ketoprofen (KET). Depending on the initial KET concentration, fourteen to fifty time's faster KET degradation was achieved using combined O 3 /UV method compared to simple ozonation. Using both methods, formation of four major aromatic transformation products were observed: 3-(1-hydroxyethyl)benzophenone, 3-(1-hydroperoxyethyl) benzophenone, 1-(3-benzoylphenyl) ethanone and 3-ethylbenzophenone. In the combined treatment the degradation was mainly due to the direct effect of UV light, however, towards the end of the treatment, O 3 highly contributed to the mineralization of small carboxylic acids. High (∼ 90%) mineralization degree was achieved using the O 3 /UV method. Toxicity tests performed using representatives of three trophic levels of the aquatic ecosystems (producers, consumers and decomposers) Pseudokirchneriella subcapitata green algae, Daphnia magna zooplanktons and Vibrio fischeri bacteria showed that under the used experimental conditions the transformation products have significantly higher toxicity towards all the test organisms, than KET itself. The bacteria and the zooplanktons showed higher tolerance to the formed products than algae. The measured toxicity correlates well with the concentration of the aromatic transformation products, therefore longer treatments than needed for complete degradation of KET are strongly suggested, in order to avoid possible impact of aromatic transformation products on the aquatic ecosystem. - Highlights: • Ketoprofen degradation is significantly faster using O 3 /UV compared to ozonation. • The presence of O 3 enhances the overall mineralization. • Formation of four major aromatic by-products was observed. • The main step in the decomposition is the decarboxylation. • Degradation products have higher toxicity than ketoprofen itself

Mechanism insight of pollutant degradation and bromate inhibition by Fe-Cu-MCM-41 catalyzed ozonation.

Science.gov (United States)

Chen, Weirui; Li, Xukai; Tang, Yiming; Zhou, Jialu; Wu, Dan; Wu, Yin; Li, Laisheng

2018-03-15

A flexible catalyst, Fe-Cu-MCM-41, was employed to enhance diclofenac (DCF) mineralization and inhibit bromate formation in catalytic ozonation process. Greater TOC removal was achieved in Fe-Cu-MCM-41/O 3 process (78%) than those in Fe-MCM-41/O 3 (65%), Cu-MCM-41/O 3 (73%) and sole ozonation (42%). But it was interesting that both Cu-MCM-41/O 3 and Fe-MCM-41/O 3 achieved 93% bromate inhibition efficiency, only 71% inhibition efficiency was observed in Fe-Cu-MCM-41/O 3 . Influence of pH, TBA/NaHSO 3 and detection of by-products were conducted to explore the mechanism. By Pyridine adsorption-IR and XPS, a relationship was found among activity of catalysts, Lewis acid sites and electron transfer effect between Fe (II/III) and Cu (I/II). Fe-Cu-MCM-41 promoted ozone decomposition to generate OH, which accounted for enhanced DCF mineralization. The consumption of aqueous O 3 also suppressed the oxidative of Br - and HBrO/Br - . More HBrO/BrO - accumulated in catalytic ozonation process and less bromate generated. Bromate formation in Fe-Cu-MCM-41/O 3 process was sensitive with pH value, the acidic condition was not favor for bromate formation. Both DCF mineralization and bromate inhibition were influenced by surface reaction. Moreover, Fe-Cu-MCM-41 showed excellent catalytic performance in suppressing the accumulation of carboxylic acid, especially for oxalic acid. Nearly no oxalic acid was detected during Fe-Cu-MCM-41/O 3 process. Copyright © 2017 Elsevier B.V. All rights reserved.

The historic surface ozone record, 1896-1975, and its relation to modern measurements

Science.gov (United States)

Galbally, I. E.; Tarasick, D. W.; Stähelin, J.; Wallington, T. J.; Steinbacher, M.; Schultz, M.; Cooper, O. R.

2017-12-01

Tropospheric ozone is a greenhouse gas, a key component of atmospheric chemistry, and is detrimental to human health and plant productivity. The historic surface ozone record 1896-1975 has been constructed from measurements selected for (a) instrumentation whose ozone response can be traced to modern tropospheric ozone measurement standards, (b) samples taken when there is low probability of chemical interference and (c) sampling locations, heights and times when atmospheric mixing will minimise vertical gradients of ozone in the planetary boundary layer above and around the measurement location. Early measurements with the Schönbein filter paper technique cannot be related to modern methods with any degree of confidence. The potassium iodide-arsenite technique used at Montsouris for 1876-1910 is valid for measuring ozone; however, due to the presence of the interfering gases sulfur dioxide, ammonia and nitrogen oxides, the measured ozone concentrations are not representative of the regional atmosphere. The use of these data sets for trend analyses is not recommended. In total, 58 acceptable sets of measurements are currently identified, commencing in Europe in 1896, Greenland in 1932 and globally by the late 1950's. Between 1896 and 1944 there were 21 studies (median duration 5 days) with a median mole fraction of 23 nmol mol-1 (range of study averages 15-62 nmol mol-1). Between 1950 and 1975 there were 37 studies (median duration approx. 21 months) with a median mole fraction of 22 nmol mol-1 (range of study averages 13-49 nmol mol-1), all measured under conditions likely to give ozone mole fractions similar to those in the planetary boundary layer. These time series are matched with modern measurements from the Tropospheric Ozone Assessment Report (TOAR) Ozone Database and used to examine changes between the historic and modern observations. These historic ozone levels are higher than previously accepted for surface ozone in the late 19th early 20th Century

Growth mechanisms for Si epitaxy on O atomic layers: Impact of O-content and surface structure

Energy Technology Data Exchange (ETDEWEB)

Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Billen, Arne [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Moussa, Alain; Caymax, Matty; Bender, Hugo [Imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Heyns, Marc [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Delabie, Annelies [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium)

2016-10-30

Highlights: • O{sub 3} or O{sub 2} exposures on H-Si(100) result in O ALs with different surface structures. • Si-EPI on O AL using O{sub 3} process is by direct epitaxial growth mechanism. • Si-EPI on O AL using O{sub 2} process is by epitaxial lateral overgrowth mechanism. • Distortions by O AL, SiH{sub 4} flux rate and Si thickness has an impact on Si-EPI quality. - Abstract: The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O{sub 3}) or oxygen (O{sub 2}) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH{sub 4}) at 500 °C. After O{sub 3} exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH{sub 4} reactants, allowing more time for surface diffusion. After O{sub 2} exposure, the O atoms are present in the form of SiO{sub x} clusters. Regions of hydrogen-terminated Si remain present between the SiO{sub x} clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

Understanding Long-Term Variations in Surface Ozone in United States (U.S. National Parks

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Deborah McGlynn

2018-03-01

Full Text Available Long-term surface ozone observations at 25 National Park Service sites across the United States were analyzed for processes on varying time scales using a time scale decomposition technique, the Ensemble Empirical Mode Decomposition (EEMD. Time scales of interest include the seasonal cycle, large-scale climate oscillations, and long-term (>10 years trends. Emission reductions were found to have a greater impact on sites that are nearest major urban areas. Multidecadal trends in surface ozone were increasing at a rate of 0.07 to 0.37 ppbv year−1 before 2004 and decreasing at a rate of −0.08 to −0.60 ppbv year−1 after 2004 for sites in the East, Southern California, and Northwestern Washington. Sites in the Intermountain West did not experience a reversal of trends from positive to negative until the mid- to late 2000s. The magnitude of the annual amplitude (=annual maximum–minimum decreased at eight sites, two in the West, two in the Intermountain West, and four in the East, by 5–20 ppbv and significantly increased at three sites; one in Alaska, one in the West, and one in the Intermountain West, by 3–4 ppbv. Stronger decreases in the annual amplitude occurred at a greater proportion of sites in the East (4/6 sites than in the West/Intermountain West (4/19 sites. The date of annual maximums and/or minimums has changed at 12 sites, occurring 10–60 days earlier in the year. There appeared to be a link between the timing of the annual maximum and the decrease in the annual amplitude, which was hypothesized to be related to a decrease in ozone titration resulting from NOx emission reductions. Furthermore, it was found that a phase shift of the Pacific Decadal Oscillation (PDO, from positive to negative, in 1998–1999 resulted in increased occurrences of La Niña-like conditions. This shift had the effect of directing more polluted air masses from East Asia to higher latitudes over the North American continent. The change in the

Impact of near-surface atmospheric composition on ozone formation in Russia

Science.gov (United States)

Berezina, Elena; Moiseenko, Konstantin; Skorokhod, Andrey; Belikov, Igor; Pankratova, Natalia; Elansky, Nikolai

2017-04-01

natural and anthropogenic sources of VOCs. The quantitative contribution of aromatic VOCs to ozone formation in urban areas and in Russian regions along the railway is estimated. The greatest impact of aromatic VOCs to ozone formation (up to 7.5 ppb of O3) is obtained in the large cities along the Trans-Siberian Railway, with the highest concentrations of aromatic VOCs (1-1.7 ppb) and nitrogen oxides (> 20 ppb) being observed. The results show a significant contribution of anthropogenic emissions of VOCs to the photochemical ozone generation (30-50%) in the large cities along the Trans-Siberian railway in hot and dry weather conditions against natural isoprene emissions determining the regional balance of ground-level ozone in summer. This study was supported by the Russian Science Foundation (grant no. 14-47-00049) and by the Russian Foundation for Basic Research (grant no. 16-35-00158). References: 1. Xie, X., Shao, M., Liu, Y., Lu, S., Chang, C. C., and Chen, Z. M. // Atmos. Environ., 2008, 42, pp. 6000-6010. 2. Guenther, A., Geron, C., Pierce, T., Lamb, B., Harley, P., Fall, R. // Atmospheric Environment, 2000, 34, pp. 2205-2230. 3. Dreyfus, G. B., Schade G. W., Goldstein A. H. // J. Geophys. Res., 2002, 107(D19): 4365, doi:10.1029/2001JD001490.

Coupled effects of atmospheric N/sub 2/O and O/sub 3/ on the earth's climate

Energy Technology Data Exchange (ETDEWEB)

Wang, W C; Sze, N D

1980-08-07

Increased application of nitrogen fertilizer could perturb the atmospheric nitrogen cycle and might lead to a possible increase in atmospheric N/sub 2/O. N/sub 2/O plays an important role in stratospheric chemistry as well as in the global radiation budget. Recent studies suggest that perturbation of local ozone could also significantly affect the global climate. Here we show that a doubling in the present day N/sub 2/O level might significantly perturb the distribution of O/sub 3/ and HNO/sub 3/, and that the associated climatic feedbacks from O/sub 3/ and HNO/sub 3/ perturbations could contribute as much as 0.23 K warming of the surface temperature, in addition to 0.44 K directly caused by N/sub 2/O doubling.

Ozone impacts of gas-aerosol uptake in global chemistry transport models

Science.gov (United States)

Stadtler, Scarlet; Simpson, David; Schröder, Sabine; Taraborrelli, Domenico; Bott, Andreas; Schultz, Martin

2018-03-01

The impact of six heterogeneous gas-aerosol uptake reactions on tropospheric ozone and nitrogen species was studied using two chemical transport models, the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP MSC-W) and the European Centre Hamburg general circulation model combined with versions of the Hamburg Aerosol Model and Model for Ozone and Related chemical Tracers (ECHAM-HAMMOZ). Species undergoing heterogeneous reactions in both models include N2O5, NO3, NO2, O3, HNO3, and HO2. Since heterogeneous reactions take place at the aerosol surface area, the modelled surface area density (Sa) of both models was compared to a satellite product retrieving the surface area. This comparison shows a good agreement in global pattern and especially the capability of both models to capture the extreme aerosol loadings in east Asia. The impact of the heterogeneous reactions was evaluated by the simulation of a reference run containing all heterogeneous reactions and several sensitivity runs. One reaction was turned off in each sensitivity run to compare it with the reference run. The analysis of the sensitivity runs confirms that the globally most important heterogeneous reaction is the one of N2O5. Nevertheless, NO2, HNO3, and HO2 heterogeneous reactions gain relevance particularly in east Asia due to the presence of high NOx concentrations and high Sa in the same region. The heterogeneous reaction of O3 itself on dust is of minor relevance compared to the other heterogeneous reactions. The impacts of the N2O5 reactions show strong seasonal variations, with the biggest impacts on O3 in springtime when photochemical reactions are active and N2O5 levels still high. Evaluation of the models with northern hemispheric ozone surface observations yields a better agreement of the models with observations in terms of concentration levels, variability, and temporal correlations at most sites when the heterogeneous reactions are

Surface resistance of YBa2Cu3O7 films deposited on LaGaO3 substrates

International Nuclear Information System (INIS)

Cooke, D.W.; Gray, E.R.; Houlton, R.J.; Javadi, H.H.S.; Maez, M.A.; Bennett, B.L.; Rusnak, B.; Meyer, E.A.; Arendt, P.N.; Beery, J.G.; Brown, D.R.; Garzon, F.H.; Raistriek, I.D.; Bolmaro, B.; Elliott, N.E.; Rollett, A.D.; Klein, N.; Muller, G.; Orbach, S.; Piel, H.; Josefowicz, J.Y.; Rensch, O.B.; Drabeck, L.; Gruner, G.

1989-01-01

Superconducting films of YBa 2 Cu 3 O 7 deposited onto LaGaO 3 substrates were prepared by e-beam and magnetron sputtering techniques. Surface resistance measurements made at 22 GHz, 86 GHz, and 148 GHz show that these films are superior to those deposited by similar techniques onto SrTiO 3 . Typical surface resistance values measured at 22 GHz and 12 K are ∼2 m(cgom) with the lowest value being 0.2 m(cgom), which is only 2 to 4 times higher than Nb. The surface resistance is proportional to the square of the measuring frequency

Total column density variations of ozone (O3 O3 O3) in presence of ...

Indian Academy of Sciences (India)

−3). In case of O4, an absorbance of. O2–O2 by Greenblatt et al (1990) is calculated as absorbance A is given by: A = σ[O2]2 l,. (2) where l is the optical path length (cm), [O2] is the concentration of oxygen (molecules cm. −3), σ is the absorption cross section with the unit of cm5 molecule. −2. The absorption cross sections of.

Importance of A Priori Vertical Ozone Profiles for TEMPO Air Quality Retrievals

Science.gov (United States)

Johnson, M. S.; Sullivan, J. T.; Liu, X.; Zoogman, P.; Newchurch, M.; Kuang, S.; McGee, T. J.; Leblanc, T.

2017-12-01

Ozone (O3) is a toxic pollutant which plays a major role in air quality. Typically, monitoring of surface air quality and O3 mixing ratios is conducted using in situ measurement networks. This is partially due to high-quality information related to air quality being limited from space-borne platforms due to coarse spatial resolution, limited temporal frequency, and minimal sensitivity to lower tropospheric and surface-level O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite is designed to address the limitations of current space-based platforms and to improve our ability to monitor North American air quality. TEMPO will provide hourly data of total column and vertical profiles of O3 with high spatial resolution to be used as a near-real-time air quality product. TEMPO O3 retrievals will apply the Smithsonian Astrophysical Observatory profile algorithm developed based on work from GOME, GOME-2, and OMI. This algorithm is suggested to use a priori O3 profile information from a climatological data-base developed from long-term ozone-sonde measurements (tropopause-based (TB-Clim) O3 climatology). This study evaluates the TB-Clim dataset and model simulated O3 profiles, which could potentially serve as a priori O3 profile information in TEMPO retrievals, from near-real-time data assimilation model products (NASA GMAO's operational GEOS-5 FP model and reanalysis data from MERRA2) and a full chemical transport model (CTM), GEOS-Chem. In this study, vertical profile products are evaluated with surface (0-2 km) and tropospheric (0-10 km) TOLNet observations and the theoretical impact of individual a priori profile sources on the accuracy of TEMPO O3 retrievals in the troposphere and at the surface are presented. Results indicate that while the TB-Clim climatological dataset can replicate seasonally-averaged tropospheric O3 profiles, model-simulated profiles from a full CTM resulted in more accurate tropospheric and surface-level O3 retrievals from

ELIMINACIÓN DE COLORANTES CATIÓNICOS USANDO OZONO, ZEOLITA NATURAL Y OZONO/ZEOLITA CATIONIC DYES REMOVAL USING OZONE, NATURAL ZEOLITE, AND OZONE/ZEOLITE

Directory of Open Access Journals (Sweden)

Héctor Valdés

2009-12-01

Full Text Available En este trabajo se comparan resultados experimentales de remoción azul de metileno (MB utilizando tratamientos basados en la oxidación con ozono (O3, la adsorción con zeolita natural (ZN, y tratamiento simultáneo de adsorción y oxidación con ozono en presencia de zeolita natural (O3/ZN. Se evalúa, a escala de laboratorio, el efecto del pH (2-8 y la presencia de sustancias atrapadoras radicales libres (iones acetatos en la velocidad de remoción y en la eficiencia de los procesos. Los experimentos se realizaron en un reactor diferencial compuesto por un estanque de 1 dm³ y una columna de 19 cm³ de capacidad. El ozono fue generado a razón de 5 g O3/h. Los resultados mostraron que el sistema simultáneo de oxidación/adsorción O3/ZN incrementa la velocidad de remoción del MB con respecto a los procesos separados de ozonización y adsorción con zeolita. En presencia de sustancias atrapadoras de radicales, se observó un 70% de disminución en la velocidad de remoción de MB cuando se empleó el tratamiento con O3 y sólo un 25% cuando se utiliza el tratamiento combinado O3/ZN. Los resultados sugieren que la reacción de oxidación del MB en el sistema tiene lugar fundamentalmente sobre la superficie de la zeolita.This paper compares experimental results on methylene blue (MB removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8, and the presence of radical scavengers (sodium acetate on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are

The Role of Catalyst Properties on Methanol Oxidation over V{sub 2}O{sub 5}-TiO{sub 2} Using Ozone

Energy Technology Data Exchange (ETDEWEB)

Sahle-Demessie, Endalkachew [US EPA, Office of Research and Development, NRML (United States)], E-mail: sahle-demessie.endalkachew@epa.gov; Almquist, Catherine B. [Miami University, Paper Science and Chemical Engineering Department (United States); Sehker, Sridara Chandra [US EPA, Office of Research and Development, NRML (United States)

2008-08-15

Oxidation of methanol over V{sub 2}O{sub 5} catalysts supported on anatase TiO{sub 2} that were prepared using sol-gel formation and impregnation procedures were investigated. The effects of incorporating Mg in sol-gel to influence the properties of the catalyst were also studied. The process provides an alternative low temperature reaction pathway for reducing emissions of hazardous air pollutant (HAPs) such as methanol and total reduced sulfur compounds (TRS) from pulp and paper mills. The bulk and surface composition of the catalysts were determined by XRD and SEM-EDAX, respectively. The X-ray diffraction patterns of the vanadia-titania catalysts showed mainly the anatase phase of TiO{sub 2}. Temperature programmed desorption of methanol from the different catalyst showed that the {alpha} and {beta} peaks differ significantly with V content and addition of Mg. The combination of gas phase and surface reactions on the V/TiO{sub 2} catalysts reduced the amount of ozone required for high degradation of methanol to mainly CO{sub x} with small quantities of methyl formate. In the absence of ozone the catalysts showed very low activity. It is hypothesized that the ozone is directly influencing the V{sup 4+} and V{sup 5+} redox cycle of the catalyst. Oxidation of methanol is influenced by the operation variables and catalyst properties. The results of this study revealed that the V content has significant influence on the catalyst activity, and the optimum vanadia loading of about 6 wt%. Higher turnover frequencies were observed over sol-gel catalysts than with catalysts prepared by the impregnation method.

Classical and quasi-classical trajectory calculations of isotope exchange and ozone formation proceeding through O+O2 collision complexes

Science.gov (United States)

Baker, Thomas A.; Gellene, Gregory I.

2002-10-01

The isotope exchange reaction, and the three-body ozone formation rate proceeding through an ozone complex, have been studied by classical and quasi-classical trajectory techniques. The exchange rate studies indicate that the rate of this reaction is dominantly sensitive to the O+O2 entrance channel characteristics of the potential energy surface. A detailed consideration of the dynamics of the intermediate ozone complex reveals three important classes. In one class, the complex adopts an ozonelike geometry, largely undergoing asymmetric stretchinglike motion until it dissociates. In a second class, the oxygen atom and molecule never visit the ozonelike geometry but rather remain separated by relatively large distances trapped near the angular momentum barrier in the entrance channel of a pseudo-effective potential. These complexes, which cannot undergo exchange, are, nevertheless, found to contribute significantly to ozone formation at high density of the third body suggesting that the association of the high-density effective formation rate constant with twice the exchange rate may not be valid. The third class can be considered a hybrid of the first two, spending some time as an ozonelike complex and some time as a large atom-diatomic complex. This third class provides a mechanism for rearranging atom locations in the complex (e.g., end and middle position swapping) and, consequently, would not be well accounted for by statistical treatments of the ozone complex based on a single ozonelike reference geometry. In general, the survival time distributions of the complexes are found to be nonexponential. However, when the detailed survival time distributions are coupled with a Lennard-Jones collision model for the stabilization step, the experimental ozone formation rate can be adequately modeled over a broad range of temperature and density.

Two-phase ozonation of chlorinated organics

International Nuclear Information System (INIS)

Bhattacharyya, D.; Freshour, A.; West, D.

1995-01-01

In the last few years the amount of research being conducted in the field of single-phase ozonation has grown extensively. However, traditional aqueous-phase ozonation systems are limited by a lack of selective oxidation potential, low ozone solubility in water, and slow intermediate decomposition rates. Furthermore, ozone may decompose before it can be utilized for pollutant destruction since ozone can be highly unstable in aqueous solutions. Naturally occurring compounds such as NaHCO 3 also affect ozone reactions by inhibiting the formation of OH-free radicals. To compensate for these factors, excess ozone is typically supplied to a reactor. Since ozone generation requires considerable electric power consumption (16 - 24 kWh/kg of O 3 ), attempts to enhance the ozone utilization rate and stability should lead to more efficient application of this process to hazardous waste treatment. To improve the process, ozonation may be more efficiently carried out in a two-phase system consisting of an inert solvent (saturated with O 3 ) contacted with an aqueous phase containing pollutants. The non-aqueous phase must meet the following criteria: (1) non-toxic, (2) very low vapor pressure, (3) high density (for ease of separation), (4) complete insolubility in water, (5) reusability, (6) selective pollutant extractability, (7) high oxidant solubility, and (8) extended O 3 stability. Previously published studies (1) have indicated that a number of fluorinated hydrocarbon compounds fit these criteria. For this project, FC40 (a product of 3M Co.) was chosen due to its low vapor pressure (3 mm Hg) and high specific gravity (1.9). The primary advantages of the FC40 solvent are that it is non-toxic, reusable, has an ozone solubility 10 times that of water, and that 85 % of the ozone remains in the solvent even after 2 hours. This novel two-phase process has been utilized to study the rapid destruction of organic chlorine compounds and organic mixtures

Experimental investigation on oxidation kinetics of germanium by ozone

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaolei, E-mail: wangxiaolei@ime.ac.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Zhao, Zhiqian; Xiang, Jinjuan [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Wang, Wenwu, E-mail: wangwenwu@ime.ac.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Zhang, Jing, E-mail: zhangj@ncut.edu.cn [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Microelectronics Department, North China University of Technology, Beijing 100041 (China); Zhao, Chao; Ye, Tianchun [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

2016-12-30

Highlights: • Kinetics mechanism of Ge surface oxidation by ozone at low temperature is experimentally investigated. • The growth process contains initially linear growth region and following parabolic growth region. • The GeO{sub x} thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. • The linear growth region includes the oxidation of two topmost Ge layers, and the oxidation of third layer and following layers of Ge is diffusion limited. • The activation energies for linear and parabolic regions are 0.04 and 0.55 eV, respectively. - Abstract: Oxidation kinetics of germanium surface by ozone at low temperature (≤400 °C) is experimentally investigated. The growth process contains two regions: initial linear growth region and following parabolic growth region. The GeO{sub x} thickness vs. oxidation time plot obeys the well-known Deal-Grove or linear parabolic model. The linear growth region contains reaction of oxygen atoms with surface bond and back bonds of outmost Ge layer. And the activation energy is experimentally estimated to be 0.06 eV. Such small activation energy indicates that the linear growth region is nearly barrier-less. The parabolic growth region starts when the oxygen atoms diffuse into back bonds of second outmost Ge layers. And the activation energy for this process is found to be 0.54 eV. Furthermore, in the ozone oxidation it is not O{sub 3} molecules but O radicals that go through the GeO{sub x} film.

Combining multiple regression and principal component analysis for accurate predictions for column ozone in Peninsular Malaysia

Science.gov (United States)

Rajab, Jasim M.; MatJafri, M. Z.; Lim, H. S.

2013-06-01

This study encompasses columnar ozone modelling in the peninsular Malaysia. Data of eight atmospheric parameters [air surface temperature (AST), carbon monoxide (CO), methane (CH4), water vapour (H2Ovapour), skin surface temperature (SSKT), atmosphere temperature (AT), relative humidity (RH), and mean surface pressure (MSP)] data set, retrieved from NASA's Atmospheric Infrared Sounder (AIRS), for the entire period (2003-2008) was employed to develop models to predict the value of columnar ozone (O3) in study area. The combined method, which is based on using both multiple regressions combined with principal component analysis (PCA) modelling, was used to predict columnar ozone. This combined approach was utilized to improve the prediction accuracy of columnar ozone. Separate analysis was carried out for north east monsoon (NEM) and south west monsoon (SWM) seasons. The O3 was negatively correlated with CH4, H2Ovapour, RH, and MSP, whereas it was positively correlated with CO, AST, SSKT, and AT during both the NEM and SWM season periods. Multiple regression analysis was used to fit the columnar ozone data using the atmospheric parameter's variables as predictors. A variable selection method based on high loading of varimax rotated principal components was used to acquire subsets of the predictor variables to be comprised in the linear regression model of the atmospheric parameter's variables. It was found that the increase in columnar O3 value is associated with an increase in the values of AST, SSKT, AT, and CO and with a drop in the levels of CH4, H2Ovapour, RH, and MSP. The result of fitting the best models for the columnar O3 value using eight of the independent variables gave about the same values of the R (≈0.93) and R2 (≈0.86) for both the NEM and SWM seasons. The common variables that appeared in both regression equations were SSKT, CH4 and RH, and the principal precursor of the columnar O3 value in both the NEM and SWM seasons was SSKT.

Investigation on the dominant key to achieve superior Ge surface passivation by GeOx based on the ozone oxidation

International Nuclear Information System (INIS)

Wang, Xiaolei; Xiang, Jinjuan; Wang, Wenwu; Xiong, Yuhua; Zhang, Jing; Zhao, Chao

2015-01-01

Highlights: • The dominant key to achieve superior Ge passivation by GeO x is investigated. • The interface state density decreases with increasing the GeO x thickness. • The Ge 3+ oxide component is the dominant key to passivate the Ge surface. • The atomic structure at the GeO x /Ge interface is built by XPS. - Abstract: The dominant key to achieve superior Ge surface passivation by GeO x interfacial layer is investigated based on ozone oxidation. The interface state density (D it ) measured from low temperature conduction method is found to decrease with increasing the GeO x thickness (0.26–1.06 nm). The X-ray photoelectron spectroscopy (XPS) is employed to demonstrate the interfacial structure of GeO x /Ge with different GeO x thicknesses. And the XPS results show that Ge 3+ oxide component is responsible to the decrease of the D it due to the effective passivation of Ge dangling bonds. Therefore, the formation of Ge 3+ component is the dominant key to achieve low D it for Ge gate stacks. Our work confirms that the same physical mechanism determines the Ge surface passivation by the GeO x regardless of the oxidation methods to grow the GeO x interfacial layer. As a result, to explore a growth process that can realize sufficient Ge 3+ component in the GeO x interlayer as thin as possible is important to achieve both equivalent oxide thickness scaling and superior interfacial property simultaneously. This conclusion is helpful to engineer the optimization of the Ge gate stacks.

Temporal Characterisation of Ground-level Ozone Concentration in Klang Valley

Science.gov (United States)

Izzah Mohamad Hashim, Nur; Noor, Norazian Mohamed; Yasina Yusof, Sara

2018-03-01

In Malaysia, ground-level ozone (O3) is one of the most significant air pollutants due to the increasing sources of ozone precursors. Hence, the surface O3 concentration should have received substantial attention because of its negative effects to human health, vegetation and the environment. In this study, hourly air pollutants dataset (i.e O3, Carbon monoxide (CO), Nitrogen dioxide (NO2), Particulate matter (PM10), Non-methane hydrocarbon (NmHC), Sulphur dioxide (SO2)) and weather parameters (i.e. wind speed (WS), wind direction (WD), temperature (T), ultraviolet B (UVB)) for ten years period (2003-2012) in Klang Valley were selected for analysis in this study. Two monitoring stations were selected that are Petaling Jaya and Shah Alam. The aim of the study is to determine the diurnal variations of O3 concentrations according to the seasonal monsoon and the correlation between the ground-level O3 concentration and others parameter. A high concentration of ground-level O3 was observed during the first transition (April to May) for both of the stations. While at a low surface, O3 concentration was found out during the southwest monsoon within June to September. Pearson correlation was used to find the correlation between the O3 concentration and all other pollutants and weather parameters. Most of the relationship between O3concentrationswas positively correlated with NO2 and negative relationship was found out with NMHC. These results were expected since these pollutants are known as the O3 precursors. Besides that, O3 concentration and its precursors show a positive significant correlation with all meteorological factors except for relative humidity.

Temporal Characterisation of Ground-level Ozone Concentration in Klang Valley

Directory of Open Access Journals (Sweden)

Mohamad Hashim Nur Izzah

2018-01-01

Full Text Available In Malaysia, ground-level ozone (O3 is one of the most significant air pollutants due to the increasing sources of ozone precursors. Hence, the surface O3 concentration should have received substantial attention because of its negative effects to human health, vegetation and the environment. In this study, hourly air pollutants dataset (i.e O3, Carbon monoxide (CO, Nitrogen dioxide (NO2, Particulate matter (PM10, Non-methane hydrocarbon (NmHC, Sulphur dioxide (SO2 and weather parameters (i.e. wind speed (WS, wind direction (WD, temperature (T, ultraviolet B (UVB for ten years period (2003-2012 in Klang Valley were selected for analysis in this study. Two monitoring stations were selected that are Petaling Jaya and Shah Alam. The aim of the study is to determine the diurnal variations of O3 concentrations according to the seasonal monsoon and the correlation between the ground-level O3 concentration and others parameter. A high concentration of ground-level O3 was observed during the first transition (April to May for both of the stations. While at a low surface, O3 concentration was found out during the southwest monsoon within June to September. Pearson correlation was used to find the correlation between the O3 concentration and all other pollutants and weather parameters. Most of the relationship between O3concentrationswas positively correlated with NO2 and negative relationship was found out with NMHC. These results were expected since these pollutants are known as the O3 precursors. Besides that, O3 concentration and its precursors show a positive significant correlation with all meteorological factors except for relative humidity.

Measurement of Ozone Production Sensor

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M. Cazorla

2010-05-01

Full Text Available A new ambient air monitor, the Measurement of Ozone Production Sensor (MOPS, measures directly the rate of ozone production in the atmosphere. The sensor consists of two 11.3 L environmental chambers made of UV-transmitting Teflon film, a unit to convert NO₂ to O₃, and a modified ozone monitor. In the sample chamber, flowing ambient air is exposed to the sunlight so that ozone is produced just as it is in the atmosphere. In the second chamber, called the reference chamber, a UV-blocking film over the Teflon film prevents ozone formation but allows other processes to occur as they do in the sample chamber. The air flows that exit the two chambers are sampled by an ozone monitor operating in differential mode so that the difference between the two ozone signals, divided by the exposure time in the chambers, gives the ozone production rate. High-efficiency conversion of NO₂ to O₃ prior to detection in the ozone monitor accounts for differences in the NO_x photostationary state that can occur in the two chambers. The MOPS measures the ozone production rate, but with the addition of NO to the sampled air flow, the MOPS can be used to study the sensitivity of ozone production to NO. Preliminary studies with the MOPS on the campus of the Pennsylvania State University show the potential of this new technique.

Ozone depletion in the interstitial air of the seasonal snowpack in northern Japan

Directory of Open Access Journals (Sweden)

Momoko Nakayama

2015-02-01

Full Text Available To examine the behaviour of ozone (O3 in the seasonal snowpack, measurements were taken of O3 and CO2 in the interstitial air on Rishiri Island, which is located in northern Japan, during the 2010/11 winter season. Exhibiting variation on timescales ranging from several minutes to several days, the atmospheric O3 in the surface air generally increased from December (38 ppb to April (52 ppb. The ozone mixing ratio sharply decreased below the snow surface. Whereas the CO2 data in the interstitial air indicated that a rapid exchange between the snow and the atmosphere occurred intermittently, the O3 mixing ratio remained low and constant (<5 ppb in the snowpack interior. The vertical profile of the O3 mixing ratio indicates that the e-folding lifetime of the O3 loss reaction was 5.0±2.3 minutes during the day and 10.0±6.3 minutes at night, suggesting photochemical O3 depletion occurred during the daytime. Kinetic experiments using ambient (maritime air and snow indicate that the photochemical O3 loss is proportional to the solar radiation and that the O3 loss rate decreases as dawn approaches during the night. The result of the kinetic experiments using artificial O3 in the pure air and snow suggests the important role of gaseous species in the ambient air towards O3 depletion.

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

Science.gov (United States)

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.; Berg, Larry K.; Fast, Jerome D.; Easter, Richard C.; Shrivastava, Manish; Thomas, Jennie L.

2017-10-01

In this study, the WRF-Chem regional model is updated to improve simulated short-lived pollutants (e.g., aerosols, ozone) in the Arctic. Specifically, we include in WRF-Chem 3.5.1 (with SAPRC-99 gas-phase chemistry and MOSAIC aerosols) (1) a correction to the sedimentation of aerosols, (2) dimethyl sulfide (DMS) oceanic emissions and gas-phase chemistry, (3) an improved representation of the dry deposition of trace gases over seasonal snow, and (4) an UV-albedo dependence on snow and ice cover for photolysis calculations. We also (5) correct the representation of surface temperatures over melting ice in the Noah Land Surface Model and (6) couple and further test the recent KF-CuP (Kain-Fritsch + Cumulus Potential) cumulus parameterization that includes the effect of cumulus clouds on aerosols and trace gases. The updated model is used to perform quasi-hemispheric simulations of aerosols and ozone, which are evaluated against surface measurements of black carbon (BC), sulfate, and ozone as well as airborne measurements of BC in the Arctic. The updated model shows significant improvements in terms of seasonal aerosol cycles at the surface and root mean square errors (RMSEs) for surface ozone, aerosols, and BC aloft, compared to the base version of the model and to previous large-scale evaluations of WRF-Chem in the Arctic. These improvements are mostly due to the inclusion of cumulus effects on aerosols and trace gases in KF-CuP (improved RMSE for surface BC and BC profiles, surface sulfate, and surface ozone), the improved surface temperatures over sea ice (surface ozone, BC, and sulfate), and the updated trace gas deposition and UV albedo over snow and ice (improved RMSE and correlation for surface ozone). DMS emissions and chemistry improve surface sulfate at all Arctic sites except Zeppelin, and correcting aerosol sedimentation has little influence on aerosols except in the upper troposphere.

Generation and Reduction of NOx on Air-Fed Ozonizers

Science.gov (United States)

Ehara, Yoshiyasu; Amemiya, Yusuke; Yamamoto, Toshiaki

A generation and reduction of NOx on air-fed ozonizers using a ferroelectric packed bed reactor have been experimentally investigated. The reactors packed with CaTiO3, SrTiO3 and BaTiO3 pellets are examined for ozone generation. An ac voltage is applied to the reactor to generate partial discharge. Ozone concentration and the different nitrogen oxides at downstream of the packed bed reactor were measured with UV absorption ozone monitor and a Fourier transform infrared spectroscope respectively. The dielectric constant of packed ferroelectric pellets influences the discharge characteristic, ozone and NOx generations are varied by the dielectric constant value. Focusing on a discharge pulse current and maximum discharge magnitude, the ferroelectric packed bed plasma reactors have been evaluated on nitrogen oxide and ozone generated concentrations.

Intra-urban spatial variability of surface ozone in Riverside, CA: viability and validation of low-cost sensors

Science.gov (United States)

Sadighi, Kira; Coffey, Evan; Polidori, Andrea; Feenstra, Brandon; Lv, Qin; Henze, Daven K.; Hannigan, Michael

2018-03-01

Sensor networks are being more widely used to characterize and understand compounds in the atmosphere like ozone (O3). This study employs a measurement tool, called the U-Pod, constructed at the University of Colorado Boulder, to investigate spatial and temporal variability of O3 in a 200 km2 area of Riverside County near Los Angeles, California. This tool contains low-cost sensors to collect ambient data at non-permanent locations. The U-Pods were calibrated using a pre-deployment field calibration technique; all the U-Pods were collocated with regulatory monitors. After collocation, the U-Pods were deployed in the area mentioned. A subset of pods was deployed at two local regulatory air quality monitoring stations providing validation for the collocation calibration method. Field validation of sensor O3 measurements to minute-resolution reference observations resulted in R2 and root mean squared errors (RMSEs) of 0.95-0.97 and 4.4-5.9 ppbv, respectively. Using the deployment data, ozone concentrations were observed to vary on this small spatial scale. In the analysis based on hourly binned data, the median R2 values between all possible U-Pod pairs varied from 0.52 to 0.86 for ozone during the deployment. The medians of absolute differences were calculated between all possible pod pairs, 21 pairs total. The median values of those median absolute differences for each hour of the day varied between 2.2 and 9.3 ppbv for the ozone deployment. Since median differences between U-Pod concentrations during deployment are larger than the respective root mean square error values, we can conclude that there is spatial variability in this criteria pollutant across the study area. This is important because it means that citizens may be exposed to more, or less, ozone than they would assume based on current regulatory monitoring.

Surface ozone measurements in the southwest of the Iberian Peninsula (Huelva, Spain).

Science.gov (United States)

Carnero, Jose A Adame; Bolívar, Juan P; de la Morena, Benito A

2010-02-01

Photochemical ozone pollution of the lower troposphere (LT) is a very complex process involving meteorological, topographic emissions and chemical parameters. Ozone is considered the most important air pollutant in rural, suburban and industrial areas of many sites in the world since it strongly affects human health, vegetation and forest ecosystems, and its increase during the last decades has been significant. In addition, ozone is a greenhouse gas that contributes to climate change. For these reasons, it is necessary to carry out investigations that determine the behaviour of ozone at different locations. The aim of this work is to understand the levels and temporal variations of surface ozone in an industrial-urban region of the Southwest Iberian Peninsula. The study is based on ozone hourly data recorded during a 6-year period, 2000 to 2005 at four stations and meteorological data from a coastal station. The stations used were El Arenosillo and Cartaya--both coastal stations, Huelva--an urban site and Valverde--an inland station 50 km away from the coastline. The general characteristics of the ozone series, seasonal and daily ozone cycles as well as number of exceedances of the threshold established in the European Ozone Directive have been calculated and analysed. Analysis of the meteorological data shows that winter-autumn seasons are governed by the movement of synoptic weather systems; however, in the spring-summer seasons, both synoptic and mesoescale conditions exist. Average hourly ozone concentrations range from 78.5 +/- 0.1 microg m(-3) at Valverde to 57.8 +/- 0.2 microg m(-3) at Huelva. Ozone concentrations present a seasonal variability with higher values in summer months, while in wintertime, lower values are recorded. A seasonal daily evolution has also been found with minimum levels around 08:00 UTC, which occurs approximately 1-1.5 h after sunrise, whereas the maximum is reached at about 16:00 UTC. Furthermore, during summer, the maximum value

A revised global ozone dry deposition estimate based on a new two-layer parameterisation for air-sea exchange and the multi-year MACC composition reanalysis

Science.gov (United States)

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

2018-03-01

Dry deposition at the Earth's surface is an important sink of atmospheric ozone. Currently, dry deposition of ozone to the ocean surface in atmospheric chemistry models has the largest uncertainty compared to deposition to other surface types, with implications for global tropospheric ozone budget and associated radiative forcing. Most global models assume that the dominant term of surface resistance in the parameterisation of ozone dry deposition velocity at the oceanic surface is constant. There have been recent mechanistic parameterisations for air-sea exchange that account for the simultaneous waterside processes of ozone solubility, molecular diffusion, turbulent transfer, and first-order chemical reaction of ozone with dissolved iodide and other compounds, but there are questions about their performance and consistency. We present a new two-layer parameterisation scheme for the oceanic surface resistance by making the following realistic assumptions: (a) the thickness of the top water layer is of the order of a reaction-diffusion length scale (a few micrometres) within which ozone loss is dominated by chemical reaction and the influence of waterside turbulent transfer is negligible; (b) in the water layer below, both chemical reaction and waterside turbulent transfer act together and are accounted for; and (c) chemical reactivity is present through the depth of the oceanic mixing layer. The new parameterisation has been evaluated against dry deposition velocities from recent open-ocean measurements. It is found that the inclusion of only the aqueous iodide-ozone reaction satisfactorily describes the measurements. In order to better quantify the global dry deposition loss and its interannual variability, modelled 3-hourly ozone deposition velocities are combined with the 3-hourly MACC (Monitoring Atmospheric Composition and Climate) reanalysis ozone for the years 2003-2012. The resulting ozone dry deposition is found to be 98.4 ± 30.0 Tg O3 yr-1 for the ocean

Ozone visible symptoms and reduced root biomass in the subalpine species Pinus uncinata after two years of free-air ozone fumigation

International Nuclear Information System (INIS)

Díaz-de-Quijano, Maria; Schaub, Marcus; Bassin, Seraina; Volk, Matthias; Peñuelas, Josep

2012-01-01

Concentrations of ozone often exceed the thresholds of forest protection in the Pyrenees, but the effect of ozone on Pinus uncinata, the dominant species in subalpine forests in this mountainous range, has not yet been studied. We conducted an experiment of free-air ozone fumigation with saplings of P. uncinata fumigated with ambient O 3 (AOT40 May–Oct: 9.2 ppm h), 1.5 × O 3amb (AOT40 May–Oct: 19.2 ppm h), and 1.8 × O 3amb (AOT40 May–Oct: 32.5 ppm h) during two growing seasons. We measured chlorophyll content and fluorescence, visible injury, gas exchange, and above- and below-ground biomass. Increased exposures to ozone led to a higher occurrence and intensity of visible injury from O 3 and a 24–29% reduction of root biomass, which may render trees more susceptible to other stresses such as drought. P. uncinata is thus a species sensitive to O 3 , concentrations of which in the Pyrenees are already likely affecting this species. - Highlights: ► We assessed sensitivity to O 3 in Pinus uncinata using a free-air O 3 fumigation system. ► Occurrence and intensity of visible injury from O 3 correlated with exposure to O 3 . ► Increased O 3 reduced root biomass 24–29%. ► O 3 weakens P. uncinata, making it more susceptible to other stresses. ► Ambient [O 3 ] in the Pyrenees is thus likely to already be affecting P. uncinata stands. - Ozone concentrations similar to those in the Pyrenees affect Pinus uncinata by reducing root biomass and possibly increasing susceptibility to other stresses.

O3 and NOx Exchange

NARCIS (Netherlands)

Loubet, B.; Castell, J.F.; Laville, P.; Personne, E.; Tuzet, A.; Ammann, C.; Emberson, L.; Ganzeveld, L.; Kowalski, A.S.; Merbold, L.; Stella, P.; Tuovinen, J.P.

2015-01-01

This discussion was based on the background document “Review on modelling atmosphere-biosphere exchange of Ozone and Nitrogen oxides”, which reviews the processes contributing to biosphere-atmosphere exchange of O3 and NOx, including stomatal and non-stomatal exchange of O3 and NO, NO2.

Water Reclamation Using a Ceramic Nanofiltration Membrane and Surface Flushing with Ozonated Water

Science.gov (United States)

Hoang, Anh T.; Okuda, Tetsuji; Takeuchi, Haruka; Tanaka, Hiroaki; Nghiem, Long D.

2018-01-01

A new membrane fouling control technique using ozonated water flushing was evaluated for direct nanofiltration (NF) of secondary wastewater effluent using a ceramic NF membrane. Experiments were conducted at a permeate flux of 44 L/m2h to evaluate the ozonated water flushing technique for fouling mitigation. Surface flushing with clean water did not effectively remove foulants from the NF membrane. In contrast, surface flushing with ozonated water (4 mg/L dissolved ozone) could effectively remove most foulants to restore the membrane permeability. This surface flushing technique using ozonated water was able to limit the progression of fouling to 35% in transmembrane pressure increase over five filtration cycles. Results from this study also heighten the need for further development of ceramic NF membrane to ensure adequate removal of pharmaceuticals and personal care products (PPCPs) for water recycling applications. The ceramic NF membrane used in this study showed approximately 40% TOC rejection, and the rejection of PPCPs was generally low and highly variable. It is expected that the fouling mitigation technique developed here is even more important for ceramic NF membranes with smaller pore size and thus better PPCP rejection. PMID:29671797

Water Reclamation Using a Ceramic Nanofiltration Membrane and Surface Flushing with Ozonated Water

Directory of Open Access Journals (Sweden)

Takahiro Fujioka

2018-04-01

Full Text Available A new membrane fouling control technique using ozonated water flushing was evaluated for direct nanofiltration (NF of secondary wastewater effluent using a ceramic NF membrane. Experiments were conducted at a permeate flux of 44 L/m2h to evaluate the ozonated water flushing technique for fouling mitigation. Surface flushing with clean water did not effectively remove foulants from the NF membrane. In contrast, surface flushing with ozonated water (4 mg/L dissolved ozone could effectively remove most foulants to restore the membrane permeability. This surface flushing technique using ozonated water was able to limit the progression of fouling to 35% in transmembrane pressure increase over five filtration cycles. Results from this study also heighten the need for further development of ceramic NF membrane to ensure adequate removal of pharmaceuticals and personal care products (PPCPs for water recycling applications. The ceramic NF membrane used in this study showed approximately 40% TOC rejection, and the rejection of PPCPs was generally low and highly variable. It is expected that the fouling mitigation technique developed here is even more important for ceramic NF membranes with smaller pore size and thus better PPCP rejection.

Passivation of surface states of α-Fe2O3(0001) surface by deposition of Ga2O3 overlayers: A density functional theory study.

Science.gov (United States)

Ulman, Kanchan; Nguyen, Manh-Thuong; Seriani, Nicola; Gebauer, Ralph

2016-03-07

There is a big debate in the community regarding the role of surface states of hematite in the photoelectrochemical water splitting. Experimental studies on non-catalytic overlayers passivating the hematite surface states claim a favorable reduction in the overpotential for the water splitting reaction. As a first step towards understanding the effect of these overlayers, we have studied the system Ga2O3 overlayers on hematite (0001) surfaces using first principles computations in the PBE+U framework. Our computations suggest that stoichiometric terminations of Ga2O3 overlayers are energetically more favored than the bare surface, at ambient oxygen chemical potentials. Energetics suggest that the overlayers prefer to grow via a layer-plus-island (Stranski-Krastanov) growth mode with a critical layer thickness of 1-2 layers. Thus, a complete wetting of the hematite surface by an overlayer of gallium oxide is thermodynamically favored. We establish that the effect of deposition of the Ga2O3 overlayers on the bare hematite surface is to passivate the surface states for the stoichiometric termination. For the oxygen terminated surface which is the most stable termination under photoelectrochemical conditions, the effect of deposition of the Ga2O3 overlayer is to passivate the hole-trapping surface state.

Multiannual tropical tropospheric ozone columns and the case of the 2015 el Niño event

Science.gov (United States)

Leventidou, Elpida; Eichmann, Kai-Uwe; Weber, Mark; Burrows, John P.

2016-04-01

Stratospheric ozone is well known for protecting the surface from harmful ultraviolet solar radiation whereas ozone in the troposphere plays a more complex role. In the lower troposphere ozone can be extremely harmful for human health as it can oxidize biological tissues and causes respiratory problems. Several studies have shown that the tropospheric ozone burden (300±30Tg (IPCC, 2007)) increases by 1-7% per decade in the tropics (Beig and Singh, 2007; Cooper et al., 2014) which makes the need to monitor it on a global scale crucial. Remote sensing from satellites has been proven to be very useful in providing consistent information of tropospheric ozone concentrations over large areas. Tropical tropospheric ozone columns can be retrieved with the Convective Cloud Differential (CCD) technique (Ziemke et al. 1998) using retrieved total ozone columns and cloud parameters from space-borne observations. We have developed a CCD-IUP algorithm which was applied to GOME/ ERS-2 (1995-2003), SCIAMACHY/ Envisat (2002-2012), and GOME-2/ MetOpA (2007-2012) weighting function DOAS (Coldewey-Egbers et al., 2005, Weber et al., 2005) total ozone data. A unique long-term record of monthly averaged tropical tropospheric ozone columns (20°S - 20°N) was created starting in 1996. This dataset has been extensively validated by comparisons with SHADOZ (Thompson et al., 2003) ozonesonde data and limb-nadir Matching (Ebojie et al. 2014) tropospheric ozone data. The comparison shows good agreement with respect to range, inter-annual variation, and variance. Biases where found to be within 5DU and the RMS errors less than 10 DU. This 17-years dataset has been harmonized into one consistent time series, taking into account the three instruments' difference in ground pixel size. The harmonised dataset is used to determine tropical tropospheric ozone trends and climatological values. The 2015 el Niño event has been characterised as one of the top three strongest el Niños since 1950. El Niño

Quantifying the Impact of Tropospheric Ozone on Crops Productivity at regional scale using JULES-crop

Science.gov (United States)

Leung, F.

2016-12-01

Tropospheric ozone (O3) is the third most important anthropogenic greenhouse gas. It is causing significant crop production losses. Currently, O3 concentrations are projected to increase globally, which could have a significant impact on food security. The Joint UK Land Environment Simulator modified to include crops (JULES-crop) is used here to quantify the impacts of tropospheric O3 on crop production at the regional scale until 2100. We evaluate JULES-crop against the Soybean Free-Air-Concentration-Enrichment (SoyFACE) experiment in Illinois, USA. Experimental data from SoyFACE and various literature sources is used to calibrate the parameters for soybean and ozone damage parameters in soybean in JULES-crop. The calibrated model is then applied for a transient factorial set of JULES-crop simulations over 1960-2005. Simulated yield changes are attributed to individual environmental drivers, CO2, O3 and climate change, across regions and for different crops. A mixed scenario of RCP 2.6 and RCP 8.5 climatology and ozone are simulated to explore the implication of policy. The overall findings are that regions with high ozone concentration such as China and India suffer the most from ozone damage, soybean is more sensitive to O3 than other crops. JULES-crop predicts CO2 fertilisation would increase the productivity of vegetation. This effect, however, is masked by the negative impacts of tropospheric O3. Using data from FAO and JULES-crop estimated that ozone damage cost around 55.4 Billion USD per year on soybean. Irrigation improves the simulation of rice only, and it increases the relative ozone damage because drought can reduce the ozone from entering the plant stomata. RCP 8.5 scenario results in a high yield for all crops mainly due to the CO2 fertilisation effect. Mixed climate scenarios simulations suggest that RCP 8.5 CO2 concentration and RCP 2.6 O3 concentration result in the highest yield. Further works such as more crop FACE-O3 experiments and more Crop

Ground-level O3 pollution and its impacts on food crops in China: A review

International Nuclear Information System (INIS)

Feng, Zhaozhong; Hu, Enzhu; Wang, Xiaoke; Jiang, Lijun; Liu, Xuejun

2015-01-01

Ground-level ozone (O 3 ) pollution has become one of the top environmental issues in China, especially in those economically vibrant and densely populated regions. In this paper, we reviewed studies on the O 3 concentration observation and O 3 effects on food crops throughout China. Data from 118 O 3 monitoring sites reported in the literature show that the variability of O 3 concentration is a function of geographic location. The impacts of O 3 on food crops (wheat and rice) were studied at five sites, equipped with Open Top Chamber or O 3 -FACE (free-air O 3 concentration enrichment) system. Based on exposure concentration and stomatal O 3 flux–response relationships obtained from the O 3 -FACE experimental results in China, we found that throughout China current and future O 3 levels induce wheat yield loss by 6.4–14.9% and 14.8–23.0% respectively. Some policies to reduce ozone pollution and impacts are suggested. - Highlights: • Ozone concentrations are increasing in most of regions of China. • Ozone has caused high yield loss of food crops in China. • More species and local varieties should be investigated for ozone sensitivity. • Developing the air quality standards for crops is required in China. • More air quality stations in the rural are needed. - Ground-level ozone is one of the most serious environmental pollutants for food production in China

Optimization of Catalytic Ozonation Process for Formaldehyde Mineralization from Synthetic Wastewater by Fe/MgO Nanoparticles Synthesis by Sol-Gel Method by Response Surface Model

Directory of Open Access Journals (Sweden)

Ghorban Asgari

2014-09-01

Full Text Available Background: Design experiment stages of formalin mineralization process by center composition design (CCD cause ease of work, reducing the number of samples, increasing the accuracy of optimized conditions and the interaction parameters determined during the process. The aim of this study was optimization of catalytic ozonation process for formaldehyde mineralization from synthetic wastewater by Fe/MgO nanoparticles synthesis by sol-gel method by response surface model. Methods: This experimental study was conducted in a semi-batch reactor, using a RSM by taking 3 factors in the final stage of pH (7-9, reaction time (10-20 min and catalyst dose (1.1-1.3 g/L was investigated. Synthesis of nanoparticles was done by sol-gel method. The results were analyzed by Design Expert 7.0.1 software. Results: The results showed that the process was dependent on the parameters studied and changing each parameter, affected the process efficiency and other parameters. The optimum conditions predicted for the process was 86.51% of mineralization efficiency. Optimum condition included pH=8.82, reaction time of 20 minute and catalyst dose of 1.3 g/L. The correlation coefficient for the process was determined 0.91. Conclusion: Using a statistical model could reduce the number of experiments, the accuracy and the prediction process. The catalytic ozonation process has the ability to remove formaldehyde with high efficiency and the process was environmental friendly.

Theoretical study of ZnO adsorption and bonding on Al2O3 (0001) surface

Institute of Scientific and Technical Information of China (English)

LI Yanrong; YANG Chun; XUE Weidong; LI Jinshan; LIU Yonghua

2004-01-01

ZnO adsorption on sapphire (0001) surface is theoretically calculated by using a plane wave ultrasoft pseudo-potential method based on ab initio molecular dynamics. The results reveal that the surface relaxation in the first layer Al-O is reduced, even eliminated after the surface adsorption of ZnO, and the chemical bonding energy is 434.3(±38.6) kJ·mol-1. The chemical bond of ZnO (0.185 ± 0.01 nm) has a 30° angle away from the adjacent Al-O bond, and the stable chemical adsorption position of the Zn is deflected from the surface O-hexagonal symmetry with an angle of about 30°. The analysis of the atomic populations, density of state and bonding electronic density before and after the adsorption indicates that the chemical bond formed by the O2- of the ZnO and the surface Al3+ has a strong ionic bonding characteristic, while the chemical bond formed by the Zn2+ and the surface O2- has an obvious covalent characteristic, which comes mainly from the hybridization of the Zn 4s and the O 2p and partially from that of the Zn 3d and the O 2p.

Achieving accurate simulations of urban impacts on ozone at high resolution

International Nuclear Information System (INIS)

Li, J; Georgescu, M; Mahalov, A; Moustaoui, M; Hyde, P

2014-01-01

The effects of urbanization on ozone levels have been widely investigated over cities primarily located in temperate and/or humid regions. In this study, nested WRF-Chem simulations with a finest grid resolution of 1 km are conducted to investigate ozone concentrations [O 3 ] due to urbanization within cities in arid/semi-arid environments. First, a method based on a shape preserving Monotonic Cubic Interpolation (MCI) is developed and used to downscale anthropogenic emissions from the 4 km resolution 2005 National Emissions Inventory (NEI05) to the finest model resolution of 1 km. Using the rapidly expanding Phoenix metropolitan region as the area of focus, we demonstrate the proposed MCI method achieves ozone simulation results with appreciably improved correspondence to observations relative to the default interpolation method of the WRF-Chem system. Next, two additional sets of experiments are conducted, with the recommended MCI approach, to examine impacts of urbanization on ozone production: (1) the urban land cover is included (i.e., urbanization experiments) and, (2) the urban land cover is replaced with the region’s native shrubland. Impacts due to the presence of the built environment on [O 3 ] are highly heterogeneous across the metropolitan area. Increased near surface [O 3 ] due to urbanization of 10–20 ppb is predominantly a nighttime phenomenon while simulated impacts during daytime are negligible. Urbanization narrows the daily [O 3 ] range (by virtue of increasing nighttime minima), an impact largely due to the region’s urban heat island. Our results demonstrate the importance of the MCI method for accurate representation of the diurnal profile of ozone, and highlight its utility for high-resolution air quality simulations for urban areas. (letter)

Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

Science.gov (United States)

Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

2015-04-01

We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. © 2014 John Wiley & Sons Ltd.

Removal of APIs and bacteria from hospital wastewater by MBR plus O(3), O(3) + H(2)O(2), PAC or ClO(2).

Science.gov (United States)

Nielsen, U; Hastrup, C; Klausen, M M; Pedersen, B M; Kristensen, G H; Jansen, J L C; Bak, S N; Tuerk, J

2013-01-01

The objective of this study has been to develop technologies that can reduce the content of active pharmaceutical ingredients (APIs) and bacteria from hospital wastewater. The results from the laboratory- and pilot-scale testings showed that efficient removal of the vast majority of APIs could be achieved by a membrane bioreactor (MBR) followed by ozone, ozone + hydrogen peroxide or powdered activated carbon (PAC). Chlorine dioxide (ClO(2)) was significantly less effective. MBR + PAC (450 mg/l) was the most efficient technology, while the most cost-efficient technology was MBR + ozone (156 mg O(3)/l applied over 20 min). With MBR an efficient removal of Escherichia coli and enterococci was measured, and no antibiotic resistant bacteria were detected in the effluent. With MBR + ozone and MBR + PAC also the measured effluent concentrations of APIs (e.g. ciprofloxacin, sulfamethoxazole and sulfamethizole) were below available predicted no-effect concentrations (PNEC) for the marine environment without dilution. Iodinated contrast media were also reduced significantly (80-99% for iohexol, iopromide and ioversol and 40-99% for amidotrizoateacid). A full-scale MBR treatment plant with ozone at a hospital with 900 beds is estimated to require an investment cost of €1.6 mill. and an operating cost of €1/m(3) of treated water.

Efficient catalytic ozonation by ruthenium nanoparticles supported on SiO2 or TiO2: Towards the use of a non-woven fiber paper as original support

KAUST Repository

Biard, Pierre-François

2015-12-24

This work focuses on the use of Ru(0) nanoparticles as heterogeneous catalyst for ozone decomposition and radical production. In a first set of experiments, the nanoparticles have been deposited on two inorganic supports (TiO2 or SiO2) by a wet impregnation approach. This study confirmed the high potential of Ru nanoparticles as active species for ozone decomposition at pH 3, since the ozone half-life time decreases by a factor 20-25, compared to the reference experiment carried out without any catalyst. The enhancement of the ozone decomposition kinetics provided an improved radical production and a higher transient radical concentration in a shorten ozone exposure. Consequently, lower oxidant dosage and contact time would be necessary. Thus, very significant atrazine consumption kinetics enhancements were measured. In a second set of experiments, a non-woven fiber paper composed of a TiO2/SiO2/zeolite mixture has been evaluated as an original support for ruthenium nanoparticles. Even if lower ozone decomposition kinetics was observed compared to TiO2 or SiO2, this support would be a promising alternative to inorganic powders to avoid the catalyst recovery step and to design reactors such as tubular reactors. A new numerical procedure is presented for the evaluation of the transient HO° concentration and of the Rct.

What-ifs for a Northern ozone hole

Energy Technology Data Exchange (ETDEWEB)

Newman, A.

1993-08-01

Based on papers presented at a recent American Geophysical Union meeting in Baltimore, this article discusses various processes that could lead to further significant stratospheric ozone losses over northern latitudes. In southern high latitudes, ClO, formed when Cl atoms react with O[sub 3], persists into the spring and enters a photocatalytic cycle that regenerates ozone-destroying Cl atoms. Type II polar stratospheric clouds (PSCs) are believed to act as catalysts in this cycle. Although type II PSCs rarely form in the warmer Arctic stratosphere, it is possible that type I PSCs and sulfuric acid droplets may act as catalytic surfaces in this region. The arctic however, currently lacks a pronounced ozone hole, unlike Antartica. This is because in the Northern Hemisphere, large-scale tropospheric weather disturbances leak a portion of their energy to the less dense stratosphere. This indirectly leads to the descent of air over the Arctic region which produces compression heating of the polar cap and keeps the Arctic winter stratosphere warm enough to evade the cold temperatures that would produce widespread PSCs, and the associated significant ozone destruction. However, the greenhouse effect could lead to a cooler stratosphere containing more water and weaker tropospheric large-scale disturbances meaning colder Arctic winters. All these factors would contribute to greater PSC formation and the associated ozone destruction.

What-ifs for a Northern ozone hole

International Nuclear Information System (INIS)

Newman, A.

1993-01-01

Based on papers presented at a recent American Geophysical Union meeting in Baltimore, this article discusses various processes that could lead to further significant stratospheric ozone losses over northern latitudes. In southern high latitudes, ClO, formed when Cl atoms react with O 3 , persists into the spring and enters a photocatalytic cycle that regenerates ozone-destroying Cl atoms. Type II polar stratospheric clouds (PSCs) are believed to act as catalysts in this cycle. Although type II PSCs rarely form in the warmer Arctic stratosphere, it is possible that type I PSCs and sulfuric acid droplets may act as catalytic surfaces in this region. The arctic however, currently lacks a pronounced ozone hole, unlike Antartica. This is because in the Northern Hemisphere, large-scale tropospheric weather disturbances leak a portion of their energy to the less dense stratosphere. This indirectly leads to the descent of air over the Arctic region which produces compression heating of the polar cap and keeps the Arctic winter stratosphere warm enough to evade the cold temperatures that would produce widespread PSCs, and the associated significant ozone destruction. However, the greenhouse effect could lead to a cooler stratosphere containing more water and weaker tropospheric large-scale disturbances meaning colder Arctic winters. All these factors would contribute to greater PSC formation and the associated ozone destruction

Formaldehyde Column Density Measurements as a Suitable Pathway to Estimate Near-Surface Ozone Tendencies from Space

Science.gov (United States)

Schroeder, Jason R.; Crawford, James H.; Fried, Alan; Walega, James; Weinheimer, Andrew; Wisthaler, Armin; Mueller, Markus; Mikoviny, Tomas; Chen, Gao; Shook, Michael;

Surface reaction rate and probability of ozone and alpha-terpineol on glass, polyvinyl chloride, and latex paint surfaces.

Science.gov (United States)

Shu, Shi; Morrison, Glenn C

2011-05-15

Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

Understanding and improving global crop response to ozone pollution

Science.gov (United States)

Concentrations of ground-level ozone ([O3]) over much of the Earth’s land surface have more than doubled since pre-industrial times. The air pollutant is highly variable over time and space, which makes it difficult to assess the average agronomic and economic impacts of the pollutant as well as to ...

Ozone Oxidation of Self-Assembled Monolayers on SiOx-Coated Zinc Selenide Surfaces

Science.gov (United States)

McIntire, T. M.; Ryder, O. S.; Finlayson-Pitts, B. J.

2008-12-01

Airborne particles are important for visibility, human health, climate, and atmospheric reactions. Atmospheric particles contain a significant fraction of organics and such compounds present on airborne particles are susceptible to oxidation by atmospheric oxidants, such as OH, ozone, halogen atoms, and nitrogen trioxide. Oxidized organics associated with airborne particles are thought to be polar, hygroscopic species with enhanced cloud-nucleating properties. Oxide layers on silicon, or SiO2-coated substrates, act as models of environmentally relevant surfaces such as dust particles upon which organics adsorb. We have shown previously that ozone oxidation of unsaturated self-assembled monolayers (SAMs) on silicon attenuated total reflectance (ATR) crystals leads to the formation of carbonyl groups and micron-sized, hydrophobic organic aggregates surrounded by carbon depleted substrate that do not have increased water uptake as previously assumed. Reported here are further ATR-FTIR studies of the oxidation of alkene SAMs on ZnSe and SiO2-coated ZnSe. These substrates have the advantage that they transmit below 1500 cm-1, allowing detection of additional product species. These experiments show that the loss of C=C and formation of carbonyl groups is also accompanied by formation of a peak at 1110 cm-1, attributed to the secondary ozonide. Details concerning the products and mechanism of ozonolysis of alkene SAMs on surfaces based on these new data are presented and the implications for the oxidation of alkenes on airborne dust particles are discussed.

Study of the solid-solid surface adsorption of Eu2O3 on various Al2O3 supports

International Nuclear Information System (INIS)

Liu Rongchuan; Yu Zhi; Zhou Yuan; Yoshitake Yamazaki

1997-12-01

Solid-solid surface interactions of Eu 2 O 3 on various oxide substrates are investigated with X-ray and Moessbauer experiments. The results indicate that the interaction of Eu 2 O 3 on the complex support differs from that having simple support. An incorporation model is used to explain how Eu 2 O 3 disperses onto the surface of γ-alumina or η-alumina

Model of daytime emissions of electronically-vibrationally excited products of O3 and O2 photolysis: application to ozone retrieval

Directory of Open Access Journals (Sweden)

V. A. Yankovsky

2006-11-01

Full Text Available The traditional kinetics of electronically excited products of O3 and O2 photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O2(a1Δg, v and O2(b1Σ+g, v, excited atomic oxygen O(1D, and the O2 molecules in the ground electronic state O2(X3Σg−, v. In contrast to the previous models of kinetics of O2(a1Δg and O2 (b1Σ+g, our model takes into consideration the following basic facts: first, photolysis of O3 and O2 and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b1Σ+g, a1Δg and X3Σg−; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O2(b1Σ+g, v=0 (at 762 nm and O2(a1Δg, v=0 (at 1.27 µm, but also leads to populating the excited electronic–vibrational states O2(b1Σ+g, v=1 and O2(b1Σ+g, v=2 (at 689 nm and 629 nm. The proposed model allows one to calculate not only the vertical profiles of the O2(a1Δg, v=0 and O2(b1Σg, v=0 concentrations, but also the profiles of [O2(a1Δg, v≤5], [O2 (b1Σ+g , v=1, 2] and O2(X3Σg−, v=1–35. In the altitude range 60–125 km, consideration of the electronic-vibrational kinetics significantly changes the calculated concentrations of the metastable oxygen molecules and reduces the discrepancy between the altitude profiles of ozone concentrations retrieved from the 762-nm and 1.27-µm emissions measured simultaneously.

Changes in the surface ozone after the windstorm in 2004, in the High Tatras

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Bičárová Svetlana

2015-06-01

Full Text Available Extreme wind event in November 2004 caused spacious destruction of slope forests in the Tatra National Park, Slovakia. Relevant changes of land cover motivated researchers to investigate damaged forest ecosystem and its response to different environmental conditions. Surface ozone (O3 is a minor but not negligible compound of the ambient air. Control strategies for the reduction of O3 precursor emissions have been applied in Europe during the last two decades. In spite of these reductions, air quality indices for O3 suggest that highland sites are more vulnerable to health and environmental risk than lowlands where mostly emissions from road transport and industry are produced. Both anthropogenic sources and biogenic precursors (BVOC from forest vegetation play a relevant role in the tropospheric photochemistry, especially at mountainous and rural locations. The parameters of air quality are measured at background station Stará Lesná in the High Tatras region since 1992 in frame of an European project EMEP. Long-term data series (1992-2013 of O3 concentrations obtained for site Stará Lesná provide specific opportunity to investigate the response of BVOC reduction on O3 variability after windstorm 2004. Evaluation of these data indicates moderate increase of annual, monthly and hourly O3 means for the period from 2005 to 2013 in comparison with the previous period 1992-2004. Temporal interpolation shows evident changes of O3 concentrations, especially ~30% increase for night hours in spring season and on the contrary ~15% decrease for daylight afternoon hours in summer season. Statistically significant changes were identified for spring months (April and May, 0-6 hours and summer months (July, 12-20 hours. Increasing O3 values in the night may be associated with the absence of BVOC for ozonolysis reaction that is one of the mechanism for O3 depletion. On the other hand, the decline of daylight O3 values in summer suggests lower O3 production

LANDFILL LEACHATES PRETREATMENT BY OZONATION

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Jacek Leszczyński

2016-06-01

Full Text Available In this paper, the application of ozonation processes for stabilized landfill leachate treatment was investigated. The leachate came from a municipal sanitary landfill located nearby Bielsk Podlaski. The average values of its main parameters were: pH 8.23; COD 870 mgO2/dm3; BOD 90 mgO2/dm3; NH4+ 136.2 mgN/dm3; UV254 absorbance 0.312 and turbidity 14 NTU. The ozone dosages used were in the range of 115.5 to 808.5 mgO3/dm3 of the leachate. The maximum COD, color and UV254 absorbance removal wa.5 mgO3/dm3. After oxidation, the ratio of BOD/COD was increased from 0.1 up to 0.23.

O2(a1Δ) Quenching In The O/O2/O3 System

Science.gov (United States)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-10-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ)+O+M→2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ) quenching were followed by observing the 1268 nm fluorescence of the O2a1Δ-X3∑ transition. Fast quenching of O2(a1Δ) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

O2(a1Δ) Quenching In The O/O2/O3 System

International Nuclear Information System (INIS)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-01-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O 2 (a 1 Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O 2 (a 1 Δ)+O+M→2O 2 +M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O 2 (a 1 Δ) in O( 3 P)/O 2 /O 3 /CO 2 /He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O 2 (a 1 Δ) quenching were followed by observing the 1268 nm fluorescence of the O 2 a 1 Δ-X 3 Σ transition. Fast quenching of O 2 (a 1 Δ) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

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X. Yin

2017-09-01

Full Text Available Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of  ∼ 5 years (January 2011 to October 2015, which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau

Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

Science.gov (United States)

Yin, Xiufeng; Kang, Shichang; de Foy, Benjamin; Cong, Zhiyuan; Luo, Jiali; Zhang, Lang; Ma, Yaoming; Zhang, Guoshuai; Rupakheti, Dipesh; Zhang, Qianggong

2017-09-01

Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of ˜ 5 years (January 2011 to October 2015), which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation) was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau. This work may provide a

Improved tooth bleaching combining ozone and hydrogen peroxide--A blinded study.

Science.gov (United States)

Al-Omiri, Mahmoud K; Abul Hassan, Ra'ed S; AlZarea, Bader K; Lynch, Edward

2016-03-01

To evaluate the efficacy of tooth bleaching using ozone after hydrogen peroxide (H2O2) in comparison to the use of H2O2 alone. 70 extracted teeth were randomly distributed into two groups. Teeth surfaces in group 1 (n=35) were treated using 38% H2O2 and then were exposed to ozone for 60s and this ozonated peroxide mixture was left on the teeth for 20 min. Meanwhile, teeth in group 2 (n=35) were treated with H2O2 38% for 20 min. The L* a* b* and Vita Classic shade values of teeth were evaluated in both groups at base line, after application of H2O2 and ozone in group 1, and after application of H2O2 and then again after another application of ozone in group 2. The statistically significant changes were set at P ≤ 0.05. Baseline L* a* b* and Vita shade values were comparable between groups (P>0.05). Teeth obtained lighter shades following bleaching with both H2O2 and ozone or with H2O2 alone (P ≤ 0.05). Further bleaching with ozone for teeth already bleached with H2O2 alone showed further improvement of the shades of teeth (Pbleaching in both groups (P ≤ 0.05). More changes were obtained when both ozone and H2O2 were used (P ≤ 0.05). Bleaching with 38% H2O2 and ozone resulted in teeth with lighter shades than bleaching with 38% H2O2 alone. Copyright © 2016 Elsevier Ltd. All rights reserved.

Global impacts of surface ozone changes on crop yields and land use

NARCIS (Netherlands)

Chuwah, C.D.; Noije, van Twan; Vuuren, van Detlef P.; Stehfest, Elke; Hazeleger, Wilco

2015-01-01

Exposure to surface ozone has detrimental impacts on vegetation and crop yields. In this study, we estimate ozone impacts on crop production and subsequent impacts on land use in the 2005-2050 period using results of the TM5 atmospheric chemistry and IMAGE integrated assessment model. For the

Global impacts of surface ozone changes on crop yields and land use

NARCIS (Netherlands)

Chuwah, Clifford; van Noije, Twan; van Vuuren, Detlef P.; Stehfest, Elke; Hazeleger, Wilco

2015-01-01

Exposure to surface ozone has detrimental impacts on vegetation and crop yields. In this study, we estimate ozone impacts on crop production and subsequent impacts on land use in the 2005-2050 period using results of the TM5 atmospheric chemistry and IMAGE integrated assessment model. For the crops

Comparison Between Dielectric Barrier Discharge Plasma and Ozone Regenerations of Activated Carbon Exhausted with Pentachlorophenol

Science.gov (United States)

Qu, Guangzhou; Liang, Dongli; Qu, Dong; Huang, Yimei; Li, Jie

2014-06-01

In this study, two regeneration methods (dielectric barrier discharge (DBD) plasma and ozone (O3) regeneration) of saturated granular activated carbon (GAC) with pentachlorophenol (PCP) were compared. The results show that the two regeneration methods can eliminate contaminants from GAC and recover its adsorption properties to some extent. Comparing the DBD plasma with O3 regeneration, the adsorption rate and the capacity of the GAC samples after DBD plasma regeneration are greater than those after O3 regeneration. O3 regeneration decreases the specific surface area of GAC and increases the acidic surface oxygen groups on the surface of GAC, which causes a decrease in PCP on GAC uptake. With increasing regeneration cycles, the regeneration efficiencies of the two methods decrease, but the decrease in the regeneration efficiencies of GAC after O3 regeneration is very obvious compared with that after DBD plasma regeneration. Furthermore, the equilibrium data were fitted by the Freundlich and Langmuir models using the non-linear regression technique, and all the adsorption equilibrium isotherms fit the Langmuir model fairly well, which demonstrates that the DBD plasma and ozone regeneration processes do not appear to modify the adsorption process, but to shift the equilibrium towards lower adsorption concentrations. Analyses of the weight loss of GAC show that O3 regeneration has a lower weight loss than DBD plasma regeneration.

Comparison Between Dielectric Barrier Discharge Plasma and Ozone Regenerations of Activated Carbon Exhausted with Pentachlorophenol

International Nuclear Information System (INIS)

Qu Guangzhou; Liang Dongli; Qu Dong; Huang Yimei; Li Jie

2014-01-01

In this study, two regeneration methods (dielectric barrier discharge (DBD) plasma and ozone (O 3 ) regeneration) of saturated granular activated carbon (GAC) with pentachlorophenol (PCP) were compared. The results show that the two regeneration methods can eliminate contaminants from GAC and recover its adsorption properties to some extent. Comparing the DBD plasma with O 3 regeneration, the adsorption rate and the capacity of the GAC samples after DBD plasma regeneration are greater than those after O 3 regeneration. O 3 regeneration decreases the specific surface area of GAC and increases the acidic surface oxygen groups on the surface of GAC, which causes a decrease in PCP on GAC uptake. With increasing regeneration cycles, the regeneration efficiencies of the two methods decrease, but the decrease in the regeneration efficiencies of GAC after O 3 regeneration is very obvious compared with that after DBD plasma regeneration. Furthermore, the equilibrium data were fitted by the Freundlich and Langmuir models using the non-linear regression technique, and all the adsorption equilibrium isotherms fit the Langmuir model fairly well, which demonstrates that the DBD plasma and ozone regeneration processes do not appear to modify the adsorption process, but to shift the equilibrium towards lower adsorption concentrations. Analyses of the weight loss of GAC show that O 3 regeneration has a lower weight loss than DBD plasma regeneration

Ozone Induced Premature Mortality and Crop Yield Loss in China

Science.gov (United States)

Lin, Y.; Jiang, F.; Wang, H.

2017-12-01

Exposure to ambient ozone is a major risk factor for health impacts such as chronic obstructive pulmonary disease (COPD) and cause damage to plant and agricultural crops. But these impacts were usually evaluated separately in earlier studies. We apply Community Multi-scale Air Quality model to simulate the ambient O3 concentration at a resolution of 36 km×36 km across China. Then, we follow Global Burden of Diseases approach and AOT40 (i.e., above a threshold of 40 ppb) metric to estimate the premature mortalities and yield losses of major grain crops (i.e., winter wheat, rice and corn) across China due to surface ozone exposure, respectively. Our results show that ozone exposure leads to nearly 67,700 premature mortalities and 145 billion USD losses in 2014. The ozone induced yield losses of all crop production totaled 78 (49.9-112.6)million metric tons, worth 5.3 (3.4-7.6)billion USD, in China. The relative yield losses ranged from 8.5-14% for winter wheat, 3.9-15% for rice, and 2.2-5.5% for maize. We can see that the top four health affected provinces (Sichuan, Henan, Shandong, Jiangsu) are also ranking on the winter wheat and rice crop yield loss. Our results provide further evidence that surface ozone pollution is becoming urgent air pollution in China, and have important policy implications for China to alleviate the impacts of air pollution.

[Mechanism and performance of styrene oxidation by O3/H2O2].

Science.gov (United States)

He, Jue-Cong; Huang, Qian-Ru; Ye, Qi-Hong; Luo, Yu-Wei; Zhang, Zai-Li; Fan, Qing-Juan; Wei, Zai-Shan

2013-10-01

It can produce a large number of free radicals in O3/H2O2, system, ozone and free radical coupling oxidation can improve the styrene removal efficiency. Styrene oxidation by O3/H2O2 was investigated. Ozone dosage, residence time, H2o2 volume fraction, spray density and molar ratio of O3/C8H8 on styrene removal were evaluated. The experimental results showed that styrene removal efficiency achieved 85.7%. The optimal residence time, H2O2, volume fraction, spray density and O3/C8H8 molar ratio were 20. 6 s, 10% , 1.72 m3.(m2.h)-1 and 0.46, respectively. The gas-phase degradation intermediate products were benzaldehyde(C6H5CHO) and benzoic acid (C6H5 COOH) , which were identified by means of gas chromatography-mass spectrometry(GC-MS). The degradation mechanism of styrene is presented.

Ozone generation in a kHz-pulsed He-O2 capillary dielectric barrier discharge operated in ambient air

Science.gov (United States)

Sands, Brian L.; Ganguly, Biswa N.

2013-12-01

The generation of reactive oxygen species using nonequilibrium atmospheric pressure plasma jet devices has been a subject of recent interest due to their ability to generate localized concentrations from a compact source. To date, such studies with plasma jet devices have primarily utilized radio-frequency excitation. In this work, we characterize ozone generation in a kHz-pulsed capillary dielectric barrier discharge configuration comprised of an active discharge plasma jet operating in ambient air that is externally grounded. The plasma jet flow gas was composed of helium with an admixture of up to 5% oxygen. A unipolar voltage pulse train with a 20 ns pulse risetime was used to drive the discharge at repetition rates between 2-25 kHz. Using UVLED absorption spectroscopy centered at 255 nm near the Hartley-band absorption peak, ozone was detected over 1 cm from the capillary axis. We observed roughly linear scaling of ozone production with increasing pulse repetition rate up to a "turnover frequency," beyond which ozone production steadily dropped and discharge current and 777 nm O(5P→5S°) emission sharply increased. The turnover in ozone production occurred at higher pulse frequencies with increasing flow rate and decreasing applied voltage with a common energy density of 55 mJ/cm3 supplied to the discharge. The limiting energy density and peak ozone production both increased with increasing O2 admixture. The power dissipated in the discharge was obtained from circuit current and voltage measurements using a modified parallel plate dielectric barrier discharge circuit model and the volume-averaged ozone concentration was derived from a 2D ozone absorption measurement. From these measurements, the volume-averaged efficiency of ozone production was calculated to be 23 g/kWh at conditions for peak ozone production of 41 mg/h at 11 kV applied voltage, 3% O2, 2 l/min flow rate, and 13 kHz pulse repetition rate, with 1.79 W dissipated in the discharge.

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

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L. Marelle

2017-10-01

Full Text Available In this study, the WRF-Chem regional model is updated to improve simulated short-lived pollutants (e.g., aerosols, ozone in the Arctic. Specifically, we include in WRF-Chem 3.5.1 (with SAPRC-99 gas-phase chemistry and MOSAIC aerosols (1 a correction to the sedimentation of aerosols, (2 dimethyl sulfide (DMS oceanic emissions and gas-phase chemistry, (3 an improved representation of the dry deposition of trace gases over seasonal snow, and (4 an UV-albedo dependence on snow and ice cover for photolysis calculations. We also (5 correct the representation of surface temperatures over melting ice in the Noah Land Surface Model and (6 couple and further test the recent KF-CuP (Kain–Fritsch + Cumulus Potential cumulus parameterization that includes the effect of cumulus clouds on aerosols and trace gases. The updated model is used to perform quasi-hemispheric simulations of aerosols and ozone, which are evaluated against surface measurements of black carbon (BC, sulfate, and ozone as well as airborne measurements of BC in the Arctic. The updated model shows significant improvements in terms of seasonal aerosol cycles at the surface and root mean square errors (RMSEs for surface ozone, aerosols, and BC aloft, compared to the base version of the model and to previous large-scale evaluations of WRF-Chem in the Arctic. These improvements are mostly due to the inclusion of cumulus effects on aerosols and trace gases in KF-CuP (improved RMSE for surface BC and BC profiles, surface sulfate, and surface ozone, the improved surface temperatures over sea ice (surface ozone, BC, and sulfate, and the updated trace gas deposition and UV albedo over snow and ice (improved RMSE and correlation for surface ozone. DMS emissions and chemistry improve surface sulfate at all Arctic sites except Zeppelin, and correcting aerosol sedimentation has little influence on aerosols except in the upper troposphere.

Oxygen isotope dynamics of atmospheric nitrate over the Antarctic plateau: First combined measurements of ozone and nitrate 17O-excess (Δ17O)

Science.gov (United States)

Vicars, William; Savarino, Joël; Erbland, Joseph; Preunkert, Susanne; Jourdain, Bruno; Frey, Markus; Gil, Jaime; Legrand, Michel

2013-04-01

Variations in the isotopic composition of atmospheric nitrate (NO3-) provide novel indicators for important processes in boundary layer chemistry, often acting as source markers for reactive nitrogen (NOx = NO + NO2) and providing both qualitative and quantitative constraints on the pathways that determine its fate. Stable isotope ratios of nitrate (δ15N, δ17O, δ18O) offer direct insight into the nature and magnitude of the fluxes associated with different processes, thus providing unique information regarding phenomena that are often difficult to quantify from concentration measurements alone. The unique and distinctive 17O-excess (Δ17O = δ17O - 0.52 × δ18O ) of ozone (O3), which is transferred to NOx via oxidation reactions in the atmosphere, has been found to be a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O-excess within the NOx cycle is critical in polar areas where there exists the possibility of extending atmospheric interpretations to the glacial/interglacial time scale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C, Antarctica during December 2011 to January 2012. Sampling was conducted within the framework of the OPALE (Oxidant Production over Antarctic Land and its Export) project, thus providing an opportunity to combine our isotopic observations with a wealth of meteorological and chemical data, including in-situ concentration measurements of the gas-phase precursors involved in nitrate production (NOx, O3, OH, HO2, etc.). Furthermore, nitrate isotope analysis has been combined in this study for the first time with parallel observations of the transferrable Δ17O of surface ozone, which was measured concurrently at Dome C using our recently developed analytical approach. This unique dataset has allowed for a direct comparison of observed Δ17O(NO3-) values to those that are

Stratospheric ozone: History and concepts and interactions with climate

Directory of Open Access Journals (Sweden)

Bekki S.

2009-02-01

Full Text Available Although in relatively low concentration of a few molecules per million of e e air molecules, atmospheric ozone (trioxygen O3 is essential to sustaining life on the surface of the Earth. Indeed, by absorbing solar radiation between 240 and 320 nm, it shields living organisms including humans from the very harmful ultraviolet radiation UV-B. About 90% of the ozone resides in the stratosphere, a region that extends from the tropopause, whose altitude ranges from 7 km at the poles to 17 km in the tropics, to the stratopause located at about 50 km altitude. Stratospheric ozone is communally referred as the « ozone layer ». Unlike the atmosphere surrounding it, the stratosphere is vertically stratified and stable because the temperature increases with height within it. This particularity originates from heating produced by the absorption of UV radiation by stratospheric ozone. The present chapter describes the main mechanisms that govern the natural balance of ozone in the stratosphere, and its disruption under the influence of human activities.

Impacts of aerosol direct effects on tropospheric ozone through changes in atmospheric dynamics and photolysis rates

Science.gov (United States)

Xing, Jia; Wang, Jiandong; Mathur, Rohit; Wang, Shuxiao; Sarwar, Golam; Pleim, Jonathan; Hogrefe, Christian; Zhang, Yuqiang; Jiang, Jingkun; Wong, David C.; Hao, Jiming

2017-08-01

Aerosol direct effects (ADEs), i.e., scattering and absorption of incoming solar radiation, reduce radiation reaching the ground and the resultant photolysis attenuation can decrease ozone (O3) formation in polluted areas. One the other hand, evidence also suggests that ADE-associated cooling suppresses atmospheric ventilation, thereby enhancing surface-level O3. Assessment of ADE impacts is thus important for understanding emission reduction strategies that seek co-benefits associated with reductions in both particulate matter and O3 levels. This study quantifies the impacts of ADEs on tropospheric ozone by using a two-way online coupled meteorology and atmospheric chemistry model, WRF-CMAQ, using a process analysis methodology. Two manifestations of ADE impacts on O3 including changes in atmospheric dynamics (ΔDynamics) and changes in photolysis rates (ΔPhotolysis) were assessed separately through multiple scenario simulations for January and July of 2013 over China. Results suggest that ADEs reduced surface daily maxima 1 h O3 (DM1O3) in China by up to 39 µg m-3 through the combination of ΔDynamics and ΔPhotolysis in January but enhanced surface DM1O3 by up to 4 µg m-3 in July. Increased O3 in July is largely attributed to ΔDynamics, which causes a weaker O3 sink of dry deposition and a stronger O3 source of photochemistry due to the stabilization of the atmosphere. Meanwhile, surface OH is also enhanced at noon in July, though its daytime average values are reduced in January. An increased OH chain length and a shift towards more volatile organic compound (VOC)-limited conditions are found due to ADEs in both January and July. This study suggests that reducing ADEs may have the potential risk of increasing O3 in winter, but it will benefit the reduction in maxima O3 in summer.

Exposure-Relevant Ozone Chemistry in Occupied Spaces

Energy Technology Data Exchange (ETDEWEB)

Coleman, Beverly Kaye [Univ. of California, Berkeley, CA (United States)

2009-04-01

Ozone, an ambient pollutant, is transformed into other airborne pollutants in the indoor environment. In this dissertation, the type and amount of byproducts that result from ozone reactions with common indoor surfaces, surface residues, and vapors were determined, pollutant concentrations were related to occupant exposure, and frameworks were developed to predict byproduct concentrations under various indoor conditions. In Chapter 2, an analysis is presented of secondary organic aerosol formation from the reaction of ozone with gas-phase, terpene-containing consumer products in small chamber experiments under conditions relevant for residential and commercial buildings. The full particle size distribution was continuously monitored, and ultrafine and fine particle concentrations were in the range of 10 to>300 mu g m^-3. Particle nucleation and growth dynamics were characterized.Chapter 3 presents an investigation of ozone reactions with aircraft cabin surfaces including carpet, seat fabric, plastics, and laundered and worn clothing fabric. Small chamber experiments were used to determine ozone deposition velocities, ozone reaction probabilities, byproduct emission rates, and byproduct yields for each surface category. The most commonly detected byproducts included C1?C10 saturated aldehydes and skin oil oxidation products. For all materials, emission rates were higher with ozone than without. Experimental results were used to predict byproduct exposure in the cabin and compare to other environments. Byproduct levels are predicted to be similar to ozone levels in the cabin, which have been found to be tens to low hundreds of ppb in the absence of an ozone converter. In Chapter 4, a model is presented that predicts ozone uptake by and byproduct emission from residual chemicals on surfaces. The effects of input parameters (residue surface concentration, ozone concentration, reactivity of the residue and the surface, near-surface airflow conditions, and

Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone

Directory of Open Access Journals (Sweden)

B. Sauvage

2007-01-01

Full Text Available We use a global chemical transport model (GEOS-Chem to evaluate the consistency of satellite measurements of lightning flashes and ozone precursors with in situ measurements of tropical tropospheric ozone. The measurements are tropospheric O3, NO2, and HCHO columns from the GOME satellite instrument, lightning flashes from the OTD and LIS satellite instruments, profiles of O3, CO, and relative humidity from the MOZAIC aircraft program, and profiles of O3 from the SHADOZ ozonesonde network. We interpret these multiple data sources with our model to better understand what controls tropical tropospheric ozone. Tropical tropospheric ozone is mainly affected by lightning NOx and convection in the upper troposphere and by surface emissions in the lower troposphere. Scaling the spatial distribution of lightning in the model to the observed flashes improves the simulation of O3 in the upper troposphere by 5–20 ppbv versus in situ observations and by 1–4 Dobson Units versus GOME retrievals of tropospheric O3 columns. A lightning source strength of 6±2 Tg N/yr best represents in situ observations from aircraft and ozonesonde. Tropospheric NO2 and HCHO columns from GOME are applied to provide top-down constraints on emission inventories of NOx (biomass burning and soils and VOCs (biomass burning. The top-down biomass burning inventory is larger than the bottom-up inventory by a factor of 2 for HCHO and alkenes, and by a factor of 2.6 for NOx over northern equatorial Africa. These emissions increase lower tropospheric O3 by 5–20 ppbv, improving the simulation versus aircraft observations, and by 4 Dobson Units versus GOME observations of tropospheric O3 columns. Emission factors in the a posteriori inventory are more consistent with a recent compilation from in situ measurements. The ozone simulation using two different dynamical schemes (GEOS-3 and GEOS-4 is evaluated versus observations; GEOS-4 better represents O3 observations by 5–15 ppbv