Lidar Observations of the Vertical Structure of Ozone and Aerosol during Wintertime High-Ozone Episodes Associated with Oil and Gas Exploration in the Uintah Basin

NASA Astrophysics Data System (ADS)

Senff, C. J.; Langford, A. O.; Banta, R. M.; Alvarez, R. J.; Weickmann, A.; Sandberg, S.; Marchbanks, R. D.; Brewer, A.; Hardesty, R. M.

2013-12-01

The Uintah Basin in northeast Utah has been experiencing extended periods of poor air quality in the winter months including very high levels of surface ozone. To investigate the causes of these wintertime ozone pollution episodes, two comprehensive studies were undertaken in January/February of 2012 and 2013. As part of these Uintah Basin Ozone Studies (UBOS), NOAA deployed its ground-based, scanning Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar to document the vertical structure of ozone and aerosol backscatter from near the surface up to about 3 km above ground level (AGL). TOPAZ, along with a comprehensive set of chemistry and meteorological measurements, was situated in both years at the Horse Pool site at the northern edge of a large concentration of gas producing wells in the eastern part of the Uintah Basin. The 2012 study was characterized by unusually warm and snow-free condition and the TOPAZ lidar observed deep boundary layers (BL) and mostly well-mixed vertical ozone profiles at or slightly above tropospheric background levels. During UBOS 2013, winter weather conditions in the Uintah Basin were more typical with snow-covered ground and a persistent, shallow cold-pool layer. The TOPAZ lidar characterized with great temporal and spatial detail the evolution of multiple high-ozone episodes as well as cleanout events caused by the passage of synoptic-scale storm systems. Despite the snow cover, the TOPAZ observations show well-mixed afternoon ozone and aerosol profiles up to about 100 m AGL. After several days of pollutant buildup, BL ozone values reached 120-150 ppbv. Above the mixed layer, ozone values gradually decreased to tropospheric background values of around 50 ppbv throughout the several-hundred-meter-deep cold-pool layer and then stayed constant above that up to about 3 km AGL. During the ozone episodes, the lidar observations show no indication of either vertical or horizontal transport of high ozone levels to the surface, thus supporting the notion that ozone is locally produced in the Uintah Basin. In both winters, TOPAZ occasionally observed ozone titration as the NOx-rich plume from the nearby Bonanza power plant was advected over the Horse Pool site. In 2012, low ozone values due to titration were observed at the surface and throughout the well-mixed BL, while in 2013 low ozone values were confined to the upper part of the cold-pool layer above the BL. This suggests that power plant NOx was very likely not part of the precursor mix that led to the high surface ozone values observed in 2013.

Impacts of stratospheric sulfate geoengineering on tropospheric ozone

NASA Astrophysics Data System (ADS)

Xia, Lili; Nowack, Peer J.; Tilmes, Simone; Robock, Alan

2017-10-01

A range of solar radiation management (SRM) techniques has been proposed to counter anthropogenic climate change. Here, we examine the potential effects of stratospheric sulfate aerosols and solar insolation reduction on tropospheric ozone and ozone at Earth's surface. Ozone is a key air pollutant, which can produce respiratory diseases and crop damage. Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario. This allows us to compare the impacts of sulfate aerosols and solar dimming on atmospheric ozone concentrations. Despite nearly identical global mean surface temperatures for the two SRM approaches, solar insolation reduction increases global average surface ozone concentrations, while sulfate injection decreases it. A fundamental difference between the two geoengineering schemes is the importance of heterogeneous reactions in the photochemical ozone balance with larger stratospheric sulfate abundance, resulting in increased ozone depletion in mid- and high latitudes. This reduces the net transport of stratospheric ozone into the troposphere and thus is a key driver of the overall decrease in surface ozone. At the same time, the change in stratospheric ozone alters the tropospheric photochemical environment due to enhanced ultraviolet radiation. A shared factor among both SRM scenarios is decreased chemical ozone loss due to reduced tropospheric humidity. Under insolation reduction, this is the dominant factor giving rise to the global surface ozone increase. Regionally, both surface ozone increases and decreases are found for both scenarios; that is, SRM would affect regions of the world differently in terms of air pollution. In conclusion, surface ozone and tropospheric chemistry would likely be affected by SRM, but the overall effect is strongly dependent on the SRM scheme. Due to the health and economic impacts of surface ozone, all these impacts should be taken into account in evaluations of possible consequences of SRM.

Surface ozone variability at Kislovodsk Observatory

NASA Technical Reports Server (NTRS)

Elansky, Nikolay F.; Makarov, Oleg V.; Senik, Irina A.

1994-01-01

The results of the surface ozone observations at the Observatory 'Kislovodsk', situated in the North Caucasus at the altitude 2070 m a.s.l., are given. The observatory is in the background conditions and the variations of the surface ozone are determined by the natural dynamic and photochemical processes. The mean value of the concentration and its seasonal variations are very near to those obtained at the high-mountain stations in Alps. The daily variations have the features, which remain stable during all warm period of the year (April-October). These features, including the minimum of the surface ozone at noon, are formed by the mountain-valley circulation. The significant variations of the surface ozone are connected with the unstationary lee waves.

Tropospheric ozone in the western Pacific Rim: Analysis of satellite and surface-based observations along with comprehensive 3-D model simulations

NASA Technical Reports Server (NTRS)

Young, Sun-Woo; Carmichael, Gregory R.

1994-01-01

Tropospheric ozone production and transport in mid-latitude eastern Asia is studied. Data analysis of surface-based ozone measurements in Japan and satellite-based tropospheric column measurements of the entire western Pacific Rim are combined with results from three-dimensional model simulations to investigate the diurnal, seasonal and long-term variations of ozone in this region. Surface ozone measurements from Japan show distinct seasonal variation with a spring peak and summer minimum. Satellite studies of the entire tropospheric column of ozone show high concentrations in both the spring and summer seasons. Finally, preliminary model simulation studies show good agreement with observed values.

High Concentrations of Ozone Air Pollution on Mount Everest: Health Implications for Sherpa Communities and Mountaineers.

PubMed

Semple, John L; Moore, G W Kent; Koutrakis, Petros; Wolfson, Jack M; Cristofanelli, Paolo; Bonasoni, Paolo

2016-12-01

Semple, John L., G.W. Kent Moore, Petros Koutrakis, Jack M. Wolfson, Paolo Cristofanelli, and Paolo Bonasoni. High concentrations of ozone air pollution on Mount Everest: health implications for Sherpa communities and mountaineers. High Alt Med Biol. 17:365-369, 2016.-Introduction: Populations in remote mountain regions are increasingly vulnerable to multiple climate mechanisms that influence levels of air pollution. Few studies have reported on climate-sensitive health outcomes unique to high altitude ecosystems. In this study, we report on the discovery of high-surface ozone concentrations and the potential impact on health outcomes on Mount Everest and the high Himalaya. Surface ozone measurements were collected during ascending transects in the Mount Everest region of Nepal with passive nitrite-coated Ogawa filter samplers to obtain 8-hour personal exposures (2860-5364 m asl). In addition, the Nepal Climate Observatory-Pyramid, a GAW-WMO Global Station sited in the Khumbu Valley (5079 m asl), collected ozone mixing ratios with photometric gas analyzer. Surface ozone measurements increased with altitude with concentrations that exceed 100 ppb (8-hour exposure). Highest values were during the spring season and the result of diverse contributions: hemispheric background values, the descent of ozone-rich stratospheric air, and the transport of tropospheric pollutants occurring at different spatial scales. Multiple climate factors, including descending stratospheric ozone and imported anthropogenic air masses from the Indo-Gangetic Plain, contribute to ambient ozone exposure levels in the vicinity of Mount Everest that are similar to if not higher than those reported in industrialized cities.

Direct observation of ozone formation on SiO2 surfaces in O2 discharges

NASA Astrophysics Data System (ADS)

Marinov, D.; Guaitella, O.; Booth, J. P.; Rousseau, A.

2013-01-01

Ozone production is studied in a pulsed O2 discharge at pressures in the range 1.3-6.7 mbar. Time-resolved absolute concentrations of O3 and O are measured in the post-discharge using UV absorption spectroscopy and two-photon absorption laser-induced fluorescence. In a bare silica discharge tube ozone is formed mainly by three-body gas-phase recombination. When the tube surface is covered by a high specific surface silica catalyst heterogeneous formation becomes the main source of ozone. The efficiency of this surface process increases with O2 pressure and is favoured by the presence of OH groups and adsorbed H2O on the surface. At p = 6.7 mbar ozone production accounts for up to 25% of the atomic oxygen losses on the surface.

Surface Ozone Measured at GLOBE Schools in the Czech Republic: A Demonstration of the Importance of Student Contribution to the Larger Science Picture

NASA Technical Reports Server (NTRS)

Pippin, Margaret R.; Creilson, John K.; Henderson, Bryana L.; Ladd, Irene H.; Fishman, Jack; Votapkova, Dana; Krpcova, Ilona

2008-01-01

GLOBE (Global Learning and Observations to Benefit the Environment) is a worldwide hands-on, primary and secondary school-based education and science program, developed to give students a chance to perform real science by making measurements, analyzing data, and participating in research in collaboration with scientists. As part of the GLOBE Surface Ozone Protocol and with the assistance of the TEREZA Association in the Czech Republic, schools in the Czech Republic have been making and reporting daily measurements of surface ozone and surface meteorological data since 2001. Using a hand-held ozone monitor developed for GLOBE, students at several Czech schools have generated multiyear data records of surface ozone from 2001 to 2005. Analysis of the data shows surface ozone levels were anomalously high during the summer of 2003 relative to other summers. These findings are consistent with measurements by the European Environment Agency that highlights the summer of 2003 as having exceptionally long-lasting and spatially extensive episodes of high surface ozone, especially during the first half of August. Further analysis of the summer s prevailing meteorology shows not only that it was one of the hottest on record, a finding also seen in the student data, but the conditions for production of ozone were ideal. Findings such as these increase student, teacher, and scientist confidence in the utility of the GLOBE data for engaging budding scientists in the collection, analysis, and eventual interpretation of the data for inquiry-based education.

Projections of Future Summertime Ozone over the U.S.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfister, G. G.; Walters, Stacy; Lamarque, J. F.

This study uses a regional fully coupled chemistry-transport model to assess changes in surface ozone over the summertime U.S. between present and a 2050 future time period at high spatial resolution (12 km grid spacing) under the SRES A2 climate and RCP8.5 anthropogenic pre-cursor emission scenario. The impact of predicted changes in climate and global background ozone is estimated to increase surface ozone over most of the U.S; the 5th - 95th percentile range for daily 8-hour maximum surface ozone increases from 31-79 ppbV to 30-87 ppbV between the present and future time periods. The analysis of a set ofmore » meteorological drivers suggests that these mostly will add to increasing ozone, but the set of simulations conducted does not allow to separate this effect from that through enhanced global background ozone. Statistically the most robust positive feedbacks are through increased temperature, biogenic emissions and solar radiation. Stringent emission controls can counteract these feedbacks and if considered, we estimate large reductions in surface ozone with the 5th-95th percentile reduced to 27-55 ppbV. A comparison of the high-resolution projections to global model projections shows that even though the global model is biased high in surface ozone compared to the regional model and compared to observations, both the global and the regional model predict similar changes in ozone between the present and future time periods. However, on smaller spatial scales, the regional predictions show more pronounced changes between urban and rural regimes that cannot be resolved at the coarse resolution of global model. In addition, the sign of the changes in overall ozone mixing ratios can be different between the global and the regional predictions in certain regions, such as the Western U.S. This study confirms the key role of emission control strategies in future air quality predictions and demonstrates the need for considering degradation of air quality with future climate change in emission policy making. It also illustrates the need for high resolution modeling when the objective is to address regional and local air quality or establish links to human health and society.« less

California Baseline Ozone Transport Study (CABOTS): Ozonesonde Measurements

NASA Astrophysics Data System (ADS)

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.

Surface and Tropospheric Ozone Profile Variability (1999-2014) at the TOLNet Site of Table Mountain, California

NASA Astrophysics Data System (ADS)

Granados-Muñoz, M. J.; Leblanc, T.

2015-12-01

Ozone in the lower troposphere acts as an air pollutant affecting human health and vegetation. Tropospheric ozone sources and variability are not yet fully identified or understood and recent studies reveal the importance of increasing the number of tropospheric ozone profiling stations and long term measurements. As part of the international monitoring network NDACC, and the U.S.-based network TOLNet, a differential absorption lidar has been performing tropospheric ozone measurements (3-20 km) at the JPL Table Mountain Facility (TMF, California) since 1999, and surface measurements have been performed since 2013 with a UV photometric analyzer. Because of the site's geolocation and high elevation, background tropospheric ozone, unaffected by the boundary layer dynamics and local anthropogenic emissions of ozone precursors, is usually expected. However, transboundary ozone contributions such as stratospheric intrusions and Asian pollution episodes are frequently detected. In this study, a statistical analysis of the 14-year lidar profiles and the 2.5-year surface data is presented. Seasonal, interannual and diurnal variability and its possible causes (e.g. El Nino/La Nina events, North American Monsoon) are investigated. Together with the high elevation surface data gathered at TMF, surface data from ARB stations nearby are analyzed to understand the lowermost tropospheric ozone variability component. The frequency of stratospheric intrusions and Asian pollution episodes reaching the Western U.S. is also examined in an attempt to understand the relative contribution of each process to the observed variability throughout the troposphere. The Table Mountain surface and lidar measurements are expected to contribute significantly to the emerging system of global air quality observations, and to the improvement of global and regional data assimilation and modeling.

Development of Compact Ozonizer with High Ozone Output by Pulsed Power

NASA Astrophysics Data System (ADS)

Tanaka, Fumiaki; Ueda, Satoru; Kouno, Kanako; Sakugawa, Takashi; Akiyama, Hidenori; Kinoshita, Youhei

Conventional ozonizer with a high ozone output using silent or surface discharges needs a cooling system and a dielectric barrier, and therefore becomes a large machine. A compact ozonizer without the cooling system and the dielectric barrier has been developed by using a pulsed power generated discharge. The wire to plane electrodes made of metal have been used. However, the ozone output was low. Here, a compact and high repetition rate pulsed power generator is used as an electric source of a compact ozonizer. The ozone output of 6.1 g/h and the ozone yield of 86 g/kWh are achieved at 500 pulses per second, input average power of 280 W and an air flow rate of 20 L/min.

Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

NASA Technical Reports Server (NTRS)

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.

On the origin of regional spring time ozone episodes in the Western Mediterranean

NASA Astrophysics Data System (ADS)

Kalabokas, Pavlos; Hjorth, Jens; Foret, Gilles; Dufour, Gaëlle; Eremenko, Maxim; Siour, Guillaume; Cuesta, Juan; Beekmann, Matthias

2017-04-01

For the identification of regional spring time ozone episodes, rural EMEP ozone measurements from countries surrounding the Western Mediterranean (Spain, France, Switzerland, Italy, Malta) have been examined with emphasis on periods of high ozone, according to the daily variation of the afternoon (12:00 - 18:00) ozone. For two selected high ozone episodes in April-May 2008, composite NCEP/NCAR reanalysis maps of various meteorological parameters and/or their anomalies (geopotential height, specific humidity, vertical velocity omega, vector wind speed and temperature) at various tropospheric pressure levels have been examined together with the corresponding satellite IASI ozone measurements (at 3 and 10 km), CHIMERE simulations, vertical ozone soundings and HYSPLIT back trajectories (Kalabokas et al., 2016). The results show that high surface ozone is measured at several countries simultaneously over several days. Also, the examined spring ozone episodes in Western Mediterranean and Central Europe are linked to synoptic meteorological conditions very similar to those recently observed in summertime ozone episodes over the Eastern Mediterranean (Doche et al., 2014; Kalabokas et al., 2015 and references therein), where the transport of tropospheric ozone-rich air masses through atmospheric subsidence influences significantly the boundary layer and surface ozone concentrations. In particular, the geographic areas with observed tropospheric subsidence seem to be the transition regions between high pressure and low pressure systems. IASI satellite measurements show extended areas of high tropospheric ozone over the low pressure systems adjacent to the anticyclones, which influence significantly the boundary layer and surface ozone concentrations within the anticyclones by subsidence and advection, in addition to the photochemically produced ozone there, resulting to exceedances of the 60 ppb standard for human health protection over extended geographical areas. References Doche, C., Dufour, G., Foret, G., Eremenko, M., Cuesta, J., Beekmann, M., and Kalabokas, P., 2014. Summertime tropospheric-ozone variability over the Mediterranean basin observed with IASI, Atmos. Chem. Phys., 14, 10589-10600. Kalabokas P. D., Thouret V., Cammas J.-P., Volz-Τhomas A., Boulanger D., Repapis C.C., 2015. The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case), Tellus B, 67, 27853, http://dx.doi.org/10.3402/tellusb.v67.27853. Kalabokas P., J. Hjorth, G. Foret, G. Dufour, M. Eremenko, G. Siour, J. Cuesta, M. Beekmann, 2016. An investigation on the origin of regional spring time ozone episodes in the Western Mediterranean and Central Europe. Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-615.

Wintertime ozone fluxes and profiles above a subalpine spruce-fir forest

Treesearch

Karl Zeller

2000-01-01

High rural concentrations of ozone (O3) are thought to be stratospheric in origin, advected from upwind urban sources, or photochemically generated locally by natural trace gas emissions. Ozone is known to be transported vertically downward from the above-canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral surfaces. However...

Synoptic meteorological conditions associated with high spring and summer ozone levels at a rural site in the Eastern Mediterranean

NASA Astrophysics Data System (ADS)

Kalabokas, Pavlos; Repapis, Christos; Mihalopoulos, Nikos; Zerefos, Christos

2017-04-01

For the identification of the nature of spring and summertime ozone episodes, rural ozone measurements from the Eastern Mediterranean station of Finokalia-Crete, Greece during the first 4-year period of its record (1998-2001) have been analyzed with emphasis on periods of high ozone concentrations, according to the daily variation of the afternoon (12:00 - 18:00) ozone values. For the 7% highest spring and summertime ozone episodes composite NOAA/ESRL reanalysis maps of various meteorological parameters and/or their anomalies (geopotential height, specific humidity, vertical wind velocity omega, vector wind speed and temperature) have been examined together with their corresponding HYSPLIT back trajectories. This work is a continuation of a previous first approach regarding summer highest and lowest surface ozone episodes in Finokalia and other Central and Eastern Mediterranean stations (Kalabokas et al., 2008), which is now extended to more meteorological parameters and higher pressure levels. The results show that the examined synoptic meteorological condition during springtime ozone episodes over the Eastern Mediterranean station of Finokalia are quite similar with those conditions during high ozone springtime episodes observed at rural stations over the Western Mediterranean (Kalabokas et al., 2016). On the other hand the summer time synoptic conditions corresponding to highest surface ozone episodes at Finokalia are comparable with the conditions encountered during highest ozone episodes in the lower troposphere following analysis of MOZAIC vertical profiles over the Aegean Sea and the Eastern Mediterranean (Kalabokas et al., 2015 and references therein). During the highest ozone episodes, for both examined seasons, the transport of tropospheric ozone-rich air masses through atmospheric subsidence influences significantly the boundary layer and surface ozone concentrations. In particular, the geographic areas with observed tropospheric subsidence seem to be the transition regions between high and low pressure synoptic meteorological systems. References Kalabokas, P. D., Mihalopoulos, N., Ellul, R., Kleanthous, S., and Repapis, C. C., 2008. An investigation of the meteorological and photochemical factors influencing the background rural and marine surface ozone levels in the Central and Eastern Mediterranean, Atmos. Environ., 42, 7894-7906. Kalabokas P. D., Thouret V., Cammas J.-P., Volz-Τhomas A., Boulanger D., Repapis C.C., 2015. The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case), Tellus B, 67, 27853, http://dx.doi.org/10.3402/tellusb.v67.27853. Kalabokas P., J. Hjorth, G. Foret, G. Dufour, M. Eremenko, G. Siour, J. Cuesta, M. Beekmann, 2016. An investigation on the origin of regional spring time ozone episodes in the Western Mediterranean and Central Europe. Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-615.

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

NASA Astrophysics Data System (ADS)

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.

Responses of Surface Ozone Air Quality to Anthropogenic Nitrogen Deposition

NASA Astrophysics Data System (ADS)

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 implications for future air quality prediction.

Coincident Observations of Surface Ozone and NMVOCs over Abu Dhabi

NASA Astrophysics Data System (ADS)

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.

Surface ozone in the White Mountains of California

Treesearch

Joel Burley; Andrzej Bytnerowicz

2011-01-01

Surface ozone concentrations are presented for four high-elevation sites along a northesouth transect along the spine of the White Mountains and a fifth site located at lower elevation approximately 15 km to the west on the floor of the Owens Valley. The ozone data, which were collected from mid-June through mid-October of 2009, include results from two sites, White...

Quantifying Ozone Production throughout the Boundary Layer from High Frequency Tethered Profile Measurements during a High Ozone Episode in the Uinta Basin, Utah

NASA Astrophysics Data System (ADS)

Sterling, C. W.; Johnson, B.; Schnell, R. C.; Oltmans, S. J.; Cullis, P.; Hall, E. G.; Jordan, A. F.; Windell, J.; McClure-Begley, A.; Helmig, D.; Petron, G.

2015-12-01

During the Uinta Basin Winter Ozone Study (UBWOS) in Jan - Feb 2013, 735 tethered ozonesonde profiles were obtained at 3 sites including during high wintertime photochemical ozone production events that regularly exceeded 125 ppb. High resolution profiles of ozone and temperature with altitude, measured during daylight hours, showed the development of approximately week long high ozone episodes building from background levels of ~40 ppb to >150 ppb. The topography of the basin combined with a strong temperature inversion trapped oil and gas production effluents in the basin and the snow covered surface amplified the sun's radiation driving the photochemical ozone production at rates up to 13 ppb/hour in a cold layer capped at 1600-1700 meters above sea level. Beginning in mid-morning, ozone mixing ratios throughout the cold layer increased until late afternoon. Ozone mixing ratios were generally constant with height indicating that ozone production was nearly uniform throughout the depth of the cold pool. Although there was strong diurnal variation, ozone mixing ratios increased during the day more than decreased during the night, resulting in elevated levels the next morning; an indication that nighttime loss processes did not compensate for daytime production. Even though the 3 tethersonde sites were at elevations differing by as much as 140 m, the top of the high ozone layer was nearly uniform in altitude at the 3 locations. Mobile van surface ozone measurements across the basin confirmed this capped structure of the ozone layer; the vehicle drove out of high ozone mixing ratios at an elevation of ~1900 meters above sea level, above which free tropospheric ozone mixing ratios of ~50 ppb were measured. Exhaust plumes from a coal-fired power plant in the eastern portion of the basin were intercepted by the tethersondes. The structure of the profiles clearly showed that effluents in the plumes were not mixed downward and thus did not contribute precursor nitrogen oxides to the observed ozone production in the boundary layer.

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

NASA Astrophysics Data System (ADS)

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.

Low modeled ozone production suggests underestimation of precursor emissions (especially NOx) in Europe

NASA Astrophysics Data System (ADS)

Oikonomakis, Emmanouil; Aksoyoglu, Sebnem; Ciarelli, Giancarlo; Baltensperger, Urs; Prévôt, André Stephan Henry

2018-02-01

High surface ozone concentrations, which usually occur when photochemical ozone production takes place, pose a great risk to human health and vegetation. Air quality models are often used by policy makers as tools for the development of ozone mitigation strategies. However, the modeled ozone production is often not or not enough evaluated in many ozone modeling studies. The focus of this work is to evaluate the modeled ozone production in Europe indirectly, with the use of the ozone-temperature correlation for the summer of 2010 and to analyze its sensitivity to precursor emissions and meteorology by using the regional air quality model, the Comprehensive Air Quality Model with Extensions (CAMx). The results show that the model significantly underestimates the observed high afternoon surface ozone mixing ratios (≥ 60 ppb) by 10-20 ppb and overestimates the lower ones (< 40 ppb) by 5-15 ppb, resulting in a misleading good agreement with the observations for average ozone. The model also underestimates the ozone-temperature regression slope by about a factor of 2 for most of the measurement stations. To investigate the impact of emissions, four scenarios were tested: (i) increased volatile organic compound (VOC) emissions by a factor of 1.5 and 2 for the anthropogenic and biogenic VOC emissions, respectively, (ii) increased nitrogen oxide (NOx) emissions by a factor of 2, (iii) a combination of the first two scenarios and (iv) increased traffic-only NOx emissions by a factor of 4. For southern, eastern, and central (except the Benelux area) Europe, doubling NOx emissions seems to be the most efficient scenario to reduce the underestimation of the observed high ozone mixing ratios without significant degradation of the model performance for the lower ozone mixing ratios. The model performance for ozone-temperature correlation is also better when NOx emissions are doubled. In the Benelux area, however, the third scenario (where both NOx and VOC emissions are increased) leads to a better model performance. Although increasing only the traffic NOx emissions by a factor of 4 gave very similar results to the doubling of all NOx emissions, the first scenario is more consistent with the uncertainties reported by other studies than the latter, suggesting that high uncertainties in NOx emissions might originate mainly from the road-transport sector rather than from other sectors. The impact of meteorology was examined with three sensitivity tests: (i) increased surface temperature by 4 °C, (ii) reduced wind speed by 50 % and (iii) doubled wind speed. The first two scenarios led to a consistent increase in all surface ozone mixing ratios, thus improving the model performance for the high ozone values but significantly degrading it for the low ozone values, while the third scenario had exactly the opposite effects. Overall, the modeled ozone is predicted to be more sensitive to its precursor emissions (especially traffic NOx) and therefore their uncertainties, which seem to be responsible for the model underestimation of the observed high ozone mixing ratios and ozone production.

MARs Color Imager (MARCI) Daily Global Ozone Column Mapping from the Mars Reconnaissance Orbiter (MRO): A Survey of 2006-2010 Results

NASA Astrophysics Data System (ADS)

Clancy, R. T.; Wolff, M. J.; Malin, M. C.; Cantor, B. A.

2010-12-01

MARCI UV band imaging photometry within (260nm) and outside (320nm) the Hartley ozone band absorption supports daily global mapping of Mars ozone column abundances. Key retrieval issues include accurate UV radiometric calibrations, detailed specifications of surface and atmospheric background reflectance (surface albedo, atmospheric Raleigh and dust scattering/absorption), and simultaneous cloud retrievals. The implementation of accurate radiative transfer (RT) treatments of these processes has been accomplished (Wolff et al., 2010) such that daily global mapping retrievals for Mars ozone columns have been completed for the 2006-2010 period of MARCI global imaging. Ozone retrievals are most accurate for high column abundances associated with mid-to-high latitude regions during fall, winter, and spring seasons. We present a survey of these MARCI ozone column retrievals versus season, latitude, longitude, and year.

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

NASA Astrophysics Data System (ADS)

Barrett, Bradford S.; Raga, Graciela B.

2016-12-01

Surface ozone concentrations in Mexico City frequently exceed the Mexican standard and have proven difficult to forecast due to changes in meteorological conditions at its tropical location. The Madden-Julian Oscillation (MJO) is largely responsible for intraseasonal variability in the tropics. Circulation patterns in the lower and upper troposphere and precipitation are associated with the oscillation as it progresses eastward around the planet. It is typically described by phases (labeled 1 through 8), which correspond to the broad longitudinal location of the active component of the oscillation with enhanced precipitation. In this study we evaluate the intraseasonal variability of winter and summer surface ozone concentrations in Mexico City, which was investigated over the period 1986-2014 to determine if there is a modulation by the MJO that would aid in the forecast of high-pollution episodes. Over 1 000 000 hourly observations of surface ozone from five stations around the metropolitan area were standardized and then binned by active phase of the MJO, with phase determined using the real-time multivariate MJO index. Highest winter ozone concentrations were found in Mexico City on days when the MJO was active and in phase 2 (over the Indian Ocean), and highest summer ozone concentrations were found on days when the MJO was active and in phase 6 (over the western Pacific Ocean). Lowest winter ozone concentrations were found during active MJO phase 8 (over the eastern Pacific Ocean), and lowest summer ozone concentrations were found during active MJO phase 1 (over the Atlantic Ocean). Anomalies of reanalysis-based cloud cover and UV-B radiation supported the observed variability in surface ozone in both summer and winter: MJO phases with highest ozone concentration had largest positive UV-B radiation anomalies and lowest cloud-cover fraction, while phases with lowest ozone concentration had largest negative UV-B radiation anomalies and highest cloud-cover fraction. Furthermore, geopotential height anomalies at 250 hPa favoring reduced cloudiness, and thus elevated surface ozone, were found in both seasons during MJO phases with above-normal ozone concentrations. Similar height anomalies at 250 hPa favoring enhanced cloudiness, and thus reduced surface ozone, were found in both seasons during MJO phases with below-normal ozone concentrations. These anomalies confirm a physical pathway for MJO modulation of surface ozone via modulation of the upper troposphere.

Surface recombination of oxygen atoms in O2 plasma at increased pressure: II. Vibrational temperature and surface production of ozone

NASA Astrophysics Data System (ADS)

Lopaev, D. V.; Malykhin, E. M.; Zyryanov, S. M.

2011-01-01

Ozone production in an oxygen glow discharge in a quartz tube was studied in the pressure range of 10-50 Torr. The O3 density distribution along the tube diameter was measured by UV absorption spectroscopy, and ozone vibrational temperature TV was found comparing the calculated ab initio absorption spectra with the experimental ones. It has been shown that the O3 production mainly occurs on a tube surface whereas ozone is lost in the tube centre where in contrast the electron and oxygen atom densities are maximal. Two models were used to analyse the obtained results. The first one is a kinetic 1D model for the processes occurring near the tube walls with the participation of the main particles: O(3P), O2, O2(1Δg) and O3 molecules in different vibrational states. The agreement of O3 and O(3P) density profiles and TV calculated in the model with observed ones was reached by varying the single model parameter—ozone production probability (\\gamma_{O_{3}}) on the quartz tube surface on the assumption that O3 production occurs mainly in the surface recombination of physisorbed O(3P) and O2. The phenomenological model of the surface processes with the participation of oxygen atoms and molecules including singlet oxygen molecules was also considered to analyse \\gamma_{O_{3}} data obtained in the kinetic model. A good agreement between the experimental data and the data of both models—the kinetic 1D model and the phenomenological surface model—was obtained in the full range of the studied conditions that allowed consideration of the ozone surface production mechanism in more detail. The important role of singlet oxygen in ozone surface production was shown. The O3 surface production rate directly depends on the density of physisorbed oxygen atoms and molecules and can be high with increasing pressure and energy inputted into plasma while simultaneously keeping the surface temperature low enough. Using the special discharge cell design, such an approach opens up the possibility to develop compact ozonizers having high ozone yield at the low energy cost of O → O3 conversion.

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

NASA Astrophysics Data System (ADS)

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.

An Estimation of the Climatic Effects of Stratospheric Ozone Losses during the 1980s. Appendix K

NASA Technical Reports Server (NTRS)

MacKay, Robert M.; Ko, Malcolm K. W.; Shia, Run-Lie; Yang, Yajaing; Zhou, Shuntai; Molnar, Gyula

1997-01-01

In order to study the potential climatic effects of the ozone hole more directly and to assess the validity of previous lower resolution model results, the latest high spatial resolution version of the Atmospheric and Environmental Research, Inc., seasonal radiative dynamical climate model is used to simulate the climatic effects of ozone changes relative to the other greenhouse gases. The steady-state climatic effect of a sustained decrease in lower stratospheric ozone, similar in magnitude to the observed 1979-90 decrease, is estimated by comparing three steady-state climate simulations: 1) 1979 greenhouse gas concentrations and 1979 ozone, II) 1990 greenhouse gas concentrations with 1979 ozone, and III) 1990 greenhouse gas concentrations with 1990 ozone. The simulated increase in surface air temperature resulting from nonozone greenhouse gases is 0.272 K. When changes in lower stratospheric ozone are included, the greenhouse warming is 0.165 K, which is approximately 39% lower than when ozone is fixed at the 1979 concentrations. Ozone perturbations at high latitudes result in a cooling of the surface-troposphere system that is greater (by a factor of 2.8) than that estimated from the change in radiative forcing resulting from ozone depiction and the model's 2 x CO, climate sensitivity. The results suggest that changes in meridional heat transport from low to high latitudes combined with the decrease in the infrared opacity of the lower stratosphere are very important in determining the steady-state response to high latitude ozone losses. The 39% compensation in greenhouse warming resulting from lower stratospheric ozone losses is also larger than the 28% compensation simulated previously by the lower resolution model. The higher resolution model is able to resolve the high latitude features of the assumed ozone perturbation, which are important in determining the overall climate sensitivity to these perturbations.

Surface ozone at the Devils Postpile National Monument receptor site during low and high wildland fire years

Treesearch

Andrzej Bytnerowicz; Joel D. Burley; Ricardo Cisneros; Haiganoush K. Preisler; Susan Schilling; Donald Schweizer; John Ray; Deanna Dulen; Christopher Beck; Bianca Auble

2013-01-01

Surface ozone (O3) was measured at the Devils Postpile National Monument (DEPO), eastern Sierra Nevada Mountains, California, during the 2007 (low-fire) and 2008 (high-fire) summer seasons. While mean and median values of O3 concentrations for the 2007 and 2008 summer seasons were similar, maximum O3...

Responses of surface ozone air quality to anthropogenic nitrogen deposition in the Northern Hemisphere

NASA Astrophysics Data System (ADS)

Zhao, Yuanhong; Zhang, Lin; Tai, Amos P. K.; Chen, Youfan; Pan, Yuepeng

2017-08-01

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. Here we combine a chemical transport model (GEOS-Chem) and a global land model (Community Land Model, CLM) 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 the addition of atmospheric deposited nitrogen - namely, 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 (e.g., a 6.6 Tg increase in isoprene emission), but it could also decrease ozone due to higher ozone dry deposition velocities (up to 0.02-0.04 cm s-1 increases). Meanwhile, deposited anthropogenic nitrogen to soil enhances soil NOx emissions. The overall effect on summer mean surface ozone concentrations shows 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 implications for future air quality prediction.

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

NASA Astrophysics Data System (ADS)

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 reference for future model simulations.

Transboundary Contributions To Surface Ozone In California's Central Valley

NASA Astrophysics Data System (ADS)

Post, A.; Faloona, I. C.; Conley, S. A.; Lighthall, D.

2014-12-01

Rising concern over the impacts of exogenous air pollution in California's Central Valley has prompted the establishment of a coastal, high altitude monitoring site at the Chews Ridge Observatory (1550 m) approximately 30 km east of Point Sur in Monterey County, under the auspices of the Monterey Institute for Research in Astronomy. Two and a half years of continuous ozone data are presented in the context of long-range transport and its potential impact on surface air quality in the San Joaquin Valley (SJV). Past attempts to quantify the impact of transboundary ozone on surface levels have relied on uncertain model estimates, or have been limited to weekly ozonesonde data. Here, we present an observationally derived quantification of the contribution of free tropospheric ozone to surface sites in the San Joaquin Valley throughout three ozone seasons (June through September, 2012-2014). The diurnal ozone patterns at Chews Ridge, and their correlations with ozone aloft over the Valley, have been presented previously. Furthermore, reanalysis data of geopotential heights indicate consistent flow from Chews Ridge to the East, directly over the SJV. In a related airborne project we quantify the vertical exchange, or entrainment, rate over the Southern SJV from a series of focused flights measuring ozone concentrations during peak photochemical hours in conjunction with local meteorological data to quantify an ozone budget for the area. By applying the entrainment rates observed in that study here we are able to quantify the seasonal contributions of free tropospheric ozone measured at Chews Ridge to surface sites in the San Joaquin Valley, and compare prior model estimates to our observationally derived values.

Stratospheric Intrusion-Influenced Ozone Air Quality Exceedences Investigated in MERRA-2

NASA Technical Reports Server (NTRS)

Knowland, K. Emma; Ott, Lesley; Duncan, Bryan; Wargan, Krzysztof

2017-01-01

Ozone near the surface is harmful to human health and is a result of the photochemical reaction with both man-made and natural precursor pollutant sources. Therefore, in order to reduce near surface ozone concentrations, communities must reduce anthropogenic pollution sources. However, the injection of stratospheric ozone into the troposphere, known as a stratospheric intrusion, can also lead to concentrations of ground-level ozone exceeding air quality standards. Stratospheric intrusions are dynamical atmospheric features, however, these intrusions have been misrepresented in models and reanalyses until recently, as the features of a stratospheric intrusion are best identified in horizontal resolutions of approximately 50 km or smaller. NASA's Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) reanalysis is a publicly-available high-resolution dataset (50 km) with assimilated ozone that characterizes stratospheric ozone on the same spatiotemporal resolution as the meteorology. We show that stratospheric intrusions that impact surface air quality are well represented in the MERRA-2 reanalysis. This is demonstrated through a case study analysis of stratospheric intrusion events which were identified by the United States Environmental Protection Agency (EPA) to impact surface ozone air quality in spring 2012 in Colorado. The stratospheric intrusions are identified in MERRA-2 by the folding of the dynamical tropopause under the jet stream and subsequent isentropic descent of dry, O3-rich stratospheric air towards the surface where ozone air quality exceedences were observed. The MERRA-2 reanalysis can support air quality agencies for more rapid identification of the impact of stratospheric air on ground-level ozone.

Tropospheric Ozone Lidar Network (TOLNet) - Long-term Tropospheric Ozone and Aerosol Profiling for Satellite Continuity and Process Studies

NASA Astrophysics Data System (ADS)

Newchurch, M.; Al-Saadi, J. A.; Alvarez, R. J.; Burris, J.; Cantrell, W.; Chen, G.; De Young, R.; Hardesty, R.; Hoff, R. M.; Kaye, J. A.; kuang, S.; Langford, A. O.; LeBlanc, T.; McDermid, I. S.; McGee, T. J.; Pierce, R.; Senff, C. J.; Sullivan, J. T.; Szykman, J.; Tonnesen, G.; Wang, L.

2012-12-01

An interagency research initiative for ground-based ozone and aerosol lidar profiling recently funded by NASA has important applications to air-quality studies in addition to the goal of serving the GEO-CAPE and other air-quality missions. Ozone is a key trace-gas species, a greenhouse gas, and an important pollutant in the troposphere. High spatial and temporal variability of ozone affected by various physical and photochemical processes motivates the high spatio-temporal lidar profiling of tropospheric ozone for improving the simulation and forecasting capability of the photochemical/air-quality models, especially in the boundary layer where the resolution and precision of satellite retrievals are fundamentally limited. It is well known that there are large discrepancies between the surface and upper-air ozone due to titration, surface deposition, diurnal processes, free-tropospheric transport, and other processes. Near-ground ozone profiling has been technically challenging for lidars due to some engineering difficulties, such as near-range saturation, field-of-view overlap, and signal processing issues. This initiative provides an opportunity for us to solve those engineering issues and redesign the lidars aimed at long-term, routine ozone/aerosol observations from the near surface to the top of the troposphere at multiple stations (i.e., NASA/GSFC, NASA/LaRC, NASA/JPL, NOAA/ESRL, UAHuntsville) for addressing the needs of NASA, NOAA, EPA and State/local AQ agencies. We will present the details of the science investigations, current status of the instrumentation development, data access/protocol, and the future goals of this lidar network. Ozone lidar/RAQMS comparison of laminar structures.

The role of refinery flaring events and bay breezes on a high surface ozone episode during the Houston, Texas DISCOVER-AQ field campaign

NASA Astrophysics Data System (ADS)

Loughner, C.; Follette-Cook, M. B.; Fried, A.; Pickering, K. E.

2015-12-01

The highest observed surface ozone concentrations in the Houston metropolitan area in 2013 occurred on September 25, which coincided with the Texas DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign. Surface ozone was elevated throughout the Houston metropolitan area with maximum 8-hour average ozone peaking along the western shore of Galveston Bay, reaching 124 ppbv, almost 50 ppbv above the current EPA standard of 75 ppbv. The NASA P-3B aircraft observed plumes from refinery flares west and northwest of Galveston Bay that were transported over the water. Continental air pollution from the north was transported into the Houston metropolitan area where it mixed with locally generated emissions. A bay breeze circulation formed causing pollutants that were transported out over the water in the morning to recirculate back inland where they mixed with freshly emitted pollution near the bay breeze convergence zone. The highest surface ozone concentrations were reported near the bay breeze front. This ozone episode will be presented using measurements made during the DISCOVER-AQ field campaign and a CMAQ model simulation with integrated source apportionment, which tracks the contribution of emissions source groups and regions on ozone concentrations.

DESIGN ARTIFACTS IN EULERIAN REGIONAL AIR QUALITY MODELS: EVALUATION OF THE EFFECTS OF LAYER THICKNESS AND VERTICAL PROFILE CORRECTION ON SURFACE OZONE CONCENTRATIONS

EPA Science Inventory

Evaluation studies of the Regional Acid Deposition Model (RADM) results have revealed that there exists high bias of surface SO2 and O3 concentrations by the model, especially during nighttime hours. omparison of the RADM results with surface measurements of hourly ozone concentr...

Atmospheric pressure atomic layer deposition of Al₂O₃ using trimethyl aluminum and ozone.

PubMed

Mousa, Moataz Bellah M; Oldham, Christopher J; Parsons, Gregory N

2014-04-08

High throughput spatial atomic layer deposition (ALD) often uses higher reactor pressure than typical batch processes, but the specific effects of pressure on species transport and reaction rates are not fully understood. For aluminum oxide (Al2O3) ALD, water or ozone can be used as oxygen sources, but how reaction pressure influences deposition using ozone has not previously been reported. This work describes the effect of deposition pressure, between ∼2 and 760 Torr, on ALD Al2O3 using TMA and ozone. Similar to reports for pressure dependence during TMA/water ALD, surface reaction saturation studies show self-limiting growth at low and high pressure across a reasonable temperature range. Higher pressure tends to increase the growth per cycle, especially at lower gas velocities and temperatures. However, growth saturation at high pressure requires longer O3 dose times per cycle. Results are consistent with a model of ozone decomposition kinetics versus pressure and temperature. Quartz crystal microbalance (QCM) results confirm the trends in growth rate and indicate that the surface reaction mechanisms for Al2O3 growth using ozone are similar under low and high total pressure, including expected trends in the reaction mechanism at different temperatures.

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

NASA Astrophysics Data System (ADS)

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

2005-02-01

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/O2 mixtures with the maximum efficiency (energy yield) of 23 g kW h-1 for 40% argon content.

The influence of meteorological factors and biomass burning on surface ozone concentrations at Tanah Rata, Malaysia

NASA Astrophysics Data System (ADS)

Toh, Ying Ying; Lim, Sze Fook; von Glasow, Roland

2013-05-01

The surface ozone concentrations at the Tanah Rata regional Global Atmosphere Watch (GAW) station, Malaysia (4°28‧N, 101°23‧E, 1545 m above Mean Sea Level (MSL)) from June 2006 to August 2008 were analyzed in this study. Overall the ozone mixing ratios are very low; the seasonal variations show the highest mixing ratios during the Southwest monsoon (average 19.1 ppb) and lowest mixing ratios during the spring intermonsoon (average 14.2 ppb). The diurnal variation of ozone is characterised by an afternoon maximum and night time minimum. The meteorological conditions that favour the formation of high ozone levels at this site are low relative humidity, high temperature and minimum rainfall. The average ozone concentration is lower during precipitation days compared to non-precipitation days. The hourly averaged ozone concentrations show significant correlations with temperature and relative humidity during the Northeast monsoon and spring intermonsoon. The highest concentrations are observed when the wind is blowing from the west. We found an anticorrelation between the atmospheric pressure tide and ozone concentrations. The ozone mixing ratios do not exceed the recommended Malaysia Air Quality Guidelines for 1-h and 8-h averages. Five day backward trajectories on two high ozone episodes in 07 August 2006 (40.0 ppb) and 24 February 2008 (45.7 ppb) are computed using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to investigate the origin of the pollutants and influence of regional transport. The high ozone episode during 07 August 2006 (burning season during southwest monsoon) is mainly attributed to regional transport from biomass burning in Sumatra, whereas favourable meteorological conditions (i.e. low relative humidity, high temperature and solar radiation, zero rainfall) and long range transport from Indo-China have elevated the ozone concentrations during 24 February 2008.

The microbial killing capacity of aqueous and gaseous ozone on different surfaces contaminated with dairy cattle manure

PubMed Central

Lowe, James

2018-01-01

A high reactivity and leaving no harmful residues make ozone an effective disinfectant for farm hygiene and biosecurity. Our objectives were therefore to (1) characterize the killing capacity of aqueous and gaseous ozone at different operational conditions on dairy cattle manure-based pathogens (MBP) contaminated different surfaces (plastic, metal, nylon, rubber, and wood); (2) determine the effect of microbial load on the killing capacity of aqueous ozone. In a crossover design, 14 strips of each material were randomly assigned into 3 groups, treatment (n = 6), positive-control (n = 6), and negative-control (n = 2). The strips were soaked in dairy cattle manure with an inoculum level of 107–108 for 60 minutes. The treatment strips were exposed to aqueous ozone of 2, 4, and 9 ppm and gaseous ozone of 1and 9 ppm for 2, 4, and 8 minutes exposure. 3M™ Petrifilm™ rapid aerobic count plate and plate reader were used for bacterial culture. On smooth surfaces, plastic and metal, aqueous ozone at 4 ppm reduced MBP to a safe level (≥5-log10) within 2 minutes (6.1 and 5.1-log10, respectively). However, gaseous ozone at 9 ppm for 4 minutes inactivated 3.3-log10 of MBP. Aqueous ozone of 9 ppm is sufficient to reduce MBP to a safe level, 6.0 and 5.4- log10, on nylon and rubber surfaces within 2 and 8 minutes, respectively. On complex surfaces, wood, both aqueous and gaseous ozone at up to 9 ppm were unable to reduce MBP to a safe level (3.6 and 0.8-log10, respectively). The bacterial load was a strong predictor for reduction in MBP (P<0.0001, R2 = 0.72). We conclude that aqueous ozone of 4 and 9 ppm for 2 minutes may provide an efficient method to reduce MBP to a safe level on smooth and moderately rough surfaces, respectively. However, ozone alone may not an adequate means of controlling MBP on complex surfaces. PMID:29758045

Influence of the West Pacific subtropical high on surface ozone daily variability in summertime over eastern China

NASA Astrophysics Data System (ADS)

Zhao, Zijian; Wang, Yuxuan

2017-12-01

The West Pacific subtropical high (WPSH), as one of the most important components of the East Asian summer monsoon (EASM), is the key synoptic-scale circulation pattern influencing summertime precipitation and atmospheric conditions in China. Here we investigate the impacts of the WPSH on surface ozone daily variability over eastern China, using observations from recently established network of ozone monitors and meteorology reanalysis data during summer (June, July, August; JJA) 2014-2016 with a focus on 2014. An empirical orthogonal function (EOF) analysis of daily ozone variations reveals that the dominating eigenvector (EOF1), which contributes a quarter (25.2%) to the total variances, is a marked north-south contrast. This pattern is temporally well correlated (r = -0.66, p < 0.01) with daily anomalies of a normalized WPSH intensity index (WPSH-I). Spatially, the WPSH-I and ozone correlation is positive in North China (NC) but negative in South China (SC), which well correlates with the ozone EOF1 pattern showing the same north-south contrast (r = -0.86, p < 0.01). These associations suggest the dominant component of surface ozone daily variability in eastern China is linked with the variability of the WPSH intensity in that a stronger WPSH leads to a decrease of surface ozone over SC but an increase over NC and vice versa. This is because a stronger WPSH enhances southwesterly transport of moisture into SC, creating such conditions not conducive for ozone formation as higher RH, more cloudiness and precipitation, less UV radiation, and lower temperature. Meanwhile, as most of the rainfall due to the enhanced southwesterly transport of moisture occurs in SC, water vapor is largely depleted in the air masses transported towards NC, creating dry and sunny conditions over NC under a strong WPSH, thereby promoting ozone formation.

Impact of downward-mixing ozone on surface ozone accumulation in southern Taiwan.

PubMed

Lin, Ching-Ho

2008-04-01

The ozone that initially presents in the previous day's afternoon mixing layer can remain in the nighttime atmosphere and then be carried over to the next morning. Finally, this ozone can be brought to the ground by downward mixing as mixing depth increases during the daytime, thereby increasing surface ozone concentrations. Variation of ozone concentration during each of these periods is investigated in this work. First, ozone concentrations existing in the daily early morning atmosphere at the altitude range of the daily maximum mixing depth (residual ozone concentrations) were measured using tethered ozonesondes on 52 experimental days during 2004-2005 in southern Taiwan. Daily downward-mixing ozone concentrations were calculated by a box model coupling the measured daily residual ozone concentrations and daily mixing depth variations. The ozone concentrations upwind in the previous day's afternoon mixing layer were estimated by the combination of back air trajectory analysis and known previous day's surface ozone distributions. Additionally, the relationship between daily downward-mixing ozone concentration and daily photochemically produced ozone concentration was examined. The latter was calculated by removing the former from daily surface maximum ozone concentration. The measured daily residual ozone concentrations distributed at 12-74 parts per billion (ppb) with an average of 42 +/- 17 ppb are well correlated with the previous upwind ozone concentration (R2 = 0.54-0.65). Approximately 60% of the previous upwind ozone was estimated to be carried over to the next morning and became the observed residual ozone. The daily downward-mixing ozone contributes 48 +/- 18% of the daily surface maximum ozone concentration, indicating that the downward-mixing ozone is as important as daily photochemically produced ozone to daily surface maximum ozone accumulation. The daily downward-mixing ozone is poorly correlated with the daily photochemically produced ozone and contributes significantly to the daily variation of surface maximum ozone concentrations (R2 = 0.19). However, the contribution of downward-mixing ozone to daily ozone variation is not included in most existing statistical models developed for predicting daily ozone variation. Finally, daily surface maximum ozone concentration is positively correlated with daily afternoon mixing depth, attributable to the downward-mixing ozone.

Attenuation by clouds of UV radiation for low stratospheric ozone conditions

NASA Astrophysics Data System (ADS)

Orte, Facundo; Wolfram, Elian; Salvador, Jacobo; D'Elia, Raúl; Quiroga, Jonathan; Quel, Eduardo; Mizuno, Akira

2017-02-01

Stratospheric poor ozone air masses related to the polar ozone hole overpass subpolar regions in the Southern Hemisphere during spring and summer seasons, resulting in increases of surface Ultraviolet Index (UVI). The impact of these abnormal increases in the ultraviolet radiation could be overestimated if clouds are not taking into account. The aim of this work is to determine the percentage of cases in which cloudiness attenuates the high UV radiation that would reach the surface in low total ozone column situations and in clear sky hypothetical condition for Río Gallegos, Argentina. For this purpose, we analysed UVI data obtained from a multiband filter radiometer GUV-541 (Biospherical Inc.) installed in the Observatorio Atmosférico de la Patagonia Austral (OAPA-UNIDEF (MINDEF - CONICET)) (51 ° 33' S, 69 ° 19' W), Río Gallegos, since 2005. The database used covers the period 2005-2012 for spring seasons. Measured UVI values are compared with UVI calculated using a parametric UV model proposed by Madronich (2007), which is an approximation for the UVI for clear sky, unpolluted atmosphere and low surface albedo condition, using the total ozone column amount, obtained from the OMI database for our case, and the solar zenith angle. It is observed that ˜76% of the total low ozone amount cases, which would result in high and very high UVI categories for a hypothetical (modeled) clear sky condition, are attenuated by clouds, while 91% of hypothetical extremely high UVI category are also attenuated.

Seasonal prediction of US summertime ozone using statistical analysis of large scale climate patterns.

PubMed

Shen, Lu; Mickley, Loretta J

2017-03-07

We develop a statistical model to predict June-July-August (JJA) daily maximum 8-h average (MDA8) ozone concentrations in the eastern United States based on large-scale climate patterns during the previous spring. We find that anomalously high JJA ozone in the East is correlated with these springtime patterns: warm tropical Atlantic and cold northeast Pacific sea surface temperatures (SSTs), as well as positive sea level pressure (SLP) anomalies over Hawaii and negative SLP anomalies over the Atlantic and North America. We then develop a linear regression model to predict JJA MDA8 ozone from 1980 to 2013, using the identified SST and SLP patterns from the previous spring. The model explains ∼45% of the variability in JJA MDA8 ozone concentrations and ∼30% variability in the number of JJA ozone episodes (>70 ppbv) when averaged over the eastern United States. This seasonal predictability results from large-scale ocean-atmosphere interactions. Warm tropical Atlantic SSTs can trigger diabatic heating in the atmosphere and influence the extratropical climate through stationary wave propagation, leading to greater subsidence, less precipitation, and higher temperatures in the East, which increases surface ozone concentrations there. Cooler SSTs in the northeast Pacific are also associated with more summertime heatwaves and high ozone in the East. On average, models participating in the Atmospheric Model Intercomparison Project fail to capture the influence of this ocean-atmosphere interaction on temperatures in the eastern United States, implying that such models would have difficulty simulating the interannual variability of surface ozone in this region.

Seasonal prediction of US summertime ozone using statistical analysis of large scale climate patterns

PubMed Central

Mickley, Loretta J.

2017-01-01

We develop a statistical model to predict June–July–August (JJA) daily maximum 8-h average (MDA8) ozone concentrations in the eastern United States based on large-scale climate patterns during the previous spring. We find that anomalously high JJA ozone in the East is correlated with these springtime patterns: warm tropical Atlantic and cold northeast Pacific sea surface temperatures (SSTs), as well as positive sea level pressure (SLP) anomalies over Hawaii and negative SLP anomalies over the Atlantic and North America. We then develop a linear regression model to predict JJA MDA8 ozone from 1980 to 2013, using the identified SST and SLP patterns from the previous spring. The model explains ∼45% of the variability in JJA MDA8 ozone concentrations and ∼30% variability in the number of JJA ozone episodes (>70 ppbv) when averaged over the eastern United States. This seasonal predictability results from large-scale ocean–atmosphere interactions. Warm tropical Atlantic SSTs can trigger diabatic heating in the atmosphere and influence the extratropical climate through stationary wave propagation, leading to greater subsidence, less precipitation, and higher temperatures in the East, which increases surface ozone concentrations there. Cooler SSTs in the northeast Pacific are also associated with more summertime heatwaves and high ozone in the East. On average, models participating in the Atmospheric Model Intercomparison Project fail to capture the influence of this ocean–atmosphere interaction on temperatures in the eastern United States, implying that such models would have difficulty simulating the interannual variability of surface ozone in this region. PMID:28223483

Efficiency of activated carbon to transform ozone into *OH radicals: influence of operational parameters.

PubMed

Sánchez-Polo, M; von Gunten, U; Rivera-Utrilla, J

2005-09-01

Based on previous findings (Jans, U., Hoigné, J., 1998. Ozone Sci. Eng. 20, 67-87), the activity of activated carbon for the transformation of ozone into *OH radicals including the influence of operational parameters (carbon dose, ozone dose, carbon-type and carbon treatment time) was quantified. The ozone decomposition constant (k(D)) was increased by the presence of activated carbon in the system and depending on the type of activated carbon added, the ratio of the concentrations of *OH radicals and ozone, the R(ct) value ([*OH]/[O3]), was increased by a factor 3-5. The results obtained show that the surface chemical and textural characteristics of the activated carbon determines its activity for the transformation of ozone into *OH radicals. The most efficient carbons in this process are those with high basicity and large surface area. The obtained results show that the interaction between ozone and pyrrol groups present on the surface of activated carbon increase the concentration of O2*- radicals in the system, enhancing ozone transformation into *OH radicals. The activity of activated carbon decreases for extended ozone exposures. This may indicate that activated carbon does not really act as a catalyst but rather as a conventional initiator or promoter for the ozone transformation into *OH radicals. Ozonation of Lake Zurich water ([O3] = 1 mg/L) in presence of activated carbon (0.5 g/L) lead to an increase in the k(D) and R(ct) value by a factor of 10 and 39, respectively, thereby favouring the removal of ozone-resistant contaminants. Moreover, the presence of activated carbon during ozonation of Lake Zurich water led to a 40% reduction in the content of dissolved organic carbon during the first 60 min of treatment. The adsorption of low concentrations of dissolved organic matter (DOM) on activated carbon surfaces did not modify its capacity to initiate/promote ozone transformation into *OH radicals.

The Sensitivity of U.S. Surface Ozone Formation to NOx, and VOCs as Viewed from Space

NASA Technical Reports Server (NTRS)

Duncan, Bryan N.; Yoshida, Yasuko; Sillman, Sanford; Retscher, Christian; Pickering, Kenneth E.; Martin, Randall V.; Celarier, Edward A.

2009-01-01

We investigated variations in the sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NO(x)) as inferred from the ratio of tropospheric columns of formaldehyde and nitrogen dioxide from the Aura Ozone Monitoring Instrument (OMI). The data indicate that ozone formation became: 1. more sensitive to NO(x) over most of the U.S, from 2005 to 2007 because of substantial decreases in NO(x) emissions primarily from stationary sources, and 2. more sensitive to NO(x) with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. Based on our interpretation of the data, current strategies implemented to reduce unhealthy levels of surface ozone should focus more on reducing NO(x) emissions, except in some downtown areas which have historically benefited from reductions in VOC emissions.

Quantifying isentropic stratosphere-troposphere exchange of ozone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Huang; Chen, Gang; Tang, Qi

There is increased evidence that stratosphere-troposphere exchange (STE) of ozone has a significant impact on tropospheric chemistry and radiation. Traditional diagnostics of STE consider the ozone budget in the lowermost stratosphere (LMS) as a whole. However, this can only render the hemispherically integrated ozone flux and therefore does not distinguish the exchange of ozone into low latitudes from that into high latitudes. The exchange of ozone at different latitudes may have different tropospheric impacts. This present study extends the traditional approach from the entire LMS to individual isentropic layers in the LMS and therefore gives the meridional distribution of STEmore » by the latitudes where each isentropic surface intersects the tropopause. The specified dynamics version of the Whole Atmosphere Community Climate Model is used to estimate the STE ozone flux on each isentropic surface. It is found that net troposphere-to-stratosphere ozone transport occurs in low latitudes along the 350–380 K isentropic surfaces and that net stratosphere-to-troposphere ozone transport takes place in the extratropics along the 280–350 K isentropes. Particularly, the seasonal cycle of extratropical STE ozone flux in the Northern Hemisphere displays a maximum in late spring and early summer, following the seasonal migration of the upper tropospheric jet and associated isentropic mixing. Moreover, differential diabatic heating and isentropic mixing tend to induce STE ozone fluxes in opposite directions, but the net effect results in a spatiotemporal pattern similar to the STE ozone flux associated with isentropic mixing.« less

Quantifying isentropic stratosphere-troposphere exchange of ozone

DOE PAGES

Yang, Huang; Chen, Gang; Tang, Qi; ...

2016-03-25

There is increased evidence that stratosphere-troposphere exchange (STE) of ozone has a significant impact on tropospheric chemistry and radiation. Traditional diagnostics of STE consider the ozone budget in the lowermost stratosphere (LMS) as a whole. However, this can only render the hemispherically integrated ozone flux and therefore does not distinguish the exchange of ozone into low latitudes from that into high latitudes. The exchange of ozone at different latitudes may have different tropospheric impacts. This present study extends the traditional approach from the entire LMS to individual isentropic layers in the LMS and therefore gives the meridional distribution of STEmore » by the latitudes where each isentropic surface intersects the tropopause. The specified dynamics version of the Whole Atmosphere Community Climate Model is used to estimate the STE ozone flux on each isentropic surface. It is found that net troposphere-to-stratosphere ozone transport occurs in low latitudes along the 350–380 K isentropic surfaces and that net stratosphere-to-troposphere ozone transport takes place in the extratropics along the 280–350 K isentropes. Particularly, the seasonal cycle of extratropical STE ozone flux in the Northern Hemisphere displays a maximum in late spring and early summer, following the seasonal migration of the upper tropospheric jet and associated isentropic mixing. Moreover, differential diabatic heating and isentropic mixing tend to induce STE ozone fluxes in opposite directions, but the net effect results in a spatiotemporal pattern similar to the STE ozone flux associated with isentropic mixing.« less

Quantitative analysis of interaction between the free troposphere and planetary boundary layer using multiple measurements and large eddy simulation model

NASA Astrophysics Data System (ADS)

Huang, Guanyu

We investigate the interaction between the free troposphere (FT) and planetary boundary layer (PBL) using multiple measurements and Dutch Atmospheric Large Eddy Simulation (DALES) coupled with a chemical module. A residual layer (RL) storing high ozone concentrations can significantly influence ground ozone concentration through the entrainment process whereby the RL aloft is incorporated into the growing convective boundary layer (CBL) during the morning transition. We use DALES model coupled with a chemical module to simultaneously study the dynamical and chemical impacts of a RL (200-1200 m above ground level (AGL)) on ground-level (0-200 m AGL) ozone concentrations. Four numerical experiments test these interactions: 1) a RL with high ozone (100 ppb); 2) a RL with low ozone (50 ppb); 3) no RL with high ozone above the NBL (100 ppb from 200-1200 m AGL); and 4) no RL with low ozone above the NBL (50 ppb). The results indicate that ozone stored in the RL can contribute up to 86% of the ozone concentration in the CBL during the following day in Case 1. Even in Case 2, 64% of the ozone in the developed CBL results from intrusions from the RL. Additionally, a RL also increases the enhancement rate of ozone in the CBL. Furthermore, we investigate the ozone diurnal variation on September 6, 2013 in Huntsville AL. The ozone variation in the CBL is mainly caused by local emissions due to the weather conditions being controlled by an anticyclonic system. The local chemical production contributes over 67% of the ozone enhancement in the CBL. The dynamical processes contribute the rest. The numerical experiments show good agreement with our ozone lidar observations. However, our simulation results and ozone lidar observations fail to reproduce a declining trend of surface ozone measured by an Environment Protection Agency (EPA) surface monitoring station that is 6 km south of our facilities, which is very likely due to the large ozone horizontal variation and the diurnal variation of ozone dry deposition under urban environment.

Comparison between assimilated and non-assimilated experiments of the MACCii global reanalysis near surface ozone

NASA Astrophysics Data System (ADS)

Tsikerdekis, Athanasios; Katragou, Eleni; Zanis, Prodromos; Melas, Dimitrios; Eskes, Henk; Flemming, Johannes; Huijnen, Vincent; Inness, Antje; Kapsomenakis, Ioannis; Schultz, Martin; Stein, Olaf; Zerefos, Christos

2014-05-01

In this work we evaluate near surface ozone concentrations of the MACCii global reanalysis using measurements from the EMEP and AIRBASE database. The eight-year long reanalysis of atmospheric composition data covering the period 2003-2010 was constructed as part of the FP7-funded Monitoring Atmospheric Composition and Climate project by assimilating satellite data into a global model and data assimilation system (Inness et al., 2013). The study mainly focuses in the differences between the assimilated and the non-assimilated experiments and aims to identify and quantify any improvements achieved by adding data assimilation to the system. Results are analyzed in eight European sub-regions and region-specific Taylor plots illustrate the evaluation and the overall predictive skill of each experiment. The diurnal and annual cycles of near surface ozone are evaluated for both experiments. Furthermore ozone exposure indices for crop growth (AOT40), human health (SOMO35) and the number of days that 8-hour ozone averages exceeded 60ppb and 90ppb have been calculated for each station based on both observed and simulated data. Results indicate mostly improvement of the assimilated experiment with respect to the high near surface ozone concentrations, the diurnal cycle and range and the bias in comparison to the non-assimilated experiment. The limitations of the comparison between assimilated and non-assimilated experiments for near surface ozone are also discussed.

Ozone decomposition

PubMed Central

Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho

2014-01-01

Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates. PMID:26109880

Ozone maxima over Southern Africa: A mid-latitude link

NASA Technical Reports Server (NTRS)

Barsby, Jane; Diab, Roseanne D.

1994-01-01

The relationship between patterns of total ozone and day-to-day weather was explored over South Africa for the period 1987 to 1988. Generally, there was a fairly poor relationship (variance less than 20 percent) between total ozone and the heights of the 100, 300 and 500 hPa geopotential heights at 5 South African stations. However, over a shorter period, October to December 1988, fluctuations in the height of the 300 hPa surface accounted for 53 percent of the variance in total ozone at Cape Town. High ozone amounts are associated with the lowering of the 300 hPa surface in the presence of an upper-air trough. The role of the mid-latitude westerly waves in this respect is discussed.

Influence of wildfires on the variability and trend of ozone concentrations in the U.S. Intermountain West

NASA Astrophysics Data System (ADS)

Lu, Xiao; Zhang, Lin; Zhao, Yuanhong; Yue, Xu

2016-04-01

Wildfires are important sources of ozone by emitting large amounts of NOx and NMVOC, main ozone precursors at both global and regional scales. Their influences on ozone in the U.S. Intermountain West have recently received much interest because surface ozone concentrations over that region showed an increasing trend in the past two decades likely due to increasing wildfire emissions in a warming climate. Here we use the Lagrangian particle dispersion model (FLEXPART) as well as the GEOS-Chem chemical transport model to estimate wildfires' contribution on summer (June, July and August; JJA) ozone concentration variations, trends, and extremely high ozone events over the US Intermountain West for the past 22 years (1989-2010). We combine the resident time estimated from the FLEXPART 5-day backward trajectories and a high-resolution fire inventory to define a fire index representing the impact of wildfires on ozone concentration at a particular site for each day of summers 1989-2010. Over 26,000 FLEXPART back-trajectories are conducted for the whole time period and for 13 CASTNet surface monitoring sites. We build a stepwise multiple linear regression (SMLR) model of daily ozone concentrations using fire index and other meteorological variables for each site. The SMLR models explain 53% of the ozone variations (ranging from 12% to 68% for each site). We show that ozone produced from wildfires (calculated from SMLR model) are of high variability at daily scale (ranging from 0.1 ppbv to 20.7 ppbv), but are averaged to lower values of about 0.25-3.5 ppbv for summer mean. We estimate that wildfires magnify inter-annual variations of the regional mean summer ozone for about 32%, compared to the result with wildfires impact excluded from the SMLR model. Wildfire ozone enhancements increase at a rate of 0.04 ppbv per year, accouting for about 20% of the regional summer ozone trend during 1989-2010. Removing wildfires' impact would reduce 35% (46%) of the high-ozone days with measured daily ozone concentrations exceeding 65(75) ppbv, indicating their significant influence on ozone exceptional events. We further compare the wildfire ozone enhancements estimated by the statistical and Lagrangian approach with those estimated from a Eulerian model (GEOS-Chem). Despite highly-correlated results, GEOS-Chem largely overestimates wildfire ozone influences near the source regions and fails to capture ozone production from wildfires at long distance, reflecting deficiencies in current Eulerian models to capture small-scale emissions.

Characterization of natural organic matter treated by iron oxide nanoparticle incorporated ceramic membrane-ozonation process.

PubMed

Park, Hosik; Kim, Yohan; An, Byungryul; Choi, Heechul

2012-11-15

In this study, changes in the physical and structural properties of natural organic matter (NOM) were observed during hybrid ceramic membrane processes that combined ozonation with ultrafiltration ceramic membrane (CM) or with a reactive ceramic membrane (RM), namely, an iron oxide nanoparticles (IONs) incorporated-CM. NOM from feed water and NOM from permeate treated with hybrid ceramic membrane processes were analyzed by employing several NOM characterization techniques. Specific ultraviolet absorbance (SUVA), high-performance size exclusion chromatography (HPSEC) and fractionation analyses showed that the hybrid ceramic membrane process effectively removed and transformed relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions. Fourier transform infrared spectroscopy (FTIR) and 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy revealed that this process caused a significant decrease of the aromaticity of humic-like structures and an increase in electron withdrawing groups. The highest removal efficiency (46%) of hydroxyl radical probe compound (i.e., para-Chlorobenzoic acid (pCBA)) in RM-ozonation process compared with that in CM without ozonation process (8%) revealed the hydroxyl radical formation by the surface-catalyzed reaction between ozone and IONs on the surface of RM. In addition, experimental results on flux decline showed that fouling of RM-ozonation process (15%) was reduced compared with that of CM without ozonation process (30%). These results indicated that the RM-ozonation process enhanced the destruction of NOM and reduced the fouling by generating hydroxyl radicals from the catalytic ozonation in the RM-ozonation process. Copyright © 2012 Elsevier Ltd. All rights reserved.

Atmospheric Impacts of Emissions from Oil and Gas Development in the Uintah Basin, Utah, USA

NASA Astrophysics Data System (ADS)

Helmig, D.; Boylan, P. J.; Hueber, J.; Van Dam, B. A.; Mauldin, L.; Parrish, D. D.

2012-12-01

In the Uintah Basin in northeast Utah, USA, surface ozone levels during winter months have approached and on occasion exceeded the US National Ambient Air Quality Standard (NAAQS). Emissions from the extensive oil and gas exploration in this region are suspected to be the cause of these ozone episodes; however emission rates and photochemical processes are uncertain. During February 2012 continuous surface measurements and vertical profiling from a tethered balloon platform at the Horsepool site yielded high resolution boundary layer profile data on ozone and ozone precursor compounds, i.e. nitrogen oxides and volatile organic compounds as well as methane. Findings from this study were: 1. Surface ozone during the study period, which had no snow cover, did not exceed the NAAQS. 2. Nitrogen oxides varied from 1-50 ppbv pointing towards significant emission sources, likely from oil and gas operations. 3. Methane concentrations were elevated, reaching up to ~10 times its Northern Hemisphere (NH) atmospheric background. 3. Light non-methane hydrocarbons (NMHC) constituted the main fraction of volatile organic compounds. NMHC concentrations were highly elevated, exceeding levels seen in urban areas. 4. Ozone, methane, NOx and VOC showed distinct diurnal cycles, with large concentration increases seen at night, except for ozone, which showed the opposite behavior. 5. During nighttime concentrations of NOx, NMHC, and methane built up near the surface to levels that were much higher than their daytime concentrations. 6. Comparing NMHC to methane concentrations indicates a mass flux ratio of ~30% for total VOC/methane emissions for the Uintah Basin.

Factors dominating 3-dimensional ozone distribution during high tropospheric ozone period.

PubMed

Chen, Xiaoyang; Liu, Yiming; Lai, Anqi; Han, Shuangshuang; Fan, Qi; Wang, Xuemei; Ling, Zhenhao; Huang, Fuxiang; Fan, Shaojia

2018-01-01

Data from an in situ monitoring network and five ozone sondes are analysed during August of 2012, and a high tropospheric ozone episode is observed around the 8th of AUG. The Community Multi-scale Air Quality (CMAQ) model and its process analysis tool were used to study factors and mechanisms for high ozone mixing ratio at different levels of ozone vertical profiles. A sensitive scenario without chemical initial and boundary conditions (ICBCs) from MOZART4-GEOS5 was applied to study the impact of stratosphere-troposphere exchange (STE) on vertical ozone. The simulation results indicated that the first high ozone peak near the tropopause was dominated by STE. Results from process analysis showed that: in the urban area, the second peak at approximately 2 km above ground height was mainly caused by local photochemical production. The third peak (near surface) was mainly caused by the upwind transportation from the suburban/rural areas; in the suburban/rural areas, local photochemical production of ozone dominated the high ozone mixing ratio from the surface to approximately 3 km height. Furthermore, the capability of indicators to distinguish O 3 -precursor sensitivity along the vertical O 3 profiles was investigated. Two sensitive scenarios, which had cut 30% anthropogenic NO X or VOC emissions, showed that O 3 -precursor indicators, specifically the ratios of O 3 /NOy, H 2 O 2 /HNO 3 or H 2 O 2 /NO Z , could partly distinguish the O 3 -precursor sensitivity between VOCs-sensitive and NOx-sensitive along the vertical profiles. In urban area, the O 3 -precursor relationship transferred from VOCs-sensitive within the boundary layer to NOx-sensitive at approximately 1-3 km above ground height, further confirming the dominant roles of transportation and photochemical production in high O 3 peaks at the near-ground layer and 2 km above ground height, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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 deposition vs. isoprene emissions to quantify the impact of each process on surface ozone seasonal cycles and compare to the changes induced by declining anthropogenic NOx emissions (RCP8.5).

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

PubMed Central

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.

PubMed

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

2018-04-19

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.

Porous glass makes effective substrate for ozone-sensing reagent

NASA Technical Reports Server (NTRS)

1965-01-01

Porous-glass substrate is used for absorption of a dye used in measuring the concentration of atmospheric ozone at high altitudes. This measurement is based on the chemiluminescence produced in the reaction between ozone and the dye, rhodamine B. The porous glass provides a large interstitial surface area which promotes this reaction.

Lightning NOx and Impacts on Air Quality

NASA Technical Reports Server (NTRS)

Murray, Lee T.

2016-01-01

Lightning generates relatively large but uncertain quantities of nitrogen oxides, critical precursors for ozone and hydroxyl radical (OH), the primary tropospheric oxidants. Lightning nitrogen oxide strongly influences background ozone and OH due to high ozone production efficiencies in the free troposphere, effecting small but non-negligible contributions to surface pollutant concentrations. Lightning globally contributes 3-4 ppbv of simulated annual-mean policy-relevant background (PRB) surface ozone, comprised of local, regional, and hemispheric components, and up to 18 ppbv during individual events. Feedbacks via methane may counter some of these effects on decadal time scales. Lightning contributes approximately 1 percent to annual-mean surface particulate matter, as a direct precursor and by promoting faster oxidation of other precursors. Lightning also ignites wildfires and contributes to nitrogen deposition. Urban pollution influences lightning itself, with implications for regional lightning-nitrogen oxide production and feedbacks on downwind surface pollution. How lightning emissions will change in a warming world remains uncertain.

The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

NASA Technical Reports Server (NTRS)

Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

2014-01-01

Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate change over Antarctic and the Southern Ocean.

Identification and characterisation of regional ozone episodes in the southwest of the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Domínguez-López, D.; Vaca, F.; Hernández-Ceballos, M. A.; Bolívar, J. P.

2015-02-01

Tropospheric ozone is considered one of the most significant air pollutants due to its negative effects on human health, agricultural crops, ecosystems and climate. The features of the southwest of the Iberian Peninsula (high temperatures and high solar radiation, the presence of the Guadalquivir basin and sources of precursors) favour the occurrence of episodes of high concentrations that cause exceedances of legal thresholds with relative frequency. Despite this, no study examining regional ozone episodes has been carried out in this region until now. In the present work a surface hourly ozone dataset (2003-2006) measured at 11 representative stations located in the southwest of the Iberian Peninsula (western Andalusia) was analysed in order to identify and characterise, for the first time, the regional ozone episodes that occur in this area. Using a statistical criterion, eight regional episodes were identified and analysed. The analysis of synoptic weather patterns revealed that these episodes occur in conjunction with two different synoptic conditions (high surface pressure either close to the British Isles or over the Atlantic Ocean). Both conditions generate weak isobaric surface pressure over the Iberian Peninsula, favouring the establishment of easterly winds at 500 m and the development of winds with two main prevailing directions (southwest-northwest, following the Guadalquivir basin) in the study area. During episodic days ozone follows a similar daily cycle to that observed on non-episode summer days, although the levels reached during the former are higher. In both cases, a direct relationship between the daily ozone cycle and the local wind regimen was not observed. This therefore seems to indicate that the daily cycle followed by ozone is mainly regulated by the precursor emissions produced in the environment, by the temperature changes taking place during the day and by the influence of the lower troposphere during anticyclonic weather conditions.

The influence of changing UVB radiation in near-surface ozone time series

NASA Astrophysics Data System (ADS)

BröNnimann, Stefan; Voigt, Stefan; Wanner, Heinz

2000-04-01

UVB radiation plays an important role in tropospheric photochemistry since it determines the rate of ozone photolysis J(O1D) and subsequent formation of OH radicals. Consequently, changes of UVB radiation, for example due to changes of the stratospheric ozone amount, could alter the concentration of reactive tropospheric gases including ozone. An observation-based attempt is made to quantify the effect of changing UVB radiation on surface ozone peaks on a day-to-day scale using a time series of measurements at a Swiss mountain site. Seven years data of ozone, NO, NOx, and meteorological measurements from Chaumont (1140 m above sea level (asl)), total ozone and UVB measurements from Arosa (1847 m asl), and surface albedo from satellite observations are investigated. The study is restricted to fair weather days with moderately high NOx concentrations. Multiple regression analysis is performed using chemical, meteorological, and UV dependent variables to predict afternoon ozone peaks. From autumn to spring, positive deviations of ozone peaks are clearly connected with positive UVB deviations. The relation is statistically significant only in part of the seasonal data subsets; however, it is consistent with model studies. The estimated net effect on ozone peaks is normally within a range of 4 ppb, a range of about 6 ppb is predicted for large UVB changes. Applying the coefficients for the large interannual variability of the stratospheric ozone layer observed in spring in the last 10 years results in a range of variation of at most 1 to 1.5 ppb for monthly mean ozone peaks. For trends of J(O1D) from 1970 to 1990, a trend bias of surface ozone peaks on polluted fair weather days of less than 0.12 ppb/yr is calculated. Although the numbers are rather small, they may play a role in certain circumstances.

Catalytic ozonation of paracetamol using commercial and Pt-supported nanocomposites of Al2O3: The impact of ultrasound.

PubMed

Ziylan-Yavaş, Asu; Ince, Nilsun H

2018-01-01

The study is the assessment of commercial γ-Al 2 O 3 and its sonolytically modified nanocomposite in catalytic ozonation of paracetamol (PCT), which is an emerging water contaminant and a highly reactive compound with ozone. The results showed that commercial alumina was ineffective regardless of the solution pH, due to the low affinity of the catalyst surface for PCT and the high reactivity of the solute with molecular ozone. The modified catalyst, which was synthesized by decoration of the original surface with nanoparticles of platinum provided considerable improvement in the performance of the catalyst, particularly in mineralization of the target compound. The presence of OH scavenging agents in solution markedly retarded the rate of PCT oxidation and organic carbon decay, to signal the importance of radical-mediated reaction mechanisms on the degradation of the compound. Finally, the attempt to accelerate the reactions by running them in the presence of ultrasound was found inadequate for the early oxidation, but highly adequate for the longer mineralization process. The failure was attributed to the diffusion of a large fraction of ozone into the gaseous cavity bubbles (reduced probability of direct reactions) and the extreme conditions of cavitation collapse that partially damaged the catalyst surface. The success (in mineralization) was explained by the shift of the reaction site from the bulk solution (poor adsorption on catalyst surfaces) to the solid surface and the gaseous cavity bubbles (via enhanced hydrophobicity), both being considerably more active reaction media. Copyright © 2017 Elsevier B.V. All rights reserved.

Climate Response to the Increase in Tropospheric Ozone since Preindustrial Times: A Comparison between Ozone and Equivalent CO2 Forcings

NASA Technical Reports Server (NTRS)

Mickley L. J.; Jacob, D. J.; Field, B. D.; Rind, D.

2004-01-01

We examine the characteristics of the climate response to anthropogenic changes in tropospheric ozone. Using a general circulation model, we have carried out a pair of equilibrium climate simulations with realistic present-day and preindustrial ozone distributions. We find that the instantaneous radiative forcing of 0.49 W m(sup -2) due to the increase in tropospheric ozone since preindustrial times results in an increase in global mean surface temperature of 0.28 C. The increase is nearly 0.4 C in the Northern Hemisphere and about 0.2 C in the Southern Hemisphere. The largest increases (greater than 0.8 C) are downwind of Europe and Asia and over the North American interior in summer. In the lower stratosphere, global mean temperatures decrease by about 0.2 C due to the diminished upward flux of radiation at 9.6 micrometers. The largest stratospheric cooling, up to 1.0 C, occurs over high northern latitudes in winter, with possibly important implications for the formation of polar stratospheric clouds. To identify the characteristics of climate forcing unique to tropospheric ozone, we have conducted two additional climate equilibrium simulations: one in which preindustrial tropospheric ozone concentrations were increased everywhere by 18 ppb, producing the same global radiative forcing as present-day ozone but without the heterogeneity; and one in which CO2 was decreased by 25 ppm relative to present day, with ozone at present-day values, to again produce the same global radiative forcing but with the spectral signature of CO2 rather than ozone. In the first simulation (uniform increase of ozone), the global mean surface temperature increases by 0.25 C, with an interhemispheric difference of only 0.03 C, as compared with nearly 0.2 C for the heterogeneous ozone increase. In the second simulation (equivalent CO2), the global mean surface temperature increases by 0.36 C, 30% higher than the increase from tropospheric ozone. The stronger surface warming from CO2 is in part because CO2 forcing (obscured by water vapor) is shifted relatively poleward where the positive ice-albedo feedback amplifies the climate response and in part because the magnitude of the CO2 forcing in the mid-troposphere is double that of ozone. However, we find that CO2 is far less effective than tropospheric ozone in driving lower stratospheric cooling at high northern latitudes in winter.

An extreme anomaly in stratospheric ozone over Europe in 1940-1942

NASA Astrophysics Data System (ADS)

Brönnimann, S.; Luterbacher, J.; Staehelin, J.; Svendby, T. M.

2004-04-01

Reevaluated historical total ozone data reveal extraordinarily high values over several European sites in 1940-1942, concurrent with extreme climatic anomalies at the Earth's surface. Using historical radiosonde data, reconstructed upper-level fields, and total ozone data from Arosa (Switzerland), Dombås, and Tromsø (Norway), this unusual case of stratosphere-troposphere coupling is analyzed. At Arosa, numerous strong total ozone peaks in all seasons were due to unusually frequent upper troughs over central Europe and related ozone redistribution in the lower stratosphere. At the Norwegian sites, high winter total ozone was most likely caused by major stratospheric warmings in Jan./Feb. 1940, Feb./Mar. 1941, and Feb. 1942. Results demonstrate that the dynamically driven interannual variability of total ozone can be much larger than that estimated based on the past 25-40 years.

Optimal Extraction of Tropospheric Ozone Column by Simultaneous Use of OMI and TES Data and the Surface Temperature

NASA Astrophysics Data System (ADS)

Mobasheri, M. R.; Shirazi, H.

2015-12-01

This article aims to increase the accuracy of Ozone data from tropospheric column (TOC) of the OMI and TES satellite instruments. To validate the estimated amount of satellite data, Ozonesonde data is used. The vertical resolution in both instruments in the tropospheric atmosphere decreases so that the degree of freedom signals (DOFS) on the average for TES is reduced to 2 and for OMI is reduced to1. But this decline in accuracy in estimation of tropospheric ozone is more obvious in urban areas so that estimated ozone in both instruments alone in non-urban areas show a high correlation with Ozonesonde. But in urban areas this correlation is significantly reduced, due to the ozone pre-structures and consequently an increase on surface-level ozone in urban areas. In order to improve the accuracy of satellite data, the average tropospheric ozone data from the two instruments were used. The aim is to increase the vertical resolution of ozone profile and the results clearly indicate an increase in correlations, but nevertheless the satellite data have a positive bias towards the earth data. To reduce the bias, with the solar flux and nitrogen dioxide values and surface temperatures are calculated as factors of ozone production on the earth's surface and formation of mathematical equations based on coefficients for each of the mentioned values and multiplication of these coefficients by satellite data and repeated comparison with the values of Ozonesonde, the results showed that bias in urban areas is greatly reduced.

Surface modification of nitrogen-doped carbon nanotubes by ozone via atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lushington, Andrew; Liu, Jian; Tang, Yongji

The use of ozone as an oxidizing agent for atomic layer deposition (ALD) processes is rapidly growing due to its strong oxidizing capabilities. However, the effect of ozone on nanostructured substrates such as nitrogen-doped multiwalled carbon nanotubes (NCNTs) and pristine multiwalled carbon nanotubes (PCNTs) are not very well understood and may provide an avenue toward functionalizing the carbon nanotube surface prior to deposition. The effects of ALD ozone treatment on NCNTs and PCNTs using 10 wt. % ozone at temperatures of 150, 250, and 300 °C are studied. The effect of ozone pulse time and ALD cycle number on NCNTs and PCNTsmore » was also investigated. Morphological changes to the substrate were observed by scanning electron microscopy and high resolution transmission electron microscopy. Brunauer-Emmett-Teller measurements were also conducted to determine surface area, pore size, and pore size distribution following ozone treatment. The graphitic nature of both NCNTs and PCNTs was determined using Raman analysis while x-ray photoelectron spectroscopy (XPS) was employed to probe the chemical nature of NCNTs. It was found that O{sub 3} attack occurs preferentially to the outermost geometric surface of NCNTs. Our research also revealed that the deleterious effects of ozone are found only on NCNTs while little or no damage occurs on PCNTs. Furthermore, XPS analysis indicated that ALD ozone treatment on NCNTs, at elevated temperatures, results in loss of nitrogen content. Our studies demonstrate that ALD ozone treatment is an effective avenue toward creating low nitrogen content, defect rich substrates for use in electrochemical applications and ALD of various metal/metal oxides.« less

Synoptic and meteorological drivers of extreme ozone concentrations over Europe

NASA Astrophysics Data System (ADS)

Otero, Noelia Felipe; Sillmann, Jana; Schnell, Jordan L.; Rust, Henning W.; Butler, Tim

2016-04-01

The present work assesses the relationship between local and synoptic meteorological conditions and surface ozone concentration over Europe in spring and summer months, during the period 1998-2012 using a new interpolated data set of observed surface ozone concentrations over the European domain. Along with local meteorological conditions, the influence of large-scale atmospheric circulation on surface ozone is addressed through a set of airflow indices computed with a novel implementation of a grid-by-grid weather type classification across Europe. Drivers of surface ozone over the full distribution of maximum daily 8-hour average values are investigated, along with drivers of the extreme high percentiles and exceedances or air quality guideline thresholds. Three different regression techniques are applied: multiple linear regression to assess the drivers of maximum daily ozone, logistic regression to assess the probability of threshold exceedances and quantile regression to estimate the meteorological influence on extreme values, as represented by the 95th percentile. The relative importance of the input parameters (predictors) is assessed by a backward stepwise regression procedure that allows the identification of the most important predictors in each model. Spatial patterns of model performance exhibit distinct variations between regions. The inclusion of the ozone persistence is particularly relevant over Southern Europe. In general, the best model performance is found over Central Europe, where the maximum temperature plays an important role as a driver of maximum daily ozone as well as its extreme values, especially during warmer months.

Foreign and Domestic Contributions to Springtime Ozone Pollution over China

NASA Astrophysics Data System (ADS)

Ni, R.; Lin, J.; Yan, Y.; Lin, W.; Chen, H.

2017-12-01

Ozone is a critical air pollutant that damages human health and vegetation. Previous studies for the United States and Europe have shown large influences of foreign emissions on domestic ozone levels, whereas the relative contributions of foreign versus domestic emissions are much less clear for China. Here, we use a global-regional two-way coupled model system based on GEOS-Chem to quantify the contributions to springtime ozone over China from anthropogenic emissions in major source regions across the globe. Our results indicate considerable influences of foreign anthropogenic pollution on China's ozone pollution. Together, foreign anthropogenic emissions enhance springtime surface ozone over China by 3 12 ppb. Of all ozone over China produced by global anthropogenic emissions, foreign emissions contribute 40% near the surface, and the contribution increases with altitude until a value of 80% in the upper troposphere. Impact from Japan and Korea is 1 2 ppb over east coastal regions, and negligible in inland. Anthropogenic emissions of South and South-East Asia increase ozone over Tibet and the Yunnan-Guizhou Plateau by up to 5 ppb, and their contribution increases with height due to strong vertical transport. Pollution from North America and Europe mainly accompanies strong westerly winds and frequent cyclonic activities that are favorable to long-range transport. European anthropogenic pollution enhances surface ozone by 1 3 ppb over West and North China. Despite a much longer transport distance, the contribution from North America is greater than European contribution due to the nearly doubled amount of anthropogenic NMVOC emissions. The high percentage contribution of foreign anthropogenic emissions to China's ozone pollution can be partly explained by excessive domestic NOx emissions that suppress ozone production efficiency and even destroy ozone. Our study is relevant to Chinese ozone pollution control and global environmental protection collaboration.

Behavior, distribution and variability of surface ozone at an arid region in the south of Iberian Peninsula (Seville, Spain).

PubMed

Adame, José A; Lozano, Antonio; Bolívar, Juan P; De la Morena, Benito A; Contreras, Juan; Godoy, Francisca

2008-01-01

In order to improve our knowledge of the surface ozone in the south of the Iberian Peninsula, annual, monthly, weekly and daily ozone concentrations have been closely monitored in the Seville metropolitan area highlighting those episodes that exceed the European Ozone Directive. A three-year period (2003-2005) and eight ozone stations were used; five of them located in the city's busiest areas and the rest in adjacent zones ( approximately 25km). In addition, the wind regime was also studied in order to understand the main characteristics of the surface atmospheric dynamics. The lowest ozone concentrations 17-33microgm(-3) took place in January while the highest 57-95microgm(-3) occurred in June. The ozone concentration week-weekend differences from May to September indicate that this phenomenon does not affect the ozone stations analysed. Daily cycles show minimum values between 7:00 and 8:00 UTC and maximum at noon, exceeding 90microgm(-3) during summer months. From March to October the ozone concentrations were above the target value for the protection of human health, especially during the summer months, with values up to 30% over the limit. The information threshold has been exceeded at all ozone stations studied but with greater frequency in the stations far from the city centre. In addition, at these latter stations the alert threshold was also exceeded on six occasions. This study in the city of Seville indicates that the high ozone levels are due to local atmospheric effects, mainly since the ozone air masses may undergo recirculation processes. The ozone is transported to the city from the S-SW, having a major impact in the NE areas.

Crystal-face-selective adsorption of Au nanoparticles onto polycrystalline diamond surfaces.

PubMed

Kondo, Takeshi; Aoshima, Shinsuke; Hirata, Kousuke; Honda, Kensuke; Einaga, Yasuaki; Fujishima, Akira; Kawai, Takeshi

2008-07-15

Crystal-face-selective adsorption of Au nanoparticles (AuNPs) was achieved on polycrystalline boron-doped diamond (BDD) surface via the self-assembly method combined with a UV/ozone treatment. To the best of our knowledge, this is the first report of crystal-face-selective adsorption on an inorganic solid surface. Hydrogen-plasma-treated BDD samples and those followed by UV/ozone treatment for 2 min or longer showed almost no adsorption of AuNP after immersion in the AuNP solution prepared by the citrate reduction method. However, the samples treated by UV/ozone for 10 s showed AuNP adsorption on their (111) facets selectively after the immersion. Moreover, the sample treated with UV/ozone for 40-60 s showed AuNP adsorption on the whole surface. These results indicate that the AuNP adsorption behavior can be controlled by UV/ozone treatment time. This phenomenon was highly reproducible and was applied to a two-step adsorption method, where AuNPs from different batches were adsorbed on the (111) and (100) surface in this order. Our findings may be of great value for the fabrication of advanced nanoparticle-based functional materials via bottom-up approaches with simple macroscale procedures.

Eradication of high viable loads of Listeria monocytogenes contaminating food-contact surfaces

PubMed Central

de Candia, Silvia; Morea, Maria; Baruzzi, Federico

2015-01-01

This study demonstrates the efficacy of cold gaseous ozone treatments at low concentrations in the eradication of high Listeria monocytogenes viable cell loads from glass, polypropylene, stainless steel, and expanded polystyrene food-contact surfaces. Using a step by step approach, involving the selection of the most resistant strain-surface combinations, 11 Listeria sp. strains resulted inactivated by a continuous ozone flow at 1.07 mg m-3 after 24 or 48 h of cold incubation, depending on both strain and surface evaluated. Increasing the inoculum level to 9 log CFU coupon-1, the best inactivation rate was obtained after 48 h of treatment at 3.21 mg m-3 ozone concentration when cells were deposited onto stainless steel and expanded polystyrene coupons, resulted the most resistant food-contact surfaces in the previous assays. The addition of naturally contaminated meat extract to a high load of L. monocytogenes LMG 23775 cells, the most resistant strain out of the 11 assayed Listeria sp. strains, led to its complete inactivation after 4 days of treatment. To the best of our knowledge, this is the first report describing the survival of L. monocytogenes and the effect of ozone treatment under cold storage conditions on expanded polystyrene, a commonly used material in food packaging. The results of this study could be useful for reducing pathogen cross-contamination phenomena during cold food storage. PMID:26236306

Stratospheric Ozone Response in Experiments G3 and G4 of the Geoengineering Model Intercomparison Project (GeoMIP)

NASA Technical Reports Server (NTRS)

Pitari, Giovanni; Aquila, Valentina; Kravitz, Ben; Watanabe, Shingo; Tilmes, Simone; Mancini, Eva; DeLuca, Natalia; DiGenova, Glauco

2013-01-01

Geoengineering with stratospheric sulfate aerosols has been proposed as a means of temporarily cooling the planet, alleviating some of the side effects of anthropogenic CO2 emissions. However, one of the known side effects of stratospheric injections of sulfate aerosols is a decrease in stratospheric ozone. Here we show results from two general circulation models and two coupled chemistry climate models that have simulated stratospheric sulfate aerosol geoengineering as part of the Geoengineering Model Intercomparison Project (GeoMIP). Changes in photolysis rates and upwelling of ozone-poor air in the tropics reduce stratospheric ozone, suppression of the NOx cycle increases stratospheric ozone, and an increase in available surfaces for heterogeneous chemistry modulates reductions in ozone. On average, the models show a factor 20-40 increase of the sulfate aerosol surface area density (SAD) at 50 hPa in the tropics with respect to unperturbed background conditions and a factor 3-10 increase at mid-high latitudes. The net effect for a tropical injection rate of 5 Tg SO2 per year is a decrease in globally averaged ozone by 1.1-2.1 DU in the years 2040-2050 for three models which include heterogeneous chemistry on the sulfate aerosol surfaces. GISS-E2-R, a fully coupled general circulation model, performed simulations with no heterogeneous chemistry and a smaller aerosol size; it showed a decrease in ozone by 9.7 DU. After the year 2050, suppression of the NOx cycle becomes more important than destruction of ozone by ClOx, causing an increase in total stratospheric ozone. Contribution of ozone changes in this experiment to radiative forcing is 0.23 W m-2 in GISS-E2-R and less than 0.1 W m-2 in the other three models. Polar ozone depletion, due to enhanced formation of both sulfate aerosol SAD and polar stratospheric clouds, results in an average 5 percent increase in calculated surface UV-B.

The Transition of Atmospheric Infrared Sounder Total Ozone Products to Operations

NASA Technical Reports Server (NTRS)

Berndt, E. B.; Zavodsky, B. T.; Jedlovec, G. J.

2014-01-01

The National Aeronautics and Space Administration Short-term Prediction Research and Transition Center (NASA SPoRT) has transitioned a total column ozone product from the Atmospheric Infrared Sounder (AIRS) retrievals to the Weather Prediction Center and Ocean Prediction Center. The total column ozone product is used to diagnose regions of warm, dry, ozone-rich, stratospheric air capable of descending to the surface to create high-impact non-convective winds. Over the past year, forecasters have analyzed the Red, Green, Blue (RGB) Air Mass imagery in conjunction with the AIRS total column ozone to aid high wind forecasts. One of the limitations of the total ozone product is that it is difficult for forecasters to determine whether elevated ozone concentrations are related to stratospheric air or climatologically high values of ozone in certain regions. During the summer of 2013, SPoRT created an AIRS ozone anomaly product which calculates the percent of normal ozone based on a global stratospheric ozone mean climatology. With the knowledge that ozone values 125 percent of normal and greater typically represent stratospheric air; the anomaly product can be used with the total column ozone product to confirm regions of stratospheric air. This paper describes the generation of these products along with forecaster feedback concerning the use of the AIRS ozone products in conjunction with the RGB Air Mass product to access the utility and transition of the products.

Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: the influence of zeolite chemical surface characteristics.

PubMed

Alejandro, Serguei; Valdés, Héctor; Manéro, Marie-Hélène; Zaror, Claudio A

2014-06-15

In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity. Copyright © 2014 Elsevier B.V. All rights reserved.

Variability in Tropospheric Ozone over China Derived from Assimilated GOME-2 Ozone Profiles

NASA Astrophysics Data System (ADS)

van Peet, J. C. A.; van der A, R. J.; Kelder, H. M.

2016-08-01

A tropospheric ozone dataset is derived from assimilated GOME-2 ozone profiles for 2008. Ozone profiles are retrieved with the OPERA algorithm, using the optimal estimation method. The retrievals are done on a spatial resolution of 160×160 km on 16 layers ranging from the surface up to 0.01 hPa. By using the averaging kernels in the data assimilation, the algorithm maintains the high resolution vertical structures of the model, while being constrained by observations with a lower vertical resolution.

Comparing and evaluating model estimates of background ozone in surface air over North America

NASA Astrophysics Data System (ADS)

Oberman, J.; Fiore, A. M.; Lin, M.; Zhang, L.; Jacob, D. J.; Naik, V.; Horowitz, L. W.

2011-12-01

Tropospheric ozone adversely affects human health and vegetation, and is thus a criteria pollutant regulated by the U.S. Environmental Protection Agency (EPA) under the National Ambient Air Quality Standard (NAAQS). Ozone is produced in the atmosphere via photo-oxidation of volatile organic compounds (VOCs) and carbon monoxide (CO) in the presence of nitrogen oxides (NOx). The present EPA approach considers health risks associated with exposure to ozone enhancement above the policy-relevant background (PRB), which is currently defined as the surface concentration of ozone that would exist without North American anthropogenic emissions. PRB thus includes production by natural precursors, production by precursors emitted on foreign continents, and transport of stratospheric ozone into surface air. As PRB is not an observable quantity, it must be estimated using numerical models. We compare PRB estimates for the year 2006 from the GFDL Atmospheric Model 3 (AM3) chemistry-climate model (CCM) and the GEOS-Chem (GC) chemical transport model (CTM). We evaluate the skill of the models in reproducing total surface ozone observed at the U.S. Clean Air Status and Trends Network (CASTNet), dividing the stations into low-elevation (< 1.5 km in altitude, primarily eastern) and high-elevation (> 1.5 km in altitude, all western) subgroups. At the low-elevation sites AM3 estimates of PRB (38±9 ppbv in spring, 27±9 ppbv in summer) are higher than GC (27±7 ppbv in spring, 21±8 ppbv in summer) in both seasons. Analysis at these sites is complicated by a positive bias in AM3 total ozone with respect to the observed total ozone, the source of which is yet unclear. At high-elevation sites, AM3 PRB is higher in the spring (47±8 ppbv) than in the summer (33±8 ppbv). In contrast, GC simulates little seasonal variation at high elevation sites (39±5 ppbv in spring vs. 38±7 ppbv in summer). Seasonal average total ozone at these sites was within 4 ppbv of the observations for both spring and summer in both models. The high elevation springtime maximum in PRB predicted by AM3 likely reflects stronger exchange between the surface and the free troposphere relative to GC, including a larger influence of stratospheric ozone. Higher summertime PRB in GC may be associated with differences in how the models treat the lightning NOx source (~10 times higher in GC over the Southwest U.S.). Biomass burning emissions (treated differently in the two models) contribute to episodic PRB enhancements in AM3 over the Midwest and East Coast. We conclude that further multi-model studies, including additional models, could provide the EPA with a more robust estimate of PRB, particularly if designed to isolate the relative roles of emissions, chemistry and transport, and evaluated with observation-based constraints wherever possible.

Arctic Haze: Natural or Pollution

DTIC Science & Technology

1978-08-01

rn wavelength, rs0o; precipitable water in g cm - , iv; Angstrom ~wavelength coefficient, a and column ozone in column cm (STP), 03. Left - Barrow...maximum of total ozone in the Arctic, but there is evidence at the same time of a depletion of surface ozone . 6. Spring is the time when the sun’s...chemical reactions due to high ozone concentrations. d. Association with dynamics of stratospheric warmings (that occur in mid-winter and spring). 6. Cosmic

Inquiry Based Projects Using Student Ozone Measurements and the Status of Using Plants as Bio-Indicators

NASA Astrophysics Data System (ADS)

Ladd, I. H.; Fishman, J.; Pippin, M.; Sachs, S.; Skelly, J.; Chappelka, A.; Neufeld, H.; Burkey, K.

2006-05-01

Students around the world work cooperatively with their teachers and the scientific research community measuring local surface ozone levels using a hand-held optical scanner and ozone sensitive chemical strips. Through the GLOBE (Global Learning and Observations to Benefit the Environment) Program, students measuring local ozone levels are connected with the chemistry of the air they breathe and how human activity impacts air quality. Educational tools have been developed and correlated with the National Science and Mathematics Standards to facilitate integrating the study of surface ozone with core curriculum. Ozone air pollution has been identified as the major pollutant causing foliar injury to plants when they are exposed to concentrations of surface ozone. The inclusion of native and agricultural plants with measuring surface ozone provides an Earth system approach to understanding surface ozone. An implementation guide for investigating ozone induced foliar injury has been developed and field tested. The guide, Using Sensitive Plants as Bio-Indicators of Ozone Pollution, provides: the background information and protocol for implementing an "Ozone Garden" with native and agricultural plants; and, a unique opportunity to involve students in a project that will develop and increase their awareness of surface ozone air pollution and its impact on plants.

Relationship between high daily erythemal UV doses, total ozone, surface albedo and cloudiness: An analysis of 30 years of data from Switzerland and Austria

NASA Astrophysics Data System (ADS)

Rieder, H. E.; Staehelin, J.; Weihs, P.; Vuilleumier, L.; Maeder, J. A.; Holawe, F.; Blumthaler, M.; Lindfors, A.; Peter, T.; Simic, S.; Spichtinger, P.; Wagner, J. E.; Walker, D.; Ribatet, M.

2010-10-01

This work investigates the occurrence frequency of days with high erythemal UV doses at three stations in Switzerland and Austria (Davos, Hoher Sonnblick and Vienna) for the time period 1974-2003. While several earlier studies have reported on increases in erythemal UV dose up to 10% during the last decades, this study focuses on days with high erythemal UV dose, which is defined as a daily dose at least 15% higher than for 1950s clear-sky conditions (which represent preindustrial conditions with respect to anthropogenic chlorine). Furthermore, the influence of low column ozone, clear-sky/partly cloudy conditions and surface albedo on UV irradiance has been analyzed on annual and seasonal basis. The results of this study show that in the Central Alpine Region the number of days with high UV dose increased strongly in the early 1990s. A large fraction of all days with high UV dose occurring in the period 1974-2003 was found especially during the years 1994-2003, namely 40% at Davos, 54% at Hoher Sonnblick and 65% at Vienna. The importance of total ozone, clear-sky/partly cloudy conditions and surface albedo (e.g. in dependence of snow cover) varies strongly among the seasons. However, overall the interplay of low total ozone and clear-sky/partly cloudy conditions led to the largest fraction of days showing high erythemal UV dose. Furthermore, an analysis of the synoptic weather situation showed that days with high erythemal UV dose, low total ozone and high relative sunshine duration occur at all three stations more frequently during situations with low pressure gradients or southerly advection.

Measurements of upward turbulent ozone fluxes above a subalpine spruce-fir forest

Treesearch

Karl Zeller; Ted Hehn

1996-01-01

High rural concentrations of ozone (O3) are thought to be either stratospheric in origin, advected from upwind urban sources, or photochemically generated locally as a result of natural trace gas emissions. Ozone is known to be transported vertically downward from the above-canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral...

The Global Structure of UTLS Ozone in GEOS-5: A Multi-Year Assimilation of EOS Aura Data

NASA Technical Reports Server (NTRS)

Wargan, Krzysztof; Pawson, Steven; Olsen, Mark A.; Witte, Jacquelyn C.; Douglass, Anne R.; Ziemke, Jerald R.; Strahan, Susan E.; Nielsen, J. Eric

2015-01-01

Eight years of ozone measurements retrieved from the Ozone Monitoring Instrument (OMI) and the Microwave Limb Sounder, both on the EOS Aura satellite, have been assimilated into the Goddard Earth Observing System version 5 (GEOS-5) data assimilation system. This study thoroughly evaluates this assimilated product, highlighting its potential for science. The impact of observations on the GEOS-5 system is explored by examining the spatial distribution of the observation-minus-forecast statistics. Independent data are used for product validation. The correlation coefficient of the lower-stratospheric ozone column with ozonesondes is 0.99 and the bias is 0.5%, indicating the success of the assimilation in reproducing the ozone variability in that layer. The upper-tropospheric assimilated ozone column is about 10% lower than the ozonesonde column but the correlation is still high (0.87). The assimilation is shown to realistically capture the sharp cross-tropopause gradient in ozone mixing ratio. Occurrence of transport-driven low ozone laminae in the assimilation system is similar to that obtained from the High Resolution Dynamics Limb Sounder (HIRDLS) above the 400 K potential temperature surface but the assimilation produces fewer laminae than seen by HIRDLS below that surface. Although the assimilation produces 5 - 8 fewer occurrences per day (up to approximately 20%) during the three years of HIRDLS data, the interannual variability is captured correctly. This data-driven assimilated product is complementary to ozone fields generated from chemistry and transport models. Applications include study of the radiative forcing by ozone and tracer transport near the tropopause.

Urban and Rural Ozone Collect over Lusaka (Zambia, 15.5 S, 28 E) during SAFARI-2000 (September 2000)

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Witte, Jacquelyn C.; Freiman, M. Tai; Phalane, N. Agnes; Coetzee, Gert J. R.

2002-01-01

In early September, throughout south central Africa, seasonal clearing of dry vegetation and the production of charcoal for cooking leads to intense smoke haze and ozone formation. Ozone soundings made over Lusaka in early September 2000 recorded layers of high ozone (greater than 125 ppbv at 5 km) during two stagnant periods, broken by a frontal passage that reduced boundary layer ozone by 30%. During the 6-day measurement period, surface ozone concentrations ranged from 50-95 ppbv and integrated tropospheric ozone from the soundings was 39-54 Dobson Units (note 1.3 km elevation at the launch site). A stable layer of high ozone at 2-5 km was advected from rural burning regions in western Zambia and neighboring countries, making Lusaka a collection point for transboundary pollution. This is confirmed by trajectories that show ozone leaving Angola, Namibia, Botswana and South Africa before heading toward the Indian Ocean and returning to Lusaka via Mozambique and Zimbabwe. Ozone in the mixed layer at Lusaka is heavily influenced by local sources.

Long-term trends of surface ozone and its influencing factors at the Mt Waliguan GAW station, China - Part 1: Overall trends and characteristics

NASA Astrophysics Data System (ADS)

Xu, Wanyun; Lin, Weili; Xu, Xiaobin; Tang, Jie; Huang, Jianqing; Wu, Hao; Zhang, Xiaochun

2016-05-01

Tropospheric ozone is an important atmospheric oxidant, greenhouse gas and atmospheric pollutant at the same time. The oxidation capacity of the atmosphere, climate, human and vegetation health can be impacted by the increase of the ozone level. Therefore, long-term determination of trends of baseline ozone is highly needed information for environmental and climate change assessment. So far, studies on the long-term trends of ozone at representative sites are mainly available for European and North American sites. Similar studies are lacking for China and many other developing countries. Measurements of surface ozone were carried out at a baseline Global Atmospheric Watch (GAW) station in the north-eastern Tibetan Plateau region (Mt Waliguan, 36°17' N, 100°54' E, 3816 m a.s.l.) for the period of 1994 to 2013. To uncover the variation characteristics, long-term trends and influencing factors of surface ozone at this remote site in western China, a two-part study has been carried out, with this part focusing on the overall characteristics of diurnal, seasonal and long-term variations and the trends of surface ozone. To obtain reliable ozone trends, we performed the Mann-Kendall trend test and the Hilbert-Huang transform (HHT) analysis on the ozone data. Our results confirm that the mountain-valley breeze plays an important role in the diurnal cycle of surface ozone at Waliguan, resulting in higher ozone values during the night and lower ones during the day, as was previously reported. Systematic diurnal and seasonal variations were found in mountain-valley breezes at the site, which were used in defining season-dependent daytime and nighttime periods for trend calculations. Significant positive trends in surface ozone were detected for both daytime (0.24 ± 0.16 ppbv year-1) and nighttime (0.28 ± 0.17 ppbv year-1). The largest nighttime increasing rate occurred in autumn (0.29 ± 0.11 ppbv year-1), followed by spring (0.24 ± 0.12 ppbv year-1), summer (0.22 ± 0.20 ppbv year-1) and winter (0.13 ± 0.10 ppbv year-1), respectively. The HHT spectral analysis identified four different stages with different positive trends, with the largest increase occurring around May 2000 and October 2010. The HHT results suggest that there were 2-4a, 7a and 11a periodicities in the time series of surface ozone at Waliguan. The results of this study can be used for assessments of climate and environment change and in the validation of chemistry-climate models.

Impacts of Ozone-vegetation Interactions and Biogeochemical Feedbacks on Atmospheric Composition and Air Quality Under Climate Change

NASA Astrophysics Data System (ADS)

Sadeke, M.; Tai, A. P. K.; Lombardozzi, D.; Val Martin, M.

2015-12-01

Surface ozone pollution is one of the major environmental concerns due to its damaging effects on human and vegetation. One of the largest uncertainties of future surface ozone prediction comes from its interaction with vegetation under a changing climate. Ozone can be modulated by vegetation through, e.g., biogenic emissions, dry deposition and transpiration. These processes are in turn affected by chronic exposure to ozone via lowered photosynthesis rate and stomatal conductance. Both ozone and vegetation growth are expected to be altered by climate change. To better understand these climate-ozone-vegetation interactions and possible feedbacks on ozone itself via vegetation, we implement an online ozone-vegetation scheme [Lombardozzi et al., 2015] into the Community Earth System Model (CESM) with active atmospheric chemistry, climate and land surface components. Previous overestimation of surface ozone in eastern US, Canada and Europe is shown to be reduced by >8 ppb, reflecting improved model-observation comparison. Simulated surface ozone is lower by 3.7 ppb on average globally. Such reductions (and improvements) in simulated ozone are caused mainly by lower isoprene emission arising from reduced leaf area index in response to chronic ozone exposure. Effects via transpiration are also potentially significant but require better characterization. Such findings suggest that ozone-vegetation interaction may substantially alter future ozone simulations, especially under changing climate and ambient CO2 levels, which would further modulate ozone-vegetation interactions. Inclusion of such interactions in Earth system models is thus necessary to give more realistic estimation and prediction of surface ozone. This is crucial for better policy formulation regarding air quality, land use and climate change mitigation. Reference list: Lombardozzi, D., et al. "The Influence of Chronic Ozone Exposure on Global Carbon and Water Cycles." Journal of Climate 28.1 (2015): 292-305.

Use of North American and European air quality networks to evaluate global chemistry-climate modeling of surface ozone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnell, J. L.; Prather, M. J.; Josse, B.

Here we test the current generation of global chemistry–climate models in their ability to simulate observed, present-day surface ozone. Models are evaluated against hourly surface ozone from 4217 stations in North America and Europe that are averaged over 1° × 1° grid cells, allowing commensurate model–measurement comparison. Models are generally biased high during all hours of the day and in all regions. Most models simulate the shape of regional summertime diurnal and annual cycles well, correctly matching the timing of hourly (~ 15:00 local time (LT)) and monthly (mid-June) peak surface ozone abundance. The amplitude of these cycles is lessmore » successfully matched. The observed summertime diurnal range (~ 25 ppb) is underestimated in all regions by about 7 ppb, and the observed seasonal range (~ 21 ppb) is underestimated by about 5 ppb except in the most polluted regions, where it is overestimated by about 5 ppb. The models generally match the pattern of the observed summertime ozone enhancement, but they overestimate its magnitude in most regions. Most models capture the observed distribution of extreme episode sizes, correctly showing that about 80 % of individual extreme events occur in large-scale, multi-day episodes of more than 100 grid cells. The models also match the observed linear relationship between episode size and a measure of episode intensity, which shows increases in ozone abundance by up to 6 ppb for larger-sized episodes. Lastly, we conclude that the skill of the models evaluated here provides confidence in their projections of future surface ozone.« less

Use of North American and European air quality networks to evaluate global chemistry-climate modeling of surface ozone

DOE PAGES

Schnell, J. L.; Prather, M. J.; Josse, B.; ...

2015-09-25

Here we test the current generation of global chemistry–climate models in their ability to simulate observed, present-day surface ozone. Models are evaluated against hourly surface ozone from 4217 stations in North America and Europe that are averaged over 1° × 1° grid cells, allowing commensurate model–measurement comparison. Models are generally biased high during all hours of the day and in all regions. Most models simulate the shape of regional summertime diurnal and annual cycles well, correctly matching the timing of hourly (~ 15:00 local time (LT)) and monthly (mid-June) peak surface ozone abundance. The amplitude of these cycles is lessmore » successfully matched. The observed summertime diurnal range (~ 25 ppb) is underestimated in all regions by about 7 ppb, and the observed seasonal range (~ 21 ppb) is underestimated by about 5 ppb except in the most polluted regions, where it is overestimated by about 5 ppb. The models generally match the pattern of the observed summertime ozone enhancement, but they overestimate its magnitude in most regions. Most models capture the observed distribution of extreme episode sizes, correctly showing that about 80 % of individual extreme events occur in large-scale, multi-day episodes of more than 100 grid cells. The models also match the observed linear relationship between episode size and a measure of episode intensity, which shows increases in ozone abundance by up to 6 ppb for larger-sized episodes. Lastly, we conclude that the skill of the models evaluated here provides confidence in their projections of future surface ozone.« less

Sensitivity analysis of surface ozone to emission controls in Beijing and its neighboring area during the 2008 Olympic Games.

PubMed

Gao, Yi; Zhang, Meigen

2012-01-01

The regional air quality modeling system RAMS (regional atmospheric modeling system)-CMAQ (community multi-scale air quality modeling system) is applied to analyze temporal and spatial variations in surface ozone concentration over Beijing and its surrounding region from July to October 2008. Comparison of simulated and observed meteorological elements and concentration of nitrogen oxides (NOx) and ozone at one urban site and three rural sites during Olympic Games show that model can generally reproduce the main observed feature of wind, temperature and ozone, but NOx concentration is overestimated. Although ozone concentration decreased during Olympics, high ozone episodes occurred on 24 July and 24 August with concentration of 360 and 245 microg/m3 at Aoyuncun site, respectively. The analysis of sensitive test, with and without emission controls, shows that emission controls could reduce ozone concentration in the afternoon when ozone concentration was highest but increase it at night and in the morning. The evolution of the weather system during the ozone episodes (24 July and 24 August) indicates that hot and dry air and a stable weak pressure field intensified the production of ozone and allowed it to accumulate. Process analysis at the urban site and rural site shows that under favorable weather condition on 24 August, horizontal transport was the main contributor of the rural place and the pollution from the higher layer would be transported to the surface layer. On 24 July, as the wind velocity was smaller, the impact of transport on the rural place was not obvious.

Changes in biologically active ultraviolet radiation reaching the Earth's surface.

PubMed

Madronich, S; McKenzie, R L; Björn, L O; Caldwell, M M

1998-10-01

Stratospheric ozone levels are near their lowest point since measurements began, so current ultraviolet-B (UV-B) radiation levels are thought to be close to their maximum. Total stratospheric content of ozone-depleting substances is expected to reach a maximum before the year 2000. All other things being equal, the current ozone losses and related UV-B increases should be close to their maximum. Increases in surface erythemal (sunburning) UV radiation relative to the values in the 1970s are estimated to be: about 7% at Northern Hemisphere mid-latitudes in winter/spring; about 4% at Northern Hemisphere mid-latitudes in summer/fall; about 6% at Southern Hemisphere mid-latitudes on a year-round basis; about 130% in the Antarctic in spring; and about 22% in the Arctic in spring. Reductions in atmospheric ozone are expected to result in higher amounts of UV-B radiation reaching the Earth's surface. The expected correlation between increases in surface UV-B radiation and decreases in overhead ozone has been further demonstrated and quantified by ground-based instruments under a wide range of conditions. Improved measurements of UV-B radiation are now providing better geographical and temporal coverage. Surface UV-B radiation levels are highly variable because of cloud cover, and also because of local effects including pollutants and surface reflections. These factors usually decrease atmospheric transmission and therefore the surface irradiances at UV-B as well as other wavelengths. Occasional cloud-induced increases have also been reported. With a few exceptions, the direct detection of UV-B trends at low- and mid-latitudes remains problematic due to this high natural variability, the relatively small ozone changes, and the practical difficulties of maintaining long-term stability in networks of UV-measuring instruments. Few reliable UV-B radiation measurements are available from pre-ozone-depletion days. Satellite-based observations of atmospheric ozone and clouds are being used, together with models of atmospheric transmission, to provide global coverage and long-term estimates of surface UV-B radiation. Estimates of long-term (1979-1992) trends in zonally averaged UV irradiances that include cloud effects are nearly identical to those for clear-sky estimates, providing evidence that clouds have not influenced the UV-B trends. However, the limitations of satellite-derived UV estimates should be recognized. To assess uncertainties inherent in this approach, additional validations involving comparisons with ground-based observations are required. Direct comparisons of ground-based UV-B radiation measurements between a few mid-latitude sites in the Northern and Southern Hemispheres have shown larger differences than those estimated using satellite data. Ground-based measurements show that summertime erythemal UV irradiances in the Southern Hemisphere exceed those at comparable latitudes of the Northern Hemisphere by up to 40%, whereas corresponding satellite-based estimates yield only 10-15% differences. Atmospheric pollution may be a factor in this discrepancy between ground-based measurements and satellite-derived estimates. UV-B measurements at more sites are required to determine whether the larger observed differences are globally representative. High levels of UV-B radiation continue to be observed in Antarctica during the recurrent spring-time ozone hole. For example, during ozone-hole episodes, measured biologically damaging radiation at Palmer Station, Antarctica (64 degrees S) has been found to approach and occasionally even exceed maximum summer values at San Diego, CA, USA (32 degrees N). Long-term predictions of future UV-B levels are difficult and uncertain. Nevertheless, current best estimates suggest that a slow recovery to pre-ozone depletion levels may be expected during the next half-century. (ABSTRACT TRUNCATED)

Improved functionality of graphene and carbon nanotube hybrid foam architecture by UV-ozone treatment

NASA Astrophysics Data System (ADS)

Wang, Wei; Ruiz, Isaac; Lee, Ilkeun; Zaera, Francisco; Ozkan, Mihrimah; Ozkan, Cengiz S.

2015-04-01

Optimization of the electrode/electrolyte double-layer interface is a key factor for improving electrode performance of aqueous electrolyte based supercapacitors (SCs). Here, we report the improved functionality of carbon materials via a non-invasive, high-throughput, and inexpensive UV generated ozone (UV-ozone) treatment. This process allows precise tuning of the graphene and carbon nanotube hybrid foam (GM) transitionally from ultrahydrophobic to hydrophilic within 60 s. The continuous tuning of surface energy can be controlled by simply varying the UV-ozone exposure time, while the ozone-oxidized carbon nanostructure maintains its integrity. Symmetric SCs based on the UV-ozone treated GM foam demonstrated enhanced rate performance. This technique can be readily applied to other CVD-grown carbonaceous materials by taking advantage of its ease of processing, low cost, scalability, and controllability.Optimization of the electrode/electrolyte double-layer interface is a key factor for improving electrode performance of aqueous electrolyte based supercapacitors (SCs). Here, we report the improved functionality of carbon materials via a non-invasive, high-throughput, and inexpensive UV generated ozone (UV-ozone) treatment. This process allows precise tuning of the graphene and carbon nanotube hybrid foam (GM) transitionally from ultrahydrophobic to hydrophilic within 60 s. The continuous tuning of surface energy can be controlled by simply varying the UV-ozone exposure time, while the ozone-oxidized carbon nanostructure maintains its integrity. Symmetric SCs based on the UV-ozone treated GM foam demonstrated enhanced rate performance. This technique can be readily applied to other CVD-grown carbonaceous materials by taking advantage of its ease of processing, low cost, scalability, and controllability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06795a

New analytical model for the ozone electronic ground state potential surface and accurate ab initio vibrational predictions at high energy range.

PubMed

Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A; Holka, Filip; Szalay, Péter G

2013-10-07

An accurate description of the complicated shape of the potential energy surface (PES) and that of the highly excited vibration states is of crucial importance for various unsolved issues in the spectroscopy and dynamics of ozone and remains a challenge for the theory. In this work a new analytical representation is proposed for the PES of the ground electronic state of the ozone molecule in the range covering the main potential well and the transition state towards the dissociation. This model accounts for particular features specific to the ozone PES for large variations of nuclear displacements along the minimum energy path. The impact of the shape of the PES near the transition state (existence of the "reef structure") on vibration energy levels was studied for the first time. The major purpose of this work was to provide accurate theoretical predictions for ozone vibrational band centres at the energy range near the dissociation threshold, which would be helpful for understanding the very complicated high-resolution spectra and its analyses currently in progress. Extended ab initio electronic structure calculations were carried out enabling the determination of the parameters of a minimum energy path PES model resulting in a new set of theoretical vibrational levels of ozone. A comparison with recent high-resolution spectroscopic data on the vibrational levels gives the root-mean-square deviations below 1 cm(-1) for ozone band centres up to 90% of the dissociation energy. New ab initio vibrational predictions represent a significant improvement with respect to all previously available calculations.

Comparison of methylisoborneol and geosmin abatement in surface water by conventional ozonation and an electro-peroxone process.

PubMed

Yao, Weikun; Qu, Qiangyong; von Gunten, Urs; Chen, Chao; Yu, Gang; Wang, Yujue

2017-01-01

In this study methylisoborneol (MIB) and geosmin abatement in a surface water by conventional ozonation and the electro-peroxone (E-peroxone) process was compared. Batch tests with addition of ozone (O 3 ) stock solutions and semi-batch tests with continuous O 2 /O 3 gas sparging (simulating real ozone contactors) were conducted to investigate O 3 decomposition, •OH production, MIB and geosmin abatement, and bromate formation during the two processes. Results show that with specific ozone doses typically used in routine drinking water treatment (0.5-1.0 mg O 3 /mg dissolved organic carbon (DOC)), conventional ozonation could not adequately abate MIB and geosmin in a surface water. While increasing the specific ozone doses (1.0-2.5 mg O 3 /mg DOC) could enhance MIB and geosmin abatement by conventional ozonation, this approach resulted in significant bromate formation. By installing a carbon-based cathode to electrochemically produce H 2 O 2 from cathodic oxygen reduction, conventional ozonation can be conveniently upgraded to an E-peroxone process. The electro-generated H 2 O 2 considerably enhanced the kinetics and to a lesser extent the yields of hydroxyl radical (•OH) from O 3 decomposition. Consequently, during the E-peroxone process, abatement of MIB and geosmin occurred at much higher rates than during conventional ozonation. In addition, for a given specific ozone dose, the MIB and geosmin abatement efficiencies increased moderately in the E-peroxone (by ∼8-9% and ∼10-25% in the batch and semi-batch tests, respectively) with significantly lower bromate formation compared to conventional ozonation. These results suggest that the E-peroxone process may serve as an attractive backup of conventional ozonation processes during accidental spills or seasonal events such as algal blooms when high ozone doses are required to enhance MIB and geosmin abatement. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surface ozone at the Swiss Alpine site Arosa: the hemispheric background and the influence of large-scale anthropogenic emissions

NASA Astrophysics Data System (ADS)

Pochanart, Pakpong; Akimoto, Hajime; Maksyutov, Shamil; Staehelin, Johannes

An innovative and effective method using isentropic trajectory analysis based on the residence time of air masses over the polluted region of Europe was successfully applied to categorize surface ozone amounts at Arosa, Switzerland during 1996-1997. The "European representative" background ozone seasonal cycle at Arosa is associated with long-range transport of North Atlantic air masses, and displays the spring maximum-summer minimum with an annual average of 35 ppb. The photochemical ozone production due to the intense large-scale anthropogenic emission over Europe is estimated as high as 20 ppb in summer, whereas it is insignificant in winter. European sources contribute an annual net ozone production of 9-12 ppb at Arosa. Comparison with the selected regional representative site in Western Europe shows similar results indicating that the categorized ozone data at Arosa by this technique could be regarded as a representative for northern hemispheric mid-latitudes.

Iron doped fibrous-structured silica nanospheres as efficient catalyst for catalytic ozonation of sulfamethazine.

PubMed

Bai, Zhiyong; Wang, Jianlong; Yang, Qi

2018-04-01

Sulfonamide antibiotics are ubiquitous pollutants in aquatic environments due to their large production and extensive application. In this paper, the iron doped fibrous-structured silica (KCC-1) nanospheres (Fe-KCC-1) was prepared, characterized, and applied as a catalyst for catalytic ozonation of sulfamethazine (SMT). The effects of ozone dosage, catalyst dosage, and initial concentration of SMT were examined. The experimental results showed that Fe-KCC-1 had large surface area (464.56 m2 g -1 ) and iron particles were well dispersed on the catalyst. The catalyst had high catalytic performance especially for the mineralization of SMT, with mineralization ratio of about 40% in a wide pH range. With addition of Fe-KCC-1, the ozone utilization increased nearly two times than single ozonation. The enhancement of SMT degradation was mainly due to the surface reaction, and the increased mineralization of SMT was due to radical mechanism. Fe-KCC-1 was an efficient catalyst for SMT degradation in catalytic ozonation system.

The Total Ozone Series of Arosa: History, Homogenization and new results using statistical extreme value theory

NASA Astrophysics Data System (ADS)

Staehelin, J.; Rieder, H. E.; Maeder, J. A.; Ribatet, M.; Davison, A. C.; Stübi, R.

2009-04-01

Atmospheric ozone protects the biota living at the Earth's surface from harmful solar UV-B and UV-C radiation. The global ozone shield is expected to gradually recover from the anthropogenic disturbance of ozone depleting substances (ODS) in the coming decades. The stratospheric ozone layer at extratropics might significantly increase above the thickness of the chemically undisturbed atmosphere which might enhance ozone concentrations at the tropopause altitude where ozone is an important greenhouse gas. At Arosa, a resort village in the Swiss Alps, total ozone measurements started in 1926 leading to the longest total ozone series of the world. One Fery spectrograph and seven Dobson spectrophotometers were operated at Arosa and the method used to homogenize the series will be presented. Due to its unique length the series allows studying total ozone in the chemically undisturbed as well as in the ODS loaded stratosphere. The series is particularly valuable to study natural variability in the period prior to 1970, when ODS started to affect stratospheric ozone. Concepts developed by extreme value statistics allow objective definitions of "ozone extreme high" and "ozone extreme low" values by fitting the (daily mean) time series using the Generalized Pareto Distribution (GPD). Extreme high ozone events can be attributed to effects of ElNino and/or NAO, whereas in the chemically disturbed stratosphere high frequencies of extreme low total ozone values simultaneously occur with periods of strong polar ozone depletion (identified by statistical modeling with Equivalent Stratospheric Chlorine times Volume of Stratospheric Polar Clouds) and volcanic eruptions (such as El Chichon and Pinatubo).

Inversion structure and winter ozone distribution in the Uintah Basin, Utah, U.S.A.

NASA Astrophysics Data System (ADS)

Lyman, Seth; Tran, Trang

2015-12-01

The Uintah Basin in Utah, U.S.A. experiences high concentrations of ozone during some winters due to strong, multi-day temperature inversions that facilitate the buildup of pollution from local sources, including the oil and gas industry. Together, elevation of monitoring sites and proximity to oil and gas wells explain as much as 90% of spatial variability in surface ozone concentrations during inversion episodes (i.e., R2 = 0.90). Inversion conditions start earlier and last longer at lower elevations, at least in part because lower elevations are more insulated from winds aloft that degrade inversion conditions and dilute produced ozone. Surface air transport under inversions is dominated by light, diurnal upslope-downslope flow that limits net transport distances. Thus, different areas of the Basin are relatively isolated from each other, allowing spatial factors like elevation and proximity to sources to strongly influence ozone concentrations at individual sites.

Development and Performance Evaluation of an Ozone-Contained Ice Making Machine Employing Pressurized Air Tight Containers

NASA Astrophysics Data System (ADS)

Yoshimura, Kenji; Akiyama, Tomoaki; Hirofuji, Yushi; Koyama, Shigeru

Ozone has the capability of sterilization and deodorization due to high oxidation power. It is also effective for the conservation of perishable foods and purification of water. However, ozone has a disadvantage, that is, conservation of ozone is difficult because it reacts to oxygen. Recently, ozone-contained ice is taken attention for the purpose of its conservation. The use of ozone-contained ice seems to keep food fresher when we conserve and transport perishable foods due to the effects of cooling and sterilization of ozone-contained ice. In the present study, we have developed an ozone-contained ice making machine employing pressurized air tight containers with commercially available size. And the performance evaluation of the system is also carried out. Furthermore, we investigated the sterilization effect of ozone-contained ice on conservation of fish. It was seen that ozone-contained ice is effective for sterilization of surface of fish.

The Anatomy of High Levels of Wintertime Photochemical Ozone Production in the Uintah Basin, Utah, 2013

NASA Astrophysics Data System (ADS)

Schnell, R. C.; Oltmans, S. J.; Johnson, B.; Petron, G.; Neely, R. R.

2013-12-01

The Uintah Basin, Utah is ~ 5,000 km2 in size with lower elevations of ~1400 m msl ringed by mountains rising to ~3,000 m. Within this basin are 6,000 gas wells that produced 10 billion m3 of natural gas and 4,000 oil wells that produced ~22 million barrels of oil in 2012. In winter, the confined geography in the basin traps effluents from these fossil fuel extraction activities into a shallow layer (a few 100 meters deep) beneath strong temperature inversions, especially when ample snow cover is present throughout the basin. The temperature inversions isolate the basin from upper level winds that allow for stagnant conditions that may last for a week or more before a frontal system may flush the basin out. The highly reflective snow provides for enhanced photolysis rates that in February are comparable to those in June. In 2013 December snowfall in the Uintah Basin persisted until early March with exceptionally elevated ozone production occurring in four distinct, 10-day periods separated by 2-3 days of near background values following frontal induced washouts of the basins. In one well studied ozone event, background ozone levels of 55 ppb in the basin were measured from the surface to the lower troposphere on January 30, 2013. By February 1, ozone concentrations from the surface to the top of the 180 m deep temperature inversion averaged 100 ppb. By February 6 ozone concentrations were 165 ppb throughout the same layer. From aircraft measurements these ozone concentrations were observed to be fairly well mixed throughout the basin although there were some notable hotspots. Clean-out of ozone and ozone precursors in the Uintah Basin was observed to occur within 4 hours or less as basin air was replaced with air coming in from the west coast and mixing to the surface.

Ozone-mist spray sterilization for pest control in agricultural management

NASA Astrophysics Data System (ADS)

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.

Mixing Heights and Three-Dimensional Ozone Structure Observed by Airborne Lidar During the 2006 Texas Air Quality Study

NASA Astrophysics Data System (ADS)

Hardesty, R. M.; Senff, C. J.; Alvarez, R. J.; Banta, R. M.; Sandberg, S. P.; Weickmann, A. M.; Darby, L. S.

2007-12-01

A new all solid state ozone lidar was deployed on a NOAA Twin Otter to study boundary layer ozone and aerosol, mostly around Houston, during the 2006 Texas Air Quality Study. The new instrument transmits high pulse-rate, low pulse-energy light at 3 wavelengths in the ultraviolet to obtain ozone profiles with 500 m horizontal resolution and 90 m vertical resolution. During the Texas field study, 20 research flights resulted in nearly 70 hours of ozone measurements during the period from August 1 to September 15. Science objectives included characterization of background ozone levels over rural areas near Houston and Dallas and variability and structure of the boundary layer over different surface types, including urban, wooded, and agricultural land surface areas as well as over Galveston Bay and the Gulf of Mexico. A histogram of all boundary layer ozone concentration measurements showed a bimodal distribution with modes at 45 ppb and 70 ppb. The lower mode correlated with southerly flow, when relatively clean air was transported onshore into the Houston area. Segmenting the observations during southerly flow by region, including the Gulf of Mexico, land within about 55 km from the coast, and further inland indicated that background levels increased by about 10 ppb as air was transported onshore. During the latter part of the experiment, as more pollution was imported into the Houston region, background levels rose to nearly 80 ppb in regions N of Houston. Two flights aimed at observing import of ozone into Texas from the east showed that ozone concentrations increased and boundary layer depths deepened upwind of Houston between September 4 and September 8. Background levels rose by more than 10 ppb over this period. In addition to ozone measurements, we also estimated boundary layer height based on maximum gradient in observed backscatter. The technique worked well when the layer topped by the strongest gradient extends down to the surface. Investigation of the correlation between ozone levels and mixing layer heights both within and external to the Houston urban plume showed a variety of relationships, depending on, e.g., wind direction and occurrence of a bay/gulf breeze. On a day-to-day basis, higher ozone levels were weakly correlated with deeper mixing levels - this was likely due to advection of the urban heat island downwind with the high-ozone urban plume.

New Insights on "Next Day" Ozone Increases in the Northeastern U.S. using Continuous Vertical Profiles of Ozone

NASA Astrophysics Data System (ADS)

Sullivan, J. T.; McGee, T. J.; Rabenhorst, S. D.; Delgado, R.; Dreessen, J.; Sumnicht, G. K.; Twigg, L.

2016-12-01

A unique multi-day air quality event occurred throughout the Mid-Atlantic region from June 9-12, 2015. The June event was coupled to the advection of widespread smoke and debris from western Canada throughout the region. Observations indicated that the aged smoke impacted the Planetary Boundary Layer (PBL) and greatly enhanced ozone concentrations at the surface. Many ground sites in the region, particularly in Maryland, recorded 8-hr ozone concentrations that were in exceedance of the 75 ppb EPA National Ambient Air Quality Standard (NAAQS). After the high O3 episode occurred, a nocturnal low-level jet developed throughout the Mid-Atlantic region, which was spatially correlated with next day high O3 at several sites within the New England region. During this event, nearly continuous vertical profiles of ozone are presented at Beltsville, MD from the NASA Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL), which has been developed and validated within the Tropospheric Ozone Lidar Network (TOLNet). Lidar observations reveal a well-mixed polluted PBL, nocturnal residual layer, and subsequent mixing down of the residual layer in the morning. Additional measurements of surface ozone, aerosol lidar profiles, wind profiles, and balloon borne profiles are also presented. Model output and trajectory analyses are also presented to illustrate the complex flow regimes that occurred during the daytime and nighttime to help redistribute the polluted air mass.

Ozone and Ozone By-Products in the Cabins of Commercial Aircraft

PubMed Central

Weisel, Clifford; Weschler, Charles J.; Mohan, Kris; Vallarino, Jose; Spengler, John D.

2013-01-01

The aircraft cabin represents a unique indoor environment due to its high surface-to-volume ratio, high occupant density and the potential for high ozone concentrations at cruising altitudes. Ozone was continuously measured and air was sampled on sorbent traps, targeting carbonyl compounds, on 52 transcontinental U.S. or international flights between 2008 and 2010. The sampling was predominantly on planes that did not have ozone scrubbers (catalytic converters). Peak ozone levels on aircraft without catalytic convertors exceeded 100 ppb, with some flights having periods of more than an hour when the ozone levels were > 75ppb. Ozone was greatly reduced on relatively new aircraft with catalytic convertors, but ozone levels on two flights whose aircraft had older convertors were similar to those on planes without catalytic convertors. Hexanal, heptanal, octanal, nonanal, decanal and 6-methyl-5-hepten-2-one (6-MHO) were detected in the aircraft cabin at sub- to low ppb levels. Linear regression models that included the log transformed mean ozone concentration, percent occupancy and plane type were statistically significant and explained between 18 and 25% of the variance in the mixing ratio of these carbonyls. Occupancy was also a significant factor for 6-MHO, but not the linear aldehydes, consistent with 6-MHO’s formation from the reaction between ozone and squalene, which is present in human skin oils. PMID:23517299

Extreme value modeling for the analysis and prediction of time series of extreme tropospheric ozone levels: a case study.

PubMed

Escarela, Gabriel

2012-06-01

The occurrence of high concentrations of tropospheric ozone is considered as one of the most important issues of air management programs. The prediction of dangerous ozone levels for the public health and the environment, along with the assessment of air quality control programs aimed at reducing their severity, is of considerable interest to the scientific community and to policy makers. The chemical mechanisms of tropospheric ozone formation are complex, and highly variable meteorological conditions contribute additionally to difficulties in accurate study and prediction of high levels of ozone. Statistical methods offer an effective approach to understand the problem and eventually improve the ability to predict maximum levels of ozone. In this paper an extreme value model is developed to study data sets that consist of periodically collected maxima of tropospheric ozone concentrations and meteorological variables. The methods are applied to daily tropospheric ozone maxima in Guadalajara City, Mexico, for the period January 1997 to December 2006. The model adjusts the daily rate of change in ozone for concurrent impacts of seasonality and present and past meteorological conditions, which include surface temperature, wind speed, wind direction, relative humidity, and ozone. The results indicate that trend, annual effects, and key meteorological variables along with some interactions explain the variation in daily ozone maxima. Prediction performance assessments yield reasonably good results.

The characteristics of tropospheric ozone seasonality observed from ozone soundings at Pohang, Korea.

PubMed

Kim, Jae H; Lee, H J; Lee, S H

2006-07-01

This paper presents the first analysis of vertical ozone sounding measurements over Pohang, Korea. The main focus is to analyze the seasonal variation of vertical ozone profiles and determine the mechanisms controlling ozone seasonality. The maxima ozone at the surface and in the free troposphere are observed in May and June, respectively. In comparison with the ozone seasonality at Oki (near sea level) and Happo (altitude of 1840 m) in Japan, which are located at the same latitude as of Pohang, we have found that the time of the ozone maximum at the Japanese sites is always a month earlier than at Pohang. Analysis of the wind flow at the surface shows that the wind shifts from westerly to southerly in May over Japan, but in June over Pohang. However, this wind shift above boundary layer occurs a month later. This wind shift results in significantly smaller amounts of ozone because the southerly wind brings clean wet tropical air. It has been suggested that the spring ozone maximum in the lower troposphere is due to polluted air transported from China. However, an enhanced ozone amount over the free troposphere in June appears to have a different origin. A tongue-like structure in the time-height cross-section of ozone concentrations, which starts from the stratosphere and extends to the middle troposphere, suggests that the ozone enhancement occurs due to a gradual migration of ozone from the stratosphere. The high frequency of dry air with elevated ozone concentrations in the upper troposphere in June suggests that the air is transported from the stratosphere. HYSPLIT trajectory analysis supports the hypothesis that enhanced ozone in the free troposphere is not likely due to transport from sources of anthropogenic activity.

Ozone formation in pulsed SDBD in a wide pressure range

NASA Astrophysics Data System (ADS)

Starikovskiy, Andrey; Nudnova, Maryia; mipt Team

2011-10-01

Ozone concentration in surface anode-directed DBD for wide pressure range (150 - 1300 torr) was experimentally measured. Voltage and pressure effect were investigated. Reduced electric field was measured for anode-directed and cathode-directed SDBD. E/n values in cathode-directed SDBD is higher than in cathode-directed on 50 percent at atmospheric pressure. E/n value increase leads to decrease the rate of oxygen dissociation and Ozone formation at lower pressures. Radiating region thickness of sliding discharge was measured. Typical thickness of radiating zone is 0.4-1.0 mm within pressure range 220-740 torr. It was shown that high-voltage pulsed nanosecond discharge due to high E/n value produces less Ozone with compare to other discharges. Kinetic model was proposed to describe Ozone formation in the pulsed nanosecond SDBD.

A 15-year climatology of wind pattern impacts on surface ozone in Houston, Texas

NASA Astrophysics Data System (ADS)

Souri, Amir Hossein; Choi, Yunsoo; Li, Xiangshang; Kotsakis, Alexander; Jiang, Xun

2016-06-01

Houston is recognized for its large petrochemical industrial facilities providing abundant radicals for tropospheric ozone formation. Fortunately, maximum daily 8-h average (MDA8) surface ozone concentrations have declined in Houston (- 0.6 ± 0.3 ppbv yr- 1) during the summers (i.e., May to September) of 2000 to 2014, possibly due to the reductions in precursor emissions by effective control policies. However, it is also possible that changes in meteorological variables have affected ozone concentrations. This study focused on the impact of long-term wind patterns which have the highest impact on ozone in Houston. The analysis of long-term wind patterns can benefit surface ozone studies by 1) providing wind patterns that distinctly changed ozone levels, 2) investigating the frequency of patterns and the respective changes and 3) estimating ozone trends in specific wind patterns that local emissions are mostly involved, thus separating emissions impacts from meteorology to some extent. To this end, the 900-hPa flow patterns in summers of 2000 to 2014 were clustered in seven classes (C1-C7) by deploying an unsupervised partitioning method. We confirm the characteristics of the clusters from a backward trajectory analysis, monitoring networks, and a regional chemical transport model simulation. The results indicate that Houston has experienced a statistically significant downward trend (- 0.6 ± 0.4 day yr- 1) of the cluster of weak easterly and northeasterly days (C4), when the highest fraction of ozone exceedances (MDA8 > 70 ppbv) occurred. This suggests that the reduction in ozone precursors was not the sole reason for the decrease in ozone exceedance days (- 1.5 ± 0.6 day yr- 1). Further, to examine the efficiency of control policies intended to reduce the amount of ozone, we estimated the trend of MDA8 ozone in C4 and C5 (weak winds) days when local emissions are primarily responsible for high ambient ozone levels. Both C4 and C5 show a large reduction in the 95th percentile and summertime trends mainly due to effective control strategies. Based on the 5th percentile daytime ozone for C1 (strong southeasterly wind) in coastal sites, this study found that the cleanest air masses that Houston received became more polluted during the summer of 2000-2014 by 1-3 ppbv. Though this study focused on Houston, the analysis method presented could generally be used to estimate ozone trends in other regions where surface ozone is dominantly influenced by both wind patterns and local emissions.

Nicotiana tabacum as model for ozone - plant surface reactions

NASA Astrophysics Data System (ADS)

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 difference of ozone measured before and after the plant cuvette was investigated as a function of stomatal opening. Switching from dark to light conditions and thus opening the stomata only a small increase in ozone loss was observed for the Ambalema variety (25%). In the case of the 3H02 variety, a line known to emit almost no diterpenoids, the ozone loss increased by more than 100% when changing from dark to light conditions. It is anticipated that the described effect is of importance also for other plant species emitting low-volatility unsaturated organic compounds (e.g. in form of exudates or resins).

Climatic consequences of observed ozone loss in the 1980s: Relevance to the greenhouse problem

NASA Technical Reports Server (NTRS)

Molnar, G. I.; Ko, M. K. W.; Zhou, S.; Sze, N. D.

1994-01-01

Recently published findings using satellite and ground-based observations indicate a large winter and summertime decrease in the column abundance of ozone at high and middle latitudes during the last decade. Using a simple ozone depletion profile reflecting the observed decrease in ozone column abundance, Ramaswamy et al. (1992) showed that the negative radiative forcing that results from the ozone decrease between 1979 and 1990 approximately balanced the greenhouse climate forcing due to the chlorofluorocarbons emitted during the same period. Here, we extend the forcing analyses by calculating the equilibrium surface temperature response explicitly, using an updated version of the Atmospheric and Environmental Research two-dimensional radiative-dynamical seasonal model. The calculated steady state responses suggest that the surface cooling due to the ozone depletion in the lower stratosphere offsets about 30% of the surface warming due to greenhouse gases emitted during the same decade. The temperature offset is roughly a factor of 2 larger than the corresponding offset obtained from forcing intercomparisons. This result appears to be related to the climate feedback mechanisms operating in the model troposphere, most notably that associated with atmospheric meridional heat transport. Thus a comprehensive assessment of ozone change effects on the predicted greenhouse warming cannot be accomplished based on forcing evaluations alone. Our results also show that calculations adopting a seasonally and latitudinally dependent ozone depletion profile produce a negative forcing about 50% smaller than that calculated for the depletion profile used by Ramaswamy et al. (1992).

Use of North American and European Air Quality Networks to Evaluate Global Chemistry-Climate Modeling of Surface Ozone

NASA Technical Reports Server (NTRS)

Schnell, J. L.; Prather, M. J.; Josse, B.; Naik, V.; Horowitz, L. W.; Cameron-Smith, P.; Bergmann, D.; Zeng, G.; Plummer, D. A.; Sudo, K.;

Shifting seasonal cycles of surface ozone: the role of regional vs. global emission changes

NASA Astrophysics Data System (ADS)

Clifton, O.; Fiore, A. M.; Correa, G. J.; Naik, V.; Horowitz, L. W.

2013-12-01

Surface-level ozone seasonal cycles vary in shape and in magnitude with location. These variations reflect local contributions, whose influence differs each month, from regional anthropogenic and natural precursor emissions, as well as ozone transported from various sources. We focus on two U.S. regions with markedly different seasonal cycles over recent decades: the Northeast and the InterMountain West. In the Northeast, there are peak ozone values in the summer months due to high regional NOx emissions, abundant sunlight and isoprene emissions during this season. The lower NOx emissions in the InterMountain West combined with higher altitude where transported 'background' ozone is larger, leads to a weak spring maximum. Parrish et al. [2013] report a shift in seasonal cycles to earlier months in spring over recent decades at remote sites. We investigate here the role of changing global and regional ozone precursor emissions over the 21st century. With GFDL's fully coupled climate chemistry model CM3, we use selected Representative Concentration Pathways (RCP) scenarios developed for the Coupled Model Intercomparison Project Phase 5 (CMIP5) in support of IPCC AR 5, and several sensitivity simulations, to examine the impacts of regional and global emissions on surface ozone seasonal cycles throughout the 21st century. In RCP8.5, an extreme climate warming scenario, methane doubles from the present to the end of the 21st century, whereas in RCP4.5, a more moderate climate warming scenario, there is a small (~10%) decrease of methane. For RCP8.5, global mean surface temperature increases by 4.5 K, and for RCP4.5, by 1.4 K. In RCP8.5 and RCP4.5, NOx emissions decrease globally by 70.1% and 52.3%, respectively, by the end of the 21st century. These regional NOx reductions shift the ozone maximum in the Northeast from summer to late winter/early spring, resembling the present-day seasonal cycle over the InterMountain West. Over the InterMoutain West, surface ozone also decreases in summer and increases in the late winter/early spring. We further find that in RCP8.5, the end of 21st century seasonal cycles in the Northeast and the InterMountain West increase by more than 5-15 ppb in each month due to the doubling of global methane. Across present-day high-NOx regions at northern mid-latitudes, surface ozone consistently decreases during the summer and fall months as NOx emissions decline globally, but in the RCP8.5 scenario increases during winter and early spring as CH4 rises.

High Background Ozone Events in the Houston-Galveston-Brazoria Area: Effects from Central American Fires

NASA Astrophysics Data System (ADS)

Lei, R.; Wang, S. C.; Yang, S.; Wang, Y.; Talbot, R. W.

2016-12-01

The policy-relevant background (PRB) ozone is defined by the U.S. Environmental Protection Agency (EPA) as the surface ozone mixing ratio that would occur over the U.S. without North American anthropogenic emission influences. PRB ozone over the Houston-Galveston-Brazoria (HGB) area may be affected by foreign sources due to its unique geographical location and meteorology. Our monitoring data revealed several high ozone events over HGB area which might be caused by Central American fire during the years of 2013-2015. To qualify the effects from Central American fire, we estimated the US, Central American and worldwide background over HGB area during those events using the GEOS-Chem global 3-D model. Anomalies in fire emissions leading to high PRB ozone were mapped through spatiotemporal sampling of the Fire INventory from NCAR (FINN) along background trajectories of air masses affecting the HGB area prior to and during the selected high PRB ozone days. Daily HGB PRB ozone estimated by researchers at the Texas Commission on Environmental Quality (TCEQ) was used as the data source to validate model results. Results showed that contribution of emission from Central American to HGB PRB ozone could be tripled during fire events compared to non-impacted fire days. Besides fire emissions from Central American, different types of meteorological events (e.g., cold fronts and thunderstorms) and high local photochemical production (e.g., heat waves and stagnation) are also found associated with high PRB ozone in HGB area during these events. Thus we imply that synthetic contribution from foreign sources and local meteorology to HGB PRB ozone warrants further investigated.

Black sea surface temperature anomaly on 5th August 1998 and the ozone layer thickness

NASA Astrophysics Data System (ADS)

Manev, A.; Palazov, K.; Raykov, St.; Ivanov, V.

2003-04-01

BLACK SEA SURFACE TEMPERATURE ANOMALY ON 5th AUGUST 1998 AND THE OZONE LAYER THICKNESS A. Manev , K. Palazov , St. Raykov, V. Ivanov Solar Terrestrial Influences Laboratory, Bulgarian Academy of Sciences amanev@abv.bg This paper focuses on the peculiarities of the Black Sea surface temperature anomaly on 05.08.1998. Researching the daily temperature changes in a number of control fields in the course of 8-10 years, we have found hidden correlations and anomalous deviations in the sea surface temperatures on a global scale. Research proves the statistical reliability of the temperature anomaly on the entire Black Sea surface registered on 04.-05.08.1998. In the course of six days around these dates the temperatures are up to 2°C higher than the maximum temperatures in this period in the other seven years. A more detailed analysis of the dynamics of the anomaly required the investigation of five Black Sea surface characteristic zones of 75x75 km. The analysis covers the period 20 days - 10 days before and 10 days after the anomaly. Investigations aimed at interpreting the reasons for the anomalous heating of the surface waters. We have tried to analyze the correlation between sea surface temperature and the global ozone above the Black Sea by using simultaneously data from the two satellite systems NOAA and TOMS. Methods of processing and comparing the data from the two satellite systems are described. The correlation coefficients values for the five characteristic zones are very high and close, which proves that the character of the correlation ozone - sea surface temperature is the same for the entire Black Sea surface. Despite the high correlation coefficient, we have proved that causality between the two phenomena at the time of the anomaly does not exit.

[Effects of synoptic type on surface ozone pollution in Beijing].

PubMed

Tang, Gui-qian; Li, Xin; Wang, Xiao-ke; Xin, Jin-yuan; Hu, Bo; Wang, Li-li; Ren, Yu-fen; Wang, Yue-Si

2010-03-01

Ozone (O), influenced by meteorological factors, is a primary gaseous photochemical pollutant during summer to fall in Beijing' s urban ambient. Continuous monitoring during July to September in 2008 was carried out at four sites in Beijing. Analyzed with synoptic type, the results show that the ratios of pre-low cylonic (mainly Mongolia cyclone) and pre-high anticylonic to total weather conditions are about 42% and 20%, illustrating the high-and low-ozone episodes, respectively. At the pre-low cylonic conditions, high temperature, low humidity, mountain and valley winds caused by local circulation induce average hourly maximum ozone concentration (volume fraction) up to 102.2 x 10(-9), negative correlated with atmospheric pressure with a slope of -3.4 x 10(-9) Pa(-1). The time of mountain wind changed to valley wind dominates the diurnal time of maximum ozone, generally around 14:00. At the pre-high anticylonic conditions, low temperature, high humidity and systematic north wind induce average hourly maximum ozone concentration (volume fraction) only 49.3 x 10(-9), the diurnal time of maximum ozone is deferred by continuous north wind till about 16:00. The consistency of photochemical pollution in Beijing region shows that good correlation exists between synoptic type and ozone concentration. Therefore, getting an eye on the structure and evolution of synoptic type is of great significances for forecasting the photochemical pollution.

The numerical modeling the sensitivity of coastal wind and ozone concentration to different SST forcing

NASA Astrophysics Data System (ADS)

Choi, Hyun-Jung; Lee, Hwa Woon; Jeon, Won-Bae; Lee, Soon-Hwan

2012-01-01

This study evaluated an atmospheric and air quality model of the spatial variability in low-level coastal winds and ozone concentration, which are affected by sea surface temperature (SST) forcing with different thermal gradients. Several numerical experiments examined the effect of sea surface SST forcing on the coastal atmosphere and air quality. In this study, the RAMS-CAMx model was used to estimate the sensitivity to two different resolutions of SST forcing during the episode day as well as to simulate the low-level coastal winds and ozone concentration over a complex coastal area. The regional model reproduced the qualitative effect of SST forcing and thermal gradients on the coastal flow. The high-resolution SST derived from NGSST-O (New Generation Sea Surface Temperature Open Ocean) forcing to resolve the warm SST appeared to enhance the mean response of low-level winds to coastal regions. These wind variations have important implications for coastal air quality. A higher ozone concentration was forecasted when SST data with a high resolution was used with the appropriate limitation of temperature, regional wind circulation, vertical mixing height and nocturnal boundary layer (NBL) near coastal areas.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, Glenn Charles

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, andmore » 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 -7, 10 -5, and 10 -5 respectively. To understand how internal surface area influences the equivalent reaction probability of whole carpet, a model of ozone diffusion into and reaction with internal carpet components was developed. This was then used to predict apparent reaction probabilities for carpet. He combines this with a modified model of turbulent mass transfer developed by Liu, et al. to predict deposition rates and indoor ozone concentrations. The model predicts that carpet should have an equivalent reaction probability of about 10 -5, matching laboratory measurements of the reaction probability. For both carpet and duct materials, surfaces become progressively quenched (aging), losing the ability to react or otherwise take up ozone. He evaluated the functional form of aging and find that the reaction probability follows a power function with respect to the cumulative uptake of ozone. To understand ozone aging of surfaces, he developed several mathematical descriptions of aging based on two different mechanisms. The observed functional form of aging is mimicked by a model which describes ozone diffusion with internal reaction in a solid. He shows that the fleecy nature of carpet materials in combination with the model of ozone diffusion below a fiber surface and internal reaction may explain the functional form and the magnitude of power function parameters observed due to ozone interactions with carpet. The ozone induced aldehyde emissions, measured from duct materials, were combined with an indoor air quality model to show that concentrations of aldehydes indoors may approach odorous levels. He shows that ducts are unlikely to be a significant sink for ozone due to the low reaction probability in combination with the short residence time of air in ducts.« less

Heterogeneous nano-Fe/Ca/CaO catalytic ozonation for selective surface hydrophilization of plastics containing brominated and chlorinated flame retardants (B/CFRs): separation from automobile shredder residue by froth flotation.

PubMed

Mallampati, Srinivasa Reddy; Lee, Byoung Ho; Mitoma, Yoshiharu; Simion, Cristian

2017-02-01

One method of weakening the inherently hydrophobic surface of plastics relevant to flotation separation is heterogeneous nano-Fe/Ca/CaO catalytic ozonation. Nano-Fe/Ca/CaO-catalyzed ozonation for 15 min efficiently decreases the surface hydrophobicity of brominated and chlorinated flame retardant (B/CFR)-containing plastics (such as acrylonitrile-butadienestyrene (ABS), high-impact polystyrene (HIPS), and polyvinyl chloride (PVC)) in automobile shredder residue (ASR) to such an extent that their flotation ability is entirely depressed. Such a hydrophilization treatment also stimulates the ABS, HIPS, and PVC surface roughness, wetting of the surface, and the thermodynamic equilibrium conditions at the surface and ultimately changes surface polarity. SEM-EDS, AFM, and XPS analyses of the PVC and ABS surfaces demonstrated a marked decrease in [Cl/Br] and a significant increase in the number of hydrophilic groups, such as C-O, C=O, and (C=O)-O. Under froth flotation conditions at 50 rpm, about 99.5 % of ABS and 99.5 % of HIPS in ASR samples settled out, resulting in a purity of 98 and 98.5 % for ABS and HIPS in ASR samples, respectively. Furthermore, at 150 rpm, we also obtained 100 % PVC separation in the settled fraction, with 98 % purity in ASR. Total recovery of non-B/CFR-containing plastics reached nearly 100 % in the floating fraction. The amount of nano-Fe/Ca/CaO reagent employed during ozonation is very small, and additional removal of surface contaminants from the recycled ASR plastic surfaces by ozonation makes the developed process simpler, greener, and more effective.

Effects of stratospheric ozone recovery on photochemistry and ozone air quality in the troposphere

NASA Astrophysics Data System (ADS)

Zhang, H.; Wu, S.; Huang, Y.; Wang, Y.

2014-04-01

There has been significant stratospheric ozone depletion since the late 1970s due to ozone-depleting substances (ODSs). With the implementation of the Montreal Protocol and its amendments and adjustments, stratospheric ozone is expected to recover towards its pre-1980 level in the coming decades. In this study, we examine the implications of stratospheric ozone recovery for the tropospheric chemistry and ozone air quality with a global chemical transport model (GEOS-Chem). With a full recovery of the stratospheric ozone, the projected increases in ozone column range from 1% over the low latitudes to more than 10% over the polar regions. The sensitivity factor of troposphere ozone photolysis rate, defined as the percentage changes in surface ozone photolysis rate for 1% increase in stratospheric ozone column, shows significant seasonal variation but is always negative with absolute value larger than one. The expected stratospheric ozone recovery is found to affect the tropospheric ozone destruction rates much more than the ozone production rates. Significant decreases in surface ozone photolysis rates due to stratospheric ozone recovery are simulated. The global average tropospheric OH decreases by 1.7%, and the global average lifetime of tropospheric ozone increases by 1.5%. The perturbations to tropospheric ozone and surface ozone show large seasonal and spatial variations. General increases in surface ozone are calculated for each season, with increases by up to 0.8 ppbv in the remote areas. Increases in ozone lifetime by up to 13% are found in the troposphere. The increased lifetimes of tropospheric ozone in response to stratospheric ozone recovery enhance the intercontinental transport of ozone and global pollution, in particular for the summertime. The global background ozone attributable to Asian emissions is calculated to increase by up to 15% or 0.3 ppbv in the Northern Hemisphere in response to the projected stratospheric ozone recovery.

Entrainment of stratospheric air and Asian pollution by the convective boundary layer in the southwestern U.S.

NASA Astrophysics Data System (ADS)

Langford, A. O.; Alvarez, R. J.; Brioude, J.; Fine, R.; Gustin, M. S.; Lin, M. Y.; Marchbanks, R. D.; Pierce, R. B.; Sandberg, S. P.; Senff, C. J.; Weickmann, A. M.; Williams, E. J.

2017-01-01

A series of deep stratospheric intrusions in late May 2013 increased the daily maximum 8 h surface ozone (O3) concentrations to more than 70 parts per billion by volume (ppbv) at rural and urban surface monitors in California and Nevada. This influx of ozone-rich lower stratospheric air and entrained Asian pollution persisted for more than 5 days and contributed to exceedances of the 2008 8 h national ambient air quality standard of 75 ppbv on 21 and 25 May in Clark County, NV. Exceedances would also have occurred on 22 and 23 May had the new standard of 70 ppbv been in effect. In this paper, we examine this episode using lidar measurements from a high-elevation site on Angel Peak, NV, and surface measurements from NOAA, the Clark County, Nevada Department of Air Quality, the Environmental Protection Agency Air Quality System, and the Nevada Rural Ozone Initiative. These measurements, together with analyses from the National Centers for Environmental Prediction/North American Regional Reanalysis; NOAA Geophysical Fluid Dynamics Laboratory AM3 model; NOAA National Environmental Satellite, Data, and Information Service Real-time Air Quality Modeling System; and FLEXPART models, show that the exceedances followed entrainment of 20 to 40 ppbv of lower stratospheric ozone mingled with another 0 to 10 ppbv of ozone transported from Asia by the unusually deep convective boundary layers above the Mojave desert. Our analysis suggests that this vigorous mixing can affect both high and low elevations and help explain the springtime ozone maximum in the southwestern U.S.

Efficacy of chlorinated and ozonated water in reducing Salmonella typhimurium attached to tomato surfaces.

PubMed

Chaidez, Cristobal; Lopez, Javier; Vidales, Juan; Campo, Nohelia Castro-Del

2007-08-01

The purpose of this study was to compare chlorinated and ozonated water in reducing Salmonella typhimurium inoculated onto fresh ripe tomatoes. Surface-inoculated tomatoes were immersed/sprayed with chlorinated (200 mg l(-1)) and ozonated water (1 and 2 mg l(-1)) under 2 and 100 nefelometric turbidity units (NTU). Contact times were 120 and 30 s for immersing and spraying applications, respectively. Immersing in chlorinated water and low turbidity resulted in the most effective application with 3.61 log(10) bacterial reduction, while 1 and 2 mg l(-1) of ozone reduced 2.32 and 2.53 log(10), respectively. High turbidity and chlorine reduced the bacterial counts by 3.39 log(10), while 1 and 2 mg l(-1) of ozonated water and low turbidity reduced the bacteria by 1.48 and 1.92 log(10), respectively. Spraying chlorinated water reduced bacteria by 3 log(10), and ozonated water at 1 and 2 mg l(-1) reduced counts by 1.84 and 2.40 log(10), respectively. No statistical differences were found between chlorine and ozone (2 mg l(-1)) during spraying applications (p < 0.05). The use of ozonated water both in immersing and spraying applications is suggested when water turbidity remains low.

The impact of synoptic weather on UK surface ozone and implications for premature mortality

NASA Astrophysics Data System (ADS)

Pope, R. J.; Butt, E. W.; Chipperfield, M. P.; Doherty, R. M.; Fenech, S.; Schmidt, A.; Arnold, S. R.; Savage, N. H.

2016-12-01

Air pollutants, such as ozone, have adverse impacts on human health and cause, for example, respiratory and cardiovascular problems. In the United Kingdom (UK), peak surface ozone concentrations typically occur in the spring and summer and are controlled by emission of precursor gases, tropospheric chemistry and local meteorology which can be influenced by large-scale synoptic weather regimes. In this study we composite surface and satellite observations of summer-time (April to September) ozone under different UK atmospheric circulation patterns, as defined by the Lamb weather types. Anticyclonic conditions and easterly flows are shown to significantly enhance ozone concentrations over the UK relative to summer-time average values. Anticyclonic stability and light winds aid the trapping of ozone and its precursor gases near the surface. Easterly flows (NE, E, SE) transport ozone and precursor gases from polluted regions in continental Europe (e.g. the Benelux region) to the UK. Cyclonic conditions and westerly flows, associated with unstable weather, transport ozone from the UK mainland, replacing it with clean maritime (North Atlantic) air masses. Increased cloud cover also likely decrease ozone production rates. We show that the UK Met Office regional air quality model successfully reproduces UK summer-time ozone concentrations and ozone enhancements under anticyclonic and south-easterly conditions for the summer of 2006. By using established ozone exposure-health burden metrics, anticyclonic and easterly condition enhanced surface ozone concentrations pose the greatest public health risk.

Surface ozone in the Southern Hemisphere: 20 years of data from a site with a unique setting in El Tololo, Chile

NASA Astrophysics Data System (ADS)

Anet, Julien G.; Steinbacher, Martin; Gallardo, Laura; Velásquez Álvarez, Patricio A.; Emmenegger, Lukas; Buchmann, Brigitte

2017-05-01

The knowledge of surface ozone mole fractions and their global distribution is of utmost importance due to the impact of ozone on human health and ecosystems and the central role of ozone in controlling the oxidation capacity of the troposphere. The availability of long-term ozone records is far better in the Northern than in the Southern Hemisphere, and recent analyses of the seven accessible records in the Southern Hemisphere have shown inconclusive trends. Since late 1995, surface ozone is measured in situ at "El Tololo", a high-altitude (2200 m a.s.l.) and pristine station in Chile (30° S, 71° W). The dataset has been recently fully quality controlled and reprocessed. This study presents the observed ozone trends and annual cycles and identifies key processes driving these patterns. From 1995 to 2010, an overall positive trend of ˜ 0.7 ppb decade-1 is found. Strongest trends per season are observed in March and April. Highest mole fractions are observed in late spring (October) and show a strong correlation with ozone transported from the stratosphere down into the troposphere, as simulated with a model. Over the 20 years of observations, the springtime ozone maximum has shifted to earlier times in the year, which, again, is strongly correlated with a temporal shift in the occurrence of the maximum of simulated stratospheric ozone transport at the site. We conclude that background ozone at El Tololo is mainly driven by stratospheric intrusions rather than photochemical production from anthropogenic and biogenic precursors. The major footprint of the sampled air masses is located over the Pacific Ocean. Therefore, due to the negligible influence of local processes, the ozone record also allows studying the influence of El Niño and La Niña episodes on background ozone levels in South America. In agreement with previous studies, we find that, during La Niña conditions, ozone mole fractions reach higher levels than during El Niño conditions.

Ensemble simulations of the role of the stratosphere in the attribution of northern extratropical tropospheric ozone variability

NASA Astrophysics Data System (ADS)

Hess, P.; Kinnison, D.; Tang, Q.

2015-03-01

Despite the need to understand the impact of changes in emissions and climate on tropospheric ozone, the attribution of tropospheric interannual ozone variability to specific processes has proven difficult. Here, we analyze the stratospheric contribution to tropospheric ozone variability and trends from 1953 to 2005 in the Northern Hemisphere (NH) mid-latitudes using four ensemble simulations of the free running (FR) Whole Atmosphere Community Climate Model (WACCM). The simulations are externally forced with observed time-varying (1) sea-surface temperatures (SSTs), (2) greenhouse gases (GHGs), (3) ozone depleting substances (ODS), (4) quasi-biennial oscillation (QBO), (5) solar variability (SV) and (6) stratospheric sulfate surface area density (SAD). A detailed representation of stratospheric chemistry is simulated, including the ozone loss due to volcanic eruptions and polar stratospheric clouds. In the troposphere, ozone production is represented by CH4-NOx smog chemistry, where surface chemical emissions remain interannually constant. Despite the simplicity of its tropospheric chemistry, at many NH measurement locations, the interannual ozone variability in the FR WACCM simulations is significantly correlated with the measured interannual variability. This suggests the importance of the external forcing applied in these simulations in driving interannual ozone variability. The variability and trend in the simulated 1953-2005 tropospheric ozone from 30 to 90° N at background surface measurement sites, 500 hPa measurement sites and in the area average are largely explained on interannual timescales by changes in the 30-90° N area averaged flux of ozone across the 100 hPa surface and changes in tropospheric methane concentrations. The average sensitivity of tropospheric ozone to methane (percent change in ozone to a percent change in methane) from 30 to 90° N is 0.17 at 500 hPa and 0.21 at the surface; the average sensitivity of tropospheric ozone to the 100 hPa ozone flux (percent change in ozone to a percent change in the ozone flux) from 30 to 90° N is 0.19 at 500 hPa and 0.11 at the surface. The 30-90° N simulated downward residual velocity at 100 hPa increased by 15% between 1953 and 2005. However, the impact of this on the 30-90° N 100 hPa ozone flux is modulated by the long-term changes in stratospheric ozone. The ozone flux decreases from 1965 to 1990 due to stratospheric ozone depletion, but increases again by approximately 7% from 1990 to 2005. The first empirical orthogonal function of interannual ozone variability explains from 40% (at the surface) to over 80% (at 150 hPa) of the simulated ozone interannual variability from 30 to 90° N. This identified mode of ozone variability shows strong stratosphere-troposphere coupling, demonstrating the importance of the stratosphere in an attribution of tropospheric ozone variability. The simulations, with no change in emissions, capture almost 50% of the measured ozone change during the 1990s at a variety of locations. This suggests that a large portion of the measured change is not due to changes in emissions, but can be traced to changes in large-scale modes of ozone variability. This emphasizes the difficulty in the attribution of ozone changes, and the importance of natural variability in understanding the trends and variability of ozone. We find little relation between the El Niño-Southern Oscillation (ENSO) index and large-scale tropospheric ozone variability over the long-term record.

Advanced oxidation-based treatment of furniture industry wastewater.

PubMed

Tichonovas, Martynas; Krugly, Edvinas; Grybauskas, Arturas; Jankūnaitė, Dalia; Račys, Viktoras; Martuzevičius, Dainius

2017-07-16

The paper presents a study on the treatment of the furniture industry wastewater in a bench scale advanced oxidation reactor. The researched technology utilized a simultaneous application of ozone, ultraviolet radiation and surface-immobilized TiO 2 nanoparticle catalyst. Various combinations of processes were tested, including photolysis, photocatalysis, ozonation, catalytic ozonation, photolytic ozonation and photocatalytic ozonation were tested against the efficiency of degradation. The efficiency of the processes was primarily characterized by the total organic carbon (TOC) analysis, indicating the remaining organic material in the wastewater after the treatment, while the toxicity changes in wastewater were researched by Daphnia magna toxicity tests. Photocatalytic ozonation was confirmed as the most effective combination of processes (99.3% of TOC reduction during 180 min of treatment), also being the most energy efficient (4.49-7.83 MJ/g). Photocatalytic ozonation and photolytic ozonation remained efficient across a wide range of pH (3-9), but the pH was an important factor in photocatalysis. The toxicity of wastewater depended on the duration of the treatment: half treated water was highly toxic, while fully treated water did not possess any toxicity. Our results indicate that photocatalytic ozonation has a high potential for the upscaling and application in industrial settings.

A Comparative Study on Ozone Photochemical Formation in the Megacities of Tianjin and Shanghai, China

NASA Astrophysics Data System (ADS)

Ran, L.; Zhao, C.; Xu, W.; Geng, F.; Lu, X.; Han, M.; Lin, W.; Xu, X.

2011-12-01

As one of the most widespread and stubborn environmental issues, the ozone problem has been of particular concern for many years, given the potential adverse effects of high ozone concentrations on public health and agricultural productivity. In the past decades, rapid urbanization and industrialization have given rise to a significant increase in ozone precursor emissions in many regions of China, especially in the densely populated megacities. Due to the highly nonlinear impacts of ozone precursors including nitrogen oxides (NOx) and various volatile organic compounds (VOCs) on ozone photochemistry, formation of ozone affected by different precursor emission patterns in those megacities has exhibited different characteristics. A comparative analysis of ozone photochemical production in the megacities of Tianjin and Shanghai has thus been carried out, using the data sets of surface ozone and its precursors measured respectively at an urban and a suburban site of the two megacities during the summertime. Observation-based analysis indicated an elevated ozone daily peak under photochemistry dominant conditions from the urban center to the suburb in both regions, nevertheless bearing different reasons. Ozone production was generally sensitive to VOCs in the Tianjin region, leading to a relatively higher level of ozone in the suburb where reactive VOCs were abundantly released from a number of industrial facilities, whereas a sensitivity of ozone production to NOx was found in Shanghai. The high level of NOx emitted mainly by motor vehicles in urban Shanghai largely inhibited ozone formation and resulted in a much more rapid decrease in ozone concentrations after reaching the daily maximum around midday compared with the other three areas. Ozone pollution in the megacity of Tianjin was more representative of the regional condition, implying that combined efforts would be needed to bring the ozone problem under control within this region. Improved understanding of ozone formation in the two megacities would be quite imperative and critical to provide a solid scientific basis for designing effective ozone control strategies.

Radiative effects due to North American anthropogenic and lightning emissions: Global and regional modeling

NASA Astrophysics Data System (ADS)

Martini, Matus Novak

We analyze the contribution of North American (NA) lightning and anthropogenic emissions to summertime ozone concentrations, radiative forcing, and exports from North America using the global University of Maryland chemistry transport model (UMD-CTM) and the regional scale Weather Research and Forecasting model with chemistry (WRF-Chem). Lightning NO contributes by 15--20 ppbv to upper tropospheric ozone concentrations over the United States with the effects of NA lightning on ozone seen as far east as North Africa and Europe. Using the UMD-CTM, we compare changes in surface and column ozone amounts due to the NOx State Implementation Plan (SIP) Call with the natural variability in ozone due to changes in meteorology and lightning. Comparing early summer 2004 with 2002, surface ozone decreased by up to 5 ppbv due to the NO x SIP Call while changes in meteorology and lightning resulted in a 0.3--1.4 ppbv increase in surface ozone. Ozone column variability was driven primarily by changes in lightning NO emissions, especially over the North Atlantic. As part of our WRF-Chem analysis, we modify the radiation schemes to use model-calculated ozone (interactive ozone) instead of climatological ozone profiles and conduct multiple 4-day simulations of July 2007. We found that interactive ozone increased the outgoing longwave radiation (OLR) by 3 W m-2 decreasing the bias with respect to remotely sensed OLR. The improvement is due to a high bias in the climatological ozone profiles. The interactive ozone had a small impact on mean upper troposphere temperature (-0.15°C). The UMD-CTM simulations indicate that NA anthropogenic emissions are responsible for more ozone export but less ozone radiative forcing than lightning NO emissions. Over the North Atlantic, NA anthropogenic emissions contributed 0.15--0.30 W m-2 to the net downward radiative flux at the tropopause while NA lightning contributed 0.30--0.50 W m-2. The ozone export from anthropogenic emissions was almost twice as large as that from lightning emissions. The WRF-Chem simulations show that the export of reactive nitrogen was 23%--28% of the boundary layer emissions and 26%--38% of the total emissions including lightning NO.

Source apportionment of surface ozone in the Yangtze River Delta, China in the summer of 2013

NASA Astrophysics Data System (ADS)

Li, L.; An, J. Y.; Shi, Y. Y.; Zhou, M.; Yan, R. S.; Huang, C.; Wang, H. L.; Lou, S. R.; Wang, Q.; Lu, Q.; Wu, J.

2016-11-01

We applied ozone source apportionment technology (OSAT) with tagged tracers coupled within the Comprehensive Air Quality Model with Extensions (CAMx) to study the region and source category contribution to surface ozone in the Yangtze River Delta area in summer of 2013. Results indicate that the daytime ozone concentrations in the YRD region are influenced by emissions both locally, regionally and super-regionally. At urban Shanghai, Hangzhou and Suzhou receptors, the ozone formation is mainly VOC-limited, precursor emissions form Zhejiang province dominate their O3 concentrations. At the junction area among two provinces and Shanghai city, the ozone is usually influenced by all the three areas. The daily max O3 at the Dianshan Lake in July are contributed by Zhejiang (48.5%), Jiangsu (11.7%), Anhui (11.6%) and Shanghai (7.4%), long-range transport constitutes around 20.9%. At Chongming site, the BVOC emissions rate is higher than urban region. Regional contribution results show that Shanghai constitutes 15.6%, Jiangsu contributes 16.2% and Zhejiang accounts for 25.5% of the daily max O3. The analysis of the source category contribution to high ozone in the Yangtze River Delta region indicates that the most significant anthropogenic emission source sectors contributing to O3 pollution include industry, vehicle exhaust, although the effects vary with source sector and selected pollution episodes. Emissions of NOx and VOCs emitted from the fuel combustion of industrial boilers and kilns, together with VOCs emissions from industrial process contribute a lot to the high concentrations in urban Hangzhou, Suzhou and Shanghai. The contribution from regional elevated power plants cannot be neglected, especially to Dianshan Lake. Fugitive emissions of volatile pollution sources also have certain contribution to regional O3. These results indicate that the regional collaboration is of most importance to reduce ambient ozone pollution, particularly during high ozone episodes.

Physics of Fresh Produce Safety: Role of Diffusion and Tissue Reaction in Sanitization of Leafy Green Vegetables with Liquid and Gaseous Ozone-Based Sanitizers.

PubMed

Shynkaryk, Mykola V; Pyatkovskyy, Taras; Mohamed, Hussein M; Yousef, Ahmed E; Sastry, Sudhir K

2015-12-01

Produce safety has received much recent attention, with the emphasis being largely on discovery of how microbes invade produce. However, the sanitization operation deserves more attention than it has received. The ability of a sanitizer to reach the site of pathogens is a fundamental prerequisite for efficacy. This work addresses the transport processes of ozone (gaseous and liquid) sanitizer for decontamination of leafy greens. The liquid sanitizer was ineffective against Escherichia coli K-12 in situations where air bubbles may be trapped within cavities. A model was developed for diffusion of sanitizer into the interior of produce. The reaction rate of ozone with the surface of a lettuce leaf was determined experimentally and was used in a numerical simulation to evaluate ozone concentrations within the produce and to determine the time required to reach different locations. For aqueous ozone, the penetration depth was limited to several millimeters by ozone self-decomposition due to the significant time required for diffusion. In contrast, gaseous sanitizer was able to reach a depth of 100 mm in several minutes without depletion in the absence of reaction with surfaces. However, when the ozone gas reacted with the produce surface, gas concentration was significantly affected. Simulation data were validated experimentally by measuring ozone concentrations at the bottom of a cylinder made of lettuce leaf. The microbiological test confirmed the relationship between ozone transport, its self-decomposition, reaction with surrounding materials, and the degree of inactivation of E. coli K-12. Our study shows that decontamination of fresh produce, through direct contact with the sanitizer, is more feasible with gaseous than with aqueous sanitizers. Therefore, sanitization during a high-speed washing process is effective only for decontaminating the wash water.

Characteristics of ozone vertical profile observed in the boundary layer around Beijing in autumn.

PubMed

Ma, Zhiqiang; Zhang, Xiaoling; Xu, Jing; Zhao, Xiujuan; Meng, Wei

2011-01-01

In the autumn of 2008, the vertical profiles of ozone and meteorological parameters in the low troposphere (0-1000 m) were observed at two sites around Beijing, specifically urban Nanjiao and rural Shangdianzi. At night and early morning, the lower troposphere divided into two stratified layers due to temperature inversion. Ozone in the lower layer showed a large gradient due to the titration of NO. Air flow from the southwest brought ozone-rich air to Beijing, and the ozone profiles were marked by a continuous increase in the residual layer at night. The accumulated ozone in the upper layer played an important role in the next day's surface peak ozone concentration, and caused a rapid increase in surface ozone in the morning. Wind direction shear and wind speed shear exhibited different influences on ozone profiles and resulted in different surface ozone concentrations in Beijing.

Characterization of surface dielectric barrier discharge influenced by intermediate frequency for ozone production

NASA Astrophysics Data System (ADS)

Abdelaziz, Ayman A.; Ishijima, Tatsuo; Seto, Takafumi; Osawa, Naoki; Wedaa, Hassan; Otani, Yoshio

2016-06-01

The aim of this study is to investigate the effect of the intermediate frequency (1-10 kHz) of the sinusoidal driving voltage on the characteristics of a developed surface dielectric barrier discharge (SDBD)-based reactor having spikes on its discharge electrode. Moreover, its influence on the production of ozone and nitrogen oxide byproducts is evaluated. The results show that SDBD is operated in the filamentary mode at all the frequencies. Nevertheless, the pulses of the discharge current at high frequencies are much denser and have higher amplitudes than those at low frequencies. The analysis of the power consumed in the reactor shows that a small portion of the input power is dissipated in the dielectric material of SDBD source, whereas the major part of the power is consumed in the plasma discharge. The results of the ozone production show that higher frequencies have a slightly adverse effect on the ozone production at relatively high energy density values, where the ozone concentration is slightly decreased when the frequency is increased at the same energy density. The temperature of the discharge channels and gas is not a crucial factor for the decomposition of ozone in this reactor, while the results of the measurements of nitrogen oxides characteristics indicate that the formation of NO and NO2 has a significant adverse effect on the production efficiency of ozone due to their oxidation to another nitrogen oxides and their catalytic effect.

Application of OMI Observations to a Space-Based Indicator of NOx and VOC Controls on Surface Ozone Formation

NASA Technical Reports Server (NTRS)

Duncan, Bryan N.; Yoshida, Yasuko; Olson, Jennifer R.; Sillman, Sanford; Martin, Randall V.; Lamsal, Lok; Hu, Yongtao; Pickering, Kenneth E.; Retscher, Christian; Allen, Dale J.;

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

NASA Astrophysics Data System (ADS)

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.

Ozone reaction with interior building materials: Influence of diurnal ozone variation, temperature and humidity

NASA Astrophysics Data System (ADS)

Rim, Donghyun; Gall, Elliott T.; Maddalena, Randy L.; Nazaroff, William W.

2016-01-01

Elevated tropospheric ozone concentrations are associated with increased morbidity and mortality. Indoor ozone chemistry affects human exposure to ozone and reaction products that also may adversely affect health and comfort. Reactive uptake of ozone has been characterized for many building materials; however, scant information is available on how diurnal variation of ambient ozone influences ozone reaction with indoor surfaces. The primary objective of this study is to investigate ozone-surface reactions in response to a diurnally varying ozone exposure for three common building materials: ceiling tile, painted drywall, and carpet tile. A secondary objective is to examine the effects of air temperature and humidity. A third goal is to explore how conditioning of materials in an occupied office building might influence subsequent ozone-surface reactions. Experiments were performed at bench-scale with inlet ozone concentrations varied to simulate daytime (ozone elevated) and nighttime (ozone-free in these experiments) periods. To simulate office conditions, experiments were conducted at two temperatures (22 °C and 28 °C) and three relative humidity values (25%, 50%, 75%). Effects of indoor surface exposures were examined by placing material samples in an occupied office and repeating bench-scale characterization after exposure periods of 1 and 2 months. Deposition velocities were observed to be highest during the initial hour of ozone exposure with slow decrease in the subsequent hours of simulated daytime conditions. Daily-average ozone reaction probabilities for fresh materials are in the respective ranges of (1.7-2.7) × 10-5, (2.8-4.7) × 10-5, and (3.0-4.5) × 10-5 for ceiling tile, painted drywall, and carpet tile. The reaction probability decreases by 7%-47% across the three test materials after two 8-h periods of ozone exposure. Measurements with the samples from an occupied office reveal that deposition velocity can decrease or increase with time. Influence of temperature and humidity on ozone-surface reactivity was not strong.

Urban and Rural Ozone Pollution Over Lusaka (Zambia, 15.5S, 25E) During SAFARI-2000 (September 2000)

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Herman, J. R.; Witte, J. C.; Phahlane, A.; Coetzee, G. J. R.; Mukula, C.; Hudson, R. D.; Frolov, A. D.; Bhartia, P. K. (Technical Monitor)

2001-01-01

In early September, throughout south central Africa, seasonal clearing of dry vegetation and the production of charcoal for cooking leads to intense smoke haze and ozone formation. Ozone soundings made over Lusaka during a six-day period in early September 2000 recorded layers of high ozone (greater than 125 ppbv at 5 km) during two stagnant periods, interspersed by a frontal passage that reduced boundary layer ozone by 30 percent. Smoke aerosol column variations aloft and total ozone were monitored by a sun photometer. During the 6-day measurement period, surface ozone concentrations ranged from 50-95 ppbv and integrated tropospheric ozone from the soundings was 39- 54 Dobson Units (note 1.3 km elevation at the launch site). High ozone concentrations above the mixed and inversion layers were advected from rural burning regions in western Zambia where SAFARI aircraft and ground-based instruments observed intense biomass fires and elevated aerosol and trace gas amounts. TOMS tropospheric ozone and smoke aerosols products show the distribution of biomass burning and associated pollution throughout southern Africa in September 2000. Animations of satellite images and trajectories confirm pollutant recirculation over south central African fires, exit of ozone from Mozambique and Tanzania to the Indian Ocean and the characteristic buildup of tropospheric ozone over the Atlantic from western African outflow.

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

PubMed

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.

Influence of the coating level on the heterogeneous ozonolysis kinetics and product yields of chlorpyrifos ethyl adsorbed on sand particles.

PubMed

El Masri, Ahmad; Laversin, Hélène; Chakir, Abdelkhaleq; Roth, Estelle

2016-12-01

Heterogeneous oxidation of chlorpyrifos ethyl (CLP) coated sand particles by gaseous ozone was studied. Mono-size sand was coated with CLP at different coating levels between 10 and 100 μg g -1 and exposed to ozone. Results were analyzed thanks to Gas Surface Reaction and Surface Layer Reaction Models. Kinetic parameters derived from these models were analyzed and led to several conclusions. The equilibrium constant of O 3 between the gas phase and the CLP-coated sand was independent on the sand contamination level. Ozone seems to have similar affinity for coated or uncoated sand surface. Meanwhile, the kinetic parameters decreased with an increasing coating level. Chlorpyrifos Oxon, (CLPO) has been identified and quantified as an ozonolysis product. The product yield of CLPO remains constant (53 ± 10%) for the different coating level. The key parameter influencing the CLP reactivity towards ozone was the CLP-coating level. This dependence had a great influence on the lifetime of the CLP coated on sand particles, with respect to ozone, which could reach several years at high contamination level. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of Day and Nighttime Lower Tropospheric Ozone from Air Quality Models using TES and Ozonesondes

NASA Astrophysics Data System (ADS)

Osterman, G. B.; Neu, J. L.; Eldering, A.; Pinder, R. W.; Tang, Y.; McQueen, J.

2012-12-01

At night, ozone can be transported long distances above the surface inversion layer without chemical destruction or deposition. As the boundary layer breaks up in the morning, this nocturnal ozone can be mixed down to the surface and rapidly increase ozone concentrations at a rate that can rival chemical ozone production. Most regional scale models that are used for air quality forecasts and ozone source attribution do not adequately capture nighttime ozone concentrations and transport. We combine ozone profile data from the NASA Earth Observing System (EOS) Tropospheric Emission Spectrometer (TES) and other sensors, ozonesonde data collected during the INTEX Ozonesonde Network Study (IONS), EPA AirNow ground station ozone data, the Community Multi-Scale Air Quality (CMAQ) model, and the National Air Quality Forecast Capability (NAQFC) model to examine air quality events during August 2006. We present both aggregated statistics and case-study analyses that assess the relationship between the models' ability to reproduce surface air quality events and their ability to capture the vertical distribution of ozone both during the day and at night. We perform the comparisons looking at the geospatial dependence in the differences between the measurements and models under different surface ozone conditions.

Development of a comprehensive air quality modeling framework for a coastal urban airshed in south Texas

NASA Astrophysics Data System (ADS)

Farooqui, Mohmmed Zuber

Tropospheric ozone is one of the major air pollution problems affecting urban areas of United States as well as other countries in the world. Analysis of surface observed ozone levels in south and central Texas revealed several days exceeding 8-hour average ozone National Ambient of Air Quality Standards (NAAQS) over the past decade. Two major high ozone episodes were identified during September of 1999 and 2002. A photochemical modeling framework for the high ozone episodes in 1999 and 2002 were developed for the Corpus Christi urban airshed. The photochemical model was evaluated as per U.S. Environmental Protection Agency (EPA) recommended statistical methods and the models performed within the limits set by EPA. An emission impact assessment of various sources within the urban airshed was conducted using the modeling framework. It was noted that by nudging MM5 with surface observed meteorological parameters and sea-surface temperature, the coastal meteorological predictions improved. Consequently, refined meteorology helped the photochemical model to better predict peak ozone levels in urban airsheds along the coastal margins of Texas including in Corpus Christi. The emissions assessment analysis revealed that Austin and San Antonio areas were significantly affected by on-road mobile emissions from light-duty gasoline and heavy-duty diesel vehicles. The urban areas of San Antonio, Austin, and Victoria areas were estimated to be NOx sensitive. Victoria was heavily influenced by point sources in the region while Corpus Christi was influenced by both point and non-road mobile sources and was identified to be sensitive to VOC emissions. A rise in atmospheric temperature due to climate change potentially increase ozone exceedances and the peak ozone levels within the study region and this will be a major concern for air quality planners. This study noted that any future increase in ambient temperature would result in a significant increase in the urban and regional ozone levels within the modeling domain and it would also enhance the transported levels of ozone across the region. Overall, the photochemical modeling framework helped in evaluating the impact of various parameters affecting ozone air quality; and, it has the potential to be a tool for policy-makers to develop effective emissions control strategies under various regulatory and climate conditions.

Spectroscopic and solubility characteristics of oxidized soots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chughtai, A.R.; Jassim, J.A.; Peterson, J.H.

1991-01-01

Spectroscopic and solubility studies of reaction products of soot (black carbon) with O{sub 3}, NO{sub 2}/N{sub 2}O{sub 4}, and SO{sub 2} have revealed a relationship between reactivity and product solubility and structure. A remarkably high solubility of ozonated n-hexane soot has its origin in the formation of anhydride and lactone surface structures and their subsequent hydrolysis to carboxylic acid species. Calculations indicate that the rate of surface carboxylation of 0.1-{mu}m diameter spheroidal soot particles, in the presence of 50 ppbv ozone at ambient temperature, is such that solubilization may occur within a 30-minute time frame. Measurements on ambient air aerosolmore » samples in metropolitan Denver are consistent with these observations and demonstrate the high reactivity of soot with ozone even at very low levels in natural systems.« less

Reactive nitrogen partitioning and its relationship to winter ozone events in Utah

NASA Astrophysics Data System (ADS)

Wild, R. J.; Edwards, P. M.; Bates, T. S.; Cohen, R. C.; de Gouw, J. A.; Dubé, W. P.; Gilman, J. B.; Holloway, J.; Kercher, J.; Koss, A.; Lee, L.; Lerner, B.; McLaren, R.; Quinn, P. K.; Roberts, J. M.; Stutz, J.; Thornton, J. A.; Veres, P. R.; Warneke, C.; Williams, E.; Young, C. J.; Yuan, B.; Brown, S. S.

2015-08-01

High wintertime ozone levels have been observed in the Uintah Basin, Utah, a sparsely populated rural region with intensive oil and gas operations. The reactive nitrogen budget plays an important role in tropospheric ozone formation. Measurements were taken during three field campaigns in the winters of 2012, 2013, and 2014, which experienced varying climatic conditions. Average concentrations of ozone and total reactive nitrogen were observed to be 2.5 times higher in 2013 than 2012, with 2014 an intermediate year in most respects. However, photochemically active NOx(NO+NO2), remained remarkably similar all three years. Roughly half of the more oxidized forms of nitrogen were composed of nitric acid in 2013, with nighttime nitric acid formation through heterogeneous uptake of N2O5 contributing approximately 6 times more than daytime formation. The nighttime N2O5 lifetime between the high-ozone year 2013 and the low-ozone year 2012 is lower by a factor 2.6, and much of this is due to higher aerosol surface area in the high ozone year of 2013. A box-model simulation supports the importance of nighttime chemistry on the reactive nitrogen budget, showing a large sensitivity of NOx and ozone concentrations to nighttime processes.

Membrane contactor/separator for an advanced ozone membrane reactor for treatment of recalcitrant organic pollutants in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, Wai Kit, E-mail: kekyeung@ust.hk; Joueet, Justine; Heng, Samuel

An advanced ozone membrane reactor that synergistically combines membrane distributor for ozone gas, membrane contactor for pollutant adsorption and reaction, and membrane separator for clean water production is described. The membrane reactor represents an order of magnitude improvement over traditional semibatch reactor design and is capable of complete conversion of recalcitrant endocrine disrupting compounds (EDCs) in water at less than three minutes residence time. Coating the membrane contactor with alumina and hydrotalcite (Mg/Al=3) adsorbs and traps the organics in the reaction zone resulting in 30% increase of total organic carbon (TOC) removal. Large surface area coating that diffuses surface chargesmore » from adsorbed polar organic molecules is preferred as it reduces membrane polarization that is detrimental to separation. - Graphical abstract: Advanced ozone membrane reactor synergistically combines membrane distributor for ozone, membrane contactor for sorption and reaction and membrane separator for clean water production to achieve an order of magnitude enhancement in treatment performance compared to traditional ozone reactor. Highlights: Black-Right-Pointing-Pointer Novel reactor using membranes for ozone distributor, reaction contactor and water separator. Black-Right-Pointing-Pointer Designed to achieve an order of magnitude enhancement over traditional reactor. Black-Right-Pointing-Pointer Al{sub 2}O{sub 3} and hydrotalcite coatings capture and trap pollutants giving additional 30% TOC removal. Black-Right-Pointing-Pointer High surface area coating prevents polarization and improves membrane separation and life.« less

Intense Electrochemical Oxidation on Graphitized Carbon Electrodes in the Presence of Ozone

NASA Astrophysics Data System (ADS)

Klochikhin, V. L.; Potapova, G. F.; Putilov, A. V.

2018-06-01

A new intense oxidation process for water treatment in which oxidation with ozone is coupled to electrochemical processes is described, and the results from its application to water purification are presented along with the discussion of its practical implementation. The use of graphitized carbon materials for this process is explained and tested experimentally. The use of glassy carbon for the anode enables us to achieve very high (up to 25 vol %) concentrations of ozone in the generated ozone-oxygen mixture. The material used for the cathode—graphitized carbon cloth (GCC) reinforced with Ni allows different electrocatalytic processes to proceed on its developed surface, and combines the high sorption capacity of this cathode and potentialcontrolled selectivity of cathodic electrochemical processes.

New Tether Ozonesonde System Developed for Uintah Basin Ozone Study in February, 2012

NASA Astrophysics Data System (ADS)

Johnson, B. J.; Cullis, P.; Wendell, J.; Hall, E.; Jordan, A.; Albee, R.; Schnell, R. C.

2012-12-01

NOAA/ESRL/GMD participated in the February, 2012 UINTAH basin air quality campaign to measure ozone concentrations from surface to 300 meters above ground level. The study region, southwest of Vernal, Utah, is an active oil and gas production and exploration area. During the previous winter in 2011, an air quality study led by state and local agencies and Utah State University measured very high ozone at several sites, exceeding 140 ppbv centered near Ouray, Utah under shallow boundary layer with surface snow-cover conditions. The high ozone conditions never developed during the 2012 campaign. The weather remained dry and warm with typical ozone mixing rations ranging from 20 to 60 ppbv. In order to provide near continuous ozone profiles without consuming a balloon and ozonesonde for each sounding, a tether system was developed by the Global Monitoring Division based upon a motorized deep sea fishing rod and reel with 50 pound line. The lightweight system was shown to be rugged and reliable and capable of conducting an ascending and descending profile to 300 m within 90 minutes. Communication software and data loggers continuously monitor the radiosonde pressure to control the ascent/descent rates and altitude. The system can operate unmanned as it will ascend, descend and hold an altitude as controlled from a laptop computer located up to 30 m distant.

An Analytical Investigation of Ozone Episodes in Bangu, Rio de Janeiro.

PubMed

Geraldino, Claudio Gabriel Pinheiro; Martins, Eduardo Monteiro; da Silva, Cleyton Martins; Arbilla, Graciela

2017-05-01

This study investigated the potential factors that contribute to frequent high levels of ozone as well as ozone episodes in Bangu, one of the most critical areas in the city of Rio de Janeiro regarding ozone levels. For 74 days in a two-year period (10.3%), the national air quality standard was exceeded. For the same period, a total of 378 days (51.8%) had ozone concentrations that were between 80 and 160 µg m -3 . A statistical analysis of pollutant concentrations and meteorological data as well as a kinetic and mechanistic analysis of VOC reactivity showed that the high ozone concentrations did not seem to be closely related to local emissions but, rather, were related to pollutant transport and triggered by photochemical activity. The mountains in the southern and northern part of the district contribute to the increase of surface temperatures and the accumulation of pollutants. The VOC/NO x ratios corresponded to a VOC-limited process.

Modeling winter ozone episodes near oil and natural gas fields in Wyoming

NASA Astrophysics Data System (ADS)

Wu, Yuling; Rappenglück, Bernhard; Pour-Biazar, Arastoo; Field, Robert A.; Soltis, Jeff

2017-04-01

Wintertime ozone episodes have been reported in the oil and natural gas (O&NG) producing fields in Uintah Basin, Utah and the Upper Green River Basin (UGRB) in Wyoming in recent years. High concentrations of ozone precursors facilitated by favorable meteorological conditions, including low wind and shallow boundary layer (BL), were found in these episodes, although the exact roles of these precursor species in different O&NG fields are to be determined. Meanwhile, snow cover is also found to play an important role in these winter ozone episodes as the cold snow covered surface enhances the inversion, further limits the BL and the high snow albedo greatly boosts photolysis reactions that are closely related to ozone chemistry. In this study, we utilize model simulation to explore the role of chemical compositions, in terms of different VOC groups and NOx, and that of the enhanced photolysis due to snow cover in the UGRB ozone episodes in the late winter of 2011.

Photochemical modeling and analysis of meteorological parameters during ozone episodes in Kaohsiung, Taiwan

NASA Astrophysics Data System (ADS)

Chen, K. S.; Ho, Y. T.; Lai, C. H.; Chou, Youn-Min

The events of high ozone concentrations and meteorological conditions covering the Kaohsiung metropolitan area were investigated based on data analysis and model simulation. A photochemical grid model was employed to analyze two ozone episodes in autumn (2000) and winter (2001) seasons, each covering three consecutive days (or 72 h) in the Kaohsiung City. The potential influence of the initial and boundary conditions on model performance was assessed. Model performance can be improved by separately considering the daytime and nighttime ozone concentrations on the lateral boundary conditions of the model domain. The sensitivity analyses of ozone concentrations to the emission reductions in volatile organic compounds (VOC) and nitrogen oxides (NO x) show a VOC-sensitive regime for emission reductions to lower than 30-40% VOC and 30-50% NO x and a NO x-sensitive regime for larger percentage reductions. Meteorological parameters show that warm temperature, sufficient sunlight, low wind, and high surface pressure are distinct parameters that tend to trigger ozone episodes in polluted urban areas, like Kaohsiung.

Ground-Based Lidar for Atmospheric Boundary Layer Ozone Measurements

NASA Technical Reports Server (NTRS)

Kuang, Shi; Newchurch, Michael J.; Burris, John; Liu, Xiong

2013-01-01

Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than 10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

The Effects of Volcano-Induced Ozone Depletion on Short-lived Climate Forcing in the Arctic

NASA Astrophysics Data System (ADS)

Ward, P. L.

2012-12-01

Photodissociation of oxygen maintains the stratopause ~50°C warmer than the tropopause. Photodissociation of ozone warms the lower stratosphere, preventing most of this high-energy DNA-damaging solar radiation from reaching the troposphere. Ozone depletion allows more UV energy to reach the lower troposphere causing photodissociation of anthropogenic ozone and nitrogen dioxide. UV energy also penetrates the ocean >10 m where it is absorbed more efficiently than infrared radiation that barely penetrates the surface. Manmade chlorofluorocarbons caused ozone depletion from 1965 to 1994 with slow recovery predicted over the next 50+ years. But the lowest levels of ozone followed the eruptions of Pinatubo (1991 VEI=6), Eyjafjallajökull (2010 VEI=4), and Grímsvötn (2011 VEI=4). Each of the relatively small, basaltic eruptions in Iceland caused more ozone depletion than the long-term effects of chlorofluorocarbons, although total ozone appears to return to pre-eruption levels within a decade. Ozone depletion by 20% increases energy flux thru the lowermost troposphere by 0.7 W m-2 for overhead sun causing temperatures in the lower stratosphere to drop >2°C since 1958 in steps after the 3 largest volcanic eruptions: Agung 1963, El Chichón 1982, and Pinatubo. Temperatures at the surface increased primarily in the regions and at the times of the greatest observed ozone depletion. The greatest warming observed was along the Western Antarctic Peninsula (65.4°S) where minimum temperatures rose 6.7°C from 1951 to 2003 while maximum temperatures remained relatively constant. Minimum total column ozone in September-October was 40-56% lower than in 1972 almost every year since 1987, strongly anti-correlated with observed minimum temperatures. Sea ice decreased 10%, 7 ice shelves separated, 87% of the glaciers retreated and the Antarctic Circumpolar Current warmed. Elsewhere under the ozone hole, warming of continental Antarctica was limited by the high albedo (0.86) of Antarctic snow and decreasing solar zenith angles at higher latitudes. The second largest ozone depletion was in the Arctic at the times and places of greatest winter warming. Average ozone at four stations in Canada (43-59°N) compared to the 1961-1970 mean were 6% lower in December 2010 after the eruption of Eyjafjallajökull and 11% lower in December 2011 after the eruption of Grímsvötn. In 2012, ozone levels were still 10% lower in March and 7% lower in July. The regions and timing of this depletion are the regions and times of unusually warm temperatures and drought in North America during 2011-2012. The Dust Bowl droughts in 1934 and 1936 show a similar temporal relationship to a highly unusual sequence of five VEI=4-5 eruptions around the Pacific in 1931-1933. Major increases in global pollution were from 1950-1970 while ozone-destroying tropospheric chlorine rose from 1970 to 1994, along with ocean heat content and mean temperature. Pollution does not seem to cause an increase in warming until ozone depletion allows more UV into the lower troposphere. Pollutants decrease surface solar radiation but also reduce Arctic-snow albedo. Widespread observations imply that ozone depletion and associated photodissociation cause substantial warming. Several issues regarding the microphysics of absorption and radiation by greenhouse gases must be resolved before we can quantify their relative importance.

Exposure-Relevant Ozone Chemistry in Occupied Spaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coleman, Beverly Kaye

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, andmore » 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 byproduct yield) were explored. In Chapter 5, the reaction of ozone with permethrin, a residual insecticide used in aircraft cabins, to form phosgene is investigated. A derivatization technique was developed to detect phosgene at low levels, and chamber experiments were conducted with permethrin-coated cabin materials. It was determined that phosgene formation, if it occurs in the aircraft cabin, is not likely to exceed the relevant, health-based phosgene exposure guidelines.« less

Effects of a modular two-step ozone-water and annealing process on silicon carbide graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Matthew J., E-mail: matthew.webb@cantab.net; Lundstedt, Anna; Grennberg, Helena

By combining ozone and water, the effect of exposing epitaxial graphene on silicon carbide to an aggressive wet-chemical process has been evaluated after high temperature annealing in ultra high vacuum. The decomposition of ozone in water produces a number of oxidizing species, however, despite long exposure times to the aqueous-ozone environment, no graphene oxide was observed after the two-step process. The systems were comprehensively characterized before and after processing using Raman spectroscopy, core level photoemission spectroscopy, and angle resolved photoemission spectroscopy together with low energy electron diffraction, low energy electron microscopy, and atomic force microscopy. In spite of the chemicalmore » potential of the aqueous-ozone reaction environment, the graphene domains were largely unaffected raising the prospect of employing such simple chemical and annealing protocols to clean or prepare epitaxial graphene surfaces.« less

Radiative forcing perturbation due to observed increases in tropospheric ozone at Hohenpeissenberg

NASA Technical Reports Server (NTRS)

Wang, Wei-Chyung; Bojkov, Rumen D.; Zhuang, Yi-Cheng

1994-01-01

The effect on surface temperature due to changes in atmospheric O3 depends highly on the latitude where the change occurs. Previous sensitivity calculations indicate that ozone changes in the upper troposphere and lower stratosphere are more effective in causing surface temperature change (Wang et al., 1980). Long term ground-based observations show that tropospheric ozone, especially at the tropopause region, has been increasing at middle and high latitudes in the Northern Hemisphere (NATO, 1988; Quadrennial Ozone Symposium, 1992). These increases will enhance the greenhouse effect and increase the radiative forcing to the troposphere-surface system, which is opposite to the negative radiative forcing calculated from the observed stratospheric ozone depletion recently reported in WMO (1992). We used more than two thousands regularly measured ozonesondes providing reliable vertical O3 distribution at Hohenpeissenberg (47N; 11E) for the 1967-1990 to study the instantaneous solar and longwave radiative forcing the two decades 1971-1990 and compare the forcing with those caused by increasing CO2, CH4, N2O, and CFCs. Calculations are also made to compare the O3 radiative forcing between stratospheric depletion and tropospheric increase. Results indicate that the O3 changes will induce a positive radiative forcing dominated by tropospheric O3 increase and the magnitude of the forcing is comparable to that due to CO2 increases during the two decades. The significant implications of the tropospheric O3 increase to the global climate are discussed.

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

PubMed

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.

The Impact of Emission and Climate Change on Ozone in the United States under Representative Concentration Pathways (RCPs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Yang; Fu, Joshua S.; Drake, John B.

Dynamical downscaling was applied in this study to link the global climate-chemistry model Community Atmosphere Model (CAM-Chem) with the regional models: Weather Research and Forecasting (WRF) Model and Community Multi-scale Air Quality (CMAQ). Two Representative Concentration Pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) were used to evaluate the climate impact on ozone concentrations in 2050s. Ozone concentrations in the lower-mid troposphere (surface to ~300 hPa), from mid- to high latitudes in the Northern Hemisphere (NH), show decreasing trends in RCP 4.5 between 2000s and 2050s, with the largest decrease of 4-10 ppbv occurring in the summer and the fall;more » and increasing trends (2-12 ppbv) in RCP 8.5 resulting from the increased methane emissions. In RCP 8.5, methane emissions increase by ~60% by the end of 2050s, accounting for more than 90% of ozone increases in summer and fall, and 60-80% in spring and winter. Under the RCP 4.5 scenario, in the summer when photochemical reactions are the most active, the large ozone precursor emissions reduction leads to the greatest decrease of downscaled surface ozone concentrations, ranging from 6 to 10 ppbv. However, a few major cities show ozone increases of 3 to 7 ppbv due to weakened NO titration. Under the RCP 8.5 scenario, in winter, downscaled ozone concentrations increase across nearly the entire continental US in winter, ranging from 3 to 10 ppbv due to increased methane emissions and enhanced stratosphere-troposphere exchange (STE). More intense heat waves are projected to occur by the end of 2050s in RCP 8.5, leading to more than 8 ppbv of the maximum daily 8-hour daily average (MDA8) ozone during the heat wave days than other days; this indicates the dramatic impact heat waves exert on high frequency ozone events.« less

Understanding and improving global crop response to ozone pollution

USDA-ARS?s Scientific Manuscript database

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 ...

CORONA-INDUCED OZONATION COUPLED WITH PHOTOOXIDATION: AN ENVIRONMENTALLY FRIENDLY AND COST-EFFECTIVE METHOD

EPA Science Inventory

We have developed a process that uses surface corona for the production of ozone by passing air or oxygen through a high voltage electrical discharge and the emitted ultraviolet light is being used to activate a photocatalyst. A thin film of nanostructured TiO2 with primary part...

Effects of trans-Eurasian transport of air pollutants on surface ozone concentrations over Western China

NASA Astrophysics Data System (ADS)

Li, Xiaoyuan; Liu, Junfeng; Mauzerall, Denise L.; Emmons, Louisa K.; Walters, Stacy; Horowitz, Larry W.; Tao, Shu

2014-11-01

Due to a lack of industrialization in Western China, surface air there was, until recently, believed to be relatively unpolluted. However, recent measurements and modeling studies have found high levels of ozone (O3) there. Based on the state-of-the-science global chemical transport model MOZART-4, we identify the origin, pathway, and mechanism of trans-Eurasian transport of air pollutants to Western China in 2000. MOZART-4 generally simulates well the observed surface O3 over inland areas of China. Simulations find surface ozone concentrations over Western China on average to be about 10 ppbv higher than Eastern China. Using sensitivity studies, we find that anthropogenic emissions from all Eurasian regions except China contribute 10-15 ppbv surface O3 over Western China, superimposed upon a 35-40 ppbv natural background. Transport from European anthropogenic sources to Northwestern China results in 2-6 ppbv O3 enhancements in spring and summer. Indian anthropogenic sources strongly influence O3 over the Tibetan Plateau during the summer monsoon. Transport of O3 originating from emissions in the Middle East occasionally reach Western China and increase surface ozone there by about 1-4 ppbv. These influences are of similar magnitude as trans-Pacific and transatlantic transport of O3 and its precursors, indicating the significance of trans-Eurasian ozone transport in hemispheric transport of air pollution. Our study further indicates that mitigation of anthropogenic emissions from Europe, the Indian subcontinent, and the Middle East could benefit public health and agricultural productivity in Western China.

Effects of trans-Eurasian transport of anthropogenic pollutants on surface ozone concentrations over China

NASA Astrophysics Data System (ADS)

Liu, J.; Li, X.; Mauzerall, D. L.; Emmons, L. K.; Horowitz, L. W.; Guo, Y.; Tao, S.

2015-12-01

Due to a lack of industrialization in Western China, surface air there was, until recently, believed to be relatively unpolluted. However, recent measurements and modeling studies have found high levels of ozone (O3) there. Based on the state-of-the-science global chemical transport model MOZART-4, we identify the origin, pathway, and mechanism of trans-Eurasian transport of air pollutants to Western China in 2000. MOZART-4 generally simulates well the observed surface O3 over inland areas of China. Simulations find surface ozone concentrations over Western China on average to be about 10 ppbv higher than Eastern China. Using sensitivity studies as well as a fully-tagged approach, we find that anthropogenic emissions from all Eurasian regions except China contribute 10-15 ppbv surface O3 over Western China, superimposed upon a 35-40 ppbv natural background. Transport from European anthropogenic sources to Northwestern China results in 2-6 ppbv O3 enhancements in spring and summer. Indian anthropogenic sources strongly influence O3 over the Tibetan Plateau during the summer monsoon. Transport of O3 originating from emissions in the Middle East occasionally reach Western China and increase surface ozone there by about 1-4 ppbv. These influences are of similar magnitude as trans-Pacific and transatlantic transport of O3 and its precursors, indicating the significance of trans-Eurasian ozone transport in hemispheric transport of air pollution. Our study further indicates that mitigation of anthropogenic emissions from Europe, the Indian subcontinent, and the Middle East could benefit public health and agricultural productivity in Western China.

Catalytic membrane reactor for water and wastewater treatment

NASA Astrophysics Data System (ADS)

Heng, Samuel

A double membrane reactor was fabricated and assessed for continuous treatment of water containing organic contaminants by ozonation. This innovative reactor consisted of a zeolite membrane prepared on the inner surface of a porous a-alumina support, which served as water selective extractor and active contactor, and a porous stainless membrane which was the ozone gas diffuser. The coupling of membrane separation and chemical oxidation was found to be highly beneficial to both processes. The total organic carbon (TOC) removal rate at the retentate was enhanced by up to 2.2 times, as compared to membrane ozonation. Simultaneously, clean water (< 2 mg C.L-1 ) was consistently produced on the permeate side, using a feed solution containing up to 1000 mg C.L-1, while the retentate was concentrated and treated. Most significantly, the addition of an adsorbing material, as a bed or a coated layer, onto the pores of the membrane support, was shown to further enhance TOC degradation, permeated TOC concentration, permeate flux, and moreover, ozone yield. The achievements of this project included: (1) The development of a novel low-temperature zeolite membrane activation method that generates consistently high quality membranes (i.e. high reproducibility and fewer defects). (2) The demonstration that gamma-alumina and gamma-alumina supported catalysts do not have significant activity and that the TOC removal enhancement usually observed during catalytic ozonation was due primarily to the contribution of adsorption and metal leaching. Thermogravimetric analysis (TGA) and elemental analysis (EA) of the spent catalyst showed that, during catalytic ozonation, oxygenated by-products of increased adsorbability were concentrated onto the gamma-alumina contactor, and were subsequently degraded. (3) The development of a method for coating high surface area gamma-alumina layers onto the grains of zeolite membrane support used as the active membrane contactor.

Modulations of stratospheric ozone by volcanic eruptions

NASA Technical Reports Server (NTRS)

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.

Public, experts join at town meeting

NASA Astrophysics Data System (ADS)

Bush, Susan

About 80 citizens concerned with the threat of ozone depletion attended a public meeting on June 9 in Charlottesville, Va., to discuss the issue with a panel of six leading ozone experts. Held in conjunction with the Quadrennial Ozone Symposium, the town meeting was videotaped for airing on public broadcast stations this fall. The meeting was aimed at nonexperts, to “get the word out” to the public, said the moderator, journalist Peter Hackes.The lively, sometimes heated discussion showed the public's high awareness and concern over problems associated with ozone depletion. During the nearly 2-hour meeting topics ranged from the reparability of the ozone layer, to steps the public can take to help mitigate ozone loss, to reports of increased cases of skin cancer due to more ultraviolet radiation reaching the Earth's surface. There were also some claims that ozone depletion is overexaggerated and is a hoax for scientists to get more research funding.

A numerical study of tropospheric ozone in the springtime in East Asia

NASA Astrophysics Data System (ADS)

Zhang, Meigen; Xu, Yongfu; Itsushi, Uno; Hajime, Akimoto

2004-04-01

The Models-3 Community Multi-scale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System (RAMS) is applied to East Asia to study the transport and photochemical transformation of tropospheric ozone in March 1998. The calculated mixing ratios of ozone and carbon monoxide are compared with ground level observations at three remote sites in Japan and it is found that the model reproduces the observed features very well. Examination of several high episodes of ozone and carbon monoxide indicates that these elevated levels are found in association with continental outflow, demonstrating the critical role of the rapid transport of carbon monoxide and other ozone precursors from the continental boundary layer. In comparison with available ozonesonde data, it is found that the model-calculated ozone concentrations are generally in good agreement with the measurements, and the stratospheric contribution to surface ozone mixing ratios is quite limited.

Development of nanomaterial-enabled advanced oxidation techniques for treatment of organic micropollutants

NASA Astrophysics Data System (ADS)

Oulton, Rebekah Lynn

Increasing demand for limited fresh water resources necessitates that alternative water sources be developed. Nonpotable reuse of treated wastewater represents one such alternative. However, the ubiquitous presence of organic micropollutants such as pharmaceuticals and personal care products (PPCPs) in wastewater effluents limits use of this resource. Numerous investigations have examined PPCP fate during wastewater treatment, focusing on their removal during conventional and advanced treatment processes. Analysis of influent and effluent data from published studies reveals that at best 1-log10 concentration unit of PPCP removal can generally be achieved with conventional treatment. In contrast, plants employing advanced treatment methods, particularly ozonation and/or membranes, remove most PPCPs often to levels below analytical detection limits. However, membrane treatment is cost prohibitive for many facilities, and ozone treatment can be very selective. Ozone-recalcitrant compounds require the use of Advanced Oxidation Processes (AOPs), which utilize highly reactive hydroxyl radicals (*OH) to target resistant pollutants. Due to cost and energy use concerns associated with current AOPs, alternatives such as catalytic ozonation are under investigation. Catalytic ozonation uses substrates such as activated carbon to promote *OH formation during ozonation. Here, we show that multi-walled carbon nanotubes (MWCNTs) represent another viable substrate, promoting *OH formation during ozonation to levels exceeding activated carbon and equivalent to conventional ozone-based AOPs. Via a series of batch reactions, we observ a strong correlation between *OH formation and MWCNT surface oxygen concentrations. Results suggest that deprotonated carboxyl groups on the CNT surface are integral to their reactivity toward ozone and corresponding *OH formation. From a practical standpoint, we show that industrial grade MWCNTs exhibit similar *OH production as their research-grade counterparts. Accelerated aging studies indicate that MWCNTs maintain surface reactivity for an extended period during ozonation treatment. Further, *OH generation is essentially unaffected in complex water matrices containing known radical scavengers, and is effective for degradation of the ozone-recalcitrant herbicide atrazine. A proof-of-concept study verified that results from batch systems can be replicated in a flow-through reactor utilizing MWCNTs immobilized on a ceramic membrane support. Collective, results suggest that CNT-enhanced ozonation may provide a viable treatment alternative for emerging organic micropollutants.

Impact of Surface Emissions to the Zonal Variability of Tropical Tropospheric Ozone and Carbon Monoxide for November 2004

NASA Technical Reports Server (NTRS)

Bowman, K. W.; Jones, D.; Logan, J.; Worden, H.; Boersma, F.; Chang, R.; Kulawik, S.; Osterman, G.; Worden, J.

2008-01-01

The chemical and dynamical processes governing the zonal variability of tropical tropospheric ozone and carbon monoxide are investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions. Vertical ozone profile estimates from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show the so called zonal 'wave-one' pattern, which is characterized by peak ozone concentrations (70-80 ppb) centered over the Atlantic, as well as elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere. 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., 2007). 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% and led to changes in GEOS-Chem upper tropospheric ozone of up to 40% over Indonesia. The remaining residual differences can be explained in part by upper tropospheric ozone produced from lightning NOx in the South Atlantic. Furthermore, model simulations from GEOS-Chem indicate that ozone over Indonesian/Australian is more sensitive to changes in surface emissions of NOx than ozone over the tropical Atlantic.

Study of UV cloud modification factors in Southern Patagonia

NASA Astrophysics Data System (ADS)

Wolfram, Elian A.; Orte, Facundo; Salvador, Jacobo; Quiroga, Jonathan; D'Elia, Raúl; Antón, Manuel; Alados-Arboledas, Lucas; Quel, Eduardo

2017-02-01

Anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth's surface, mainly through the Antarctic ozone hole, making the ozone and ultraviolet (UV) radiation two important issues in the study of Earth atmosphere in the scientific community. Also the clouds have been identified as the main modulator of UV amount in short time scales and produce the main source of uncertainty in the projection of surface UV level as consequence of projected ozone recovery. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as consequence the surface UV radiation may be higher than an equivalent clear sky scenario for several minutes. In particular this situation can be important when low ozone column and partially cloud cover skies happen simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an atmospheric remote sensing site near the city of Río Gallegos (51°55'S, 69°14'W). In this paper, the impact of clouds over the UV radiation is investigated by the use of ground based measurements from the passive remote sensing instruments operating at this site, mainly of broad and moderate narrow band filter radiometers. We analyzed the UV Index obtained from a multiband filter radiometer GUV-541 (UVI) [Biospherical Inc.] installed in the Observatorio Atmosférico de la Patagonia Austral, Río Gallegos, since 2005. Cloud modification factors (CMF, ratio between the measured UV radiation in a cloudy sky and the simulated radiation under cloud-free conditions) are evaluated for the study site. The database used in this work covers the period 2005-2012 for spring and summer seasons, when the ozone hole can affect these subpolar regions. CMF higher than 1 are found during spring and summer time, when lower total ozone columns, higher solar elevations and high cloud cover occur simultaneously, producing extreme erythemal irradiance at ground surface. Enhancements as high as 25% were registered. The maximum duration of the enhancement was around 30 minute. This produces dangerous sunbathing situations for the Río Gallegos citizen.

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

PubMed

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.

Global Distribution and Trends of Tropospheric Ozone: An Observation-Based Review

NASA Technical Reports Server (NTRS)

Cooper, O. R.; Parrish, D. D.; Ziemke, J.; Cupeiro, M.; Galbally, I. E.; Gilge, S.; Horowitz, L.; Jensen, N. R.; Lamarque, J.-F.; Naik, V.;

An Elevated Reservoir of Air Pollutants over the Mid-Atlantic States During the 2011 DISCOVER-AQ Campaign: Airborne Measurements and Numerical Simulations

NASA Technical Reports Server (NTRS)

He, Hao; Loughner, Christopher P.; Stehr, Jeffrey W.; Arkinson, Heather L.; Brent, Lacey C.; Follette-Cook, Melanie B.; Tzortziou, Maria A.; Pickering, Kenneth E.; Thompson, Anne M.; Martins, Douglas K.;

Stratospheric contribution to surface ozone in the desert Southwest during the 2013 Las Vegas Ozone Study

NASA Astrophysics Data System (ADS)

Langford, A. O.; Senff, C. J.; Alvarez, R. J. _II, II; Brioude, J. F.; Cooper, O. R.; Holloway, J. S.; Lin, M.; Marchbanks, R.; Pierce, R. B.; Reddy, P. J.; Sandberg, S.; Weickmann, A. M.; Williams, E. J.; Gustin, M. S.; Iraci, L. T.; Leblanc, T.; Yates, E. L.

2014-12-01

The 2013 Las Vegas Ozone Study (LVOS) was designed to investigate the potential impact of stratosphere-troposphere transport (STT) and long-range transport of pollution from Asia on surface O3 concentrations in Clark County, NV. This measurement campaign, which took place in May and June of 2013, was conducted at Angel Peak, NV, a high elevation site about 2.8 km above mean sea level and 45 km west of Las Vegas. The study was organized around the NOAA ESRL truck-based TOPAZ scanning ozone lidar with collocated in situ sampling of O3, CO, and meteorological parameters. These measurements were supported by the NOAA/NESDIS real time modelling system (RAQMS), FLEXPART particle dispersion model, and the NOAA GFDL AM3 model. In this talk, I will describe one of several STT events that occurred during the LVOS campaign. This intrusion, which was profiled by TOPAZ on the night of May 24-25, was also sampled by the NASA Alpha Jet, the Table Mountain ozone lidar, and by an ozonesonde flying above southern California. This event also led to significant ozone increases at surface monitors operated by Clark County, the California Air Resources Board, the U.S. National Park Service, and the Nevada Rural Ozone Initiative (NRVOI), and resulted in exceedances of the 2008 75 ppbv O3 NAAQS both in Clark County and in surrounding areas of Nevada and southern California. The potential implications of this and similar events for air quality compliance in the western U.S. will be discussed.

Reactive nitrogen partitioning and its relationship to winter ozone events in Utah

NASA Astrophysics Data System (ADS)

Wild, R. J.; Edwards, P. M.; Bates, T. S.; Cohen, R. C.; de Gouw, J. A.; Dubé, W. P.; Gilman, J. B.; Holloway, J.; Kercher, J.; Koss, A. R.; Lee, L.; Lerner, B. M.; McLaren, R.; Quinn, P. K.; Roberts, J. M.; Stutz, J.; Thornton, J. A.; Veres, P. R.; Warneke, C.; Williams, E.; Young, C. J.; Yuan, B.; Zarzana, K. J.; Brown, S. S.

2016-01-01

High wintertime ozone levels have been observed in the Uintah Basin, Utah, a sparsely populated rural region with intensive oil and gas operations. The reactive nitrogen budget plays an important role in tropospheric ozone formation. Measurements were taken during three field campaigns in the winters of 2012, 2013 and 2014, which experienced varying climatic conditions. Average concentrations of ozone and total reactive nitrogen were observed to be 2.5 times higher in 2013 than 2012, with 2014 an intermediate year in most respects. However, photochemically active NOx (NO + NO2) remained remarkably similar all three years. Nitric acid comprised roughly half of NOz ( ≡ NOy - NOx) in 2013, with nighttime nitric acid formation through heterogeneous uptake of N2O5 contributing approximately 6 times more than daytime formation. In 2012, N2O5 and ClNO2 were larger components of NOz relative to HNO3. The nighttime N2O5 lifetime between the high-ozone year 2013 and the low-ozone year 2012 is lower by a factor of 2.6, and much of this is due to higher aerosol surface area in the high-ozone year of 2013. A box-model simulation supports the importance of nighttime chemistry on the reactive nitrogen budget, showing a large sensitivity of NOx and ozone concentrations to nighttime processes.

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

PubMed

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.

Impact of chemical lateral boundary conditions in a regional air quality forecast model on surface ozone predictions during stratospheric intrusions

NASA Astrophysics Data System (ADS)

Pendlebury, Diane; Gravel, Sylvie; Moran, Michael D.; Lupu, Alexandru

2018-02-01

A regional air quality forecast model, GEM-MACH, is used to examine the conditions under which a limited-area air quality model can accurately forecast near-surface ozone concentrations during stratospheric intrusions. Periods in 2010 and 2014 with known stratospheric intrusions over North America were modelled using four different ozone lateral boundary conditions obtained from a seasonal climatology, a dynamically-interpolated monthly climatology, global air quality forecasts, and global air quality reanalyses. It is shown that the mean bias and correlation in surface ozone over the course of a season can be improved by using time-varying ozone lateral boundary conditions, particularly through the correct assignment of stratospheric vs. tropospheric ozone along the western lateral boundary (for North America). Part of the improvement in surface ozone forecasts results from improvements in the characterization of near-surface ozone along the lateral boundaries that then directly impact surface locations near the boundaries. However, there is an additional benefit from the correct characterization of the location of the tropopause along the western lateral boundary such that the model can correctly simulate stratospheric intrusions and their associated exchange of ozone from stratosphere to troposphere. Over a three-month period in spring 2010, the mean bias was seen to improve by as much as 5 ppbv and the correlation by 0.1 depending on location, and on the form of the chemical lateral boundary condition.

Climate Change Impacts on Projections of Excess Mortality at 2030 using Spatially-Varying Ozone-Temperature Risk Surfaces

PubMed Central

Wilson, Ander; Reich, Brian J.; Nolte, Christopher G.; Spero, Tanya L.; Hubbell, Bryan; Rappold, Ana G.

2017-01-01

We project the change in ozone-related mortality burden attributable to changes in climate between a historical (1995–2005) and near-future (2025–2035) time period while incorporating a nonlinear and synergistic effect of ozone and temperature on mortality. We simulate air quality from climate projections varying only biogenic emissions and holding anthropogenic emissions constant, thus attributing changes in ozone only to changes in climate and independent of changes in air pollutant emissions. We estimate nonlinear, spatially-varying, ozone-temperature risk surfaces for 94 US urban areas using observed data. Using the risk surfaces and climate projections we estimate daily mortality attributable to ozone exceeding 40 ppb (moderate level) and 75 ppb (US ozone NAAQS) for each time period. The average increases in city-specific median April-October ozone and temperature between time periods are 1.02 ppb and 1.94°F; however, the results varied by region. Increases in ozone due to climate change result in an increase in ozone-mortality burden. Mortality attributed to ozone exceeding 40 ppb increases by 7.7% (1.6%, 14.2%). Mortality attributed to ozone exceeding 75 ppb increases by 14.2% (1.6%, 28.9%). The absolute increase in excess ozone mortality is larger for changes in moderate ozone levels, reflecting the larger number of days with moderate ozone levels. PMID:27005744

The TOAR database on observations of surface ozone (and more)

NASA Astrophysics Data System (ADS)

Schultz, M. G.; Schröder, S.; Cooper, O. R.; Galbally, I. E.; Petropavlovskikh, I. V.; von Schneidemesser, E.; Tanimoto, H.; Elshorbany, Y. F.; Naja, M. K.; Seguel, R. J.

2017-12-01

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. 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. This presentation will provide a summary of the TOAR surface observations database including recent additions of ozone precursor and meteorological data. We will demonstrate how the database can be accessed and the data can be used, and we will discuss its limitations and the potential for closing some of teh remaining data gaps.

Vertical ozone characteristics in urban boundary layer in Beijing.

PubMed

Ma, Zhiqiang; Xu, Honghui; Meng, Wei; Zhang, Xiaoling; Xu, Jing; Liu, Quan; Wang, Yuesi

2013-07-01

Vertical ozone and meteorological parameters were measured by tethered balloon in the boundary layer in the summer of 2009 in Beijing, China. A total of 77 tethersonde soundings were taken during the 27-day campaign. The surface ozone concentrations measured by ozonesondes and TEI 49C showed good agreement, albeit with temporal difference between the two instruments. Two case studies of nocturnal secondary ozone maxima are discussed in detail. The development of the low-level jet played a critical role leading to the observed ozone peak concentrations in nocturnal boundary layer (NBL). The maximum of surface ozone was 161.7 ppbv during the campaign, which could be attributed to abundant precursors storage near surface layer at nighttime. Vertical distribution of ozone was also measured utilizing conventional continuous analyzers on 325-m meteorological observation tower. The results showed the NBL height was between 47 and 280 m, which were consistent with the balloon data. Southerly air flow could bring ozone-rich air to Beijing, and the ozone concentrations exceeded the China's hourly ozone standard (approximately 100 ppb) above 600 m for more than 12 h.

Ozone assisted oxidation of gaseous PCDD/Fs over CNTs-containing composite catalysts at low temperature.

PubMed

Wang, Qiulin; Tang, Minghui; Peng, Yaqi; Du, Cuicui; Lu, Shengyong

2018-05-01

Ozone assisted carbon nanotubes (CNTs) supported vanadium oxide/titanium dioxide (V/Ti-CNTs) or vanadium oxide-manganese oxide/titanium dioxide (V-Mn/Ti-CNTs) catalysts towards gaseous PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) catalytic oxidations at low temperature (150 °C) were investigated. The removal efficiency (RE) and decomposition efficiency (DE) of PCDD/Fs achieved with V-Mn/Ti-CNTs alone were 95% and 45% at 150 °C under a space velocity (SV) of 14000 h -1 ; yet, these values reached 99% and 91% when catalyst and low concentration (50 ppm) ozone were used in combined. The ozone promotion effect on catalytic activity was further enhanced with the addition of manganese oxide (MnO x ) and CNTs. Adding MnO x and CNTs in V/Ti catalysts facilitated the ozone decomposition (creating more active species on catalyst surface), thus, improved ozone utilization (demanding relatively lower ozone addition concentration). On the other hand, this study threw light upon ozone promotion mechanism based on the comparison of catalyst properties (i.e. components, surface area, surface acidity, redox ability and oxidation state) before and after ozone treatment. The experimental results indicate that a synergistic effect exists between catalyst and ozone: ozone is captured and decomposed on catalyst surface; meanwhile, the catalyst properties are changed by ozone in return. Reactive oxygen species from ozone decomposition and the accompanied catalyst properties optimization are crucial reasons for catalyst activation at low temperature. Copyright © 2018 Elsevier Ltd. All rights reserved.

Influence of altitude on ozone levels and variability in the lower troposphere: a ground-based study for western Europe over the period 2001-2004

NASA Astrophysics Data System (ADS)

Chevalier, A.; Gheusi, F.; Delmas, R.; Ordóñez, C.; Sarrat, C.; Zbinden, R.; Thouret, V.; Athier, G.; Cousin, J.-M.

2007-08-01

The PAES (French acronym for synoptic scale atmospheric pollution) network focuses on the chemical composition (ozone, CO, NOx/y and aerosols) of the lower troposphere (0-3000 m). Its high-altitude surface stations located in different mountainous areas in France complete the low-altitude rural MERA stations (the French contribution to the european program EMEP, European Monitoring and Evaluation Program). They are representative of pollution at the scale of the French territory because they are away from any major source of pollution. This study deals with ozone observations between 2001 and 2004 at 11 stations from PAES and MERA, in addition to 16 elevated stations located in mountainous areas of Switzerland, Germany, Austria, Italy and Spain. The set of stations covers a range of altitudes between 115 and 3550 m. The comparison between recent ozone mixing ratios to those of the last decade at Pic du Midi (2877 m), as well as trends calculated over 14-year data series at three high-altitude sites in the Alps (Jungfraujoch, Sonnblick and Zugspitze) reveal that ozone is still increasing but at a slower rate than in the 1980s and 1990s. The 2001-2004 mean levels of ozone from surface stations capture the ozone stratification revealed by climatological profiles from the airborne observation system MOZAIC (Measurement of OZone and water vapour by Airbus In-service airCraft) and from ozone soundings above Payerne (Switzerland). In particular all data evidence a clear transition at about 1000-1200 m a.s.l. between a sharp gradient below (of the order of +30 ppb/km) and a gentler gradient (+3 ppb/km) above. The same altitude (1200 m) is also found to be a threshold regarding how well the ozone levels at the surface stations agree with the free-tropospheric reference (MOZAIC or soundings). Below the departure can be as large as 40%, but suddenly drops within 15% above. For stations above 2000 m, the departure is even less than 8%. Ozone variability also reveals a clear transition between boundary-layer and free-tropospheric regimes around 1000 m a.s.l. Below, diurnal photochemistry accounts for about the third of the variability in summer, but less than 20% above - and at all levels in winter - where ozone variability is mostly due to day-to-day changes (linked to weather conditions or synoptic transport). In summary, the altitude range 1000-1200 m clearly turns out in our study to be an upper limit below which specific surface effects dominate the ozone content. Monthly-mean ozone mixing-ratios show at all levels a minimum in winter and the classical summer broad maximum in spring and summer - which is actually the superposition of the tropospheric spring maximum (April-May) and regional pollution episodes linked to persistent anticyclonic conditions that may occur from June to September. To complement this classical result it is shown that summer maxima are associated with considerably more variability than the spring maximum. This ensemble of findings support the relevance of mountain station networks such as PAES for the long-term observation of free-tropospheric ozone over Europe.

Estimation of UV index in the clear-sky using OMI PROFOZ and AERONET data

NASA Astrophysics Data System (ADS)

Lee, H.; Kim, J.; Jeong, U.

2016-12-01

Due to a strong influence to the human health and ecosystem environment, continuous monitoring of the surface-level ultraviolet (UV) radiation is important nowadays. UV index (UVI) is a simple parameter to show the strength of surface UV radiation, therefore UVI has been widely utilized for the purpose of UV monitoring. In this work, we also try to develop our own retrieval algorithm for better estimation of UVI. The amount of UVA (320-400 nm) and UVB (290-320 nm) radiation at the Earth surface depends on the extent of Rayleigh scattering by atmospheric gas molecules, the radiative absorption by ozone, radiative scattering by clouds, and both absorption and scattering by airborne aerosols. Thus advanced consideration of these factors is the essential part to establish the process of UVI estimation. In this study, we estimate UV Index (UVI) at Seoul first in a clear-sky atmosphere, and then validate this estimated UVI comparing to UVI from Brewer spectrophotometer measurements located at Yonsei University in Seoul. We use the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model version 2.6 for our UVI calculation. To consider the ozone and aerosol influence in a real situation, we input ozone and temperature profiles from the Ozone Monitoring Instrument (OMI) Aura vertical profile ozone (PROFOZ) data, and aerosol properties from the AErosol RObotic NETwork (AERONET) measurements at Seoul into the model. Inter-comparison of UVI is performed for the year 2011, 2012 and 2014, and resulted in a high correlation coefficient (R=0.95) under clear-sky condition. But a slight overestimation of Brewer UVI occurred under high AOD conditions in clear-sky. Because our UVI algorithm does not account for surface absorbing aerosols, it is lead to systematic overestimation of surface UV irradiances. Therefore, we also investigate the effect of absorbing aerosol on the amount of UV irradiance in the clear-sky over East Asia.

Trends in surface ozone concentrations at Arosa (Switzerland)

NASA Astrophysics Data System (ADS)

Staehelin, Johannes; Thudium, Juerg; Buehler, Ralph; Volz-Thomas, Andreas; Graber, Werner

During the years 1989-1991, ozone was measured at four sites around Arosa (Switzerland). One of these sites was identical with that, where surface ozone was measured in the 1950s (Götz and Volz, 1951; Perl, 1965). Comparison of both old and recent data indicates that surface ozone concentrations at Arosa have increased by a factor of approximately 2.2. The increase shows a seasonal variation with a relative increase of more than a factor of three in December and January. The results are discussed in the context of measurements made at other times, locations and altitudes. The comparison indicates that the increase in ozone levels at Arosa has most likely occured between the fifties and today. The measurements additionally suggest that photochemical ozone production in the free troposphere has significantly contributed to the observed ozone trends in winter.

Ground-based lidar for atmospheric boundary layer ozone measurements.

PubMed

Kuang, Shi; Newchurch, Michael J; Burris, John; Liu, Xiong

2013-05-20

Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than ±10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

Apparatus and process for the surface treatment of carbon fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paulauskas, Felix Leonard; Ozcan, Soydan; Naskar, Amit K.

A method for surface treating a carbon-containing material in which carbon-containing material is reacted with decomposing ozone in a reactor (e.g., a hollow tube reactor), wherein a concentration of ozone is maintained throughout the reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering the reactor, and position of one or more ozone inlets (ports) in the reactor, wherein the method produces a surface-oxidized carbon or carbon-containing material, preferably having a surface atomic oxygen content of at least 15%. The resulting surface-oxidized carbon material and solid composites made therefrom are also described.

Long-term performance of passive materials for removal of ozone from indoor air.

PubMed

Cros, C J; Morrison, G C; Siegel, J A; Corsi, R L

2012-02-01

The health effects associated with exposure to ozone range from respiratory irritation to increased mortality. In this paper, we explore the use of three green building materials and an activated carbon (AC) mat that remove ozone from indoor air. We studied the effects of long-term exposure of these materials to real environments on ozone removal capability and pre- and post-ozonation emissions. A field study was completed over a 6-month period, and laboratory testing was intermittently conducted on material samples retrieved from the field. The results show sustained ozone removal for all materials except recycled carpet, with greatest ozone deposition velocity for AC mat (2.5-3.8 m/h) and perlite-based ceiling tile (2.2-3.2 m/h). Carbonyl emission rates were low for AC across all field sites. Painted gypsum wallboard and perlite-based ceiling tile had similar overall emission rates over the 6-month period, while carpet had large initial emission rates of undesirable by-products that decayed rapidly but remained high compared with other materials. This study confirms that AC mats and perlite-based ceiling tile are viable surfaces for inclusion in buildings to remove ozone without generating undesirable by-products. PRACTICAL IMPLICATIONS The use of passive removal materials for ozone control could decrease the need for, or even render unnecessary, active but energy consuming control solutions. In buildings where ozone should be controlled (high outdoor ozone concentrations, sensitive populations), materials specifically designed or selected for removing ozone could be implemented, as long as ozone removal is not associated with large emissions of harmful by-products. We find that activated carbon mats and perlite-based ceiling tiles can provide substantial, long-lasting, ozone control. © 2011 John Wiley & Sons A/S.

Ozone adsorption on carbon nanoparticles

NASA Astrophysics Data System (ADS)

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 < 50 nm), under magnetic stirring. The aerosol was then mixed with ozone in an aerosol flow tube. Ozone uptake experiments were performed with different particles concentrations with a fixed ozone concentration. The influence of several factors on kinetics was examined: initial ozone concentration, particle size (50 nm ≤ Dp ≤ 200 nm) and competitive adsorption (with probe molecule and water). The effect of initial ozone concentration was first 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 (or O2) and were chosen because it is believed to form the same reactive oxygen intermediates than ozone. A weak water physisorption on soot was observed revealing hydrophobic properties of particles. Oxygen atoms were found to be strongly reactive. A Langmuir behavior was observed for oxygen atoms adsorption on carbon particles and we were able to determine an initial uptake coefficient of approximately 2.10-2. [1] Fenidel, W., et al., Interaction between carbon or iron aerosol particles and ozone. Atmospheric Environment, 1995. 29(9): p. 967-973. [2] Smith, D. and A. Chughtai, Reaction kinetics of ozone at low concentrations with n-hexane soot. Journal of geophysical research, 1996. 101(D14): p. 19607-19,620. [3] Kamm, S., et al., The heterogeneous reaction of ozone with soot aerosol. Atmospheric Environment, 1999. 33(28): p. 4651-4661. [4] Stephens, S., M.J. Rossi, and D.M. Golden, The heterogeneous reaction of ozone on carbonaceous surfaces. International journal of chemical kinetics, 1986. 18(10): p. 1133-1149. [5] Pöschl, U., et al., Interaction of ozone and water vapor with spark discharge soot aerosol particles coated with benzo [a] pyrene: O3 and H2O adsorption, benzo [a] pyrene degradation, and atmospheric implications. The Journal of Physical Chemistry A, 2001. 105(16): p. 4029-4041.

Influence of Mountains on Arctic Tropospheric Ozone

NASA Astrophysics Data System (ADS)

Whiteway, J. A.; Seabrook, J.

2015-12-01

Tropospheric ozone was measured above Ellesmere Island in the Canadian Arctic during spring using a differential absorption lidar (DIAL). Analysis of the observations revealed that mountains had a significant effect on the vertical distribution of ozone. Ozone depletion events were observed when air that had spent significant time near to the frozen surface of the Arctic Ocean reached Eureka. This air arrived at Eureka by flowing over the surrounding mountains. Surface level ozone depletion events were not observed during periods when mountains blocked the flow of air from over the sea ice. In the case of blocking there was an enhancement in the amount of ozone near the surface as air from the mid troposphere descended in the lee of the mountains. Three case studies will be presented.

Quantifying wintertime boundary layer ozone production from frequent profile measurements in the Uinta Basin, UT, oil and gas region

NASA Astrophysics Data System (ADS)

Schnell, Russell C.; Johnson, Bryan J.; Oltmans, Samuel J.; Cullis, Patrick; Sterling, Chance; Hall, Emrys; Jordan, Allen; Helmig, Detlev; Petron, Gabrielle; Ahmadov, Ravan; Wendell, James; Albee, Robert; Boylan, Patrick; Thompson, Chelsea R.; Evans, Jason; Hueber, Jacques; Curtis, Abigale J.; Park, Jeong-Hoo

2016-09-01

As part of the Uinta Basin Winter Ozone Study, January-February 2013, we conducted 937 tethered balloon-borne ozone vertical and temperature profiles from three sites in the Uinta Basin, Utah (UB). Emissions from oil and gas operations combined with snow cover were favorable for producing high ozone-mixing ratios in the surface layer during stagnant and cold-pool episodes. The highly resolved profiles documented the development of approximately week-long ozone production episodes building from regional backgrounds of 40 ppbv to >165 ppbv within a shallow cold pool up to 200 m in depth. Beginning in midmorning, ozone-mixing ratios increased uniformly through the cold pool layer at rates of 5-12 ppbv/h. During ozone events, there was a strong diurnal cycle with each succeeding day accumulating 4-8 ppbv greater than the previous day. The top of the elevated ozone production layer was nearly uniform in altitude across the UB independent of topography. Above the ozone production layer, mixing ratios decreased with height to 400 m above ground level where they approached regional background levels. Rapid clean-out of ozone-rich air occurred within a day when frontal systems brought in fresh air. Solar heating and basin topography led to a diurnal flow pattern in which daytime upslope winds distributed ozone precursors and ozone in the Basin. NOx-rich plumes from a coal-fired power plant in the eastern sector of the Basin did not appear to mix down into the cold pool during this field study.

Impacts of seasonal and regional variability in biogenic VOC emissions on surface ozone in the Pearl River Delta region, China

DOE Office of Scientific and Technical Information (OSTI.GOV)

Situ, S.; Guenther, Alex B.; Wang, X. J.

In this study, the BVOC emissions in November 2010 over the Pearl River Delta (PRD) region in southern China have been estimated by the latest version of a Biogenic Volatile Organic Compound (BVOC) emission model (MEGAN v2.1). The evaluation of MEGAN performance at a representative forest site within this region indicates MEGAN can estimate BVOC emissions reasonably well in this region except overestimating isoprene emission in autumn for reasons that are discussed in this manuscript. Along with the output from MEGAN, the Weather Research and Forecasting model with chemistry (WRF-Chem) is used to estimate the impacts of BVOC emissions onmore » surface ozone in the PRD region. The results show BVOC emissions increase the daytime ozone peak by *3 ppb on average, and the max hourly impacts of BVOC emissions on the daytime ozone peak is 24.8 ppb. Surface ozone mixing ratios in the central area of Guangzhou- Foshan and the western Jiangmen are most sensitive to BVOC emissions BVOCs from outside and central PRD influence the central area of Guangzhou-Foshan and the western Jiangmen significantly while BVOCs from rural PRD mainly influence the western Jiangmen. The impacts of BVOC emissions on surface ozone differ in different PRD cities, and the impact varies in different seasons. Foshan and Jiangmen being most affected in autumn, result in 6.0 ppb and 5.5 ppb increases in surface ozone concentrations, while Guangzhou and Huizhou become more affected in summer. Three additional experiments concerning the sensitivity of surface ozone to MEGAN input variables show that surface ozone is more sensitive to landcover change, followed by emission factors and meteorology.« less

Field-analysis of potable water quality and ozone efficiency in ozone-assisted biological filtration systems for surface water treatment.

PubMed

Zanacic, Enisa; Stavrinides, John; McMartin, Dena W

2016-11-01

Potable water treatment in small communities is challenging due to a complexity of factors starting with generally poor raw water sources, a smaller tax and consumption base that limit capital and operating funds, and culminating in what is typically a less sophisticated and robust water treatment plant for production and delivery of safe, high quality potable water. The design and optimization of modular ozone-assisted biological filtration systems can address some of these challenges. In surface water treatment, the removal of organic matter (e.g., dissolved organic carbon - DOC), inorganic nutrients and other exposure-related contaminants (e.g., turbidity and dissolved solids) from the raw water source is essential. Thus, a combination of chemical and biological oxidation processes can produce an effective and efficient water treatment plant design that is also affordable and robust. To that end, the ozone-assisted biological filtration water treatment plants in two communities were evaluated to determine the efficacy of oxidation and contaminant removal processes. The results of testing for in-field system performance indicate that plant performance is particularly negatively impacted by high alkalinity, high organics loading, and turbidity. Both bicarbonate and carbonate alkalinity were observed to impede ozone contact and interaction with DOC, resulting in lower than anticipated DOC oxidation efficiency and bioavailability. The ozone dosage at both water treatment plants must be calculated on a more routine basis to better reflect both the raw water DOC concentration and presence of alkalinities to ensure maximized organics oxidation and minimization of trihalomethanes production. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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 and 722.8 ± 87.3 Tg O3 yr-1 globally. The new estimate of the ocean component is approximately a third of the current model estimates. This reduction corresponds to an approximately 20 % decrease in the total global ozone dry deposition, which (with all other components being unchanged) is equivalent to an increase of approximately 5 % in the modelled tropospheric ozone burden and a similar increase in tropospheric ozone lifetime.

On the variability of tropospheric ozone in the Tropical Eastern Pacific and its impact on the oxidizing capacity

NASA Astrophysics Data System (ADS)

Saiz-Lopez, A.; Gomez Martin, J.; Hay, T.; Mahajan, A.; Ordoñez, C.; Parrondo Sempere, M.; Gil, M. J.; Agama Reyes, M.; Paredes Mora, J.; Voemel, H.

2012-12-01

Observations of surface ozone, NOx and meteorological variables were made during two ground based field campaigns in the Eastern Pacific marine boundary layer (MBL). The first study was PIQUERO (Primera Investigación de la Química, Evolución y Reparto de Ozono), running from September 2000 to July 2001 in parallel to the Southern Hemisphere ADditional OZonesondes (SHADOZ) in the Galápagos Islands. The second study is the Climate and HAlogen Reactivity tropicaL EXperiment (CHARLEX), running from September 2010 to present. These long-term, high frequency, measurements enable a detailed description of the daily, monthly, seasonal and interannual variability of ozone and help to constrain the MBL and lower free troposphere (FT) ozone budget. In the Equatorial Eastern Pacific "cold season" (August - October), net ozone photochemical destruction of ~ 2 ppb day-1 occurs in the MBL (~30% due to halogens, and the rest to HOx). Ozone recovers by entrainment from aloft at night. The monthly baseline is set by the tropical instability waves (TIW), which also impact the ozone concentration in the lower FT. In the cold phase of the TIWs the MBL is stratified and, apart from higher surface ozone, it may also contain an upper drier layer with higher ozone between ~ 500 m and the main inversion at ~1 km. In the warm phase the buoyant MBL expands upwards (as much as 500 m) and poor ozone air reaches the FT. As the system shifts to the warm season (February- April), the TIWs stop and the sea becomes warmer, increasing evaporation and reducing ozone. The inversion is pushed upwards and finally disappears or becomes very weak. Surface ozone is so low that even at the low background NOx levels observed ozone production balances photochemical destruction, so the daily profile is flat (observed local effects in the populated areas of Galapagos are discussed). In February Galapagos is almost in the doldrums because the Inter-Tropical Convergence Zone (ITCZ) shifts south. In this situation, air convected at the ITZC is advected at different heights in the FT over Galapagos, so the entrainment of air from the FT does not replenish MBL ozone, explaining the low seasonal minimum. An important aspect of the marked ozone seasonal cycle is the impact on OH. levels. The consequences of this for the oxidizing capacity of the lower atmosphere are discussed.

Seasonal and diurnal variations of ozone at a high-altitude mountain baseline station in East Asia

NASA Astrophysics Data System (ADS)

Ou Yang, Chang-Feng; Lin, Neng-Huei; Sheu, Guey-Rong; Lee, Chung-Te; Wang, Jia-Lin

2012-01-01

Continuous measurements of tropospheric ozone were conducted at the Lulin Atmospheric Background Station (LABS) at an altitude of 2862 m from April 2006 to the end of 2009. Distinct seasonal variations in the ozone concentration were observed at the LABS, with a springtime maximum and a summertime minimum. Based on a backward trajectory analysis, CO data, and ozonesondes, the springtime maximum was most likely caused by the long-range transport of air masses from Southeast Asia, where biomass burning was intense in spring. In contrast, a greater Pacific influence contributed to the summertime minimum. In addition to seasonal variations, a distinct diurnal pattern was also observed at the LABS, with a daytime minimum and a nighttime maximum. The daytime ozone minimum was presumably caused by sinks of dry deposition and NO titration during the up-slope transport of surface air. The higher nighttime values, however, could be the result of air subsidence at night bringing ozone aloft to the LABS. After filtering out the daytime data to remove possible local surface contributions, the average background ozone value for the period of 2006-2009 was approximately 36.6 ppb, increased from 32.3 ppb prior to data filtering, without any changes in the seasonal pattern. By applying HYSPLIT4 model analysis, the origins of the air masses contributing to the background ozone observed at the LABS were investigated.

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

DOE PAGES

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.; ...

2017-01-01

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 +more » 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.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marelle, Louis; Raut, Jean-Christophe; Law, Kathy S.

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 +more » 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.« less

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

NASA Astrophysics Data System (ADS)

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.

An evaluation of the regional acid deposition model surface module for ozone uptake at three sites in the San Joaquin Valley of California

NASA Technical Reports Server (NTRS)

Massman, W. J.; Pederson, J.; Delany, A.; Grantz, D.; Hertog, G. Den; Neumann, H. H.; Oncley, S. P.; Pearson, R., Jr.; Shaw, R. H.

1994-01-01

Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day for at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated.

Analysis of European ozone trends in the period 1995-2014

NASA Astrophysics Data System (ADS)

Yan, Yingying; Pozzer, Andrea; Ojha, Narendra; Lin, Jintai; Lelieveld, Jos

2018-04-01

Surface-based measurements from the EMEP and Airbase networks are used to estimate the changes in surface ozone levels during the 1995-2014 period over Europe. We find significant ozone enhancements (0.20-0.59 µg m-3 yr-1 for the annual means; P-value < 0.01 according to an F-test) over the European suburban and urban stations during 1995-2012 based on the Airbase sites. For European background ozone observed at EMEP sites, it is shown that a significantly decreasing trend in the 95th percentile ozone concentrations has occurred, especially at noon (0.9 µg m-3 yr-1; P-value < 0.01), while the 5th percentile ozone concentrations continued to increase with a trend of 0.3 µg m-3 yr-1 (P-value < 0.01) during the study period. With the help of numerical simulations performed with the global chemistry-climate model EMAC, the importance of anthropogenic emissions changes in determining these changes over background sites are investigated. The EMAC model is found to successfully capture the observed temporal variability in mean ozone concentrations, as well as the contrast in the trends of 95th and 5th percentile ozone over Europe. Sensitivity simulations and statistical analysis show that a decrease in European anthropogenic emissions had contrasting effects on surface ozone trends between the 95th and 5th percentile levels and that background ozone levels have been influenced by hemispheric transport, while climate variability generally regulated the inter-annual variations of surface ozone in Europe.

Impact of surface ozone interactions on indoor air chemistry: A modeling study.

PubMed

Kruza, M; Lewis, A C; Morrison, G C; Carslaw, N

2017-09-01

An INdoor air Detailed Chemical Model was developed to investigate the impact of ozone reactions with indoor surfaces (including occupants), on indoor air chemistry in simulated apartments subject to ambient air pollution. The results are consistent with experimental studies showing that approximately 80% of ozone indoors is lost through deposition to surfaces. The human body removes ozone most effectively from indoor air per square meter of surface, but the most significant surfaces for C 6 -C 10 aldehyde formation are soft furniture and painted walls owing to their large internal surfaces. Mixing ratios of between 8 and 11 ppb of C 6 -C 10 aldehydes are predicted to form in apartments in various locations in summer, the highest values are when ozone concentrations are enhanced outdoors. The most important aldehyde formed indoors is predicted to be nonanal (5-7 ppb), driven by oxidation-derived emissions from painted walls. In addition, ozone-derived emissions from human skin were estimated for a small bedroom at nighttime with concentrations of nonanal, decanal, and 4-oxopentanal predicted to be 0.5, 0.7, and 0.7 ppb, respectively. A detailed chemical analysis shows that ozone-derived surface aldehyde emissions from materials and people change chemical processing indoors, through enhanced formation of nitrated organic compounds and decreased levels of oxidants. © 2017 The Authors. Indoor Air Published by John Wiley & Sons Ltd.

CORONA DISCHARGE REACTOR FOR SELECTIVE OXIDATION OF ALCOHOLS AND HYDROCARBONS USING OZONATION AND PHOTOXIDATION OF OVER TIO2

EPA Science Inventory

We have developed a process that combines the use of surface corona for the production of ozone by passing air or oxygen through a high voltage electrical discharge and the emitted UV is being used to activate a photocatalyst. A thin film of nanostructured TiO2 with primary part...

Global Radiative Forcing of Coupled Tropospheric Ozone and Aerosols in a Unified General Circulation Model

NASA Technical Reports Server (NTRS)

Liao, Hong; Seinfeld, John H.; Adams, Peter J.; Mickley, Loretta J.

2008-01-01

Global simulations of sea salt and mineral dust aerosols are integrated into a previously developed unified general circulation model (GCM), the Goddard Institute for Space Studies (GISS) GCM II', that simulates coupled tropospheric ozone-NOx-hydrocarbon chemistry and sulfate, nitrate, ammonium, black carbon, primary organic carbon, and secondary organic carbon aerosols. The fully coupled gas-aerosol unified GCM allows one to evaluate the extent to which global burdens, radiative forcing, and eventually climate feedbacks of ozone and aerosols are influenced by gas-aerosol chemical interactions. Estimated present-day global burdens of sea salt and mineral dust are 6.93 and 18.1 Tg with lifetimes of 0.4 and 3.9 days, respectively. The GCM is applied to estimate current top of atmosphere (TOA) and surface radiative forcing by tropospheric ozone and all natural and anthropogenic aerosol components. The global annual mean value of the radiative forcing by tropospheric ozone is estimated to be +0.53 W m(sup -2) at TOA and +0.07 W m(sup -2) at the Earth's surface. Global, annual average TOA and surface radiative forcing by all aerosols are estimated as -0.72 and -4.04 W m(sup -2), respectively. While the predicted highest aerosol cooling and heating at TOA are -10 and +12 W m(sup -2) respectively, surface forcing can reach values as high as -30 W m(sup -2), mainly caused by the absorption by black carbon, mineral dust, and OC. We also estimate the effects of chemistry-aerosol coupling on forcing estimates based on currently available understanding of heterogeneous reactions on aerosols. Through altering the burdens of sulfate, nitrate, and ozone, heterogeneous reactions are predicted to change the global mean TOA forcing of aerosols by 17% and influence global mean TOA forcing of tropospheric ozone by 15%.

Ozone Transport Aloft Drives Surface Ozone Maxima Across the Mojave Desert

NASA Astrophysics Data System (ADS)

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.

Ozone-initiated chemistry in an occupied simulated aircraft cabin.

PubMed

Weschler, Charles J; Wisthaler, Armin; Cowlin, Shannon; Tamás, Gyöngyi; Strøm-Tejsen, Peter; Hodgson, Alfred T; Destaillats, Hugo; Herrington, Jason; Zhang, Junfeng; Nazaroff, William W

2007-09-01

We have used multiple analytical methods to characterize the gas-phase products formed when ozone was added to cabin air during simulated 4-hour flights that were conducted in a reconstructed section of a B-767 aircraft containing human occupants. Two separate groups of 16 females were each exposed to four conditions: low air exchange (4.4 (h-1)), <2 ppb ozone; low air exchange, 61-64 ppb ozone; high air exchange (8.8 h(-1)), <2 ppb ozone; and high air exchange, 73-77 ppb ozone. The addition of ozone to the cabin air increased the levels of identified byproducts from approximately 70 to 130 ppb at the lower air exchange rate and from approximately 30 to 70 ppb at the higher air exchange rate. Most of the increase was attributable to acetone, nonanal, decanal, 4-oxopentanal (4-OPA), 6-methyl-5-hepten-2-one (6-MHO), formic acid, and acetic acid, with 0.25-0.30 mol of quantified product volatilized per mol of ozone consumed. Several of these compounds reached levels above their reported odor thresholds. Most byproducts were derived from surface reactions with occupants and their clothing, consistent with the inference that occupants were responsible for the removal of >55% of the ozone in the cabin. The observations made in this study have implications for other indoor settings. Whenever human beings and ozone are simultaneously present, one anticipates production of acetone, nonanal, decanal, 6-MHO, geranyl acetone, and 4-OPA.

Efficiency enhancement of silicon nanowire solar cells by using UV/Ozone treatments and micro-grid electrodes

NASA Astrophysics Data System (ADS)

Chen, Junyi; Subramani, Thiyagu; Sun, Yonglie; Jevasuwan, Wipakorn; Fukata, Naoki

2018-05-01

Silicon nanowire solar cells were fabricated by metal catalyzed electroless etching (MCEE) followed by thermal chemical vapor deposition (CVD). In this study, we investigated two effects, a UV/ozone treatment and the use of a micro-grid electrodes, to enhance light absorption and reduce the optic losses in the solar cell device. The UV/ozone treatment successfully improved the conversion efficiency. The micro-grid electrodes were then applied in solar cell devices subjected to a back surface field (BSF) treatment and rapid thermal annealing (RTA). These effects improved the conversion efficiency from 9.4% to 10.9%. Moreover, to reduce surface recombination and improve the continuity of front electrodes, we optimized the etching time of the MCEE process, giving a high efficiency of 12.3%.

Using Tropospheric Ozone Profiles and Surface Data (2004 - 2012) to Determine Background Ozone Levels in Houston, Texas

NASA Astrophysics Data System (ADS)

Spychala, M. D.; Morris, G. A.; Lefer, B. L.; Rappenglueck, B.; Cohan, D. S.; zhou, W.

2012-12-01

The Tropospheric Ozone Pollution Project (TOPP) at Rice University (2004 - 2006) and the University of Houston (2006 - present) has gathered > 400 profiles of ozone, temperature, pressure, and relative humidity, and > 250 of those also have wind speed and wind direction near the core of the City of Houston, Texas. Houston continues to be plagued with difficulty in coming into compliance with EPA National Ambient Air Quality Standards (NAAQS) due to a combination of its geographic location, large commuter population, significant petrochemical and energy production, and favorable weather patterns. An outstanding question remains the relative partitioning of ozone between local and remote, anthropogenic and natural sources. In this presentation, we use TOPP ozone profiles to determine a "background" ozone concentration and compare this measure with surface monitor "background" ozone as determined from upwind and downwind Continuous Air Monitoring Stations (CAMS) in an effort to further our understanding of this partitioning. For periods studied with the Community Multiscale Air Quality (CMAQ) Model, we also compare the sonde and surface "background" ozone with that suggested by the model.

Evaluating the Vertical Distribution of Ozone and its Relationship to Pollution Events in Air Quality Models using Satellite Data

NASA Astrophysics Data System (ADS)

Osterman, G. B.; Neu, J. L.; Eldering, A.; Pinder, R. W.; Tang, Y.; McQueen, J.

2014-12-01

Most regional scale models that are used for air quality forecasts and ozone source attribution do not adequately capture the distribution of ozone in the mid- and upper troposphere, but it is unclear how this shortcoming relates to their ability to simulate surface ozone. We combine ozone profile data from the NASA Earth Observing System (EOS) Tropospheric Emission Spectrometer (TES) and a new joint product from TES and the Ozone Monitoring Instrument along with ozonesonde measurements and EPA AirNow ground station ozone data to examine air quality events during August 2006 in the Community Multi-Scale Air Quality (CMAQ) and National Air Quality Forecast Capability (NAQFC) models. We present both aggregated statistics and case-study analyses with the goal of assessing the relationship between the models' ability to reproduce surface air quality events and their ability to capture the vertical distribution of ozone. We find that the models lack the mid-tropospheric ozone variability seen in TES and the ozonesonde data, and discuss the conditions under which this variability appears to be important for surface air quality.

Molecular and Immunological Characterization of Ragweed (Ambrosia artemisiifolia L.) Pollen after Exposure of the Plants to Elevated Ozone over a Whole Growing Season

PubMed Central

Kanter, Ulrike; Heller, Werner; Durner, Jörg; Winkler, J. Barbro; Engel, Marion; Behrendt, Heidrun; Holzinger, Andreas; Braun, Paula; Hauser, Michael; Ferreira, Fatima; Mayer, Klaus; Pfeifer, Matthias; Ernst, Dieter

2013-01-01

Climate change and air pollution, including ozone is known to affect plants and might also influence the ragweed pollen, known to carry strong allergens. We compared the transcriptome of ragweed pollen produced under ambient and elevated ozone by 454-sequencing. An enzyme-linked immunosorbent assay (ELISA) was carried out for the major ragweed allergen Amb a 1. Pollen surface was examined by scanning electron microscopy and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), and phenolics were analysed by high-performance liquid chromatography. Elevated ozone had no influence on the pollen size, shape, surface structure or amount of phenolics. ATR-FTIR indicated increased pectin-like material in the exine. Transcriptomic analyses showed changes in expressed-sequence tags (ESTs), including allergens. However, ELISA indicated no significantly increased amounts of Amb a 1 under elevated ozone concentrations. The data highlight a direct influence of ozone on the exine components and transcript level of allergens. As the total protein amount of Amb a 1 was not altered, a direct correlation to an increased risk to human health could not be derived. Additional, the 454-sequencing contributes to the identification of stress-related transcripts in mature pollen that could be grouped into distinct gene ontology terms. PMID:23637846

Impact of Tropospheric Ozone on Summer Climate in China

NASA Astrophysics Data System (ADS)

Li, Shu; Wang, Tijian; Zanis, Prodromos; Melas, Dimitris; Zhuang, Bingliang

2018-04-01

The spatial distribution, radiative forcing, and climatic effects of tropospheric ozone in China during summer were investigated by using the regional climate model RegCM4. The results revealed that the tropospheric ozone column concentration was high in East China, Central China, North China, and the Sichuan basin during summer. The increase in tropospheric ozone levels since the industrialization era produced clear-sky shortwave and clear-sky longwave radiative forcing of 0.18 and 0.71 W m-2, respectively, which increased the average surface air temperature by 0.06 K and the average precipitation by 0.22 mm day-1 over eastern China during summer. In addition, tropospheric ozone increased the land-sea thermal contrast, leading to an enhancement of East Asian summer monsoon circulation over southern China and a weakening over northern China. The notable increase in surface air temperature in northwestern China, East China, and North China could be attributed to the absorption of longwave radiation by ozone, negative cloud amount anomaly, and corresponding positive shortwave radiation anomaly. There was a substantial increase in precipitation in the middle and lower reaches of the Yangtze River. It was related to the enhanced upward motion and the increased water vapor brought by strengthened southerly winds in the lower troposphere.

Mitigation of global cooling by stratospheric chemistry feedbacks in a simulation of the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Noda, S.; Kodera, K.; Deushi, M.; Kitoh, A.; Mizuta, R.; Yoshida, K.; Murakami, S.; Adachi, Y.; Yoden, S.

2017-12-01

A series of numerical simulations of the Last Glacial Maximum (21 kyr B.P.) climate are performed by using an Earth System Model of the Meteorological Research Institute of the Japan Meteorological Agency to investigate the impact of stratospheric ozone profile on the surface climate with decreased CO2 condition and different orbital parameters. The contribution of the interactive ozone chemistry reveals a significant anomaly of +0.5 K (approximately 20 %) in the tropics and up to +1.5 K in high-latitudes for the annual mean zonal mean surface air temperature compared with those of the corresponding experiments with a prescribed ozone profile for preindustrial simulation of the fifth Coupled Model Intercomparison Project (CMIP5). In the tropics, this mitigation of global cooling is related to longwave radiative feedbacks associated with circulation-driven increases in lower stratospheric ozone and related increase in stratospheric water vapor and related decrease in cirrus cloud. The relations are opposite signs to and consistent with those of a global warming simulation. In high-latitudes, the polar amplification of mitigation of cooling associated with the change of sea ice area that is the same sign to and consistent with our previous paleoclimate simulation in the mid-Holocene (6 kyr B.P.). We recommend that climate models include sea ice and ozone profile that are consistent with CO2 concentration.

Lower tropospheric ozone over India and its linkage to the South Asian monsoon

NASA Astrophysics Data System (ADS)

Lu, Xiao; Zhang, Lin; Liu, Xiong; Gao, Meng; Zhao, Yuanhong; Shao, Jingyuan

2018-03-01

Lower tropospheric (surface to 600 hPa) ozone over India poses serious risks to both human health and crops, and potentially affects global ozone distribution through frequent deep convection in tropical regions. Our current understanding of the processes controlling seasonal and long-term variations in lower tropospheric ozone over this region is rather limited due to spatially and temporally sparse observations. Here we present an integrated process analysis of the seasonal cycle, interannual variability, and long-term trends of lower tropospheric ozone over India and its linkage to the South Asian monsoon using the Ozone Monitoring Instrument (OMI) satellite observations for years 2006-2014 interpreted with a global chemical transport model (GEOS-Chem) simulation for 1990-2010. OMI observed lower tropospheric ozone over India averaged for 2006-2010, showing the highest concentrations (54.1 ppbv) in the pre-summer monsoon season (May) and the lowest concentrations (40.5 ppbv) in the summer monsoon season (August). Process analyses in GEOS-Chem show that hot and dry meteorological conditions and active biomass burning together contribute to 5.8 Tg more ozone being produced in the lower troposphere in India in May than January. The onset of the summer monsoon brings ozone-unfavorable meteorological conditions and strong upward transport, which all lead to large decreases in the lower tropospheric ozone burden. Interannually, we find that both OMI and GEOS-Chem indicate strong positive correlations (r = 0.55-0.58) between ozone and surface temperature in pre-summer monsoon seasons, with larger correlations found in high NOx emission regions reflecting NOx-limited production conditions. Summer monsoon seasonal mean ozone levels are strongly controlled by monsoon strengths. Lower ozone concentrations are found in stronger monsoon seasons mainly due to less ozone net chemical production. Furthermore, model simulations over 1990-2010 estimate a mean annual trend of 0.19 ± 0.07 (p value < 0.01) ppbv yr-1 in Indian lower tropospheric ozone over this period, which are mainly driven by increases in anthropogenic emissions with a small contribution (about 7 %) from global methane concentration increases.

Enhanced near-surface ozone under heatwave conditions in a Mediterranean island.

PubMed

Pyrgou, Andri; Hadjinicolaou, Panos; Santamouris, Mat

2018-06-15

Near-surface ozone is enhanced under particular chemical reactions and physical processes. This study showed the seasonal variation of near-surface ozone in Nicosia, Cyprus and focused in summers when the highest ozone levels were noted using a seven year hourly dataset from 2007 to 2014. The originality of this study is that it examines how ozone levels changed under heatwave conditions (defined as 4 consecutive days with daily maximum temperature over 39 °C) with emphasis on specific air quality and meteorological parameters with respect to non-heatwave summer conditions. The influencing parameters had a medium-strong positive correlation of ozone with temperature, UVA and UVB at daytime which increased by about 35% under heatwave conditions. The analysis of the wind pattern showed a small decrease of wind speed during heatwaves leading to stagnant weather conditions, but also revealed a steady diurnal cycle of wind speed reaching a peak at noon, when the highest ozone levels were noted. The negative correlation of NOx budget with ozone was further increased under heatwave conditions leading to steeper lows of ozone in the morning. In summary, this research encourages further analysis into the persistent weather conditions prevalent during HWs stimulating ozone formation for higher temperatures.

Vertical Distribution of Non-Methane Hydrocarbons During Winter Ozone Production Events in the Uintah Basin

NASA Astrophysics Data System (ADS)

Stephens, C. R.; Helmig, D.; Evans, J.; Hueber, J.; Park, J.; Boylan, P.

2013-12-01

Emissions of non-methane hydrocarbons (NMHC) are primarily linked to anthropogenic fossil fuel activities, such as oil and natural gas extraction and distribution, and are important tropospheric ozone precursors. The Uintah Basin, Utah, is a region of heavy oil and natural gas development where high winter-time ozone production events have been observed during strong inversions when there is snow cover present. In the winters of 2012 and 2013, we conducted measurements of methane and NMHC during the Uintah Basin Winter Ozone Study. NMHC were monitored along a vertical gradient up to 150 m using a flux tower and tethered balloon. In 2013, measurements of NMHC were also conducted from within the snowpack. In 2012, no high ozone events were observed. In contrast, during the 2013 study, several periods of high ozone occurred concurrently with strong increases in ambient NMHC. Here, we present vertical profile measurements of C2-C5 alkanes, benzene and toluene comparing 2012 and 2013. Data from 2013 show strong vertical gradients with build-up of NMHC and ozone near the surface during inversion events, with wash out of both ozone and ozone precursors during low pressure front passage from the west. The NOAA/INSTAAR global flask network provides a useful comparison for expected regional background values of NMHC, and we find up to a 570-fold enhancement in Uintah, providing evidence for the importance of local emissions sources. Investigation of NMHC ratios reveals distinctly different values in the ambient air and within the snowpack, suggesting active radical chemistry occurring in the snow. Analysis of butane and pentane isomer ratios points towards the presence of chlorine radicals, indicating that the snow may serve as a reactive chlorine reservoir that may enhance ozone production chemistry.

Meteorological air quality forecasting using the WRF-Chem model during the LMOS2017 field campaign

NASA Astrophysics Data System (ADS)

Stanier, C. O.; Abdioskouei, M.; Carmichael, G. R.; Christiansen, M.; Sobhani, N.

2017-12-01

The Lake Michigan Ozone Study (LMOS 2017) occurred during May and June 2017 to address the high ozone episodes in coastal communities surrounding Lake Michigan. Aircraft, ship, mobile lab, and ground-based stations were used in this campaign to build an extensive dataset regarding ozone, its precursors, and particulate matter. The University of Iowa produced high-resolution (4x4 km2 horizontal resolution and 53 vertical levels) forecast products using the WRF-Chem modeling system in support of experimental planning during LMOS 2017. The base forecast system used WRF-Chem 3.6.1 and updated National Emission Inventory (NEI-2011v2). In the updated NEI-2011v2, we reduced the NOx emissions by 28% based on EPA's estimated NOx trends from 2011 to 2017. We ran another daily forecast (perturbed forecast) with 50% reduced NOx emission to capture the sensitivity of ozone to NOx emission and account for the impact of weekend emissions on ozone values. Preliminary in-field evaluation of model performance for clouds, on-shore flows, and surface and aircraft sampled ozone and NOx concentrations found that the model successfully captured much of the observed synoptic variability of onshore flows. The model captured the variability of O3 well, but underpredicted peak ozone during high O3 episodes. In post-campaign WRF-Chem simulations, we investigated the sensitivity of the model to the hydrocarbon emission.

Spatial and temporal variation of surface ozone, NO and NO₂ at urban, suburban, rural and industrial sites in the southwest of the Iberian Peninsula.

PubMed

Domínguez-López, D; Adame, J A; Hernández-Ceballos, M A; Vaca, F; De la Morena, B A; Bolívar, J P

2014-09-01

Surface ozone is one of the most important photochemical pollutants in the low atmosphere, causing damage to human health, vegetation, materials and climate. The weather (high temperatures and high solar radiation), orography (presence of the Guadalquivir valley) and anthropogenic (the cities of Cádiz, Córdoba, Huelva and Seville and two important industrial complexes) characteristics of the southwestern Iberian Peninsula make this region ideal for the formation and accumulation of ozone. To increase the knowledge of ozone behaviour in this area, the monthly, daily and weekly variations of ozone and its precursors, nitrogen oxides (NO(x) = NO + NO2), were analysed over a 4-year period (2003 to 2006). Using the k-means cluster technique, 12 representative stations of five different areas with different ozone behaviour were selected from a total of 29 monitoring sites. This is the first time that the analysis of these atmospheric pollutants has been carried out for the whole area, allowing therefore a complete understanding of the dynamics and the relationships of these compounds in this region. The results showed an opposite behaviour among ozone and NO and NO2 concentrations in urban and suburban zones, marked by maximums of ozone (minimums NO(x)) in spring and summer and minimums (maximums) in autumn and winter. A seasonal behaviour, with lower amplitude, was also observed in rural and industrial areas for ozone concentrations, with the NO and NO2 concentrations remaining at low and similar values during the year in rural zones due to the absence of emission sources in their surroundings. The daily cycles of ozone in urban, suburban and industrial sites registered a maximum value in the early afternoon (14:00-17:00 UTC) while for NOx two peaks were observed, at 7:00-10:00 UTC and 20:00-22:00. In the case of rural stations, no hourly peak of ozone or NO(x) was registered. The weekend effect was studied by using a statistical contrast tests (Student's t). The results indicated that only areas influenced by important traffic emissions presented a weekend effect for NO and NO2, whereas an ozone weekend effect was not detected in any case.

Ozone in the marine boundary layer of Bay of Bengal and Arabian Sea during post winter period - continental influence

NASA Astrophysics Data System (ADS)

Nair, Prabha R.; George, Susan K.; David, Liji Mary; Parameswaran, Krishnaswamy

Ozone plays a key role in controlling the oxidation capacity of the troposphere and hence the lifetime of a variety of trace gases in the atmosphere. In pristine marine boundary layer (MBL), entire chemistry is initiated by the photolysis of ozone and the subsequent formation of OH radical from water vapour. Also in such environment, photochemical destruction is considered as a major sink in global ozone budget. Even though large number of studies on near surface ozone has been carried out over land such studies are very few over oceanic environments. This paper presents the observational results on the spatial variations of near-surface ozone over Bay of Bengal and Arabian Sea as revealed by the cruise-based measurements (cruise No. SK223) conducted as part of Integrated Campaign for Aerosol gases and Radiation Budget (ICARB) under the Geosphere Biosphere Programme of Indian Space Research Organisation (IGBP). Online measurements of ozone have been carried out by using a UV Photometric Analyser (model 49C of Thermo Electron Corporation, USA). Ozone mixing ratio was observed to be significantly high over northern Bay of Bengal (20-28 ppb) compared to southern Bay of Bengal and Arabian Sea. Minimum levels of ozone ( 5 ppb) have been measured in the central Bay of Bengal region. Over Arabian Sea latitudinal variation was not prominently observed. The over all latitudinal gradient is estimated to be 1.2 ppb/o latitude over Bay of Bengal with longitudinal gradient showing variation depending on the latitude sector. It was maximum (of 1.2ppb/o longitude) over the mid Bay of Bengal region ( 15o N). Longitudinal variation was not significant over northern and southern regions. A close examination of surface airflow patterns and the air mass back trajectories revealed increase in ozone level associated with continental outflow from the northern and central parts of the subcontinent. The diurnal pattern also showed variations depending on the proximity to inhabited land mass and also with meteorological parameters.

Ozone studies in the Paso del Norte region

NASA Astrophysics Data System (ADS)

Becerra-Davila, Fernando

The Paso del Norte region forms the largest contiguous bi-national conglomerate on the US-Mexico border. With a combined population of around 2 million inhabitants, the Paso del Norte region is isolated, more than 500 km away from the nearest urban area of comparable size, thus making it an ideal location for air quality studies of an isolated urban environment. The meteorological conditions leading to a high ozone episode in this region, such as the historical ozone episode of June 2006, are analyzed. It is well known that stagnation and minimal winds, high temperatures, and pressure ridges over the region are conducive to high ozone episodes. In addition, the planetary boundary height is studied to understand its impact on high ozone episodes. Several studies report that ground level ozone non-attainment regulations could be caused not only by local emissions, but also by atmospheric transport. In this work the atmospheric advection of pollutants into the region is analyzed using HYSPLIT backward trajectories. Furthermore, a novel backward trajectory clustering technique is implemented for the summer of 2006. The "ozone weekend effect" (OWE) is a phenomenon by which in some geographical regions ambient ozone concentrations tend to be higher on weekends than on weekdays, despite the lower emissions of ozone precursors during those days. The observed local OWE has never previously been studied in terms of the photolysis rates of four of the main ozone precursors. In this research a novel method that allows the calculation of actinic fluxes, photolysis frequencies and photolysis rates with a high degree of accuracy and reliability has been developed. This method utilizes a combination of the experimental data available for this region in conjunction with a radiative transfer model (TUV model). Three weekend-weekday cases during summers 2006, 2009 and 2010 are studied in this work. In this research, the photolysis impact on the local OWE is studied. The results obtained from this photolysis study demonstrate that the local ground level ozone formation is not only influenced by the strong solar radiation and changing aerosol makeup, but also by other heterogeneous factors and reactions. In addition, this research provided good evidence that the ground level ozone precursor regime in El Paso during the ozone episode of June 2006 was mostly VOC-limited. Much of this estimation was derived from measurements of local ambient VOC/NOx ratios. This finding shows that at least during June 2006, the non-linear surface ozone production increased during weekends compared to workdays in a habitually VOC-limited regime. The seasonal variations of columnar ozone as measured by a Multi-filter Rotating Shadowband instrument installed at the UTEP campus are analyzed for the first time for this region and results are presented. This investigation has addressed the problem of ground-level ozone formation in the Paso del Norte region. Urban ozone is a complex problem with many aspects that are not fully understood. In this investigation, a range of techniques has been used to address the study of local surface ozone episodes with the purpose of acquiring new insights and knowledge that will help understand and remediate the diverse atmospheric pollution events that affect this bi-national region recurrently. Innovative techniques were developed and used, ranging from the use of local ambient atmospheric pollution data to the utilization of complex modeling techniques to achieve the best possible computer results. Finally, the influence of ground level ozone concentrations in admissions to hospitals for this region due to respiratory diseases is analyzed. The comprehensive results obtained in this work will help to better understand ozone formation in the Paso del Norte Region for future policy regulation implementations.

Using Ozone To Clean and Passivate Oxygen-Handling Hardware

NASA Technical Reports Server (NTRS)

Torrance, Paul; Biesinger, Paul

2009-01-01

A proposed method of cleaning, passivating, and verifying the cleanliness of oxygen-handling hardware would extend the established art of cleaning by use of ozone. As used here, "cleaning" signifies ridding all exposed surfaces of combustible (in particular, carbon-based) contaminants. The method calls for exposing the surfaces of the hardware to ozone while monitoring the ozone effluent for carbon dioxide. The ozone would passivate the hardware while oxidizing carbon-based residues, converting the carbon in them to carbon dioxide. The exposure to ozone would be continued until no more carbon dioxide was detected, signifying that cleaning and passivation were complete.

Analysis of Ozone And CO2 Profiles Measured At A Diary Facility

NASA Astrophysics Data System (ADS)

Ogunjemiyo, S. O.; Hasson, A. S.; Ashkan, S.; Steele, J.; Shelton, T.

2015-12-01

Ozone and carbon dioxide are both greenhouse gasses in the planetary boundary layer. Ozone is a harmful secondary pollutant in the troposphere produced mostly during the day when there is a photochemical reaction in which primary pollutant precursors such as nitrous oxide (NOx) or volatile organic compounds (VOC's) mix with sunlight. As with most pollutants in the lower troposphere, both ozone and carbon dioxide vary in spatial and temporal scale depending on sources of pollution, environmental conditions and the boundary layer dynamics. Among the several factors that influence ozone variation, the seasonal changes in meteorological parameters and availability of ozone precursors are crucial because they control ozone formation and decay. Understanding how the difference in emission sources affect vertical transport of ozone and carbon dioxide is considered crucial to the improvement of their regional inventory sources. The purpose of this study is to characterize vertical transport of ozone and carbon at a diary facility. The study was conducted in the summer of 2011 and 2012 at a commercial dairy facility in Central California and involved profile measurements of ozone and CO2 using electrochemical ozonesondes, meteorological sondes and CO2 probe tethered to a 9 cubic meters helium balloon. On each day of the data collection, multiple balloon launches were made over a period representing different stages of the boundary layer development. The results show ozone and CO2 profiles display different characteristics. Regardless of the time of the day, the CO2 concentration decreases with height with a sharp gradient near the surface that is strengthened by a stable atmospheric condition, a feature suggesting the surface as the source. On the other hand, ozone profiles show greater link to the evolution of the lower boundary layer. Ozone profiles display unique features indicating ozone destruction near the surface. This unusual near the surface, observed even in the afternoon when the boundary layer is fully developed, greatly contrast ozone profiles are typical of urban environment

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

NASA Astrophysics Data System (ADS)

Kujanpää, J.; Kalakoski, N.

2015-05-01

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 EUMETSAT's polar orbiting meteorological operational (Metop) satellites. The input total ozone product is generated by the German Aerospace Center (DLR) also within the O3M SAF framework. Polar orbiting satellites provide global coverage but infrequent sampling of the diurnal cloud cover. The diurnal variation of the surface UV radiation is extremely strong due to modulation by solar elevation and rapidly changing cloud cover. At the minimum, one sample of the cloud cover in the morning and another in the afternoon are needed to derive daily maximum and daily integrated surface UV radiation quantities. This is achieved by retrieving cloud optical depth from the channel 1 reflectance of the third Advanced Very High Resolution Radiometer (AVHRR/3) instrument aboard both Metop in the morning orbit (daytime descending node around 09:30 LT) and Polar Orbiting Environmental Satellites (POES) of the National Oceanic and Atmospheric Administration (NOAA) in the afternoon orbit (daytime ascending node around 14:30 LT). In addition, more overpasses are used at high latitudes where the swaths of consecutive orbits overlap. The input satellite data are received from EUMETSAT's Multicast Distribution System (EUMETCast) using commercial telecommunication satellites for broadcasting the data to the user community. The surface UV product includes daily maximum dose rates and integrated daily doses with different biological weighting functions, integrated UVB and UVA radiation, solar noon UV Index and daily maximum photolysis frequencies of ozone and nitrogen dioxide at the surface level. The quantities are computed in a 0.5° × 0.5° regular latitude-longitude grid and stored as daily files in the hierarchical data format (HDF5) within two weeks from sensing. The product files are archived in the O3M SAF distributed archive and can be ordered via the EUMETSAT Data Centre.

Ozone deposition velocities, reaction probabilities and product yields for green building materials

NASA Astrophysics Data System (ADS)

Lamble, S. P.; Corsi, R. L.; Morrison, G. C.

2011-12-01

Indoor surfaces can passively remove ozone that enters buildings, reducing occupant exposure without an energy penalty. However, reactions between ozone and building surfaces can generate and release aerosols and irritating and carcinogenic gases. To identify desirable indoor surfaces the deposition velocity, reaction probability and carbonyl product yields of building materials considered green (listed, recycled, sustainable, etc.) were quantified. Nineteen separate floor, wall or ceiling materials were tested in a 10 L, flow-through laboratory reaction chamber. Inlet ozone concentrations were maintained between 150 and 200 ppb (generally much lower in chamber air), relative humidity at 50%, temperature at 25 °C and exposure occurred over 24 h. Deposition velocities ranged from 0.25 m h -1 for a linoleum style flooring up to 8.2 m h -1 for a clay based paint; reaction probabilities ranged from 8.8 × 10 -7 to 6.9 × 10 -5 respectively. For all materials, product yields of C 1 thru C 12 saturated n-aldehydes, plus acetone ranged from undetectable to greater than 0.70 The most promising material was a clay wall plaster which exhibited a high deposition velocity (5.0 m h -1) and a low product yield (

Spatial distribution of ozone over Indonesia (Study case: Forest fire event 2015)

NASA Astrophysics Data System (ADS)

Muslimah, Sri; Buce Saleh, Muhamad; Hidayat, Rahmat

2018-05-01

Tropospheric ozone is known as surface ozone and caused several health impact. The objective of this study was to analysis spatial distribution of tropospheric ozone over Indonesia case study forest fire event in 2015. Monthly observation measured by Ozone Monitoring Instrument (OMI) have been analysed from January – December 2015 to study spatial distribution of tropospheric ozone related to forest fire event 2015. The study discovered high level of tropospheric column ozone (TCO) from October to November 2015. The result shows increasing average of TCO from September to October almost 6 DU. Meanwhile, monthly number of hotspot is higher in September 2015 with total number 257 hotspot which is acquired by Moderate Resolution Imaging Spectrometer (MODIS) Terra version 6.1 with confidence level same or more than 90%. The hotspot distribution compared with spatial TCO distribution and shows interesting time lag with respect to hotspot distribution, one month. Further study for daily comparison of TCO and forest fire event needed. This result suggested that the tropospheric ozone over the Indonesian region increases in 2015 were remarkable and corresponded to forest fire event.

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

DOE PAGES

Schultz, Martin G.; Schroder, Sabine; Lyapina, Olga; ...

2017-11-27

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 buildmore » 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 observation network both in terms of regions without monitoring, and in terms of regions that have monitoring programs but no public access to the data archive. Therefore future improvements to the database will require not only improved data harmonization, but also expanded data sharing and increased monitoring in data-sparse regions.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, Martin G.; Schroder, Sabine; Lyapina, Olga

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 buildmore » 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 observation network both in terms of regions without monitoring, and in terms of regions that have monitoring programs but no public access to the data archive. Therefore future improvements to the database will require not only improved data harmonization, but also expanded data sharing and increased monitoring in data-sparse regions.« less

Long-term trends of surface ozone and its influencing factors at the Mt Waliguan GAW station, China - Part 2: The roles of anthropogenic emissions and climate variability

NASA Astrophysics Data System (ADS)

Xu, Wanyun; Xu, Xiaobin; Lin, Meiyun; Lin, Weili; Tarasick, David; Tang, Jie; Ma, Jianzhong; Zheng, Xiangdong

2018-01-01

Inter-annual variability and long-term trends in tropospheric ozone are both environmental and climate concerns. Ozone measured at Mt Waliguan Observatory (WLG, 3816 m a.s.l.) on the Tibetan Plateau over the period of 1994-2013 has increased significantly by 0.2-0.3 ppbv yr-1 during spring and autumn but shows a much smaller trend in winter and no significant trend in summer. Here we explore the factors driving the observed ozone changes at WLG using backward trajectory analysis, chemistry-climate model hindcast simulations (GFDL AM3), a trajectory-mapped ozonesonde data set, and several climate indices. A stratospheric ozone tracer implemented in GFDL AM3 indicates that stratosphere-to-troposphere transport (STT) can explain ˜ 60 % of the simulated springtime ozone increase at WLG, consistent with an increase in the NW air-mass frequency inferred from the trajectory analysis. Enhanced STT associated with the strengthening of the mid-latitude jet stream contributes to the observed high ozone anomalies at WLG during the springs of 1999 and 2012. During autumn, observations at WLG are more heavily influenced by polluted air masses originating from South East Asia than in the other seasons. Rising Asian anthropogenic emissions of ozone precursors are the key driver of increasing autumnal ozone observed at WLG, as supported by the GFDL AM3 model with time-varying emissions, which captures the observed ozone increase (0.26 ± 0.11 ppbv yr-1). AM3 simulates a greater ozone increase of 0.38 ± 0.11 ppbv yr-1 at WLG in autumn under conditions with strong transport from South East Asia and shows no significant ozone trend in autumn when anthropogenic emissions are held constant in time. During summer, WLG is mostly influenced by easterly air masses, but these trajectories do not extend to the polluted regions of eastern China and have decreased significantly over the last 2 decades, which likely explains why summertime ozone measured at WLG shows no significant trend despite ozone increases in eastern China. Analysis of the Trajectory-mapped Ozonesonde data set for the Stratosphere and Troposphere (TOST) and trajectory residence time reveals increases in direct ozone transport from the eastern sector during autumn, which adds to the autumnal ozone increase. We further examine the links of ozone variability at WLG to the quasi-biennial oscillation (QBO), the East Asian summer monsoon (EASM), and the sunspot cycle. Our results suggest that the 2-3-, 3-7-, and 11-year periodicities are linked to the QBO, EASM index, and sunspot cycle, respectively. A multivariate regression analysis is performed to quantify the relative contributions of various factors to surface ozone concentrations at WLG. Through an observational and modelling analysis, this study demonstrates the complex relationships between surface ozone at remote locations and its dynamical and chemical influencing factors.

Improved Potential Energy Surface of Ozone Constructed Using the Fitting by Permutationally Invariant Polynomial Function

DOE PAGES

Ayouz, Mehdi; Babikov, Dmitri

2012-01-01

New global potential energy surface for the ground electronic state of ozone is constructed at the complete basis set level of the multireference configuration interaction theory. A method of fitting the data points by analytical permutationally invariant polynomial function is adopted. A small set of 500 points is preoptimized using the old surface of ozone. In this procedure the positions of points in the configuration space are chosen such that the RMS deviation of the fit is minimized. New ab initio calculations are carried out at these points and are used to build new surface. Additional points are added tomore » the vicinity of the minimum energy path in order to improve accuracy of the fit, particularly in the region where the surface of ozone exhibits a shallow van der Waals well. New surface can be used to study formation of ozone at thermal energies and its spectroscopy near the dissociation threshold.« less

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

NASA Technical Reports Server (NTRS)

Johnson, Matthew S.; Sullivan, John; Liu, Xiong; Zoogman, Peter; Newchurch, Mike; Kuang, Shi; McGee, Thomas; Leblanc, Thierry

2017-01-01

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 (Global Ozone Monitoring Experiment), GOME-2, and OMI (Ozone Monitoring Instrument). 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 (Global Modeling and Assimilation Office) operational GEOS-5 (Goddard Earth Observing System, Version 5) FP (Forecast Products) model and reanalysis data from MERRA2 (Modern-Era Retrospective analysis for Research and Applications, Version 2)) and a full chemical transport model (CTM), GEOS-Chem. In this study, vertical profile products are evaluated with surface (0-2 kilometers) and tropospheric (0-10 kilometers) TOLNet (Tropospheric Ozone Lidar Network) 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 TEMPO when compared to hourly and daily-averaged TOLNet observations. Furthermore, it is shown that when large surface O3 mixing ratios are observed, TEMPO retrieval values at the surface are most accurate when applying CTM a priori profile information compared to all other data products.

Investigating Ozone Sources in California Using AJAX Airborne Measurements and Models: Implications for Stratospheric Intrusion and Long Range Transport

NASA Technical Reports Server (NTRS)

Ryoo, Ju-Mee; Johnson, Matthew S.; Iraci, Laura T.; Yates, Emma L.; Pierce, R. Bradley; Tanaka, Tomoaki; Gore, Warren

2016-01-01

High ozone concentrations at low altitudes near the surface were detected from airborne Alpha Jet Atmospheric eXperiment (AJAX) measurements on May 30, 2012. We investigate the causes of the elevated ozone concentrations using the airborne measurements and various models. GEOSchem and WRF-STILT model simulations show that the contribution from local sources is small. From MERRA reanalysis, it is found that high potential vorticity (PV) is observed at low altitudes. This high PV appears to be only partially coming through the stratospheric intrusions because the air inside the high PV region is moist, which shows that mixing appears to be enhanced in the low altitudes. Considering that diabatic heating can also produce high PV in the lower troposphere, high ozone is partially coming through stratospheric intrusion, but this cannot explain the whole ozone concentration in the target areas of the western U.S. A back-trajectory model is utilized to see where the air masses originated. The air masses of the target areas came from the lower stratosphere (LS), upper (UT), mid- (MT), and lower troposphere (LT). The relative number of trajectories coming from LS and UT is low (7.7% and 7.6%, respectively) compared to that from LT (64.1%), but the relative ozone concentration coming from LS and UT is high (38.4% and 20.95%, respectively) compared to that from LT (17.7%). The air mass coming from LT appears to be mostly coming from Asia. Q diagnostics show that there is sufficient mixing along the trajectory to indicate that ozone from the different origins is mixed and transported to the western U.S. This study shows that high ozone concentrations can be detected by airborne measurements, which can be analyzed by integrated platforms such as models, reanalysis, and satellite data.

Investigation of Ozone Sources in California Using AJAX Airborne Measurements and Models: Implications for Stratospheric Intrusion and Long Range Transport

NASA Technical Reports Server (NTRS)

Ryoo, Ju-Mee; Johnson, Matthew S.; Iraci, Laura T.; Yates, Emma L.; Pierce, R. Bradley; Tanaka, Tomoaki; Gore, Warren

2015-01-01

High ozone concentrations at low altitudes near the surface were detected from airborne Alpha Jet Atmospheric eXperiment (AJAX) measurements on May 30, 2012. We investigate the causes of the elevated ozone concentrations using the airborne measurements and various models. GEOS-chem and WRF-STILT model simulations show that the contribution from local sources is small. From MERRA reanalysis, it is found that high potential vorticity (PV) is observed at low altitudes. This high PV appears to be only partially coming through the stratospheric intrusions because the air inside the high PV region is moist, which shows that mixing appears to be enhanced in the low altitudes. Considering that diabatic heating can also produce high PV in the lower troposphere, high ozone is partially coming through stratospheric intrusion, but this cannot explain the whole ozone concentration in the target areas of the western U.S. A back-trajectory model is utilized to see where the air masses originated. The air masses of the target areas came from the lower stratosphere (LS), upper (UT), mid- (MT), and lower troposphere (LT). The relative number of trajectories coming from LS and UT is low (7.7 and 7.6, respectively) compared to that from LT (64.1), but the relative ozone concentration coming from LS and UT is high (38.4 and 20.95, respectively) compared to that from LT (17.7). The air mass coming from LT appears to be mostly coming from Asia. Q diagnostics show that there is sufficient mixing along the trajectory to indicate that ozone from the different origins is mixed and transported to the western U.S. This study shows that high ozone concentrations can be detected by airborne measurements, which can be analyzed by integrated platforms such as models, reanalysis, and satellite data.

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

PubMed Central

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

Ozone reaction with clothing and its initiated VOC emissions in an environmental chamber.

PubMed

Rai, A C; Guo, B; Lin, C-H; Zhang, J; Pei, J; Chen, Q

2014-02-01

Human health is adversely affected by ozone and the volatile organic compounds (VOCs) produced from its reactions in the indoor environment. Hence, it is important to characterize the ozone-initiated reactive chemistry under indoor conditions and study the influence of different factors on these reactions. This investigation studied the ozone reactions with clothing through a series of experiments conducted in an environmental chamber under various conditions. The study found that the ozone reactions with a soiled (human-worn) T-shirt consumed ozone and generated VOCs. The ozone removal rate and deposition velocity for the T-shirt increased with the increasing soiling level and air change rate, decreased at high ozone concentrations, and were relatively unaffected by the humidity. The deposition velocity for the soiled T-shirt ranged from 0.15 to 0.29 cm/s. The ozone-initiated VOC emissions included C6-C10 straight-chain saturated aldehydes, acetone, and 4-OPA (4-oxopentanal). The VOC emissions were generally higher at higher ozone, humidity, soiling of T-shirt, and air change rate. The total molar yield was approximately 0.5 in most cases, which means that for every two moles of ozone removed by the T-shirt surface, one mole of VOCs was produced. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Williamson, James M.; Trump, Darryl D.; Bletzinger, Peter; Ganguly, Biswa N.

2006-10-01

A surface dielectric barrier discharge (DBD) in atmospheric pressure air was excited either by low frequency (0.3-2 kHz) high-voltage ac or by short, high-voltage pulses at repetition rates from 50 to 600 pulses s-1. The short-pulse excited discharge was more diffuse and did not have the pronounced bright multiple cathode spots observed in the ac excited discharge. The discharge voltage, current and average power deposited into the discharge were calculated for both types of excitation. As a measure of plasma-chemical efficiency, the ozone number density was measured by UV absorption as a function of average deposited power. The density of ozone produced by ac excitation did not increase so rapidly as that produced by short-pulse excitation as a function of average power, with a maximum measured density of ~3 × 1015 cm-3 at 25 W. The maximum ozone production achieved by short-pulse excitation was ~8.5 × 1015 cm-3 at 20 W, which was four times greater than that achieved by ac excitation at the same power level.

Current and future climate- and air pollution-mediated impacts on human health.

PubMed

Doherty, Ruth M; Heal, Mathew R; Wilkinson, Paul; Pattenden, Sam; Vieno, Massimo; Armstrong, Ben; Atkinson, Richard; Chalabi, Zaid; Kovats, Sari; Milojevic, Ai; Stevenson, David S

2009-12-21

We describe a project to quantify the burden of heat and ozone on mortality in the UK, both for the present-day and under future emission scenarios. Mortality burdens attributable to heat and ozone exposure are estimated by combination of climate-chemistry modelling and epidemiological risk assessment. Weather forecasting models (WRF) are used to simulate the driving meteorology for the EMEP4UK chemistry transport model at 5 km by 5 km horizontal resolution across the UK; the coupled WRF-EMEP4UK model is used to simulate daily surface temperature and ozone concentrations for the years 2003, 2005 and 2006, and for future emission scenarios. The outputs of these models are combined with evidence on the ozone-mortality and heat-mortality relationships derived from epidemiological analyses (time series regressions) of daily mortality in 15 UK conurbations, 1993-2003, to quantify present-day health burdens. During the August 2003 heatwave period, elevated ozone concentrations > 200 microg m-3 were measured at sites in London and elsewhere. This and other ozone photochemical episodes cause breaches of the UK air quality objective for ozone. Simulations performed with WRF-EMEP4UK reproduce the August 2003 heatwave temperatures and ozone concentrations. There remains day-to-day variability in the high ozone concentrations during the heatwave period, which on some days may be explained by ozone import from the European continent.Preliminary calculations using extended time series of spatially-resolved WRF-EMEP4UK model output suggest that in the summers (May to September) of 2003, 2005 & 2006 over 6000 deaths were attributable to ozone and around 5000 to heat in England and Wales. The regional variation in these deaths appears greater for heat-related than for ozone-related burdens.Changes in UK health burdens due to a range of future emission scenarios will be quantified. These future emissions scenarios span a range of possible futures from assuming current air quality legislation is fully implemented, to a more optimistic case with maximum feasible reductions, through to a more pessimistic case with continued strong economic growth and minimal implementation of air quality legislation. Elevated surface ozone concentrations during the 2003 heatwave period led to exceedences of the current UK air quality objective standards. A coupled climate-chemistry model is able to reproduce these temperature and ozone extremes. By combining model simulations of surface temperature and ozone with ozone-heat-mortality relationships derived from an epidemiological regression model, we estimate present-day and future health burdens across the UK. Future air quality legislation may need to consider the risk of increases in future heatwaves.

Interactive Ozone and Methane Chemistry in GISS-E2 Historical and Future Climate Simulations

NASA Technical Reports Server (NTRS)

Shindell, D. T.; Pechony, O.; Voulgarakis, A.; Faluvegi, G.; Nazarenko. L.; Lamarque, J.-F.; Bowman, K.; Milly, G.; Kovari, B.; Ruedy, R.;

Mortality tradeoff between air quality and skin cancer from changes in stratospheric ozone

NASA Astrophysics Data System (ADS)

Eastham, Sebastian D.; Keith, David W.; Barrett, Steven R. H.

2018-03-01

Skin cancer mortality resulting from stratospheric ozone depletion has been widely studied. Similarly, there is a deep body of literature on surface ozone and its health impacts, with modeling and observational studies demonstrating that surface ozone concentrations can be increased when stratospheric air mixes to the Earth’s surface. We offer the first quantitative estimate of the trade-off between these two effects, comparing surface air quality benefits and UV-related harms from stratospheric ozone depletion. Applying an idealized ozone loss term in the stratosphere of a chemistry-transport model for modern-day conditions, we find that each Dobson unit of stratospheric ozone depletion results in a net decrease in the global annual mortality rate of ~40 premature deaths per billion population (d/bn/DU). The impacts are spatially heterogeneous in sign and magnitude, composed of a reduction in premature mortality rate due to ozone exposure of ~80 d/bn/DU concentrated in Southeast Asia, and an increase in skin cancer mortality rate of ~40 d/bn/DU, mostly in Western Europe. This is the first study to quantify air quality benefits of stratospheric ozone depletion, and the first to find that marginal decreases in stratospheric ozone around modern-day values could result in a net reduction in global mortality due to competing health impact pathways. This result, which is subject to significant methodological uncertainty, highlights the need to understand the health and environmental trade-offs involved in policy decisions regarding anthropogenic influences on ozone chemistry over the 21st century.

A major event of Antarctic ozone hole influence in southern Brazil in October 2016: an analysis of tropospheric and stratospheric dynamics

NASA Astrophysics Data System (ADS)

Dornelles Bittencourt, Gabriela; Bresciani, Caroline; Kirsch Pinheiro, Damaris; Valentin Bageston, José; Schuch, Nelson Jorge; Bencherif, Hassan; Paes Leme, Neusa; Vaz Peres, Lucas

2018-03-01

The Antarctic ozone hole is a cyclical phenomenon that occurs during the austral spring where there is a large decrease in ozone content in the Antarctic region. Ozone-poor air mass can be released and leave through the Antarctic ozone hole, thus reaching midlatitude regions. This phenomenon is known as the secondary effect of the Antarctic ozone hole. The objective of this study is to show how tropospheric and stratospheric dynamics behaved during the occurrence of this event. The ozone-poor air mass began to operate in the region on 20 October 2016. A reduction of ozone content of approximately 23 % was observed in relation to the climatology average recorded between 1992 and 2016. The same air mass persisted over the region and a drop of 19.8 % ozone content was observed on 21 October. Evidence of the 2016 event occurred through daily mean measurements of the total ozone column made with a surface instrument (Brewer MkIII no. 167 Spectrophotometer) located at the Southern Space Observatory (29.42° S, 53.87° W) in São Martinho da Serra, Rio Grande do Sul. Tropospheric dynamic analysis showed a post-frontal high pressure system on 20 and 21 October 2016, with pressure levels at sea level and thickness between 1000 and 500 hPa. Horizontal wind cuts at 250 hPa and omega values at 500 hPa revealed the presence of subtropical jet streams. When these streams were allied with positive omega values at 500 hPa and a high pressure system in southern Brazil and Uruguay, the advance of the ozone-poor air mass that caused intense reductions in total ozone content could be explained.

Surface Ozone Variability and Trends over the South African Highveld from 1990 to 2007

NASA Technical Reports Server (NTRS)

Balashov, Nikolay V.; Thompson, Anne M.; Piketh, Stuart J.; Langerman, Kristy E.

2014-01-01

Surface ozone is a secondary air pollutant formed from reactions between nitrogen oxides (NOx = NO + NO2) and volatile organic compounds in the presence of sunlight. In this work we examine effects of the climate pattern known as the El Niño-Southern Oscillation (ENSO) and NOx variability on surface ozone from 1990 to 2007 over the South African Highveld, a heavily populated region in South Africa with numerous industrial facilities. Over summer and autumn (December-May) on the Highveld, El Niño, as signified by positive sea surface temperature (SST) anomalies over the central Pacific Ocean, is typically associated with drier and warmer than normal conditions favoring ozone formation. Conversely, La Niña, or negative SST anomalies over the central Pacific Ocean, is typically associated with cloudier and above normal rainfall conditions, hindering ozone production. We use a generalized regression model to identify any linear dependence that the Highveld ozone, measured at five air quality monitoring stations, may have on ENSO and NOx. Our results indicate that four out of the five stations exhibit a statistically significant sensitivity to ENSO at some point over the December-May period where El Niño amplifies ozone formation and La Niña reduces ozone formation. Three out of the five stations reveal statistically significant sensitivity to NOx variability, primarily in winter and spring. Accounting for ENSO and NOx effects throughout the study period of 18 years, two stations exhibit statistically significant negative ozone trends in spring, one station displays a statistically significant positive trend in August, and two stations show no statistically significant change in surface ozone.

Gridded global surface ozone metrics for atmospheric chemistry model evaluation

NASA Astrophysics Data System (ADS)

Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.

2016-02-01

The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent data set for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total data set of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regionally representative locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This data set is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily 8-hour average (MDA8), sum of means over 35 ppb (daily maximum 8-h; SOMO35), accumulated ozone exposure above a threshold of 40 ppbv (AOT40), and metrics related to air quality regulatory thresholds. Gridded data sets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi: 10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

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

NASA Astrophysics Data System (ADS)

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.

Stratosphere-to-Troposphere Transport Revealed by Ground-based Lidar and Ozonesonde at a Midlatitude Site

NASA Technical Reports Server (NTRS)

Kuang, Shi; Newchurch, M. J.; Burris, John; Wang, Lihua; Knupp, Kevin; Huang, Guanyu

2013-01-01

This paper presents ozone structures measured by a ground-based ozone lidar and ozonesonde at Huntsville, Alabama, on 27-29 April 2010 originating from a stratosphere-to-troposphere transport event associated with a cutoff cyclone and tropopause fold. In this case, the tropopause reached 6 km and the stratospheric intrusion resulted in a 2-km thick elevated ozone layer with values between 70 and 85 ppbv descending from the 306-K to 298-K isentropic surface at a rate of 5 km day1. The potential temperature was provided by a collocated microwave profiling radiometer. We examine the corresponding meteorological fields and potential vorticity (PV) structures derived from the analysis data from the North American Mesoscale model. The 2-PVU (PV unit) surface, defined as the dynamic tropopause, is able to capture the variations of the ozone tropopause estimated from the ozonesonde and lidar measurements. The estimated ozone/PV ratio, from the measured ozone and model derived PV, for the mixing layer between the troposphere and stratosphere is approximately 41 ppbv/PVU with an uncertainty of approximately 33%. Within two days, the estimated mass of ozone irreversibly transported from the stratospheric into the troposphere is between 0.07 Tg (0.9 10(exp33) molecules) and 0.11 Tg (1.3 10(exp33) molecules) with an estimated uncertainty of 59%. Tropospheric ozone exhibited enormous variability due to the complicated mixing processes. Low ozone and large variability were observed in the mid-troposphere after the stratospheric intrusion due to the westerly advection including the transition from a cyclonic system to an anticyclonic system. This study using high temporal and vertical-resolution measurements suggests that, in this case, stratospheric air quickly lost its stratospheric characteristics once it is irreversibly mixed down into the troposphere.

Lidar Measurements of Tropospheric Ozone in the Arctic

NASA Astrophysics Data System (ADS)

Seabrook, Jeffrey; Whiteway, James

2016-06-01

This paper reports on differential absorption lidar (DIAL) measurements of tropospheric ozone in the Canadian Arctic during springtime. Measurements at Eureka Weather Station revealed that mountains have a significant effect on the vertical structure of ozone above Ellesmere Island. Ozone depletion events were observed when air that had spent significant time near to the frozen surface of the Arctic Ocean reached Eureka. This air arrived at Eureka by flowing over the surrounding mountains. Surface level ozone depletions were not observed during periods when the flow of air from over the sea ice was blocked by mountains. In the case of blocking there was an enhancement in the amount of ozone near the surface as air from the mid troposphere descended in the lee of the mountains. Three case studies will be shown in the presentation, while one is described in this paper.

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

NASA Astrophysics Data System (ADS)

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.

Modeling of meteorology, tracer transport and chemistry for the Uintah Basin Winter Ozone Studies 2012 and 2013

NASA Astrophysics Data System (ADS)

Ahmadov, R.; McKeen, S. A.; Angevine, W. M.; Frost, G. J.; Roberts, J. M.; De Gouw, J. A.; Warneke, C.; Peischl, J.; Brown, S. S.; Edwards, P. M.; Wild, R. J.; Pichugina, Y. L.; Banta, R. M.; Brewer, A.; Senff, C. J.; Langford, A. O.; Petron, G.; Karion, A.; Sweeney, C.; Schnell, R. C.; Johnson, B.; Zamora, R. J.; Helmig, D.; Park, J.; Evans, J.; Stephens, C. R.; Olson, J. B.; Trainer, M.

2013-12-01

The Uintah Basin Winter Ozone Studies (UBWOS) field campaigns took place during winter of 2012 and 2013 in the Uintah Basin, Utah. The studies were aimed at characterizing meteorology, emissions of atmospheric constituents and air chemistry in a region abundant with oil and gas production, with associated emissions of various volatile organic compounds (VOCs) and NOx. High ozone pollution events were observed throughout the Uintah Basin during the winter of 2013, but not during the winter of 2012. A clear understanding of the processes leading to high ozone events is still lacking. We present here high spatiotemporal resolution simulations of meteorology, tracer transport and gas chemistry over the basin during January-February, 2012 and 2013 using the WRF/Chem regional photochemical model. Correctly characterizing the meteorology poses unique challenges due to complex terrain, cold-pool conditions, and shallow inversion layers observed during the winter of 2013. We discuss the approach taken to adequately simulate the meteorology over the basin and present evaluations of the modeled meteorology using surface, lidar and tethersonde measurements. Initial simulations use a passive tracer within the model as a surrogate for CH4 released from oil and gas wells. These tracer transport simulations show that concentrations of inert, emitted species near the surface in 2013 were 4-8 times higher than 2012 due to much shallower boundary layers and reduced winds in 2013. This is supported by in-situ measurements of CH4 made at the Horse Pool surface station during the field campaigns. Full photochemical simulations are forced by VOC and NOx emissions that are determined in a top-down approach, using observed emission ratios of VOC and NOx relative to CH4, along with available information of active wells, compressors, and processing plants. We focus on differences in meteorology, temperature, and radiation between the two winters in determining ozone concentrations in the basin. The model is then used diagnostically to assess first-order sensitivities of basin-wide ozone to NOx or VOC emissions, and how they depend on the environmental differences between the winters of 2012 and 2013.

Highlights from the 1998-2000 SHADOZ (Southern Hemisphere Additional Ozonesondes) Satellite Validation Project

NASA Technical Reports Server (NTRS)

Witte, J. C.; Thompson, A. M.; Fortuin, P.; Einsudi, Franco (Technical Monitor)

2001-01-01

There are three years of data (more than 1000 individual ozone profiles) available from a network of 10 southern hemisphere tropical and subtropical stations, designated the Southern Hemisphere ADditional OZonesondes (SHADOZ) project. Since late 1999, a tropical station in the northern hemisphere (Paramaribo, Surinam; lat/long) joined SHADOZ, providing coordinated weekly ozone and radiosonde data from the surface to approx. 7 hPa for satellite validation, process studies, and model evaluation. Profiles are also collected at: Ascension Island; Nairobi, Kenya; Irene, South Africa; R (union Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. The archive, station characteristics and photos are available at http://code9l6.gsfc.nasa.gov/Data_ services/shadoz>. SHADOZ ozone time-series and profiles in 1998-2000 display highly variable tropospheric ozone, a zonal wave-one pattern in total (and tropospheric) column ozone, and signatures of the Quasi-Biennial Oscillation (QBO) in stratospheric ozone. Total, stratospheric and tropospheric column ozone amounts peak between August and November and are lowest between March and May. Integrated total ozone column amounts from the sondes are lower than independent measurements from a ground-based network and from the TOMS (Total Ozone Mapping Spectrometer) satellite (version 7 data).

Ozone Climatology for Portsmouth, NH 1978-2002

NASA Astrophysics Data System (ADS)

Wake, C. P.; Miller, S. T.

2003-12-01

Hourly ozone mixing ratios have been monitored in Portsmouth, NH since 1978 for the typical "summer" ozone season (April to October) by the New Hampshire Department of Environmental Services. This 25 year record provides the basis to investigate seasonal variability in daily summertime ozone levels in Portsmouth NH and evaluate the relationship between ozone mixing ratios, temperature, precipitation, and the state of El Niño/Southern Oscillation. The overall goal of this research is to identify significant relationships between high ozone days and a suite of climate variables. The mean daily ozone mixing ratio in Portsmouth from 1977 through 2002 was 40 ppbv (sd 17 ppbv) with a mean of 6 days per summer when maxiumum 8 hour ozone levels exceed the 80 ppbv level. The highest ozone levels usually occur during June, July and August (with a peak in July), but high ozone days also occur May and September. April and October rarely experience high ozone. High ozone in coastal New Hampshire (and for most of New England) occurs predominantly on days when maximum temperatures are above 85 oF, although there are also may hot days when ozone levels do not reach elevated levels. Analysis of the relationship between number of days per year when 8 hour ozone is greater than 80 ppbv and maximum temperatures are greater than 85 oF indicates that there is a positive correlation (r = 0.60). Surprisingly, there is not a strong inverse relationship between ozone days and precipitation. For example, over the last 25 years, 1988 clearly stands out with 20 days with maximum 8 hour ozone above 80 ppbv. However, 1988 also experienced considerable precipitation in July and August (14.1 inches compared to the climatological mean of 6.7 inches) and relatively few days without precipitation (38 compared to the climatological mean of 44). There are differences in temperature, precipitation, and ozone levels in Portsmouth during years that are classified as El Ni¤o and neutral, compared to La Nina years. However, we have only experienced one strong La Nina year in the past 25 years, so the results must be viewed with caution. The La Nina year (1988) experience high ozone and more frequent hot days, as well as double the average precipitation. El Niño years experience slightly warmer, dryer and experience more frequent ozone days, although they are not significantly different from neutral years. Our results indicate that hot summers are indeed related to higher than average ozone levels, although there is considerable variability in this relationship. There does not appear to be a consistent ozone - precipitation relationship. Further work is needed to define these relationships for a larger number of stations throughout New England and also for comparison to broader synoptic to hemispheric circulation patterns and sea surface temperatures.

Polar boundary layer bromine explosion and ozone depletion events in the chemistry-climate model EMAC v2.52: implementation and evaluation of AirSnow algorithm

NASA Astrophysics Data System (ADS)

Falk, Stefanie; Sinnhuber, Björn-Martin

2018-03-01

Ozone depletion events (ODEs) in the polar boundary layer have been observed frequently during springtime. They are related to events of boundary layer enhancement of bromine. Consequently, increased amounts of boundary layer volume mixing ratio (VMR) and vertical column densities (VCDs) of BrO have been observed by in situ observation, ground-based as well as airborne remote sensing, and from satellites. These so-called bromine explosion (BE) events have been discussed serving as a source of tropospheric BrO at high latitudes, which has been underestimated in global models so far. We have implemented a treatment of bromine release and recycling on sea-ice- and snow-covered surfaces in the global chemistry-climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) based on the scheme of Toyota et al. (2011). In this scheme, dry deposition fluxes of HBr, HOBr, and BrNO3 over ice- and snow-covered surfaces are recycled into Br2 fluxes. In addition, dry deposition of O3, dependent on temperature and sunlight, triggers a Br2 release from surfaces associated with first-year sea ice. Many aspects of observed bromine enhancements and associated episodes of near-complete depletion of boundary layer ozone, both in the Arctic and in the Antarctic, are reproduced by this relatively simple approach. We present first results from our global model studies extending over a full annual cycle, including comparisons with Global Ozone Monitoring Experiment (GOME) satellite BrO VCDs and surface ozone observations.

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

PubMed

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.

Deposition velocities and impact of physical properties on ozone removal for building materials

NASA Astrophysics Data System (ADS)

Lin, Chi-Chi; Hsu, Shu-Chen

2015-01-01

This study aims to estimate the ozone deposition velocities of eight commonly used building materials (BMs) which include calcium silicate board (CSB), green calcium silicate board (GCSB), mineral fiber ceiling (MFC), green mineral fiber ceiling (GMFC), gypsum board (GB), green gypsum board (GGB), wooden flooring (WF) and green wooden flooring (GWF). In addition, the impact of physical properties (specific surface area and total pore volume of BM) on ozone removal ability was also explored and discussed. Studies were conducted in a small-scale environmental stainless steel chamber. CSB and GCSB showed the highest ozone deposition velocities, while WF and GWF showed the lowest ozone deposition velocities among test BMs materials. All reaction probabilities were estimated to fall within the order of magnitude of 10-6. Green BMs showed lower reaction probabilities with ozone comparing with non-green BMs except for GGB. Consistent with the trends for deposition velocity, fleecy and porous materials exhibit higher reaction probabilities than smooth, non-porous surfaces. Specific surface area of BM is more closely related to ozone removal than total pore volume of BM with R2 of 0.93 vs. R2 of 0.84. Discussion of Thiele modulus for all test BMs indicates surface reactions are occurring quickly relative to internal diffusion and ozone removal is internal diffusion-limited.

Evaluation of ozone hindcasts: optimal data sets to use, and results from simulations with the GMI model for 1990-2010.

NASA Astrophysics Data System (ADS)

Logan, J. A.; Megretskaia, I.; Liu, J.; Rodriguez, J. M.; Strahan, S. E.; Damon, M.; Steenrod, S. D.

2012-12-01

Simulations of atmospheric composition in the recent past (hindcasts) are a valuable tool for determining the causes of interannual variability (IAV) and trends in tropospheric ozone, including factors such as anthropogenic emissions, biomass burning, stratospheric input, and variability in meteorology. We will review the ozone data sets (balloon, satellite, and surface) that are the most reliable for evaluating hindcasts, and demonstrate their application with the GMI model. The GMI model is driven by the GEOS-5/MERRA reanalysis and includes both stratospheric and tropospheric chemistry. Preliminary analysis of a simulation for 1990-2010 using constant fossil fuel emissions is promising. The model reproduces the recent interannual variability (IAV) in ozone in the lowermost stratosphere seen in MLS and sonde data, as well as the IAV seen in sonde data in the lower stratosphere since 1995, and captures much of the IAV and short-term trends in surface ozone at remote sites, showing the influence of variability in dynamics. There was considerable IAV in ozone in the lowermost stratosphere in the Aura period, but almost none at European alpine sites in winter/spring, when ozone at 150 hPa has been shown to be correlated with that at 700 hPa in earlier years. The model matches the IAV in alpine ozone in Europe in July-September, including the high values in heat-waves, showing the role of variability in meteorology. A focus on IAV in each season is essential. The model matches IAV in MLS in the upper troposphere, TES tropical ozone, and the tropospheric ozone column (OMI/MLS) the best in tSropical regions controlled by ENSO related changes in dynamics. This study, combined with sensitivity simulations with changes to emissions, and simulations with passive tracers (see Abstract by Rodriguez et al. Session A76), lays the foundations for assessment of the mechanisms that have influenced tropospheric ozone in the past two decades.

Trends in Surface Level Ozone Observations from Human-health Relevant Metrics: Results from the Tropospheric Ozone Assessment Report (TOAR)

NASA Astrophysics Data System (ADS)

Fleming, Z. L.; von Schneidemesser, E.; Doherty, R. M.; Malley, C.; Cooper, O. R.; Pinto, J. P.; Colette, A.; Xu, X.; Simpson, D.; Schultz, M.; Hamad, S.; Moola, R.; Solberg, S.; Feng, Z.

2017-12-01

Ozone is an air pollutant formed in the atmosphere from precursor species (NOx, VOCs, CH4, CO) that is detrimental to human health and ecosystems. The global Tropospheric Ozone Assessment Report (TOAR) initiative has assembled a global database of surface ozone observations and generated ozone exposure metrics at thousands of measurement sites around the world. This talk will present results from the assessment focused on those indicators most relevant to human health. Specifically, the trends in ozone, comparing different time periods and patterns across regions and among metrics will be addressed. In addition, the fraction of population exposed to high ozone levels and how this has changed between 2000 and 2014 will also be discussed. The core time period analyzed for trends was 2000-2014, selected to include a greater number of sites in East Asia. Negative trends were most commonly observed at many US and some European sites, whereas many sites in East Asia showed positive trends, while sites in Japan showed more of a mix of positive and negative trends. More than half of the sites showed a common direction and significance in the trends for all five human-health relevant metrics. The peak ozone metrics indicate a reduction in exposure to peak levels of ozone related to photochemical episodes in Europe and the US. A considerable number of European countries and states within the US have shown a decrease in population-weighted ozone over time. The 2000-2014 results will be augmented and compared to the trend analysis for additional time periods that cover a greater number of years, but by necessity are based on fewer sites. Trends are found to be statistically significant at a larger fraction of sites with longer time series, compared to the shorter (2000-2014) time series.

Ozone, Tropospheric

NASA Technical Reports Server (NTRS)

Fishman, Jack

1995-01-01

In the early part of the 20th century, ground-based and balloon-borne measurements discovered that most of atmosphere's ozone is located in the stratosphere with highest concentrations located between 15 and 30 km (9,3 and 18.6 miles). For a long time, it was believed that tropospheric ozone originated from the stratosphere and that most of it was destroyed by contact with the earth's surface. Ozone, O3, was known to be produced by the photo-dissociation of molecular oxygen, O2, a process that can only occur at wavelengths shorter than 242 nm. Because such short-wave-length radiation is present only in the stratosphere, no tropospheric ozone production is possible by this mechanism. In the 1940s, however, it became obvious that production of ozone was also taking place in the troposphere. The overall reaction mechanism was eventually identified by Arie Haagen-Smit of the California Institute of Technology, in highly polluted southern California. The copious emissions from the numerous cars driven there as a result of the mass migration to Los Angeles after World War 2 created the new unpleasant phenomenon of photochemical smog, the primary component of which is ozone. These high levels of ozone were injuring vegetable crops, causing women's nylons to run, and generating increasing respiratory and eye-irritation problems for the populace. Our knowledge of tropospheric ozone increased dramatically in the early 1950s as monitoring stations and search centers were established throughout southern California to see what could be done to combat this threat to human health and the environment.

GOME-2 Tropospheric Ozone Profile Retrievals from Joint UV/Visible Measurement

NASA Astrophysics Data System (ADS)

Liu, X.; Zoogman, P.; Chance, K.; Cai, Z.; Nowlan, C. R.; Huang, G.; Gonzalez Abad, G.

2016-12-01

It has been shown from sensitivity studies that adding visible measurements in the Chappuis ozone band to UV measurements in the Hartley/Huggins ozone bands can significantly enhance retrieval sensitivity to lower tropospheric ozone from backscattered solar radiances due to deeper photon penetration in the visible to the surface than in the ultraviolet. The first NASA EVI (Earth Venture Instrument) TEMPO (Tropospheric Emissions: Monitoring of Pollution) instrument is being developed to measure backscattered solar radiation in two channels ( 290-490 and 540-740 nm) and make atmospheric pollution measurements over North America from the Geostationary orbit. However, this retrieval enhancement has yet to be demonstrated from existing measurements due to the weak ozone absorption in the visible and strong interferences from surface reflectance and aerosols and the requirement of accurate radiometric calibration across different spectral channels. We present GOME-2 retrievals from joint UV/visible measurements using the SAO ozone profile retrieval algorithm, to directly explore the retrieval improvement in lower tropospheric ozone from additional visible measurements. To reduce the retrieval interference from surface reflectance, we add characterization of surface spectral reflectance in the visible based on combining EOFs (Empirical Orthogonal Functions) derived from ASTER and other surface reflectance spectra with MODIS BRDF climatology into the ozone profile algorithm. The impacts of various types of aerosols and surface BRDF on the retrievals will be investigated. In addition, we will also perform empirical radiometric calibration of the GOME-2 data based on radiative transfer simulations. We will evaluate the retrieval improvement of joint UV/visible retrieval over the UV retrieval based on fitting quality and validation against ozonesonde observations.

Analysis of Strong Wintertime Ozone Events in an Area of Extensive Oil and Gas Extraction

NASA Astrophysics Data System (ADS)

Rappenglück, Bernhard; Ackermann, Luis; Alvarez, Sergio; Golovko, Julia; Buhr, Martin; Field, Robert; Soltis, Jeff; Montague, Derek C.; Hauze, Bill; Scott, Adamson; Risch, Dan; Wilkerson, George; Bush, David; Stoeckenius, Till; Keslar, Cara

2015-04-01

During recent years, elevated ozone (O3) values have been observed repeatedly in the Upper Green River Basin (UGRB), Wyoming during wintertime. This paper presents an analysis of high ozone days in late winter 2011 (1-hour average up to 166 ppbv). Intensive Observational Periods (IOPs) were performed which included comprehensive surface and boundary layer measurements. Low windspeeds in combination with low mixing layer heights (~50 m agl) are essential for accumulation of pollutants. Air masses contain substantial amounts of reactive nitrogen (NOx) and non-methane hydrocarbons (NMHC) emitted from fossil fuel exploration activities in the Pinedale Anticline. On IOP days in the morning hours reactive nitrogen (up to 69%), then aromatics and alkanes (each ~10-15%; mostly ethane and propane) are major contributors to the hydroxyl (OH) reactivity. This time frame largely coincides with lowest NMHC/NOx ratios (~50), reflecting a relatively low NMHC mixture, and a change from a NOx-limited regime towards a NMHC limited regime. OH production on IOP days is mainly due to nitrous acid (HONO). On a 24-hr basis and as determined for a measurement height of 1.80 m above the surface HONO photolysis on IOP days can contribute ~83% to OH production on average, followed by alkene ozonolysis (~9%). Photolysis by ozone and HCHO photolysis contributes about 4% each to hydroxyl formation. High HONO levels (maximum hourly median on IOP days: 1,096 pptv) are favored by a combination of shallow boundary layer conditions and enhanced photolysis rates due to the high albedo of the snow surface. HONO is most likely formed through (i) abundant nitric acid (HNO3) produced in atmospheric oxidation of NOx, deposited onto the snow surface and undergoing photo-enhanced heterogeneous conversion to HONO and (ii) combustion related emission of HONO. HONO production is confined to the lowermost 10 m of the boundary layer. HONO, serves as the most important precursor for OH, strongly enhanced due to the high albedo of the snow cover.

Ozone response to enhanced heterogeneous processing after the eruption of Mt. Pinatubo

NASA Technical Reports Server (NTRS)

Rodriguez, Jose M.; Ko, M. K. W.; Sze, N. D.; Heisey, C. W.; Yue, G. K.; Mccormick, M. P.

1994-01-01

Increases in aerosol loading after the Pinatubo eruption are expected to cause additional ozone depletion. Even though aerosol loadings were highest in the winter of 1991-1992, recent analyses of satellite and ground-based ozone measurements indicate that ozone levels in the winter of 1992-1993 are the lowest recorded in recent years, raising the question of the mechanisms responsible for such behavior. We have incorporated aerosol surface areas derived from the Stratospheric Aerosol and Gas Experiment II (SAGE-II) measurements into our two-dimensional model. Inclusion of heterogeneous chemsitry on these enhanced aerosol surfaces yields maximum ozone reductions during the winter of 1992-1993 in the Northern Hemisphere, consistent with those derived from observations. This delayed behavior is due to the combination of the non-linear nature of the impact of heterogeneous reactions as a function of aerosol surface area, and the long time constants for ozone in the lower stratosphere. If heterogeneous mechanisms are primarily responsible for the low 1992-1993 ozone levels, we expect ozone concentrations to start recovering in 1994.

Air Quality Impacts of Oil and Gas Operations in the Northern Colorado Front Range

NASA Astrophysics Data System (ADS)

Helmig, D.; Thompson, C. R.; Jacques, H.; Smith, K. R.; Terrell, R. M.

2014-12-01

Exceedences of the US EPA National Ambient Air Quality Standard (NAAQS) for surface ozone have been reported from monitoring sites in the Northern Colorado Front Range (NCFR) for more than fifteen years during summer. Comparison of ozone records from the NCFR clearly show that ozone primarily results from regional photochemical daytime production. Recent trend analyses do not show an improvement of surface ozone despite efforts by the State of Colorado to curb ozone precursor emissions. Our review of atmospheric volatile organic compound (VOC) measurements from historic and recent monitoring shows significant spatial increases of atmospheric VOC towards the oil and gas development area in Weld County, NW of the Denver-Boulder metropolitan region. Secondly, analyses of VOC trends and VOC signatures show an overall increase of oil and gas associated VOC relative to other VOC sources. These analyses suggest that oil and gas emissions are playing and increasing role in ozone production in the NCFR and that reductions of oil and gas emissions would be beneficial for lowering surface ozone and attainment of the ozone NAAQS.

A Comparison of Statistical Techniques for Combining Modeled and Observed Concentrations to Create High-Resolution Ozone Air Quality Surfaces

EPA Science Inventory

Air quality surfaces representing pollutant concentrations across space and time are needed for many applications, including tracking trends and relating air quality to human and ecosystem health. The spatial and temporal characteristics of these surfaces may reveal new informat...

Effects of future land use and ecosystem changes on boundary-layer meteorology and air quality

NASA Astrophysics Data System (ADS)

Tai, A. P. K.; Wang, L.; Sadeke, M.

2017-12-01

Land vegetation plays key roles shaping boundary-layer meteorology and air quality via various pathways. Vegetation can directly affect surface ozone via dry deposition and biogenic emissions of volatile organic compounds (VOCs). Transpiration from land plants can also influence surface temperature, soil moisture and boundary-layer mixing depth, thereby indirectly affecting surface ozone. Future changes in the distribution, density and physiology of vegetation are therefore expected to have major ramifications for surface ozone air quality. In our study, we examine two aspects of potential vegetation changes using the Community Earth System Model (CESM) in the fully coupled land-atmosphere configuration, and evaluate their implications on meteorology and air quality: 1) land use change, which alters the distribution of plant functional types and total leaf density; and 2) ozone damage on vegetation, which alters leaf density and physiology (e.g., stomatal resistance). We find that, following the RCP8.5 scenario for 2050, global cropland expansion induces only minor changes in surface ozone in tropical and subtropical regions, but statistically significant changes by up to +4 ppbv in midlatitude North America and East Asia, mostly due to higher surface temperature that enhances biogenic VOC emissions, and reduced dry deposition to a lesser degree. These changes are in turn to driven mostly by meteorological changes that include a shift from latent to sensible heat in the surface energy balance and reduced soil moisture, reflecting not only local responses but also a northward expansion of the Hadley Cell. On the other hand, ozone damage on vegetation driven by rising anthropogenic emissions is shown to induce a further enhancement of ozone by up to +6 ppbv in midlatitude regions by 2050. This reflects a strong localized positive feedback, with severe ozone damage in polluted regions generally inducing stomatal closure, which in turn reduces transpiration, increases surface temperature, and thus enhances biogenic VOC emissions and surface ozone. Our findings demonstrate the importance of considering meteorological responses to vegetation changes in future air quality assessment, and call for greater coordination among land use, ecosystem and air quality management efforts.

Comparison of pharmaceutical abatement in various water matrices by conventional ozonation, peroxone (O3/H2O2), and an electro-peroxone process.

PubMed

Wang, Huijiao; Zhan, Juhong; Yao, Weikun; Wang, Bin; Deng, Shubo; Huang, Jun; Yu, Gang; Wang, Yujue

2018-03-01

Pharmaceutical abatement in a groundwater (GW), surface water (SW), and secondary effluent (SE) by conventional ozonation, the conventional peroxone (O 3 /H 2 O 2 ), and the electro-peroxone (E-peroxone) processes was compared in batch tests. SE had significantly more fast-reacting dissolved organic matter (DOM) moieties than GW and SW. Therefore, O 3 decomposed much faster in SE than in GW and SW. At specific ozone doses of 0.5-1.5 mg O 3 /mg dissolved organic carbon (DOC), the application of O 3 /H 2 O 2 and E-peroxone process (by adding external H 2 O 2 stocks or in-situ generating H 2 O 2 from cathodic O 2 reduction during ozonation) similarly enhanced the OH yield from O 3 decomposition by ∼5-12% and 5-7% in GW and SW, respectively, compared to conventional ozonation. In contrast, due to the slower reaction kinetics of O 3 with H 2 O 2 than O 3 with fast-reacting DOM moieties, the addition or electro-generation of H 2 O 2 hardly increased the OH yield (<4% increases) in SE. Corresponding to the changes in the OH yields, the abatement efficiencies of ozone-resistant pharmaceuticals (ibuprofen and clofibric acid) increased evidently in GW (up to ∼14-18% at a specific ozone dose of 1.5 mg O 3 /mg DOC), moderately in SW (up to 6-10% at 0.5 mg O 3 /mg DOC), and negligibly in SE during the O 3 /H 2 O 2 and E-peroxone treatment compared to conventional ozonation. These results indicate that similar to the conventional O 3 /H 2 O 2 process, the E-peroxone process can more pronouncedly enhance O 3 transformation to OH, and thus increase the abatement efficiency of ozone-resistant pharmaceuticals in water matrices exerting relatively high ozone stability (e.g., groundwater and surface water with low DOM contents). Therefore, by installing electrodes in existing ozone reactors, the E-peroxone process may provide a convenient way to enhance pharmaceutical abatement in drinking water applications, where groundwater and surface water with low DOM contents are used as the source waters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sorption, desorption, and surface oxidative fate of nicotine.

PubMed

Petrick, Lauren; Destaillats, Hugo; Zouev, Irena; Sabach, Sara; Dubowski, Yael

2010-09-21

Nicotine dynamics in an indoor environment can be greatly affected by building parameters (e.g. relative humidity (RH), air exchange rate (AER), and presence of ozone), as well as surface parameters (e.g. surface area (SA) and polarity). To better understand the indoor fate of nicotine, these parameter effects on its sorption, desorption, and oxidation rates were investigated on model indoor surfaces that included fabrics, wallboard paper, and wood materials. Nicotine sorption under dry conditions was enhanced by higher SA and higher polarity of the substrate. Interestingly, nicotine sorption to cotton and nylon was facilitated by increased RH, while sorption to polyester was hindered by it. Desorption was affected by RH, AER, and surface type. Heterogeneous nicotine-ozone reaction was investigated by Fourier transform infrared spectrometry with attenuated total reflection (FTIR-ATR), and revealed a pseudo first-order surface reaction rate of 0.035 +/- 0.015 min(-1) (at [O(3)] = 6 +/- 0.3 x 10(15) molecules cm(-3)) that was partially inhibited at high RH. Extrapolation to a lower ozone level ([O(3)] = 42 ppb) showed oxidation on the order of 10(-5) min(-1) corresponding to a half-life of 1 week. In addition, similar surface products were identified in dry and high RH using gas chromatography-mass spectrometry (GC-MS). However, FTIR analysis revealed different product spectra for these conditions, suggesting additional unidentified products and association with surface water. Knowing the indoor fate of condensed and gas phase nicotine and its oxidation products will provide a better understanding of nicotine's impact on personal exposures as well as overall indoor air quality.

A network of autonomous surface ozone monitors in Antarctica: technical description and first results

NASA Astrophysics Data System (ADS)

Bauguitte, S. J.; Brough, N.; Frey, M. M.; Jones, A. E.; Roscoe, H. K.; Wolff, E. W.

2009-12-01

Concentrations of surface ozone over polar regions cannot be derived from satellite data so can only be studied from ground-based platforms. To understand the regional picture a carefully-designed network of ground-based monitors is required. Here we report on a network of 10 autonomous ozone monitors that was established around the Weddell Sea sector of coastal Antarctica with a transect up onto the Antarctic Plateau during the International Polar Year. The aim was to measure for a full year, thus gaining a much-improved broader view of boundary layer ozone seasonality at different locations as well as on factors affecting the budget of surface ozone in Antarctica. Of specific interest were the balance between halogen-driven destruction and photochemical production from snow-emitted precursors, as well as the spatial extent of ozone depletion events. Each ozone monitor measured successfully within its predefined duty cycle throughout the year, with some differences in performance dependent on power availability. Here we present technical information and first results from the network.

Characterizing the seasonal cycle and vertical structure of ozone in Paris, France using four years of ground based LIDAR measurements in the lowermost troposphere

NASA Astrophysics Data System (ADS)

Klein, Amélie; Ancellet, Gérard; Ravetta, François; Thomas, Jennie L.; Pazmino, Andrea

2017-10-01

Systematic ozone LIDAR measurements were completed during a 4 year period (2011-2014) in Paris, France to study the seasonal variability of the vertical structure of ozone in the urban boundary layer. In addition, we use in-situ measurements from the surface air quality network that is located in Paris (AIRPARIF). Specifically, we use ozone and NO2 measurements made at two urban stations: Paris13 (60 m ASL) and the Eiffel Tower (310 m ASL) to validate and interpret the LIDAR profiles. Remote sensed tropospheric NO2 integrated columns from the SAOZ instrument located in Paris are also used to interpret ozone measurements. Comparison between ozone LIDAR measurements averaged from 250 m to 500 m and the Eiffel Tower in-situ measurements shows that the accuracy of the LIDAR (originally ±14 μg·m-3) is significantly improved (±7 μg·m-3) when a small telescope with a wide angular aperture is used. Results for the seasonal cycle of the ozone vertical gradient are found to be similar using two methods: (1) measured differences between AIRPARIF stations with measurements at 60 m ASL and 310 m ASL and (2) using LIDAR profiles from 300 m to the top of the Planetary Boundary Layer (PBL). Ozone concentrations measured by the LIDAR increase with altitude within the PBL, with a steeper gradient in winter (60 μg·m-3·km-1) and a less strong gradient in summer (20 μg·m-3·km-1). Results show that in winter, there is a sharp positive gradient of ozone at the surface, which is explained by ozone titration by NO combined with increased atmospheric stability in winter. In the afternoon during summer, photochemistry and vertical mixing are large enough to compensate for ozone titration near the surface, where NOx is emitted, and there is no gradient in ozone observed. In contrast, in the summer during the morning, ozone has a sharper positive vertical gradient similar to the winter values. Comparison of the vertically averaged ozone concentrations up to (0-3 km) and urban layer (0-310 m) ozone concentrations shows that the ratio between these two quantities is the largest in summer (86%) and the lowest in winter (49%). We conclude that satellite measurements that represent the 0-3 km integrated ozone column are not necessarily a good proxy for surface ozone and may lead to incorrect conclusions about the surface ozone seasonal variability. The ratio between the urban layer NO2 average concentration and the boundary layer NO2 average concentration obtained from SAOZ NO2 tropospheric columns is always less than 50%, meaning NO2 does not decrease linearly in the PBL, but with a sharper decrease close to the surface.

Source attribution of interannual variability of tropospheric ozone over the southern hemisphere

NASA Astrophysics Data System (ADS)

Liu, J.; Rodriguez, J. M.; Logan, J. A.; Steenrod, S. D.; Douglass, A. R.; Olsen, M. A.; Wargan, K.; Ziemke, J. R.

2015-12-01

Both model simulations and GMAO assimilated ozone product derived from OMI/MLS show a high tropospheric ozone column centered over the south Atlantic from the equator to 30S. This ozone maximum extends eastward to South America and the southeast Pacific; it extends southwestward to southern Africa, south Indian Ocean. In this study, we use hindcast simulations from the GMI model of tropospheric and stratospheric chemistry, driven by assimilated MERRA meteorological fields, to investigate the factors controlling the interannual variations (IAV) of this ozone maximum during the last two decades. We also use various GMI tracer diagnostics, including a stratospheric ozone tracer to tag the impact of stratospheric ozone, and a tagged CO tracer to track the emission sources, to ascertain the contribution of difference processes to IAV in ozone at different altitudes, as well as partial columns above different pressure level. Our initial model analysis suggests that the IAV of the stratospheric contribution plays a major role on in the IAV of the upper tropospheric ozone and explains a large portion of variance during its winter season. Over the south Atlantic region, the IAV of surface emissions from both South America and southern Africa also contribute significantly to the IAV of ozone, especially in the middle and lower troposphere

The effect of surface anisotropy on the accuracy of total ozone estimates from satellite observations

NASA Technical Reports Server (NTRS)

Fraser, R. S.; Ahmad, Z.

1978-01-01

The total amount of ozone in a vertical column of the earth's atmosphere is being derived from satellite measurements of the intensity of ultraviolet sunlight scattered by the earth-atmosphere system. The algorithm for deriving the ozone amount utilizes the assumption that the earth's surface reflects the incident light isotropically according to Lambert's law. Natural surface reflection deviates more or less from this law. Two extreme examples of anisotropic reflection from dark ocean and from bright snow are analyzed by means of models for their effects on the derived values of ozone.

Transport and deposition of nitrogen oxides and ozone in the atmospheric surface layer

NASA Astrophysics Data System (ADS)

Li, Yongxian

Tropospheric ozone is an important photochemical air pollutant, which increases respiratory-related diseases, decreases crop yields, and causes other environmental problems. This research has focused on the measurement of soil biogenic emissions of nitric oxide (NO), one of the precursors for ozone formation, from intensively managed soils in the Southeast US, and examined the transport and deposition of NOx (NO + NO2) and ozone in the atmospheric surface layer, and the effects of NO emissions and its chemical reactions on ozone flux and deposition to the earth's surface. Emissions of nitric oxide were measured from an intensively managed agricultural soil, in the lower coastal plain of North Carolina (near Plymouth, NC), using a dynamic chamber technique. Measurements of soil NO emissions in several crop canopies were conducted at four different sites in North Carolina during late spring and summer of 1994-1996. The turbulent fluxes of NO2 and O3 at 5 m and 10 m above the ground were measured using the eddy-correlation technique near Plymouth, NC during late spring of 1995 and summer of 1996, concurrent with measurements of soil NO emissions using the dynamic chamber system. Soil NO emission from within the corn field was high averaging approximately 35 ng N/m2/s during the measurement period of 1995. In another study, vertical measurements of ozone were made on a 610 m tall tower located 15 km Southeast of Raleigh, NC during the summers of 1993-1997, as part of an effort by the State of North Carolina to develop a State Implementation Plan (SIP) for ozone control in the Raleigh Metropolitan Statistical Area. A strong correlation was observed between the nighttime and early morning ozone concentrations in the residual layer (CR) above the NBL and the maximum ground level concentration (C o max) the following afternoon. Based on this correlation, an empirical regression equation (Co max = 27.67*exp(0.016 CR)) was developed for predicting maximum ground level ozone concentrations during the summer months. (Abstract shortened by UMI.)

Assimilation of IASI partial tropospheric columns with an Ensemble Kalman Filter over Europe

NASA Astrophysics Data System (ADS)

Coman, A.; Foret, G.; Beekmann, M.; Eremenko, M.; Dufour, G.; Gaubert, B.; Ung, A.; Schmechtig, C.; Flaud, J.-M.; Bergametti, G.

2011-09-01

Partial lower tropospheric ozone columns provided by the IASI (Infrared Atmospheric Sounding Interferometer) instrument have been assimilated into a chemistry-transport model at continental scale (CHIMERE) using an Ensemble Kalman Filter (EnKF). Analyses are made for the month of July 2007 over the European domain. Launched in 2006, aboard the MetOp-A satellite, IASI shows high sensitivity for ozone in the free troposphere and low sensitivity at the ground; therefore it is important to evaluate if assimilation of these observations can improve free tropospheric ozone, and possibly surface ozone. The analyses are validated against independent ozone observations from sondes, MOZAIC1 aircraft and ground based stations (AIRBASE - the European Air quality dataBase) and compared with respect to the free run of CHIMERE. These comparisons show a decrease in error of 6 parts-per-billion (ppb) in the free troposphere over the Frankfurt area, and also a reduction of the root mean square error (respectively bias) at the surface of 19% (33%) for more than 90% of existing ground stations. This provides evidence of the potential of data assimilation of tropospheric IASI columns to better describe the tropospheric ozone distribution, including surface ozone, despite the lower sensitivity. The changes in concentration resulting from the observational constraints were quantified and several geophysical explanations for the findings of this study were drawn. The corrections were most pronounced over Italy and the Mediterranean region, on the average we noted an average reduction of 8-9 ppb in the free troposphere with respect to the free run, and still a reduction of 5.5 ppb at ground, likely due to a longer residence time of air masses in this part associated to the general circulation pattern (i.e. dominant western circulation) and to persistent anticyclonic conditions over the Mediterranean basin. This is an important geophysical result, since the ozone burden is large over this area, with impact on the radiative balance and air quality. 1 Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft ( http://mozaic.aero.obs-mip.fr/web/)

Assimilation of IASI partial tropospheric columns with an Ensemble Kalman Filter over Europe

NASA Astrophysics Data System (ADS)

Coman, A.; Foret, G.; Beekmann, M.; Eremenko, M.; Dufour, G.; Gaubert, B.; Ung, A.; Schmechtig, C.; Flaud, J.-M.; Bergametti, G.

2012-03-01

Partial lower tropospheric ozone columns provided by the IASI (Infrared Atmospheric Sounding Interferometer) instrument have been assimilated into a chemistry-transport model at continental scale (CHIMERE) using an Ensemble Square Root Kalman Filter (EnSRF). Analyses are made for the month of July 2007 over the European domain. Launched in 2006, aboard the MetOp-A satellite, IASI shows high sensitivity for ozone in the free troposphere and low sensitivity at the ground; therefore it is important to evaluate if assimilation of these observations can improve free tropospheric ozone, and possibly surface ozone. The analyses are validated against independent ozone observations from sondes, MOZAIC1 aircraft and ground based stations (AIRBASE - the European Air quality dataBase) and compared with respect to the free run of CHIMERE. These comparisons show a decrease in error of 6 parts-per-billion (ppb) in the free troposphere over the Frankfurt area, and also a reduction of the root mean square error (respectively bias) at the surface of 19% (33%) for more than 90% of existing ground stations. This provides evidence of the potential of data assimilation of tropospheric IASI columns to better describe the tropospheric ozone distribution, including surface ozone, despite the lower sensitivity. The changes in concentration resulting from the observational constraints were quantified and several geophysical explanations for the findings of this study were drawn. The corrections were most pronounced over Italy and the Mediterranean region, we noted an average reduction of 8-9 ppb in the free troposphere with respect to the free run, and still a reduction of 5.5 ppb at ground, likely due to a longer residence time of air masses in this part associated to the general circulation pattern (i.e. dominant western circulation) and to persistent anticyclonic conditions over the Mediterranean basin. This is an important geophysical result, since the ozone burden is large over this area, with impact on the radiative balance and air quality. 1 Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft (http://mozaic.aero.obs-mip.fr/web/).

Influence of mountains on Arctic tropospheric ozone

NASA Astrophysics Data System (ADS)

Seabrook, Jeffrey; Whiteway, James

2016-02-01

Tropospheric ozone was measured above Ellesmere Island in the Canadian Arctic during spring of 2008 using a differential absorption lidar. The observations were carried out at Eureka Weather Station, which is located between various mountain ranges. Analysis of the observations revealed that mountains had a significant effect on the vertical distribution of ozone. Ozone depletion events were observed when air that had spent significant time near to the frozen surface of the Arctic Ocean reached Eureka. This air arrived at Eureka by flowing over the surrounding mountains. Surface level ozone depletions were not observed during periods when mountains blocked the flow of air from over the sea ice. In the case of blocking there was an enhancement in the amount of ozone near the surface as air from the midtroposphere descended in the lee of the mountains. Three case studies from spring of 2008 are described.

Stratospheric solar geoengineering without ozone loss.

PubMed

Keith, David W; Weisenstein, Debra K; Dykema, John A; Keutsch, Frank N

2016-12-27

Injecting sulfate aerosol into the stratosphere, the most frequently analyzed proposal for solar geoengineering, may reduce some climate risks, but it would also entail new risks, including ozone loss and heating of the lower tropical stratosphere, which, in turn, would increase water vapor concentration causing additional ozone loss and surface warming. We propose a method for stratospheric aerosol climate modification that uses a solid aerosol composed of alkaline metal salts that will convert hydrogen halides and nitric and sulfuric acids into stable salts to enable stratospheric geoengineering while reducing or reversing ozone depletion. Rather than minimizing reactive effects by reducing surface area using high refractive index materials, this method tailors the chemical reactivity. Specifically, we calculate that injection of calcite (CaCO 3 ) aerosol particles might reduce net radiative forcing while simultaneously increasing column ozone toward its preanthropogenic baseline. A radiative forcing of -1 W⋅m -2 , for example, might be achieved with a simultaneous 3.8% increase in column ozone using 2.1 Tg⋅y -1 of 275-nm radius calcite aerosol. Moreover, the radiative heating of the lower stratosphere would be roughly 10-fold less than if that same radiative forcing had been produced using sulfate aerosol. Although solar geoengineering cannot substitute for emissions cuts, it may supplement them by reducing some of the risks of climate change. Further research on this and similar methods could lead to reductions in risks and improved efficacy of solar geoengineering methods.

Identifying and forecasting deep stratospheric ozone intrusions over the western United States from space

NASA Astrophysics Data System (ADS)

Lin, M.; Fiore, A. M.; Horowitz, L. W.; Cooper, O. R.; Langford, A. O.; Pan, L.; Liu, X.; Reddy, P. J.

2012-12-01

Recent studies have shown that deep stratospheric ozone intrusions can episodically enhance ground-level ozone above the health-based standard over the western U.S. in spring. Advanced warning of incoming intrusions could be used by state agencies to inform the public about poor air quality days. Here we explore the potential for using total ozone retrievals (version 5.2, level 3) at twice daily near global coverage from the AIRS instrument aboard the NASA Aqua satellite to identify stratospheric intrusions and forecast the eventual surface destination of transported stratospheric ozone. The method involves the correlation of AIRS daily total ozone columns at each 1ox1o grid box ~1-3 days prior to stratospheric enhancements to daily maximum 8-hour average ozone at a selected surface site using datasets from April to June in 2003-2011. The surface stratospheric enhancements are estimated by the GFDL AM3 chemistry-climate model which includes full stratospheric and tropospheric chemistry and is nudged to reanalysis winds. Our earlier work shows that the model presents deep stratospheric intrusions over the Western U.S. consistently with observations from AIRS, surface networks, daily ozone sondes, and aircraft lidar available in spring of 2010 during the NOAA CalNex field campaign. For the 15 surface sites in the U.S. Mountain West considered, a correlation coefficient of 0.4-0.7 emerges with AIRS ozone columns over 30o-50oN latitudes and 125o-105oW longitudes - variability in the AIRS column within this spatial domain indicates incoming intrusions. For each "surface receptor site", the spatial domain can narrow to an area ~5ox5o northwest of the individual site, with the strong correlation (0.5-0.7) occurring when the AIRS data is lagged by 1 day from the AM3 stratospheric enhancements in surface air. The spatial pattern of correlations is consistent with our process-oriented understanding developed from case studies of extreme intrusions. Surface observations during these events show that the sites experiencing elevated ozone levels are typically located over the southeastern side of the enhanced ozone columns captured by AIRS ~12 hours to 1 day prior. This first scoping study suggests there is potential to use near-daily global coverage of ozone in total column or in UT/LS levels from the space-based instruments (e.g. AIRS, OMI, MLS) to serve as a qualitative early-warning indicator of incoming stratospheric intrusions with a lead time of ~1-3 days. There is more skill in ~12 hours to 1 day as to where the intrusion will reach the surface, particularly during the ENSO years (i.e. 2003, 2008, 2010, 2011) when deep intrusions are more likely to occur as compared to other years. These space-based ozone products can also provide some indication of whether a historic exceedance was caused by an intrusion.

Ozone injury on Bel W-3 tobacco controlled by at least two genes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, G.S.

1968-08-01

Tobacco varieties differ widely in susceptibility to injury by ozone in polluted air. Ordinarily, this injury appears as small flecks on the upper surface of the leaf. The highly susceptible variety Bel W-3, commonly used as an indicator plant for ozone, develops both the flecking plus larger brown or white spots which interfere with the assessment of injury. The highly resistant breeding line 6524 develops no spots but only a few flecks under like conditions. The F/sub 1/ of Bel W-3 x 6524 is intermediate, showing flecks but fewer spots than Bel W-3. The F/sub 2/, however, segregated into 40%more » highly resistant, 10% highly susceptible, and 50% intermediate individuals. When exposed to ozone, resistant plants developed only a few small flecks, and susceptible plants responded as does Bel W-3. Among the plants in the intermediate group were individuals that formed only larger brown or white spots without fleck. Plants with the severe spot reaction showed injury on the calyx remnant surrounding the seed pod. Microbial infection was not involved. This is the first evidence that the severe symptoms of ozone injury on Bel W-3 are a combination of reactions controlled by at least two separate genes.« less

Improved selectivity towards NO₂ of phthalocyanine-based chemosensors by means of original indigo/nanocarbons hybrid material.

PubMed

Brunet, J; Pauly, A; Dubois, M; Rodriguez-Mendez, M L; Ndiaye, A L; Varenne, C; Guérin, K

2014-09-01

A new and original gas sensor-system dedicated to the selective monitoring of nitrogen dioxide in air and in the presence of ozone, has been successfully achieved. Because of its high sensitivity and its partial selectivity towards oxidizing pollutants (nitrogen dioxide and ozone), copper phthalocyanine-based chemoresistors are relevant. The selectivity towards nitrogen dioxide results from the implementation of a high efficient and selective ozone filter upstream the sensing device. Thus, a powdered indigo/nanocarbons hybrid material has been developed and investigated for such an application. If nanocarbonaceous material acts as a highly permeable matrix with a high specific surface area, immobilized indigo nanoparticles are involved into an ozonolysis reaction with ozone leading to the selective removal of this analytes from air sample. The filtering yields towards each gas have been experimentally quantified and establish the complete removal of ozone while having the concentration of nitrogen dioxide unchanged. Long-term gas exposures reveal the higher durability of hybrid material as compared to nanocarbons and indigo separately. Synthesis, characterizations by many complementary techniques and tests of hybrid filters are detailed. Results on sensor-system including CuPc-based chemoresistors and indigo/carbon nanotubes hybrid material as in-line filter are illustrated. Sensing performances will be especially discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Feasibility Study For A Spaceborne Ozone/Aerosol Lidar System

NASA Technical Reports Server (NTRS)

Campbell, Richard E.; Browell, Edward V.; Ismail, Syed; Dudelzak, Alexander E.; Carswell, Allan I.; Ulitsky, Arkady

1997-01-01

Because ozone provides a shield against harmful ultraviolet radiation, determines the temperature profile in the stratosphere, plays important roles in tropospheric chemistry and climate, and is a health risk near the surface, changes in natural ozone layers at different altitudes and their global impact are being intensively researched. Global ozone coverage is currently provided by passive optical and microwave satellite sensors that cannot deliver high spatial resolution measurements and have particular limitations in the troposphere. Vertical profiling DIfferential Absorption Lidars (DIAL) have shown excellent range-resolved capabilities, but these systems have been large, inefficient, and have required continuous technical attention for long term operations. Recently, successful, autonomous DIAL measurements have been performed from a high-altitude aircraft (LASE - Lidar Atmospheric Sensing Experiment), and a space-qualified aerosol lidar system (LITE - Laser In-space Technology Experiment) has performed well on Shuttle. Based on the above successes, NASA and the Canadian Space Agency are jointly studying the feasibility of developing ORACLE (Ozone Research with Advanced Cooperative Lidar Experiments), an autonomously operated, compact DIAL instrument to be placed in orbit using a Pegasus class launch vehicle.

Links between extreme UV-radiation, total ozone, surface albedo and cloudiness: An analysis of 30 years of data from Switzerland and Austria

NASA Astrophysics Data System (ADS)

Rieder, H. E.; Staehelin, J.; Weihs, P.; Vuilleumier, L.; Blumthaler, M.; Holawe, F.; Lindfors, A.; Maeder, J. A.; Simic, S.; Wagner, J. E.; Walker, D.; Ribatet, M.

2009-04-01

Since the discovery of anthropogenic ozone depletion in the early 1970s (e.g. Molina and Rowland, 1974; Farman et al., 1985) the interest in stratospheric ozone trends and solar UV-B increased within the scientific community and the general public because of the link between reduced total column ozone and increased UV-radiation doses. Stratospheric ozone (e.g. Koch et al., 2005) and erythemal UV-radiation (e.g. Rieder et al., 2008) in the northern mid-latitudes are characterized by strong temporal variability. Long-term measurements of UV-B radiation are rare and datasets are only available for few locations and most of these measurements do not provide spectral information on the UV part of the spectra. During strong efforts in the reconstruction of erythemal UV, datasets of past UV-radiation doses became available for several measurement sites all over the globe. For Switzerland and Austria reconstructed UV datasets are available for 3 measurement sites (Davos, Sonnblick and Vienna) (Lindfors and Vuilleumier, 2005; Rieder et al., 2008). The world's longest ozone time series dating back to 1926 is available from Arosa, Switzerland, and is discussed in detail by Staehelin et al. (1998a,b). Recently new tools from extreme value theory have been applied to the Arosa time series to describe extreme events in low and high total ozone (Rieder et al., 2009). In our study we address the question of how much of the extremes in UV-radiation can be attributed to extremes in total ozone, high surface albedo and cloudiness. An analysis of the frequency distributions of such extreme events for the last decades is presented to gain a better understanding of the links between extreme erythemal UV-radiation, total ozone, surface albedo and clouds. References: Farman, J. C., Gardiner, B. G., and Shanklin, J. D.: Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction, Nature, 315, 207-210, 1985. Koch, G., Wernli, H., Schwierz, C., Staehelin, J., and Peter, T.: A composite study on the structure and formation of ozone miniholes and minihights over central Europe, J. Geophys. Res., 32, doi:10.1029/2004GL022062, 2005. Lindfors, A., and Vuilleumier, L.: Erythemal UV at Davos (Switzerland), 1926-2003, estimated using total ozone, sunshine duration, and snow depth, J. Geophys. Res., 110, D02104, doi:10.1029/2004JD005231, 2005. Molina, M. J., and Rowland, F. S.: Stratospheric sink for chlorofluoromethans: Chlorine atom-catalysed destruction of ozone, Nature, 249, 810-812, 1974. Rieder, H.E., Holawe, F., Simic, S., Blumthaler, M., Krzyscin, J.W., Wagner J.E., Schmalwieser A.W., and Weihs, P.: Reconstruction of erythemal UV-doses for two stations in Austria: A comparison between alpine and urban regions, Atmos. Chem. Phys., 8, 6309-6323, 2008. Rieder, H.E., Staehelin, J., Maeder, J.A., Ribatet, M., Stübi, R., Weihs, P., Holawe, F., Peter, T., and Davison, A.C.: From ozone mini holes and mini highs towards extreme value theory: New insights from extreme events and non stationarity, submitted to J. Geophys. Res., 2009. Staehelin, J., Kegel, R., and Harris, N. R.: Trend analysis of the homogenized total ozone series of Arosa (Switzerland), 1929-1996, J. Geophys. Res., 103(D7), 8389-8400, doi:10.1029/97JD03650, 1998a. Staehelin, J., Renaud, A., Bader, J., McPeters, R., Viatte, P., Hoegger, B., Bugnion, V., Giroud, M., and Schill, H.: Total ozone series at Arosa (Switzerland): Homogenization and data comparison, J. Geophys. Res., 103(D5), 5827-5842, doi:10.1029/97JD02402, 1998b.

Evaluation of emission control strategies to reduce ozone pollution in the Paso del Norte region using a photochemical air quality modeling system

NASA Astrophysics Data System (ADS)

Valenzuela, Victor Hugo

Air pollution emissions control strategies to reduce ozone precursor pollutants are analyzed by applying a photochemical modeling system. Simulations of air quality conditions during an ozone episode which occurred in June, 2006 are undertaken by increasing or reducing area source emissions in Ciudad Juarez, Chihuahua, Mexico. Two air pollutants are primary drivers in the formation of tropospheric ozone. Oxides of nitrogen (NOx) and volatile organic compounds (VOC) undergo multiple chemical reactions under favorable meteorological conditions to form ozone, which is a secondary pollutant that irritates respiratory systems in sensitive individuals especially the elderly and young children. The U.S. Environmental Protection Agency established National Ambient Air Quality Standards (NAAQS) to limit ambient air pollutants such as ozone by establishing an 8-hour average concentration of 0.075 ppm as the threshold at which a violation of the standard occurs. Ozone forms primarily due reactions in the troposphere of NOx and VOC emissions generated primarily by anthropogenic sources in urban regions. Data from emissions inventories indicate area sources account for ˜15 of NOx and ˜45% of regional VOC emissions. Area sources include gasoline stations, automotive paint bodyshops and nonroad mobile sources. Multiplicity of air pollution emissions sources provides an opportunity to investigate and potentially implement air quality improvement strategies to reduce emissions which contribute to elevated ozone concentrations. A baseline modeling scenario was established using the CAMx photochemical air quality model from which a series of sensitivity analyses for evaluating air quality control strategies were conducted. Modifications to area source emissions were made by varying NOx and / or VOC emissions in the areas of particular interest. Model performance was assessed for each sensitivity analysis. Normalized bias (NB) and normalized error (NE) were used to identify variability of the PREDICTED to OBSERVED ozone concentrations of both BASELINE model and simulations with modified emissions assessed by the sensitivity analysis. All simulations were found to vary within acceptable ranges of these two criteria variables. Simulation results indicate ozone formation in the PdN region is VOC-limited. Under VOC-limited conditions, modifications to NOx emissions do not produce a marked increase or decrease in ozone concentrations. Modifications to VOC emissions generated the highest variability in ozone concentrations. Increasing VOC emissions by 75% produced results which minimized model bias and error when comparing PREDICTED and OBSERVED ozone concentrations. Increasing VOC emissions by 75% either alone or in combination with a 75% increase in NOx emissions generated PREDICTED ozone concentrations very near to OBSERVED ozone. By evaluating the changes in ambient ozone concentrations through photochemical modeling, air quality planners may identify the most efficient or effective VOC emissions control strategies for area sources. Among the strategies to achieve emissions reductions are installation of gasoline vapor recovery systems, replacing high-pressure low-volume surface coating paint spray guns with high-volume low-pressure spray paint guns, requiring emissions control booths for surface coating operations as well as undertaking solvent management practices, requiring the sale of low VOC paint solvents in the surface-coating industry, and requiring low-VOC solvents in the dry cleaning industry. Other strategies to reduce VOC emissions include initiating Eco-Driving strategies to reduce fuel consumption from mobile sources and minimize vehicle idling at the international ports of entry by reducing bridge wait times. This dissertation depicts a tool for evaluating impacts of emissions on regional air quality by addressing the highly unresolved fugitive emissions in the Paso del Norte region. It provides a protocol for decision makers to assess the effects of various emission control strategies in the region. Impacts of specific source categories such as the international ports of entry, gasoline stations, paint body shops, truck stops, and military installations on the regional air quality can be easily and systematically addressed in a timely manner in the future.

Improving Aerosol and Visibility Forecasting Capabilities Using Current and Future Generations of Satellite Observations

DTIC Science & Technology

2012-09-30

improving forecast performance over cloudy regions using the Ozone Monitoring Instrument (OMI) Aerosol Index; and 2) preparing for the post-MODIS...meteorological fields, the International Geosphere-Biosphere Programme (IGBP) SW and LW surface characteristics, and an ozone climatology are used as...The primary impact of CALIOP assimilation on the model is the redistribution of mass toward the boundary layer from the free troposphere . For high

On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

NASA Astrophysics Data System (ADS)

Akritidis, Dimitris; Pozzer, Andrea; Zanis, Prodromos; Tyrlis, Evangelos; Škerlak, Bojan; Sprenger, Michael; Lelieveld, Jos

2016-11-01

We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

Impact of parameterization choices on the restitution of ozone deposition over vegetation

NASA Astrophysics Data System (ADS)

Le Morvan-Quéméner, Aurélie; Coll, Isabelle; Kammer, Julien; Lamaud, Eric; Loubet, Benjamin; Personne, Erwan; Stella, Patrick

2018-04-01

Ozone is a potentially phyto-toxic air pollutant, which can cause leaf damage and drastically alter crop yields, causing serious economic losses around the world. The VULNOZ (VULNerability to OZone in Anthropised Ecosystems) project is a biology and modeling project that aims to understand how plants respond to the stress of high ozone concentrations, then use a set of models to (i) predict the impact of ozone on plant growth, (ii) represent ozone deposition fluxes to vegetation, and finally (iii) estimate the economic consequences of an increasing ozone background the future. In this work, as part of the VULNOZ project, an innovative representation of ozone deposition to vegetation was developed and implemented in the CHIMERE regional chemistry-transport model. This type of model calculates the average amount of ozone deposited on a parcel each hour, as well as the integrated amount of ozone deposited to the surface at the regional or country level. Our new approach was based on a refinement of the representation of crop types in the model and the use of empirical parameters specific to each crop category. The results obtained were compared with a conventional ozone deposition modeling approach, and evaluated against observations from several agricultural areas in France. They showed that a better representation of the distribution between stomatal and non-stomatal ozone fluxes was obtained in the empirical approach, and they allowed us to produce a new estimate of the total amount of ozone deposited on the subtypes of vegetation at the national level.

An evaluation of in situ ozone sensor performance during a cold frontal passage

NASA Technical Reports Server (NTRS)

Parsons, C. L.

1978-01-01

The capabilities of the electrochemical concentration cell ozonesonde for measuring the vertical profile of atmospheric ozone were studied during a three day experiment at Wallops Island, Virginia, and Norfolk, Virginia. Using ancillary measurements at the surface and the spectrophotometer, it was concluded that the ozonesonde measures the total ozone overburden to within 10% of the real value. By releasing the balloon-borne instruments at a rate of four per day at each of the two sites, an indication was obtained of the temporal and spatial scales of atmospheric ozone variability. No significant effects of a weak cold front passage or of the loss of insolation at night were seen. An isolated incident of anomalously high ozone concentration at the peak of the profile was attributed to sporadic instrument performance effects. The data base currently available is not adequate for determining an exact cause of the anomaly.

Global Ozone Distribution relevant to Human Health: Metrics and present day levels from the Tropospheric Ozone Assessment Report (TOAR)

NASA Astrophysics Data System (ADS)

Fleming, Z. L.; Doherty, R. M.; von Schneidemesser, E.; Cooper, O. R.; Malley, C.; Colette, A.; Xu, X.; Pinto, J. P.; Simpson, D.; Schultz, M. G.; Hamad, S.; Moola, R.; Solberg, S.; Feng, Z.

2017-12-01

Using stations from the TOAR surface ozone database, this study quantifies present-day global and regional distributions of five ozone metrics relevant for both short-term and long-term human exposure. These metrics were explored at ozone monitoring sites globally, and re-classified for this project as urban or non-urban using population densities and night-time lights. National surface ozone limit values are usually related to an annual number of exceedances of daily maximum 8-hour running mean (MDA8), with many countries not even having any ozone limit values. A discussion and comparison of exceedances in the different ozone metrics, their locations and the seasonality of exceedances provides clues as to the regions that potentially have more serious ozone health implications. Present day ozone levels (2010-2014) have been compared globally and show definite geographical differences (see Figure showing the annual 4th highest MDA8 for present day ozone for all non-urban stations). Higher ozone levels are seen in western compared to eastern US, and between southern and northern Europe, and generally higher levels in east Asia. The metrics reflective of peak concentrations show highest values in western North America, southern Europe and East Asia. A number of the metrics show similar distributions of North-South gradients, most prominent across Europe and Japan. The interquartile range of the regional ozone metrics was largest in East Asia, higher for urban stations in Asia but higher for non-urban stations in Europe and North America. With over 3000 monitoring stations included in this analysis and despite the higher densities of monitoring stations in Europe, north America and East Asia, this study provides the most comprehensive global picture to date of surface ozone levels in terms of health-relevant metrics.

Ozone and photocatalytic processes to remove the antibiotic sulfamethoxazole from water.

PubMed

Beltrán, Fernando J; Aguinaco, Almudena; García-Araya, Juan F; Oropesa, Ana

2008-08-01

In this study, water containing the pharmaceutical compound sulfamethoxazole (SMT) was subjected to the various treatments of different oxidation processes involving ozonation, and photolysis and catalysis under different experimental conditions. Removal rates of SMT and total organic carbon (TOC), from experiments of simple UVA radiation, ozonation (O(3)), catalytic ozonation (O(3)/TiO(2)), ozone photolysis (O(3)/UVA), photocatalytic oxidation (O(2)/TiO(2)/UVA) and photocatalytic ozonation (O(3)/UVA/TiO(2)), have been compared. Photocatalytic ozonation leads to the highest SMT removal rate (pH 7 in buffered systems, complete removal is achieved in less than 5min) and total organic carbon (in unbuffered systems, with initial pH=4, 93% TOC removal is reached). Also, lowest ozone consumption per TOC removed and toxicity was achieved with the O(3)/UVA/TiO(2) process. Direct ozone and free radical reactions were found to be the principal mechanisms for SMT and TOC removal, respectively. In photocatalytic ozonation, with buffered (pH 7) aqueous solutions phosphates (buffering salts) and accumulation of bicarbonate scavengers inhibit the reactions completely on the TiO(2) surface. As a consequence, TOC removal diminishes. In all cases, hydrogen peroxide plays a key role in TOC mineralization. According to the results obtained in this work the use of photocatalytic ozonation is recommended to achieve a high mineralization degree of water containing SMT type compounds.

Attribution of Trends and Variability in Surface Ozone over the United States

NASA Technical Reports Server (NTRS)

Strode, Sarah; Cooper, Owen; Damo, Megan; Logan, Jennifer; Rodriquez, Jose; Strahan, Susan; Witte, Jacquie

2013-01-01

Concentrations of tropospheric ozone, a greenhouse gas and air pollutant, are impacted by changes in precursor emissions as well meteorology and influx from the stratosphere. Observations show a decreasing trend in summertime surface ozone at rural stations in the eastern United States, while some western stations show increasing trends, particularly in springtime. We use the Global Modeling Initiative (GMI) global chemical transport model to investigate the roles of precursor emission changes, meteorological variability, and stratosphere-troposphere exchange (STE) in explaining observed trends in surface ozone from rural sites in the United States from 1991-2010. The model's interannual variability shows significant correlations with observations from many of the surface sites. We also compare the simulated ozone to ozonesonde data for several locations with sufficiently long records. We compare a simulation with time-dependent precursor emissions, including emission reductions over the United States and Europe and increases over Asia, to a simulation with fixed emissions to quantify the impact of changing emissions on the surface trends. The simulation with varying emissions reproduces much of the east-west difference in summertime ozone over the U.S., although it generally underestimates the negative trend in the East. In contrast, the fixed-emission simulation shows increasing ozone at both eastern and western sites. We will discuss possible causes of this behavior, including long-range transport and STE.

Extended and refined multi sensor reanalysis of total ozone for the period 1970-2012

NASA Astrophysics Data System (ADS)

van der A, R. J.; Allaart, M. A. F.; Eskes, H. J.

2015-07-01

The ozone multi-sensor reanalysis (MSR) is a multi-decadal ozone column data record constructed using all available ozone column satellite data sets, surface Brewer and Dobson observations and a data assimilation technique with detailed error modelling. The result is a high-resolution time series of 6-hourly global ozone column fields and forecast error fields that may be used for ozone trend analyses as well as detailed case studies. The ozone MSR is produced in two steps. First, the latest reprocessed versions of all available ozone column satellite data sets are collected and then are corrected for biases as a function of solar zenith angle (SZA), viewing zenith angle (VZA), time (trend), and stratospheric temperature using surface observations of the ozone column from Brewer and Dobson spectrophotometers from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Subsequently the de-biased satellite observations are assimilated within the ozone chemistry and data assimilation model TMDAM. The MSR2 (MSR version 2) reanalysis upgrade described in this paper consists of an ozone record for the 43-year period 1970-2012. The chemistry transport model and data assimilation system have been adapted to improve the resolution, error modelling and processing speed. Backscatter ultraviolet (BUV) satellite observations have been included for the period 1970-1977. The total record is extended by 13 years compared to the first version of the ozone multi sensor reanalysis, the MSR1. The latest total ozone retrievals of 15 satellite instruments are used: BUV-Nimbus4, TOMS-Nimbus7, TOMS-EP, SBUV-7, -9, -11, -14, -16, -17, -18, -19, GOME, SCIAMACHY, OMI and GOME-2. The resolution of the model runs, assimilation and output is increased from 2° × 3° to 1° × 1°. The analysis is driven by 3-hourly meteorology from the ERA-Interim reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) starting from 1979, and ERA-40 before that date. The chemistry parameterization has been updated. The performance of the MSR2 analysis is studied with the help of observation-minus-forecast (OmF) departures from the data assimilation, by comparisons with the individual station observations and with ozone sondes. The OmF statistics show that the mean bias of the MSR2 analyses is less than 1 % with respect to de-biased satellite observations after 1979.

Convective storms and non-classical low-level jets during high ozone level episodes in the Amazon region: An ARM/GOAMAZON case study

NASA Astrophysics Data System (ADS)

Dias-Junior, Cléo Q.; Dias, Nelson Luís; Fuentes, José D.; Chamecki, Marcelo

2017-04-01

In this work, we investigate the ozone dynamics during the occurrence of both downdrafts associated with mesoscale convective storms and non-classical low-level jets. Extensive data sets, comprised of air chemistry and meteorological observations made in the Amazon region of Brazil over the course of 2014-15, are analyzed to address several questions. A first objective is to investigate the atmospheric thermodynamic and dynamic conditions associated with storm-generated ozone enhancements in the Amazon region. A second objective is to determine the magnitude and the frequency of ground-level ozone enhancements related to low-level jets. Ozone enhancements are analyzed as a function of wind shear, low-level jet maximum wind speed, and altitude of jet core. Strong and sudden increases in ozone levels are associated with simultaneous changes in variables such as horizontal wind speed, convective available potential energy, turbulence intensity and vertical velocity skewness. Rapid increases in vertical velocity skewness give support to the hypothesis that the ozone enhancements are directly related to downdrafts. Low-level jets associated with advancing density currents are often present during and after storm downdrafts that transport ozone-enriched air from aloft to the surface.

The impact of drought on ozone dry deposition over eastern Texas

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Studies on Stratospheric Moistening and Its Effect on Ozone Depletion in Global Perspective

NASA Astrophysics Data System (ADS)

Saha, Upal; Maitra, Animesh; Adhikari, Arpita

2012-07-01

Stratospheric moistening is the water vapor intrusion in the stratosphere which affects ozone, surface climate and stratospheric temperatures. Increased stratospheric water vapor can be an important cause of global warming as it acts to cool the stratosphere but warms the underlying troposphere. Stratospheric moistening is controlled by the transport through the tropopause region and the oxidation of methane within the stratosphere. In this article, variations of stratospheric moistening and stratospheric ozone over the whole Globe, equatorial region, mid latitudinal region, polar region are reported during the years from 2004 to 2011 using the Aura's Microwave Limb Sounder (MLS) water vapor data and Earth Probe TOMS ozone data. Maximum stratospheric moistening over the Globe is found to occur during boreal summer months although it is high during boreal winter months. The stratospheric ozone over Globe remains high during the pre-boreal summer months and decreases during the boreal winter. The mid latitudinal region has the maximum contribution of stratospheric moistening and stratospheric ozone over the Globe. Northern and southern poles have somewhat less contribution of stratospheric moistening. Stratospheric moistening over North Polar and mid latitudinal region is high during boreal summer months but over South Polar and mid latitudinal region it is high during boreal winter months. It is also found that stratospheric moistening has increased since 2004 and correspondingly stratospheric ozone concentration also decreased. This shows an anti-correlation between stratospheric moistening and stratospheric ozone, which indicates the dominance of prevailing photochemical reactions occurring in the stratosphere. Stratospheric moistening over the Indian and South Asian Monsoon regions has a global contribution of about 0.46% and 0.78% respectively. Latitudinal variation of stratospheric moistening and stratospheric ozone shows a good global inter-relation between them with a significant correlation. Atomic and molecular oxygen are produced due to photo-dissociation of the H2O molecule in the stratosphere. The stratospheric hydroxyl free radicals are responsible to deplete stratospheric ozone into oxygen via combination-recombination reaction. A decrease in stratospheric ozone concentration caused by the OH radical is predominant in the lower stratosphere but this process also extends to troposphere. Thus a decrease of ozone concentration is expected in Indian and South Asian Monsoon region, which will indicate an overview of ozone depletion in global perspective due to stratospheric moistening.

Formation and emissions of carbonyls during and following gas-phase ozonation of indoor materials

NASA Astrophysics Data System (ADS)

Poppendieck, D. G.; Hubbard, H. F.; Weschler, C. J.; Corsi, R. L.

Ozone concentrations that are several orders of magnitude greater than typical urban ambient concentrations are necessary for gas-phase ozonation of buildings, either for deodorization or for disinfection of biological agents. However, there is currently no published literature on the interaction of building materials and ozone under such extreme conditions. It would be useful to understand, for example in the case of building re-occupation planning, what types and amounts of reaction products may form and persist in a building after ozonation. In this study, 24 materials were exposed to ozone at concentrations of 1000 ppm in the inlet stream of experimental chambers. Fifteen target carbonyls were selected and measured as building ozonation by-products (BOBPs). During the 36 h that include the 16 h ozonation and 20 h persistence phase, the total BOBP mass released from flooring and wall coverings ranged from 1 to 20 mg m -2, with most of the carbonyls being of lower molecular weight (C 1-C 4). In contrast, total BOBP mass released from wood-based products ranged from 20 to 100 mg m -2, with a greater fraction of the BOBPs being heavier carbonyls (C 5-C 9). The total BOBP mass released during an ozonation event is a function of both the total surface area of the material and the BOBP emission rate per unit area of material. Ceiling tile, carpet, office partition, and gypsum wallboard with flat latex paint often have large surface areas in commercial buildings and these same materials exhibited relatively high BOBP releases. The greatest overall BOBP mass releases were observed for three materials that building occupants might have significant contact with: paper, office partition, and medium density fiberboard, e.g., often used in office furniture. These materials also exhibited extended BOBP persistence following ozonation; some BOBPs (e.g., nonanal) persist for months or more at emission rates large enough to result in indoor concentrations that exceed their odor threshold.

Atmospheric Oxidation of Squalene: Molecular Study Using COBRA Modeling and High-Resolution Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fooshee, David R.; Aiona, Paige K.; Laskin, Alexander

2015-10-22

Squalene is a major component of skin and plant surface lipids, and is known to be present at high concentrations in indoor dust. Its high reactivity toward ozone makes it an important ozone sink and a natural protectant against atmospheric oxidizing agents. While the volatile products of squalene ozonolysis are known, the condensed-phase products have not been characterized. We present an analysis of condensed-phase products resulting from an extensive oxidation of squalene by ozone probed by electrospray ionization (ESI) high-resolution mass spectrometry (HR-MS). A complex distribution of nearly 1,300 peaks assignable to molecular formulas is observed in direct infusion positivemore » ion mode ESI mass spectra. The distribution of peaks in the mass spectra suggests that there are extensive cross-coupling reactions between hydroxy-carbonyl products of squalene ozonolysis. To get additional insights into the mechanism, we apply a Computational Brewing Application (COBRA) to simulate the oxidation of squalene in the presence of ozone, and compare predicted results with those observed by the HR-MS experiments. The system predicts over one billion molecular structures between 0-1450 Da, which correspond to about 27,000 distinct elemental formulas. Over 83% of the squalene oxidation products inferred from the mass spectrometry data are matched by the simulation. Simulation indicates a prevalence of peroxy groups, with hydroxyl and ether groups being the second-most important O-containing functional groups formed during squalene oxidation. These highly oxidized products of squalene ozonolysis may accumulate on indoor dust and surfaces, and contribute to their redox capacity.« less

Evaluating the effects of climate change on summertime ozone using a relative response factor approach for policymakers.

PubMed

Avise, Jeremy; Abraham, Rodrigo Gonzalez; Chung, Serena H; Chen, Jack; Lamb, Brian; Salathé, Eric P; Zhang, Yongxin; Nolte, Christopher G; Loughlin, Daniel H; Guenther, Alex; Wiedinmyer, Christine; Duhl, Tiffany

2012-09-01

The impact of climate change on surface-level ozone is examined through a multiscale modeling effort that linked global and regional climate models to drive air quality model simulations. Results are quantified in terms of the relative response factor (RRF(E)), which estimates the relative change in peak ozone concentration for a given change in pollutant emissions (the subscript E is added to RRF to remind the reader that the RRF is due to emission changes only). A matrix of model simulations was conducted to examine the individual and combined effects offuture anthropogenic emissions, biogenic emissions, and climate on the RRF(E). For each member in the matrix of simulations the warmest and coolest summers were modeled for the present-day (1995-2004) and future (2045-2054) decades. A climate adjustment factor (CAF(C) or CAF(CB) when biogenic emissions are allowed to change with the future climate) was defined as the ratio of the average daily maximum 8-hr ozone simulated under a future climate to that simulated under the present-day climate, and a climate-adjusted RRF(EC) was calculated (RRF(EC) = RRF(E) x CAF(C)). In general, RRF(EC) > RRF(E), which suggests additional emission controls will be required to achieve the same reduction in ozone that would have been achieved in the absence of climate change. Changes in biogenic emissions generally have a smaller impact on the RRF(E) than does future climate change itself The direction of the biogenic effect appears closely linked to organic-nitrate chemistry and whether ozone formation is limited by volatile organic compounds (VOC) or oxides of nitrogen (NO(x) = NO + NO2). Regions that are generally NO(x) limited show a decrease in ozone and RRF(EC), while VOC-limited regions show an increase in ozone and RRF(EC). Comparing results to a previous study using different climate assumptions and models showed large variability in the CAF(CB). We present a methodology for adjusting the RRF to account for the influence of climate change on ozone. The findings of this work suggest that in some geographic regions, climate change has the potential to negate decreases in surface ozone concentrations that would otherwise be achieved through ozone mitigation strategies. In regions of high biogenic VOC emissions relative to anthropogenic NO(x) emissions, the impact of climate change is somewhat reduced, while the opposite is true in regions of high anthropogenic NO(x) emissions relative to biogenic VOC emissions. Further, different future climate realizations are shown to impact ozone in different ways.

Estimation of ozone dry deposition over Europe for the period 2071-2100

NASA Astrophysics Data System (ADS)

Komjáthy, Eszter; Gelybó, Györgyi; László Lagzi, István.; Mészáros, Róbert

2010-05-01

Ozone in the lower troposphere is a phytotoxic air pollutant which can cause injury to plant tissues, causing reduction in plant growth and productivity. In the last decades, several investigations have been carried out for the purpose to estimate ozone load over different surface types. At the same time, the changes of atmospheric variables as well as surface/vegetation parameters due to the global climate change could also strongly modify both temporal and spatial variations of ozone load over Europe. In this study, the possible effects of climate change on ozone deposition are analyzed. Using a sophisticated deposition model, ozone deposition was estimated on a regular grid over Europe for the period 2071-2100. Our aim is to determine the uncertainties and the possible degree of change in ozone deposition velocity as an important predictor of total ozone load using climate data from multiple climate models and runs. For these model calculations, results of the PRUDENCE (Predicting of Regional Scenarios and Uncertainties for Defining European Climate Change Risks and Effects) climate prediction project were used. As a first step, seasonal variations of ozone deposition over different vegetation types in case of different climate scenarios are presented in this study. Besides model calculations, in the frame of a sensitivity analyses, the effects of surface/vegetation parameters (e.g. leaf area index or stomatal resistance) on ozone deposition under a modified climate regime have also been analyzed.

Effect of dry-ozone exposure on different polymer surfaces and their resulting biocidal action on sporulated bacteria

NASA Astrophysics Data System (ADS)

Mahfoudh, A.; Poncin-Épaillard, F.; Moisan, M.; Barbeau, J.

2010-08-01

The current work describes a novel technique by which certain types of polymers subjected to dry gaseous ozone acquire the ability to inactivate microorganisms, including those as resistant as bacterial spores. The originality and advantages of this ozone treatment of polymer surfaces rest on its simplicity (achieved at ambient temperature and pressure, a one step process …) and its efficacy. The inactivation efficiency is found to be specific to the nature of the treated polymer: 24 h after deposition of 10 6B. atrophaeus spores from a 100 µL suspension, high inactivation rates are observed with polymethyldisiloxane (99.997%, almost 5 log) and polystyrene (99.7%, more than 2 log), a lower rate with polyurethane (99.1%, 2 log) whereas polytetrafluoroethylene shows no detectable biocidal activity. Changes in hydrophilicity of these surfaces are monitored by means of contact-angle measurements while topographic modifications are characterized through atomic force microscopy. Ozone exposure brings about important topographic changes and chemical modifications on some polymers, which can be correlated with oxidation processes, increased wettability and surface energy. Variations of the dispersive and non-dispersive (polar) components of the surface energy are partially correlated with the polymer biocidal response. Furthermore, the basic component of the treated polymer (in contrast to its acidic component) seems to be correlated with the biocidal activity of the treated surfaces. Chemical species bearing ester groups, probably partially-oxidized styrene oligomers, as revealed by chemical analysis, could be involved in the biocidal activity. On practical grounds, since some of these treated polymers can strongly reduce microorganism loads on their surfaces, they could be particularly useful in hospital environment.

Ozone treatment of coal- and coffee grounds-based active carbons: Water vapor adsorption and surface fractal micropores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsunoda, Ryoichi; Ozawa, Takayoshi; Ando, Junichi

1998-09-15

Characteristics of the adsorption iostherms of water vapor on active carbons from coal and coffee grounds and those ozonized ones from the surface fractal dimension analysis are discussed. The upswing of the adsorption isotherms in the low relative pressure of coffee grounds-based active carbon, of which isotherms were not scarcely affected on ozonization, was attributed to the adsorption of water molecules on the metallic oxides playing the role of oxygen-surface complexes, which formed the corrugated surfaces on the basal planes of micropore walls with the surface fractal dimension D{sub s} > 2. On the other hand, coal-based active carbon withmore » D{sub s} < 2, which indicated the flat surfaces of micropore walls, showed little effect on the upswing even on ozonization, even though the adsorption amounts of water vapor were increased in the low relative pressure.« less

Experimental Findings from Aircraft Measurements in the Residual Layer

NASA Astrophysics Data System (ADS)

Caputi, D.; Conley, S. A.; Faloona, I. C.; Trousdell, J.

2016-12-01

The southern San Joaquin Valley of California is home to some of the highest ozone pollution in the United States. Thus, a complete understanding of boundary layer dynamics in this area during high ozone events is crucial for better ozone forecasting and effective attainment planning. This work will discuss the results from five aircraft deployments, spanning two summers, in which a Mooney aircraft operated by Scientific Aviation Inc. was flown between Fresno and Bakersfield throughout the diurnal cycle, measuring ozone, NOx, and methane. Under a simple budgeting model, changes in any species within the boundary layer can occur from advection, chemical production or loss, surface fluxes or deposition, and entrainment between the boundary layer and free troposphere. The advection of ozone appears to be most appreciable at night with stronger winds in the residual layer, and are on the order of 2 to 4 ppb hr-1. The nighttime chemical loss of ozone due to interaction with NO2 can be estimated by simple numerical modeling of observed quantities and reaction rates, and is found to often roughly compensate for the advection, with typical calculated values of -1 to -3 ppb hr-1. The mixing component is more difficult to directly quantify, but attempts are being made to estimate eddy viscosity by solving for this term in the budget equation. Additionally, small-scale features, such as nocturnal elevated mixed layers, localized BRN (bulk Richardson number) minimums, and low level jets are spotted in systematic ways throughout the flight data, and it is speculated that these may have a role in the transfer of ozone from the residual layer to the surface layer. Ultimately, the preliminary data is promising for the eventual goal of linking together the observed boundary layer evolution with ozone production during air pollution episodes.

The influence of temperature on ozone production under varying NOx conditions - a modelling study

NASA Astrophysics Data System (ADS)

Coates, Jane; Mar, Kathleen A.; Ojha, Narendra; Butler, Tim M.

2016-09-01

Surface ozone is a secondary air pollutant produced during the atmospheric photochemical degradation of emitted volatile organic compounds (VOCs) in the presence of sunlight and nitrogen oxides (NOx). Temperature directly influences ozone production through speeding up the rates of chemical reactions and increasing the emissions of VOCs, such as isoprene, from vegetation. In this study, we used an idealised box model with different chemical mechanisms (Master Chemical Mechanism, MCMv3.2; Common Representative Intermediates, CRIv2; Model for OZone and Related Chemical Tracers, MOZART-4; Regional Acid Deposition Model, RADM2; Carbon Bond Mechanism, CB05) to examine the non-linear relationship between ozone, NOx and temperature, and we compared this to previous observational studies. Under high-NOx conditions, an increase in ozone from 20 to 40 °C of up to 20 ppbv was due to faster reaction rates, while increased isoprene emissions added up to a further 11 ppbv of ozone. The largest inter-mechanism differences were obtained at high temperatures and high-NOx emissions. CB05 and RADM2 simulated more NOx-sensitive chemistry than MCMv3.2, CRIv2 and MOZART-4, which could lead to different mitigation strategies being proposed depending on the chemical mechanism. The increased oxidation rate of emitted VOC with temperature controlled the rate of Ox production; the net influence of peroxy nitrates increased net Ox production per molecule of emitted VOC oxidised. The rate of increase in ozone mixing ratios with temperature from our box model simulations was about half the rate of increase in ozone with temperature observed over central Europe or simulated by a regional chemistry transport model. Modifying the box model set-up to approximate stagnant meteorological conditions increased the rate of increase of ozone with temperature as the accumulation of oxidants enhanced ozone production through the increased production of peroxy radicals from the secondary degradation of emitted VOCs. The box model simulations approximating stagnant conditions and the maximal ozone production chemical regime reproduced the 2 ppbv increase in ozone per degree Celsius from the observational and regional model data over central Europe. The simulated ozone-temperature relationship was more sensitive to mixing than the choice of chemical mechanism. Our analysis suggests that reductions in NOx emissions would be required to offset the additional ozone production due to an increase in temperature in the future.

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

NASA Astrophysics Data System (ADS)

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. This historic surface ozone analysis provides a new test for historical reconstructions by Climate-Chemistry models.

Rate acceleration of the heterogeneous reaction of ozone with a model alkene at the air-ice interface at low temperatures.

PubMed

Ray, Debajyoti; Malongwe, Joseph K'Ekuboni; Klán, Petr

2013-07-02

The kinetics of the ozonation reaction of 1,1-diphenylethylene (DPE) on the surface of ice grains (also called "artificial snow"), produced by shock-freezing of DPE aqueous solutions or DPE vapor-deposition on pure ice grains, was studied in the temperature range of 268 to 188 K. A remarkable and unexpected increase in the apparent ozonation rates with decreasing temperature was evaluated using the Langmuir-Hinshelwood and Eley-Rideal kinetic models, and by estimating the apparent specific surface area of the ice grains. We suggest that an increase of the number of surface reactive sites, and possibly higher ozone uptake coefficients are responsible for the apparent rate acceleration of DPE ozonation at the air-ice interface at lower temperatures. The increasing number of reactive sites is probably related to the fact that organic molecules are displaced more to the top of a disordered interface (or quasi-liquid) layer on the ice surface, which makes them more accessible to the gas-phase reactants. The effect of NaCl as a cocontaminant on ozonation rates was also investigated. The environmental implications of this phenomenon for natural ice/snow are discussed. DPE was selected as an example of environmentally relevant species which can react with ozone. For typical atmospheric ozone concentrations in polar areas (20 ppbv), we estimated that its half-life on the ice surface would decrease from ∼5 days at 258 K to ∼13 h at 188 K at submonolayer DPE loadings.

A novel "wastes-treat-wastes" technology: role and potential of spent fluid catalytic cracking catalyst assisted ozonation of petrochemical wastewater.

PubMed

Chen, Chunmao; Yu, Ji; Yoza, Brandon A; Li, Qing X; Wang, Gang

2015-04-01

Catalytic ozonation is a promising wastewater treatment technology. However, the high cost of the catalyst hinders its application. A novel "wastes-treat-wastes" technology was developed to reuse spent fluid catalytic cracking catalysts (sFCCc) for the ozonation of petrochemical wastewater in this study. Multivalent vanadium (V(4+) and V(5+)), iron (Fe(2+) and Fe(3+)) and nickel (Ni(2+)) oxides that are distributed on the surface of sFCCc and poisoned FCC catalysts are the catalytic components for ozonation. The sFCCc assisted catalytic ozonation (sFCCc-O) of nitrobenzene indicated that the sFCCc significantly promoted hydroxyl radical mediated oxidation. The degradation rate constant of nitrobenzene in sFCCc-O (0.0794 min(-1) at 298 K) was approximately doubled in comparison with that in single ozonation (0.0362 min(-1) at 298 K). The sFCCc-O of petrochemical wastewater increased chemical oxygen demand removal efficiency by three-fold relative to single ozonation. The number of oxygen-containing (Ox) polar contaminants in the effluent (253) from sFCCc-O treatment decreased to about 70% of the initial wastewater (353). The increased oxygen/carbon atomic ratio and decreased number of Ox polar contaminants indicated a high degree of degradation. The present study showed the role and potential of sFCCc for catalytic ozonation of petrochemical wastewater, particularly in an advantage of the cost-effectiveness through "wastes-treat-wastes". Copyright © 2015 Elsevier Ltd. All rights reserved.

Development and (evidence for) destruction of biofilm with Pseudomonas aeruginosa as architect

NASA Technical Reports Server (NTRS)

Uzcategui, Valerie N.; Donadeo, John J.; Lombardi, Daniel R.; Costello, Michael J.; Sauer, Richard L.

1991-01-01

Disinfection and maintenance of an acceptable level of asepsis in spacecraft potable water delivery systems is a formidable task. The major area of research for this project has been to monitor the formation and growth of biofilm, and biofilm attached microorganisms, on stainless steel surfaces (specifically coupons), and the use of ozone for the elimination of these species in a closed loop system. A number of different techniques have been utilized during the course of a typical run. Scraping and sonication of coupon surfaces with subsequent plating as well as epifluorescence microscopy have been utilized to enumerate biofilm protected Pseudomonas aeruginosa. In addition, scanning electron microscopy is the method of choice to examine the integrity of the biofilm. For ozone determinations, the indigo decolorization spectrophotometric method seems most reliable. Both high- and low-nutrient cultured P. aeruginosa organisms were the target species for the ozone disinfection experiments.

Stage-specific, Nonlinear Surface Ozone Damage to Rice Production in China

NASA Astrophysics Data System (ADS)

Carter, Colin A.; Cui, Xiaomeng; Ding, Aijun; Ghanem, Dalia; Jiang, Fei; Yi, Fujin; Zhong, Funing

2017-03-01

China is one of the most heavily polluted nations and is also the largest agricultural producer. There are relatively few studies measuring the effects of pollution on crop yields in China, and most are based on experiments or simulation methods. We use observational data to study the impact of increased air pollution (surface ozone) on rice yields in Southeast China. We examine nonlinearities in the relationship between rice yields and ozone concentrations and find that an additional day with a maximum ozone concentration greater than 120 ppb is associated with a yield loss of 1.12% ± 0.83% relative to a day with maximum ozone concentration less than 60 ppb. We find that increases in mean ozone concentrations, SUM60, and AOT40 during panicle formation are associated with statistically significant yield losses, whereas such increases before and after panicle formation are not. We conclude that heightened surface ozone levels will potentially lead to reductions in rice yields that are large enough to have implications for the global rice market.

Effect of Ventilation Strategies on Residential Ozone Levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Iain S.; Sherman, Max H.

Elevated outdoor ozone levels are associated with adverse health effects. Because people spend the vast majority of their time indoors, reduction in indoor levels of ozone of outdoor origin would lower population exposures and might also lead to a reduction in ozone-associated adverse health effects. In most buildings, indoor ozone levels are diminished with respect to outdoor levels to an extent that depends on surface reactions and on the degree to which ozone penetrates the building envelope. Ozone enters buildings from outdoors together with the airflows that are driven by natural and mechanical means, including deliberate ventilation used to reducemore » concentrations of indoor-generated pollutants. When assessing the effect of deliberate ventilation on occupant health one should consider not only the positive effects on removing pollutants of indoor origin but also the possibility that enhanced ventilation might increase indoor levels of pollutants originating outdoors. This study considers how changes in residential ventilation that are designed to comply with ASHRAE Standard 62.2 might influence indoor levels of ozone. Simulation results show that the building envelope can contribute significantly to filtration of ozone. Consequently, the use of exhaust ventilation systems is predicted to produce lower indoor ozone concentrations than would occur with balanced ventilation systems operating at the same air-­exchange rate. We also investigated a strategy for reducing exposure to ozone that would deliberately reduce ventilation rates during times of high outdoor ozone concentration while still meeting daily average ventilation requirements.« less

An Overview of the SOLVE-THESEO 2000 Campaign

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Harris, Neil R. P.; Adriani, Alberto; Amanatidis, Georgios T.; Anderson, James G.; Braathen, Geir O.; Brune, William H.; Carslaw, Kenneth S.; Craig, Michael T.; DeCola, Philip E.

2001-01-01

Between November 1999 and April 2000, two major field experiments, the SAGE III Ozone Loss and Validation Experiment (SOLVE) and the Third European Stratospheric Experiment on Ozone (THESEO 2000), collaborated to form the largest field campaign yet mounted to study Arctic ozone loss. This international campaign involved more than 500 scientists from over 20 countries spread across the high and mid-latitudes of the northern hemisphere. The main scientific aims of SOLVE-THESEO 2000 were to study (a) the processes leading to ozone loss in the Arctic vortex and (b) the effect on ozone amounts over northern mid-latitudes. The campaign included satellites, heavy lift balloon launches, 6 different aircraft, ground stations, and scores of ozone-sonde. Campaign activities were principally conducted in 3 intensive measurement phases centered on early December 1999, late January 2000, and early March 2000. Observations made during the campaign showed that temperatures were unusually cold in the polar lower stratosphere over the course of the 1999-2000 winter. These cold temperatures resulted in the formation of extensive polar stratospheric clouds (PSCs) across the Arctic. Heterogeneous chemical reactions on the surfaces of the PSC particles produced high levels of reactive chlorine within the polar vortex by early January. This reactive chlorine catalytically destroyed about 60% of the ozone in a layer near 20 km between late January and mid-March 2000.

Characterization of ozone decomposition in a soil slurry: kinetics and mechanism.

PubMed

Lim, Hyung-Nam; Choi, Hechul; Hwang, Tae-Moon; Kang, Joon-Wun

2002-01-01

A series of soil slurry experiments were performed in a carefully conceived reactor set-up to investigate the characteristics of the catalytic decomposition of ozone on a sand and iron surface. Real time on-line monitoring of ozone in the reaction module was possible using flow injection analysis coupled with a computer-controlled UV detector and data acquisition system. The effects of the soil media and size, ozone dosage, pH and p-CBA as a probe compound were examined at the given experimental conditions. Two apparent phases existed, and ozone instantaneously decomposed within one second in the first phase. These were defined as the instantaneous ozone demand (ID) phase, and the relatively slow decay stage. The interactions of ozone with the soil organic matter (SOM) and metal oxides were attributed mostly to the instantaneous decomposition of ozone. From the probe (p-CBA) experiments, 60-68% of total p-CBA removal occurred during the ID phase. The generation of hydroxyl radicals (OH.) was demonstrated and was closely related with metal oxides as well as SOM. Metal oxides in soil surface were considered to have relatively faster reaction rate with ozone and provide more favorable reactive sites to generate higher amount of OH. than SOM. Even at one-tenth concentration of the sands, a goethite-induced catalytic reaction outfitted the removal rate ofp-CBA among all the soils tested. More than 40% of total p-CBA removal occurred on the soil surface. It was inferred that the radical reaction with the probe compound seemed to take place not only on the soil surface but also in the solid-liquid interface. Ozone decomposition and the reaction between OH. and p-CBA appeared to be independent of any change in pH.

[Effect of ozone on membrane fouling in water and wastewater treatment: a research review].

PubMed

Zhu, Hong-tao; Wen, Xiang-hua; Huang, Xia

2009-01-01

As a high efficient water and wastewater treatment technology, membrane filtration has been mainly used in wastewater treatment as membrane bioreactor, in reclaiming secondary effluent,treating surface water and potable water, and etc. Membrane fouling is a main obstacle to the wide application of membrane technology. Ozone has strong oxidizing power and has been utilized widely in water and wastewater treatment. In recent years, researches on combined process of ozone-membrane filtration are increasing. This paper does reviews and analysis of these researches. It is noticed that there has been a few of researches on the ozone treatment plus MBR process. Pre-ozonation of feed to MBR and slight ozonation of the mixed liquid in MBR may be used to relieve membrane fouling.Combined processes of ozone-membrane filtration can be divided into three classes in terms of the function of ozone and the system configuration: (1) cleaning the fouled membrane with ozone; (2) separate ozone-membrane filtration process; (3) integrated ozone-membrane filtration process. Although most reports supported that ozonation can control membrane fouling development,there were contrary results. At present, researches on the mechanisms of ozone's effect on membrane fouling control concentrated on the change of organic composition of the filtration influent under ozonation, however, particulate substances, microbial and inorganic substances may also be affected and then play roles in membrane fouling, depending on source water quality and process configuration. Moreover, there have not been common parameters to evaluate the ozone diffusion equipment and efficiency. The authors suggest that further researches should emphasize on integrated ozone-membrane process, and more attention should be paid to the cost-effectiveness of the combined process.

Ozone treatment of shell eggs to preserve functional quality and enhance shelf life during storage.

PubMed

Yüceer, Muhammed; Aday, Mehmet Seçkin; Caner, Cengiz

2016-06-01

Eggs have long been recognised as a source of high-quality proteins. Many methods exist to extend shelf life of food and one of them is ozone treatment, which is an emerging technology for disinfecting surfaces in the food industry. This study aimed to extend the shelf life of fresh eggs using gaseous ozone treatments at concentrations of 2, 4 and 6 ppm with exposure times of 2 and 5 min during storage for 6 weeks at 24 °C. The effect of the treatments on interior quality and functional properties of eggs is also reported. Ozone concentration and exposure time significantly affected the Haugh unit (HU), yolk index, albumen pH, relative whipping capacity (RWC), and albumen viscosity of eggs during the storage. Control eggs had the highest albumen pH and lowest albumen viscosity. Attributes such as albumen pH and RWC of eggs exposed to ozone treatments were better than the control samples. The measurement results showed that ozone concentration at 6 ppm and exposure time of 5 min can be applied to fresh eggs and extend shelf life up to 6 weeks at 24 °C storage period. Ozone treatments helped to maintain egg quality for a longer time. Ozone concentrations at 2 and 4 ppm showed promising results in maintaining internal quality and functional properties of fresh eggs during storage. Ozone at high concentration (6 ppm) caused a detrimental effect on eggshell quality. As a result, this study demonstrated that ozone treatments of 2, and especially 4 and 6 ppm concentration maintained eggshell quality during the storage. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean.

PubMed

Read, Katie A; Mahajan, Anoop S; Carpenter, Lucy J; Evans, Mathew J; Faria, Bruno V E; Heard, Dwayne E; Hopkins, James R; Lee, James D; Moller, Sarah J; Lewis, Alastair C; Mendes, Luis; McQuaid, James B; Oetjen, Hilke; Saiz-Lopez, Alfonso; Pilling, Michael J; Plane, John M C

2008-06-26

Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation; the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open-ocean marine sources has been postulated by numerical models, but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year-round data set of co-located in situ surface trace gas measurements made in conjunction with low-level aircraft observations shows that the mean daily observed ozone loss is approximately 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.

Impact of ozonation on particle aggregation in mature fine tailings.

PubMed

Liang, Jiaming; Tumpa, Fahmida; Pérez Estrada, Leonidas; Gamal El-Din, Mohamed; Liu, Yang

2014-12-15

The extraction of bitumen from the oil sands in Canada generates tonnes of mature fine tailings (MFT), consisting of a mineral matrix of sand, clay, and water, which without treatment requires thousands of years to fully consolidate. We assessed the performance of a novel ozonation method designed to enhance the settling of MFT and explored the mechanisms involved. The solid content of MFT obtained from oil sands tailings was adjusted to 1, 3, 5 wt % with water before applying 15, 30, and 60 min of ozonation. MFT settled after a short (15 min) ozonation treatment, resulting in a sample with clear released water on the top and condensed sludge at the bottom. The water chemistry characteristics, particles' surface charge and chemical bonding were measured. Ozonation led to the increased organic acids concentrations in MFT suspension through converting of organic matter from high to low molecular weight, and detaching organic coating on MFT particles. The pH and the concentrations of ions in the MFT suspension were changed significantly, an association of metal ions with MFT particles was promoted, and the surface charges of MFT particles were neutralized. Consequently, the MFT suspension was destabilized and MFT particle precipitation was observed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Stratospheric ozone changes under solar geoengineering: implications for UV exposure and air quality

NASA Astrophysics Data System (ADS)

Nowack, Peer Johannes; Abraham, Nathan Luke; Braesicke, Peter; Pyle, John Adrian

2016-03-01

Various forms of geoengineering have been proposed to counter anthropogenic climate change. Methods which aim to modify the Earth's energy balance by reducing insolation are often subsumed under the term solar radiation management (SRM). Here, we present results of a standard SRM modelling experiment in which the incoming solar irradiance is reduced to offset the global mean warming induced by a quadrupling of atmospheric carbon dioxide. For the first time in an atmosphere-ocean coupled climate model, we include atmospheric composition feedbacks for this experiment. While the SRM scheme considered here could offset greenhouse gas induced global mean surface warming, it leads to important changes in atmospheric composition. We find large stratospheric ozone increases that induce significant reductions in surface UV-B irradiance, which would have implications for vitamin D production. In addition, the higher stratospheric ozone levels lead to decreased ozone photolysis in the troposphere. In combination with lower atmospheric specific humidity under SRM, this results in overall surface ozone concentration increases in the idealized G1 experiment. Both UV-B and surface ozone changes are important for human health. We therefore highlight that both stratospheric and tropospheric ozone changes must be considered in the assessment of any SRM scheme, due to their important roles in regulating UV exposure and air quality.

Summary of aircraft results for 1978 southeastern Virginia urban plume measurement study of ozone, nitrogen oxides, and methane

NASA Technical Reports Server (NTRS)

Gregory, G. L.; Wornom, D. E.; Mathis, J. J., Jr.; Sebacher, D. I.

1980-01-01

Ozone production was determined from aircraft and surface in situ measurements, as well as from an airborne laser absorption spectrometer. Three aircraft and approximately 10 surface stations provided air-quality data. Extensive meteorological, mixing-layer-height, and ozone-precursor data were also measured. Approximately 50 hrs (9 flight days) of data from the aircraft equipped to monitor ozone, nitrogen oxides, dewpoint temperature, and temperature are presented. In addition, each experiment conducted is discussed.

Gridded global surface ozone metrics for atmospheric chemistry model evaluation

NASA Astrophysics Data System (ADS)

Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.; Wmo Gaw, Epa Aqs, Epa Castnet, Capmon, Naps, Airbase, Emep, Eanet Ozone Datasets, All Other Contributors To

2015-07-01

The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent dataset for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total dataset of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regional background locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This dataset is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily eight-hour average (MDA8), SOMO35, AOT40, and metrics related to air quality regulatory thresholds. Gridded datasets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi:10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

Quantifying the Contribution of Thermally Driven Recirculation to a High-Ozone Event Along the Colorado Front Range Using Lidar

NASA Technical Reports Server (NTRS)

Sullivan, John T.; McGee, Thomas J.; Langford, Andrew O.; Alvarez, Raul J., II; Senff, Christoph; Reddy, Patrick J.; Thompson, Anne M.; Twigg, Laurence W.; Sumnicht, Grant K.; Lee, Pius;

Harvesting of Scenedesmus obliquus FSP-3 using dispersed ozone flotation.

PubMed

Cheng, Ya-Ling; Juang, Yu-Chuan; Liao, Guan-Yu; Tsai, Pei-Wen; Ho, Shih-Hsin; Yeh, Kuei-Ling; Chen, Chun-Yen; Chang, Jo-Shu; Liu, Jhy-Chern; Chen, Wen-Ming; Lee, Duu-Jong

2011-01-01

The Scenedesmus obliquus FSP-3, a species with excellent potential for CO(2) capture and lipid production, was harvested using dispersed ozone flotation. While air aeration does not, ozone produces effective solid-liquid separation through flotation. Ozone dose applied for sufficient algal flotation is similar to those used in practical drinking waterworks. The algae removal rate, surface charge, and hydrophobicity of algal cells, and fluorescence characteristics and proteins and polysaccharides contents of algogenic organic matter (AOM) were determined during ozonation. Proteins released from tightly bound AOM are essential to modifying the hydrophobicity of bubble surfaces for easy cell attachment and to forming a top froth layer for collecting floating cells. Humic substances in the suspension scavenge dosed ozone that adversely affects ozone flotation efficiency of algal cells. Copyright © 2010 Elsevier Ltd. All rights reserved.

Ozone precursors and ozone photochemistry over eastern North Pacific during the spring of 1984 based on the NASA GTE/CITE 1 airborne observations

NASA Technical Reports Server (NTRS)

Chameides, W. L.; Davis, D. D.; Gregory, G. L.; Sachse, G.; Torres, A. L.

1989-01-01

Simultaneous high-resolution measurements of O3, NO, CO, dew point temperature, and UV flux obtained during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation (GTE/CITE 1) spring 1984 airborne field exercise over the eastern North Pacific Ocean are analyzed. Mid-tropospheric CO, O3, and NO mixing ratios averaged about 120 parts per billion by volume (ppbv), 50 ppbv, and 10 parts per trillion by volume (pptv), respectively. Statistical analysis of the high-resolution data indicates the existence of two ozone sources, one related to the downward transport of ozone-rich air from the upper troposphere and stratosphere, and the other to the transport of ozone-rich air from the continents. Modeling calculations based on these average levels imply that, from the surface to about 8 km, photochemical reactions probably supplied a net sink of ozone to the region overlying the eastern North Pacific Ocean during the sampling period. However, because the NO levels measured during the flights were frequently at or near the detection limit of the instruments and because the results are very sensitive to the absolute NO levels and their temporal variability, the conclusion must be considered provisional.

Modeling and characterization of field-enhanced corona discharge in ozone-generator diode

NASA Astrophysics Data System (ADS)

Patil, Jagadish G.; Vijayan, T.

2010-02-01

Electric field enhanced corona plasma discharge in ozone generator diode of axial symmetry has been investigated and characterized in theory. The cathode K of diode is made of a large number of sharpened nozzles arranged on various radial planes on the axial mast and pervaded in oxygen gas inside the anode cup A, produces high fields over MV/m and aids in the formation of a corona plume of dense ozone cloud over the cathode surface. An r-z finite difference scheme has been devised and employed to numerically determine the potential and electric field distributions inside the diode. The analyses of cathode emissions revealed a field emission domain conformed to modified Child-Langmuir diode-current. Passage of higher currents (over μA) in shorter A-K gaps d gave rise to cathode heated plasma extending from the corona to Saha regimes depending on local temperature. Plasma densities of order 102-106 m-3 are predicted in these. For larger d however, currents are smaller and heating negligible and a negative corona favoring ozone formation is attained. High ozone yields about 20 per cent of oxygen input is predicted in this domain. The generator so developed will be applied to various important applications such as, purification of ambient air /drinking water, ozone therapy, and so on.

Leveraging Mechanism Simplicity and Strategic Averaging to Identify Signals from Highly Heterogeneous Spatial and Temporal Ozone Data

NASA Astrophysics Data System (ADS)

Brown-Steiner, B.; Selin, N. E.; Prinn, R. G.; Monier, E.; Garcia-Menendez, F.; Tilmes, S.; Emmons, L. K.; Lamarque, J. F.; Cameron-Smith, P. J.

2017-12-01

We summarize two methods to aid in the identification of ozone signals from underlying spatially and temporally heterogeneous data in order to help research communities avoid the sometimes burdensome computational costs of high-resolution high-complexity models. The first method utilizes simplified chemical mechanisms (a Reduced Hydrocarbon Mechanism and a Superfast Mechanism) alongside a more complex mechanism (MOZART-4) within CESM CAM-Chem to extend the number of simulated meteorological years (or add additional members to an ensemble) for a given modeling problem. The Reduced Hydrocarbon mechanism is twice as fast, and the Superfast mechanism is three times faster than the MOZART-4 mechanism. We show that simplified chemical mechanisms are largely capable of simulating surface ozone across the globe as well as the more complex chemical mechanisms, and where they are not capable, a simple standardized anomaly emulation approach can correct for their inadequacies. The second method uses strategic averaging over both temporal and spatial scales to filter out the highly heterogeneous noise that underlies ozone observations and simulations. This method allows for a selection of temporal and spatial averaging scales that match a particular signal strength (between 0.5 and 5 ppbv), and enables the identification of regions where an ozone signal can rise above the ozone noise over a given region and a given period of time. In conjunction, these two methods can be used to "scale down" chemical mechanism complexity and quantitatively determine spatial and temporal scales that could enable research communities to utilize simplified representations of atmospheric chemistry and thereby maximize their productivity and efficiency given computational constraints. While this framework is here applied to ozone data, it could also be applied to a broad range of geospatial data sets (observed or modeled) that have spatial and temporal coverage.

Application of Satellite and Ozonesonde Data to the Study of Nighttime Tropospheric Ozone Impacts and Relationship to Air Quality

NASA Astrophysics Data System (ADS)

Osterman, G. B.; Eldering, A.; Neu, J. L.; Tang, Y.; McQueen, J.; Pinder, R. W.

2011-12-01

To help protect human health and ecosystems, regional-scale atmospheric chemistry models are used to forecast high ozone events and to design emission control strategies to decrease the frequency and severity of ozone events. Despite the impact that nighttime aloft ozone can have on surface ozone, regional-scale atmospheric chemistry models often do not simulate the nighttime ozone concentrations well and nor do they sufficiently capture the ozone transport patterns. Fully characterizing the importance of the nighttime ozone has been hampered by limited measurements of the vertical distribution of ozone and ozone-precursors. The main focus of this work is to begin to utilize remote sensing data sets to characterize the impact of nighttime aloft ozone to air quality events. We will describe our plans to use NASA satellite data sets, transport models and air quality models to study ozone transport, focusing primarily on nighttime ozone and provide initial results. We will use satellite and ozonesonde data to help understand how well the air quality models are simulating ozone in the lower free troposphere and attempt to characterize the impact of nighttime ozone to air quality events. Our specific objectives are: 1) Characterize nighttime aloft ozone using remote sensing data and sondes. 2) Evaluate the ability of the Community Multi-scale Air Quality (CMAQ) model and the National Air Quality Forecast Capability (NAQFC) model to capture the nighttime aloft ozone and its relationship to air quality events. 3) Analyze a set of air quality events and determine the relationship of air quality events to the nighttime aloft ozone. We will achieve our objectives by utilizing the ozone profile data from the NASA Earth Observing System (EOS) Tropospheric Emission Spectrometer (TES) and other sensors, ozonesonde data collected during the Aura mission (IONS), EPA AirNow ground station ozone data, the CMAQ continental-scale air quality model, and the National Air Quality Forecast model.

The seasonality and geographic dependence of ENSO impacts on U.S. surface ozone variability

NASA Astrophysics Data System (ADS)

Xu, Li; Yu, Jin-Yi; Schnell, Jordan L.; Prather, Michael J.

2017-04-01

We examine the impact of El Niño-Southern Oscillation (ENSO) on surface ozone abundance observed over the continental United States (U.S.) during 1993-2013. The monthly ozone decreases (increases) during El Niño (La Niña) years with amplitude up to 1.8 ppb per standard deviation of Niño 3.4 index. The largest ENSO influences occur over two southern U.S. regions during fall when the ENSO develops and over two western U.S. regions during the winter to spring after the ENSO decays. ENSO affects surface ozone via chemical processes during warm seasons in southern regions, where favorable meteorological conditions occur, but via dynamic transport during cold seasons in western regions, where the ENSO-induced circulation variations are large. The geographic dependence and seasonality of the ENSO impacts imply that regulations regarding air quality and its exceedance need to be adjusted for different seasons and U.S. regions to account for the ENSO-driven patterns in surface ozone.

Kinetics of the heterogeneous photo oxidation of the pesticide bupirimate by OH-radicals and ozone under atmospheric conditions.

PubMed

Bouya, H; Errami, M; Chakir, A; Roth, E

2015-09-01

This article is concerned with the study of the photochemical degradation of bupirimate adsorbed on a quartz surface by atmospheric oxidants, namely ozone and OH radicals. OH oxidation experiments were conducted relative to two reference compounds, terbuthylazine and (4-chlorophenyl)(3,4-dimethoxyphenyl) methanone. Meanwhile, ozone oxidation experiments were performed in the absolute mode and were interpreted by both, the Surface Layer Reaction and the Gas Surface Reaction models of heterogeneous reactions. The obtained results show that the rate constants for the reactions between bupirimate and OH radicals and ozone are (cm(3)molecule(-1)s(-1)): (1.06 ± 0.87) × 10(-12) and (5.4 ± 0.3) × 10(-20), respectively. As a consequence, for the experimental conditions used in this study, the lifetime of bupirimate at quartz like surface/atmosphere interfaces is several months against ozone and a tenth of days against OH-radical. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of ozone and ozone/peroxide on trace organic contaminants and NDMA in drinking water and water reuse applications.

PubMed

Pisarenko, Aleksey N; Stanford, Benjamin D; Yan, Dongxu; Gerrity, Daniel; Snyder, Shane A

2012-02-01

An ozone and ozone/peroxide oxidation process was evaluated at pilot scale for trace organic contaminant (TOrC) mitigation and NDMA formation in both drinking water and water reuse applications. A reverse osmosis (RO) pilot was also evaluated as part of the water reuse treatment train. Ozone/peroxide showed lower electrical energy per order of removal (EEO) values for TOrCs in surface water treatment, but the addition of hydrogen peroxide increased EEO values during wastewater treatment. TOrC oxidation was correlated to changes in UV(254) absorbance and fluorescence offering a surrogate model for predicting contaminant removal. A decrease in N-nitrosodimethylamine (NDMA) formation potential (after chloramination) was observed after treatment with ozone and ozone/peroxide. However, during spiking experiments with surface water, ozone/peroxide achieved limited destruction of NDMA, while in wastewaters net direct formation of NDMA of 6-33 ng/L was observed after either ozone or ozone/peroxide treatment. Once formed during ozonation, NDMA passed through the subsequent RO membranes, which highlights the significance of the potential for direct NDMA formation during oxidation in reuse applications. Copyright © 2011 Elsevier Ltd. All rights reserved.

Projection of Changes in Regional Climate and Air Quality in the Great Lakes Basin between 2000 and 2050 for the RCP8.5 Emissions Scenario using the GEM-AQ Model

NASA Astrophysics Data System (ADS)

Lupu, A.; Semeniuk, K.; McConnell, J. C.; Kaminski, J. W.; Toyota, K.; Neary, L.

2012-12-01

The Global Environmental Multiscale Air Quality (GEM-AQ) model was run in global and limited area model (LAM) modes for the baseline year 2000 and one future year, 2050, on three different horizontal grids of increasing resolution from global (1.5°) to North American (LAM, 0.45°) to Ontario regional scale (LAM, 0.15°). For the future simulation we used the high greenhouse emissions scenario RCP8.5. Boundary conditions for the LAM runs were taken from the coarser resolution runs. All simulations had 54 vertical sigma-pressure hybrid levels from the ground to the stratopause (˜50 km), which should give a good representation of ozone injection to the troposphere from the stratosphere. The model uses the interactive land surface scheme ISBA. Sea surface and lake temperatures are prescribed, but ice cover is partially interactive based on prescribed fields. A lake model, FLAKE, was coupled to GEM-AQ in order to capture the impacts of the Great Lakes on the meteorology when the model is run at high resolution. For the Ontario regional simulation the interactive lake model allowed for self-consistent water temperatures and moisture fluxes. The simulation for the year 2000 shows that the model is able to reproduce the observed monthly surface temperatures across the US. The monthly surface ozone is reproduced at the level of detail of most other air quality models with year 2000 weather as opposed to a free run forced by SSTs. Our year 2050 simulation shows that ozone levels during the summer throughout most of Ontario and Canada will increase. Regions south of the latitude of Lake Superior will generally see decreased levels of summer (JJA) ozone, except for around large urban areas such as Toronto, Chicago and Montreal. However, NOx levels will decrease during the summer, reflecting decreased emissions. Ozone levels in the US will generally improve. Other indices rather than simple averages yield a different perspective. If the MDA8 ozone metric and NO2 one-hour 98th percentile are used, then it is found that air quality across Canada and US will generally improve. From the perspective of meteorology, the most significant surface warming that is likely to occur by 2050 is during winter. The winter warming also reflects changes in large scale circulation with baroclinic eddy storm tracks moving north. Winter warming contributes to a surface ozone increase by 2050 in spite of reduced emissions. In addition, we note that in the Ontario region and environs for 2050 there is a significant increase (˜40) in the number of DD5 days, i.e. days where the temperature is above 5°C, a metric useful for the length of the growing season for agriculture. This also means that conditions that impact forests and movement of disease vectors will also change.

Implications of CO Bias for Ozone and Methane Lifetime in a CCM

NASA Technical Reports Server (NTRS)

Strode, Sarah; Duncan, Bryan Neal; Yegorova, Elena; Douglass, Anne

2013-01-01

A low bias in carbon monoxide compared to observations at high latitudes is a common feature of chemistry climate models. CO bias can both indicate and contribute to a bias in modeled OH and methane lifetime. This study examines possible causes of CO bias in the ACCMIP simulation of the GEOSCCM, and considers how attributing the CO bias to uncertainty in CO emissions versus biases in other constituents impacts the relationship between CO bias and methane lifetime. We use a simplified model of CO tagged by source with specified OH to quantify the sensitivity of the CO bias to changes in CO emissions or OH concentration, comparing the modeled CO to surface and MOPITT observations. The simplified model shows that decreasing OH in the northern hemisphere removes most of the global mean and inter-hemispheric bias in surface CO. We then use results from this analysis to explore how adjusting CO sources in the CCM impacts the concentrations of ozone, OH and methane. The CCM simulation also exhibits biases in ozone and water vapor compared to observations. We use a parameterized CO-OH-CH4 model that takes ozone and water vapor as inputs to the parameterization to examine whether correcting water and ozone biases can alter OH enough to remove the CO bias. Through this analysis, we aim to better quantify the relationship between CO bias and model biases in ozone concentrations and methane lifetime.

Is the ozone climate penalty robust in Europe?

NASA Astrophysics Data System (ADS)

Colette, Augustin; Andersson, Camilla; Baklanov, Alexander; Bessagnet, Bertrand; Brandt, Jørgen; Christensen, Jesper H.; Doherty, Ruth; Engardt, Magnuz; Geels, Camilla; Giannakopoulos, Christos; Hedegaard, Gitte B.; Katragkou, Eleni; Langner, Joakim; Lei, Hang; Manders, Astrid; Melas, Dimitris; Meleux, Frédérik; Rouïl, Laurence; Sofiev, Mikhail; Soares, Joana; Stevenson, David S.; Tombrou-Tzella, Maria; Varotsos, Konstantinos V.; Young, Paul

2015-08-01

Ozone air pollution is identified as one of the main threats bearing upon human health and ecosystems, with 25 000 deaths in 2005 attributed to surface ozone in Europe (IIASA 2013 TSAP Report #10). In addition, there is a concern that climate change could negate ozone pollution mitigation strategies, making them insufficient over the long run and jeopardising chances to meet the long term objective set by the European Union Directive of 2008 (Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008) (60 ppbv, daily maximum). This effect has been termed the ozone climate penalty. One way of assessing this climate penalty is by driving chemistry-transport models with future climate projections while holding the ozone precursor emissions constant (although the climate penalty may also be influenced by changes in emission of precursors). Here we present an analysis of the robustness of the climate penalty in Europe across time periods and scenarios by analysing the databases underlying 11 articles published on the topic since 2007, i.e. a total of 25 model projections. This substantial body of literature has never been explored to assess the uncertainty and robustness of the climate ozone penalty because of the use of different scenarios, time periods and ozone metrics. Despite the variability of model design and setup in this database of 25 model projection, the present meta-analysis demonstrates the significance and robustness of the impact of climate change on European surface ozone with a latitudinal gradient from a penalty bearing upon large parts of continental Europe and a benefit over the North Atlantic region of the domain. Future climate scenarios present a penalty for summertime (JJA) surface ozone by the end of the century (2071-2100) of at most 5 ppbv. Over European land surfaces, the 95% confidence interval of JJA ozone change is [0.44; 0.64] and [0.99; 1.50] ppbv for the 2041-2070 and 2071-2100 time windows, respectively.

Climate Throughout Geologic Time Was Cooled by Sequences of Explosive Volcanic Eruptions Forming Aerosols That Reflect and Scatter Ultraviolet Solar Radiation and Warmed by Relatively Continuous Extrusion of Basaltic Lava that Depletes Ozone, Allowing More Solar Ultraviolet Radiation to Reach Earth

NASA Astrophysics Data System (ADS)

Ward, P. L.

2015-12-01

Active volcanoes of all sizes and eruptive styles, emit chlorine and bromine gases observed to deplete ozone. Effusive, basaltic volcanic eruptions, typical in Hawaii and Iceland, extrude large lava flows, depleting ozone and causing global warming. Major explosive volcanoes also deplete ozone with the same emissions, causing winter warming, but in addition eject megatons of water and sulfur dioxide into the lower stratosphere where they form sulfuric-acid aerosols whose particles grow large enough to reflect and scatter ultraviolet sunlight, causing net global cooling for a few years. The relative amounts of explosive and effusive volcanism are determined by the configuration of tectonic plates moving around Earth's surface. Detailed studies of climate change throughout geologic history, and since 1965, are not well explained by greenhouse-gas theory, but are explained quite clearly at OzoneDepletionTheory.info. Ozone concentrations vary substantially by the minute and show close relationships to weather system highs and lows (as pointed out by Dobson in the 1920s), to the height of the tropopause, and to the strength and location of polar vortices and jet streams. Integrating the effects of volcanism on ozone concentrations and the effects of ozone concentrations on synoptic weather patterns should improve weather forecasting. For example, the volcano Bárðarbunga, in central Iceland, extruded 85 km2 of basaltic lava between August 29, 2014, and February 28, 2015, having a profound effect on weather. Most surprising, more than a week before the March 4 eruption of Eyjafjallajökull in 2010, substantial amounts of ozone were released in the vicinity of the volcano precisely when surface deformation showed that magma first began moving up from sills below 4 km depth. Ozone similarly appears to have been emitted 3.5 months before the Pinatubo eruption in 1991. Readily available daily maps of ozone concentrations may allow early warning of an imminent volcanic eruption.

Broad features of surface ozone variations over Indian region

NASA Technical Reports Server (NTRS)

Shende, R. R.; Jayaraman, K.; Sreedharan, C. R.; Tiwari, V. S.

1994-01-01

Surface ozone concentration at three Indian stations - New Delhi (28.6 deg N), Pune (18.5 deg N) and Thiruvananthapuram (formerly Trivandrum (8.3 deg N) - has been measured since 1973 with the help of an electrochemical continuous ozone recorder. These stations show diurnal, seasonal and annual cycles in surface ozone. Daily changes show that the minimum value occurs at sunrise and maximum in the afternoon. As regards seasonal variations, Thiruvananthapuram and Pune have a minimum value during monsoon season (June to August) while at New Delhi the minimum value occurs in January. However, New Delhi also records low ozone amount during monsoon season identical to the amounts show at Thiruvananthapuram and Pune. The annual cycles at these stations have been compared with similar measurements in the northern and southern hemispheres. The Indian measurements agree well with the annual cycles at these stations. Further, the analysis of the Indian data indicates that the major contribution in surface ozone comes from the natural sources like stratospheric-tropospheric exchange, turbulence, and mixing in the boundary layer; however, a small contribution from anthropogenic sources cannot be ruled out at Pune and probably at New Delhi, especially in winter and summer seasons.

Quantifying TOLNet Ozone Lidar Accuracy During the 2014 DISCOVER-AQ and FRAPPE Campaigns

NASA Technical Reports Server (NTRS)

Wang, Lihua; Newchurch, Michael J.; Alvarez, Raul J., II; Berkoff, Timothy A.; Brown, Steven S.; Carrion, William; De Young, Russell J.; Johnson, Bryan J.; Ganoe, Rene; Gronoff, Guillaume;

Quantifying TOLNet ozone lidar accuracy during the 2014 DISCOVER-AQ and FRAPPÉ campaigns

NASA Astrophysics Data System (ADS)

Wang, Lihua; Newchurch, Michael J.; Alvarez, Raul J., II; Berkoff, Timothy A.; Brown, Steven S.; Carrion, William; De Young, Russell J.; Johnson, Bryan J.; Ganoe, Rene; Gronoff, Guillaume; Kirgis, Guillaume; Kuang, Shi; Langford, Andrew O.; Leblanc, Thierry; McDuffie, Erin E.; McGee, Thomas J.; Pliutau, Denis; Senff, Christoph J.; Sullivan, John T.; Sumnicht, Grant; Twigg, Laurence W.; Weinheimer, Andrew J.

2017-10-01

The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure high-resolution atmospheric profiles of ozone. The accurate characterization of these lidars is necessary to determine the uniformity of the network calibration. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission and the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) to measure ozone variations from the boundary layer to the top of the troposphere. This study presents the analysis of the intercomparison between the TROPOZ, TOPAZ, and LMOL lidars, along with comparisons between the lidars and other in situ ozone instruments including ozonesondes and a P-3B airborne chemiluminescence sensor. The TOLNet lidars measured vertical ozone structures with an accuracy generally better than ±15 % within the troposphere. Larger differences occur at some individual altitudes in both the near-field and far-field range of the lidar systems, largely as expected. In terms of column average, the TOLNet lidars measured ozone with an accuracy better than ±5 % for both the intercomparison between the lidars and between the lidars and other instruments. These results indicate that these three TOLNet lidars are suitable for use in air quality, satellite validation, and ozone modeling efforts.

Air Quality Science and Regulatory Efforts Require Geostationary Satellite Measurements

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.; Allen, D. J.; Stehr, J. W.

2006-01-01

Air quality scientists and regulatory agencies would benefit from the high spatial and temporal resolution trace gas and aerosol data that could be provided by instruments on a geostationary platform. More detailed time-resolved data from a geostationary platform could be used in tracking regional transport and in evaluating mesoscale air quality model performance in terms of photochemical evolution throughout the day. The diurnal cycle of photochemical pollutants is currently missing from the data provided by the current generation of atmospheric chemistry satellites which provide only one measurement per day. Often peak surface ozone mixing ratios are reached much earlier in the day during major regional pollution episodes than during local episodes due to downward mixing of ozone that had been transported above the boundary layer overnight. The regional air quality models often do not simulate this downward mixing well enough and underestimate surface ozone in regional episodes. Having high time-resolution geostationary data will make it possible to determine the magnitude of this lower-and mid-tropospheric transport that contributes to peak eight-hour average ozone and 24-hour average PM2.5 concentrations. We will show ozone and PM(sub 2.5) episodes from the CMAQ model and suggest ways in which geostationary satellite data would improve air quality forecasting. Current regulatory modeling is typically being performed at 12 km horizontal resolution. State and regional air quality regulators in regions with complex topography and/or land-sea breezes are anxious to move to 4-km or finer resolution simulations. Geostationary data at these or finer resolutions will be useful in evaluating such models.

A comparison of different activated carbon performances on catalytic ozonation of a model azo reactive dye.

PubMed

Gül, S; Eren, O; Kır, S; Onal, Y

2012-01-01

The objective of this study is to compare the performances of catalytic ozonation processes of two activated carbons prepared from olive stone (ACOS) and apricot stone (ACAS) with commercial ones (granular activated carbon-GAC and powder activated carbon-PAC) in degradation of reactive azo dye (Reactive Red 195). The optimum conditions (solution pH and amount of catalyst) were investigated by using absorbencies at 532, 220 and 280 nm wavelengths. Pore properties of the activated carbon (AC) such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N(2) adsorption. The highest BET surface area carbon (1,275 m(2)/g) was obtained from ACOS with a particle size of 2.29 nm. After 2 min of catalytic ozonation, decolorization performances of ACOS and ACAS (90.4 and 91.3%, respectively) were better than that of GAC and PAC (84.6 and 81.2%, respectively). Experimental results showed that production of porous ACs with high surface area from olive and apricot stones is feasible in Turkey.

Ozone production process in pulsed positive dielectric barrier discharge

NASA Astrophysics Data System (ADS)

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 kinetics in low-pressure discharges: vibrationally excited ozone and molecule formation on surfaces

NASA Astrophysics Data System (ADS)

Marinov, Daniil; Guerra, Vasco; Guaitella, Olivier; Booth, Jean-Paul; Rousseau, Antoine

2013-10-01

A combined experimental and modeling investigation of the ozone kinetics in the afterglow of pulsed direct current discharges in oxygen is carried out. The discharge is generated in a cylindrical silica tube of radius 1 cm, with short pulse durations between 0.5 and 2 ms, pressures in the range 1-5 Torr and discharge currents ˜40-120 mA. Time-resolved absolute concentrations of ground-state atoms and ozone molecules were measured simultaneously in situ, by two-photon absorption laser-induced fluorescence and ultraviolet absorption, respectively. The experiments were complemented by a self-consistent model developed to interpret the results and, in particular, to evaluate the roles of vibrationally excited ozone and of ozone formation on surfaces. It is found that vibrationally excited ozone, O_3^{*} , plays an important role in the ozone kinetics, leading to a decrease in the ozone concentration and an increase in its formation time. In turn, the kinetics of O_3^{*} is strongly coupled with those of atomic oxygen and O2(a 1Δg) metastables. Ozone formation at the wall does not contribute significantly to the total ozone production under the present conditions. Upper limits for the effective heterogeneous recombination probability of O atoms into ozone are established.

Fungicide residue remediation on table grapes using ozone fumigation

USDA-ARS?s Scientific Manuscript database

Ozone fumigation was explored as a means for degrading contemporary organic fungicides related to table grape production. Separate fumigations were conducted in a flow-through chamber on fungicides sorbed to model abiotic glass surfaces or to table grapes. Gaseous ozone at constant ozone concentrati...

Lusaka, Zambia, during SAFARI-2000: Convergence of local and imported ozone pollution

NASA Astrophysics Data System (ADS)

Thompson, Anne M.; Witte, Jacquelyn C.; Freiman, M. Tal; Phahlane, N. Agnes; Coetzee, Gert J. R.

2002-10-01

In August and September, throughout south central Africa, seasonal clearing of dry vegetation and other fire-related activities lead to intense smoke haze and ozone formation. The first ozone soundings in the heart of the southern African burning region were taken at Lusaka, Zambia (15.5S, 28E) in early September 2000. Maximum surface ozone was over 90 ppbv and column tropospheric ozone exceeded 50 DU. These values are higher than concurrent measurements over Nairobi (1S, 38E) and Irene (25S, 28E, near Pretoria). At least 30% of Lusaka surface ozone appears to be from local sources. A layer at 800-500 hPa has ozone >120 ppbv and originates from trans-boundary recirculation. Starting out over Zambia, Angola, and Namibia, ozone-rich air travels east to the Indian Ocean, before heading back toward Mozambique, Zimbabwe and Zambia. Thus, Lusaka collects local and imported pollution, consistent with its location within the southern African gyre.

Diverse policy implications for future ozone and surface UV in a changing climate

NASA Astrophysics Data System (ADS)

Butler, A. H.; Daniel, J. S.; Portmann, R. W.; Ravishankara, A. R.; Young, P. J.; Fahey, D. W.; Rosenlof, K. H.

2016-06-01

Due to the success of the Montreal Protocol in limiting emissions of ozone-depleting substances, concentrations of atmospheric carbon dioxide, nitrous oxide, and methane will control the evolution of total column and stratospheric ozone by the latter half of the 21st century. As the world proceeds down the path of reducing climate forcing set forth by the 2015 Conference of the Parties to the United Nations Framework Convention on Climate Change (COP 21), a broad range of ozone changes are possible depending on future policies enacted. While decreases in tropical stratospheric ozone will likely persist regardless of the future emissions scenario, extratropical ozone could either remain weakly depleted or even increase well above historical levels, with diverse implication for ultraviolet (UV) radiation. The ozone layer’s dependence on future emissions of these gases creates a complex policy decision space for protecting humans and ecosystems, which includes unexpected options such as accepting nitrous oxide emissions in order to maintain historical column ozone and surface UV levels.

Damages of surface ozone: evidence from agricultural sector in China

NASA Astrophysics Data System (ADS)

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.

The Response of Tropospheric Ozone to ENSO in Observations and a Chemistry-Climate Simulation

NASA Technical Reports Server (NTRS)

Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Rodriguez, J. M.; Nielsen, J. E.

2012-01-01

The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere. Recent results have revealed an ENSO induced wave-l anomaly in observed tropical tropospheric column ozone. This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years. An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region. We will show targeted comparisons with observations from NASA's Aura satellite Microwave Limb Sounder (MLS), and the Tropospheric Emissions Spectrometer (TES) to provide insight into the vertical structure of ozone changes. The tropospheric ozone response to ENSO could be a useful chemistry-climate model evaluation tool and should be considered in future modeling assessments.

The Impact of Chemical Mechanism Design on Simulated Surface Ozone in CAM-Chem

NASA Astrophysics Data System (ADS)

Schwantes, R.; Emmons, L. K.; Orlando, J. J.; Tyndall, G. S.

2017-12-01

Many regions in the United States have poor air quality because of high levels of ozone. Global and regional chemical transport models are important tools for recommending regulatory policy directions to efficiently reduce ozone. Ozone is intrinsically hard to simulate in global and regional models because the amount of ozone present is controlled by large non-linear sources and sinks. Recent field campaigns have concluded that monoterpene chemistry is particularly important for the NOx budget and thereby O3 formation. However, many regional and global models have none or heavily reduced monoterpene chemical schemes. In this study, the chemical mechanism for isoprene and monoterpene oxidation will be significantly improved and updated in CAM-Chem (Community Atmosphere Model with chemistry), which is a component of the Community Earth System Model (CESM). In particular, the updates will focus on accurately portraying organic nitrate formation and fate. The impact of various uncertainties (e.g., nitrate yields, later generation chemistry, loss of organic nitrates to aerosols via hydrolysis, etc.) on ozone formation will be tested. This study will both improve the chemistry in CAM-Chem and reveal lingering uncertainties that have the largest impact on ozone formation.

Design of a Vehicle-Based Intervention System to Prevent Ozone Loss

NASA Technical Reports Server (NTRS)

Mason, William H.; Kirchbaum, Nathan; Kay, Jacob; Benoliel, Alexander M.; Lynn, Sean R.; Bunker, Deborah; Hesbach, Thomas D., Jr.; Howerton, Everett B.; Hreinsson, Gudbjoern; Mistr, E. Kirk

1993-01-01

Reduced quantities of ozone in the atmosphere allow greater levels of ultraviolet (UV) radiation to reach the earth's surface. The 1992/1993 project goals for the Virginia Tech Senior Design Team were to 1) understand the processes which contribute to stratospheric ozone loss, 2) examine ways to prevent ozone loss, and 3) define the requirements for an implementation vehicle to carry out the prevention scheme. A scheme proposed by R.J. Cicerone, el al late in 1991 was selected because of its supporting research and economic feasibility. This scheme uses hydrocarbon injected into the Antarctic ozone hole to form stable compounds with free chlorine, thus reducing ozone depletion. A study of the hydrocarbon injection requirements determined that 130 aircraft traveling Mach 2.4 at a maximum altitude of 66,000 ft. would provide the most economic approach to preventing ozone loss. Each aircraft would require an 8,000 nm. range and be able to carry 35,000 lbs. of propane. The propane would be stored in a three-tank high pressure system. Modularity and multi-role functionality were selected to be key design features. Missions originate from airports located in South America and Australia.

Relationship between the structure of Fe-MCM-48 and its activity in catalytic ozonation for diclofenac mineralization.

PubMed

Li, Xukai; Chen, Weirui; Tang, Yiming; Li, Laisheng

2018-05-12

Fe-MCM-48 catalyst with a three-dimensional cubic pore structure was directly synthesized via a hydrothermal method, and the mineralization efficiency of diclofenac (DCF) in the catalytic ozonation process (Fe-MCM-48/O 3 ) was assessed. X-ray diffraction (XRD), N 2 adsorption desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) characterizations revealed that Fe existed in the framework of MCM-48, and Fe-MCM-48 possessed a large surface area and a highly ordered cubic mesoporous structure, which could accelerate reactants and products diffusion. Regarding mineralization efficiency, the addition of Fe-MCM-48 significantly improved total organic carbon (TOC) removal, and approximately 49.9% TOC were removed through the Fe-MCM-48/O 3 process at 60 min, which was 2.0 times higher than that in single ozonation. Due to this catalyst's superior structure, Fe-MCM-48 showed the better catalytic activity compared with Fe-MCM-41 and Fe loaded MCM-48 (Fe/MCM-48, Fe existed on the surface of MCM-48). DCF removal in the Fe-MCM-48/O 3 process was primarily based on ozone direct oxidation. The improvement of mineralization efficiency was attributed to the function of generated hydroxyl radicals (•OH), which indicated that the presence of Fe-MCM-48 accelerated ozone decomposition. Moreover, the negatively charged surface of Fe-MCM-48 and the proper pH value of the DCF solution played an essential role in OH generation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase.

PubMed

Bohli, Thouraya; Ouederni, Abdelmottaleb

2016-08-01

Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

On Springtime Ozone Enhancements in the Lower Troposphere Over Beijing

NASA Astrophysics Data System (ADS)

Huang, J.; Liu, H.; Chan, C.; Crawford, J. H.; Considine, D. B.; Zhang, Y.; Zheng, X.; Oltmans, S. J.; Liu, S. C.; Thouret, V.

2012-12-01

Tropospheric ozone is an important greenhouse gas, the primary source of hydroxyl radical (OH) that controls the tropospheric oxidizing capacity, and a major air pollutant near the surface. Previous studies showed that ozone concentrations in the lower troposphere (LT) over Beijing have increased over the past two decades as a result of rapid industrialization in China. As part of an ozonesonde sounding campaign, called Transport of Air Pollutants and Tropospheric Ozone over China (TAPTO-China), intensive measurements of ozone vertical profiles (16 in total) were conducted in Beijing during April 11 - May 15, 2005. Thirteen vertical profiles were also sampled by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program during April 3 - May 29, 2005. High ozone concentrations (up to 94.7 ppbv) were frequently observed in the LT (~1.5-2km) during this period. We evaluate here the capability of a 3-D chemical transport model (GEOS-Chem at 2°x2.5° resolution) to reproduce these ozone enhancements, and use the model to examine transport pathways for ozone pollution and quantify their sources. The model captures the occurrences but significantly underestimates the magnitude of ozone enhancements. By tagging ozone produced in different source regions and conducting sensitivity simulations with the model, we show that Asian troposphere and Asian anthropogenic pollution made the major contributions to those ozone enhancements. Contributions from European and North American troposphere and anthropogenic pollution reduced during these events, compared to those days without ozone enhancements. We find that most of the ozone enhancements observed in the LT occurred under southerly wind and warmer conditions. Their occurrence frequency appears to be related to the onset of Asian summer monsoon. The influence of regional transport from different source regions in East Asia will also be discussed.

Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

PubMed

Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

2015-04-01

There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters.

Atomic layer deposition of dielectrics on graphene using reversibly physisorbed ozone.

PubMed

Jandhyala, Srikar; Mordi, Greg; Lee, Bongki; Lee, Geunsik; Floresca, Carlo; Cha, Pil-Ryung; Ahn, Jinho; Wallace, Robert M; Chabal, Yves J; Kim, Moon J; Colombo, Luigi; Cho, Kyeongjae; Kim, Jiyoung

2012-03-27

Integration of graphene field-effect transistors (GFETs) requires the ability to grow or deposit high-quality, ultrathin dielectric insulators on graphene to modulate the channel potential. Here, we study a novel and facile approach based on atomic layer deposition through ozone functionalization to deposit high-κ dielectrics (such as Al(2)O(3)) without breaking vacuum. The underlying mechanisms of functionalization have been studied theoretically using ab initio calculations and experimentally using in situ monitoring of transport properties. It is found that ozone molecules are physisorbed on the surface of graphene, which act as nucleation sites for dielectric deposition. The physisorbed ozone molecules eventually react with the metal precursor, trimethylaluminum to form Al(2)O(3). Additionally, we successfully demonstrate the performance of dual-gated GFETs with Al(2)O(3) of sub-5 nm physical thickness as a gate dielectric. Back-gated GFETs with mobilities of ~19,000 cm(2)/(V·s) are also achieved after Al(2)O(3) deposition. These results indicate that ozone functionalization is a promising pathway to achieve scaled gate dielectrics on graphene without leaving a residual nucleation layer. © 2012 American Chemical Society

Climate change impacts on projections of excess mortality at ...

EPA Pesticide Factsheets

We project the change in ozone-related mortality burden attributable to changes in climate between a historical (1995-2005) and near-future (2025-2035) time period while incorporating a non-linear and synergistic effect of ozone and temperature on mortality. We simulate air quality from climate projections varying only biogenic emissions and holding anthropogenic emissions constant, thus attributing changes in ozone only to changes in climate and independent of changes in air pollutant emissions. We estimate non-linear, spatially varying, ozone-temperature risk surfaces for 94 US urban areas using observeddata. Using the risk surfaces and climate projections we estimate daily mortality attributable to ozone exceeding 40 p.p.b. (moderate level) and 75 p.p.b. (US ozone NAAQS) for each time period. The average increases in city-specific median April-October ozone and temperature between time periods are 1.02 p.p.b. and 1.94 °F; however, the results variedby region . Increases in ozone because of climate change result in an increase in ozone mortality burden. Mortality attributed to ozone exceeding 40 p.p.b. increases by 7.7% (1 .6-14.2%). Mortality attributed to ozone exceeding 75 p.p.b. increases by 14.2% (1.628.9%). The absolute increase in excess ozone mortality is larger for changes in moderate ozone levels, reflecting the larger number of days with moderate ozone levels. In this study we evaluate changes in ozone related mortality due to changes in biogenic f

Recent Advances in Ozone Data Assimilation at the GMAO - Towards a New Reanalysis

NASA Technical Reports Server (NTRS)

Krzysztof, Wargan; Pawson, S.; Nielsen, J. E.; Witte, J.; Douglass, A.; Strahan, S.; Joiner, J.; Bhartia, P. K.; Livesey, N.; Read, W.;

Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

NASA Technical Reports Server (NTRS)

Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

2016-01-01

Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

Effects and mechanism on Kapton film under ozone exposure in a ground near space simulator

NASA Astrophysics Data System (ADS)

Wei, Qiang; Yang, Guimin; Liu, Gang; Jiang, Haifu; Zhang, Tingting

2018-05-01

The effect on aircraft materials in the near space environment is a key part of air-and-space integration research. Ozone and aerodynamic fluids are important organizational factors in the near space environment and both have significant influences on the performance of aircraft materials. In the present paper a simulated ozone environment was used to test polyimide material that was rotated at the approximate velocity of 150-250 m/s to form an aerodynamic fluid field. The goal was to evaluate the performance evolution of materials under a comprehensive environment of ozone molecular corrosion and aerodynamic fluids. The research results show that corrosion and sputtering by ozone molecules results in Kapton films exhibiting a rugged "carpet-like" morphology exhibits an increase in surface roughness. The morphology after ozone exposure led to higher surface roughness and an increase in surface optical diffuse reflection, which is expressed by the lower optical transmittance and the gradual transition from light orange to brown. The mass loss test, XPS, and FTIR analysis show that the molecular chains on the surface of the Kapton film are destroyed resulting in Csbnd C bond breaking to form small volatile molecules such as CO2 or CO, which are responsible for a linear increase in mass loss per unit area. The Csbnd N and Csbnd O structures exhibit weakening tendency under ozone exposure. The present paper explores the evaluation method for Kapton's adaptability under the ozone exposure test in the near space environment, and elucidates the corrosion mechanism and damage mode of the polyimide material under the combined action of ozone corrosion and the aerodynamic fluid. This work provides a methodology for studying materials in the near-space environment.

Tobacco smoke aging in the presence of ozone: A room-sized chamber study

NASA Astrophysics Data System (ADS)

Petrick, Lauren M.; Sleiman, Mohamad; Dubowski, Yael; Gundel, Lara A.; Destaillats, Hugo

2011-09-01

Exposure to tobacco pollutants that linger indoors after smoking has taken place ( thirdhand smoke, THS) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were characterized during aging. After smoldering 10 cigarettes in a 24-m 3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of ˜10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h -1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heterogeneous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.

Airborne DIAL Ozone and Aerosol Trends Observed at High Latitudes Over North America from February to May 2000

NASA Technical Reports Server (NTRS)

Hair, Jonathan W.; Browell, Edward V.; Butler, Carolyn F.; Grant, William B.; DeYoung, Russell J.; Fenn, Marta A.; Brackett, Vince G.; Clayton, Marian B.; Brasseur, Lorraine

2002-01-01

Ozone (O3) and aerosol scattering ratio profiles were obtained from airborne lidar measurements on thirty-eight aircraft flights over seven aircraft deployments covering the latitudes of 40 deg.-85 deg.N between 4 February and 23 May 2000 as part of the TOPSE (Tropospheric Ozone Production about the Spring Equinox) field experiment. The remote and in situ O3 measurements were used together to produce a vertically-continuous O3 profile from near the surface to above the tropopause. Ozone, aerosol, and potential vorticity (PV) distributions were used together to identify the presence of pollution plumes and stratospheric intrusions. The number of observed pollution plumes was found to increase into the spring along with a significant increase in aerosol loading. Ozone was found to increase in the middle free troposphere (4-6 km) at high latitudes (60 deg.-85 deg. N) by an average of 4.3 ppbv/mo from about 55 ppbv in early February to over 72 ppbv in mid-May. The average aerosol scattering ratios in the same region increased at an average rate of 0.37/mo from about 0.35 to over 1.7. Ozone and aerosol scattering were highly correlated over entire field experiment. Based on the above results and the observed aircraft in-situ measurements, it was estimated that stratospherically-derived O3 accounted for less than 20% of the observed increase in mid tropospheric O3 at high latitudes. The primary cause of the observed O3 increase was found to be the photochemical production of O3 in pollution plumes.

High density gold nanoparticles immobilized on surface via plasma deposited APTES film for decomposing organic compounds in microchannels

NASA Astrophysics Data System (ADS)

Rao, Xi; Guyon, Cédric; Ognier, Stephanie; Da Silva, Bradley; Chu, Chenglin; Tatoulian, Michaël; Hassan, Ali Abou

2018-05-01

Immobilization of colloidal particles (e.g. gold nanoparticles (AuNps)) on the inner surface of micro-/nano- channels has received a great interest for catalysis. A novel catalytic ozonation setup using a gold-immobilized microchannel reactor was developed in this work. To anchor AuNps, (3-aminopropyl) triethoxysilane (APTES) with functional amine groups was deposited using plasma enhanced chemical vapor deposition (PECVD) process. The results clearly evidenced that PECVD processing exhibited relatively high efficiency for grafting amine groups and further immobilizing AuNPs. The catalytic activity of gold immobilized microchannel was evaluated by pyruvic acid ozonation. The decomposition rate calculated from High Performance Liquid Chromatography (HPLC) indicated a much better catalytic performance of gold in microchannel than that in batch. The results confirmed immobilizing gold nanoparticles on plasma deposited APTES for preparing catalytic microreactors is promising for the wastewater treatment in the future.

Accurate ab initio dipole moment surfaces of ozone: First principle intensity predictions for rotationally resolved spectra in a large range of overtone and combination bands.

PubMed

Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A

2017-02-14

Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of 16 O 3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works. For the first time, a very good agreement of first principle calculations with the experiment was obtained for the line-by-line intensities in rotationally resolved ozone spectra in a large far- and mid-infrared range. This includes high overtone and combination bands up to ΔV = 6. A particular challenge was a correct description of the B-type bands (even ΔV 3 values) that represented major difficulties for the previous ab initio investigations and for the empirical spectroscopic models. The major patterns of various B-type bands were correctly described without empirically adjusted dipole moment parameters. For the 10 μm range, which is of key importance for the atmospheric ozone retrievals, our ab initio intensity results are within the experimental error margins. The theoretical values for the strongest lines of the ν 3 band lie in general between two successive versions of HITRAN (HIgh-resolution molecular TRANsmission) empirical database that corresponded to most extended available sets of observations. The overall qualitative agreement in a large wavenumber range for rotationally resolved cold and hot ozone bands up to about 6000 cm -1 is achieved here for the first time. These calculations reveal that several weak bands are yet missing from available spectroscopic databases.

Decreasing Lower Tropospheric Ozone over the North China Plain Observed by IASI: Looking for Explanations

NASA Astrophysics Data System (ADS)

Dufour, G.; Eremenko, M.; Lachâtre, M.; Hauglustaine, D.; Fortems-Cheiney, A.; Cuesta, J.; Zhang, Y.; Cai, Z.; Liu, Y.; Xu, X.; Lin, W.; Cooper, O. R.

2017-12-01

China, and especially the North China Plain (NCP), is a highly polluted region. Emission reductions have been applied since about 10 years, starting with SO2 emissions in 2006 and with NOx emissions in 2010. Recent satellite observations series show a decrease of NO2 tropospheric columns since 2013 and attributed to the NOx emissions reduction. The question of the impact of such reduction on ozone is then arising. In this study, we use the capabilities of the IASI satellite instrument to retrieve 2 semi-independent columns of ozone in the lower (surface-6km asl) and the upper (6-12km) troposphere - the lower tropospheric (LT) column having a sensitivity maximum at 3-4 km - and we evaluate the variability and trend of LT ozone over the NCP for 2008-2016. Deseasonalized monthly timeseries show two distinct periods: a first period (2008-2012) with no significant trend (slope of the linear fit < -0.1 %/yr) and a second period (2013-2016) with a highly significant negative trend of -1.2 %/yr, leading to an overall trend of -0.77 %/yr for 2008-2016. A first temptation is to attribute this decrease to the NOx emissions changes. However, negative trends have not been reported from background surface measurements in this Chinese region. Furthermore recent work made within the framework of the TOAR initiative reveals discrepancies in the sign of the trends of tropospheric column ozone derived from infrared and ultraviolet satellite instruments. As yet there is no conclusive explanation for the discrepancy. We then investigate the IASI retrieval stability and robustness in terms of vertical sensitivity, interferences with large aerosol loading, and comparing with surface and ozonesonde measurements and the IASI instrument aboard the Metop-B satellite. One issue arises concerning the temporal sampling of IASI that may induce significant change in the trend derived from surface stations. We also explore the possible variables, other than emissions, which could explain the observed negative trends using both a statistical regression model and simulations from global and regional chemistry transport models.

Processes Affecting Tropospheric Ozone Inferred from Ozonesonde and Other Tracer Data from the R/V R H Brown Atlantic Cruise (37N-34S) in January-February 1999

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Doddridge, B. G.; Luke, W. T.; Johnson, J. E.; Witte, J. C.; Reynolds, R. M.; Johnson, B.; Oltmans, S. J.

1999-01-01

During the Aerosols-99 trans-Atlantic cruise from Norfolk, VA, to Cape Town, South Africa, 22 ozonesondes were launched from the NOAA R/V R H Brown between 17 Jan and 6 Feb 1999, with all sondes but one reaching 30 km. A composite of ozone profiles along the transect shows high free tropospheric ozone (up to 100 ppbv at 9 km) between 5N and 20S, a coherent feature straddling either side of the ITCZ. Latitudinal variations of tropospheric ozone are interpreted using correlative measurements of surface ozone, CO, water vapor, and aerosol optical thickness (column absorbance) measured from the ship. Elevated ozone in the lower troposphere results from photochemical reactions of precursors emitted by biomass burning north of the ITCZ. However, the greatest ozone mixing ratios are in the mid-troposphere south of the ITCZ, which gives evidence of interhemispheric transport. Column-integrated tropospheric ozone, 35 DU from 0-16 km, agrees with that derived from the TOMS satellite by the modified-residual method [Thompson and Hudson, 1999]. NCEP wind fields, ship-launched radiosondes and back trajectories are consistent with a picture of recirculating air parcels centered in the tropical Atlantic region which is identified with the maximum wave-one amplitude in total ozone seen in sondes and by satellite.

Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: inference from synoptic-scale patterns

NASA Astrophysics Data System (ADS)

Toyota, K.; McConnell, J. C.; Lupu, A.; Neary, L.; McLinden, C. A.; Richter, A.; Kwok, R.; Semeniuk, K.; Kaminski, J. W.; Gong, S.-L.; Jarosz, J.; Chipperfield, M. P.; Sioris, C. E.

2011-04-01

Episodes of high bromine levels and surface ozone depletion in the springtime Arctic are simulated by an online air-quality model, GEM-AQ, with gas-phase and heterogeneous reactions of inorganic bromine species and a simple scheme of air-snowpack chemical interactions implemented for this study. Snowpack on sea ice is assumed to be the only source of bromine to the atmosphere and to be capable of converting relatively stable bromine species to photolabile Br2 via air-snowpack interactions. A set of sensitivity model runs are performed for April 2001 at a horizontal resolution of approximately 100 km×100 km in the Arctic, to provide insights into the effects of temperature and the age (first-year, FY, versus multi-year, MY) of sea ice on the release of reactive bromine to the atmosphere. The model simulations capture much of the temporal variations in surface ozone mixing ratios as observed at stations in the high Arctic and the synoptic-scale evolution of areas with enhanced BrO column amount ("BrO clouds") as estimated from satellite observations. The simulated "BrO clouds" are in modestly better agreement with the satellite measurements when the FY sea ice is assumed to be more efficient at releasing reactive bromine to the atmosphere than on the MY sea ice. Surface ozone data from coastal stations used in this study are not sufficient to evaluate unambiguously the difference between the FY sea ice and the MY sea ice as a source of bromine. The results strongly suggest that reactive bromine is released ubiquitously from the snow on the sea ice during the Arctic spring while the timing and location of the bromine release are largely controlled by meteorological factors. It appears that a rapid advection and an enhanced turbulent diffusion associated with strong boundary-layer winds drive transport and dispersion of ozone to the near-surface air over the sea ice, increasing the oxidation rate of bromide (Br-) in the surface snow. Also, if indeed the surface snowpack does supply most of the reactive bromine in the Arctic boundary layer, it appears to be capable of releasing reactive bromine at temperatures as high as -10 °C, particularly on the sea ice in the central and eastern Arctic Ocean. Dynamically-induced BrO column variability in the lowermost stratosphere appears to interfere with the use of satellite BrO column measurements for interpreting BrO variability in the lower troposphere but probably not to the extent of totally obscuring "BrO clouds" that originate from the surface snow/ice source of bromine in the high Arctic. A budget analysis of the simulated air-surface exchange of bromine compounds suggests that a "bromine explosion" occurs in the interstitial air of the snowpack and/or is accelerated by heterogeneous reactions on the surface of wind-blown snow in ambient air, both of which are not represented explicitly in our simple model but could have been approximated by a parameter adjustment for the yield of Br2 from the trigger.

Changes in biologically active ultraviolet radiation reaching the Earth's surface.

PubMed

McKenzie, Richard L; Björn, Lars Olof; Bais, Alkiviadis; Ilyasad, Mohammad

2003-01-01

Since publication of the 1998 UNEP Assessment, there has been continued rapid expansion of the literature on UV-B radiation. Many measurements have demonstrated the inverse relationship between column ozone amount and UV radiation, and in a few cases long-term increases due to ozone decreases have been identified. The quantity, quality and availability of ground-based UV measurements relevant to assessing the environmental impacts of ozone changes continue to improve. Recent studies have contributed to delineating regional and temporal differences due to aerosols, clouds, and ozone. Improvements in radiative transfer modelling capability now enable more accurate characterization of clouds, snow-cover, and topographical effects. A standardized scale for reporting UV to the public has gained wide acceptance. There has been increased use of satellite data to estimate geographic variability and trends in UV. Progress has been made in assessing the utility of satellite retrievals of UV radiation by comparison with measurements at the Earth's surface. Global climatologies of UV radiation are now available on the Internet. Anthropogenic aerosols play a more important role in attenuating UV irradiances than has been assumed previously, and this will have implications for the accuracy of UV retrievals from satellite data. Progress has been made inferring historical levels of UV radiation using measurements of ozone (from satellites or from ground-based networks) in conjunction with measurements of total solar radiation obtained from extensive meteorological networks. We cannot yet be sure whether global ozone has reached a minimum. Atmospheric chlorine concentrations are beginning to decrease. However, bromine concentrations are still increasing. While these halogen concentrations remain high, the ozone layer remains vulnerable to further depletion from events such as volcanic eruptions that inject material into the stratosphere. Interactions between global warming and ozone depletion could delay ozone recovery by several years, and this topic remains an area of intense research interest. Future changes in greenhouse gases will affect the future evolution of ozone through chemical, radiative, and dynamic processes In this highly coupled system, an evaluation of the relative importance of these processes is difficult: studies are ongoing. A reliable assessment of these effects on total column ozone is limited by uncertainties in lower stratospheric response to these changes. At several sites, changes in UV differ from those expected from ozone changes alone, possibly as a result of long-term changes in aerosols, snow cover, or clouds. This indicates a possible interaction between climate change and UV radiation. Cloud reflectance measured by satellite has shown a long-term increase at some locations, especially in the Antarctic region, but also in Central Europe, which would tend to reduce the UV radiation. Even with the expected decreases in atmospheric chlorine, it will be several years before the beginning of an ozone recovery can be unambiguously identified at individual locations. Because UV-B is more variable than ozone, any identification of its recovery would be further delayed.

Contributions of regional and intercontinental transport to surface ozone in the Tokyo area

NASA Astrophysics Data System (ADS)

Yoshitomi, M.; Wild, O.; Akimoto, H.

2011-08-01

Japan lies downwind of the Asian continent and for much of the year air quality is directly influenced by emissions of ozone precursors over these heavily-populated and rapidly-industrializing regions. This study examines the extent to which oxidant transport from regional and distant anthropogenic sources influences air quality in Japan in springtime, when these contributions are largest. We find that European and North American contributions to surface ozone over Japan in spring are persistent, averaging 3.5±1.1 ppb and 2.8±0.5 ppb respectively, and are greatest in cold continental outflow conditions following the passage of cold fronts. Contributions from China are larger, 4.0±2.8 ppb, and more variable, as expected for a closer source region, and are generally highest near cold fronts preceding the influence of more distant sources. The stratosphere provides a varying but ever-present background of ozone of about 11.2±2.5 ppb during spring. Local sources over Japan and Korea have a relatively small impact on mean ozone, 2.4±7.6 ppb, but this masks a strong diurnal signal, and local sources clearly dominate during episodes of high daytime ozone. By examining the meteorological mechanisms that favour transport from different source regions, we demonstrate that while maximum foreign influence generally does not occur at the same time as the greatest buildup of oxidants from local sources, it retains a significant influence under these conditions. It is thus clear that while meteorological boundaries provide some protection from foreign influence during oxidant outbreaks in Tokyo, these distant sources still make a substantial contribution to exceedance of the Japanese ozone air quality standard in springtime.

Contributions of regional and intercontinental transport to surface ozone in Tokyo

NASA Astrophysics Data System (ADS)

Yoshitomi, M.; Wild, O.; Akimoto, H.

2011-04-01

Japan lies downwind of the Asian continent and for much of the year air quality is directly influenced by emissions of ozone precursors over these heavily-populated and rapidly-industrializing regions. This study examines the extent to which oxidant transport from regional and distant anthropogenic sources influences air quality in Japan in springtime, when these contributions are largest. We find that European and North American contributions to surface ozone over Japan in spring are persistent, averaging 3.5±1.1 ppb and 2.8±0.5 ppb respectively, and are greatest in cold continental outflow conditions following the passage of cold fronts. Contributions from China are larger, 4.0±2.8 ppb, and more variable, as expected for a closer source region, and are generally highest near cold fronts preceding the influence of more distant sources. The stratosphere provides a varying but ever-present background of ozone of about 11.2±2.5 ppb during spring. Local sources over Japan and Korea have a relatively small impact on mean ozone, 2.4±7.6 ppb, but this masks a strong diurnal signal, and local sources clearly dominate during episodes of high daytime ozone. By examining the meteorological mechanisms that favour transport from different source regions, we demonstrate that while maximum foreign influence generally does not occur at the same time as the greatest buildup of oxidants from local sources, it retains a significant influence under these conditions. It is thus clear that while meteorological boundaries provide some protection from foreign influence during oxidant outbreaks in Tokyo, these distant sources still make a substantial contribution to exceedance of the Japanese ozone air quality standard in springtime.

Multi-year objective analyses of warm season ground-level ozone and PM2.5 over North America using real-time observations and Canadian operational air quality models

NASA Astrophysics Data System (ADS)

Robichaud, A.; Ménard, R.

2014-02-01

Multi-year objective analyses (OA) on a high spatiotemporal resolution for the warm season period (1 May to 31 October) for ground-level ozone and for fine particulate matter (diameter less than 2.5 microns (PM2.5)) are presented. The OA used in this study combines model outputs from the Canadian air quality forecast suite with US and Canadian observations from various air quality surface monitoring networks. The analyses are based on an optimal interpolation (OI) with capabilities for adaptive error statistics for ozone and PM2.5 and an explicit bias correction scheme for the PM2.5 analyses. The estimation of error statistics has been computed using a modified version of the Hollingsworth-Lönnberg (H-L) method. The error statistics are "tuned" using a χ2 (chi-square) diagnostic, a semi-empirical procedure that provides significantly better verification than without tuning. Successful cross-validation experiments were performed with an OA setup using 90% of data observations to build the objective analyses and with the remainder left out as an independent set of data for verification purposes. Furthermore, comparisons with other external sources of information (global models and PM2.5 satellite surface-derived or ground-based measurements) show reasonable agreement. The multi-year analyses obtained provide relatively high precision with an absolute yearly averaged systematic error of less than 0.6 ppbv (parts per billion by volume) and 0.7 μg m-3 (micrograms per cubic meter) for ozone and PM2.5, respectively, and a random error generally less than 9 ppbv for ozone and under 12 μg m-3 for PM2.5. This paper focuses on two applications: (1) presenting long-term averages of OA and analysis increments as a form of summer climatology; and (2) analyzing long-term (decadal) trends and inter-annual fluctuations using OA outputs. The results show that high percentiles of ozone and PM2.5 were both following a general decreasing trend in North America, with the eastern part of the United States showing the most widespread decrease, likely due to more effective pollution controls. Some locations, however, exhibited an increasing trend in the mean ozone and PM2.5, such as the northwestern part of North America (northwest US and Alberta). Conversely, the low percentiles are generally rising for ozone, which may be linked to the intercontinental transport of increased emissions from emerging countries. After removing the decadal trend, the inter-annual fluctuations of the high percentiles are largely explained by the temperature fluctuations for ozone and to a lesser extent by precipitation fluctuations for PM2.5. More interesting is the economic short-term change (as expressed by the variation of the US gross domestic product growth rate), which explains 37% of the total variance of inter-annual fluctuations of PM2.5 and 15% in the case of ozone.

Soybean Cultivar Variation in Response to Elevated Ozone Concentration

USDA-ARS?s Scientific Manuscript database

Crop losses to ozone damage are conservatively estimated to cost $1 to $3 billion in the U.S. These costs will rise as surface-level ozone increases over this century. A critical step in maximizing soybean yield in a future of rising tropospheric ozone is identifying variation in cultivar responses,...

Multi-Model Comparison of Lateral Boundary Contributions to Surface Ozone Over the United States

EPA Science Inventory

As the National Ambient Air Quality Standards (NAAQS) for ozone become more stringent, there has been growing attention on characterizing the contributions and the uncertainties in ozone from outside the US to the ozone concentrations within the US. The third phase of the Air Qua...

Lower tropospheric ozone and aerosol measurements at a coastal mountain site in Northern California

NASA Astrophysics Data System (ADS)

Post, A.; Conley, S. A.; Zhao, Y.; Cliff, S. S.; Faloona, I. C.; Wexler, A. S.; Lighthall, D.

2012-12-01

Increasing concern over the impacts of exogenous air pollution in California's Central Valley have prompted the establishment of a coastal, high altitude monitoring site at the Chews Ridge Observatory (1550 m) approximately 30 km east of Point Sur in Monterey County. Six months of ozone and aerosol measurements are presented in the context of long-range transport and its potential impact on surface air quality in the southern San Joaquin Valley. Moreover, approximately monthly ozone surveys are conducted by aircraft upwind, over the Pacific Ocean, and downwind, over the Central Valley, to characterize horizontal and vertical transport across the coastal mountains. The measurements exhibit no systematic diurnal variations of ozone or water vapor, an indication that the site primarily samples lower free tropospheric air which has not been significantly influenced by either local emissions or convective coupling to the surface. Aerosol size is measured with a scanning mobility particle sizer and composition is analyzed with an 8-stage rotating drum impactor whose substrates are characterized by X-ray fluorescence. Various elemental ratios and back trajectory calculations are used to infer the temporal patterns of influence that long range transport has on California air quality.

TOLNet Data Format for Lidar Ozone Profile & Surface Observations

NASA Astrophysics Data System (ADS)

Chen, G.; Aknan, A. A.; Newchurch, M.; Leblanc, T.

2015-12-01

The Tropospheric Ozone Lidar Network (TOLNet) is an interagency initiative started by NASA, NOAA, and EPA in 2011. TOLNet currently has six Lidars and one ozonesonde station. TOLNet provides high-resolution spatio-temporal measurements of tropospheric (surface to tropopause) ozone and aerosol vertical profiles to address fundamental air-quality science questions. The TOLNet data format was developed by TOLNet members as a community standard for reporting ozone profile observations. The development of this new format was primarily based on the existing NDAAC (Network for the Detection of Atmospheric Composition Change) format and ICARTT (International Consortium for Atmospheric Research on Transport and Transformation) format. The main goal is to present the Lidar observations in self-describing and easy-to-use data files. The TOLNet format is an ASCII format containing a general file header, individual profile headers, and the profile data. The last two components repeat for all profiles recorded in the file. The TOLNet format is both human and machine readable as it adopts standard metadata entries and fixed variable names. In addition, software has been developed to check for format compliance. To be presented is a detailed description of the TOLNet format protocol and scanning software.

Analyzer for measurement of nitrogen oxide concentration by ozone content reduction in gas using solid state chemiluminescent sensor

NASA Astrophysics Data System (ADS)

Chelibanov, V. P.; Ishanin, G. G.; Isaev, L. N.

2014-05-01

Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

Impact of Enhanced Ozone Deposition and Halogen Chemistry on Tropospheric Ozone over the Northern Hemisphere.

PubMed

Sarwar, Golam; Gantt, Brett; Schwede, Donna; Foley, Kristen; Mathur, Rohit; Saiz-Lopez, Alfonso

2015-08-04

Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen chemistry in a comprehensive atmospheric modeling system. The enhanced ozone deposition treatment accounts for the interaction of iodide in seawater with ozone and increases deposition velocities by 1 order of magnitude. Halogen chemistry includes detailed chemical reactions of organic and inorganic bromine and iodine species. Two different simulations are completed with the halogen chemistry: without and with photochemical reactions of higher iodine oxides. Enhanced deposition reduces mean summer-time surface ozone by ∼3% over marine regions in the Northern Hemisphere. Halogen chemistry without the photochemical reactions of higher iodine oxides reduces surface ozone by ∼15% whereas simulations with the photochemical reactions of higher iodine oxides indicate ozone reductions of ∼48%. The model without these processes overpredicts ozone compared to observations whereas the inclusion of these processes improves predictions. The inclusion of photochemical reactions for higher iodine oxides leads to ozone predictions that are lower than observations, underscoring the need for further refinement of the halogen emissions and chemistry scheme in the model.

Ozone Variability and Anomalies Observed During SENEX and SEAC4RS Campaigns in 2013

NASA Astrophysics Data System (ADS)

Kuang, Shi; Newchurch, Michael J.; Thompson, Anne M.; Stauffer, Ryan M.; Johnson, Bryan J.; Wang, Lihua

2017-10-01

Tropospheric ozone variability occurs because of multiple forcing factors including surface emission of ozone precursors, stratosphere-to-troposphere transport (STT), and meteorological conditions. Analyses of ozonesonde observations made in Huntsville, AL, during the peak ozone season (May to September) in 2013 indicate that ozone in the planetary boundary layer was significantly lower than the climatological average, especially in July and August when the Southeastern United States (SEUS) experienced unusually cool and wet weather. Because of a large influence of the lower stratosphere, however, upper tropospheric ozone was mostly higher than climatology, especially from May to July. Tropospheric ozone anomalies were strongly anticorrelated (or correlated) with water vapor (or temperature) anomalies with a correlation coefficient mostly about 0.6 throughout the entire troposphere. The regression slopes between ozone and temperature anomalies for surface up to midtroposphere are within 3.0-4.1 ppbv K-1. The occurrence rates of tropospheric ozone laminae due to STT are ≥50% in May and June and about 30% in July, August, and September suggesting that the stratospheric influence on free-tropospheric ozone could be significant during early summer. These STT laminae have a mean maximum ozone enhancement over the climatology of 52 ± 33% (35 ± 24 ppbv) with a mean minimum relative humidity of 2.3 ± 1.7%.

Seasonal Changes in Tropospheric Ozone Concentrations over South Korea and Its Link to Ozone Precursors

NASA Astrophysics Data System (ADS)

Jung, H. C.; Moon, B. K.; Wie, J.

2017-12-01

Concentration of tropospheric ozone over South Korea has steadily been on the rise in the last decades, mainly due to rapid industrializing and urbanizing in the Eastern Asia. To identify the characteristics of tropospheric ozone in South Korea, we fitted a sine function to the surface ozone concentration data from 2005 to 2014. Based on fitted sine curves, we analyzed the shifts in the dates on which ozone concentration reached its peak in the calendar year. Ozone monitoring sites can be classified into type types: where the highest annual ozone concentration kept occurring sooner (Esites) and those that kept occurring later (Lsites). The seasonal analysis shows that the surface ozone had increased more rapidly in Esites than in Lsites in the past decade during springtime and vice-versa during summertime. We tried to find the reason for the different seasonal trends with the relationship between ozone and ozone precursors. As a result, it was found that the changes in the ground-level ozone concentration in the spring and summer times are considerably influenced by changes in nitrogen dioxide concentration, and this is closely linked to the destruction (production) process of ozone by nitrogen dioxide in spring (summer). The link between tropospheric ozone and nitrogen dioxide discussed in this study will have to be thoroughly examined through climate-chemistry modeling in the future. Acknowledgements This research was supported by the Korea Ministry of Environment (MOE) as "Climate Change Correspondence Program."

Ozone depletion - Ultraviolet radiation and phytoplankton biology in Antarctic waters

NASA Technical Reports Server (NTRS)

Smith, R. C.; Prezelin, B. B.; Baker, K. S.; Bidigare, R. R.; Boucher, N. P.; Coley, T.; Karentz, D.; Macintyre, S.; Matlick, H. A.; Menzies, D.

1992-01-01

The near-50-percent thinning of the stratospheric ozone layer over the Antarctic, with increased passage of mid-UV radiation to the surface of the Southern Ocean, has prompted concern over possible radiation damage to the near-surface phytoplankton communities that are the bases of Antarctic marine ecosystems. As the ozone layer thinned, a 6-week study of the marginal ice zone of the Bellingshousen Sea in the austral spring of 1990 noted sea-surface and depth-dependent ratios of mid-UV irradiance to total irradiance increased, and mid-UV inhibition of photosynthesis increased. A 6-12 percent reduction in primary production associated with ozone depletion was estimated to have occurred over the course of the present study.

Regional trend analysis of surface ozone observations from monitoring networks in eastern North America, Europe and East Asia

NASA Astrophysics Data System (ADS)

Chang, K. L.; Petropavlovskikh, I. V.; Cooper, O. R.; Schultz, M.; Wang, T.

2017-12-01

Surface ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity. The Tropospheric Ozone Assessment Report (TOAR) is designed to provide the research community with an up-to-date observation-based overview of tropospheric ozone's global distribution and trends. The TOAR Surface Ozone Database contains ozone metrics at thousands of monitoring sites around the world, densely clustered across mid-latitude North America, western Europe and East Asia. Calculating regional ozone trends across these locations is challenging due to the uneven spacing of the monitoring sites across urban and rural areas. To meet this challenge we conducted a spatial and temporal trend analysis of several TOAR ozone metrics across these three regions for summertime (April-September) 2000-2014, using the generalized additive mixed model (GAMM). Our analysis indicates that East Asia has the greatest human and plant exposure to ozone pollution among investigating regions, with increasing ozone levels through 2014. The results also show that ozone mixing ratios continue to decline significantly over eastern North America and Europe, however, there is less evidence for decreases of daytime average ozone at urban sites. The present-day spatial coverage of ozone monitors in East Asia (South Korea and Japan) and eastern North America is adequate for estimating regional trends by simply taking the average of the individual trends at each site. However the European network is more sparsely populated across its northern and eastern regions and therefore a simple average of the individual trends at each site does not yield an accurate regional trend. This analysis demonstrates that the GAMM technique can be used to assess the regional representativeness of existing monitoring networks, indicating those networks for which a regional trend can be obtained by simply averaging the trends of all individual sites and those networks that require a more sophisticated statistical approach.

Rate and reaction probability of the surface reaction between ozone and dihydromyrcenol measured in a bench scale reactor and a room-sized chamber

NASA Astrophysics Data System (ADS)

Shu, Shi; Morrison, Glenn C.

2012-02-01

Low volatility terpenoids emitted from consumer products can react with ozone on surfaces and may significantly alter concentrations of ozone, terpenoids and reaction products in indoor air. We measured the reaction probability and a second-order surface-specific reaction rate for the ozonation of dihydromyrcenol, a representative indoor terpenoid, adsorbed onto polyvinylchloride (PVC), glass, and latex paint coated spheres. The reaction probability ranged from (0.06-8.97) × 10 -5 and was very sensitive to humidity, substrate and mass adsorbed. The average surface reaction probability is about 10 times greater than that for the gas-phase reaction. The second-order surface-specific rate coefficient ranged from (0.32-7.05) × 10 -15 cm 4 s -1 molecule -1and was much less sensitive to humidity, substrate, or mass adsorbed. We also measured the ozone deposition velocity due to adsorbed dihydromyrcenol on painted drywall in a room-sized chamber, Based on that, we calculated the rate coefficient ((0.42-1.6) × 10 -15 cm 4 molecule -1 s -1), which was consistent with that derived from bench-scale experiments for the latex paint under similar conditions. We predict that more than 95% of dihydromyrcenol oxidation takes place on indoor surfaces, rather than in building air.

Sensitivity of U.S. surface ozone to future emissions and climate changes

NASA Astrophysics Data System (ADS)

Tao, Zhining; Williams, Allen; Huang, Ho-Chun; Caughey, Michael; Liang, Xin-Zhong

2007-04-01

The relative contributions of projected future emissions and climate changes to U.S. surface ozone concentrations are investigated focusing on California, the Midwest, the Northeast, and Texas. By 2050 regional average ozone concentrations increase by 2-15% under the IPCC SRES A1Fi (``dirty'') scenario, and decrease by 4-12% under the B1 (relatively ``clean'') scenario. However, the magnitudes of ozone changes differ significantly between major metropolitan and rural areas. These ozone changes are dominated by the emissions changes in 61% area of the contiguous U.S. under the B1 scenario, but are largely determined by the projected climate changes in 46% area under the A1Fi scenario. In the ozone responses to climate changes, the biogenic emissions changes contribute strongly over the Northeast, moderately in the Midwest, and negligibly in other regions.

Ozonation of 1,2-dihydroxybenzene in the presence of activated carbon.

PubMed

Zaror, C; Soto, G; Valdés, H; Mansilla, H

2001-01-01

This work aims at obtaining experimental data on ozonation of 1,2-dihydroxybenzene (DHB) in the presence of activated carbon, with a view to assessing possible changes in its surface chemical structure and adsorption capacity. Experiments were conducted in a 0.5 L reactor, loaded with 2 g Filtrasorb 400 granular activated carbon, and 1-5 mM DHB aqueous solution at pH 2-8. Ozone gas was generated with an Ozocav generator, and fed into the reactor for a given exposure time, in the range 0.5-240 min, at 25 degrees C and 1 atm. After each run, liquid and activated carbon samples were taken for chemical assays. Soluble organic groups present on the active carbon surface were desorbed and analysed by GC-MS and HPLC. Activated carbon chemical surface properties were analysed using TPD, FT-IR, and XPS techniques. Reactions between ozone and adsorbed DHB were shown to be fast, leading to formation of C-6, C-4 and C-2 by-products. Oxygenated surface groups, particularly, COOH and C = O, increased as a result of ozonation.

Observations of tropospheric trace gases from GOSAT thermal infrared spectra

NASA Astrophysics Data System (ADS)

Ohyama, Hirofumi; Shiomi, Kei; Kawakami, Shuji; Nakajima, Masakatsu; Maki, Takashi; Deushi, Makoto

2013-04-01

Thermal And Near infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS), which is one of the sensors onboard the Greenhouse gases Observing SATellite (GOSAT), measures the sunlight backscattered by the Earth's surface and atmosphere as well as the thermal radiance emitted from the Earth. Atmospheric trace gases such as ozone (O3), water vapor (H2O and HDO), methanol (CH3OH) and ammonia (NH3) are derived from the thermal infrared spectral radiance recorded with the TANSO-FTS by an optimal estimation retrieval approach. TANSO-FTS total ozone columns are compared with Dobson spectrophotometer and Ozone Monitoring Instrument (OMI) data. The TANSO-FTS total ozone retrievals exhibit a positive bias of 3-4% with a root-mean-square difference of 2-6% compared to the Dobson and OMI measurements. We compare TANSO-FTS tropospheric ozone columns to those from ozonesonde data as well as from a three-dimensional chemical-climate model (MRI-CCM2). The TANSO-FTS data have high correlations with the ozonesonde data. The seasonal trends of the retrieved tropospheric ozone are consistent with those of the ozonesonde data. The spatial distribution of the tropospheric ozone from the TANSO-FTS and MRI-CCM2 shows good agreement, especially in the high-level tropospheric ozone regions. We also retrieve tropospheric H2O and HDO profiles simultaneously, accounting for the cross correlations between the water isotopes. The joint retrieval results in precise estimation of the isotope ratio by partial cancellation of systematic errors common to both H2O and HDO. The retrieved profiles and columns are compared with radiosonde, GPS, and ground-based high-resolution FTS data. The temporal and spatial variations of the precipitable water and the isotope ratio are consistent with those of the validation data. Finally, air pollutants such as CH3OH and NH3 are retrieved using the retrieved ozone and water vapor. We present the latitudinal and seasonal variations of CH3OH related to plant growth and biomass burning, and the high-level NH3 in the hot spot areas.

Reanalysis of and attribution to near-surface ozone concentrations in Sweden during 1990-2013

NASA Astrophysics Data System (ADS)

Andersson, Camilla; Alpfjord, Heléne; Robertson, Lennart; Karlsson, Per Erik; Engardt, Magnuz

2017-11-01

We have constructed two data sets of hourly resolution reanalyzed near-surface ozone (O3) concentrations for the period 1990-2013 for Sweden. Long-term simulations from a chemistry-transport model (CTM) covering Europe were combined with hourly ozone concentration observations at Swedish and Norwegian background measurement sites using retrospective variational data analysis. The reanalysis data sets show improved performance over the original CTM when compared to independent observations. In one of the reanalyses, we included all available hourly near-surface O3 observations, whilst in the other we carefully selected time-consistent observations. Based on the second reanalysis we investigated statistical aspects of the distribution of the near-surface O3 concentrations, focusing on the linear trend over the 24-year period. We show that high near-surface O3 concentrations are decreasing and low O3 concentrations are increasing, which is reflected in observed improvement of many health and vegetation indices (apart from those with a low threshold). Using the CTM we also conducted sensitivity simulations to quantify the causes of the observed change, focusing on three factors: change in hemispheric background concentrations, meteorology and anthropogenic emissions. The rising low concentrations of near-surface O3 in Sweden are caused by a combination of all three factors, whilst the decrease in the highest O3 concentrations is caused by European O3 precursor emissions reductions. While studying the impact of anthropogenic emissions changes, we identified systematic differences in the modeled trend compared to observations that must be caused by incorrect trends in the utilized emissions inventory or by too high sensitivity of our model to emissions changes.

New Insights in Tropospheric Ozone and its Variability

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Douglass, Anne R.; Ziemke, Jerry R.; Rodriquez, Jose M.

2011-01-01

We have produced time-slice simulations using the Goddard Earth Observing System Version 5 (GEOS-5) coupled to a comprehensive stratospheric and tropospheric chemical mechanism. These simulations are forced with observed sea surface temperatures over the past 25 years and use constant specified surface emissions, thereby providing a measure of the dynamically controlled ozone response. We examine the model performance in simulating tropospheric ozone and its variability. Here we show targeted comparisons results from our simulations with a multi-decadal tropical tropospheric column ozone dataset obtained from satellite observations of total column ozone. We use SHADOZ ozonesondes to gain insight into the observed vertical response and compare with the simulated vertical structure. This work includes but is not limited to ENSO related variability.

Design of a vehicle based system to prevent ozone loss

NASA Technical Reports Server (NTRS)

Lynn, Sean R.; Bunker, Deborah; Hesbach, Thomas D., Jr.; Howerton, Everett B.; Hreinsson, G.; Mistr, E. Kirk; Palmer, Matthew E.; Rogers, Claiborne; Tischler, Dayna S.; Wrona, Daniel J.

1993-01-01

Reduced quantities of ozone in the atmosphere allow greater levels of ultraviolet light (UV) radiation to reach the earth's surface. This is known to cause skin cancer and mutations. Chlorine liberated from Chlorofluorocarbons (CFC's) and natural sources initiate the destruction of stratospheric ozone through a free radical chain reaction. The project goals are to understand the processes which contribute to stratospheric ozone loss, examine ways to prevent ozone loss, and design a vehicle-based system to carry out the prevention scheme. The 1992/1993 design objectives were to accomplish the first two goals and define the requirements for an implementation vehicle to be designed in detail starting next year. Many different ozone intervention schemes have been proposed though few have been researched and none have been tested. A scheme proposed by R.J. Cicerone, Scott Elliot and R.P.Turco late in 1991 was selected because of its research support and economic feasibility. This scheme uses hydrocarbon injected into the Antarctic ozone hole to form stable compounds with free chlorine, thus reducing ozone depletion. Because most polar ozone depletion takes place during a 3-4 week period each year, the hydrocarbon must be injected during this time window. A study of the hydrocarbon injection requirements determined that 100 aircraft traveling Mach 2.4 at a maximum altitude of 66,000 ft. would provide the most economic approach to preventing ozone loss. Each aircraft would require an 8,000 nm. range and be able to carry 35,000 lbs. of propane. The propane would be stored in a three-tank high pressure system. Missions would be based from airport regions located in South America and Australia. To best provide the requirements of mission analysis, an aircraft with L/D(sub cruise) = 10.5, SFC = 0.65 (the faculty advisor suggested that this number is too low) and a 250,000 lb TOGW was selected as a baseline. Modularity and multi-role functionality were selected to be key design features. Modularity provides ease of turnaround for the down-time critical mission. Multi-role functionality allows the aircraft to be used beyond its design mission, perhaps as an High Speed Civil Transport (HSCT) or for high altitude research.

Highly elevated atmospheric levels of volatile organic compounds in the Uintah Basin, Utah.

PubMed

Helmig, D; Thompson, C R; Evans, J; Boylan, P; Hueber, J; Park, J-H

2014-05-06

Oil and natural gas production in the Western United States has grown rapidly in recent years, and with this industrial expansion, growing environmental concerns have arisen regarding impacts on water supplies and air quality. Recent studies have revealed highly enhanced atmospheric levels of volatile organic compounds (VOCs) from primary emissions in regions of heavy oil and gas development and associated rapid photochemical production of ozone during winter. Here, we present surface and vertical profile observations of VOC from the Uintah Basin Winter Ozone Studies conducted in January-February of 2012 and 2013. These measurements identify highly elevated levels of atmospheric alkane hydrocarbons with enhanced rates of C2-C5 nonmethane hydrocarbon (NMHC) mean mole fractions during temperature inversion events in 2013 at 200-300 times above the regional and seasonal background. Elevated atmospheric NMHC mole fractions coincided with build-up of ambient 1-h ozone to levels exceeding 150 ppbv (parts per billion by volume). The total annual mass flux of C2-C7 VOC was estimated at 194 ± 56 × 10(6) kg yr(-1), equivalent to the annual VOC emissions of a fleet of ∼100 million automobiles. Total annual fugitive emission of the aromatic compounds benzene and toluene, considered air toxics, were estimated at 1.6 ± 0.4 × 10(6) and 2.0 ± 0.5 × 10(6) kg yr(-1), respectively. These observations reveal a strong causal link between oil and gas emissions, accumulation of air toxics, and significant production of ozone in the atmospheric surface layer.

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

NASA Astrophysics Data System (ADS)

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.

Removal of sulfa drugs by sewage treatment in aqueous solution systems: activated carbon treatment and ozone oxidation.

PubMed

Ogata, Fumihiko; Tominaga, Hisato; Kangawa, Moe; Inoue, Kenji; Kawasaki, Naohito

2012-01-01

This study investigates the activated carbon (AC) treatment and ozone oxidation of the sulfa drugs--sulfamethoxazole (SMX), sulfamonomethoxine (SMM), sulfadimidine (SDD), and sulfadimethoxine (SDM)--in aqueous solution systems. Three AC samples were prepared from Shirasagi (AC1 and AC2) and coal (AC3), and the surface functional groups, solution pH, specific surface areas, pore volumes, and morphologies of the three samples were evaluated. The specific surface areas were in the following order: AC1 (1391 m²/g) > AC2 (1053 m²/g) > AC3 (807 m²/g). The pore volume and mean pore diameter of AC3 were greater than those of AC1 and AC2. The concentration of sulfa drugs adsorbed onto the AC samples reached equilibrium within 150 h. Experimental data of the adsorption rate were fitted to a pseudo-second-order model. The amount of sulfa drugs adsorbed onto the AC samples was in the order of SDM < SMM < SDD < SMX; the mechanism of adsorption of the sulfa drugs onto the AC samples depended on the hydrophobicity of the AC surface. The adsorption isotherm data were fitted to Freundlich and Langmuir models. Ozone was generated from oxygen gas using an A-27 ozone generator, and the complete degradation of the sulfa drugs by ozone treatment at 60 mL/min was achieved within 50 min. Ozone treatment caused the structure of the sulfa drugs to decompose via ozone oxidation.

Stratospheric Instrusion Catalog: A 10-Year Compilation of Events Identified by using TRACK with NASA's MERRA-2 Reanalysis

NASA Technical Reports Server (NTRS)

Knowland, K. Emma; Ott, Lesley E.; Duncan, Bryan N.; Wargan, Kris; Hodges, Kevin

2017-01-01

Stratospheric intrusions "the introduction of ozone-rich stratospheric air into the troposphere" have been linked with surface ozone air quality exceedances, especially at the high elevations in the western USA in springtime. However, the impact of stratospheric intrusions in the remaining seasons and over the rest of the USA is less clear. A new approach to the study of stratospheric intrusions uses NASA's Goddard Earth Observing System Model (GEOS) model and assimilation products with an objective feature tracking algorithm to investigate the atmospheric dynamics that generate stratospheric intrusions and the different mechanisms through which stratospheric intrusions may influence tropospheric chemistry and surface air quality seasonally over both the western and the eastern USA. A catalog of stratospheric intrusions identified in the MERRA-2 reanalysis was produced for the period 2004-2015 and validated against surface ozone observations (focusing on those which exceed the national air quality standard) and a recent data set of stratospheric intrusion-influenced air quality exceedance flags from the US Environmental Protection Agency (EPA). Considering not all ozone exceedances have been flagged by the EPA, a collection of stratospheric intrusions can support air quality agencies for more rapid identification of the impact of stratospheric air on surface ozone and demonstrates that future operational analyses may aid in forecasting such events. An analysis of the spatiotemporal variability of stratospheric intrusions over the continental US was performed, and while the spring over the western USA does exhibit the largest number of stratospheric intrusions affecting the lower troposphere, the number of intrusions in the remaining seasons and over the eastern USA is sizable. By focusing on the major modes of variability that influence weather in the USA, such as the Pacific North American (PNA) teleconnection index, predicative meteorological patterns associated with stratospheric intrusions and their regional effects on tropospheric ozone were identified. Improved understanding of the connections between large-scale climate variability and local-scale dynamically-driven air quality events may support improved seasonal prediction of such events.

Stratospheric Intrusion Catalog: A 10-year Compilation of Events Identified By Using an Objective Feature Tracking Model With NASA's MERRA-2 Reanalysis

NASA Astrophysics Data System (ADS)

Knowland, K. E.; Ott, L. E.; Duncan, B. N.; Wargan, K.; Hodges, K.

2017-12-01

Stratospheric intrusions - the introduction of ozone-rich stratospheric air into the troposphere - have been linked with surface ozone air quality exceedances, especially at the high elevations in the western USA in springtime. However, the impact of stratospheric intrusions in the remaining seasons and over the rest of the USA is less clear. A new approach to the study of stratospheric intrusions uses NASA's Goddard Earth Observing System Model (GEOS) model and assimilation products with an objective feature tracking algorithm to investigate the atmospheric dynamics that generate stratospheric intrusions and the different mechanisms through which stratospheric intrusions may influence tropospheric chemistry and surface air quality seasonally over both the western and the eastern USA. A catalog of stratospheric intrusions identified in the MERRA-2 reanalysis was produced for the period 2005-2014 and validated against surface ozone observations (focusing on those which exceed the national air quality standard) and a recent data set of stratospheric intrusion-influenced air quality exceedance flags from the US Environmental Protection Agency (EPA). Considering not all ozone exceedances have been flagged by the EPA, a collection of stratospheric intrusions can support air quality agencies for more rapid identification of the impact of stratospheric air on surface ozone and demonstrates that future operational analyses may aid in forecasting such events. An analysis of the spatiotemporal variability of stratospheric intrusions over the continental US was performed, and while the spring over the western USA does exhibit the largest number of stratospheric intrusions affecting the lower troposphere, the number of intrusions in the remaining seasons and over the eastern USA is sizable. By focusing on the major modes of variability that influence weather in the USA, such as the Pacific North American (PNA) teleconnection index, predicative meteorological patterns associated with stratospheric intrusions and their regional effects on tropospheric ozone were identified. Improved understanding of the connections between large-scale climate variability and local-scale dynamically-driven air quality events may support improved seasonal prediction of such events.

Model Calculations of the Impact of NO(x) from Air Traffic, Lightning and Surface Emissions, Compared with Measurements

NASA Technical Reports Server (NTRS)

Meijer, E. W.; vanVelthoven, P. F. J.; Thompson, A. M.; Pfister, L.; Schlager, H.; Schulte, P.; Kelder, H.

1999-01-01

The impact of NO(x) from aircraft emissions, lightning and surface contributions on atmospheric nitrogen oxides and ozone has been investigated with the three-dimensional global chemistry transport model TM3 by partitioning the nitrogen oxides and ozone according to source category. The results have been compared with POLINAT II and SONEX airborne measurements in the North Atlantic flight corridor in 1997. Various cases have been investigated: measurements during a stagnant anti-cyclone and an almost cut-off low, both with expected high aircraft contributions, a southward bound flight with an expected strong flight corridor gradient and lightning contributions in the South, and a transatlantic flight with expected boundary layer pollution near the U.S. coast. The agreement between modeled results and measurements is reasonably good for NO and ozone. Also, the calculated impact of the three defined sources were consistent with the estimated exposure of the sampled air to these sources, obtained by specialized back-trajectory model products.

Impact of Stratospheric Ozone Zonal Asymmetries on the Tropospheric Circulation

NASA Technical Reports Server (NTRS)

Tweedy, Olga; Waugh, Darryn; Li, Feng; Oman, Luke

2015-01-01

The depletion and recovery of Antarctic ozone plays a major role in changes of Southern Hemisphere (SH) tropospheric climate. Recent studies indicate that the lack of polar ozone asymmetries in chemistry climate models (CCM) leads to a weaker and warmer Antarctic vortex, and smaller trends in the tropospheric mid-latitude jet and the surface pressure. However, the tropospheric response to ozone asymmetries is not well understood. In this study we report on a series of integrations of the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to further examine the effect of zonal asymmetries on the state of the stratosphere and troposphere. Integrations with the full, interactive stratospheric chemistry are compared against identical simulations using the same CCM except that (1) the monthly mean zonal mean stratospheric ozone from first simulation is prescribed and (2) ozone is relaxed to the monthly mean zonal mean ozone on a three day time scale. To analyze the tropospheric response to ozone asymmetries, we examine trends and quantify the differences in temperatures, zonal wind and surface pressure among the integrations.

TOLNet ozone lidar intercomparison during the discover-aq and frappé campaigns

NASA Astrophysics Data System (ADS)

Newchurch, Michael J.; Alvarez, Raul J.; Berkoff, Timothy A.; Carrion, William; DeYoung, Russell J.; Ganoe, Rene; Gronoff, Guillaume; Kirgis, Guillaume; Kuang, Shi; Langford, Andy O.; Leblanc, Thierry; McGee, Thomas J.; Pliutau, Denis; Senff, Christoph; Sullivan, John T.; Sumnicht, Grant; Twigg, Laurence W.; Wang, Lihua

2018-04-01

The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure atmospheric profiles of ozone and aerosols, to contribute to air-quality studies, atmospheric modeling, and satellite validation efforts. The accurate characterization of these lidars is of critical interest, and is necessary to determine cross-instrument calibration uniformity. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the "Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality" (DISCOVER-AQ) mission and the "Front Range Air Pollution and Photochemistry Éxperiment" (FRAPPÉ) to measure sub-hourly ozone variations from near the surface to the top of the troposphere. Although large differences occur at few individual altitudes in the near field and far field range, the TOLNet lidars agree with each other within ±4%. These results indicate excellent measurement accuracy for the TOLNet lidars that is suitable for use in air-quality and ozone modeling efforts.

[Observation of ozone dry deposition in the field of winter wheat.

PubMed

Li, Shuo; Zheng, You Fei; Wu, Rong Jun; Yin, Ji Fu; Xu, Jing Xin; Zhao, Hui; Sun, Jian

2016-06-01

Ozone is one of the main atmospheric pollutants over surface layer, and its increasing surface ozone concentration and its impact on main crops have become the focus of the public. In order to explore ozone deposition law and environmental factors influencing ozone deposition process, this study used the micrometeorological methods and carried out the experiment under natural conditions. The results showed that during the observational period (the vigorously growing season of wheat), the mean value of ozone flux was -0.35 μg·m -2 ·s -1 (the negative sign indicated that the deposition direction was toward the ground). The mean rate of ozone deposition was 0.55 cm·s -1 . The mean value of aerodynamic resistance was 30 s·m -1 , the mean value of sub-layer resistance was 257 s·m -1 , and that of the canopy layer stomatic resistance was 163 s·m -1 . All the test parameters presented distinct diurnal fluctuation. The ozone deposition resistance was influenced by friction velocity, solar radiation velocity, temperature, relative humidity and other factors.

Feasibility of Sensing Tropospheric Ozone with MODIS 9.6 Micron Observations

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Iacovazzi, R., Jr.; Moon-Yoo, Jung

2004-01-01

With the infrared observations made by the Moderate Resolution Imaging Spectrometer (MODIS) on board the EOS-Aqua satellite, which include the 9.73 micron channel, a method is developed to deduce horizontal patterns of tropospheric ozone in cloud free conditions on a scale of about 100 km. It is assumed that on such small scale, at a given instant, horizontal changes in stratospheric ozone are small compared to that in the troposphere. From theoretical simulations it is found that uncertainties in the land surface emissivity and the vertical thermal stratification in the troposphere can lead to significant errors in the inferred tropospheric ozone. Because of this reason in order to derive horizontal patterns of tropospheric ozone in a given geographic area a tuning of this method is necessary with the help of a few dependent cases. After tuning, this method is applied to independent cases of MODIS data taken over Los Angeles basin in cloud free conditions to derive horizontal distribution of ozone in the troposphere. Preliminary results indicate that the derived patterns of ozone resemble crudely the patterns of surface ozone reported by EPA.

Using Source Apportionment to Evaluate the Cross State Transport of Ozone in the Eastern United States

NASA Astrophysics Data System (ADS)

Goldberg, D. L.; Canty, T. P.; Hembeck, L.; Vinciguerra, T.; Carpenter, S. F.; Anderson, D. C.; Salawitch, R. J.; Dickerson, R. R.

2014-12-01

The amount of air pollution crossing state lines has great policy implications. Using the ozone source apportionment tool (OSAT) in the Comprehensive Air-Quality Model with Extensions (CAMx) version 6.10, we can quantify how much ozone is generated locally versus transported from upwind locations. Initial results show that up to 70% of the surface ozone in Maryland during poor air quality days in the summer of July 2011 can be attributed to pollution from outside of the state's borders. Modifications to the CB05 gas-phase chemistry mechanism, supported by literature recommendations and improve agreement with NASA's DISCOVER-AQ Maryland aircraft campaign, can further increase this percentage. Additionally, we show the role of upwind sources and background ozone has become increasingly important as local emissions of ozone precursors continue to drop, starting with the steep reductions imposed in 2002 in response to Maryland's State Implementation Plan submitted to EPA. This study suggests future efforts to control surface ozone must include a meaningful strategy for dealing with cross-state transport of ozone precursors.

Ozone treatment of textile wastewaters for reuse.

PubMed

Ciardelli, G; Capannelli, G; Bottino, A

2001-01-01

Treatment of textile wastewaters by means of an ozonation pilot plant are described. Wastewaters used were produced by a dyeing and finishing factory and were first treated in an active sludge plant and filtrated through sand. In the appropriate conditions very high colour removal (95-99%) was achieved and the effluent could be reused in production processes requiring water of high quality as dyeing yarns or light colorations. Even if the chemical oxygen demand of treated waters was still in a range (75-120 mg/l, a decrease of up to 60%) that was usually considered to be too high for recycling purposes, recycling experiments were successful. The economical viability of the techniques implementation was also demonstrated and the industrial plant is currently under realisation under an EU financed project. The paper considers also the possible improvement of ozone diffusion by means of membrane contactors realised in a second pilot plant, in order to further reduce operating costs of the technique. With respect to traditional systems, the gas/liquid contact surface is much higher being that of the membrane. Ozone at the interface is therefore immediately solubilized and potentially consumed with no additional resistance to the mass transfer.

Tropospheric Ozone Source Attribution in Southern California during Summer 2014 Based on Lidar Measurements and Model Simulations

NASA Technical Reports Server (NTRS)

Granados Munoz, Maria Jose; Johnson, Matthew S.; Leblanc, Thierry

2016-01-01

In the past decades, significant efforts have been made to increase tropospheric ozone long-term monitoring. A large number of ground-based, airborne and space-borne instruments are currently providing valuable data to contribute to better understand tropospheric ozone budget and variability. Nonetheless, most of these instruments provide in-situ surface and column-integrated data, whereas vertically resolved measurements are still scarce. Besides ozonesondes and aircraft, lidar measurements have proven to be valuable tropospheric ozone profilers. Using the measurements from the tropospheric ozone differential absorption lidar (DIAL) located at the JPL Table Mountain Facility, California, and the GEOS-Chem and GEOS-5 model outputs, the impact of the North American monsoon on tropospheric ozone during summer 2014 is investigated. The influence of the Monsoon lightning-induced NOx will be evaluated against other sources (e.g. local anthropogenic emissions and the stratosphere) using also complementary data such as backward-trajectories analysis, coincident water vapor lidar measurements, and surface ozone in-situ measurements.

Barriers and opportunities for passive removal of indoor ozone

NASA Astrophysics Data System (ADS)

Gall, Elliott T.; Corsi, Richard L.; Siegel, Jeffrey A.

2011-06-01

This paper presents a Monte Carlo simulation to assess passive removal materials (PRMs) that remove ozone with no additional energy input and minimal byproduct formation. Distributions for air exchange rate in a subset of homes in Houston, Texas, were taken from the literature and combined with background ozone removal rates in typical houses and previous experimentally determined ozone deposition velocities to activated carbon cloth and gypsum wallboard PRMs. The median ratio of indoor to outdoor ozone was predicted to be 0.16 for homes with no PRMs installed and ranged from 0.047 to 0.12 for homes with PRMs. Median values of ozone removal effectiveness in these homes ranged from 22% to 68% for the conditions investigated. Achieving an ozone removal effectiveness above 50% in half of the homes would require installing a large area of PRMs and providing enhanced air speed to transport pollutants to PRM surfaces. Challenges associated with achieving this removal include optimizing indoor transport and aesthetic implications of large surface areas of PRM materials.

How to most effectively expand the global surface ozone observing network

NASA Astrophysics Data System (ADS)

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 the gap in our ability to measure global surface ozone. An additional 20 surface ozone monitoring sites (a 20 % increase in the World Meteorological Organization Global Atmosphere Watch (WMO GAW) ozone sites or a 1 % increase in the total background network) located on 10 islands and in 10 continental regions would almost double the area observed. The cost of this addition to the network is small compared to other expenditure on atmospheric composition research infrastructure and would provide a significant long-term benefit to our understanding of the composition of the atmosphere, information which will also be available for consideration by air quality control managers and policy makers.

Ozone-vegetation interaction in the Earth system: implications for air quality, ecosystems and agriculture

NASA Astrophysics Data System (ADS)

Tai, A. P. K.; Lombardozzi, D.; Val Martin, M.; Heald, C. L.

2015-12-01

Surface ozone is one of the most significant air pollutants due to its damaging effects not only on human health, but also on vegetation and crop productivity. Chronic ozone exposure has been shown to reduce photosynthesis and interfere with gas exchange in plants, which in turn affect the surface energy balance, carbon sink and other biogeochemical fluxes. Ozone damage on vegetation can thus have major ramifications on climate and atmospheric composition, including possible feedbacks onto ozone itself (see figure) that are not well understood. The damage of ozone on crops has been well documented, but a mechanistic understanding is not well established. Here we present several results pertaining to ozone-vegetation interaction. Using the Community Earth System Model, we find that inclusion of ozone damage on plants reduces the global land carbon sink by up to 5%, while simulated ozone is modified by -20 to +4 ppbv depending on the relative importance of competing mechanisms in different regions. We also perform a statistical analysis of multidecadal global datasets of crop yields, agroclimatic variables and ozone exposures to characterize the spatial variability of crop sensitivity to ozone and temperature extremes, specifically accounting for the confounding effect of ozone-temperature covariation. We find that several crops exhibit stronger sensitivity to ozone than found by previous field studies, with a strong anticorrelation between the sensitivity and average ozone levels that reflects biological adaptive ozone resistance. Our results show that a more complete understanding of ozone-vegetation interaction is necessary to derive more realistic future projections of climate, air quality and agricultural production, and thereby to formulate optimal strategies to safeguard public health and food security.

Future Climate Impacts of Direct Radiative Forcing Anthropogenic Aerosols, Tropospheric Ozone, and Long-lived Greenhouse Gases

NASA Technical Reports Server (NTRS)

Chen, Wei-Ting; Liao, Hong; Seinfeld, John H.

2007-01-01

Long-lived greenhouse gases (GHGs) are the most important driver of climate change over the next century. Aerosols and tropospheric ozone (O3) are expected to induce significant perturbations to the GHG-forced climate. To distinguish the equilibrium climate responses to changes in direct radiative forcing of anthropogenic aerosols, tropospheric ozone, and GHG between present day and year 2100, four 80-year equilibrium climates are simulated using a unified tropospheric chemistry-aerosol model within the Goddard Institute for Space Studies (GISS) general circulation model (GCM) 110. Concentrations of sulfate, nitrate, primary organic (POA) carbon, secondary organic (SOA) carbon, black carbon (BC) aerosols, and tropospheric ozone for present day and year 2100 are obtained a priori by coupled chemistry-aerosol GCM simulations, with emissions of aerosols, ozone, and precursors based on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenario (SRES) A2. Changing anthropogenic aerosols, tropospheric ozone, and GHG from present day to year 2100 is predicted to perturb the global annual mean radiative forcing by +0.18 (considering aerosol direct effects only), +0.65, and +6.54 W m(sup -2) at the tropopause, and to induce an equilibrium global annual mean surface temperature change of +0.14, +0.32, and +5.31 K, respectively, with the largest temperature response occurring at northern high latitudes. Anthropogenic aerosols, through their direct effect, are predicted to alter the Hadley circulation owing to an increasing interhemispheric temperature gradient, leading to changes in tropical precipitation. When changes in both aerosols and tropospheric ozone are considered, the predicted patterns of change in global circulation and the hydrological cycle are similar to those induced by aerosols alone. GHG-induced climate changes, such as amplified warming over high latitudes, weakened Hadley circulation, and increasing precipitation over the Tropics and high latitudes, are consistent with predictions of a number of previous GCM studies. Finally, direct radiative forcing of anthropogenic aerosols is predicted to induce strong regional cooling over East and South Asia. Wintertime rainfall over southeastern China and the Indian subcontinent is predicted to decrease because of the increased atmospheric stability and decreased surface evaporation, while the geographic distribution of precipitation is also predicted to be altered as a result of aerosol-induced changes in wind flow.

Effects of Exposure to Ozone on the Ocular Surface in an Experimental Model of Allergic Conjunctivitis

PubMed Central

Lee, Hun; Kim, Eung Kweon; Kim, Hee Young; Kim, Tae-im

2017-01-01

Based on previous findings that ozone can induce an inflammatory response in the ocular surface of an animal model and in cultured human conjunctival epithelial cells, we investigated whether exposure to ozone exacerbates symptoms of allergic conjunctivitis. We evaluated the effects of exposure to ozone on conjunctival chemosis, conjunctival injection, corneal and conjunctival fluorescein staining scores, production of inflammatory cytokines in tears, and aqueous tear production in a mouse model of allergic conjunctivitis. To validate our in vivo results, we used interleukin (IL)-1α-pretreated conjunctival epithelial cells as an in vitro substitute for the mouse model. We evaluated whether exposure to ozone increased the inflammatory response and altered oxidative status and mitochondrial function in IL-1α-pretreated conjunctival epithelial cells. In the in vivo study, ozone induced increases in conjunctival chemosis, conjunctival injection, corneal and conjunctival fluorescein staining scores, and production of inflammatory cytokines, accompanied by a decrease in tear volume. In the in vitro study, exposure to ozone led to additional increases in IL-6 and tumor necrosis factor-α mRNA levels, which were already induced by treatment with IL-1α. Ozone did not induce any changes in cell viability. Pretreatment with IL-1α increased the expression of manganese superoxide dismutase, and exposure to ozone led to additional increments in the expression of this antioxidant enzyme. Ozone did not induce any changes in mitochondrial activity or expression of mitochondrial enzymes and proteins related to mitochondrial function, with the exception of phosphor-mammalian target of rapamycin. Treatment with butylated hydroxyanisole, a free radical scavenger, attenuated the ozone-induced increases in IL-6 expression in IL-1α-pretreated conjunctival epithelial cells. Therefore, we conclude that exposure to ozone exacerbates the detrimental effects on the integrity of the ocular surface caused by conjunctival allergic reactions, and further increases the inflammatory response in IL-1α-pretreated conjunctival epithelial cells. PMID:28046113

Determination of the UV solar risk in Argentina with high-resolution maps calculated using TOMS ozone climatology

NASA Astrophysics Data System (ADS)

Piacentini, Rubén D.; Cede, Alexander; Luccini, Eduardo; Stengel, Fernando

2004-01-01

The connection between ultraviolet (UV) radiation and various skin diseases is well known. In this work, we present the computer program "UVARG", developed in order to prevent the risk of getting sunburn for persons exposed to solar UV radiation in Argentina, a country that extends from low (tropical) to high southern hemisphere latitudes. The software calculates the so-called "erythemal irradiance", i.e., the spectral irradiance weighted by the McKinlay and Diffey action spectrum for erythema and integrated in wavelength. The erythemal irradiance depends mainly on the following geophysical parameters: solar elevation, total ozone column, surface altitude, surface albedo, total aerosol optical depth and Sun-Earth distance. Minor corrections are due to the variability in the vertical ozone, aerosol, pressure, humidity and temperature profiles and the extraterrestrial spectral solar UV irradiance. Key parameter in the software is a total ozone column climatology incorporating monthly averages, standard deviations and tendencies for the particular geographical situation of Argentina that was obtained from TOMS/NASA satellite data from 1978 to 2000. Different skin types are considered in order to determine the sunburn risk at any time of the day and any day of the year, with and without sunscreen protection. We present examples of the software for three different regions: the high altitude tropical Puna of Atacama desert in the North-West, Tierra del Fuego in the South when the ozone hole event overpasses and low summertime ozone conditions over Buenos Aires, the largest populated city in the country. In particular, we analyzed the maximum time for persons having different skin types during representative days of the year (southern hemisphere equinoxes and solstices). This work was made possible by the collaboration between the Argentine Skin Cancer Foundation, the Institute of Physics Rosario (CONICET-National University of Rosario, Argentina) and the Institute of Medical Physics, University of Innsbruck, Austria. With the teamwork of physicians and physicists, a scientifically reliable and easy-to-handle tool was developed to predict the risk of solar exposure in Argentina. It can be used by dermatologists as well as health authorities and educators in order to prevent health problems induced by solar UV radiation.

A rapid and low energy consumption method to decolorize the high concentration triphenylmethane dye wastewater: operational parameters optimization for the ultrasonic-assisted ozone oxidation process.

PubMed

Zhou, Xian-Jiao; Guo, Wan-Qian; Yang, Shan-Shan; Ren, Nan-Qi

2012-02-01

This research set up an ultrasonic-assisted ozone oxidation process (UAOOP) to decolorize the triphenylmethane dyes wastewater. Five factors - temperature, initial pH, reaction time, ultrasonic power (low frequency 20 kHz), and ozone concentration - were investigated. Response surface methodology was used to find out the major factors influencing color removal rate and the interactions between these factors, and optimized the operating parameters as well. Under the experimental conditions: reaction temperature 39.81 °C, initial pH 5.29, ultrasonic power 60 W and ozone concentration 0.17 g/L, the highest color removals were achieved with 10 min reaction time and the initial concentration of the MG solution was 1000 mg/L. The optimal results indicated that the UAOOP was a rapid, efficient and low energy consumption technique to decolorize the high concentration MG wastewater. The predicted model was approximately in accordance with the experimental cases with correlation coefficients R(2) and R(adj)(2) of 0.9103 and 0.8386. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Atmospheric conditions and transport patterns associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean

NASA Astrophysics Data System (ADS)

Kalabokas, Pavlos; Cammas, Jean-Pierre; Thouret, Valerie; Volz-Thomas, Andreas; Boulanger, Damien; Repapis, Christos

2016-04-01

Vertical summertime ozone profiles measured in the period 1994-2008 in the framework of the MOZAIC project over the Eastern Mediterranean basin (especially over the Cairo and Tel-Aviv airports) were analysed, focusing at first in the lower troposphere (1.5-5 km). The vertical profiles collected during extreme days with very high or very low tropospheric ozone mixing ratios have been examined together with the average profiles of relative humidity, carbon monoxide, temperature gradient, wind speed and the corresponding composite maps of geopotential heights at 850 hPa. As a next step, average profiles corresponding, respectively, to the highest and the lowest ozone mixing ratios for the 0-1.5km layer over Cairo in summer are examined along with their corresponding composite maps of geopotential height (and anomalies), vertical velocity (and anomalies), specific humidity anomalies, precipitable water anomalies, air temperature anomalies and wind speed at 850 hPa as well as the corresponding backward trajectories. Based on the above analysis, it turns out that the lower-tropospheric ozone variability over the eastern Mediterranean area is controlled mainly by the synoptic meteorological conditions, combined with local topographical and meteorological features. In particular, the highest ozone concentrations in the lower troposphere and subsequently in the boundary layer are associated with large-scale subsidence of ozone-rich air masses from the upper troposphere under anticyclonic conditions while the lowest ozone concentrations are associated with low pressure conditions inducing uplifting of boundary-layer air, poor in ozone and rich in relative humidity, to the lower troposphere. Also, during the 7% highest ozone days at the 0-1.5km layer over Cairo, very high ozone concentrations of about 80 ppb on average are observed from the surface up to 4-5 km altitude. During the highest ozone days over both airports for the 1.5-5km layer and over Cairo over the 0-1.5km layer, there are extended regions of strong subsidence in the eastern Mediterranean but also in eastern and northern Europe and over these regions the atmosphere is dryer than average. The results of this study will be used within the framework of the MACC project. References Kalabokas, P. D., Cammas, J.-P., Thouret, V., Volz-Thomas, A., Boulanger, D. and Repapis C.C. 2013. Examination of the atmospheric conditions associated with high and low summer ozone levels in the lower troposphere over the eastern Mediterranean. Atmos. Chem. Phys. 13, 10339-10352. DOI: http://dx.doi.org/10.5194/acp-13-10339-2013 Kalabokas P. D., Thouret V., Cammas J.-P., Volz-thomas A., Boulanger D., Repapis C.C., 2015. The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case), Tellus B, 67, 27853, http://dx.doi.org/10.3402/tellusb.v67.27853.

The Response of Tropical Tropospheric Ozone to ENSO

NASA Technical Reports Server (NTRS)

Oman, L. D.; Ziemke, J. R.; Douglass, A. R.; Waugh, D. W.; Lang, C.; Rodriguez, J. M.; Nielsen, J. E.

2011-01-01

We have successfully reproduced the Ozone ENSO Index (OEI) in the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) forced by observed sea surface temperatures over a 25-year period. The vertical ozone response to ENSO is consistent with changes in the Walker circulation. We derive the sensitivity of simulated ozone to ENSO variations using linear regression analysis. The western Pacific and Indian Ocean region shows similar positive ozone sensitivities from the surface to the upper troposphere, in response to positive anomalies in the Nino 3.4 Index. The eastern and central Pacific region shows negative sensitivities with the largest sensitivity in the upper troposphere. This vertical response compares well with that derived from SHADOZ ozonesondes in each region. The OEI reveals a response of tropospheric ozone to circulation change that is nearly independent of changes in emissions and thus it is potentially useful in chemistry-climate model evaluation.

Measurement, modeling, and analysis of nonmethane hydrocarbons and ozone in the southeast United States national parks

NASA Astrophysics Data System (ADS)

Kang, Daiwen

In this research, the sources, distributions, transport, ozone formation potential, and biogenic emissions of VOCs are investigated focusing on three Southeast United States National Parks: Shenandoah National Park, Big Meadows site (SHEN), Great Smoky Mountains National Park at Cove Mountain (GRSM) and Mammoth Cave National Park (MACA). A detailed modeling analysis is conducted using the Multiscale Air Quality SImulation Platform (MAQSIP) focusing on nonmethane hydrocarbons and ozone characterized by high O3 surface concentrations. Nine emissions perturbation using the Multiscale Air Quality SImulation Platform (MAQSIP) focusing on nonmethane hydrocarbons and ozone characterized by high O 3 surface concentrations. In the observation-based analysis, source classification techniques based on correlation coefficient, chemical reactivity, and certain ratios were developed and applied to the data set. Anthropogenic VOCs from automobile exhaust dominate at Mammoth Cave National Park, and at Cove Mountain, Great Smoky Mountains National Park, while at Big Meadows, Shenandoah National Park, the source composition is complex and changed from 1995 to 1996. The dependence of isoprene concentrations on ambient temperatures is investigated, and similar regressional relationships are obtained for all three monitoring locations. Propylene-equivalent concentrations are calculated to account for differences in reaction rates between the OH and individual hydrocarbons, and to thereby estimate their relative contributions to ozone formation. Isoprene fluxes were also estimated for all these rural areas. Model predictions (base scenario) tend to give lower daily maximum O 3 concentrations than observations by 10 to 30%. Model predicted concentrations of lumped paraffin compounds are of the same order of magnitude as the observed values, while the observed concentrations for other species (isoprene, ethene, surrogate olefin, surrogate toluene, and surrogate xylene) are usually an order of magnitude higher than the predictions. Detailed sensitivity and process analyses in terms of ozone and VOC scenarios including the base scenario are designed and utilized in the model simulations. Model predictions are compared with the observed values at the three locations for the same time period. Detailed sensitivity and process analyses in terms of ozone and VOC budgets, and relative importance of various VOCs species are provided. (Abstract shortened by UMI.)

Description of the surface water filtration and ozone treatment system at the Northeast Fishery Center

USDA-ARS?s Scientific Manuscript database

A water filtration and ozone disinfection system was installed at the U.S. Fish and Wildlife Service's Northeast Fishery Center in Lamar, Pennsylvania to treat a surface water supply that is used to culture sensitive and endangered fish. The treatment system first passes the surface water through dr...

Anthropogenic changes in the surface all-sky UV-B radiation through 1850-2005 simulated by an Earth system model

NASA Astrophysics Data System (ADS)

Watanabe, S.; Takemura, T.; Sudo, K.; Yokohata, T.; Kawase, H.

2012-06-01

The historical anthropogenic change in the surface all-sky UV-B (solar ultraviolet: 280-315 nm) radiation through 1850-2005 is evaluated using an Earth system model. Responses of UV-B dose to anthropogenic changes in ozone and aerosols are separately evaluated using a series of historical simulations including/excluding these changes. Increases in these air pollutants cause reductions in UV-B transmittance, which occur gradually/rapidly before/after 1950 in and downwind of industrial and deforestation regions. Furthermore, changes in ozone transport in the lower stratosphere, which is induced by increasing greenhouse gas concentrations, increase ozone concentration in the extratropical upper troposphere and lower stratosphere. These transient changes work to decrease the amount of UV-B reaching the Earth's surface, counteracting the well-known effect increasing UV-B due to stratospheric ozone depletion, which developed rapidly after ca. 1980. As a consequence, the surface UV-B radiation change between 1850 and 2000 is negative in the tropics and NH extratropics and positive in the SH extratropics. Comparing the contributions of ozone and aerosol changes to the UV-B change, the transient change in ozone absorption of UV-B mainly determines the total change in the surface UV-B radiation at most locations. On the other hand, the aerosol direct and indirect effects on UV-B play an equally important role to that of ozone in the NH mid-latitudes and tropics. A typical example is East Asia (25° N-60° N and 120° E-150° E), where the effect of aerosols (ca. 70%) dominates the total UV-B change.

Anthropogenic changes in the surface all-sky UV-B radiation through 1850-2005 simulated by an Earth system model

NASA Astrophysics Data System (ADS)

Watanabe, S.; Takemura, T.; Sudo, K.; Yokohata, T.; Kawase, H.

2012-02-01

The historical anthropogenic change in the surface all-sky UV-B (solar ultraviolet: 280-315 nm) radiation through 1850-2005 is evaluated using an Earth system model. Responses of UV-B dose to anthropogenic changes in ozone and aerosols are separately evaluated using a series of historical simulations including/excluding these changes. Increases in these air pollutants cause reductions in UV-B transmittance, which occur gradually/rapidly before/after 1950 in and downwind of industrial and deforestation regions. Furthermore, changes in ozone transport in the lower stratosphere, which is induced by increasing greenhouse gas concentrations, increase ozone concentration in the extratropical upper troposphere and lower stratosphere. These transient changes work to decrease the amount of UV-B reaching the Earth's surface, counteracting the well-known effect increasing UV-B due to stratospheric ozone depletion, which developed rapidly after ca. 1980. As a consequence, the surface all-sky UV-B radiation change between 1850 and 2000 is negative in the tropics and NH extratropics and positive in the SH extratropics. Comparing the contributions of ozone and aerosol changes to the UV-B change, the transient change in ozone absorption of UV-B mainly determines the total change in the surface all-sky UV-B radiation at most locations. On the other hand, the aerosol direct and indirect effects on UV-B play an equally important role to that of ozone in the NH mid-latitudes and tropics. A typical example is East Asia (25° N-60° N and 120° E-150° E), where the effect of aerosols (ca. 70%) dominates the total UV-B change.

Factors affecting ozone removal rates in a simulated aircraft cabin environment

NASA Astrophysics Data System (ADS)

Tamás, Gyöngyi; Weschler, Charles J.; Bakó-Biró, Zsolt; Wyon, David P.; Strøm-Tejsen, Peter

Ozone concentrations were measured concurrently inside a simulated aircraft cabin and in the airstream providing ventilation air to the cabin. Ozone decay rates were also measured after cessation of ozone injection into the supply airstream. By systematically varying the presence or absence of people, soiled T-shirts, aircraft seats and a used HEPA filter, we have been able in the course of 24 experiments to isolate the contributions of these and other factors to the removal of ozone from the cabin air. In the case of this simulated aircraft, people were responsible for almost 60% of the ozone removal occurring within the cabin and recirculation system; respiration can only have been responsible for about 4% of this removal. The aircraft seats removed about 25% of the ozone; the loaded HEPA filter, 7%; and the other surfaces, 10%. A T-shirt that had been slept in overnight removed roughly 70% as much ozone as a person, indicating the importance of skin oils in ozone removal. The presence of the used HEPA filter in the recirculated airstream reduced the perceived air quality. Over a 5-h period, the overall ozone removal rate by cabin surfaces decreased at ˜3% h -1. With people present, the measured ratio of ozone's concentration in the cabin versus that outside the cabin was 0.15-0.21, smaller than levels reported in the literature. The results reinforce the conclusion that the optimal way to reduce people's exposure to both ozone and ozone oxidation products is to efficiently remove ozone from the air supply system of an aircraft.

Feedbacks between Climate and Fire Emissions

DTIC Science & Technology

2011-11-29

CH4 2. Direct emission of short-lived climate forcers - Black Carbon - Particulate organic matter 3. Production of tropospheric ozone and secondary... tropospheric ozone and secondary organic particulate matter 4. Changes in land surface properties - Black carbon on snow - Albedo Radiative Forcing of Black...lived  climate forcers:  particles 3.  Ozone   production 4. Change in  surface properties Fires Impacts on the Climate System 1. Emission of long lived

Probabilistic Forecasting of Surface Ozone with a Novel Statistical Approach

NASA Technical Reports Server (NTRS)

Balashov, Nikolay V.; Thompson, Anne M.; Young, George S.

2017-01-01

The recent change in the Environmental Protection Agency's surface ozone regulation, lowering the surface ozone daily maximum 8-h average (MDA8) exceedance threshold from 75 to 70 ppbv, poses significant challenges to U.S. air quality (AQ) forecasters responsible for ozone MDA8 forecasts. The forecasters, supplied by only a few AQ model products, end up relying heavily on self-developed tools. To help U.S. AQ forecasters, this study explores a surface ozone MDA8 forecasting tool that is based solely on statistical methods and standard meteorological variables from the numerical weather prediction (NWP) models. The model combines the self-organizing map (SOM), which is a clustering technique, with a step wise weighted quadratic regression using meteorological variables as predictors for ozone MDA8. The SOM method identifies different weather regimes, to distinguish between various modes of ozone variability, and groups them according to similarity. In this way, when a regression is developed for a specific regime, data from the other regimes are also used, with weights that are based on their similarity to this specific regime. This approach, regression in SOM (REGiS), yields a distinct model for each regime taking into account both the training cases for that regime and other similar training cases. To produce probabilistic MDA8 ozone forecasts, REGiS weighs and combines all of the developed regression models on the basis of the weather patterns predicted by an NWP model. REGiS is evaluated over the San Joaquin Valley in California and the northeastern plains of Colorado. The results suggest that the model performs best when trained and adjusted separately for an individual AQ station and its corresponding meteorological site.

Degradation of sulfamethoxazole using ozone and chlorine dioxide - Compound-specific stable isotope analysis, transformation product analysis and mechanistic aspects.

PubMed

Willach, Sarah; Lutze, Holger V; Eckey, Kevin; Löppenberg, Katja; Lüling, Michelle; Terhalle, Jens; Wolbert, Jens-Benjamin; Jochmann, Maik A; Karst, Uwe; Schmidt, Torsten C

2017-10-01

The sulfonamide antibiotic sulfamethoxazole (SMX) is a widely detected micropollutant in surface and groundwaters. Oxidative treatment with e.g. ozone or chlorine dioxide is regularly applied for disinfection purposes at the same time exhibiting a high potential for removal of micropollutants. Especially for nitrogen containing compounds such as SMX, the related reaction mechanisms are largely unknown. In this study, we systematically investigated reaction stoichiometry, product formation and reaction mechanisms in reactions of SMX with ozone and chlorine dioxide. To this end, the neutral and anionic SMX species, which may occur at typical pH-values of water treatment were studied. Two moles of chlorine dioxide and approximately three moles of ozone were consumed per mole SMX degraded. Oxidation of SMX with ozone and chlorine dioxide leads in both cases to six major transformation products (TPs) as revealed by high-resolution mass spectrometry (HRMS). Tentatively formulated TP structures from other studies could partly be confirmed by compound-specific stable isotope analysis (CSIA). However, for one TP, a hydroxylated SMX, it was not possible by HRMS alone to identify whether hydroxylation occurred at the aromatic ring, as suggested in literature before, or at the anilinic nitrogen. By means of CSIA and an analytical standard it was possible to identify sulfamethoxazole hydroxylamine unequivocally as one of the TPs of the reaction of SMX with ozone as well as with chlorine dioxide. H-abstraction and electron transfer at the anilinic nitrogen are suggested as likely initial reactions of ozone and chlorine dioxide, respectively, leading to its formation. Oxidation of anionic SMX with ozone did not show any significant isotopic fractionation whereas the other reactions studied resulted in a significant carbon isotope fractionation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Global ozone and air quality: a multi-model assessment of risks to human health and crops

NASA Astrophysics Data System (ADS)

Ellingsen, K.; Gauss, M.; van Dingenen, R.; Dentener, F. J.; Emberson, L.; Fiore, A. M.; Schultz, M. G.; Stevenson, D. S.; Ashmore, M. R.; Atherton, C. S.; Bergmann, D. J.; Bey, I.; Butler, T.; Drevet, J.; Eskes, H.; Hauglustaine, D. A.; Isaksen, I. S. A.; Horowitz, L. W.; Krol, M.; Lamarque, J. F.; Lawrence, M. G.; van Noije, T.; Pyle, J.; Rast, S.; Rodriguez, J.; Savage, N.; Strahan, S.; Sudo, K.; Szopa, S.; Wild, O.

2008-02-01

Within ACCENT, a European Network of Excellence, eighteen atmospheric models from the U.S., Europe, and Japan calculated present (2000) and future (2030) concentrations of ozone at the Earth's surface with hourly temporal resolution. Comparison of model results with surface ozone measurements in 14 world regions indicates that levels and seasonality of surface ozone in North America and Europe are characterized well by global models, with annual average biases typically within 5-10 nmol/mol. However, comparison with rather sparse observations over some regions suggest that most models overestimate annual ozone by 15-20 nmol/mol in some locations. Two scenarios from the International Institute for Applied Systems Analysis (IIASA) and one from the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) have been implemented in the models. This study focuses on changes in near-surface ozone and their effects on human health and vegetation. Different indices and air quality standards are used to characterise air quality. We show that often the calculated changes in the different indices are closely inter-related. Indices using lower thresholds are more consistent between the models, and are recommended for global model analysis. Our analysis indicates that currently about two-thirds of the regions considered do not meet health air quality standards, whereas only 2-4 regions remain below the threshold. Calculated air quality exceedances show moderate deterioration by 2030 if current emissions legislation is followed and slight improvements if current emissions reduction technology is used optimally. For the "business as usual" scenario severe air quality problems are predicted. We show that model simulations of air quality indices are particularly sensitive to how well ozone is represented, and improved accuracy is needed for future projections. Additional measurements are needed to allow a more quantitative assessment of the risks to human health and vegetation from changing levels of surface ozone.

Preliminary Analysis of Ozonesonde Data from Houston, TX as Part of INTEX-A, July - August 2004

NASA Astrophysics Data System (ADS)

Hersey, S.; Morris, G.; Fraser, M.; Holmes, C.; Thompson, A.; Kuscera, T.; Witte, J.

2004-12-01

The Houston area is well-known for its frequent levels of high ozone pollution. The extent of the pollution in Houston has important direct and indirect consequences for the local population, ranging from the cancelling of recess to increased rates of asthma to threats of fines and loss of transportation dollars for failure to comply with EPA standards. Despite these consequences, the Houston area has no established program to monitor ozone concentrations at any altitude in the atmosphere but the surface. During the period July 8 - August 12, we launched 25 ozonesondes that yielded data on the vertical distribution of ozone over the city of Houston as part of INTEX-A and a study sponsored by the Shell Center for Sustainable Development at Rice University. Combining ozonesonde data from Houston with a trajectory model from NASA Goddard provides a powerful approach to interpreting the data, including insight into local and remote contributions to Houston's ozone pollution. Analysis of our data show (1) the impact of remote wild fires on ozone levels above Houston, (2) the amount of ozone that develops over Houston in the course of one day, and (3) the extent of vertical mixing of Houston's ozone pollution, a factor in transport to areas downwind of the city.

The Response of Lower Atmospheric Ozone to ENSO in Aura Measurements and a Chemistry-Climate Simulation

NASA Technical Reports Server (NTRS)

Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Rodriquez, J. M.; Waugh, D. W.; Nielsen, J. E.

2012-01-01

The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere. Recent work has revealed an ENSO-induced wave-1 anomaly in observed tropical tropospheric column ozone. This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this feature using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years. An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region. We will show composition sensitivity in observations from NASA s Aura satellite Microwave Limb Sounder (MLS) and the Tropospheric Emissions Spectrometer (TES) and a simulation to provide insight into the vertical structure of these ENSO-induced ozone changes. The ozone changes due to the Quasi-Biennial Oscillation (QBO) in the extra-polar upper troposphere and lower stratosphere in MLS measurements will also be discussed.

A Bayesian model for quantifying the change in mortality associated with future ozone exposures under climate change.

PubMed

Alexeeff, Stacey E; Pfister, Gabriele G; Nychka, Doug

2016-03-01

Climate change is expected to have many impacts on the environment, including changes in ozone concentrations at the surface level. A key public health concern is the potential increase in ozone-related summertime mortality if surface ozone concentrations rise in response to climate change. Although ozone formation depends partly on summertime weather, which exhibits considerable inter-annual variability, previous health impact studies have not incorporated the variability of ozone into their prediction models. A major source of uncertainty in the health impacts is the variability of the modeled ozone concentrations. We propose a Bayesian model and Monte Carlo estimation method for quantifying health effects of future ozone. An advantage of this approach is that we include the uncertainty in both the health effect association and the modeled ozone concentrations. Using our proposed approach, we quantify the expected change in ozone-related summertime mortality in the contiguous United States between 2000 and 2050 under a changing climate. The mortality estimates show regional patterns in the expected degree of impact. We also illustrate the results when using a common technique in previous work that averages ozone to reduce the size of the data, and contrast these findings with our own. Our analysis yields more realistic inferences, providing clearer interpretation for decision making regarding the impacts of climate change. © 2015, The International Biometric Society.

Atmospheric carbon dioxide and chlorofluoromethanes - Combined effects on stratospheric ozone, temperature, and surface temperature

NASA Technical Reports Server (NTRS)

Callis, L. B.; Natarajan, M.

1981-01-01

The effects of combined CO2 and CFCl3 and CF2Cl2 time-dependent scenarios on atmospheric O3 and temperature are described; the steady-state levels of O3 and surface temperature, to which the chlorofluoromethane scenario tends in the presence of twice and four time ambient CO2, are examined; and surface temperature changes, caused by the combined effects, are established. A description of the model and of the experiments is presented. Results indicate that (1) the total ozone time history is significantly different from that due to the chlorofluoromethane alone; (2) a local ozone minimum occurs in the upper stratosphere about 45 years from the present with a subsequent ozone increase, then decline; and (3) steady-state solutions indicate that tropospheric temperature and water vapor increases, associated with increased infrared opacity, cause significant changes in tropospheric ozone levels for 2 x CO2 and 4 x CO2, without the addition of chlorofluoromethanes.

Ozone destruction through heterogeneous chemistry following the eruption of El Chichon

NASA Technical Reports Server (NTRS)

Hofmann, David J.; Solomon, Susan

1989-01-01

The results of ozone observations at northern midlatitudes in late 1982 through 1983, following the eruption of El Chichon are discussed, together with the observations of other trace gases which may be linked to possible variations in ozone chemistry. These results are related to the in situ aerosol observations following the El Chicon eruption, with particular attention given to data relevant to heterogeneous reactions, such as the aerosol surface area and weight percent H2SO4. It is shown that, at midlatitudes, the observed volcanic-particle surface area reached a maximum of about 50 sq microns/cu m (above a typical background value of about 0.75) at an altitude of 18-20 km in early 1983; this enhancement of surface area is about the same as that encountered in stratospheric clouds in the Antarctic, suggesting a possible basis for ozone depletion through heterogeneous chemistry. The fraction of ozone reduction that may have occurred as a result of heterogeneous chemicl effects is estimated.

CAMx Ozone Source Attribution in the Eastern United States using Guidance from Observations during DISCOVER-AQ Maryland

PubMed Central

Goldberg, Daniel L.; Vinciguerra, Timothy P.; Anderson, Daniel C.; Hembeck, Linda; Canty, Timothy P.; Ehrman, Sheryl H.; Martins, Douglas K.; Stauffer, Ryan M.; Thompson, Anne M.; Salawitch, Ross J.; Dickerson, Russell R.

2018-01-01

A Comprehensive Air-Quality Model with Extensions (CAMx) version 6.10 simulation was assessed through comparison with data acquired during NASA’s 2011 DISCOVER-AQ Maryland field campaign. Comparisons for the baseline simulation (CB05 chemistry, EPA 2011 National Emissions Inventory) show a model overestimate of NOy by +86.2% and an underestimate of HCHO by −28.3%. We present a new model framework (CB6r2 chemistry, MEGAN v2.1 biogenic emissions, 50% reduction in mobile NOx, enhanced representation of isoprene nitrates) that better matches observations. The new model framework attributes 31.4% more surface ozone in Maryland to electric generating units (EGUs) and 34.6% less ozone to on-road mobile sources. Surface ozone becomes more NOx-limited throughout the eastern United States compared to the baseline simulation. The baseline model therefore likely underestimates the effectiveness of anthropogenic NOx reductions as well as the current contribution of EGUs to surface ozone. PMID:29618849

CAMx Ozone Source Attribution in the Eastern United States using Guidance from Observations during DISCOVER-AQ Maryland.

PubMed

Goldberg, Daniel L; Vinciguerra, Timothy P; Anderson, Daniel C; Hembeck, Linda; Canty, Timothy P; Ehrman, Sheryl H; Martins, Douglas K; Stauffer, Ryan M; Thompson, Anne M; Salawitch, Ross J; Dickerson, Russell R

2016-03-16

A Comprehensive Air-Quality Model with Extensions (CAMx) version 6.10 simulation was assessed through comparison with data acquired during NASA's 2011 DISCOVER-AQ Maryland field campaign. Comparisons for the baseline simulation (CB05 chemistry, EPA 2011 National Emissions Inventory) show a model overestimate of NO y by +86.2% and an underestimate of HCHO by -28.3%. We present a new model framework (CB6r2 chemistry, MEGAN v2.1 biogenic emissions, 50% reduction in mobile NO x , enhanced representation of isoprene nitrates) that better matches observations. The new model framework attributes 31.4% more surface ozone in Maryland to electric generating units (EGUs) and 34.6% less ozone to on-road mobile sources. Surface ozone becomes more NO x -limited throughout the eastern United States compared to the baseline simulation. The baseline model therefore likely underestimates the effectiveness of anthropogenic NO x reductions as well as the current contribution of EGUs to surface ozone.

Does ozone enhance the remineralizing potential of nanohydroxyapatite on artificially demineralized enamel? A laser induced fluorescence study

NASA Astrophysics Data System (ADS)

Srinivasan, Samuelraj; Prabhu, Vijendra; Chandra, Subhash; Koshy, Shalini; Acharya, Shashidhar; Mahato, Krishna K.

2014-02-01

The present era of minimal invasive dentistry emphasizes the early detection and remineralization of initial enamel caries. Ozone has been shown to reverse the initial demineralization before the integrity of the enamel surface is lost. Nano-hydroxyapatite is a proven remineralizing agent for early enamel caries. In the present study, the effect of ozone in enhancing the remineralizing potential of nano-hydroxyapatite on artificially demineralized enamel was investigated using laser induced fluorescence. Thirty five sound human premolars were collected from healthy subjects undergoing orthodontic treatment. Fluorescence was recorded by exciting the mesial surfaces using 325 nm He-Cd laser with 2 mW power. Tooth specimens were subjected to demineralization to create initial enamel caries. Following which the specimens were divided into three groups, i.e ozone (ozonated water for 2 min), without ozone and artificial saliva. Remineralization regimen was followed for 3 weeks. The fluorescence spectra of the specimens were recorded from all the three experimental groups at baseline, after demineralization and remineralization. The average spectrum for each experimental group was used for statistical analysis. Fluorescence intensities of Ozone treated specimens following remineralization were higher than that of artificial saliva, and this difference was found to be statistically significant (P<0.0001). In a nutshell, ozone enhanced the remineralizing potential of nanohydroxyapatite, and laser induced fluorescence was found to be effective in assessing the surface mineral changes in enamel. Ozone can be considered an effective agent in reversing the initial enamel caries there by preventing the tooth from entering into the repetitive restorative cycle.

Comparative Analysis of the Surface Ozone Regime Over Russia and Europe

NASA Astrophysics Data System (ADS)

Kuznetsov, G. I.; Tarasova, O. A.; Elansky, N. F.; Beloglazov, M. I.

2004-05-01

The data of the measurements of the surface ozone concentration (SOC) at several Russian cites, in TROICA expeditions, data of EMEP network as well as the results of LOTOS model application were used to compare the main characteristics of ozone spatial and temporal variability over Russia and Europe. To carry out this investigation the number of new methods of data analysis were developed and applied. Their complex application gave us possibility to separate clearly the contribution of photochemical processes having mainly periodical component (daily and seasonal). Hence more attention could be paid to the dynamical mechanism impacting SOC regime, their spatial and temporal variability including trends estimation. Spectral windowing application to the filtered database of EMEP network showed that among the different processes providing annual and shorter variability the main part (about 40% of dispersion) is governed by local and synoptical scale processes in the range of 2-7 days. At the same time the spatial distribution of these percentage contribution is non-uniform over Europe. One of the important mechanisms providing this type of variability as well as the longer ones is air transport. To study the impact of air transport the correlation fields were calculated for the transport indices using 2D NILU trajectories and SOC at EMEP network. They showed that at the Eastern border of Europe the growth of the westerlies provides not the decrease but the growth of observed SOC. This approach was use to study the features of the zonal and meridianal transport, its seasonal characteristics and annual variability. Moreover at Kislovodsk High Mountain Station the changes of the transport patters can partly explain even observed trend of SOC. Comparison of the regime at the different locations using TROICA data shows that in the most of Russian cities ozone destruction is observed. The generation of the surface ozone is only possible in the cases of combination of natural and anthropogenic emissions (like forest fires episodes in Moscow region in summer 2002). The spatial structure of the surface ozone over the European Russia was obtained with the application of LOTOS model (TNO) evaluated for 1997. It showed much more uniformity of the SOC fields over Russia with the high concentrations in rural regions in comparison with industrial ones. This conclusion is in a good agreement with the measurements of TROICA expedition. The work is carried out under the support of INTAS grant 01-0016 and RFBR 03-05-64712.

A general circulation model study of the climatic effect of observed stratospheric ozone depletion between 1980 and 1990

NASA Technical Reports Server (NTRS)

Dudek, Michael P.; Wang, Wei-Chyung; Liang, Xin-Zhong; Li, Zhu

1994-01-01

The total ozone mapping spectrometer (TOMS) and stratospheric aerosol and gas experiment (SAGE) measurements show a significant reduction in the stratospheric ozone over the middle and high latitudes of both hemispheres between the years 1979 and 1991 (WMO, 1992). This change in ozone will effect both the solar and longwave radiation with climate implications. However, recent studies (Ramaswamy et al., 1992; WMO, 1992) indicate that the net effect depends not only on latitudes and seasons, but also on the response of the lower stratospheric temperature. In this study we use a general circulation model (GCM) to calculate the climatic effect due to stratospheric ozone depletion and compare the effect with that due to observed increases of trace gases CO2, CH4, N2O, and CFC's for the period 1980-1990. In the simulations, we use the observed changes in ozone derived from the TOMS data. The GCM used is a version of the NCAR community climate model referenced in Wang et al. (1991). For the present study we run the model in perpetual January and perpetual July modes in which the incoming solar radiation and climatological sea surface temperatures are held constant.

Seasonal Characteristics of Widespread Ozone Pollution in China and India: Current Model Capabilities and Source Attributions

NASA Astrophysics Data System (ADS)

Gao, M.; Song, S.; Beig, G.; Zhang, H.; Hu, J.; Ying, Q.; McElroy, M. B.

2017-12-01

Fast urbanization and industrialization in China and India have led to severe ozone pollution, threatening public health in these densely populated countries. We show the spatial and seasonal characteristics of ozone concentrations using nation-wide observations for these two countries in 2013. We used the Weather Research and Forecasting model coupled to chemistry (WRF-Chem) to conduct one-year simulations and to evaluate how current models capture the important photochemical processes using the exhaustive available datasets in China and India, including surface measurements, ozonesonde data and satellite retrievals. We also employed the factor separation approach to distinguish the contributions of different sectors to ozone during different seasons. The back trajectory model FLEXPART was applied to investigate the role of transport in highly polluted regions (e.g., North China Plain, Yangtze River delta, and Pearl River Delta) during different seasons. Preliminary results indicate that the WRF-Chem model provides a satisfactory representation of the temporal and spatial variations of ozone for both China and India. The factor separation approach offers valuable insights into relevant sources of ozone for both countries providing valuable guidance for policy options designed to mitigate the related problem.

Industrial wastewater treatment in a new gas-induced ozone reactor.

PubMed

Lin, Sheng H; Wang, Ching H

2003-03-17

The present work was to investigate industrial wastewater treatment by ozonation in a new gas-induced reactor in conjunction with chemical coagulation pretreatment. The reactor was specifically designed in a fashion that gas induction was created on the liquid surface by the high-speed action of an impeller turbine inside a draft tube to maximize the ozone gas utilization. A new design feature of the present reactor system was a fixed granular activated carbon (GAC) bed packed in a circular compartment between the reactor wall and the shaft tube. The fixed GAC bed provided additional adsorption and catalytic degradation of organic pollutants. Combination of the fixed GAC bed and ozonation results in enhanced oxidation of organic pollutants. In addition to enhanced pollutant oxidation, ozonation was found to provide in situ GAC regeneration that was considered crucial in the present reaction system. Kinetic investigations were also made using a proposed complex kinetic model to elucidate the possible oxidation reaction mechanisms of the present gas-induced ozonation system. As a complementary measure, chemical coagulation pretreatment was found able to achieve up to 50% COD and 85% ADMI removal. Experimental tests were conducted to identify its optimum operating conditions. Copyright 2003 Elsevier Science B.V.

An Overview of the Uintah Basin Winter Ozone Study Intensives: 2012, 2013, and 2014

NASA Astrophysics Data System (ADS)

Roberts, J. M.; Edwards, P. M.; Brown, S. S.; Ahmadov, R.; Bates, T. S.; De Gouw, J. A.; Gilman, J.; Graus, M.; Helmig, D.; Koss, A.; Langford, A. O.; Lefer, B. L.; Lerner, B. M.; Li, R.; Li, S. M.; Liggio, J.; McKeen, S. A.; McLaren, R.; Parrish, D. D.; Quinn, P.; Senff, C. J.; Stutz, J.; Thompson, C. R.; Tsai, J. Y.; Veres, P. R.; Washenfelder, R. A.; Warneke, C.; Wild, R. J.; Young, C.; Yuan, B.

2014-12-01

Ground level ozone frequently exceeds the National Ambient Air Quality Standard in the Uintah Basin in northeastern Utah during the winter season. The basin is home to some of the most intensive oil and gas production in the region, activities that have been accelerated by new technologies in that industry. High ozone episodes are coincident with the presence of snow and "cold pool" conditions during which a stable shallow boundary layer persists for periods of up to 10 days. Local emissions of NOx and VOCs build up within this layer, but the sources of radicals that initiate the photochemistry have been unclear since low photolysis rates and water vapor make the traditional channel, ozone photolysis, quite inefficient. Intensive studies over the past 3 winter seasons have shown that unconventional radical sources; primarily carbonyls, and to a lesser extent nitryl chloride and nitrous acid, are responsible for radical production in this environment. The role of snow cover is to restrict vertical mixing, enhance photolysis rates through increased albedo, and reduce ozone deposition. The uptake and production of photo-labile species on the snow surface were observed, but appear to have only minor influences on the ozone photochemistry.

Chemical effect on ozone deposition over seawater

EPA Science Inventory

Surface layer resistance plays an important role in determining ozone deposition velocity over seawater. Recent studies suggest that surface layer resistance over sea-water is influenced by wind-speed and chemical interaction at the air-water interface. Here, we investigate the e...

Study of thickness and uniformity of oxide passivation with DI-O3 on silicon substrate for electronic and photonic applications

NASA Astrophysics Data System (ADS)

Sharma, Mamta; Hazra, Purnima; Singh, Satyendra Kumar

2018-05-01

Since the beginning of semiconductor fabrication technology evolution, clean and passivated substrate surface is one of the prime requirements for fabrication of Electronic and optoelectronic device fabrication. However, as the scale of silicon circuits and device architectures are continuously decreased from micrometer to nanometer (from VLSI to ULSI technology), the cleaning methods to achieve better wafer surface qualities has raised research interests. The development of controlled and uniform silicon dioxide is the most effective and reliable way to achieve better wafer surface quality for fabrication of electronic devices. On the other hand, in order to meet the requirement of high environment safety/regulatory standards, the innovation of cleaning technology is also in demand. The controlled silicon dioxide layer formed by oxidant de-ionized ozonated water has better uniformity. As the uniformity of the controlled silicon dioxide layer is improved on the substrate, it enhances the performance of the devices. We can increase the thickness of oxide layer, by increasing the ozone time treatment. We reported first time to measurement of thickness of controlled silicon dioxide layer and obtained the uniform layer for same ozone time.

Indoor air purification by dielectric barrier discharge combined with ionic wind: physical and microbiological investigations

NASA Astrophysics Data System (ADS)

Timmermann, E.; Prehn, F.; Schmidt, M.; Höft, H.; Brandenburg, R.; Kettlitz, M.

2018-04-01

A non-thermal plasma source based on a surface dielectric barrier discharge (DBD) is developed for purification of recirculating air in operating theatres in hospitals. This is a challenging application due to high flow rates, short treatment times and the low threshold for ozone in the ventilated air. Therefore, the surface DBD was enhanced in order to generate an ionic wind, which can deflect and thus, filter out airborne microorganisms. Electrical and gas diagnostics as well as microbiological experiments were performed in a downscaled plasma source under variation of various electrical parameters, but application-oriented airflow velocity and humidity. The dependence of electrical power and ozone concentration as well as charged particles in the plasma treated air on frequency, voltage and relative humidity is presented and discussed. The presence of humidity causes a more conductive dielectric surface and thus a weaker plasma formation, especially at low frequency. The airborne test bacteria, Escherichia coli, showed significant effect to plasma treatment (up to 20% reduction) and to plasma with ionic wind (up to 90% removal); especially a configuration with 70% removal and an accompanying ozone concentration of only 360 ppb is promising for future application.

Chemical Controls of Ozone Dry Deposition to the Sea Surface Microlayer

NASA Astrophysics Data System (ADS)

Carpenter, L.; Chance, R.; Tinel, L.; Saint, A.; Sherwen, T.; Loades, D.; Evans, M. J.; Boxhall, P.; Hamilton, J.; Stolle, C.; Wurl, O.; Ribas-Ribas, M.; Pereira, R.

2017-12-01

Oceanic dry deposition of atmospheric ozone (O3) is both the largest and most uncertain O3 depositional sink, and is widely acknowledged to be controlled largely by chemical reactions in the sea surface microlayer (SML) involving iodide (I-) and dissolved organic material (DOM). These reactions not only determine how quickly O3 can be removed from the atmosphere, but also result in emissions of trace gases including volatile organic compounds and may constitute a source of secondary organic aerosols to the marine atmosphere. Iodide concentrations at the sea surface vary by approximately an order of magnitude spatially, leading to more than fivefold variation in ozone deposition velocities (and volatile iodine fluxes). Sea-surface temperature is a reasonable predictor of [I-], however two recent parameterisations for surface I- differ by a factor of two at low latitudes. The nature and reactivity of marine DOM to O3 is almost completely unknown, although studies have suggested approximately equivalent chemical control of I- and DOM on ozone deposition. Here we present substantial new measurements of oceanic I- in both bulk seawater and the overlying SML, and show improved estimates of the global sea surface iodide distribution. We also present analyses of water-soluble DOM isolated from the SML and bulk seawater, and corresponding laboratory studies of ozone uptake to bulk and SML seawater, with the aim of characterizing the reactivity of O3 towards marine DOM.

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

PubMed

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 at El Arenosillo and Valverde stations remains very uniformed until 20:00 UTC. These levels could be due to the photochemical production in situ and also to the horizontal and vertical ozone transport at El Arenosillo from the reservoir layers in the sea and in the case of Valverde, the horizontal transport, thanks to the marine breeze. Finally, the data have been evaluated relative to the thresholds defined in the European Ozone Directive. The threshold to protect human health has been exceeded during the spring and summer months mainly at El Arenosillo and Valverde. The vegetation threshold has also been frequently exceeded, ranging from 131 days at Cartaya up to 266 days at Valverde. The results in the seasonal and daily variations demonstrate that El Arenosillo and Valverde stations show higher ozone concentrations than Cartaya and Huelva during the spring and summer months. Under meteorological conditions characterized by land-sea breeze circulation, the daytime sea breeze transports the emissions from urban and industrial sources in the SW further inland. Under this condition, the area located downwind to the NE is affected very easily by high ozone concentrations, which is the case for the Valverde station. Nevertheless, according to this circulation model, the El Arenosillo station located at the coast SE from these sources is not directly affected by their emissions. The ozone concentrations observed at El Arenosillo can be explained by the ozone residual layer over the sea, similar to other coastal sites in the Mediterranean basin. The temporal variations of the ozone concentrations have been studied at four measurement sites in the southwest of the Iberian Peninsula. The results obtained point out that industrial and urban emissions combined with specific meteorological conditions in spring and summer cause high ozone levels which exceed the recommended threshold limits and could affect the vegetation and human health in this area. This work is the first investigation related to surface ozone in this region; therefore, the results obtained may be a useful tool to air quality managers and policy-makers to apply possible air control strategies towards a reduction of ozone exceedances and the impact on human health and vegetation. Due to the levels, variability and underlying boundary layer dynamics, it is necessary to extend this research in this geographical area with the purpose of improving the understanding of photochemical air pollution in the Western Mediterranean Basin and in the south of the Iberian Peninsula.

Effect of ozonation on the removal of cyanobacterial toxins during drinking water treatment.

PubMed Central

Hoeger, Stefan J; Dietrich, Daniel R; Hitzfeld, Bettina C

2002-01-01

Water treatment plants faced with toxic cyanobacteria have to be able to remove cyanotoxins from raw water. In this study we investigated the efficacy of ozonation coupled with various filtration steps under different cyanobacterial bloom conditions. Cyanobacteria were ozonated in a laboratory-scale batch reactor modeled on a system used by a modern waterworks, with subsequent activated carbon and sand filtration steps. The presence of cyanobacterial toxins (microcystins) was determined using the protein phosphatase inhibition assay. We found that ozone concentrations of at least 1.5 mg/L were required to provide enough oxidation potential to destroy the toxin present in 5 X 10(5 )Microcystis aeruginosa cells/mL [total organic carbon (TOC), 1.56 mg/L]. High raw water TOC was shown to reduce the efficiency of free toxin oxidation and destruction. In addition, ozonation of raw waters containing high cyanobacteria cell densities will result in cell lysis and liberation of intracellular toxins. Thus, we emphasize that only regular and simultaneous monitoring of TOC/dissolved organic carbon and cyanobacterial cell densities, in conjunction with online residual O(3) concentration determination and efficient filtration steps, can ensure the provision of safe drinking water from surface waters contaminated with toxic cyanobacterial blooms. PMID:12417484

The Sources and Significance of Stratospheric Water Vapor: Mechanistic Studies from Equator to Pole

NASA Astrophysics Data System (ADS)

Smith, Jessica Birte

It is the future of the stratospheric ozone layer, which protects life at Earth's surface from harmful ultraviolet (UV) radiation, that is the focus of the present work. Fundamental changes in the composition and structure of the stratosphere in response to anthropogenic climate forcing may lead to catastrophic ozone loss under current, and even reduced, stratospheric halogen loading. In particular, the evolution toward a colder, wetter stratosphere, threatens to enhance the heterogeneous conversion of inorganic halogen from its reservoir species to its catalytically active forms, and thus promote in situ ozone loss. Water vapor concentrations control the availability of reactive surface area, which facilitates heterogeneous chemistry. Furthermore, the rates of the key heterogeneous processes are tightly controlled by the ambient humidity. Thus, credible predictions of UV dosage require a quantitative understanding of both the sensitivity of these chemical mechanisms to water vapor concentrations, and an elucidation of the processes controlling stratospheric water vapor concentrations. Toward this end, we present a set of four case studies utilizing high resolution in situ data acquired aboard NASA aircraft during upper atmospheric research missions over the past two decades. 1) We examine the broad scale humidity structure of the upper troposphere and lower stratosphere from the midlatitudes to the tropics, focusing on cirrus formation and dehydration at the cold-point tropical tropopause. The data show evidence for frequent supersaturation in clear air, and sustained supersaturation in the presence of cirrus. These results challenge the strict thermal control of the tropical tropopause. 2) We investigate the likelihood of cirrus-initiated activation of chlorine in the midlatitude lower stratosphere. At midlatitudes the transition from conditions near saturation below the local tropopause to undersaturated air above greatly reduces the probability of heterogeneous activation and in situ ozone loss in this region. 3) We probe the details of heterogeneous processing in the wintertime Arctic vortex, and find that in situ measurements of OH provide incontrovertible evidence for the heterogeneous reaction of HOCl with HCl. This reaction is critical to sustaining catalytically active chlorine and prolonging ozone loss in the springtime vortex. 4) We revisit the topic of midlatitude ozone loss with an emphasis upon the response of ozone in this region to changes in the chemical composition and thermal structure of the lower stratosphere induced by anthropogenic climate change. Specifically, we show evidence for episodic moisture plumes in the overworld stratosphere generated by the rapid evaporation of ice injected into this region by deep convection, and find that these high water vapor plumes have the potential to alter the humidity of the lower stratosphere, and drastically increase the rate of heterogeneous chemistry and in situ ozone loss, given sufficient reactive surface.

The Tropospheric Ozone Assessment Report (TOAR): A community-wide effort to quantify tropospheric ozone in a rapidly changing world

NASA Astrophysics Data System (ADS)

Cooper, O. R.; Schultz, M.; Paoletti, E.; Galbally, I. E.; Naja, M. K.; Tarasick, D. W.; Evans, M. J.; Thompson, A. M.

2017-12-01

Tropospheric ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity. Since 1990 a large portion of the anthropogenic emissions that react in the atmosphere to produce ozone has shifted from North America and Europe to Asia. This rapid shift, coupled with limited ozone monitoring in developing nations, left scientists unable to answer the most basic questions: Which regions of the world have the greatest human and plant exposure to ozone pollution? Is ozone continuing to decline in nations with strong emissions controls? To what extent is ozone increasing in the developing world? How can the atmospheric sciences community facilitate access to the ozone metrics necessary for quantifying ozone's impact on human health and crop/ecosystem productivity? To answer these questions the International Global Atmospheric Chemistry Project (IGAC) initiated the Tropospheric Ozone Assessment Report (TOAR). With over 220 member scientists and air quality specialists from 36 nations, TOAR's mission is to provide the research community with an up-to-date scientific assessment of tropospheric ozone's global distribution and trends from the surface to the tropopause. TOAR has also built the world's largest database of surface ozone observations and generated ozone exposure and dose metrics at thousands of measurement sites around the world, freely accessible for research on the global-scale impact of ozone on climate, human health and crop/ecosystem productivity. Plots of these metrics show the regions of the world with the greatest ozone exposure for humans and crops/ecosystems, at least in areas where observations are available. The results also highlight regions where air quality is improving and where it has degraded. TOAR has also conducted the first intercomparison of tropospheric column ozone from ozonesondes and multiple satellite instruments, which provide similar estimates of the present-day tropospheric ozone burden.

Low temperature ozone oxidation of solid waste surrogates

NASA Astrophysics Data System (ADS)

Nabity, James A.; Lee, Jeffrey M.

2015-09-01

Solid waste management presents a significant challenge to human spaceflight and especially, long-term missions beyond Earth orbit. A six-month mission will generate over 300 kg of solid wastes per crewmember that must be dealt with to eliminate the need for storage and prevent it from becoming a biological hazard to the crew. There are several methods for the treatment of wastes that include oxidation via ozone, incineration, microbial oxidation or pyrolysis and physical methods such as microwave drying and compaction. In recent years, a low temperature oxidation process using ozonated water has been developed for the chemical conversion of organic wastes to CO2 and H2O. Experiments were conducted to evaluate the rate and effectiveness with which ozone oxidized several different waste materials. Increasing the surface area by chopping or shredding the solids into small pieces more than doubled the rate of oxidation. A greater flow of ozone and agitation of the ozonated water system also increased processing rates. Of the materials investigated, plastics have proven the most difficult to oxidize. The processing of plastics above the glass transition temperatures caused the plastics to clump together which reduced the exposed surface area, while processing at lower temperatures reduced surface reaction kinetics.

An analysis of the impacts of global climate and emissions changes on regional tropospheric ozone

NASA Technical Reports Server (NTRS)

John, Kuruvilla; Crist, Kevin C.; Carmichael, Gregory R.

1994-01-01

Many of the synergistic impacts resulting from future changes in emissions as well as changes in ambient temperature, moisture, and UV flux have not been quantified. A three-dimensional regional-scale photo-chemical model (STEM-2) is used in this study to evaluate these perturbations to trace gas cycles over the eastern half of the United States of America. The model was successfully used to simulate a regional-scale ozone episode (base case - June 1984) and four perturbations scenarios - viz., perturbed emissions, temperature, water vapor column, and incoming UV flux cases, and a future scenario (for the year 2034). The impact of these perturbation scenarios on the distribution of ozone and other major pollutants such as SO2 and sulfates were analyzed in detail. The spatial distribution and the concentration of ozone at the surface increased by about 5-15 percent for most cases except for the perturbed water vapor case. The regional scale surface ozone concentration distribution for the year 2034 (future scenario) showed an increase of non-attainment areas. The rural areas of Pennsylvania, West Virginia, and Georgia showed the largest change in the surface ozone field for the futuristic scenario when compared to the base case.

Effect of UV-ozone treatment on poly(dimethylsiloxane) membranes: surface characterization and gas separation performance.

PubMed

Fu, Ywu-Jang; Qui, Hsuan-zhi; Liao, Kuo-Sung; Lue, Shingjiang Jessie; Hu, Chien-Chieh; Lee, Kueir-Rarn; Lai, Juin-Yih

2010-03-16

A thin SiO(x) selective surface layer was formed on a series of cross-linked poly(dimethylsiloxane) (PDMS) membranes by exposure to ultraviolet light at room temperature in the presence of ozone. The conversion of the cross-linked polysiloxane to SiO(x) was monitored by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) microanalysis, contact angle analysis, and atomic force microscopy (AFM). The conversion of the cross-linked polysiloxane to SiO(x) increased with UV-ozone exposure time and cross-linking agent content, and the surface possesses highest conversion. The formation of a SiO(x) layer increased surface roughness, but it decreased water contact angle. Gas permeation measurements on the UV-ozone exposure PDMS membranes documented interesting gas separation properties: the O(2) permeability of the cross-linked PDMS membrane before UV-ozone exposure was 777 barrer, and the O(2)/N(2) selectivity was 1.9; after UV-ozone exposure, the permeability decreased to 127 barrer while the selectivity increased to 5.4. The free volume depth profile of the SiO(x) layer was investigated by novel slow positron beam. The results show that free volume size increased with the depth, yet the degree of siloxane conversion to SiO(x) does not affect the amount of free volume.

Chemical Data Assimilation Estimates of Continental US Ozone and Nitrogen Budgets during INTEX-A

NASA Technical Reports Server (NTRS)

Pierce, Robert B.; Schaack, Todd K.; Al-Saadi, Jassim A.; Fairlie, T. Duncan; Kittaka, Chieko; Lingenfelser, Gretchen; Natarajan, Murali; Olson, Jennifer; Soja, Amber; Zapotocny, Tom;

Surface ozone characterization at Larsemann Hills and Maitri, Antarctica.

PubMed

Ali, Kaushar; Trivedi, D K; Sahu, S K

2017-04-15

Data are analyzed in terms of daily average ozone, its diurnal variation and its relation with meteorological parameters like dry bulb temperature (T), wet bulb temperature (T w ), atmospheric pressure and wind speed based on measurement of these parameters at two Indian Antarctic stations (Larsemann Hills, and Maitri) during 28th Indian Scientific Expedition of Antarctica (ISEA) organized during Antarctic summer of the year 2008-09. The work has been carried out to investigate summer time ozone level and its day-to-day and diurnal variability at these coastal locations and to highlight possible mechanism of ozone production and destruction. The result of the analysis indicates that daily average ozone concentration at Larsemann Hills varied from ~13 and ~20ppb with overall average value of ~16ppb and at Maitri, it varied from ~16 and ~21ppb with overall average value of ~18ppb. Photochemistry is found to partially contribute occasionally to the surface layer ozone at both the stations. Lower concentration of ozone at Maitri during beginning of the observational days may be due to destruction of ozone through activated halogens, whereas higher ozone on latter days may be due to photochemistry and advective transport from east to south-east areas. Ozone concentration during blizzard episodes at both the stations is reduced due to slow photochemical production of ozone, its photochemical removal and removal through deposition of ozone molecules on precipitation particles. Diurnal variation of ozone at Larsemann Hills and Maitri has been found to be absent. Copyright © 2017 Elsevier B.V. All rights reserved.

Camx Ozone Source Attribution in the Eastern United States Using Guidance from Observations During DISCOVER-AQ Maryland

NASA Technical Reports Server (NTRS)

Goldberg, Daniel L.; Vinciguerra, Timothy P.; Anderson, Daniel C.; Hembeck, Linda; Canty, Timothy P.; Ehrman, Sheryl H.; Martins, Douglas K.; Stauffer, Ryan M.; Thompson, Anne M.; Salawitch, Ross J.;

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

Schemes used to parameterise ozone dry deposition velocity at the oceanic surface mainly differ in terms of how the dominant term of surface resistance is parameterised. We examine three such schemes and test them in a global climate-chemistry model that incorporates meteorological nudging and monthly-varying reactive-gas emissions. The default scheme invokes the commonly used assumption that the water surface resistance is constant. The other two schemes, named the one-layer and two-layer reactivity schemes, include the simultaneous influence on the water surface resistance of ozone solubility in water, waterside molecular diffusion and turbulent transfer, and a first-order chemical reaction of ozone with dissolved iodide. Unlike the one-layer scheme, the two-layer scheme can indirectly control the degree of interaction between chemical reaction and turbulent transfer through the specification of a surface reactive layer thickness. A comparison is made of the modelled deposition velocity dependencies on sea surface temperature (SST) and wind speed with recently reported cruise-based observations. The default scheme overestimates the observed deposition velocities by a factor of 2-4 when the chemical reaction is slow (e.g. under colder SSTs in the Southern Ocean). The default scheme has almost no temperature, wind speed, or latitudinal variations in contrast with the observations. The one-layer scheme provides noticeably better variations, but it overestimates deposition velocity by a factor of 2-3 due to an enhancement of the interaction between chemical reaction and turbulent transfer. The two-layer scheme with a surface reactive layer thickness specification of 2.5 µm, which is approximately equal to the reaction-diffusive length scale of the ozone-iodide reaction, is able to simulate the field measurements most closely with respect to absolute values as well as SST and wind-speed dependence. The annual global oceanic deposition of ozone determined using this scheme is approximately half of the original oceanic deposition obtained using the default scheme, and it corresponds to a 10 % decrease in the original estimate of the total global ozone deposition. The previously reported modelled estimate of oceanic deposition is roughly one-third of total deposition and with this new parameterisation it is reduced to 12 % of the modelled total global ozone deposition. Deposition parameterisation influences the predicted atmospheric ozone mixing ratios, especially in the Southern Hemisphere. For the latitudes 45-70° S, the two-layer scheme improves the prediction of ozone observed at an altitude of 1 km by 7 % and that within the altitude range 1-6 km by 5 % compared to the default scheme.

Surface studies of low molecular weight photolysis products from UV-ozone oxidised polystyrene

NASA Astrophysics Data System (ADS)

Davidson, M. R.; Mitchell, S. A.; Bradley, R. H.

2005-05-01

The production of low molecular weight oxidised material during UV-ozone treatment of polystyrene has been studied by XPS, GC-MS, FTIR and UV/visible spectroscopy. XPS analysis of the oxidised polystyrene surfaces before and after washing with water or methanol indicates that the removal of oxidation products and the surface that remains after washing is strongly dependent on the choice of solvent. Methanol washing removes a greater proportion of the more highly oxidised carbonyl and carboxyl groups resulting in a surface with a lower oxygen content than that remaining after water washing. Extended exposure to UV-ozone treatment reveals a two-stage oxidation process with mono-substituted benzene rings such as benzaldehyde, acetophenone and benzoic acid being produced at exposure times less than 15 min. Compounds, more typical of those formed via dehydration reactions of existing oxidised species, are produced at longer exposure times. UV-visible spectroscopy and Fourier transform infrared spectroscopy also confirm the presence of carboxylic acid, aromatic ketones and esters. Measurements of water contact angle on a 10 min treated surface reveals that methanol washing produces a more hydrophilic surface than water washing, the resulting water contact angles being 47° and 62° respectively. Ageing of methanol washed surfaces for 24 h leads to a recovery of the water contact angle back to 62° which suggests some form of post-washing surface relaxation process. Since XPS analyses show no increase in the oxygen concentration of the methanol washed surfaces after a 24 h ageing period, the increase in contact angle found with ageing is attributed to the reorientation of very near-surface functional groups i.e. within the XPS sampling depth.

Contributors to ozone episodes in three US/Mexico border twin-cities.

PubMed

Shi, Chune; Fernando, H J S; Yang, Jie

2009-09-01

The Process Analysis tools of the Community Multiscale Air Quality (CMAQ) modeling system together with back-trajectory analysis were used to assess potential contributors to ozone episodes that occurred during June 1-4, 2006, in three populated U.S.-Mexico border twin cities: San Diego/Tijuana, Imperial/Mexicali and El Paso/Ciudad Juárez. Validation of CMAQ output against surface ozone measurements indicates that the predictions are acceptable with regard to commonly recommended statistical standards and comparable to other reported studies. The mean normalized bias test (MNBT) and mean normalized gross error (MNGE) for hourly ozone fall well within the US EPA suggested range of +/-15% and 35%, respectively, except MNBT for El Paso. The MNBTs for maximum 8-h average ozone are larger than those for hourly ozone, but all the simulated maximum 8-h average ozone are within a factor of 2 of those measured in all three regions. The process and back-trajectory analyses indicate that the main sources of daytime ground-level ozone are the local photochemical production and regional transport. By integrating the effects of each process over the depth of the daytime planetary boundary layer (PBL), it is found that in the San Diego area (SD), chemistry and vertical advection contributed about 36%/48% and 64%/52% for June 2 and 3, respectively. This confirms the previous finding that high-altitude regional transport followed by fumigation contributes significantly to ozone in SD. The back-trajectory analysis shows that this ozone was mostly transported from the coastal area of southern California. For the episodes in Imperial Valley and El Paso, respectively, ozone was transported from the coastal areas of southern California and Mexico and from northern Texas and Oklahoma.

Device performance and lifetime of polymer:fullerene solar cells with UV-ozone-irradiated hole-collecting buffer layers.

PubMed

Lee, Seungsoo; Nam, Sungho; Lee, Hyena; Kim, Hwajeong; Kim, Youngkyoo

2011-11-18

We report the influence of UV-ozone irradiation of the hole-collecting buffer layers on the performance and lifetime of polymer:fullerene solar cells. UV-ozone irradiation was targeted at the surface of the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layers by varying the irradiation time up to 600 s. The change of the surface characteristics in the PEDOT:PSS after UV-ozone irradiation was measured by employing optical absorption spectroscopy, photoelectron yield spectroscopy, and contact angle measurements, while Raman and X-ray photoelectron spectroscopy techniques were introduced for more microscopic analysis. Results showed that the UV-ozone irradiation changed the chemical structure/composition of the surface of the PEDOT:PSS layers leading to the gradual increase of ionization potential with irradiation time in the presence of up-and-down variations in the contact angle (polarity). This surface property change was attributed to the formation of oxidative components, as evidenced by XPS and Auger electron images, which affected the sheet resistance of the PEDOT:PSS layers. Interestingly, device performance was slightly improved by short irradiation (up to 10 s), whereas it was gradually decreased by further irradiation. The short-duration illumination test showed that the lifetime of solar cells with the UV-ozone irradiated PEDOT:PSS layer was improved due to the protective role of the oxidative components formed upon UV-ozone irradiation against the attack of sulfonic acid groups in the PEDOT:PSS layer to the active layer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the role of ozone feedback in the ENSO amplitude response under global warming

NASA Astrophysics Data System (ADS)

Nowack, P. J.; Braesicke, P.; Abraham, N. L.; Pyle, J. A.

2017-12-01

The El Niño-Southern Oscillation (ENSO) in the tropical Pacific is of key importance to global climate and weather. However, climate models still disagree on the ENSO's response under climate change. Here we show that typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations (i.e. standard abrupt 4xCO2). We mainly explain this effect by the lapse rate adjustment of the tropical troposphere to ozone changes in the upper troposphere and lower stratosphere (UTLS) under 4xCO2. The ozone-induced lapse rate changes modify the Walker circulation response to the CO2 forcing and consequently tropical Pacific surface temperature gradients. Therefore, not including ozone feedbacks increases the number of extreme ENSO events in our model. In addition, we demonstrate that even if ozone changes in the tropical UTLS are included in the simulations, the neglect of the ozone response in the middle-upper stratosphere still leads to significantly larger ENSO amplitudes (compared to simulations run with a fully interactive atmospheric chemistry scheme). Climate modeling studies of the ENSO often neglect changes in ozone. Our results imply that this could affect the inter-model spread found in ENSO projections and, more generally, surface climate change simulations. We discuss the additional complexity in quantifying such ozone-related effects that arises from the apparent model dependency of chemistry-climate feedbacks and, possibly, their range of surface climate impacts. In conclusion, we highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability. Reference: Nowack PJ, Braesicke P, Abraham NL, and Pyle JA (2017), On the role of ozone feedback in the ENSO amplitude response under global warming, Geophys. Res. Lett. 44, 3858-3866, doi:10.1002/2016GL072418.

On the role of atmosphere-ocean interactions in the expected long-term changes of the Earth's ozone layer caused by greenhouse gases

NASA Astrophysics Data System (ADS)

Zadorozhny, Alexander; Dyominov, Igor

It is well known that anthropogenic emissions of greenhouse gases into the atmosphere produce a global warming of the troposphere and a global cooling of the stratosphere. The expected stratospheric cooling essentially influences the ozone layer via increased polar stratospheric cloud formation and via temperature dependences of the gas phase reaction rates. One more mechanism of how greenhouse gases influences the ozone layer is enhanced water evaporation from the oceans into the atmosphere because of increasing temperatures of the ocean surface due to greenhouse effect. The subject of this paper is a study of the influence of anthropogenic pollution of the atmosphere by the greenhouse gases CO2, CH4, N2O and ozone-depleting chlorine and bromine compounds on the expected long-term changes of the ozone layer with taking into account an increase of water vapour content in the atmosphere due to greenhouse effect. The study based on 2-D zonally averaged interactive dynamical radiative-photochemical model of the troposphere and stratosphere. The model allows to self-consistently calculating diabatic circulation, temperature, gaseous composition of the troposphere and stratosphere at latitudes from the South to North Poles, as well as distribution of sulphate aerosol particles and polar stratospheric clouds of two types. It was supposed in the model that an increase of the ocean surface temperature caused by greenhouse effect is similar to calculated increase of atmospheric surface temperature. Evaporation rate from the ocean surface was computed in dependence of latitude. The model time-dependent runs were made for the period from 1975 to 2100 using two IPCC scenarios depicting maximum and average expected increases of greenhouse gases in the atmosphere. The model calculations show that anthropogenic increasing of water vapour abundance in the atmosphere due to heating of the ocean surface caused by greenhouse effect gives a sensible contribution to the expected ozone changes. The enhanced evaporation from the ocean increases noticeably a water vapour abundance in the stratosphere that decreases global total ozone and retards the expected recovery of the ozone layer. In polar latitudes, additional stratospheric water vapour increase due to greenhouse effect noticeably strengthens the impact of anthropogenic greenhouse gases on ozone through modification of polar stratospheric clouds and retards the expected recovery of the ozone, too. In the Northern hemisphere, the delay of the ozone recovery is about 5 years, in the Southern hemisphere the delay is about 2 years.

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria

NASA Astrophysics Data System (ADS)

Mahfoudh, Ahlem; Barbeau, Jean; Moisan, Michel; Leduc, Annie; Séguin, Jacynthe

2010-03-01

Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

A Two-Timescale Response to Ozone Depletion: Importance of the Background State

NASA Astrophysics Data System (ADS)

Seviour, W.; Waugh, D.; Gnanadesikan, A.

2015-12-01

It has been recently suggested that the response of Southern Ocean sea-ice extent to stratospheric ozone depletion is time-dependent; that the ocean surface initially cools due to enhanced northward Ekman drift caused by a poleward shift in the eddy-driven jet, and then warms after some time due to upwelling of warm waters from below the mixed layer. It is therefore possible that ozone depletion could act to favor a short-term increase in sea-ice extent. However, many uncertainties remain in understanding this mechanism, with different models showing widely differing time-scales and magnitudes of the response. Here, we analyze an ensemble of coupled model simulations with a step-function ozone perturbation. The two-timescale response is present with an approximately 30 year initial cooling period. The response is further shown to be highly dependent upon the background ocean temperature and salinity stratification, which is influenced by both natural internal variability and the isopycnal eddy mixing parameterization. It is suggested that the majority of inter-model differences in the Southern Ocean response to ozone depletion is caused by differences in stratification.

Development of KRISS standard reference photometer (SRP) for ambient ozone measurement

NASA Astrophysics Data System (ADS)

Lee, S.; Lee, J.

2014-12-01

Surface ozone has adverse impacts on human health and ecosystem. Accurate measurement of ambient ozone concentration is essential for developing effective mitigation strategies and understanding atmospheric chemistry. Korea Research Institute of Standards and Science (KRISS) has developed new ozone standard reference photometers (SRPs) for the calibration of ambient ozone instruments. The basic principle of the KRISS ozone SRPs is to determine the absorption of ultraviolet radiation at a specific wavelength, 253.7 nm, by ozone in the atmosphere. Ozone concentration is calculated by converting UV transmittance through the Beer-Lambert Law. This study introduces the newly developed ozone SRPs and characterizes their performance through uncertainty analysis and comparison with BIPM (International Bureau of Weights and Measures) SRP.

Degradation of recalcitrant naphthenic acids from raw and ozonated oil sands process-affected waters by a semi-passive biofiltration process.

PubMed

Zhang, Lei; Zhang, Yanyan; Gamal El-Din, Mohamed

2018-04-15

In this study, a fixed-bed biofiltration system (biofilter) that utilized indigenous microorganisms was developed for the reclamation of oil sands process-affected water (OSPW). With the assistance of quantitative polymerase chain reaction (qPCR) and confocal laser scanning microscopy (CLSM), indigenous microorganisms from OSPW were able to attach to the surface of sand media and form biofilms. The number of total bacteria on the biofilter media reached a steady state (10 9 /g) after 23 days of operation. Ultra Performance Liquid Chromatography/High Resolution Mass Spectrometry (UPLC/HRMS) analysis showed that 21.8% of the classical naphthenic acids (NAs) removal was achieved through the circulation of raw OSPW on the biofilter for 8 times (equivalent to a hydraulic retention time of 16 h). When ozonation with utilized ozone dose of 30 mg/L was applied as pretreatment, the classical NAs in the ozonated OSPW were removed by 89.3% with an accelerated biodegradation rate of 0.5 mg/L/h. Compared with other biofilm reactors such as moving bed biofilm reactor (MBBR), ozonation pretreatment could benefit the biodegradation of NAs in the biofilter more (classical NA removal: 89.3% vs. 34.4%), especially for those with high carbon number and cyclicity. The combined ozonation-biofiltration process could remove 92.7% of classical NAs from raw OSPW in 16 h. Although both ozonation and biofiltration alone did not show degradation of oxidized NAs from raw OSPW, the combined process led to a 52.9% and 42.6% removal for O 3 -NAs and O 4 -NAs, respectively, which were the dominant oxidized NA species in OSPW. Metagenomic sequencing analysis showed that Rhodococcus was the dominant bacterial genus on the sand media, which may play a crucial role during the NA biodegradation. With the advantage of high NA removal efficiency, the combined ozonation-biofiltration process is a promising approach for NA degradation and shows high potential to be scaled up for in-situ OSPW treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Natural zeolite reactivity towards ozone: the role of compensating cations.

PubMed

Valdés, Héctor; Alejandro, Serguei; Zaror, Claudio A

2012-08-15

Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal. Copyright © 2012 Elsevier B.V. All rights reserved.

Ultraviolet-ozone treatment reduces levels of disease-associated prion protein and prion infectivity

USGS Publications Warehouse

Johnson, C.J.; Gilbert, P.; McKenzie, D.; Pedersen, J.A.; Aiken, Judd M.

2009-01-01

Background. Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases caused by novel infectious agents referred to as prions. Prions appear to be composed primarily, if not exclusively, of a misfolded isoform of the cellular prion protein. TSE infectivity is remarkably stable and can resist many aggressive decontamination procedures, increasing human, livestock and wildlife exposure to TSEs. Findings. We tested the hypothesis that UV-ozone treatment reduces levels of the pathogenic prion protein and inactivates the infectious agent. We found that UV-ozone treatment decreased the carbon and prion protein content in infected brain homogenate to levels undetectable by dry-ashing carbon analysis or immunoblotting, respectively. After 8 weeks of ashing, UV-ozone treatment reduced the infectious titer of treated material by a factor of at least 105. A small amount of infectivity, however, persisted despite UV-ozone treatment. When bound to either montmorillonite clay or quartz surfaces, PrPTSE was still susceptible to degradation by UV-ozone. Conclusion. Our findings strongly suggest that UV-ozone treatment can degrade pathogenic prion protein and inactivate prions, even when the agent is associated with surfaces. Using larger UV-ozone doses or combining UV-ozone treatment with other decontaminant methods may allow the sterilization of TSE-contaminated materials. ?? 2009 Aiken et al; licensee BioMed Central Ltd.

Radiative Forcing Due to Enhancements in Tropospheric Ozone and Carbonaceous Aerosols Caused by Asian Fires During Spring 2008

NASA Technical Reports Server (NTRS)

Natarajan, Murali; Pierce, R. Bradley; Lenzen, Allen J.; Al-Saadi, Jassim A.; Soja, Amber J.; Charlock, Thomas P.; Rose, Fred G.; Winker, David M.; Worden, John R.

2012-01-01

Simulations of tropospheric ozone and carbonaceous aerosol distributions, conducted with the Real-time Air Quality Modeling System (RAQMS), are used to study the effects of major outbreaks of fires that occurred in three regions of Asia, namely Thailand, Kazakhstan, and Siberia, during spring 2008. RAQMS is a global scale meteorological and chemical modeling system. Results from these simulations, averaged over April 2008, indicate that tropospheric ozone column increases by more than 10 Dobson units (DU) near the Thailand region, and by lesser amounts in the other regions due to the fires. Widespread increases in the optical depths of organic and black carbon aerosols are also noted. We have used an off-line radiative transfer model to evaluate the direct radiative forcing due to the fire-induced changes in atmospheric composition. For clear sky, the monthly averaged radiative forcing at the top of the atmosphere (TOA) is mostly negative with peak values less than -12 W/sq m occurring near the fire regions. The negative forcing represents the increased outgoing shortwave radiation caused by scattering due to carbonaceous aerosols. At high latitudes, the radiative forcing is positive due to the presence of absorbing aerosols over regions of high surface albedo. Regions of positive forcing at TOA are more pronounced under total sky conditions. The monthly averaged radiative forcing at the surface is mostly negative, and peak values of less than -30 W/sq m occur near the fire regions. Persistently large negative forcing at the surface could alter the surface energy budget and potentially weaken the hydrological cycle.

Immobilization of naringin onto chitosan substrates by using ozone activation.

PubMed

Li, Chung Hsing; Wang, Jing Wei; Ho, Ming Hua; Shih, Jia Lin; Hsiao, Sheng Wen; Thien, Doan Van Hong

2014-03-01

Ozone oxidation can easily produce peroxides containing active free radicals that can be used for the surface modification of biomaterials. This process is highly efficient and nontoxic. In this research, naringin, an HMG-CoA reductase inhibitor that can promote bone formation, was immobilized onto a chitosan film using ozone activation. First, a chitosan film was treated by ozone to produce peroxides; these peroxides were then quantified and their amount was optimized by an iodide assay. For the in vitro delivery of naringin, a chitosan-naringin substrate was immersed in phosphate-buffered saline to quantify the released amount of naringin. It was found that the immobilized naringin was slowly released over the course of two weeks, where its concentration in the medium was controlled by this delivery process. The results of cell culture showed that cell viability and early osteogenic differentiation, as measured by alkaline phosphatase expression, were promoted with the immobilized naringin on chitosan substrates. The expression of osteogenic proteins, including type-I collagen, bone siloprotein, and osteocalcin, were also enhanced. According to the results of Smad1 and Smad6 phosphorylation, immobilized naringin on ozonated chitosan substrates would be able to initiate bone morphogenetic protein-Smad signaling by activating receptor Smad and by suppressing inhibitory Smad. The results in this research demonstrated that the naringin-chitosan substrate produced by biocompatible ozone activation was highly osteoconductive without cytotoxicity. Copyright © 2013 Elsevier B.V. All rights reserved.

EVALUATION OF OZONATION BY-PRODUCTS FROM TWO CALIFORNIA SURFACE WATERS

EPA Science Inventory

Ozonation by-products were analyzed for two surface water sources in Southern California--Los Angeles Aqueduct Water (LAAW) and State Project Water (SPW). ncluded are data obtained when LAAW was being treated at the Los Angeles Aqueduct Filtration Plant and similar data obtained ...

EVALUATION OF OZONATION BY-PRODUCTS FROM TWO CALIFORNIA SURFACE WATERS

EPA Science Inventory

Ozonation by-products were analyzed for two surface water sources in Southern California-Los Angeles Aqueduct Water (LAWW) and State Project Water (SPW). Included are data obtained when LAAW was being treated at the Los Angeles Aqueduct Filtration Plant and similar data obtained...

Ozone budgets from the Dynamics and Chemistry of Marine Stratocumulus experiment

NASA Technical Reports Server (NTRS)

Kawa, S. R.; Pearson, R., Jr.

1989-01-01

Measurements from the Dynamics and Chemistry of marine Stratocumulus experiment have been used to study components of the regional ozone budget. The surface destruction rate is determined by eddy correlation of ozone and vertical velocity measured by a low-flying aircraft. Significant variability is found in the measured surface resistance; it is partially correlated with friction velocity but appears to have other controlling influences as well. The mean resistance is 4190 s/m which is higher (slower destruction) than most previous estimates for seawater. Flux and mean measurements throughout the marine boundary layer are used to estimate the net rate of in situ photochemical production/destruction of ozone. Averaged over the flights, ozone concentration is found to be near steady state, and a net of photochemical destruction of 0.02-0.07 ng/cu m per sec is diagnosed. This is an important confirmation of photochemical model results for the remote marine boundary layer. Ozone vertical distributions above the boundary layer show a strongly layered structure with very sharp gradients. These distributions are possibly related to the stratospheric ozone source.

Ozone reactions with indoor materials during building disinfection

NASA Astrophysics Data System (ADS)

Poppendieck, D.; Hubbard, H.; Ward, M.; Weschler, C.; Corsi, R. L.

There is scant information related to heterogeneous indoor chemistry at ozone concentrations necessary for the effective disinfection of buildings, i.e., hundreds to thousands of ppm. In the present study, 24 materials were exposed for 16 h to ozone concentrations of 1000-1200 ppm in the inlet streams of test chambers. Initial ozone deposition velocities were similar to those reported in the published literature for much lower ozone concentrations, but decayed rapidly as reaction sites on material surfaces were consumed. For every material, deposition velocities converged to a relatively constant, and typically low, value after approximately 11 h. The four materials with the highest sustained deposition velocities were ceiling tile, office partition, medium density fiberboard and gypsum wallboard backing. Analysis of ozone reaction probabilities indicated that throughout each experiment, and particularly after several hours of disinfection, surface reaction resistance dominated the overall resistance to ozone deposition for nearly all materials. Total building disinfection by-products (all carbonyls) were quantified per unit area of each material for the experimental period. Paper, office partition, and medium density fiberboard each released greater than 38 mg m -2 of by-products.

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

PubMed

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.

Process-scale modeling of elevated wintertime ozone in Wyoming.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotamarthi, V. R.; Holdridge, D. J.; Environmental Science Division

2007-12-31

Measurements of meteorological variables and trace gas concentrations, provided by the Wyoming Department of Environmental Quality for Daniel, Jonah, and Boulder Counties in the state of Wyoming, were analyzed for this project. The data indicate that highest ozone concentrations were observed at temperatures of -10 C to 0 C, at low wind speeds of about 5 mph. The median values for nitrogen oxides (NOx) during these episodes ranged between 10 ppbv and 20 ppbv (parts per billion by volume). Measurements of volatile organic compounds (VOCs) during these periods were insufficient for quantitative analysis. The few available VOCs measurements indicated unusuallymore » high levels of alkanes and aromatics and low levels of alkenes. In addition, the column ozone concentration during one of the high-ozone episodes was low, on the order of 250 DU (Dobson unit) as compared to a normal column ozone concentration of approximately 300-325 DU during spring for this region. Analysis of this observation was outside the scope of this project. The data analysis reported here was used to establish criteria for making a large number of sensitivity calculations through use of a box photochemical model. Two different VOCs lumping schemes, RACM and SAPRC-98, were used for the calculations. Calculations based on this data analysis indicated that the ozone mixing ratios are sensitive to (a) surface albedo, (b) column ozone, (c) NOx mixing ratios, and (d) available terminal olefins. The RACM model showed a large response to an increase in lumped species containing propane that was not reproduced by the SAPRC scheme, which models propane as a nearly independent species. The rest of the VOCs produced similar changes in ozone in both schemes. In general, if one assumes that measured VOCs are fairly representative of the conditions at these locations, sufficient precursors might be available to produce ozone in the range of 60-80 ppbv under the conditions modeled.« less

The chemical and radiative effects of the Mount Pinatubo eruption

NASA Technical Reports Server (NTRS)

Kinneson, Douglas E.; Grant, Keith E.; Connell, Peter S.; Rotman, Douglas A.; Wuebbles, Donald J.

1994-01-01

To clarify the mechanisms leading to effects on stratospheric ozone, time-dependent stratospheric aerosol and gas experiment II (SAGE II) and cryogenic limb array elaton spectrometer (CLAES) aerosol optical extinction data and SAGE II surface area density are used as parameters in a two-dimensional (2-D) zonally averaged chemical radiative transport model. The model was integrated with time from before the eruption through December 1993. The modeled impact on global ozone results from increased rates of heterogeneous reactions on sulfate aerosols and from the increased radiative heating and scattering caused by these aerosols. When the aerosol heating is allowed to modify the temperature distribution, the maximum change calculated in equatorial column ozone is -1.6%. The calculated equatorial temperature change and peak local ozone change in October 1991 are +6K and -4%, respectively. When aerosol heating perturbs the circulation in the model, the maximum change in equatorial column ozone is -6%. Increased heterogeneous processing on sulfate aerosols is calculated to have changed equatorial column ozone in late 1991 by -1.5%. Global column ozone in the model in 1992 and 1993 changed by -2.8% and -2.4%, respectively. The relationship of ozone-controlling processes in the lower stratosphere is altered as well; HO(x) becomes the most important catalytic cycle, followed by ClO(x) and NO(x). This is driven by significant changes in trace gas concentrations. In October 1991, lower stratospheric, equatorial NO(x) decreased by 40%, ClO(x) increased by 60%, and HO(x) increased by 25%. When the effect of heterogeneous chemical processing on sulfate aerosols is combined with aerosol heating, modifying either circulation or temperature, dramatically different ozone fingerprints with time and latitude are predicted. Model-derived changes in the equatorial region in column ozone best represented the observed data when perturbed circulation was combined with heterogeneous chemical effects. However, at high latitudes, the increased ozone production from the strengthening of the mean circulation tends to cancel the heterogeneous reduction of ozone. This is not in good agreement with observed data, especially in 1992 and 1993. When the circulation is held fixed and the temperature allowed to change, and heterogeneous chemical effects are included, the equatorial ozone decrease predicted was too small for 1991. However, the mid- to high-latitude decrease in 1992 and 1993 is in better agreement with observed data.

3rd hand smoking; heterogeneous oxidation of nicotine and secondary aerosol formation in the indoor environment

NASA Astrophysics Data System (ADS)

Petrick, Lauren; Dubowski, Yael

2010-05-01

Tobacco smoking is well known as a significant source of primary indoor air pollutants. However, only recently has it been recognized that the impact of Tobacco smoking may continue even after the cigarette has been extinguished (i.e., third hand smoke) due to the effect of indoor surfaces. These surfaces may affect the fate of tobacco smoke in the form of secondary reactions and pollutants, including secondary organic aerosol (SOA) formation. Fourier Transform Infrared spectrometry with Attenuated Total Reflection (FTIR-ATR) in tandem with a Scanning Mobility Particle Sizing (SMPS) system was used to monitor the ozonation of cellulose sorbed nicotine and resulting SOA formation. SOA formation began at onset of ozone introduction ([O3] = 60 ± 5 ppb) with a size distribution of dp ≤ 25 nm, and was determined to be a result of heterogeneous reaction (opposed to homogeneous). SOA yield from reacted surface nicotine was on the order of 10 %. Simultaneous to SOA monitoring, FTIR-ATR spectra showed surface changes in the nicotine film as the reaction progressed, revealing a pseudo first-order surface reaction rate of 0.0026 ± 0.0008 min-1. Identified surface oxidation products included: cotinine, myosmine, methylnicotinamide and nicotyrine. Surface reaction rate was found to be partially inhibited at high relative humidity. Given the toxicity of some of the identified products (e.g., cotinine has shown potential mutagenicity and teratogenicity) and that small particles may contribute to adverse health effects, the present study indicates that exposure to 3rd hand smoke ozonation products may pose additional health risks.

Impacts of ozone-vegetation coupling and feedbacks on global air quality, ecosystems and food security

NASA Astrophysics Data System (ADS)

Tai, A. P. K.

2016-12-01

Surface ozone is an air pollutant of significant concerns due to its harmful effects on human health, vegetation and crop productivity. Chronic ozone exposure is shown to reduce photosynthesis and interfere with gas exchange in plants, thereby influencing surface energy balance and biogeochemical fluxes with important ramifications for climate and atmospheric composition, including possible feedbacks onto ozone itself that are not well understood. Ozone damage on crops has been well documented, but a mechanistic understanding is not well established. Here we present several results pertaining to the effects of ozone-vegetation coupling on air quality, ecosystems and agriculture. Using the Community Earth System Model (CESM), we find that inclusion of ozone damage on plants reduces the global land carbon sink by up to 5%, while simulated ozone is enhanced by up to 6 ppbv North America, Europe and East Asia. This strong positive feedback on ozone air quality via ozone-vegetation coupling arises mainly from reduced stomatal conductance, which induces two feedback pathways: 1) reduced dry deposition and ozone uptake; and 2) reduced evapotranspiration that enhances vegetation temperature and thus isoprene emission. Using the same ozone-vegetation scheme in a crop model within CESM, we further examine the impacts of historical ozone exposure on global crop production. We contrast our model results with a separate statistical analysis designed to characterize the spatial variability of crop-ozone-temperature relationships and account for the confounding effect of ozone-temperature covariation, using multidecadal global datasets of crop yields, agroclimatic variables and ozone exposures. We find that several crops (especially C4 crops such as maize) exhibit stronger sensitivities to ozone than found by field studies or in CESM simulations. We also find a strong anticorrelation between crop sensitivities and average ozone levels, reflecting biological adaptive ozone resistance that is not accounted for in current generation of crop models. Our results show that a more complete understanding of ozone-vegetation interactions is necessary to derive more realistic future projections of climate, air quality, ecosystem functions and food security.

Multi-year objective analyses of warm season ground-level ozone and PM2.5 over North America using real-time observations and Canadian operational air quality models

NASA Astrophysics Data System (ADS)

Robichaud, A.; Ménard, R.

2013-05-01

We present multi-year objective analyses (OA) on a high spatio-temporal resolution (15 or 21 km, every hour) for the warm season period (1 May-31 October) for ground-level ozone (2002-2012) and for fine particulate matter (diameter less than 2.5 microns (PM2.5)) (2004-2012). The OA used here combines the Canadian Air Quality forecast suite with US and Canadian surface air quality monitoring sites. The analysis is based on an optimal interpolation with capabilities for adaptive error statistics for ozone and PM2.5 and an explicit bias correction scheme for the PM2.5 analyses. The estimation of error statistics has been computed using a modified version of the Hollingsworth-Lönnberg's (H-L) method. Various quality controls (gross error check, sudden jump test and background check) have been applied to the observations to remove outliers. An additional quality control is applied to check the consistency of the error statistics estimation model at each observing station and for each hour. The error statistics are further tuned "on the fly" using a χ2 (chi-square) diagnostic, a procedure which verifies significantly better than without tuning. Successful cross-validation experiments were performed with an OA set-up using 90% of observations to build the objective analysis and with the remainder left out as an independent set of data for verification purposes. Furthermore, comparisons with other external sources of information (global models and PM2.5 satellite surface derived measurements) show reasonable agreement. The multi-year analyses obtained provide relatively high precision with an absolute yearly averaged systematic error of less than 0.6 ppbv (parts per billion by volume) and 0.7 μg m-3 (micrograms per cubic meter) for ozone and PM2.5 respectively and a random error generally less than 9 ppbv for ozone and under 12 μg m-3 for PM2.5. In this paper, we focus on two applications: (1) presenting long term averages of objective analysis and analysis increments as a form of summer climatology and (2) analyzing long term (decadal) trends and inter-annual fluctuations using OA outputs. Our results show that high percentiles of ozone and PM2.5 are both following a decreasing trend overall in North America with the eastern part of United States (US) presenting the highest decrease likely due to more effective pollution controls. Some locations, however, exhibited an increasing trend in the mean ozone and PM2.5 such as the northwestern part of North America (northwest US and Alberta). The low percentiles are generally rising for ozone which may be linked to increasing emissions from emerging countries and the resulting pollution brought by the intercontinental transport. After removing the decadal trend, we demonstrate that the inter-annual fluctuations of the high percentiles are significantly correlated with temperature fluctuations for ozone and precipitation fluctuations for PM2.5. We also show that there was a moderately significant correlation between the inter-annual fluctuations of the high percentiles of ozone and PM2.5 with economic indices such as the Industrial Dow Jones and/or the US gross domestic product growth rate.

Global health benefits of mitigating ozone pollution with methane emission controls.

PubMed

West, J Jason; Fiore, Arlene M; Horowitz, Larry W; Mauzerall, Denise L

2006-03-14

Methane (CH(4)) contributes to the growing global background concentration of tropospheric ozone (O(3)), an air pollutant associated with premature mortality. Methane and ozone are also important greenhouse gases. Reducing methane emissions therefore decreases surface ozone everywhere while slowing climate warming, but although methane mitigation has been considered to address climate change, it has not for air quality. Here we show that global decreases in surface ozone concentrations, due to methane mitigation, result in substantial and widespread decreases in premature human mortality. Reducing global anthropogenic methane emissions by 20% beginning in 2010 would decrease the average daily maximum 8-h surface ozone by approximately 1 part per billion by volume globally. By using epidemiologic ozone-mortality relationships, this ozone reduction is estimated to prevent approximately 30,000 premature all-cause mortalities globally in 2030, and approximately 370,000 between 2010 and 2030. If only cardiovascular and respiratory mortalities are considered, approximately 17,000 global mortalities can be avoided in 2030. The marginal cost-effectiveness of this 20% methane reduction is estimated to be approximately 420,000 US dollars per avoided mortality. If avoided mortalities are valued at 1 US dollars million each, the benefit is approximately 240 US dollars per tone of CH(4) ( approximately 12 US dollars per tone of CO(2) equivalent), which exceeds the marginal cost of the methane reduction. These estimated air pollution ancillary benefits of climate-motivated methane emission reductions are comparable with those estimated previously for CO(2). Methane mitigation offers a unique opportunity to improve air quality globally and can be a cost-effective component of international ozone management, bringing multiple benefits for air quality, public health, agriculture, climate, and energy.

A room temperature method for the formation of ultrathin silicon oxide films

NASA Astrophysics Data System (ADS)

Muisener, Richard John

Growing interest surrounds the use of thin films to impart unique surface properties without adversely affecting those of the bulk. One such example is the formation of a stable high-energy silicon oxide surface on polymers. Thin silicon oxide films have been used to tailor the surface properties of many materials. Conventional methods for SiOx film fabrication such as chemical vapor deposition require either high temperature or expensive vacuum chambers. This research focuses on the intrinsically inexpensive process of UV-ozone to form ultrathin SiOx films from polysiloxane precursors at room temperature and atmospheric pressure. Chemical evidence suggests a complete conversion from organic polymer to inorganic ceramic. Through XPS, the UV-ozone treatment oxidizes over 95% of the silicone's organic side groups with a resulting stoichiometry Of Si 1O2.2C0.08. The silicon oxidation state changes from 2+ in poly(dimethylsiloxane) to 93% 4+ corresponding to SiO2. IR studies show a total loss of methyl bands and the growth of a new Si-O band centered at 1225 cm-1. Gas phase reaction products suggest a radical driven process. The physical properties also suggest a complete conversion to SiO x. Excellent control of film thickness, as low as 2 nm, has been demonstrated by variable angle spectroscopic ellipsometry. The ellipsometrically determined thickness loss of 55% during treatment corresponds to an SiOx film density of 1.9 g/cm3. The continuity of the film is demonstrated by electrical properties and a very low water contact angle consistent with SiOx. The later property ensures that the SiOx films are anti-fogging in nature. Unique hydrophilic-hydrophobic structures were formed through photo-patterning. The reaction has been successfully modeled as self-limiting based on the diffusion of ozone. The chief reactant, atomic oxygen, is generated by the photochemical dissociation of ozone and quickly generates radical species within the polymer film. The reaction proceeds through a cascade of radical reaction pathways until the resulting oxide is formed. The penetration of ozone is limited to the topmost 30 nm of the film; hence, the formation of SiOx is also surface limited. SiOx films of upto 10 nm are formed at room temperature from polymeric precursors.

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

NASA Technical Reports Server (NTRS)

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.;

From ozone mini-holes and mini-highs towards extreme value theory: New insights from extreme events and non-stationarity

NASA Astrophysics Data System (ADS)

Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Stübi, R.; Weihs, P.; Holawe, F.; Peter, T.; Davison, A. C.

2009-04-01

Over the last few decades negative trends in stratospheric ozone have been studied because of the direct link between decreasing stratospheric ozone and increasing surface UV-radiation. Recently a discussion on ozone recovery has begun. Long-term measurements of total ozone extending back earlier than 1958 are limited and only available from a few stations in the northern hemisphere. The world's longest total ozone record is available from Arosa, Switzerland (Staehelin et al., 1998a,b). At this site total ozone measurements have been made since late 1926 through the present day. Within this study (Rieder et al., 2009) new tools from extreme value theory (e.g. Coles, 2001; Ribatet, 2007) are applied to select mathematically well-defined thresholds for extreme low and extreme high total ozone. A heavy-tail focused approach is used by fitting the Generalized Pareto Distribution (GPD) to the Arosa time series. Asymptotic arguments (Pickands, 1975) justify the use of the GPD for modeling exceedances over a sufficiently high (or below a sufficiently low) threshold (Coles, 2001). More precisely, the GPD is the limiting distribution of normalized excesses over a threshold, as the threshold approaches the endpoint of the distribution. In practice, GPD parameters are fitted, to exceedances by maximum likelihood or other methods - such as the probability weighted moments. A preliminary step consists in defining an appropriate threshold for which the asymptotic GPD approximation holds. Suitable tools for threshold selection as the MRL-plot (mean residual life plot) and TC-plot (stability plot) from the POT-package (Ribatet, 2007) are presented. The frequency distribution of extremes in low (termed ELOs) and high (termed EHOs) total ozone and their influence on the long-term changes in total ozone are analyzed. Further it is shown that from the GPD-model the distribution of so-called ozone mini holes (e.g. Bojkov and Balis, 2001) can be precisely estimated and that the "extremes concept" provides new information on the data distribution and variability within the Arosa record as well as on the influence of ELOs and EHOs on the long-term trends of the ozone time series. References: Bojkov, R. D., and Balis, D.S.: Characteristics of episodes with extremely low ozone values in the northern middle latitudes 1975-2000, Ann. Geophys., 19, 797-807, 2001. Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Pickands, J.: Statistical inference using extreme order statistics, Ann. Stat., 3, 1, 119-131, 1975. Ribatet, M.: POT: Modelling peaks over a threshold, R News, 7, 34-36, 2007. Rieder, H.E., Staehelin, J., Maeder, J.A., Stübi, R., Weihs, P., Holawe, F., and M. Ribatet: From ozone mini holes and mini highs towards extreme value theory: New insights from extreme events and non stationarity, submitted to J. Geophys. Res., 2009. Staehelin, J., Kegel, R., and Harris, N. R.: Trend analysis of the homogenized total ozone series of Arosa (Switzerland), 1929-1996, J. Geophys. Res., 103(D7), 8389-8400, doi:10.1029/97JD03650, 1998a. Staehelin, J., Renaud, A., Bader, J., McPeters, R., Viatte, P., Hoegger, B., Bugnion, V., Giroud, M., and Schill, H.: Total ozone series at Arosa (Switzerland): Homogenization and data comparison, J. Geophys. Res., 103(D5), 5827-5842, doi:10.1029/97JD02402, 1998b.

Simulating climate change with interactive stratospheric ozone

NASA Astrophysics Data System (ADS)

Lin, P.; Ming, Y.

2017-12-01

We compare the simulated climate changes with and without interactive ozone in GFDL AM4. We also compare the simulations with a fully interactive stratospheric chemistry scheme versus those with a simplified scheme in which ozone is treated as a passive tracer. Despite its simplicity, the ozone tracer is sufficient to represent the ozone changes in response to changes in the stratospheric circulation as well as the zonally asymmetric distribution of ozone concentration. With interactive ozone, the model simulates a stronger cooling in the tropical lower stratosphere and less stratospheric moistening in response to surface warming. We further investigate how the different stratospheric response translate into different responses in the tropospheric circulations.

Application of Response Surface Methodology for characterization of ozone production from Multi-Cylinder Reactor in non-thermal plasma device

NASA Astrophysics Data System (ADS)

Lian See, Tan; Zulazlan Shah Zulkifli, Ahmad; Mook Tzeng, Lim

2018-04-01

Ozone is a reactant which can be applied for various environmental treatment processes. It can be generated via atmospheric air non-thermal plasmas when sufficient voltages are applied through a combination of electrodes and dielectric materials. In this study, the concentration of ozone generated via two different configurations of multi-cylinder dielectric barrier discharge (DBD) reactor (3 x 40 mm and 10 x 10 mm) was investigated. The influence of the voltage and the duty cycle to the concentration of ozone generated by each configuration was analysed using response surface methodology. Voltage was identified as significant factor to the ozone production process. However, the regressed model was biased towards one of the configuration, leaving the predicted results of another configuration to be out of range.

Noninvasive determination of respiratory ozone absorption: development of a fast-responding ozone analyzer.

PubMed

Ultman, J S; Ben-Jebria, A

1991-03-01

We developed a chemiluminescent ozone analyzer and constructed an ozone bolus generator with the eventual goal of using a bolus-response method to measure noninvasively the longitudinal distribution of ozone absorption in human lungs. Because the analyzer will be used to sample gases within a single breath, it must have a sufficiently rapid response to monitor changes in ozone concentration during a four-second breathing period, yet its sampling flow must be small enough that it does not interfere with quiet respiratory flows of 300 mL/sec. Our analyzer, which is based on the chemiluminescent reaction between 2-methyl-2-butene and ozone, has favorable performance characteristics: a 90 percent step-response time of 110 msec; a linear calibration from 0.03 to 10 parts per million (ppm)2 with a sensitivity of 2.3 nA/ppm; a signal-to-noise ratio of 30 evaluated at 0.5 ppm; and a minimum detection limit of 0.017 ppm. At an airflow corresponding to quiet breathing, the ozone generator is capable of producing single boluses with a peak ozone fraction as high as 4 ppm, but containing only 0.35 micrograms of ozone dispersed over a small volume of 19 mL. To test the combination of ozone analyzer and bolus generator, we performed bolus-response experiments at steady airflows of 50 to 200 mL/sec in excised pig and sheep tracheas. In spite of the small surface area available for radial diffusion, we found that 25 to 50 percent of the ozone introduced into the trachea was absorbed. By comparing the mathematical moments of the bolus input and the response curves to the predictions of a diffusion theory, we computed an absorption coefficient (K). The values of K increased with increasing airflow, implying that ozone absorption is limited by diffusion processes in the airway lumen as well as in the surrounding tissue.

A new differential absorption lidar to measure sub-hourly fluctuation of tropospheric ozone profiles in the Baltimore-Washington DC region

NASA Astrophysics Data System (ADS)

Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.; Twigg, L. W.; Hoff, R. M.

2014-04-01

Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99° N, 76.84° W, 57 m a.s.l.) from 400 m to 12 km a.g.l. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19% from 0-1.5 km, 10-18% from 1.5-3 km, and 11-25% from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area.

A New Differential Absorption Lidar to Measure Sub-Hourly Fluctuation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. Region

NASA Technical Reports Server (NTRS)

Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.; Twigg, L. W.; Hoff, R. M.

2014-01-01

Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99 N, 76.84 W, 57 meters ASL) from 400 m to 12 km AGL. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19 percent from 0-1.5 km, 10-18 percent from 1.5-3 km, and 11-25 percent from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area.

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

NASA Astrophysics Data System (ADS)

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 Research Foundation (project No. 07-05-00428).

Investigating Sources of Ozone over California Using AJAX Airborne Measurements and Models: Assessing the Contribution from Long Range Transport

NASA Technical Reports Server (NTRS)

Ryoo, Ju-Mee; Johnson, Matthew S.; Iraci, Laura T.; Yates, Emma L.; Gore, Warren

2017-01-01

High ozone (O3) concentrations at low altitudes (1.5e4 km) were detected from airborne Alpha Jet Atmospheric eXperiment (AJAX) measurements on 30 May 2012 off the coast of California (CA). We investigate the causes of those elevated O3 concentrations using airborne measurements and various models. GEOS-Chem simulation shows that the contribution from local sources is likely small. A back trajectory model was used to determine the air mass origins and how much they contributed to the O3 over CA. Low-level potential vorticity (PV) from Modern Era Retrospective analysis for Research and Applications 2 (MERRA-2) reanalysis data appears to be a result of the diabatic heating and mixing of airs in the lower altitudes, rather than be a result of direct transport from stratospheric intrusion. The Q diagnostic, which is a measure of the mixing of the air masses, indicates that there is sufficient mixing along the trajectory to indicate that O3 from the different origins is mixed and transported to the western U.S.The back-trajectory model simulation demonstrates the air masses of interest came mostly from the mid troposphere (MT, 76), but the contribution of the lower troposphere (LT, 19) is also significant compared to those from the upper troposphere/lower stratosphere (UTLS, 5). Air coming from the LT appears to be mostly originating over Asia. The possible surface impact of the high O3 transported aloft on the surface O3 concentration through vertical and horizontal transport within a few days is substantiated by the influence maps determined from the Weather Research and Forecasting Stochastic Time Inverted Lagrangian Transport (WRF-STILT) model and the observed increases in surface ozone mixing ratios. Contrasting this complex case with a stratospheric-dominant event emphasizes the contribution of each source to the high O3 concentration in the lower altitudes over CA. Integrated analyses using models, reanalysis, and diagnostic tools, allows high ozone values detected by in-situ measurements to be attributed to multiple source processes.

Analysis of Ozone in Cloudy Versus Clear Sky Conditions

NASA Technical Reports Server (NTRS)

Strode, Sarah; Douglass, Anne; Ziemke, Jerald

2016-01-01

Convection impacts ozone concentrations by transporting ozone vertically and by lofting ozone precursors from the surface, while the clouds and lighting associated with convection affect ozone chemistry. Observations of the above-cloud ozone column (Ziemke et al., 2009) derived from the OMI instrument show geographic variability, and comparison of the above-cloud ozone with all-sky tropospheric ozone columns from OMI indicates important regional differences. We use two global models of atmospheric chemistry, the GMI chemical transport model (CTM) and the GEOS-5 chemistry climate model, to diagnose the contributions of transport and chemistry to observed differences in ozone between areas with and without deep convection, as well as differences in clean versus polluted convective regions. We also investigate how the above-cloud tropospheric ozone from OMI can provide constraints on the relationship between ozone and convection in a free-running climate simulation as well as a CTM.

The impact of historical land use change from 1850 to 2000 on secondary particulate matter and ozone

NASA Astrophysics Data System (ADS)

Heald, Colette L.; Geddes, Jeffrey A.

2016-12-01

Anthropogenic land use change (LUC) since preindustrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation. The general trend of expansion of managed ecosystems (croplands and pasturelands) at the expense of natural ecosystems has led to an 11 % decline in global mean biogenic volatile organic compound emissions. Concomitant growth in agricultural activity has more than doubled ammonia emissions and increased emissions of nitrogen oxides from soils by more than 50 %. Conversion to croplands has also led to a widespread increase in ozone dry deposition velocity. Together these changes in biosphere-atmosphere exchange have led to a 14 % global mean increase in biogenic secondary organic aerosol (BSOA) surface concentrations, a doubling of surface aerosol nitrate concentrations, and local changes in surface ozone of up to 8.5 ppb. We assess a global mean LUC-DRF of +0.017, -0.071, and -0.01 W m-2 for BSOA, nitrate, and tropospheric ozone, respectively. We conclude that the DRF and the perturbations in surface air quality associated with LUC (and the associated changes in agricultural emissions) are substantial and should be considered alongside changes in anthropogenic emissions and climate feedbacks in chemistry-climate studies.

The use of visible-channel data from NOAA satellites to measure total ozone amount over Antarctica

NASA Technical Reports Server (NTRS)

Boime, Robert D.; Warren, Steven G.; Gruber, Arnold

1994-01-01

Accurate, detailed maps of total ozone were not available until the launch of the Total Ozone Mapping Spectrometer (TOMS) in late 1978. However, the Scanning Radiometer (SR), an instrument on board the NOAA series satellites during the 1970s, had a visible channel that overlapped closely with the Chappuis absorption band of ozone. We are investigating whether data from the SR can be used to map Antarctic ozone prior to 1978. The method is being developed with 1980s data from the Advanced Very High Resolution Radiometer (AVHRR), which succeeded the SR on the NOAA polar-orbiting satellites. Visible-derived total ozone maps can then be compared able on the NOAA satellites, which precludes the use of a differential absorption technique to measure ozone. Consequently, our method works exclusively over scenes whose albedos are large and unvarying, i.e. scenes that contain ice sheets and/or uniform cloud-cover. Initial comparisons of time series for October-December 1987 at locations in East Antarctica show that the visible absorption by ozone in measurable and that the technique may be usable for the 1970s, but with much less accuracy than TOMS. This initial test assumes that clouds, snow, and ice all reflect the same percentage of visible light towards the satellite, regardless of satellite position or environmental conditions. This assumption is our greatest source of error. To improve the accuracy of ozone retrievals, realistic anisotropic reflectance factors are needed, which are strongly influenced by cloud and snow surface features.

Lower tropospheric ozone and aerosol measurements at a coastal mountain site in Central California

NASA Astrophysics Data System (ADS)

Post, A.; Faloona, I. C.; Lighthall, D.; Wexler, A. S.; Cliff, S. S.; Conley, S. A.; Zhao, Y.

2013-12-01

Increasing concern over the impacts of exogenous air pollution in California's Central Valley has prompted the establishment of a coastal, high altitude monitoring site at the Chews Ridge Observatory (1550 m) approximately 30 km east of Point Sur in Monterey County, operated by the Monterey Institute for Research in Astronomy. Eighteen months of ozone and aerosol measurements are presented in the context of long-range transport and its potential impact on surface air quality in the southern San Joaquin Valley. Moreover, several ozone surveys have been conducted by aircraft upwind, over the Pacific Ocean, and downwind, over the Central Valley, to characterize horizontal and vertical transport across the coastal mountains. Diurnal variations present at Chews Ridge indicate the formation of a convective boundary layer on the ridge during the daytime leading to a 6-8 ppb decrease in ozone accompanied by a rise in specific humidity of 2-3 g/kg due to coupling with the forest. During the nighttime, the sampled air masses are representative of free tropospheric conditions which have not been significantly influenced by either local emissions nor convective coupling to the surface. The maximum daily 8-hour average ozone concentration at Chews Ridge is used in lagged correlation analysis with two sites in the San Joaquin Valley, Fresno and Arvin, to de-emphasize the influence of locally produced, diurnally cycled ozone. The correlation coefficients (~0.60) peak between 9-21 hour lag and tend to decorrelate completely within 4-5 days. These and other analyses along with data provided by the aircraft sampling are used to provide a deeper understanding of ozone transport into the San Joaquin Valley. Aerosol size is measured with a scanning mobility particle sizer and composition is analyzed with an 8-stage rotating drum impactor whose substrates are characterized by X-ray fluorescence. Various elemental ratios and back trajectory calculations are used to infer the temporal patterns of influence that long range transport has on California air quality.

Development of a hybrid ozonation biofilm-membrane filatration process for the production of drinking water.

PubMed

Leiknes, T; Lazarova, M; Odegaard, H

2005-01-01

Drinking water sources in Norway are characterized by high concentrations of natural organic matter (NOM), low alkalinity and low turbidity. The removal of NOM is therefore a general requirement in producing potable water. Drinking water treatment plants are commonly designed with coagulation direct filtration or NF spiral wound membrane processes. This study has investigated the feasibility and potential of a hybrid process combining ozonation and biofiltration with a rotating disk membrane for treating drinking water with high NOM concentrations. Ozonation will oxidize the NOM content removing colour and form biodegradable organic compounds, which can be removed in biological filters. A constructed water was used in this study which is representative of ozonated NOM-containing water. A rotating membrane disk bioreactor downstream the ozonation process was used to carry out both the biodegradation as well as biomass separation in the same reactor. Maintenance of biodegradation of the organic matter while controlling biofouling of the membrane and acceptable water production rates was the focus in the study. Three operating modes were investigated. Removal of the biodegradable organics was consistent throughout the study indicating that sufficient biomass was maintained in the reactor for all operating conditions tested. Biofouling control was not achieved through shear-induced cleaning by periodically rotating the membrane disks at high speed. By adding a small amount of sponges in the membrane chamber the biofouling could be controlled by mechanical cleaning of the membrane surface during disk rotation. The overall results indicate that the system can favorably be used in an ozonation/biofiltration process by carrying out both biodegradation as well as biomass separation in the same reactor.

Influence of the Bermuda High on interannual variability of summertime ozone in the Houston-Galveston-Brazoria region

NASA Astrophysics Data System (ADS)

Wang, Yuxuan; Jia, Beixi; Wang, Sing-Chun; Estes, Mark; Shen, Lu; Xie, Yuanyu

2016-12-01

The Bermuda High (BH) quasi-permanent pressure system is the key large-scale circulation pattern influencing summertime weather over the eastern and southern US. Here we developed a multiple linear regression (MLR) model to characterize the effect of the BH on year-to-year changes in monthly-mean maximum daily 8 h average (MDA8) ozone in the Houston-Galveston-Brazoria (HGB) metropolitan region during June, July, and August (JJA). The BH indicators include the longitude of the BH western edge (BH-Lon) and the BH intensity index (BHI) defined as the pressure gradient along its western edge. Both BH-Lon and BHI are selected by MLR as significant predictors (p < 0.05) of the interannual (1990-2015) variability of the HGB-mean ozone throughout JJA, while local-scale meridional wind speed is selected as an additional predictor for August only. Local-scale temperature and zonal wind speed are not identified as important factors for any summer month. The best-fit MLR model can explain 61-72 % of the interannual variability of the HGB-mean summertime ozone over 1990-2015 and shows good performance in cross-validation (R2 higher than 0.48). The BH-Lon is the most important factor, which alone explains 38-48 % of such variability. The location and strength of the Bermuda High appears to control whether or not low-ozone maritime air from the Gulf of Mexico can enter southeastern Texas and affect air quality. This mechanism also applies to other coastal urban regions along the Gulf Coast (e.g., New Orleans, LA, Mobile, AL, and Pensacola, FL), suggesting that the BH circulation pattern can affect surface ozone variability through a large portion of the Gulf Coast.

An Assessment of Ground Level and Free Tropospheric Ozone Over California and Nevada

NASA Astrophysics Data System (ADS)

Yates, E. L.; Johnson, M. S.; Iraci, L. T.; Ryoo, J.-M.; Pierce, R. B.; Cullis, P. D.; Gore, W.; Ives, M. A.; Johnson, B. J.; Leblanc, T.; Marrero, J. E.; Sterling, C. W.; Tanaka, T.

2017-09-01

Increasing free tropospheric ozone (O3), combined with the high elevation and often deep boundary layers at western U.S. surface stations, poses challenges in attaining the more stringent 70 ppb O3 National Ambient Air Quality Standard. As such, use of observational data to identify sources and mechanisms that contribute to surface O3 is increasingly important. This work analyzes surface and vertical O3 observations over California and Nevada from 1995 to 2015. Over this period, the number of high O3 events (95th percentile) at the U.S. Environmental Protection Agency Clean Air Status and Trends Network (CASTNET) sites has decreased during summer, as a result of decreasing U.S. emissions. In contrast, an increase in springtime 5th percentile O3 indicates a general increase of baseline O3. During 2012 there was a peak in exceedances and in the average spring-summer O3 mixing ratios at CASTNET sites. Goddard Earth Observing System-Chem results show that the surface O3 attributable to transport from the upper troposphere and stratosphere was increased in 2013 compared to 2012, highlighting the importance of measurements aloft. Vertical O3 measurements from aircraft, ozonesondes, and lidar show distinct seasonal trends, with a high percentage of elevated O3 laminae (O3 > 70 ppb, 3-8 km) during spring and summer. Analysis of the timing of high O3 surface events and correlation between surface and vertical O3 data is used to discuss varying sources of western U.S. surface O3.

Modeling and Observations of the Response of Tropical Tropospheric Ozone to ENSO

NASA Technical Reports Server (NTRS)

Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Lang, C.; Rodriquez, J. M.; Nielsen, J. E.

2012-01-01

The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere, Recent results have revealed an ENSO induced wave-1 anomaly in observed tropical tropospheric column ozone, This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years, An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region, We will show targeted comparisons with SHADOZ ozonesondes over these regions to provide insight into the vertical structure. Also, comparisons with NASA's Aura satellite Microwave Limb Sounder (MLS) and Tropospheric Emissions Spectrometer (TES) instruments and other appropriate data sets will be shown. In addition, the water vapor response to ENSO will be compared to help illuminate its role relative to dynamics in impacting ozone concentrations. These results indicate that the tropospheric ozone response to ENSO is potentially a very useful chemistry-climate diagnostic and should be considered in future modeling assessments.

The Impact of Warm Pool El Nino Events on Antarctic Ozone

NASA Technical Reports Server (NTRS)

Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

2011-01-01

Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

Winter Photochemistry Underlying High Ozone in an Oil and Gas Producing Region

NASA Astrophysics Data System (ADS)

Brown, S. S.; Edwards, P. M.; Roberts, J. M.; Ahmadov, R.; Banta, R. M.; De Gouw, J. A.; Dube, W. P.; Field, R. A.; Gilman, J.; Graus, M.; Helmig, D.; Koss, A.; Langford, A. O.; Lefer, B. L.; Lerner, B. M.; McKeen, S. A.; Li, S. M.; Murphy, S. M.; Parrish, D. D.; Senff, C. J.; Stutz, J.; Thompson, C. R.; Trainer, M.; Veres, P. R.; Warneke, C.; Wild, R. J.; Young, C.; Yuan, B.; Zamora, R. J.; Washenfelder, R. A.

2014-12-01

Ozone formation during wintertime in oil and gas producing basins of the Rocky Mountain West now accounts for some of the highest ozone pollutant concentrations observed in the U.S. These events are scientifically challenging, occurring only during cold, snow covered periods when meteorological inversions concentrate pollutants near the surface, but when incident solar actinic flux that initiates photochemical reactions is at or near its minimum. A near-explicit chemical model that incorporates detailed measurements obtained during three successive winter field studies in the Uintah Basin, Utah, accurately reproduces the observed buildup of ozone and other photochemically generated species. It also identifies the sources of free radicals that drive this unusual photochemistry, and quantifies their relative contributions. Although sharing the same basic atmospheric chemistry, winter ozone formation differs from its summertime, urban counterpart in its dependence upon the relative concentrations of volatile organic compounds (VOCs) and nitrogen oxide (NOx) precursors. Observed NO­­x mixing ratios in the Uintah basin are lower than is typical of urban areas, while VOC levels are significantly larger. These extreme VOC concentrations allow for nearly optimal efficiency of ozone production from the available NO­x. This analysis will inform the design of mitigation strategies and provide insight into the response of winter ozone to primary air pollutants in other regions, particularly those where oil and gas development is contemplated.

STRATEGIES AND TECHNOLOGY FOR MANAGING HIGH-CARBON ASH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert Hurt; Eric Suuberg; John Veranth

2002-09-10

The overall objective of the present project is to identify and assess strategies and solutions for the management of industry problems related to carbon in ash. Specific research issues to be addressed include: (1) the effect of parent fuel selection on ash properties and adsorptivity, including a first ever examination of the air entrainment behavior of ashes from alternative (non-coal) fuels; (2) the effect of various low-NOx firing modes on ash properties and adsorptivity; and (3) the kinetics and mechanism of ash ozonation. This data will provide scientific and engineering support of the ongoing process development activities. During this fourthmore » project period we completed the characterization of ozone-treated carbon surfaces and wrote a comprehensive report on the mechanism through which ozone suppresses the adsorption of concrete surfactants.« less

Ozone dissociation to oxygen affected by Criegee intermediate.

PubMed

Wei, Wen-Mei; Zheng, Ren-Hui; Pan, Yue-Li; Wu, Yun-Kai; Yang, Fan; Hong, Shi

2014-03-06

The detailed potential energy surfaces for the reactions of Criegee intermediate (CI, H2COO) and formaldehyde (H2CO) with ozone (O3) have been investigated at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311++G(2d,2p) level of theory, respectively. New alternative reaction mechanisms, to the one previously proposed (J. Phys. Chem. Lett. 2013, 4, 2525) have been found. The lower barrier of the new mechanism shows that it is easy for H2COO + O3 to dissociate to formaldehyde and oxygen. For the reactions of H2CO with O3 to produce H2COO and O2, we find relatively high energy barriers, which makes the ozone dissociation to oxygen unlikely to be catalyzed by CI.

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

NASA Astrophysics Data System (ADS)

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.

Surface Ozone Background in the United States: Canadian and Mexican Pollution Influences

EPA Science Inventory

We use a global chemical transport model (GEOS-Chem) with 1° x 1° horizontal resolution to quantify the effects of anthropogenic emissions from Canada, Mexico, and outside North America on daily maximum 8-h average ozone concentrations in U.S.surface air.

The corrosion effect of ozonated seawater solution on titanium in polymer generated crevice environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leveillee, S.Y.

1998-01-01

Two different tests were designed to evaluate the reaction of various polymers and grade-2 titanium in ozonated seawater in conjunction with a comparative analysis in an aerated seawater solution. The first was a weight loss test measuring the weight change of Polyvinyl chloride (PVC), Polyethylene and Teflon{trademark} in both ozonated and aerated artificial seawater baths. The second test was designed to induce crevice corrosion on the titanium test samples using various crevice generating materials in both ozonated and aerated solutions. The materials used to create the crevices were grade-2 titanium washers, PVC, Polyethylene, Saran and Teflon{trademark}. The weight loss testmore » showed that all three polymers lost weight in the ozonated bath. The results of the titanium washer crevice test provided no indication of corrosion or surface discoloration in either the ozonated or aerated solutions. Energy dispersive spectrometry (EDS) analysis found no fluorine, chlorine or other corrosion product. The PVC samples in the aerated bath also showed no signs of corrosion, but the PVC samples in the ozonated tank had light brown rings of surface discoloration. One of the ozonated PVC samples did show evidence of chlorine in the corrosion product. The outer circumference of the ozonated PVC washers exhibited the same type bleaching effect as in the weight loss samples, but the whitening of these samples were more pronounced. The polyethylene samples under aeration showed no discoloration or presence of fluorine or chlorine. The polyethylene crevice samples in the ozonated solution all exhibited the distinct brilliant blue color of titanium oxide. Fluorine was found in the corrosion product on only one of the samples. Chlorine was found on the surface of one of the other corrosion coupons. The results of the Teflon{trademark} crevice samples substantiated the previous Rensselaer study.« less

Stratospheric ozone depletion

PubMed Central

Rowland, F. Sherwood

2006-01-01

Solar ultraviolet radiation creates an ozone layer in the atmosphere which in turn completely absorbs the most energetic fraction of this radiation. This process both warms the air, creating the stratosphere between 15 and 50 km altitude, and protects the biological activities at the Earth's surface from this damaging radiation. In the last half-century, the chemical mechanisms operating within the ozone layer have been shown to include very efficient catalytic chain reactions involving the chemical species HO, HO2, NO, NO2, Cl and ClO. The NOX and ClOX chains involve the emission at Earth's surface of stable molecules in very low concentration (N2O, CCl2F2, CCl3F, etc.) which wander in the atmosphere for as long as a century before absorbing ultraviolet radiation and decomposing to create NO and Cl in the middle of the stratospheric ozone layer. The growing emissions of synthetic chlorofluorocarbon molecules cause a significant diminution in the ozone content of the stratosphere, with the result that more solar ultraviolet-B radiation (290–320 nm wavelength) reaches the surface. This ozone loss occurs in the temperate zone latitudes in all seasons, and especially drastically since the early 1980s in the south polar springtime—the ‘Antarctic ozone hole’. The chemical reactions causing this ozone depletion are primarily based on atomic Cl and ClO, the product of its reaction with ozone. The further manufacture of chlorofluorocarbons has been banned by the 1992 revisions of the 1987 Montreal Protocol of the United Nations. Atmospheric measurements have confirmed that the Protocol has been very successful in reducing further emissions of these molecules. Recovery of the stratosphere to the ozone conditions of the 1950s will occur slowly over the rest of the twenty-first century because of the long lifetime of the precursor molecules. PMID:16627294

Arctic spring ozone reduction associated with projected sea ice loss

NASA Astrophysics Data System (ADS)

Deser, C.; Sun, L.; Tomas, R. A.; Polvani, L. M.

2013-12-01

The impact of Arctic sea ice loss on the stratosphere is investigated using the Whole-Atmosphere Community Climate Model (WACCM), by prescribing the sea ice in the late 20th century and late 21st century, respectively. The localized Sea Surface Temperature (SST) change associated with sea ice melt is also included in the future run. Overall, the model simulates a negative annular-mode response in the winter and spring. In the stratosphere, polar vortex strengthens from February to April, peaking in March. Consistent with it, there is an anomalous cooling in the high-latitude stratosphere, and polar cap ozone reduction is up to 20 DU. Since the difference between these two runs lies only in the sea ice and localized SST in the Arctic, the stratospheric circulation and ozone changes can be attributed to the surface forcing. Eliassen-Palm analysis reveals that the upward propagation of planetary waves is suppressed in the spring as a consequence of sea ice loss. The reduction in propagation causes less wave dissipation and thus less zonal wind deceleration in the extratropical stratosphere.

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing

PubMed Central

Marshall, John; Armour, Kyle C.; Scott, Jeffery R.; Kostov, Yavor; Hausmann, Ute; Ferreira, David; Shepherd, Theodore G.; Bitz, Cecilia M.

2014-01-01

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around ‘climate response functions’ (CRFs), i.e. the response of the climate to ‘step’ changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate. PMID:24891392

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing.

PubMed

Marshall, John; Armour, Kyle C; Scott, Jeffery R; Kostov, Yavor; Hausmann, Ute; Ferreira, David; Shepherd, Theodore G; Bitz, Cecilia M

2014-07-13

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around 'climate response functions' (CRFs), i.e. the response of the climate to 'step' changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate.