Simulations of photochemical smog formation in complex urban areas

NASA Astrophysics Data System (ADS)

Muilwijk, C.; Schrijvers, P. J. C.; Wuerz, S.; Kenjereš, S.

2016-12-01

In the present study we numerically investigated the dispersion of photochemical reactive pollutants in complex urban areas by applying an integrated Computational Fluid Dynamics (CFD) and Computational Reaction Dynamics (CRD) approach. To model chemical reactions involved in smog generation, the Generic Reaction Set (GRS) approach is used. The GRS model was selected since it does not require detailed modeling of a large set of reactive components. Smog formation is modeled first in the case of an intensive traffic emission, subjected to low to moderate wind conditions in an idealized two-dimensional street canyon with a building aspect ratio (height/width) of one. It is found that Reactive Organic Components (ROC) play an important role in the chemistry of smog formation. In contrast to the NOx/O3 photochemical steady state model that predicts a depletion of the (ground level) ozone, the GRS model predicts generation of ozone. Secondly, the effect of direct sunlight and shadow within the street canyon on the chemical reaction dynamics is investigated for three characteristic solar angles (morning, midday and afternoon). Large differences of up to one order of magnitude are found in the ozone production for different solar angles. As a proof of concept for real urban areas, the integrated CFD/CRD approach is applied for a real scale (1 × 1 km2) complex urban area (a district of the city of Rotterdam, The Netherlands) with high traffic emissions. The predicted pollutant concentration levels give realistic values that correspond to moderate to heavy smog. It is concluded that the integrated CFD/CRD method with the GRS model of chemical reactions is both accurate and numerically robust, and can be used for modeling of smog formation in complex urban areas.

Field measurements of the ambient ozone formation potential in Beijing during winter

NASA Astrophysics Data System (ADS)

Crilley, Leigh; Kramer, Louisa; Thomson, Steven; Lee, James; Squires, Freya; Bloss, William

2017-04-01

The air quality issues in Beijing have been well-documented, and the severe air pollution levels result in a unique chemical mix in the urban boundary layer, both in terms of concentration and composition. As many of the atmospheric chemical process are non-linear and interlinked, this makes predictions difficult for species formed in atmosphere, such as ozone, requiring field measurements to understand these processes in order to guide mitigation efforts. To investigate the ozone formation potential of ambient air, we employed a custom built instrument to measure in near real time the potential for in situ ozone production, using an artificial light source. Our results are thus indicative of the ozone formation potential for the sampled ambient air mixture. Measurements were performed as part of the Air Pollution and Human Health (APHH) field campaign in November / December 2016 at a suburban site in central Beijing. We also conducted experiments to examine the ozone production sensitivity to NOx. We will present preliminarily results from ambient sampling and NOx experiments demonstrating changes in the ozone production potential during clean and haze periods in Beijing.

Gas-Phase Formation Rates of Nitric Acid and Its Isomers Under Urban Conditions

NASA Technical Reports Server (NTRS)

Okumura, M.; Mollner, A. K.; Fry, J. L.; Feng, L.

2005-01-01

Ozone formation in urban smog is controlled by a complex set of reactions which includes radical production from photochemical processes, catalytic cycles which convert NO to NO2, and termination steps that tie up reactive intermediates in long-lived reservoirs. The reaction OH + NO2 + M -4 HONO2 + M (la) is a key termination step because it transforms two short-lived reactive intermediates, OH and NO2, into relatively long-lived nitric acid. Under certain conditions (low VOC/NOx), ozone production in polluted urban airsheds can be highly sensitive to this reaction, but the rate parameters are not well constrained. This report summarizes the results of new laboratory studies of the OH + NO2 + M reaction including direct determination of the overall rate constant and branching ratio for the two reaction channels under atmospherically relevant conditions.

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.

Contribution of low vapor pressure-volatile organic compounds (LVP-VOCs) from consumer products to ozone formation in urban atmospheres

NASA Astrophysics Data System (ADS)

Shin, Hyeong-Moo; McKone, Thomas E.; Bennett, Deborah H.

2015-05-01

Because recent laboratory testing indicates that some low vapor pressure-volatile organic compounds (LVP-VOC) solvents readily evaporate at ambient conditions, LVP-VOCs used in some consumer product formulations may contribute to ozone formation. The goal of this study is to determine the fraction of LVP-VOCs available for ozone formation from the use of consumer products for two hypothetical emissions. This study calculates and compares the fraction of consumed product available for ozone formation as a result of (a) volatilization to air during use and (b) down-the-drain disposal. The study also investigates the impact of different modes of releases on the overall fraction available in ambient air for ozone formation. For the portion of the LVP-VOCs volatilized to air during use, we applied a multi-compartment mass-balance model to track the fate of emitted LVP-VOCs in a multimedia urban environment. For the portion of the LVP-VOCs disposed down the drain, we used a wastewater treatment plant (WWTP) fate model to predict the emission rates of LVP-VOCs to ambient air at WWTPs or at the discharge zone of the facilities and then used these results as emissions in the multimedia urban environment model. In a WWTP, the LVP-VOCs selected in this study are primarily either biodegraded or removed via sorption to sludge depending on the magnitude of the biodegradation half-life and the octanol-water partition coefficient. Less than 0.2% of the LVP-VOCs disposed down the drain are available for ozone formation. In contrast, when the LVP-VOC in a consumer product is volatilized from the surface to which it has been applied, greater than 90% is available for photochemical reactions either at the source location or in the downwind areas. Comparing results from these two modes of releases allows us to understand the importance of determining the fraction of LVP-VOCs volatilized versus disposed down the drain when the product is used by consumers. The results from this study provide important information and modeling tools to evaluate the impact of LVP-VOCs on air quality and suggest the need for future research on emissions of LVP-VOCs at the point of use.

The changing oxidizing environment in London - trends in ozone precursors and their contribution to ozone production

NASA Astrophysics Data System (ADS)

von Schneidemesser, E.; Vieno, M.; Monks, P. S.

2014-01-01

Ground-level ozone is recognized to be a threat to human health (WHO, 2003), have a deleterious impact on vegetation (Fowler et al., 2009), is also an important greenhouse gas (IPCC, 2007) and key to the oxidative ability of the atmosphere (Monks et al., 2009). Owing to its harmful effect on health, much policy and mitigation effort has been put into reducing its precursors - the nitrogen oxides (NOx) and non-methane volatile organic compounds (NMVOCs). The non-linear chemistry of tropospheric ozone formation, dependent mainly on NOx and NMVOC concentrations in the atmosphere, makes controlling tropospheric ozone complex. Furthermore, the concentration of ozone at any given point is a complex superimposition of in-situ produced or destroyed ozone and transported ozone on the regional and hemispheric-scale. In order to effectively address ozone, a more detailed understanding of its origins is needed. Here we show that roughly half (5 μg m-3) of the observed increase in urban (London) ozone (10 μg m-3) in the UK from 1998 to 2008 is owing to factors of local origin, in particular, the change in NO : NO2 ratio, NMVOC : NOx balance, NMVOC speciation, and emission reductions (including NOx titration). In areas with previously higher large concentrations of nitrogen oxides, ozone that was previously suppressed by high concentrations of NO has now been "unmasked", as in London and other urban areas of the UK. The remaining half (approximately 5 μg m-3) of the observed ozone increase is attributed to non-local factors such as long-term transport of ozone, changes in background ozone, and meteorological variability. These results show that a two-pronged approach, local action and regional-to-hemispheric cooperation, is needed to reduce ozone and thereby population exposure, which is especially important for urban ozone.

Natural hydrocarbons, urbanization, and urban ozone

NASA Technical Reports Server (NTRS)

Cardelino, C. A.; Chameides, W. L.

1990-01-01

The combined effects of emission control and urbanization, with its concomitant intensification of the urban heat island, on urban ozone concentrations are studied. The effect of temperature on ozone is considered, and attention is given to the temperature effect on ozone photochemistry. Model calculations suggest that ozone concentration enhancements are caused by the effect of temperature on the atmospheric chemistry of peroxyacetyl nitrate, as well as the temperature dependence of natural and anthropogenic hydrocarbon emissions. It is pointed out that, because of the sensitivity of urban ozone to local climatic conditions and the ability of trees to moderate summertime temperatures, the inadvertent removal of trees from urbanization can have an adverse effect on urban ozone concentration, while a temperature increase in the urban heat island caused by urbanization can essentially cancel out the ozone-reducing benefits obtained from a 50-percent reduction in anthropogenic hydrocarbon emissions.

Urban Climate Effects on Air Pollution and Atmospheric Chemistry

NASA Astrophysics Data System (ADS)

Rasoul, Tara; Bloss, William; Pope, Francis

2016-04-01

Tropospheric ozone, adversely affects the environment and human health. The presence of chlorine nitrate (ClNO2) in the troposphere can enhance ozone (O3) formation as it undergoes photolysis, releasing chlorine reactive atoms (Cl) and nitrogen dioxide (NO2), both of which enhance tropospheric ozone formation. The importance of new sources of tropospheric ClNO2 via heterogeneous processes has recently been highlighted. This study employed a box model, using the Master Chemical Mechanism (MCM version 3.2) to assess the effect of ClNO2 on air quality in urban areas within the UK. The model updated to include ClNO2 production, photolysis, a comprehensive parameterisation of dinitrogen pentoxide (N2O5) uptake, and ClNO2 production calculated from bulk aerosol composition. The model simulation revealed the presence of ClNO2 enhances the formation of NO2, organic peroxy radical (CH3O2), O3, and hydroxyl radicals (OH) when compared with simulations excluding ClNO2. In addition, the study examined the effect of temperature variation upon ClNO2 formation. The response of ClNO2 to temperature was analysed to identify the underlying drivers, of particular importance when assessing the response of atmospheric chemistry processes under potential future climates.

Effect of heat waves on VOC emissions from vegetation and urban air quality

NASA Astrophysics Data System (ADS)

Churkina, G.; Kuik, F.; Lauer, A.; Bonn, B.; Butler, T. M.

2015-12-01

Programs to plant millions of trees in cities around the world aim at the reduction of summer temperatures, increase carbon storage, storm water control, provision of space for recreation, as well as poverty alleviation. Although these multiple benefits speak positively for urban greening programs, the programs do not take into account how close human and natural systems are coupled in urban areas. Elevated temperatures together with anthropogenic emissions of air and water pollutants distinguish the urban system. Urban and sub-urban vegetation responds to ambient changes and reacts with pollutants. Neglecting this coupling may lead to unforeseen drawbacks of urban greening programs. The potential for emissions of volatile organic compounds (VOC) from vegetation combined with anthropogenic emissions to produce ozone has long been recognized. This potential increases under rising temperatures. Here we investigate how heat waves affect emissions of VOC from urban vegetation and corresponding ground-level ozone. In this study we use Weather Research and Forecasting Model with coupled atmospheric chemistry (WRF-CHEM) to quantify these feedbacks in Berlin, Germany during the 2006 heat wave. VOC emissions from vegetation are simulated with MEGAN 2.0 coupled with WRF-CHEM. Our preliminary results indicate that contribution of VOCs from vegetation to ozone formation may increase by more than twofold during the heat wave period. We highlight the importance of the vegetation for urban areas under changing climate and discuss associated tradeoffs.

Estimating changes in urban ozone concentrations due to life cycle emissions from hydrogen transportation systems

NASA Astrophysics Data System (ADS)

Wang, Guihua; Ogden, Joan M.; Chang, Daniel P. Y.

Hydrogen has been proposed as a low polluting alternative transportation fuel that could help improve urban air quality. This paper examines the potential impact of introducing a hydrogen-based transportation system on urban ambient ozone concentrations. This paper considers two scenarios, where significant numbers of new hydrogen vehicles are added to a constant number of gasoline vehicles. In our scenarios hydrogen fuel cell vehicles (HFCVs) are introduced in Sacramento, California at market penetrations of 9% and 20%. From a life cycle analysis (LCA) perspective, considering all the emissions involved in producing, transporting, and using hydrogen, this research compares three hypothetical natural gas to hydrogen pathways: (1) on-site hydrogen production; (2) central hydrogen production with pipeline delivery; and (3) central hydrogen production with liquid hydrogen truck delivery. Using a regression model, this research shows that the daily maximum temperature correlates well with atmospheric ozone formation. However, increases in initial VOC and NO x concentrations do not necessarily increase the peak ozone concentration, and may even cause it to decrease. It is found that ozone formation is generally limited by NO x in the summer and is mostly limited by VOC in the fall in Sacramento. Of the three hydrogen pathways, the truck delivery pathway contributes the most to ozone precursor emissions. Ozone precursor emissions from the truck pathway at 9% market penetration can cause additional 3-h average VOC (or NO x) concentrations up to approximately 0.05% (or 1%) of current pollution levels, and at 20% market penetration up to approximately 0.1% (or 2%) of current pollution levels. However, all of the hydrogen pathways would result in very small (either negative or positive) changes in ozone air quality. In some cases they will result in worse ozone air quality (mostly in July, August, and September), and in some cases they will result in better ozone air quality (mostly in October). The truck pathway tends to cause a much wider fluctuation in degradation or improvement of ozone air quality: percentage changes in peak ozone concentrations are approximately -0.01% to 0.04% for the assumed 9% market penetration, and approximately -0.03% to 0.1% for the 20% market penetration. Moreover, the 20% on-site pathway occasionally results in a decrease of about -0.1% of baseline ozone pollution. Compared to the current ambient pollution level, all three hydrogen pathways are unlikely to cause a serious ozone problem for market penetration levels of HFCVs in the 9-20% range.

Direct measurements of the ozone formation potential from livestock and poultry waste emissions.

PubMed

Howard, Cody J; Kumar, Anuj; Mitloehner, Frank; Stackhouse, Kimberly; Green, Peter G; Flocchini, Robert G; Kleeman, Michael J

2010-04-01

The global pattern of expanding urban centers and increasing agricultural intensity is leading to more frequent interactions between air pollution emissions from urban and agricultural sources. The confluence of these emissions that traditionally have been separated by hundreds of kilometers is creating new air quality challenges in numerous regions across the United States. An area of particular interest is California's San Joaquin Valley (SJV), which has an agricultural output higher than many countries, a rapidly expanding human population, and ozone concentrations that are already higher than many dense urban areas. New regulations in the SJV restrict emissions of reactive organic gases (ROGs) from animal sources in an attempt to meet Federal and State ozone standards designed to protect human health. The objective of this work is to directly measure the ozone formation potential (OFP) of agricultural animal plus waste sources in representative urban and rural atmospheres using a transportable "smog" chamber. Four animal types were examined: beef cattle, dairy cattle, swine, and poultry. Emissions from each animal plus waste type were captured in a 1 m(3) Teflon bag, mixed with representative background NO(x) and ROG concentrations, and then exposed to UV radiation so that ozone formation could be quantified. The emitted ROG composition was also measured so that the theoretical incremental reactivity could be calculated for a variety of atmospheres and directly compared with the measured OFP under the experimental conditions. The results demonstrate that OFP associated with waste ROG emissions from swine (0.39 +/- 0.04 g-O(3) per g-ROG), beef cattle (0.51 +/- 0.10 g-O(3) per g-ROG), and dairy cattle (0.42 +/- 0.07 g-O(3) per g-ROG) are lower than OFP associated with ROG emissions from gasoline powered light-duty vehicles (LDV) (0.69 +/- 0.05 g-O(3) per g-ROG). The OFP of ROG emitted from poultry waste (1.35 +/- 0.73 g-O(3) per g-ROG) is approximately double the LDV OFP. The measured composition of ROG emitted from animal plus waste sources is nine times less reactive than the current regulatory profiles that are based on dated measurements. The new animal waste ROG OFP measurements combined with adjusted animal waste ROG emissions inventory estimates predict that actual ozone production in the SJV from livestock and poultry (5.7 +/- 1.3 tons O(3) day(-1)) is 40 +/- 10% of the ozone produced by light duty gasoline vehicles (14.3 +/- 1.4 tons O(3) day(-1)) under constant NO(x) conditions.

Modeling the Impact of CINO2 on Ozone Formation in the Houston Area

EPA Science Inventory

During the summer of 2006, nitryl chloride (ClNO₂) mixing ratios of over 1 ppb were measured in the Houston urban area. Nitryl chloride is potentially important to atmospheric chemistry in urban environments because its photolysis products include both NO₂ a...

A modeling study of the impact of urban trees on ozone

Treesearch

David J. Nowak; Kevin L. Civerolo; S. Trivikrama Rao; Gopal Sistla; Christopher J. Luley; Daniel E. Crane

2000-01-01

Modeling the effects of increased urban tree cover on ozone concentrations (July 13-15, 1995) from Washington, DC, to central Massachusetts reveals that urban trees generally reduce ozone concentrations in cities, but tend to increase average ozone concentrations in the overall modeling domain. During the daytime, average ozone reductions in urban areas (1 ppb) were...

Impacts of biogenic and anthropogenic emissions on summertime ozone formation in the Guanzhong Basin, China

NASA Astrophysics Data System (ADS)

Li, Nan; He, Qingyang; Greenberg, Jim; Guenther, Alex; Li, Jingyi; Cao, Junji; Wang, Jun; Liao, Hong; Wang, Qiyuan; Zhang, Qiang

2018-05-01

This study is the first attempt to understand the synergistic impact of anthropogenic and biogenic emissions on summertime ozone (O3) formation in the Guanzhong (GZ) Basin where Xi'an, the oldest and the most populous city (with a population of 9 million) in northwestern China, is located. Month-long (August 2011) WRF-Chem simulations with different sensitivity experiments were conducted and compared with near-surface measurements. Biogenic volatile organic compounds (VOCs) concentrations was characterized from six surface sites among the Qinling Mountains, and urban air composition was measured in Xi'an city at a tower 100 m a. s. The WRF-Chem control experiment reasonably reproduced the magnitudes and variations of observed O3, VOCs, NOx, PM2.5, and meteorological parameters, with normalized mean biases for each parameter within ±21 %. Subsequent analysis employed the factor separation approach (FSA) to quantitatively disentangle the pure and synergistic impacts of anthropogenic and/or biogenic sources on summertime O3 formation. The impact of anthropogenic sources alone was found to be dominant for O3 formation. Although anthropogenic particles reduced NO2 photolysis by up to 60 %, the anthropogenic sources contributed 19.1 ppb O3 formation on average for urban Xi'an. The abundant biogenic VOCs from the nearby forests promoted O3 formation in urban areas by interacting with the anthropogenic NOx. The calculated synergistic contribution (from both biogenic and anthropogenic sources) was up to 14.4 ppb in urban Xi'an, peaking in the afternoon. Our study reveals that the synergistic impact of individual source contributions to O3 formation should be considered in the formation of air pollution control strategies, especially for big cities in the vicinity of forests.

The study of ozone variations in the Las Vegas metropolitan area using remote sensing information and ground observations

USGS Publications Warehouse

Xian, G.; Crane, M.

2006-01-01

Urban development in the Las Vegas Valley, Nevada, has grown rapidly in the past fifty years. Associated with this growth has been a change in landscape from natural cover types to developed urban land mixed with planned vegetation canopy throughout in the metropolitan area. Air quality in the Las Vegas Valley has been affected by increases in anthropogenic emissions and concentrations of carbon monoxide, ozone, and criteria pollutants of particular matter. Ozone concentration in the region is generally influenced by synoptic and mesoscale meteorological conditions, as well as regional transport of pollutants from the western side of Las Vegas. Local influences from ground-level nitrogen oxide emissions and vegetation canopy coverage also affect ozone concentration. Multi-year observational data collected by a network of local air monitoring stations in Clark County, Nevada, indicate that ozone maximums develop in May and June, while minimums exist primarily from November to February. Ozone concentrations are high on the west and northwest sides of the valley. A nighttime ozone reduction in the urban area characterizes the heterogeneous features of spatial distribution for average ozone levels in the Las Vegas urban area. The urban vegetation canopy has a locally positive effect by reducing ozone in urban areas. Decreased ozone levels associated with increased urban development density suggests that the highest ozone concentrations are associated with medium- to low-density urban development in Las Vegas.

[Chemical Loss of Volatile Organic Compounds and Its Impact on the Formation of Ozone in Shanghai].

PubMed

Wang, Hong-li

2015-09-01

The spatial characterization of ozone (O3) and its precursors was studied based on the field measurements in urban and rural areas of Shanghai during the summer of 2014. The chemical loss of volatile organic compounds (VOCs) was estimated by the parameterization method. The mixing ratio of VOCs was 20 x 10(-9) in urban area and 17 x 10(-9) in the west rural area during the measurements. The average values of the maximum incremental reactivity were comparable in urban and rural areas, namely 5. 0 mol.mol-1 (O3/VOCs). By contrast, the chemical loss of VOCs was 8. 3 x 10(-9) in west rural area, which was two times as that in urban area. The more chemical loss of VOCs was probably one of the important reasons leading to the higher O3 concentration in west rural area. The regional transport might be important reason of the variation of O3 in the eastern coastal rural area. The chemical loss of VOCs showed good agreement with the local formation of O3 in both urban and rural areas, suggesting a similar efficiency of O3 formation from the chemical loss of VOCs. Among the chemical loss, aromatics and alkenes are the dominant VOC species of the atmospheric chemistry which accounts for more than 90% . The diurnal profile of VOC chemical loss matched well with the production of O3 with one-hour postponement.

Removal of Ozone by Urban and Peri-Urban Forests: Evidence from Laboratory, Field, and Modeling Approaches

Treesearch

Carlo Calfapietra; Arianna Morani; Gregorio Sgrigna; Sara Di Giovanni; Valerio Muzzini; Emanuele Pallozzi; Gabriele Guidolotti; David Nowak; Silvano Fares

2016-01-01

A crucial issue in urban environments is the interaction between urban trees and atmospheric pollution, particularly ozone (O3). Ozone represents one of the most harmful pollutants in urban and peri-urban environments, especially in warm climates. Besides the large interest in reducing anthropogenic and biogenic precursors of O3...

Ozone production during an urban air stagnation episode over Nashville, Tennessee

NASA Astrophysics Data System (ADS)

Valente, R. J.; Imhoff, R. E.; Tanner, R. L.; Meagher, J. F.; Daum, P. H.; Hardesty, R. M.; Banta, R. M.; Alvarez, R. J.; McNider, R. T.; Gillani, N. V.

1998-09-01

The highest O3 levels observed during the 1995 Southern Oxidants Study in middle Tennessee occurred during a period of air stagnation from July 11 through July 15. Extensive airborne (two fixed wing and one helicopter) and ground-based measurements of the chemistry and meteorology of this episode near Nashville, Tennessee, are presented. In situ airborne measurements include O3, NOy, NO, NO2, SO2, CO, nitrate, hydrocarbons, and aldehydes. Airborne LIDAR O3 measurements are also utilized to map the vertical and horizontal extent of the urban plume. The use of multiple instrumented research aircraft permitted highly detailed mapping of the plume chemistry in the vertical and horizontal dimensions. Interactions between the urban Nashville plume (primarily a NOx and hydrocarbon source) and the Gallatin coal-fired power plant plume (primarily a NOx and SO2 source) are also documented, and comparisons of ozone formation in the isolated and mixed urban and power plant plume are presented. The data suggest that during this episode the background air and the edges of the urban plume are NOx sensitive and the core of the urban plume is hydrocarbon sensitive. Under these worst case meteorological conditions, ambient O3 levels well over the level of the new National Ambient Air Quality Standard (NAAQS) for ozone (80 ppb) were observed over and just downwind of Nashville. For example, on July 12, the boundary layer air upwind of Nashville showed 60 to 70 ppb O3, while just downwind of the city the urban plume maximum was over 140 ppb O3. With a revised ozone standard set at 80 ppb (8 hour average) and upwind levels already within 10 or 20 ppb of the standard, only a slight increase in ozone from the urban area will cause difficulty in attaining the standard at monitors near the core of the urban plume during this type of episode. The helicopter mapping and LIDAR aircraft data clearly illustrate that high O3 levels can occur during stagnation episodes within a few kilometers of and even within the urban area. The extremely light boundary layer winds (1-3 m s-1) contributed to the creation of an ozone dome or blob which stayed very near to the city rather than an elongated plume. The small spatial scale of the zone of high O3 concentrations is mapped in detail demonstrating that the regulatory monitoring network failed to document the maximum O3 concentrations. Modelers using such regulatory data to test photochemical algorithms need to bear in mind that magnitude and frequency of urban ozone may be underestimated by monitoring networks, especially in medium-sized urban areas under slow transport conditions. Finally, this effort shows the value of collaborative field measurements from multiple platforms in developing a more complete picture of the chemistry and transport of photochemical O3.

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.

Aerosol indirect effects on lightning in the generation of induced NOx and tropospheric ozone over an Indian urban metropolis

NASA Astrophysics Data System (ADS)

Saha, Upal; Maitra, Animesh; Talukdar, Shamitaksha; Jana, Soumyajyoti

Lightning flashes, associated with vigorous convective activity, is one of the most prominent weather phenomena in the tropical atmosphere. High aerosol loading is indirectly associated with the increase in lightning flash rates via the formation of tropospheric ozone during the pre-monsoon and monsoon over the tropics. Tropospheric ozone, an important greenhouse pollutant gas have impact on Earth’s radiation budget and play a key role in changing the atmospheric circulation patterns. Lightning-induced NOx is a primary pollutant found in photochemical smog and an important precursor for the formation of tropospheric ozone. A critical analysis is done to study the indirect effects of high aerosol loading on the formation of tropospheric ozone via lightning flashes and induced NOx formation over an urban metropolitan location Kolkata (22°32'N, 88°20'E), India during the period 2001-2012. The seasonal variation of lightning flash rates (LFR), taken from TRMM-LIS 2.5o x 2.5o gridded dataset, show that the LFR was observed to be intensified in the pre-monsoon (March-May) and high in monsoon (June-September) months over the region. Aerosol Optical Depth (AOD) at 555nm, taken from MISR 0.5o x 0.5o gridded level-3 dataset, plays an indirect effect on the increase in LFR during the pre-monsoon and monsoon months and has positive correlations between them during these periods. This is also justified from the seasonal variation of the increase in LFR due to the increase in AOD over the region during 2001-2012. The calibrated GOME and OMI/AURA satellite data analysis shows that the tropospheric ozone, formed as a result of lightning-induced NOx and due to the increased AOD at 555 nm, also increases during the pre-monsoon and monsoon months. The seasonal variation of lightning-induced tropospheric NOx, taken from SCIAMACHY observations also justified the fact that the pre-monsoon and monsoon LFR solely responsible for the generation of induced NOx over the region. The increase in lightning activity is caused by the indirect influx of aerosols, especially in the upper troposphere. This is due to the warming-effect of aerosol forcing via its effect on tropospheric ozone production. Due to the increased production of O3 by lightning-induced NOx and high aerosol loading in the pre-monsoon and monsoon months, the positive climate feedback indicates a warmer climate. As a consequence, convective activity as well as lightning flashes may increase due to this indirect effect of AOD over the region. The generation of induced NOx has a positive correlation (r = 0.723) with the LFR during 2001-2012 over Kolkata. Thus, our results have significant implications for understanding the tropospheric ozone forcing by investigating the coupled aerosol-cloud-chemistry system on the generation of lightning and lightning-induced NOx over the urban metropolis.

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.

Spatiotemporal variation of ozone precursors and ozone formation in Hong Kong: Grid field measurement and modelling study.

PubMed

Lyu, X P; Liu, M; Guo, H; Ling, Z H; Wang, Y; Louie, P K K; Luk, C W Y

2016-11-01

Grid field measurements of volatile organic compounds (VOCs) covering the entire territory of Hong Kong were simultaneously carried out twice daily on 27 September 2013 and 24 September 2014, respectively, to advance our understanding on the spatiotemporal variations of VOCs and ozone (O3) formation, the factors controlling O3 formation and the efficacy of a control measure in Hong Kong. From before to after the control measure on liquefied petroleum gas (LPG) fueled vehicles, the VOCs originated from LPG vehicle exhaust deceased from 41.3±1.2μg/m(3) (49.7±1.5%) to 32.8±1.4μg/m(3) (38.8±1.7%) (p<0.05). In contrast, the contribution to VOCs made by gasoline and diesel vehicle exhaust and solvent usage increased (p<0.05). VOCs and nitric oxide (NO) in LPG source experienced the highest reductions at the roadside sites, while the variations were not significant at the urban and new town sites (p>0.05). For O3 production, LPG vehicle exhaust generally made a negative contribution (-0.17±0.06 ppbv) at the roadside sites, however it turned to a slightly positive contribution (0.004±0.038 ppbv) after the control measure. At the urban sites, although the reductions of VOCs and NO were minor (p>0.05), O3 produced by LPG vehicle significantly reduced from 4.19±1.92 ppbv to 0.95±0.38 ppbv (p<0.05). Meanwhile, O3 produced by LPG at the new town sites remained stable. The analysis of O3-precursor relationships revealed that alkenes and aromatics were the main species limiting roadside O3 formation, while aromatics were the most predominant controlling factor at urban and new town sites. In contrast, isoprene and sometimes NOx limited the O3 formation in rural environment. Copyright © 2016 Elsevier B.V. All rights reserved.

The influence of ocean halogen and sulfur emissions in the air quality of a coastal megacity: The case of Los Angeles.

PubMed

Muñiz-Unamunzaga, Maria; Borge, Rafael; Sarwar, Golam; Gantt, Brett; de la Paz, David; Cuevas, Carlos A; Saiz-Lopez, Alfonso

2018-01-01

The oceans are the main source of natural halogen and sulfur compounds, which have a significant influence on the oxidizing capacity of the marine atmosphere; however, their impact on the air quality of coastal cities is currently unknown. We explore the effect of marine halogens (Cl, Br and I) and dimethyl sulfide (DMS) on the air quality of a large coastal city through a set of high-resolution (4-km) air quality simulations for the urban area of Los Angeles, US, using the Community Multiscale Air Quality (CMAQ model). The results indicate that marine halogen emissions decrease ozone and nitrogen dioxide levels up to 5ppbv and 2.5ppbv, respectively, in the city of Los Angeles. Previous studies suggested that the inclusion of chlorine in air quality models leads to the generation of ozone in urban areas through photolysis of nitryl chloride (ClNO 2 ). However, we find that when considering the chemistry of Cl, Br and I together the net effect is a reduction of surface ozone concentrations. Furthermore, combined ocean emissions of halogens and DMS cause substantial changes in the levels of key urban atmospheric oxidants such as OH, HO 2 and NO 3 , and in the composition and mass of fine particles. Although the levels of ozone, NO 3 and HO x are reduced, we find a 10% increase in secondary organic aerosol (SOA) mean concentration, attributed to the increase in aerosol acidity and sulfate aerosol formation when combining DMS and bromine. Therefore, this new pathway for enhanced SOA formation may potentially help with current model under predictions of urban SOA. Although further observations and research are needed to establish these preliminary conclusions, this first city-scale investigation suggests that the inclusion of oceanic halogens and DMS in air quality models may improve regional air quality predictions over coastal cities around the world. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Temperature, ozone, and mortality in urban and non-urban counties in the northeastern United States.

PubMed

Madrigano, Jaime; Jack, Darby; Anderson, G Brooke; Bell, Michelle L; Kinney, Patrick L

2015-01-07

Most health effects studies of ozone and temperature have been performed in urban areas, due to the available monitoring data. We used observed and interpolated data to examine temperature, ozone, and mortality in 91 urban and non-urban counties. Ozone measurements were extracted from the Environmental Protection Agency's Air Quality System. Meteorological data were supplied by the National Center for Atmospheric Research. Observed data were spatially interpolated to county centroids. Daily internal-cause mortality counts were obtained from the National Center for Health Statistics (1988-1999). A two-stage Bayesian hierarchical model was used to estimate each county's increase in mortality risk from temperature and ozone. We examined county-level associations according to population density and compared urban (≥1,000 persons/mile(2)) to non-urban (<1,000 persons/mile(2)) counties. Finally, we examined county-level characteristics that could explain variation in associations by county. A 10 ppb increase in ozone was associated with a 0.45% increase in mortality (95% PI: 0.08, 0.83) in urban counties, while this same increase in ozone was associated with a 0.73% increase (95% PI: 0.19, 1.26) in non-urban counties. An increase in temperature from 70°F to 90°F (21.2°C 32.2°C) was associated with a 8.88% increase in mortality (95% PI: 7.38, 10.41) in urban counties and a 8.08% increase (95% PI: 6.16, 10.05) in non-urban counties. County characteristics, such as population density, percentage of families living in poverty, and percentage of elderly residents, partially explained the variation in county-level associations. While most prior studies of ozone and temperature have been performed in urban areas, the impacts in non-urban areas are significant, and, for ozone, potentially greater. The health risks of increasing temperature and air pollution brought on by climate change are not limited to urban areas.

Ozone levels in European and USA cities are increasing more than at rural sites, while peak values are decreasing.

PubMed

Paoletti, Elena; De Marco, Alessandra; Beddows, David C S; Harrison, Roy M; Manning, William J

2014-09-01

Ground-level ozone (O3) levels are usually lower in urban centers than nearby rural sites. To compare trends in O3 levels during the period 1990-2010, we obtained monitoring data from paired urban and rural sites from the European Environment Agency and the US Environmental Protection Agency. Ozone peaks decreased at both station types, with no significant differences between urban and rural stations. Ozone annual averages increased at both urban and rural sites, with a faster rate of increase for urban centers. The overall trend was for convergence between urban and rural O3 data. Ozone levels exceeded the criteria established for the protection of human and vegetation health at both urban and rural sites. Copyright © 2014 Elsevier Ltd. All rights reserved.

Life Cycle Assessment of Diesel and Electric Public Transportation Buses

EPA Science Inventory

The Clean Air Act identifies diesel powered motor vehicles, including transit buses, as significant sources of several criteria pollutants which contribute to ground level ozone formation or smog. The effects of air pollution in urban areas are often more significant due to con...

Tropospheric Ozone and Photochemical Smog

NASA Astrophysics Data System (ADS)

Sillman, S.

2003-12-01

The question of air quality in polluted regions represents one of the issues of geochemistry with direct implications for human well-being. Human health and well-being, along with the well-being of plants, animals, and agricultural crops, are dependent on the quality of air we breathe. Since the start of the industrial era, air quality has become a matter of major importance, especially in large cities or urbanized regions with heavy automobile traffic and industrial activity.Concern over air quality existed as far back as the 1600s. Originally, polluted air in cities resulted from the burning of wood or coal, largely as a source of heat. The industrial revolution in England saw a great increase in the use of coal in rapidly growing cities, both for industrial use and domestic heating. London suffered from devastating pollution events during the late 1800s and early 1900s, with thousands of excess deaths attributed to air pollution (Brimblecombe, 1987). With increasing use of coal, other instances also occurred in continental Europe and the USA. These events were caused by directly emitted pollutants (primary pollutants), including sulfur dioxide (SO2), carbon monoxide (CO), and particulates. They were especially acute in cities with northerly locations during fall and winter when sunlight is at a minimum. These original pollution events gave rise to the term "smog" (a combination of smoke and fog). Events of this type have become much less severe since the 1950s in Western Europe and the US, as natural gas replaced coal as the primary source of home heating, industrial smokestacks were designed to emit at higher altitudes (where dispersion is more rapid), and industries were required to install pollution control equipment.Beginning in the 1950s, a new type of pollution, photochemical smog, became a major concern. Photochemical smog consists of ozone (O3) and other closely related species ("secondary pollutants") that are produced photochemically from directly emitted species, in a process that is driven by sunlight and is accelerated by warm temperatures. This smog is largely the product of gasoline-powered engines (especially automobiles), although coal-fired industry can also generate photochemical smog. The process of photochemical smog formation was first identified by Haagen-Smit and Fox (1954) in association with Los Angeles, a city whose geography makes it particularly susceptible to this type of smog formation. Sulfate aerosols and organic particulates are often produced concurrently with ozone, giving rise to a characteristic milky-white haze associated with this type of air pollution.Today ozone and particulates are recognized as the air pollutants that are most likely to affect human health adversely. In the United States, most major metropolitan areas have periodic air pollution events with ozone in excess of government health standards. Violations of local health standards also occur in major cities in Canada and in much of Europe. Other cities around the world (especially Mexico City) also experience very high ozone levels. In addition to urban-scale events, elevated ozone occurs in region-wide events in the eastern USA and in Western Europe, with excess ozone extending over areas of 1,000 km2 or more. Ozone plumes of similar extent are found in the tropics (especially in Central Africa) at times of high biomass burning (e.g., Jenkins et al., 1997; Chatfield et al., 1998). In some cases ozone associated with biomass burning has been identified at distances up to 104 km from its sources (Schultz et al., 1999).Ozone also has a significant impact on the global troposphere, and ozone chemistry is a major component of global tropospheric chemistry. Global background ozone concentrations are much lower than urban or regional concentrations during pollution events, but there is evidence that the global background has increased as a result of human activities (e.g., Wang and Jacob, 1998; Volz and Kley, 1988). A rise in global background ozone can make the effects of local pollution events everywhere more acute, and can also cause ecological damage in remote locations that are otherwise unaffected by urban pollution. Ozone at the global scale is also related to greenhouse warming.This chapter provides an overview of photochemical smog at the urban and regional scale, focused primarily on ozone and including a summary of information about particulates. It includes the following topics: dynamics and extent of pollution events; health and ecological impacts; relation between ozone and precursor emissions, including hydrocarbons and nitrogen oxides (NOx); sources, composition, and fundamental properties of particulates; chemistry of ozone and related species; methods of interpretation based on ambient measurements; and the connection between air pollution events and the chemistry of the global troposphere. Because there are many similarities between the photochemistry of ozone during pollution events and the chemistry of the troposphere in general, this chapter will include some information about global tropospheric chemistry and the links between urban-scale and global-scale events. Additional treatment of the global troposphere is found in Volume 4 of this work. The chemistry of ozone formation discussed here is also related to topics discussed in greater detail elsewhere in this volume (see Chapters 9.10 and 9.12) and in Volume 4.

Urban greening impacts on tropospheric ozone

NASA Astrophysics Data System (ADS)

Grote, R.; Churkina, G.; Butler, T. M.; Morfopoulos, C.

2013-12-01

Cities are characterized by elevated air temperatures as well as high anthropogenic emissions of air pollutants. Cities' greening in form of urban parks, street trees, and vegetation on roofs and walls of buildings is supposed to generally mitigate negative impacts on human health and well-being. However, high emissions of biogenic volatile organic compounds (BVOC) from certain popular urban plants in combination with the elevated concentrations of NOx have the potential to increase ground-level ozone concentrations - with negative impacts on health, agriculture, and climate. Policies targeting reduction of ground-level ozone in urban and suburban areas therefore must consider limiting BVOC emissions along with measures for decreasing NOx and VOC from anthropogenic sources. For this, integrated climate/ chemistry models are needed that take into account the species-specific physiological responses of urban plants which in turn drive their emission behavior. Current models of urban climate and air quality 1) do not account for the feedback between ozone concentrations, productivity, and BVOC emission and 2) do not distinguish different physiological properties of urban tree species. Instead environmental factors such as light, temperature, carbon dioxide, and water supply are applied disregarding interactions between such influences. Thus we may not yet be able to represent the impacts of air pollution under multiple changed conditions such as climate change, altered anthropogenic emission patterns, and new urban structures. We present here the implementation of the new BVOC emission model (Morfopolous et al., in press) that derives BVOC emissions directly from the electron production potential and consumption from photosynthesis calculation that is already supplied by the CLM land surface model. The new approach has the advantage that many environmental drivers of BVOC emissions are implicitly considered in the description of plant photosynthesis and phenology. We investigate the tradeoff between vegetation driven ozone -reduction and -formation processes in dependence on temperature, radiation, CO2 and O3 concentrations. We have parameterized suitable plant functional types for different urban greening structures, currently focusing on central European vegetation. The modified CLM model is applied in a global (CESM) and a regional climate/ air quality model (WRF-Chem) to calculate realistic ozone concentrations in the influence zones of urban conglomerations. BVOC emissions and their impacts are also calculated with the standard MEGAN2.1 approach for comparison. The simulation results are analyzed and discussed in view of the models suitability for air quality scenario estimates under simultaneously changing climate, anthropogenic emissions and plant species composition. References Morfopoulos, C., Prentice, I.C., Keenan T.F., Friedlingstein, P., Medlyn, B., Penuelas, J., Possel, M. (in press): A unifying conceptual model for the environmental responses of isoprene emission by plants. Annals of Botany

Characterizing ozone pollution in a petrochemical industrial area in Beijing, China: a case study using a chemical reaction model.

PubMed

Wei, Wei; Lv, Zhaofeng; Cheng, Shuiyuan; Wang, Lili; Ji, Dongsheng; Zhou, Ying; Han, Lihui; Wang, Litao

2015-06-01

This study selected a petrochemical industrial complex in Beijing, China, to understand the characteristics of surface ozone (O3) in this industrial area through the on-site measurement campaign during the July-August of 2010 and 2011, and to reveal the response of local O3 to its precursors' emissions through the NCAR-Master Mechanism model (NCAR-MM) simulation. Measurement results showed that the O3 concentration in this industrial area was significantly higher, with the mean daily average of 124.6 μg/m(3) and mean daily maximum of 236.8 μg/m(3), which are, respectively, 90.9 and 50.6 % higher than those in Beijing urban area. Moreover, the diurnal O3 peak generally started up early in 11:00-12:00 and usually remained for 5-6 h, greatly different with the normal diurnal pattern of urban O3. Then, we used NCAR-MM to simulate the average diurnal variation of photochemical O3 in sunny days of August 2010 in both industrial and urban areas. A good agreement in O3 diurnal variation pattern and in O3 relative level was obtained for both areas. For example of O3 daily maximum, the calculated value in the industrial area was about 51 % higher than in the urban area, while measured value in the industrial area was approximately 60 % higher than in the urban area. Finally, the sensitivity analysis of photochemical O3 to its precursors was conducted based on a set of VOCs/NOx emissions cases. Simulation results implied that in the industrial area, the response of O3 to VOCs was negative and to NOx was positive under the current conditions, with the sensitivity coefficients of -0.16~-0.43 and +0.04~+0.06, respectively. By contrast, the urban area was within the VOCs-limitation regime, where ozone enhancement in response to increasing VOCs emissions and to decreasing NOx emission. So, we think that the VOCs emissions control for this petrochemical industrial complex will increase the potential risk of local ozone pollution aggravation, but will be helpful to inhibit the ozone formation in Beijing urban area through reducing the VOCs transport from the industrial area to the urban area.

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.

The potential near-source ozone impacts of upstream oil and gas industry emissions.

PubMed

Olaguer, Eduardo P

2012-08-01

Increased drilling in urban areas overlying shale formations and its potential impact on human health through decreased air quality make it important to estimate the contribution of oil and gas activities to photochemical smog. Flares and compressor engines used in natural gas operations, for example, are large sources not only of NOx but also offormaldehyde, a hazardous air pollutant and powerful ozone precursor We used a neighborhood scale (200 m horizontal resolution) three-dimensional (3D) air dispersion model with an appropriate chemical mechanism to simulate ozone formation in the vicinity ofa hypothetical natural gas processing facility, based on accepted estimates of both regular and nonroutine emissions. The model predicts that, under average midday conditions in June, regular emissions mostly associated with compressor engines may increase ambient ozone in the Barnett Shale by more than 3 ppb beginning at about 2 km downwind of the facility, assuming there are no other major sources of ozone precursors. Flare volumes of 100,000 cubic meters per hour ofnatural gas over a period of 2 hr can also add over 3 ppb to peak 1-hr ozone somewhatfurther (>8 km) downwind, once dilution overcomes ozone titration and inhibition by large flare emissions of NOx. The additional peak ozone from the hypothetical flare can briefly exceed 10 ppb about 16 km downwind. The enhancements of ambient ozone predicted by the model are significant, given that ozone control strategy widths are of the order of a few parts per billion. Degrading the horizontal resolution of the model to 1 km spuriously enhances the simulated ozone increases by reducing the effectiveness of ozone inhibition and titration due to artificial plume dilution.

Quantifying the ozone "weekend effect" at various locations in Phoenix, Arizona

NASA Astrophysics Data System (ADS)

Atkinson-Palombo, Carol M.; Miller, James A.; Balling, Robert C.

Analysis of pollution data from a network of monitors in Maricopa County, Arizona, reveals considerable variation in the magnitude of the ozone "weekend effect" depending on how and where it is measured. We used four separate methods to calculate the weekend effect, all of which showed that the phenomenon is stronger in the urban core, where ozone is produced. Spatial linear regressions show that the magnitude of the weekend effect and the goodness of fit of weekly harmonic cycles in ozone is a function of urbanization, described quantitatively using an index of traffic counts, population, and employment within a 4 km buffer zone of monitoring sites. Analysis of diurnal patterns of ozone as well as oxides of nitrogen (NO x) at a representative site in the urban core supports the hypothesis that lower levels of NO x on Sundays reduce the degree to which ozone is titrated, resulting in a higher minimum and hence mean for that day of the week (DOW). Fringe sites, where ozone concentrations are higher in absolute terms than in the urban core, show almost no "weekend effect," regardless of which of the four individual methods we used. Alternative quantification methods show statistically significant DOW differences in ozone levels in urban fringe locations, albeit out of phase with the weekly cycling of ozone in the urban core. Our findings suggest that multiple metrics need to be used to test for the weekend effect and that the causes of DOW differences in ozone concentrations may be location specific.

Analysis of impacts of urban land use and land cover on air quality in the Las Vegas region using remote sensing information and ground observations

USGS Publications Warehouse

Xian, G.

2007-01-01

Urban development in the Las Vegas Valley of Nevada (USA) has expanded rapidly over the past 50 years. The air quality in the valley has suffered owing to increases from anthropogenic emissions of carbon monoxide, ozone and criteria pollutants of particular matter. Air quality observations show that pollutant concentrations have apparent heterogeneous characteristics in the urban area. Quantified urban land use and land cover information derived from satellite remote sensing data indicate an apparent local influence of urban development density on air pollutant distributions. Multi‐year observational data collected by a network of local air monitoring stations specify that ozone maximums develop in the May and June timeframe, whereas minimum concentrations generally occur from November to February. The fine particulate matter maximum occurs in July. Ozone concentrations are highest on the west and northwest sides of the valley. Night‐time ozone reduction contributes to the heterogeneous features of the spatial distribution for average ozone levels in the Las Vegas metropolitan area. Decreased ozone levels associated with increased urban development density suggest that the highest ozone and lowest nitrogen oxides concentrations are associated with medium to low density urban development in Las Vegas.

NOx emissions and photochemistry associated with oil and gas production

NASA Astrophysics Data System (ADS)

Edwards, P.; Brown, S. S.; Dube, W. P.; Holloway, J. S.; Petron, G.; Kofler, J.; Warneke, C.; Williams, E. J.; Young, C. J.; Geiger, F.

2012-12-01

Winter ozone concentrations exceeding the current national ambient air quality standards (NAAQS) were observed in the Uintah basin, Utah, during the winters of 2009-2010 and 2010-2011. The chemistry driving these ground level ozone episodes, usually considered an urban summertime phenomenon, is currently poorly understood. Emissions of ozone precursor species in the Uintah basin are complex, and thought to be driven largely by extensive oil and gas development and production within the basin. The Uintah Basin Winter Ozone Study (UBWOS) was a major collaborative field study in February-March 2012, with the aim of increasing our understanding of this important air quality issue. Through the use of a comprehensive suite of instrumentation and multiple measurement platforms we have been able to better characterize the sources of important ozone precursors, in particular NOx and VOCs, within the basin. These observations enable an investigation of the unique aspects of local sources and chemistry that lead to winter ozone formation within the Uintah basin.

Modeling the uncertainty of several VOC and its impact on simulated VOC and ozone in Houston, Texas

NASA Astrophysics Data System (ADS)

Pan, Shuai; Choi, Yunsoo; Roy, Anirban; Li, Xiangshang; Jeon, Wonbae; Souri, Amir Hossein

2015-11-01

A WRF-SMOKE-CMAQ modeling system was used to study Volatile Organic Compound (VOC) emissions and their impact on surface VOC and ozone concentrations in southeast Texas during September 2013. The model was evaluated against the ground-level Automated Gas Chromatograph (Auto-GC) measurement data from the Texas Commission on Environmental Quality (TCEQ). The comparisons indicated that the model over-predicted benzene, ethylene, toluene and xylene, while under-predicting isoprene and ethane. The mean biases between simulated and observed values of each VOC species showed clear daytime, nighttime, weekday and weekend variations. Adjusting the VOC emissions using simulated/observed ratios improved model performance of each VOC species, especially mitigating the mean bias substantially. Simulated monthly mean ozone showed a minor change: a 0.4 ppb or 1.2% increase; while a change of more than 5 ppb was seen in hourly ozone data on high ozone days, this change moved model predictions closer to observations. The CMAQ model run with the adjusted emissions better reproduced the variability in the National Aeronautics and Space Administration (NASA)'s Ozone Monitoring Instrument (OMI) formaldehyde (HCHO) columns. The adjusted model scenario also slightly better reproduced the aircraft HCHO concentrations from NASA's DISCOVER-AQ campaign conducted during the simulation episode period; Correlation, Mean Bias and RMSE improved from 0.34, 1.38 ppb and 2.15 ppb to 0.38, 1.33 ppb and 2.08 ppb respectively. A process analysis conducted for both industrial/urban and rural areas suggested that chemistry was the main process contributing to ozone production in both areas, while the impact of chemistry was smaller in rural areas than in industrial and urban areas. For both areas, the positive chemistry contribution increased in the sensitivity simulation largely due to the increase in emissions. Nudging VOC emissions to match the observed concentrations shifted the ozone hotspots outside the industrial/urban region and enhanced the peaked ozone in the outflow region with consistent southerly/southeasterly winds during the afternoon time (1-5 pm). This study helps in the understanding of these processes which are critical to constrain high peak ozone values in the outflow regions. The results indicate that formation of ozone in the outflow could complicate attainment status in neighboring counties.

Effects of 10% biofuel substitution on ground level ozone formation in Bangkok, Thailand

NASA Astrophysics Data System (ADS)

Milt, Austin; Milano, Aaron; Garivait, Savitri; Kamens, Richard

2009-12-01

The Thai Government's search for alternatives to imported petroleum led to the consideration of mandating 10% biofuel blends (biodiesel and gasohol) by 2012. Concerns over the effects of biofuel combustion on ground level ozone formation in relation to their conventional counterparts need addressing. Ozone formation in Bangkok is explored using a trajectory box model. The model is compared against O 3, NO, and NO 2 time concentration data from air monitoring stations operated by the Thai Pollution Control Department. Four high ozone days in 2006 were selected for modeling. Both the traditional trajectory approach and a citywide average approach were used. The model performs well with both approaches but slightly better with the citywide average. Highly uncertain and missing data are derived within realistic bounds using a genetic algorithm optimization. It was found that 10% biofuel substitution will lead to as much as a 16 ppb peak O 3 increase on these four days compared to a 48 ppb increase due to the predicted vehicle fleet size increase between 2006 and 2012. The approach also suggests that when detailed meteorological data is not available to run three dimensional airshed models, and if the air is stagnant or predominately remains over an urban area during the day, that a simple low cost trajectory analysis of O 3 formation may be applicable.

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.

Stochastic model to forecast ground-level ozone concentration at urban and rural areas.

PubMed

Dueñas, C; Fernández, M C; Cañete, S; Carretero, J; Liger, E

2005-12-01

Stochastic models that estimate the ground-level ozone concentrations in air at an urban and rural sampling points in South-eastern Spain have been developed. Studies of temporal series of data, spectral analyses of temporal series and ARIMA models have been used. The ARIMA model (1,0,0) x (1,0,1)24 satisfactorily predicts hourly ozone concentrations in the urban area. The ARIMA (2,1,1) x (0,1,1)24 has been developed for the rural area. In both sampling points, predictions of hourly ozone concentrations agree reasonably well with measured values. However, the prediction of hourly ozone concentrations in the rural point appears to be better than that of the urban point. The performance of ARIMA models suggests that this kind of modelling can be suitable for ozone concentrations forecasting.

Nitrogen oxides and ozone in Portugal: trends and ozone estimation in an urban and a rural site.

PubMed

Fernández-Guisuraga, José Manuel; Castro, Amaya; Alves, Célia; Calvo, Ana; Alonso-Blanco, Elisabeth; Blanco-Alegre, Carlos; Rocha, Alfredo; Fraile, Roberto

2016-09-01

This study provides an analysis of the spatial distribution and trends of NO, NO2 and O3 concentrations in Portugal between 1995 and 2010. Furthermore, an estimation model for daily ozone concentrations was developed for an urban and a rural site. NO concentration showed a significant decreasing trend in most urban stations. A decreasing trend in NO2 is only observed in the stations with less influence from emissions of primary NO2. Several stations showed a significant upward trend in O3 as a result of the decrease in the NO/NO2 ratio. In the northern rural region, ozone showed a strong correlation with wind direction, highlighting the importance of long-range transport. In the urban site, most of the variance is explained by the NO2/NOX ratio. The results obtained by the ozone estimation model in the urban site fit 2013 observed data. In the rural site, the estimated ozone during extreme events agrees with observed concentration.

Development of a sensitive passive sampler using indigotrisulfonate for the determination of tropospheric ozone.

PubMed

Garcia, Gabriel; Allen, Andrew George; Cardoso, Arnaldo Alves

2010-06-01

A new sampling and analytical design for measurement of ambient ozone is presented. The procedure is based on ozone absorption and decoloration (at 600 nm) of indigotrisulfonate dye, where ozone adds itself across the carbon-carbon double bond of the indigo. A mean relative standard deviation of 8.6% was obtained using samplers exposed in triplicate, and a correlation coefficient (r) of 0.957 was achieved in parallel measurements using the samplers and a commercial UV ozone instrument. The devices were evaluated in a measurement campaign, mapping spatial and temporal trends of ozone concentrations in a region of southeast Brazil strongly influenced by seasonal agricultural biomass burning, with associated emissions of ozone precursors. Ozone concentrations were highest in rural areas and lowest at an urban site, due to formation during downwind transport and short-term depletion due to titration with nitric oxide. Ozone concentrations showed strong seasonal trends, due to the influences of precursor emissions, relative humidity and solar radiation intensity. Advantages of the technique include ease and speed of use, the ready availability of components, and excellent sensitivity. Achievable temporal resolution of ozone concentrations is 8 hours at an ambient ozone concentration of 3.8 ppb, or 2 hours at a concentration of 15.2 ppb.

Ozone production in remote oceanic and industrial areas derived from ship based measurements of peroxy radicals during TexAQS 2006

NASA Astrophysics Data System (ADS)

Sommariva, R.; Brown, S. S.; Roberts, J. M.; Brookes, D. M.; Parker, A. E.; Monks, P. S.; Bates, T. S.; Bon, D.; de Gouw, J. A.; Frost, G. J.; Gilman, J. B.; Goldan, P. D.; Herndon, S. C.; Kuster, W. C.; Lerner, B. M.; Osthoff, H. D.; Tucker, S. C.; Warneke, C.; Williams, E. J.; Zahniser, M. S.

2011-03-01

During the Texas Air Quality Study II (TexAQS 2006) campaign, a PEroxy Radical Chemical Amplifier (PERCA) was deployed on the NOAA research vessel R/V Brown to measure total peroxy radicals (HO2+Σ RO2). Day-time mixing ratios of HO2+Σ RO2 between 25 and 110 ppt were observed throughout the study area - the Houston/Galveston region and the Gulf coast of the US - and analyzed in relation to measurements of nitrogen oxides, volatile organic compounds (VOC) and photolysis rates to assess radical sources and sinks in the region. The measurements of HO2+Σ RO2 were used to calculate the in-situ net photochemical formation of ozone. Measured median values ranged from 0.6 ppb/h in clean oceanic air masses up to several tens of ppb/h in the most polluted industrial areas. The results are consistent with previous studies and generally agree with observations made during the previous TexAQS 2000 field campaign. The net photochemical ozone formation rates determined at Barbours Cut, a site immediately south of the Houston Ship Channel, were analyzed in relation to local wind direction and VOC reactivity to understand the relationship between ozone formation and local VOC emissions. The measurements of HO2+Σ RO2 made during the R/V Brown TexAQS 2006 cruise indicate that ozone formation is NOx-limited in the Houston/Galveston region and influenced by highly reactive hydrocarbons, especially alkenes from urban and industrial sources and their photo-oxidation products, such as formaldehyde.

Ozone production in remote oceanic and industrial areas derived from ship based measurements of peroxy radicals during TexAQS 2006

NASA Astrophysics Data System (ADS)

Sommariva, R.; Brown, S. S.; Roberts, J. M.; Brookes, D. M.; Parker, A. E.; Monks, P. S.; Bates, T. S.; Bon, D.; de Gouw, J. A.; Frost, G. J.; Gilman, J. B.; Goldan, P. D.; Herndon, S. C.; Kuster, W. C.; Lerner, B. M.; Osthoff, H. D.; Tucker, S. C.; Warneke, C.; Williams, E. J.; Zahniser, M. S.

2010-10-01

During the Texas Air Quality Study II (TexAQS 2006) campaign, a PEroxy Radical Chemical Amplifier (PERCA) was deployed on the NOAA research vessel R/V Brown to measure total peroxy radicals (HO2+ΣRO2). Day-time mixing ratios of HO2+ΣRO2 between 25 and 110 ppt were observed throughout the study area - the Houston/Galveston region and the Gulf coast of the U.S. - and analyzed in relation to measurements of nitrogen oxides, volatile organic compounds (VOC) and photolysis rates to assess radical sources and sinks in the region. The measurements of HO2+ΣRO2 were used to calculate the in-situ net photochemical formation of ozone. Measured median values ranged from 0.6 ppb/h in clean oceanic air masses up to several tens of ppb/h in the most polluted industrial areas. The results are consistent with previous studies and generally agree with observations made during the previous TexAQS 2000 field campaign. The net photochemical ozone formation rates determined at Barbours Cut, a site immediately south of the Houston Ship Channel, were analyzed in relation to local wind direction and VOC reactivity to understand the relationship between ozone formation and local VOC emissions. The measurements of HO2+ΣRO2 made during the R/V Brown TexAQS 2006 cruise indicate that ozone formation is NOx-limited in the Houston/Galveston region and influenced by highly reactive hydrocarbons, especially alkenes from urban and industrial sources and their photooxidation products, such as formaldehyde.

On the Complex Coupling Between the Production of Ozone and Secondary Organic Aerosol in Polluted Urban Regions

NASA Astrophysics Data System (ADS)

Stewart, D. R.; Stockwell, W. R.; Morris, V. R.; Fitzgerald, R. M.

2016-12-01

The major photochemical processes that produce ozone and aerosols are coupled together strongly in the polluted urban atmosphere. Aerosols are either directly emitted or formed through the same kind of chemistry that leads to the production of ozone. The aerosols produced through atmospheric chemistry are known as secondary aerosols and they may be composed of inorganic (nitrates, sulfates) or organic compounds. Wind blown dust and soot are two examples of primary aerosols. The component of secondary inorganic aerosols includes compounds such as ammonium nitrate, ammonium bisulfate and ammonium sulfate. Secondary organic aerosols are a very important component of PM with strong implications for health. The formation of secondary organic aerosol is linked with ozone photochemistry through the reactions of volatile organic compounds (VOC). The oxidation of VOC produces radicals that convert nitric oxide to nitrogen dioxide that photolyze to produce ozone. Larger VOC (those with more carbon atoms) undergo a number of oxidation cycles that add oxygen atoms to large organic molecules. The vapor pressure of many of these highly oxidized compounds is sufficiently low that they condense to produce secondary organic aerosols. The Community Multi-scale Air Quality model (CMAQ) and other chemical simulations have been made to quantify the relationship between varying emissions of VOC and NOx and the production of inorganic and secondary organic aerosols. The results from this analysis will be presented.

Measurement of volatile organic compounds in suburban Bangkok, Thailand: characteristics and influence from combustion related activities

NASA Astrophysics Data System (ADS)

Suthawaree, J.; Tajima, Y.; Kato, S.; Khunchornyakong, A.; Sharp, A.; Kajii, Y.

2009-12-01

Elucidation of air quality in the suburban area of Bangkok, Thailand is essential in order to achieve effective regulations and mitigation strategies. VOCs plays important role in formation of tropospheric urban ozone. Without overkill NO concentration, transport of O3 precursors into suburban area which add surplus to local O3 formation as well as direct transport of O3 itself results in relatively higher total O3 observed in suburban area rather than urban. Whole air canister sampling was carried out in the suburban Bangkok during 2008, July 2-7. 4 samples per day were collected at 30 min passes 6, 12, 17, 21 hours with sampling time of 1 min. Analysis was achieved by using GC-FID and GC-MS. High concentrations of VOCs detected during the peak periods in the morning and evening are most likely due to vehicular emission. Averaged VOCs concentrations, reveal distinct different between data measured for weekday and weekend which the latter were found with lower concentrations. No difference was found for CFCs which the levels are also comparable to global background level reported by World Meteorological Organization. The most abundance species have found to be propane and toluene with averaged concentration of 3100 and 2891 pptv, respectively. Ratios of benzene over toluene suggest additional concentration owing to industrial emission, of which particularly larger during the weekday. Comparison with C2Cl4 and CH3Cl concentrations obtained for suburban Tokyo reveal relatively higher influence of biomass burning at suburban Bangkok. In order to estimate the role of the different VOCs towards tropospheric ozone formation, ozone formation potential was calculated using maximum incremental reactivity. Toluene was found to contribute the most to O3 production followed by ethylene, m,p-xylene, and propylene.

Progress in understanding the formation of fine particulate matter and ground-level ozone in Pearl River Delta region, China

NASA Astrophysics Data System (ADS)

Wang, Xuemei; Wang, Tao; Zheng, Junyu; Shao, Min; Wang, Xinming

2015-12-01

In the past three decades, the Pearl River Delta of China has been suffered from severe air pollution due to the rapid increase in energy consumption associated with industrialization and urbanization of the region. The number of hazy days, increased from below 20 days in a year before 1970, to more than 150 days a year during 1980 and 2000. The ground-level ozone levels have also on the rise, with hourly concentration of 160 ppbv being observed in Guangzhou and 201 ppbv in nearby Hong Kong (Zhang et al., 2008). The ozone pollution has been difficult to reduce even in air quality improvement program for the Guangzhou Asian Games (Liu et al., 2013).

Analyses of ozone in urban and rural sites in Málaga (Spain).

PubMed

Dueñas, C; Fernández, M C; Cañete, S; Carretero, J; Liger, E

2004-08-01

Ozone concentrations were measured at two (urban and a rural) sites near the city of Málaga (Spain). The aim of this study was to determine the daily, monthly and seasonal variation patterns of ozone concentrations at both sites and to study the possible regional influences. The daily variations mostly have the usual features with the afternoon maximum and the night minimum being more pronounced in the urban area. The average monthly concentrations throughout the year start to increase in March reaching their maximum values in July for the urban site. However, in the rural area, the monthly variations are smaller reaching their maximum value in June. The hourly evolution of the ozone concentrations in both sampling sites is well defined in spring and summer and not so well defined in autumn and winter. Taking into account the four seasons, the rural concentrations are higher than the urban ones. Summer is the season when there are similar concentrations at both sampling sites. Average hourly summer afternoon ozone for the hours 12:00-20:00 LST exceeded the 110 microg m(-3) European Union guidelines for human health for 8 h ozone exposure at the urban and rural sites.

Kinetic and mechanistic reactivity. Isoprene impact on ozone levels in an urban area near Tijuca Forest, Rio de Janeiro.

PubMed

da Silva, Cleyton Martins; da Silva, Luane Lima; Corrêa, Sergio Machado; Arbilla, Graciela

2016-12-01

Volatile organic compounds (VOCs) play a central role in atmospheric chemistry. In this work, the kinetic and mechanistic reactivities of VOCs are analyzed, and the contribution of the organic compounds emitted by anthropogenic and natural sources is estimated. VOCs react with hydroxyl radicals and other photochemical oxidants, such as ozone and nitrate radicals, which cause the conversion of NO to NO 2 in various potential reaction paths, including photolysis, to form oxygen atoms, which generate ozone. The kinetic reactivity was evaluated based on the reaction coefficients for hydroxyl radicals with VOCs. The mechanistic reactivity was estimated using a detailed mechanism and the incremental reactivity scale that Carter proposed. Different scenarios were proposed and discussed, and a minimum set of compounds, which may describe the tropospheric reactivity in the studied area, was determined. The role of isoprene was analyzed in terms of its contribution to ozone formation.

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.

Modelling the photochemical pollution over the metropolitan area of Porto Alegre, Brazil

NASA Astrophysics Data System (ADS)

Borrego, C.; Monteiro, A.; Ferreira, J.; Moraes, M. R.; Carvalho, A.; Ribeiro, I.; Miranda, A. I.; Moreira, D. M.

2010-01-01

The main purpose of this study is to evaluate the photochemical pollution over the Metropolitan Area of Porto Alegre (MAPA), Brazil, where high concentrations of ozone have been registered during the past years. Due to the restricted spatial coverage of the monitoring air quality network, a numerical modelling technique was selected and applied to this assessment exercise. Two different chemistry-transport models - CAMx and CALGRID - were applied for a summer period, driven by the MM5 meteorological model. The meteorological model performance was evaluated comparing its results to available monitoring data measured at the Porto Alegre airport. Validation results point out a good model performance. It was not possible to evaluate the chemistry models performance due to the lack of adequate monitoring data. Nevertheless, the model intercomparison between CAMx and CALGRID shows a similar behaviour in what concerns the simulation of nitrogen dioxide, but some discrepancies concerning ozone. Regarding the fulfilment of the Brazilian air quality targets, the simulated ozone concentrations surpass the legislated value in specific periods, mainly outside the urban area of Porto Alegre. The ozone formation is influenced by the emission of pollutants that act as precursors (like the nitrogen oxides emitted at Porto Alegre urban area and coming from a large refinery complex) and by the meteorological conditions.

Measurements of in situ chemical ozone (oxidant) production rates

NASA Astrophysics Data System (ADS)

Huang, Hao; Faloon, Kate; Najera, Juan; Bloss, William

2013-04-01

Tropospheric ozone is a major air pollutant, harmful to human health, agricultural crops and vegetation, the main precursor to the atmospheric oxidants which initiate the degradation of most reactive gases emitted to the atmosphere, and an important greenhouse gas in its own right. The capacity to understand and predict tropospheric ozone levels is a key goal for atmospheric science - but one which is challenging, as ozone is formed in the atmosphere from the complex oxidation of VOCs in the presence of NOx and sunlight, on a timescale such that in situ chemical processes, deposition and transport all affect ozone levels. Known uncertainties in emissions, chemistry, dynamics and deposition affect the accuracy of predictions of current and future ozone levels, and hinder development of optimal air quality policies to mitigate against ozone exposure. Recently new approaches to directly measure the local chemical ozone production rate, bypassing the many uncertainties in emissions and chemical schemes, have been developed (Cazorla & Brune, AMT 2010). Here, we describe the development of an analogous Ozone Production Rate (OPR) approach: Air is sampled into parallel reactors, within which ozone formation either occurs as in the ambient atmosphere, or is suppressed. Comparisons of ozone levels exiting a pair of such reactors determines the net chemical oxidant production rate, after correction for perturbation of the NOx-O3 photochemical steady state, and when operated under conditions such that wall effects are minimised. We report preliminary measurements of local chemical ozone production made during the UK NERC ClearfLo (Clean Air for London) campaign at an urban background location in London in January and July 2012. The OPR system was used to measure the local chemical oxidant formation rate, which is compared with observed trends in O3 and NOx and the prevailing meteorology, and with the predictions of a detailed zero-dimensional atmospheric chemistry model, constrained by observations of long-lived species.

Concentration–Response Function for Ozone and Daily Mortality: Results from Five Urban and Five Rural U.K. Populations

PubMed Central

Yu, Dahai; Armstrong, Ben G.; Pattenden, Sam; Wilkinson, Paul; Doherty, Ruth M.; Heal, Mathew R.; Anderson, H. Ross

2012-01-01

Background: Short-term exposure to ozone has been associated with increased daily mortality. The shape of the concentration–response relationship—and, in particular, if there is a threshold—is critical for estimating public health impacts. Objective: We investigated the concentration–response relationship between daily ozone and mortality in five urban and five rural areas in the United Kingdom from 1993 to 2006. Methods: We used Poisson regression, controlling for seasonality, temperature, and influenza, to investigate associations between daily maximum 8-hr ozone and daily all-cause mortality, assuming linear, linear-threshold, and spline models for all-year and season-specific periods. We examined sensitivity to adjustment for particles (urban areas only) and alternative temperature metrics. Results: In all-year analyses, we found clear evidence for a threshold in the concentration–response relationship between ozone and all-cause mortality in London at 65 µg/m3 [95% confidence interval (CI): 58, 83] but little evidence of a threshold in other urban or rural areas. Combined linear effect estimates for all-cause mortality were comparable for urban and rural areas: 0.48% (95% CI: 0.35, 0.60) and 0.58% (95% CI: 0.36, 0.81) per 10-µg/m3 increase in ozone concentrations, respectively. Seasonal analyses suggested thresholds in both urban and rural areas for effects of ozone during summer months. Conclusions: Our results suggest that health impacts should be estimated across the whole ambient range of ozone using both threshold and nonthreshold models, and models stratified by season. Evidence of a threshold effect in London but not in other study areas requires further investigation. The public health impacts of exposure to ozone in rural areas should not be overlooked. PMID:22814173

Reassessing the atmospheric oxidation mechanism of toluene

NASA Astrophysics Data System (ADS)

Ji, Yuemeng; Zhao, Jun; Terazono, Hajime; Misawa, Kentaro; Levitt, Nicholas P.; Li, Yixin; Lin, Yun; Peng, Jianfei; Wang, Yuan; Duan, Lian; Pan, Bowen; Zhang, Fang; Feng, Xidan; An, Taicheng; Marrero-Ortiz, Wilmarie; Secrest, Jeremiah; Zhang, Annie L.; Shibuya, Kazuhiko; Molina, Mario J.; Zhang, Renyi

2017-08-01

Photochemical oxidation of aromatic hydrocarbons leads to tropospheric ozone and secondary organic aerosol (SOA) formation, with profound implications for air quality, human health, and climate. Toluene is the most abundant aromatic compound under urban environments, but its detailed chemical oxidation mechanism remains uncertain. From combined laboratory experiments and quantum chemical calculations, we show a toluene oxidation mechanism that is different from the one adopted in current atmospheric models. Our experimental work indicates a larger-than-expected branching ratio for cresols, but a negligible formation of ring-opening products (e.g., methylglyoxal). Quantum chemical calculations also demonstrate that cresols are much more stable than their corresponding peroxy radicals, and, for the most favorable OH (ortho) addition, the pathway of H extraction by O2 to form the cresol proceeds with a smaller barrier than O2 addition to form the peroxy radical. Our results reveal that phenolic (rather than peroxy radical) formation represents the dominant pathway for toluene oxidation, highlighting the necessity to reassess its role in ozone and SOA formation in the atmosphere.

Quantifying Neighborhood-Scale Spatial Variations of Ozone at Open Space and Urban Sites in Boulder, Colorado Using Low-Cost Sensor Technology.

PubMed

Cheadle, Lucy; Deanes, Lauren; Sadighi, Kira; Gordon Casey, Joanna; Collier-Oxandale, Ashley; Hannigan, Michael

2017-09-10

Recent advances in air pollution sensors have led to a new wave of low-cost measurement systems that can be deployed in dense networks to capture small-scale spatio-temporal variations in ozone, a pollutant known to cause negative human health impacts. This study deployed a network of seven low-cost ozone metal oxide sensor systems (UPods) in both an open space and an urban location in Boulder, Colorado during June and July of 2015, to quantify ozone variations on spatial scales ranging from 12 m between UPods to 6.7 km between open space and urban measurement sites with a measurement uncertainty of ~5 ppb. The results showed spatial variability of ozone at both deployment sites, with the largest differences between UPod measurements occurring during the afternoons. The peak median hourly difference between UPods was 6 ppb at 1:00 p.m. at the open space site, and 11 ppb at 4:00 p.m. at the urban site. Overall, the urban ozone measurements were higher than in the open space measurements. This study evaluates the effectiveness of using low-cost sensors to capture microscale spatial and temporal variation of ozone; additionally, it highlights the importance of field calibrations and measurement uncertainty quantification when deploying low-cost sensors.

Development of a framework for quantifying the environmental impacts of urban development and construction practices.

PubMed

Li, Ke; Zhang, Peng; Crittenden, John C; Guhathakurta, Subhrajit; Chen, Yongsheng; Fernando, Harindra; Sawhney, Anil; McCartney, Peter; Grimm, Nancy; Kahhat, Ramzy; Joshi, Himanshu; Konjevod, Goran; Choi, Yu-Jin; Fonseca, Ernesto; Allenby, Braden; Gerrity, Daniel; Torrens, Paul M

2007-07-15

To encourage sustainable development, engineers and scientists need to understand the interactions among social decision-making, development and redevelopment, land, energy and material use, and their environmental impacts. In this study, a framework that connects these interactions was proposed to guide more sustainable urban planning and construction practices. Focusing on the rapidly urbanizing setting of Phoenix, Arizona, complexity models and deterministic models were assembled as a metamodel, which is called Sustainable Futures 2100 and were used to predict land use and development, to quantify construction material demands, to analyze the life cycle environmental impacts, and to simulate future ground-level ozone formation.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

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.

Air quality during the 2008 Beijing Olympics: secondary pollutants and regional impact

NASA Astrophysics Data System (ADS)

Wang, T.; Nie, W.; Gao, J.; Xue, L. K.; Gao, X. M.; Wang, X. F.; Qiu, J.; Poon, C. N.; Meinardi, S.; Blake, D.; Wang, S. L.; Ding, A. J.; Chai, F. H.; Zhang, Q. Z.; Wang, W. X.

2010-08-01

This paper presents the first results of the measurements of trace gases and aerosols at three surface sites in and outside Beijing before and during the 2008 Olympics. The official air pollution index near the Olympic Stadium and the data from our nearby site revealed an obvious association between air quality and meteorology and different responses of secondary and primary pollutants to the control measures. Ambient concentrations of vehicle-related nitrogen oxides (NOx) and volatile organic compounds (VOCs) at an urban site dropped by 25% and 20-45% in the first two weeks after full control was put in place, but the levels of ozone, sulfate and nitrate in PM2.5 increased by 16%, 64%, 37%, respectively, compared to the period prior to the full control; wind data and back trajectories indicated the contribution of regional pollution from the North China Plain. Air quality (for both primary and secondary pollutants) improved significantly during the Games, which were also associated with the changes in weather conditions (prolonged rainfall, decreased temperature, and more frequent air masses from clean regions). A comparison of the ozone data at three sites on eight ozone-pollution days, when the air masses were from the southeast-south-southwest sector, showed that regional pollution sources contributed >34-88% to the peak ozone concentrations at the urban site in Beijing. Regional sources also contributed significantly to the CO concentrations in urban Beijing. Ozone production efficiencies at two sites were low (~3 ppbv/ppbv), indicating that ozone formation was being controlled by VOCs. Compared with data collected in 2005 at a downwind site, the concentrations of ozone, sulfur dioxide (SO2), total sulfur (SO2+PM2.5 sulfate), carbon monoxide (CO), reactive aromatics (toluene and xylenes) sharply decreased (by 8-64%) in 2008, but no significant changes were observed for the concentrations of PM2.5, fine sulfate, total odd reactive nitrogen (NOy), and longer lived alkanes and benzene. We suggest that these results indicate the success of the government's efforts in reducing emissions of SO2, CO, and VOCs in Beijing, but increased regional emissions during 2005-2008. More stringent control of regional emissions will be needed for significant reductions of ozone and fine particulate pollution in Beijing.

Ozone Trends Across the United States over a Period of Decreasing NOx and VOC Emissions

EPA Science Inventory

In this work, we evaluate ambient ozone trends at urban, suburban, and rural monitoring sites across the United States over a period of decreasing NOx and VOC emissions (1998–2013). We find that decreasing ozone trends generally occur in the summer, in less urbanized areas,...

Emission sources of non-methane volatile organic compounds (NMVOCs) and their contribution to photochemical ozone (O3) formation at an urban atmosphere in western India.

NASA Astrophysics Data System (ADS)

Yadav, R.; Sahu, L. K.; Tripathi, N.; Pal, D.

2017-12-01

Atmospheric non-methane volatile organic compounds (NMVOCs) were measured at a sampling site in Udaipur city of western India during 2015 to recognize their pollution levels, variation characteristics, sources and photochemical reactivity. The samples were analyzed for NMVOCs using a Gas Chromatograph equipped with Flame Ionization Detector (GC/FID) and Thermal Desorption (TD) system. The main focus on understand the sources responsible for NMVOC emissions, and evaluating the role of the identified sources towards ozone formation. Hourly variations of various NMVOC species indicate that VOCs mixing ratios were influenced by photochemical removal with OH radicals for reactive species, secondary formation for oxygenated VOCs. In general, higher mixing ratios were observed during winter/pre-monsoon and lower levels during the monsoon season due to the seasonal change in meteorological, transport path of air parcel and boundary layer conditions. The high levels of propane (C3H8) and butane (C4H10) show the dominance of LPG over the study location. The correlation coefficients of typical NMVOC pairs (ethylene/propylene, propylene/isoprene, and ethane/propane) depicted that vehicular emission and natural gas leakages were important sources for atmospheric hydrocarbons in Udaipur. Based on the annual data, PMF analysis suggest the source factors namely biomass burning/ bio-fuel, automobile exhaust, Industrial/ natural gas/power plant emissions, petrol/Diesel, gasoline evaporation, and use of liquid petroleum gas (LPG) contribute to NMVOCs loading. The propylene-equivalent and ozone formation potential of NMVOCs have also been calculated in order to find out their OH reactivity and contribution to the photochemical ozone formation.

Report card on low level ozone in urban areas

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

Onischak, M.

1994-12-31

It has been four years since the Clean Air Act was amended in November of 1990. Much work has been done in this time, and the country is beginning to see real air quality benefits. Although these changes have not completely licked the urban ozone problem yet, they have made a lot of progress. All of the urban areas which have been required to reduce their ozone levels have done a good job of lowering their emissions. While the urban areas have not all been able to meet every federal deadline, the areas have all been able to achieve themore » control milestones before the mandatory Clean Air Act sanctions have taken effect. Some areas are even ready to declare their ozone problems solved.« less

Development and field deployment of an instrument to measure ozone production rates in the troposphere

NASA Astrophysics Data System (ADS)

Sklaveniti, S.; Locoge, N.; Dusanter, S.; Leonardis, T.; Lew, M.; Bottorff, B.; Sigler, P. S. R.; Stevens, P. S.; Wood, E. C. D.; Kundu, S.; Gentner, D. R.

2015-12-01

Ozone is a greenhouse gas and a primary constituent of urban smog, irritating the respiratory system and damaging the vegetation. The current understanding of ozone chemistry in the troposphere indicates that net ozone production P(O3) occurs when peroxy radicals (HO2+RO2) react with NO producing NO2, whose photolysis leads to O3 formation. P(O3) values can be calculated from peroxy radical concentrations, either from ambient measurements or box model outputs. These two estimation methods often disagree for NOx mixing ratios higher than a few ppb, questioning our ability to measure peroxy radicals under high NOx conditions or indicating that there are still unknowns in our understanding of the radical and ozone production chemistry. Direct measurements of ozone production rates will help to address this issue and improve air quality regulations. We will present the development of an instrument for direct measurements of ozone production rates (OPR). The OPR instrument consists of three parts: (i) two quartz flow tubes sampling ambient air ("Ambient" and "Reference" flow tube), (ii) an O3-to-NO2 conversion unit, and (iii) a Cavity Attenuated Phase Shift (CAPS) monitor to measure NO2. The air in the Ambient flow tube undergoes the same photochemistry as in ambient air, while the Reference flow tube is covered by a UV filter limiting the formation of ozone. Exiting the flow tubes, ozone is converted into NO2 and the sum O3+NO2 (Ox) is measured by the CAPS monitor. The difference in Ox between the two flow tubes divided by the residence time yields the Ox production rate, P(Ox). P(O3) is assumed to be equal to P(Ox) when NO2 is efficiently photolyzed during daytime. We will present preliminary results from the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) campaign in Bloomington, Indiana, during July 2015, where ozone production rates were measured by introducing various amounts of NO inside the flow tubes to investigate the ozone production sensitivity.

Numerical study on the impacts of heterogeneous reactions on ozone formation in the Beijing urban area

NASA Astrophysics Data System (ADS)

Xu, Jun; Zhang, Yuanhang; Wang, Wei

2006-12-01

The air quality model CMAQ-MADRID (Community Multiscale Air Quality-Model of Aerosol Dynamics, Reaction, Ionization and Dissolution) was employed to simulate summer O3 formation in Beijing China, in order to explore the impacts of four heterogeneous reactions on O3 formation in an urban area. The results showed that the impacts were obvious and exhibited the characteristics of a typical response of a VOC-limited regime in the urban area. For the four heterogeneous reactions considered, the NO2 and HO2 heterogeneous reactions have the most severe impacts on O3 formation. During the O3 formation period, the NO2 heterogeneous reaction increased new radical creation by 30%, raising the atmospheric activity as more NO→NO2 conversion occurred, thus causing the O3 to rise. The increase of O3 peak concentration reached a maximum value of 67 ppb in the urban area. In the morning hours, high NO titration reduced the effect of the photolysis of HONO, which was produced heterogeneously at night in the surface layer. The NO2 heterogeneous reaction in the daytime is likely one of the major reasons causing the O3 increase in the Beijing urban area. The HO2 heterogeneous reaction accelerated radical termination, resulting in a decrease of the radical concentration by 44% at the most. O3 peak concentration decreased by a maximum amount of 24 ppb in the urban area. The simulation results were improved when the heterogeneous reactions were included, with the O3 and HONO model results close to the observations.

EVALUATION OF SHORT-TERM OGAWA PASSIVE, PHOTOLYTIC, AND FEDERAL REFERENCE METHOD SAMPLING DEVICES FOR NITROGEN OXIDES IN EL PASO AND HOUSTON, TEXAS

EPA Science Inventory

Nitrogen Dioxide (NO₂) is a common urban air pollutant that results from the combustion of fossil fuels. It causes serious human health effects, is a precursor to the formation of ground level ozone, another serious air pollutAnt, and is one of the six criteria air pol...

MUTAGENICITY IN LUNG OF BIG BLUE ((R) MICE AND INDUCTION OF TANDEM-BASE SUBSTITUTIONS IN SALMONELLA BY THE AIR POLLUTANT PEROXYACETYL NITRATE (PAN): PREDICTED FORMATION OF INTRASTRAND CROSS-LINKS

EPA Science Inventory

Peroxyacetyl nitrate (PAN) is a ubiquitous air pollutant formed from N02 reacting with acetoxy radicals generated from ambient aldehydes in the presence of sunlight and ozone. It contributes to eye irritation associated with photochemical smog and is present in most urban air. ...

Environmental Externalities in Electric Power Markets: Acid Rain, Urban Ozone, and Climate Change

EIA Publications

1995-01-01

This article discusses the emissions resulting from the generation of electricity by utilities and their role in contributing to the environmental problems of acid rain, urban ozone, and climate change.

Air quality during the 2008 Beijing Olympics: secondary pollutants and regional impact

NASA Astrophysics Data System (ADS)

Wang, T.; Nie, W.; Gao, J.; Xue, L. K.; Gao, X. M.; Wang, X. F.; Qiu, J.; Poon, C. N.; Meinardi, S.; Blake, D.; Ding, A. J.; Chai, F. H.; Zhang, Q. Z.; Wang, W. X.

2010-05-01

This paper presents the first results of the atmospheric measurements of trace gases and aerosols at three surface sites in and around Beijing before and during the 2008 Olympics. We focus on secondary pollutants including ozone, fine sulfate and nitrate, and the contribution of regional sources in summer 2008. The results reveal different responses of secondary pollutants to the control measures from primary pollutants. Ambient concentrations of vehicle-related nitrogen oxides (NOx) and volatile organic compounds (VOCs) at an urban site dropped by 25% and 20-45% in the first two weeks after full control was put in place, but the levels of ozone, sulfate and nitrate in PM2.5 increased by 16%, 64%, 37%, respectively, compared to the period prior to the full control; wind data and back trajectories indicated the contribution of regional pollution from the North China Plain. Air quality (for both primary and secondary pollutants) improved significantly during the Games, which were also associated with the changes in weather conditions (prolonged rainfall, decreased temperature, and more frequent air masses from clean regions). A comparison of the ozone data at three sites on eight ozone-pollution days, when the air masses were from the southeast-south-southwest sector, showed that regional pollution sources contributed 34%-88% to the peak ozone concentrations in urban Beijing. Ozone production efficiencies at two sites were low (~3 ppbv/ppbv), indicating that ozone formation was being controlled by VOCs. Compared with data collected in 2005 at a downwind site, the concentrations of ozone, sulfur dioxide (SO2), total sulfur (SO2+PM2.5 sulfate), carbon monoxide (CO), reactive aromatics (toluene and xylenes) sharply decreased (by 8-64%) in 2008, but no significant changes were observed for the concentrations of PM2.5, fine sulfate, total odd reactive nitrogen (NOy), and longer lived alkanes and benzene. We suggest that these results indicate the success of the government's efforts in reducing emissions of SO2, CO, and VOCs in Beijing. However, further control of regional emissions is needed for significant reductions of ozone and fine particulate pollution in Beijing.

Ozone pollution in China: A review of concentrations, meteorological influences, chemical precursors, and effects.

PubMed

Wang, Tao; Xue, Likun; Brimblecombe, Peter; Lam, Yun Fat; Li, Li; Zhang, Li

2017-01-01

High concentrations of ozone in urban and industrial regions worldwide have long been a major air quality issue. With the rapid increase in fossil fuel consumption in China over the past three decades, the emission of chemical precursors to ozone-nitrogen oxides and volatile organic compounds-has increased sharply, surpassing that of North America and Europe and raising concerns about worsening ozone pollution in China. Historically, research and control have prioritized acid rain, particulate matter, and more recently fine particulate matter (PM 2.5 ). In contrast, less is known about ozone pollution, partly due to a lack of monitoring of atmospheric ozone and its precursors until recently. This review summarizes the main findings from published papers on the characteristics and sources and processes of ozone and ozone precursors in the boundary layer of urban and rural areas of China, including concentration levels, seasonal variation, meteorology conducive to photochemistry and pollution transport, key production and loss processes, ozone dependence on nitrogen oxides and volatile organic compounds, and the effects of ozone on crops and human health. Ozone concentrations exceeding the ambient air quality standard by 100-200% have been observed in China's major urban centers such as Jing-Jin-Ji, the Yangtze River delta, and the Pearl River delta, and limited studies suggest harmful effect of ozone on human health and agricultural corps; key chemical precursors and meteorological conditions conductive to ozone pollution have been investigated, and inter-city/region transport of ozone is significant. Several recommendations are given for future research and policy development on ground-level ozone. Copyright © 2016 Elsevier B.V. All rights reserved.

Summary of measurement results of ozone, methane, and nonmethane hydrocarbons for C-54 aircraft. 1979 Southeastern Virginia Urban Plume Study

NASA Technical Reports Server (NTRS)

Cofer, W. R., III; Purgold, G. C.; Gregory, G. L.

1981-01-01

Methane, nonmethane hydrocarbon, and ozone data collected in a C-54 aircraft during the 1979 Southeastern Virginia Urban Plume Study are presented. Three major aircraft experiments were flown on five separate days in August collecting 20 hours of flight data. Direct correlation between ozone and hydrocarbon plumes was observed on several occasions.

The impact of air pollutants on rainwater chemistry during "urban-induced heavy rainfall" in downtown Tokyo, Japan

NASA Astrophysics Data System (ADS)

Uchiyama, Ryunosuke; Okochi, Hiroshi; Katsumi, Naoya; Ogata, Hiroko

2017-06-01

In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban-induced heavy rain), we analyzed inorganic ions in rainwater samples collected on an event basis over 5 years from October 2012 to December 2016 in Shinjuku, Tokyo. Hourly rainfall amounts and wet deposition fluxes of acidic components (the sum of H+, NH4+, NO3-, and nonsea-salt SO42-) in UHR were 13.1 and 17.8 times larger than those in normal rainfall, respectively, indicating that large amount of air pollutants were scavenged and deposited by UHR with large amounts of rainfall. The level of air pollutants, such as NO2, SO2, and potential ozone, in the ambient air increased just before the formation of UHR and decreased sharply at the end of the UHR event. These results indicate that NO2, which was formed secondarily by oxidants, was further oxidized by HO radicals and formed HNO3 just before the formation of UHR, which was subsequently scavenged by UHR.

Urban Summertime Ozone of China: Peak Ozone Hour and Nighttime Mixing

NASA Astrophysics Data System (ADS)

Qu, H.; Wang, Y.; Zhang, R.

2017-12-01

We investigate the observed diurnal cycle of summertime ozone in the cities of China using a regional chemical transport model. The simulated daytime ozone is in general agreement with the observations. Model simulations suggest that the ozone peak time and peak concentration are a function of NOx (NO + NO2) and volatile organic compound (VOC) emissions. The differences between simulated and observed ozone peak time and peak concentration in some regions can be applied to understand biases in the emission inventories. For example, the VOCs emissions are underestimated over the Pearl River Delta (PRD) region, and either NOx emissions are underestimated or VOC emissions are overestimated over the Yangtze River Delta (YRD) regions. In contrast to the general good daytime ozone simulations, the simulated nighttime ozone has a large low bias of up to 40 ppbv. Nighttime ozone in urban areas is sensitive to the nocturnal boundary-layer mixing, and enhanced nighttime mixing (from the surface to 200-500 m) is necessary for the model to reproduce the observed level of ozone.

Assessing and evaluating urban VOC emissions in mid-latitude megacities from intensive observations in Paris and Los Angeles

NASA Astrophysics Data System (ADS)

Borbon, A.; Gilman, J. B.; Kuster, W. C.; McKeen, S. A.; Holloway, J. S.; Gros, V.; Gaimoz, C.; Beekmann, M.; De Gouw, J. A.

2011-12-01

Volatile Organic Compounds (VOC) affect urban air quality and regional climate change by contributing to ozone formation and the build-up of Secondary Organic Aerosols (SOA). Quantification of VOC emissions is a first critical step to predict VOC environmental impacts and to design effective abatement strategies. Indeed, the quality of ozone and SOA forecasts strongly depends on an accurate knowledge of the primary VOC emissions. However, commonly used bottom-up approaches are highly uncertain due to source multiplicity (combustion processes, storage and distribution of fossil fuels, solvent use, etc.) because of numerous controlling factors (driving conditions, fuel type, temperature, radiation, etc.), and their great variability in time and space. Field observations of VOC and other trace gases can provide valuable top-down constraints to evaluate VOC emission inventories at urban scales. In addition, the implementation of emission reduction measures raises the question of the increasing importance of VOC sources other than traffic. Here, we will evaluate VOC emissions of two mid-latitude megacities in the Northern Hemisphere: the Greater Paris area (Europe) and Los Angeles (USA). In 2009 and 2010, three intensive field campaigns took place in Paris and Los Angeles in the framework of the MEGAPOLI (EU FP7) and CalNex-2010 projects, respectively. Very detailed measurements of aerosol composition and properties, and their gaseous VOC precursors were carried out at ground-based sites (urban center and suburban) and on various mobile platforms. This contribution uses a comprehensive suite of VOC measurements collected by GC-MS/FID techniques at ground-based sites in both cities by a source-receptor methodology. First, emission ratios were estimated from the observations (uncertainty of ± 20%) and compared regarding regional characteristics and European vs. Californian control policies. Then, determined emission ratios were used to assess the accuracy of up-to-date emission inventories. While emission ratios agree within the uncertainties for many VOCs, remarkable differences are observed for aromatic VOCs (C7-C9) depending on the season. Moreover, the evaluation of emission inventories shows large discrepancies for VOCs for which traffic is not the dominant source. Commonalities and/or differences are also discussed in term of implication for urban atmospheric chemistry (ozone and SOA formation potential) in both megacities.

Exploring the roles of temperature and NOx on ozone production in the Sacramento urban plume

NASA Astrophysics Data System (ADS)

Lafranchi, B. W.; Cohen, R. C.

2009-12-01

We investigate the role of temperature and NOx (NOx = NO+NO2) on ozone (O3) production in the Sacramento urban plume over a stretch of seven years (2001-2007) using data collected at UC Blodgett Forest Research Station (a forested site in the Sierra Nevadas about 80 km downwind of Sacramento, CA) and at a series of California Air Resources Board (CARB) sites along the Sacramento-Blodgett transect. The consistent daytime wind patterns between the Central Valley of California and the foothills of the Sierra Nevada mountains permits the assumption of plume transport from downtown Sacramento, over the CARB monitoring sites in the eastern suburbs, and past the Blodgett Forest research site. While NOx emissions are limited primarily to the urban and suburban regions of the transect, biogenic volatile organic compound (VOC) emissions are significant throughout the transect, thus there is a fast transition from VOC-limited to NOx-limited as the plume travels away from the urban center, and we have the opportunity to analyze the differences in ozone production across these two chemical regimes. For this analysis, the Sacramento-Blodgett transect is separated into three segments: urban, suburban, and rural, defined by the locations of selected monitoring sites. Ozone concentrations across each segment are controlled by chemical production (Pchem) and loss (Lchem), deposition to surfaces (Ldep), and mixing with background air (Lmix). At an assumed deposition rate, mixing rate, and background O3 concentration, the net chemical flux of ozone (Pchem - Lchem) can be inferred from differences in ozone concentrations between adjacent monitoring sites. We show that ozone production rates, in general, increase with temperature. We also show that decreases in NOx emissions over the period from 2001-2007 have been effective at reducing ozone production at all points along the transect, but only on days where temperatures are highest. At low temperatures, this decrease is less apparent, and in the urban transect, ozone production is observed to increase as NOx concentrations decrease. This is attributed to the high NOx/VOC ratio that results from reduced biogenic emissions and strong local inputs of NOx, thus driving the chemical environment into a NOx-saturated regime. From these results, we give predictions of future ozone exceedences for various emissions and climate scenarios.

In situ ozone data for evaluation of the laser absorption spectrometer ozone remote sensor: 1979 southeastern Virginia urban plume study summer field program

NASA Technical Reports Server (NTRS)

Gregory, G. L.; Mcdougal, D. S.; Mathis, J. J., Jr.

1980-01-01

Ozone data from the 1979 Southeastern Virginia Urban Study (SEV-UPS) field program are presented. The SEV-UPS was conducted for evaluation of an ozone remote sensor, the Laser Absorption Spectrometer. During the measurement program, remote-sensor evaluation was in two areas; (1) determination of the remote sensor's accuracy, repeatability, and operational characteristics, and (2) demonstration of the application of remotely sensed ozone data in air-quality studies. Data from six experiments designed to provide in situ ozone data for evaluation of the sensor in area 1, above, are presented. Experiments consisted of overflights of a test area with the remote sensor aircraft while in situ measurements with a second aircraft and selected surface stations provided correlative ozone data within the viewing area of the remote sensor.

Effects of the Bermuda High and the Great Plains low-level jet upon background and peak ozone concentrations in Texas urban areas

NASA Astrophysics Data System (ADS)

Estes, M. J.; Wang, Y.; Lei, R.; Wang, S. C.; Jia, B.

2017-12-01

Previous studies have established that the westward extent of the Bermuda High is strongly linked to the ozone concentrations in Houston. This study examines the linkages between the Bermuda High, the Great Plains low-level jet, background ozone in the eastern half of Texas, and local contributions to peak ozone in Texas urban areas. Analysis of North American Regional Reanalysis (NARR) wind and pressure fields will be used to establish the presence and strength of synoptic-scale weather features, and this information will be used with ozone data from air quality networks to determine the effects upon the seasonal and interannual variations of ozone. Quantification of the effects of large-scale meteorological factors will improve understanding of the causes of ozone variations, including decadal trends in Texas cities.

Enhancement of bromate formation by pH depression during ozonation of bromide-containing water in the presence of hydroxylamine.

PubMed

Yang, Jingxin; Li, Ji; Dong, Wenyi; Ma, Jun; Yang, Yi; Li, Jiayin; Yang, Zhichao; Zhang, Xiaolei; Gu, Jia; Xie, Wanying; Cang, Yan

2017-02-01

This work investigated the fate of bromate formation during ozonation in the presence of hydroxylamine (HA). Results indicated that pH depression, as a commonly feasible control strategy for bromate formation during ozonation, unexpectedly enhanced the bromate formation during ozonation in the presence of HA. A dramatically high level of bromate was observed at acidic pH in the ozone/HA process. The scavenging experiments demonstrated the essential role of OH produced in the reaction of ozone with HA in bromate formation. In the process, OH mainly oxidizes bromide to Br, which is further oxidized by ozone and eventually converts to bromate. Further investigations suggested that the unexpected enhancement on bromate formation by pH depression can be mainly ascribed to the pH-dependent ozone decay, OH exposures and formation rate of Br. As pH decreased from 7 to 5, the reduced OH scavenging capacity of HA led to higher OH exposures, which contributed to the enhancement of bromate formation. As pH decreased from 5 to 3, the enhanced formation rate of Br largely augmented the formation of bromate. In addition, the ozone decay slowed down by pH depression provided more available ozone for the oxidation of the formed Br to bromate. The enhanced effect of pH depression on bromate formation was still observed in the real water samples in the ozone/HA process. Accordingly, pH depression might be avoided to control the bromate formation during ozonation in the presence of HA. Copyright © 2016 Elsevier Ltd. All rights reserved.

Volatile organic compounds speciation and their influence on ozone formation potential in an industrialized urban area in Brazil.

PubMed

Galvão, Elson Silva; Santos, Jane Meri; Reis Junior, Neyval Costa; Stuetz, Richard Michael

2016-09-01

Speciation and the influence on the ozone formation potential (OFP) from volatile organic compounds (VOCs) have been studied between February June 2013 in Vitória, ES, Brazil. Passive samplers were installed at three air-quality monitoring stations and a total of 96 samplings were collected. A total of 78 VOCs were characterized by gas chromatograph-mass spectrometer. The predominant group was organic acids, followed by alcohols and substituted aromatics and 14 precursor species were quantified. An analysis correlating concentrations with wind direction was conducted to identify possible sources. The OFP was calculated applying the scale of maximum incremental reactivity proposed by Carter.[ 23 ] Ozone precursors with the greatest OFP such as undecane, toluene, ethylbenzene and m, p-xylene compounds were the most abundant with means of 0.855, 0.365, 0.259 and 0.289 µg m(-3), respectively. The benzene, toluene, ethylbenzene and xylene (BTEX) group was found below the limits considered harmful to the health of the population living in Vitória. The OFP calculated for the precursors group was 22.55 µg m(-3) for the rainy season and 32.11 µg m(-3) for the dry season. The VOC/NOx ratio in Vitória is approximately 1.71, indicating that the region has a VOC-limiting condition for the production of ozone.

The Impact of TexAQS 2000 on Air Quality Planning in Houston

NASA Astrophysics Data System (ADS)

Thomas, J. W.; Price, J. H.

2002-12-01

Before the Texas 2000 Air Quality Study (TexAQS 2000) the State used the Urban Airshed Model to model nine different episodes in Houston with very poor results: only one episode met EPA model performance criteria. Questions existed regarding emissions uncertainties, meteorological modeling, and model chemistry. NOAA, DOE, and SOS led more than 35 organizations and 250 investigators who participated in TexAQS 2000. Major findings from TexAQS 2000 are: 1. There are two types of meteorological patterns that lead to ozone episodes in the Houston area: (i) stagnation associated with the sea breeze flow reversal causes a pool of industrial emissions and ozone to accumulate, then to move across the city as the wind flow picks up and (ii) plumes of ozone form when relatively persistent winds carry the emissions away from the city and industrial areas. 2. The chemistry that produces high ozone concentrations and rapid rises in ozone in the Houston area has been explained: multiple investigators in TexAQS 2000 have documented more rapid and more efficient formation of ozone in the plume from the Houston industrial area than any of them has observed in any previous field study. Houston's exceptionally rapid ozone formation arises from large amounts of anthropogenic VOCs in the atmosphere, often from the same plants that provide sufficient NOx. 3. This rapid and efficient ozone formation results most often from the presence of a specific subclass of hydrocarbons called light olefins, primarily ethylene and propylene. 4. Sometimes it is other specific hydrocarbons that cause the rapid formation of high concentrations of ozone, and sometimes it is just the total mass of a lot of relatively unreactive hydrocarbons. 5. The current emissions inventory for ethylene and propylene, as well as other VOCs, underestimates their routine emissions by a factor of roughly five to ten or perhaps even more. 6. It is not clear whether the emissions causing Houston's rapid ozone formation are the results of upsets or of routine operations or both. Each of the research groups in TexAQS 2000 has found that the data are consistent with routine emissions; however, their analyses do not exclude the possibility of multiple releases per day that would not be readily distinguishable from continuous emissions. 7. Further analysis of the data collected in 2000 and 2001 will be necessary to refine the estimates of the discrepancy between reported and actual VOC emissions and assign top-down VOC emissions inventory corrections for the current round of regulatory modeling. 8. Additional work will need to continue for the next few years with the cooperation of industry to develop an adequate bottom-up emissions inventory for VOCs. 9. The opportunity to compare regulatory modeling results to state-of-the-science aircraft measurements is a major advance in determining whether photochemical models are getting the right answers for the right reasons. Doing so is critical to development of effective and cost-effective control strategies. Without TexAQS 2000 and subsequent findings, the one-hour ozone control strategies for Houston would not address the problem correctly. What's next? The challenges of the impending 8-hour ozone standard will demand even more precision in our technical work to develop efficient and cost-effective strategies to demonstrate attainment. There is a proposal to conduct another major field study in 2005 to build on our current understanding of the science for ozone, fine particulate matter, and regional haze in Texas.

Temporal and Spatial Variation in, and Population Exposure to, Summertime Ground-Level Ozone in Beijing

PubMed Central

Zheng, Youfei; Li, Ting; Wei, Li; Guan, Qing

2018-01-01

Ground-level ozone pollution in Beijing has been causing concern among the public due to the risks posed to human health. This study analyzed the temporal and spatial distribution of, and investigated population exposure to, ground-level ozone. We analyzed hourly ground-level ozone data from 35 ambient air quality monitoring sites, including urban, suburban, background, and traffic monitoring sites, during the summer in Beijing from 2014 to 2017. The results showed that the four-year mean ozone concentrations for urban, suburban, background, and traffic monitoring sites were 95.1, 99.8, 95.9, and 74.2 μg/m3, respectively. A total of 44, 43, 45, and 43 days exceeded the Chinese National Ambient Air Quality Standards (NAAQS) threshold for ground-level ozone in 2014, 2015, 2016, and 2017, respectively. The mean ozone concentration was higher in suburban sites than in urban sites, and the traffic monitoring sites had the lowest concentration. The diurnal variation in ground-level ozone concentration at the four types of monitoring sites displayed a single-peak curve. The peak and valley values occurred at 3:00–4:00 p.m. and 7:00 a.m., respectively. Spatially, ground-level ozone concentrations decreased in gradient from the north to the south. Population exposure levels were calculated based on ground-level ozone concentrations and population data. Approximately 50.38%, 44.85%, and 48.49% of the total population of Beijing were exposed to ground-level ozone concentrations exceeding the Chinese NAAQS threshold in 2014, 2015, and 2016, respectively. PMID:29596366

Temporal and Spatial Variation in, and Population Exposure to, Summertime Ground-Level Ozone in Beijing.

PubMed

Zhao, Hui; Zheng, Youfei; Li, Ting; Wei, Li; Guan, Qing

2018-03-29

Ground-level ozone pollution in Beijing has been causing concern among the public due to the risks posed to human health. This study analyzed the temporal and spatial distribution of, and investigated population exposure to, ground-level ozone. We analyzed hourly ground-level ozone data from 35 ambient air quality monitoring sites, including urban, suburban, background, and traffic monitoring sites, during the summer in Beijing from 2014 to 2017. The results showed that the four-year mean ozone concentrations for urban, suburban, background, and traffic monitoring sites were 95.1, 99.8, 95.9, and 74.2 μg/m³, respectively. A total of 44, 43, 45, and 43 days exceeded the Chinese National Ambient Air Quality Standards (NAAQS) threshold for ground-level ozone in 2014, 2015, 2016, and 2017, respectively. The mean ozone concentration was higher in suburban sites than in urban sites, and the traffic monitoring sites had the lowest concentration. The diurnal variation in ground-level ozone concentration at the four types of monitoring sites displayed a single-peak curve. The peak and valley values occurred at 3:00-4:00 p.m. and 7:00 a.m., respectively. Spatially, ground-level ozone concentrations decreased in gradient from the north to the south. Population exposure levels were calculated based on ground-level ozone concentrations and population data. Approximately 50.38%, 44.85%, and 48.49% of the total population of Beijing were exposed to ground-level ozone concentrations exceeding the Chinese NAAQS threshold in 2014, 2015, and 2016, respectively.

Sources of C₂-C₄ alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region.

PubMed

Zhang, Yanli; Wang, Xinming; Zhang, Zhou; Lü, Sujun; Huang, Zhonghui; Li, Longfeng

2015-01-01

Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Multiscale multifractal properties between ground-level ozone and its precursors in rural area in Hong Kong.

PubMed

He, Hong-di; Qiao, Zhong-Xia; Pan, Wei; Lu, Wei-Zhen

2017-07-01

In rural area, due to the reduction of NOx and CO emitted from vehicle exhausts, the ozone photochemical reaction exhibits relatively weak effect and ozone formation presents different pattern with its precursors in contrast to urban situation. Hence, in this study, we apply detrended cross-correlation analysis to investigate the multifractal properties between ozone and its precursors in a rural area in Hong Kong. The observed databases of ozone, NO 2 , NOx and CO levels during 2005-2014 are obtained from a rural monitoring station in Hong Kong. Based on the collected database, the cross-correlation analysis is carried out firstly to examine the cross-correlation patterns and the results indicate that close interactive relations exist between them. Then the detrended cross-correlation analysis is performed for further analysis. The multifractal characters occur between ozone and its precursors. The long-term cross-correlations behaviors in winter are verified to be stronger than that in other seasons. Additionally, the method is extended on daily averaged data to explore the multifractal property on various time scales. The long-term cross-correlation behavior of ozone vs NO 2 and NOx on daily basis becomes weaker while that of ozone vs CO becomes stronger. The multifractal properties for all pairs in summer are found to be the strongest among the whole year. These findings successfully illustrate that the multifractal analysis is a useful tool for describing the temporal scaling behaviors of ozone trends in different time series in rural areas. Copyright © 2017 Elsevier Ltd. All rights reserved.

The impact of urban canopy meteorological forcing on summer photochemistry

NASA Astrophysics Data System (ADS)

Huszár, Peter; Karlický, Jan; Belda, Michal; Halenka, Tomáš; Pišoft, Petr

2018-03-01

The regional climate model RegCM4.4, including the surface model CLM4.5, was offline coupled to the chemistry transport model CAMx version 6.30 in order to investigate the impact of the urban canopy induced meteorological changes on the longterm summer photochemistry over central Europe for the 2001-2005 period. First, the urban canopy impact on the meteorological conditions was calculated performing a reference experiment without urban landsurface considered and an experiment with urban surfaces modeled with the urban parameterization within the CLM4.5 model. In accordance with expectations, strong increases of urban surface temperatures (up to 2-3 K), decreases of wind speed (up to -1 ms-1) and increases of vertical turbulent diffusion coefficient (up to 60-70 m2s-1) were found. For the impact on chemistry, these three components were considered. Additionally, we accounted for the effect of temperature enhanced biogenic emission increase. Several experiments were performed by adding these effects one-by-one to the total impact: i.e., first, only the urban temperature impact was considered driving the chemistry model; secondly, the wind impact was added and so on. We found that the impact on biogenic emission account for minor changes in the concentrations of ozone (O3), oxides of nitrogen NOx = NO + NO2 and nitric acid (HNO3). On the other hand, the dominating component acting is the increased vertical mixing, resulting in up to 5 ppbv increase of urban ozone concentrations while causing -2 to -3 ppbv decreases and around 1 ppbv increases of NOx and HNO3 surface concentrations, respectively. The temperature impact alone results in reduction of ozone, increase in NO, decrease in NO2 and increases of HNO3. The wind impact leads, over urban areas, to ozone decreases, increases of NOx and a slight increase in HNO3. The overall impact is similar to the impact of increased vertical mixing alone. The Process Analysis (PA) technique implemented in CAMx was adopted to investigate the causes of the modeled impacts in more details. It showed that the main process contributing to the temperature impact on ozone is a dry-deposition enhancement, while the dominating process controlling the wind impact on ozone over cities is the advection reduction. In case of the impact of enhanced turbulence, PA suggests that ozone increases are, again as assumed, the result of increased downward vertical mixing supported by reduced chemical loss. Comparing the model concentrations with measurements over urban areas, a slight improvement of the model performance was achieved during afternoon hours if urban canopy forcing on chemistry via meteorology was accounted for. The study demonstrates that disregarding the urban canopy induced meteorological effects in air-quality oriented modeling studies can lead to erroneous results in the calculated species concentrations. However, it also shows that the individual components are not equally important: urban canopy induced turbulence effects dominate while the wind-speed and temperature related ones are of considerably smaller magnitude.

Process Analysis of Typhoon Related Ozone Pollution over the Pearl River Delta during the PRIDE-PRD2006

NASA Astrophysics Data System (ADS)

Li, Y.; Wang, X.; Zhang, Y.

2014-12-01

There were two typhoon processes during Campaign PRIDE-PRD2006 in July 2006 and serious ozone pollution episodes occurred before the landing of the typhoons. Chemical transport model CMAQ was employed in this work to simulate the ozone pollution episode related by the typhoon KAEMI. According to the meteorological conditions, the pollution episode could be divided into three phases with the movement of the typhoon, which were (1) far away from the continent; (2) coming close to the continent; (3) before landing. Process analysis was applied to get the contributions of physical and chemical processes for the ozone. It revealed that transport process was dominant during this pollution episode, and the influence of chemical process increased in the second phase. Three typical regions, northern rural area, urban area and Hong Kong area, were selected to study the contribution of each chemical and physical process. In the first phase, the primary process in northern rural area and the urban area was vertical diffusion, accounting for 47% and 46% respectively. In the second phase, the primary process in northern rural area and the urban area was chemical process, accounting for 33% and 31% respectively. In the third phase, the region of high concentration ozone moved southward. For Hong Kong area, the western inflow was prominent as 40%. Sensitivity study showed that urban areas were VOCs-limited regime with decreased ozone concentration when reducing the emission of VOCs. On the contrary, the ozone concentration in downwind rural areas decreased with the reduction of NOx, and the reason may be the decrement of the accumulated precursors.

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.

PARAMETER EVALUATION AND MODEL VALIDATION OF OZONE EXPOSURE ASSESSMENT USING HARVARD SOUTHERN CALIFORNIA CHRONIC OZONE EXPOSURE STUDY DATA

EPA Science Inventory

To examine factors influencing long-term ozone exposures by children living in urban communities, we analyzed longitudinal data on personal, indoor, and outdoor ozone concentrations as well as related housing and other questionnaire information collected in the one-year-long Harv...

USE OF AUXILIARY DATA FOR SPATIAL INTERPOLATION OF OZONE EXPOSURE IN SOUTHEASTERN FORESTS

EPA Science Inventory

In order to assess the impact of tropospheric ozone on forests, it is necessary to quantify ozone exposure on regional scales. Since ozone monitoring stations are widely scattered and mostly concentrate in urban and suburban areas, some form of spatial interpolation is necessary ...

Nitrate formation during ozonation as a surrogate parameter for abatement of micropollutants and the N-nitrosodimethylamine (NDMA) formation potential.

PubMed

Song, Yang; Breider, Florian; Ma, Jun; von Gunten, Urs

2017-10-01

In this study, nitrate formation from ammonium and/or dissolved organic nitrogen (DON) was investigated as a novel surrogate parameter to evaluate the abatement of micropollutants during ozonation of synthetic waters containing natural organic matter (NOM) isolates, a natural water and secondary wastewater effluents. Nitrate formation during ozonation was compared to the changes in UV absorbance at 254 nm (UVA 254 ) including the effect of pH. For low specific ozone doses UVA 254 was abated more efficiently than nitrate was formed. This is due to a relatively slow rate-limiting step for nitrate formation from the reaction between ozone and a proposed nitrogen-containing intermediate. This reaction cannot compete with the fast reactions between ozone and UV-absorbing moieties (e.g., activated aromatic compounds). To further test the kinetics of nitrate formation, two possible intermediates formed during ozonation of DON were tested. At pH 7, nitrate was formed during ozonation of acetone oxime and methyl nitroacetate with second-order rate constants of 256.7 ± 4.7 M -1  s -1 and 149.5 ± 5.8 M -1  s -1 , respectively. The abatement of the selected micropollutants (i.e., 17α-ethinylestradiol (EE2), carbamazepine (CBZ), bezafibrate (BZF), ibuprofen (IBU), and p-chlorobenzoic acid (pCBA)) was investigated for specific ozone doses ≤1.53 mgO 3 /mgDOC and its efficiency depended strongly on the reactivity of the selected compounds with ozone. The relative abatement of micropollutants (i.e., EE2 and CBZ) with high ozone reactivity showed linear relationships with nitrate formation. The abatement of micropollutants with intermediate-low ozone reactivity (BZF, IBU, and pCBA) followed one- and two-phase behaviors relative to nitrate formation during ozonation of water samples containing high and low concentrations of nitrate-forming DON, respectively. During ozonation of a wastewater sample, the N-nitrosodimethylamine formation potential (NDMA-FP) during chloramination decreased with increasing specific ozone doses. A good correlation was obtained between NDMA-FP abatement and nitrate formation. Therefore, nitrate formation after pre-ozonation may be a useful parameter to estimate the reduction of the NDMA-FP during post-chloramination. Overall, the results of this study suggest that nitrate formation (possibly in combination with UVA 254 abatement) during ozonation of DON-containing waters may be a good surrogate for assessing the abatement of micropollutants and the NDMA-FP. Copyright © 2017 Elsevier Ltd. All rights reserved.

Removal of Ozone by Urban and Peri-Urban Forests: Evidence from Laboratory, Field, and Modeling Approaches.

PubMed

Calfapietra, Carlo; Morani, Arianna; Sgrigna, Gregorio; Di Giovanni, Sara; Muzzini, Valerio; Pallozzi, Emanuele; Guidolotti, Gabriele; Nowak, David; Fares, Silvano

2016-01-01

A crucial issue in urban environments is the interaction between urban trees and atmospheric pollution, particularly ozone (O). Ozone represents one of the most harmful pollutants in urban and peri-urban environments, especially in warm climates. Besides the large interest in reducing anthropogenic and biogenic precursors of O emissions, there is growing scientific activity aimed at understanding O removal by vegetation, particularly trees. The intent of this paper is to provide the state of the art and suggestions to improve future studies of O fluxes and to discuss implications of O flux studies to maximize environmental services through the planning and management of urban forests. To evaluate and quantify the potential of O removal in urban and peri-urban forests, we describe experimental approaches to measure O fluxes, distinguishing laboratory experiments, field measurements, and model estimates, including recent case studies. We discuss the strengths and weaknesses of the different approaches and conclude that the combination of the three levels of investigation is essential for estimating O removal by urban trees. We also comment on the implications of these findings for planning and management of urban forests, suggesting some key issues that should be considered to maximize O removal by urban and peri-urban forests. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Quantifying VOC-Reaction Tracers, Ozone Production, and Continuing Aerosol Production Rates in Urban and Far-Downwind Atmospheres

NASA Technical Reports Server (NTRS)

Chatfield, Robert; Ren, X.; Brune, W.; Fried, A.; Schwab, J.

2008-01-01

We have found a surprisingly informative decomposition of the complex question of smoggy ozone production (basically, [HO2] in a more locally determined field of [NO]) in the process of linked investigations of modestly smoggy Eastern North America (by NASA aircraft, July 2004) and rather polluted Flushing, NYC (Queens College, July, 2001). In both rural and very polluted situations, we find that a simple contour graph parameterization of the local principal ozone production rate can be estimated using only the variables [NO] and j(sub rads) [HCHO]: Po(O3) = c (j(sub rads) [HCHO])(sup a) [HCHO](sup b). Here j(sub rads) is the photolysis of HCHO to radicals, presumably capturing many harder-UV photolytic processes and the principle ozone production is that due to HO2; mechanisms suggest that ozone production due to RO2 is closely correlated, often suggesting a limited range of different proportionality factors. The method immediately suggests a local interpretation for concepts of VOC limitation and NOx limitation. We believe that the product j(sub rads) [HCHO] guages the oxidation rate of observed VOC mixtures in a way that also provides [HO2] useful for the principle ozone production rate k [HO2] [NO], and indeed, all ozone chemical production. The success of the method suggests that dominant urban primary-HCHO sources may transition to secondary plume-HCHO sources in a convenient way. Are there other, simple, near-terminal oxidized VOC's which help guage ozone production and aerosol particle formation? Regarding particles, we report on, to the extent NASA Research resources allow, on appealing relationships between far-downwind (Atlantic PBL) HCHO and very fine aerosol (including sulfate. Since j(sub rads) [HCHO] provides a time-scale, we may understand distant-plume particle production in a more quantitative manner. Additionally we report on a statistical search in the nearer field for relationships between glyoxals (important near-terminal aromatic and isoprene reaction products) and aerosol production, looking for VOC's that might be most implicated. All three variables j(sub rads), [HCHO], and [NO] are relatively easily measured in widespread air pollution monitoring networks, and all are deducible form space-borne observations, though estimation of [NO] from [NO2] (the species observable from space) may require care. We report also on airborne and surface observations of HCHO, suggesting that concentrated (urban) and more diffuse (forest) sources may be distinguishable from space. The use of the 3.58 micron microwindow for HCHO remote sensing should allow much sharper resolution of HCHO than the UV. UV sensing requires large and expensive instruments, but even these seem justified since formaldehyde is so informative.

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

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

Kim, Saewung; Kim, So-Young; Lee, Meehye

Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Gangzhou, and Beijing are surrounded by densely forested areas and recent research has consistently demonstrated the importance of biogenic volatile organic compounds from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical concentrations, undermine our ability to assess regional photochemical air pollution problems. We present an observational dataset of CO, NOX, SO2, ozone, HONO, andmore » VOCs (anthropogenic and biogenic) from Taehwa Research Forest (TRF) near the Seoul Metropolitan Area (SMA) in early June 2012. The data show that TRF is influenced both by aged pollution and fresh BVOC emissions. With the dataset, we diagnose HOx (OH, HO2, and RO2) distributions calculated with the University of Washington Chemical Box Model (UWCM v 2.1). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that 1) different model simulation scenarios cause systematic differences in HOX distributions especially OH levels (up to 2.5 times) and 2) radical destruction (HO2+HO2 or HO2+RO2) could be more efficient than radical recycling (HO2+NO) especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NOX sensitivity and oxidation product formation rates. Overall, the VOC limited regime in ozone photochemistry is predicted but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO2 levels are positively correlated with OVOCs production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher than expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.« less

COMPASS - COMparative Particle formation in the Atmosphere using portable Simulation chamber Study techniques

NASA Astrophysics Data System (ADS)

Bonn, B.; Sun, S.; Haunold, W.; Sitals, R.; van Beesel, E.; dos Santos, L.; Nillius, B.; Jacobi, S.

2013-12-01

In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes, such as particle formation online, and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically, with a residence time xT (COMPASS1) = 26.5 ± 0.3 min and xT (COMPASS2) = 26.6 ± 0.4 min, at a typical flow rate of 15 L min-1 and a gas leak rate of (1.6 ± 0.8) × 10-5 s-1. Particle loss rates were found to be larger (due to the particles' stickiness to the chamber walls), with an extrapolated maximum of 1.8 × 10-3 s-1 at 1 nm, i.e. a hundredfold of the gas leak rate. This latter value is associated with sticky non-volatile gaseous compounds, too. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system, a set of experiments was conducted under different conditions, i.e. urban and remote, enhanced ozone and terpenes as well as reduced sunlight. In order to do so, an ozone lamp was applied to enhance ozone in one of two chambers; the measurement chamber was protected from radiation by a first-aid cover and volatile organic compounds (VOCs) were added using a small additional flow and a temperature-controlled oven. During the elevated ozone period, ambient particle number and volume increased substantially at urban and remote conditions, but by a different intensity. Protection of solar radiation displayed a clear negative effect on particle number, while terpene addition did cause a distinct daily pattern. E.g. adding β pinene particle number concentration rose by 13% maximum at noontime, while no significant effect was observable during darkness. Therefore, the system is a useful tool for investigating local precursors and the details of ambient particle formation at surface locations as well as potential future feedback processes.

Characterization of Nonmethane Hydrocarbons at Three Urban Sites in Western Saudi Arabia, in Lahore (Pakistan), and in Singapore

NASA Astrophysics Data System (ADS)

Barletta, B.; Simpson, I. J.; Blake, N. J.; Meinardi, S.; Aburizaiza, O. S.; Siddique, A.; Zeb, J.; Yu, L. E.; Khwaja, H. A.; Farrukh, M. A.; Blake, D. R.

2014-12-01

Favorable conditions to tropospheric ozone (O3) formation are present over the Persian Gulf Region. Ozone is a well known pollutant affecting human health and natural ecosystems. Among the several factors contributing to the formation of the O3 hot spot over the Middle East, the presence of local emissions of its precursors needs to be considered. We report initial measurements of a suite of nonmethane hydrocarbons (NMHCs), an important component of volatile organic compounds (VOCs), which, coupled with nitrogen oxides in the presence of sunlight, are key chemical precursors of tropospheric O3. We measured 63 speciated C2-C10 NMHCs, in addition to methane (CH4) and carbon monoxide (CO) in three cities of Saudi Arabia (Jeddah, Mecca, and Madina; October-November 2012 and April 2013) and in the city of Lahore (Pakistan; December 2012). To put these data into perspective, we compare our results to data collected in Singapore (August-November 2012). We observed enhanced levels in all three Saudi Arabian cities compared to the local background and to those measured in Singapore. However, the Saudi levels are much lower than those measured in Lahore, where the sum of quantified NMHCs is about six times higher. For Madina, enhanced levels of the alkenes, ethyne and CO indicated that vehicle exhaust was the dominant source. In Jeddah and Mecca, the most abundant NMHC were the alkanes (47-61% of total measured NMHCs), which are more closely associated with emissions from natural gas, liquid petroleum gas (LPG), and gasoline evaporation. In Lahore, the hydroxyl radical (OH) reactivity, used to evaluate the importance of the different measured species toward ozone production, is three to six times higher than for the Saudi cities, and more than 20 times higher than for Singapore. For all urban areas reported here, among the measured compounds, the alkenes (especially ethene and propene) dominate in terms of OH reactivity because of a combination of their great abundance and relatively fast reaction rates with the hydroxyl radical. In light of the ozone hot spot detected over the Persian/Arabia Gulf our study shows the importance of different classes of NMHCs, or individual species, to the OH reactivity. This information can help policy makers regulate emissions in an attempt to reduce O3 formation by targeting key atmospheric pollutants.

Removing PAHs from urban runoff water by combining ozonation and carbon nano-onions.

PubMed

Sakulthaew, Chainarong; Comfort, Steve D; Chokejaroenrat, Chanat; Li, Xu; Harris, Clifford E

2015-12-01

Ozone (O3) is a chemical oxidant capable of transforming polycyclic aromatic hydrocarbons (PAHs) in urban runoff within minutes but complete oxidation to CO2 can take days to weeks. We developed and tested a flow-through system that used ozone to quickly transform PAHs in a runoff stream and then removed the ozone-transformed PAHs via adsorption to carbon nano-onions (CNOs). To quantify the efficacy of this approach, (14)C-labeled phenanthrene and benzo(a)pyrene, as well as a mixture of 16 unlabeled PAHs were used as test compounds. These PAHs were pumped from a reservoir into a flow-through reactor that continuously ozonated the solution. Outflow from the reactor then went to a chamber that contained CNOs to adsorb the ozone-transformed PAHs and allowed clean water to pass. By adding a microbial consortium to the CNOs following adsorption, we observed that bacteria were able to degrade the adsorbed products and release more soluble, biodegradable products back into solution. Control treatments confirmed that parent PAH structures (i.e., non-ozonated) were not biologically degraded following CNO adsorption and that O3-transformed PAHs were not released from the CNOs in the absence of bacteria. These results support the combined use of ozone, carbon nano-onions with subsequent biological degradation as a means of removing PAHs from urban runoff or a commercial waste stream. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fast mineralization and detoxification of amoxicillin and diclofenac by photocatalytic ozonation and application to an urban wastewater.

PubMed

Moreira, Nuno F F; Orge, Carla A; Ribeiro, Ana R; Faria, Joaquim L; Nunes, Olga C; Pereira, M Fernando R; Silva, Adrián M T

2015-12-15

The degradation of two organic pollutants (amoxicillin and diclofenac) in 0.1 mM aqueous solutions was studied by using advanced oxidation processes, namely ozonation, photolysis, photolytic ozonation, photocatalysis and photocatalytic ozonation. Diclofenac was degraded quickly under direct photolysis by artificial light (medium-pressure vapor arc, λ(exc) > 300 nm), while amoxicillin remained very stable. In the presence of ozone, regardless of the type of process, complete degradation of both organic pollutants was observed in less than 20 min. Photolysis or ozonation on their own led to modest values of total organic carbon (TOC) removal (<6% or 41%, respectively in 180 min), while for photocatalysis (no ozone present) a significant fraction of nonoxidizable compounds remained in the treated water (∼15% after 180 min). In the case of photolytic ozonation, the kinetics of TOC removal was slow. In contrast, a relatively fast and complete mineralization of amoxicillin and diclofenac (30 and 120 min, respectively) was achieved when applying the photocatalytic ozonation process. The absence of toxicity of the treated waters was confirmed by growth inhibition assays using two different microorganisms, Escherichia coli and Staphylococcus aureus. Photocatalytic ozonation was also applied to an urban wastewater spiked with both amoxicillin and diclofenac. The parent pollutants were easily oxidized, but the TOC removal was only as much as 68%, mainly due to the persistent presence of oxamic acid in the treated sample. The same treatment allowed the effective degradation of a wide group of micropollutants (pesticides, pharmaceuticals, hormones and an industrial compound) detected in non-spiked urban wastewater. Copyright © 2015 Elsevier Ltd. All rights reserved.

The role of a peri-urban forest on air quality improvement in the Mexico City megalopolis.

PubMed

Baumgardner, Darrel; Varela, Sebastian; Escobedo, Francisco J; Chacalo, Alicia; Ochoa, Carlos

2012-04-01

Air quality improvement by a forested, peri-urban national park was quantified by combining the Urban Forest Effects (UFORE) and the Weather Research and Forecasting coupled with Chemistry (WRF-Chem) models. We estimated the ecosystem-level annual pollution removal function of the park's trees, shrub and grasses using pollution concentration data for carbon monoxide (CO), ozone (O(3)), and particulate matter less than 10 microns in diameter (PM(10)), modeled meteorological and pollution variables, and measured forest structure data. Ecosystem-level O(3) and CO removal and formation were also analyzed for a representative month. Total annual air quality improvement of the park's vegetation was approximately 0.02% for CO, 1% for O(3,) and 2% for PM(10), of the annual concentrations for these three pollutants. Results can be used to understand the air quality regulation ecosystem services of peri-urban forests and regional dynamics of air pollution emissions from major urban areas. Copyright © 2011 Elsevier Ltd. All rights reserved.

The Impacts of Policies To Meet The UK Climate Change Act Target on Air Quality - An Explicit Modelling Study

NASA Astrophysics Data System (ADS)

Williams, M.; Beevers, S.; Lott, M. C.; Kitwiroon, N.

2016-12-01

This paper presents a preliminary analysis of different pathways to meet the UK Climate Change Act target for 2050, of an 80% reduction in carbon dioxide equivalent emissions on a base year of 1990. The pathways can result in low levels of air pollution emissions through the use of renewables and nuclear power. But large increases in biomass burning and the continued use of diesel cars they can result in larger air quality impacts. The work evaluated the air quality impacts in several pathways using an energy system optimisation model (UK TIMES) and a chemical transport model (CMAQ). The work described in this paper goes beyond the `damage cost' approach where only emissions in each are assessed. In this work we used scenarios produced by the UK TIMES model which we converted into air pollution emissions. Emissions of ammonia from agriculture are not attributed to the energy system and are thus not captured by energy system models, yet are crucial in forming PM2.5, acknowledged to be currently the most important pollutant associated with premature deaths. Our model includes these emissions and other non-energy sources of hydrocarbons which lead to the formation of ozone, another significant cause of air pollution health impacts. A key policy issue is how much biogenic hydrocarbons contribute to ozone formation compared with man-made emissions. We modelled pollution concentrations at a resolution of 7 km across the UK and at 2km in urban areas. These results allow us to estimate changes in premature mortality and morbidity associated with the changes in air pollution and subsequently the economic cost of the impacts on public health. The work shows that in the `clean' scenario, urban exposures to particles (PM2.5) and NO2 could decrease by very large amounts, but ozone exposures are likely to increase without further significant reductions world-wide. Large increases in biomass use however could lead to increases in urban levels of carcinogens and primary PM.

Modeling the influence of biogenic volatile organic compound emissions on ozone concentration during summer season in the Kinki region of Japan

NASA Astrophysics Data System (ADS)

Bao, Hai; Shrestha, Kundan Lal; Kondo, Akira; Kaga, Akikazu; Inoue, Yoshio

2010-01-01

Tropospheric ozone adversely affects human health and vegetation, and biogenic volatile organic compound (BVOC) emission has potential to influence ozone concentration in summer season. In this research, the standard emissions of isoprene and monoterpene from the vegetation of the Kinki region of Japan, estimated from growth chamber experiments, were converted into hourly emissions for July 2002 using the temperature and light intensity data obtained from results of MM5 meteorological model. To investigate the effect of BVOC emissions on ozone production, two ozone simulations for one-month period of July 2002 were carried out. In one simulation, hourly BVOC emissions were included (BIO), while in the other one, BVOC emissions were not considered (NOBIO). The quantitative analyses of the ozone results clearly indicate that the use of spatio-temporally varying BVOC emission improves the prediction of ozone concentration. The hourly differences of monthly-averaged ozone concentrations between BIO and NOBIO had the maximum value of 6 ppb at 1400 JST. The explicit difference appeared in urban area, though the place where the maximum difference occurred changed with time. Overall, BVOC emissions from the forest vegetation strongly affected the ozone generation in the urban area.

Exploration on the technology for ozone reduction in urban sewage treatment

NASA Astrophysics Data System (ADS)

Yang, Min; Sun, Yi; Han, Zhicheng; Liu, Jun

2017-05-01

With the rapid development of China’s economy, urban water consumption is increasing. However, sewage treatment plants will produce large amounts of sludge after treatment of sewage. Generally, and the sludge treatment costs are relatively high. Therefore, the problem about how to deal with the sewage sludge becomes the hot issues. Municipal waste water treatment plant produces a lot of sludge. This paper summarized the abroad study of ozonation minimization technology. Introduction and discussion were made on the principle of ozonated efficiency of sludge minimization, the efficiency of sludge minimization and the relationship between efficiency and ozone dosage, as well the effect of return sludge ozonated on waste water treatment running and the sludge setting and the dewatering characteristic. The economic estimation was also made on this technology. It’s showed that sludge minimization technology exhibits extensive application foreground.

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.

ROLE OF NITROGEN OXIDES IN NONURBAN OZONE FORMATION IN THE PLANETARY BOUNDARY LAYER OVER N (NORTH) AMERICA, W (WESTERN) EUROPE AND ADJACENT AREAS OF OCEAN

EPA Science Inventory

The status of knowledge on photochemical ozone formation and the effects of nitrogen oxides and peroxyacyl nitrates on such formation has been evaluated. The literature is reviewed on nonurban ozone and nitrogen oxide concentration distributions, ozone lifetimes, nitrogen oxide l...

[Influencing Factors of Assimilable Organic Carbon (AOC) Formation in Drinking Water During Ozonation Process].

PubMed

Dong, Bing-zhi; Zhang, Jia-li; He, Chang

2016-05-15

The influences of ozone dosage, pH and ionic strength on the formation of Assimilable Organic Carbon (AOC) during ozonation were investigated. The result demonstrated that within the range of 1-5 mg · L⁻¹ O₃, the formation of AOC increased with increasing ozone dosage, but higher ozone dosage (9 mg · L⁻¹) resulted in reduction of AOC formation. AOC formation increased with higher pH but decreased with increasing ionic strength. The result also showed that AOC formation with hydrophobic fraction (HPO) was the most, followed by transphilic fraction (TPI), and charged hydrophilic fraction (CHPI), while neutral hydrophilic fraction (NHPI) was the least. It was found that AOC formation related closely with SUVA of small molecular weight organics, and the lower SUVA produced more AOC.

Ozone from Wildfires: Peering through the Smog

NASA Astrophysics Data System (ADS)

Jaffe, D. A.; Baylon, P.; Wigder, N. L.; Collier, S.; Zhou, S.; Zhang, Q.; Alvarado, M. J.

2014-12-01

In the western US, many areas are near the current air quality standard for O3. Yet there is substantial inter-annual variability (IAV) in the number of days that exceed the O3 air quality threshold (currently 75 ppbv for an 8-hour average). We propose that wildfires are the dominant cause for this IAV. However there are large uncertainties around O3 production from wildfires due to numerous complicating factors. Ozone formation in wildfire plumes differs substantially from urban O3 production in several ways: substantial variations in the emissions, much larger aerosol loadings, a much greater variety of reactive and oxygenated VOCs, rapid and substantial formation of PAN and very different sources of HOx in the plume. These factors make it challenging to model wildfire impacts on photochemistry in the usual way. In this presentation we will show examples of three common situations based on data from the Mt. Bachelor Observatory: Rapid O3 formation (within one day) in a wildfire plume. Slow, but substantial, O3 formation (over days to a week) in a wildfire plume. No detectable O3 formation in a wildfire plume. We will interpret these results with respect to the observed NOy mixing ratios, the photochemical environment, the combustion efficiency, the plume transport and other factors and suggest some key experiments and modeling studies that can help further our understanding of wildfire O3 production.

Impact Assessment of Global Temperature Perturbations on Urban and Regional Ozone Levels in South Texas

NASA Astrophysics Data System (ADS)

Biswas, Jhumoor; John, Kuruvilla; Farooqui, Zuber

The recent Intergovernmental Panel on Climate Change report predicts significant temperature increases over the century which constitutes the pulse of climate variability in a region. A modeling study was performed to identify the potential impact of temperature perturbations on tropospheric ozone concentrations in South Texas. A future case modeling scenario which incorporates appropriate emission reduction strategies without accounting for climatic inconsistencies was used in this study. The photochemical modeling was undertaken for a high ozone episode of 13-20 September 1999, and a future modeling scenario was projected for ozone episode days in 2007 utilizing the meteorological conditions prevalent in the base year. The temperatures were increased uniformly throughout the simulation domain and through the vertical layers by 2°C, 3°C, 4°C, 5°C, and 6°C, respectively in the future year modeling case. These temperature perturbations represented the outcome of extreme climate change within the study region. Significantly large changes in peak ozone concentrations were predicted by the photochemical model. For the 6°C temperature perturbation, the greatest amplification in the maximum 8-h ozone concentrations within urban areas of the modeling domain was approximately 12 ppb. In addition, transboundary flux from major industrialized urban areas played a major role in supplementing the high ozone concentrations during the perturbed temperature scenarios. The Unites States Environmental Protection Agency (USEPA) is currently proposing stricter 8-h ozone standards. The effect of temperature perturbations on ozone exceedances based on current and potential stringent future National Ambient Air Quality Standards (NAAQS) was also studied. Temperatures had an appreciable spatial impact on the 8-h ozone exceedances with a considerable increase in spatial area exceeding the NAAQS for the 8-h ozone levels within the study region for each successive augmentation in temperature. The number of exceedances of the 8-h ozone standard increased significantly with each degree rise of temperature with the problem becoming even more acute in light of stricter future proposed standards of ozone.

Ozone photochemical production in urban Shanghai, China: Analysis based on ground level observations

NASA Astrophysics Data System (ADS)

Ran, Liang; Zhao, Chunsheng; Geng, Fuhai; Tie, Xuexi; Tang, Xu; Peng, Li; Zhou, Guangqiang; Yu, Qiong; Xu, Jianmin; Guenther, Alex

2009-08-01

Ozone and its precursors were measured from 15 June 2006 to 14 June 2007 at an urban site in Shanghai and used to characterize photochemical oxidant production in this region. During the observation period, ozone displays a seasonal variation with a maximum in spring. Observed nitrogen oxides (NOx) and carbon monoxide (CO) reached a maximum in winter and a minimum in summer. NOx and CO has a similar double-peak diurnal cycle, implying that they are largely of motor vehicle origin. Total nonmethane organic compounds (NMOC) concentrations averaged over the morning, and the 24-hour periods have a large day-to-day variation with no apparent seasonal cycle. Aromatics play a dominant role in contributing to total NMOC reactivity and ozone-forming potential. Anthropogenic NMOC of diverse sources are major components of total NMOC and consist mainly of moderate and low reactivity species. In contrast, relatively low levels of biogenic NMOC concentrations were observed in urban Shanghai. The early morning NMOC/NOx ratios are typically below 8:1 with an average of around 4:1, indicating that the sampling location is situated in a NMOC-limited regime. Model simulations confirm that potential photochemical ozone production in Shanghai is NMOC-sensitive. It is presently difficult to predict the impact of future human activities, such as the increase of automobiles and vegetation-covered landscapes and the reduction of aerosol on ozone pollution in the fast developing megacities of China, and additional studies are needed to better understand the highly nonlinear ozone problem.

N-nitrosodimethylamine (NDMA) formation during ozonation of wastewater and water treatment polymers.

PubMed

Sgroi, Massimiliano; Roccaro, Paolo; Oelker, Gregg; Snyder, Shane A

2016-02-01

N-Nitrosodimethylamine (NDMA) formation by ozonation was investigated in the effluents of four different wastewater treatment plants destined for alternative reuse. Very high levels of NDMA formation were observed in wastewaters from treatment plants non operating with biological nitrogen removal. Selected experiments showed that hydroxyl radical did not have a significant role in NDMA formation during ozonation of wastewater. Furthermore, ozonation of three different polymers used for water treatment, including polyDADMAC, anionic polyacrylamide, and cationic polyacrylamide, spiked in wastewater did not increase the NDMA formation. Effluent organic matter (EfOM) likely reduced the availability of ozone in water able to react with polymers and quenched the produced ·OH radicals which limited polymer degradation and subsequent NDMA production. Excellent correlations were observed between NDMA formation, UV absorbance at 254 nm, and total fluorescence reduction. These data provide evidence that UV and fluorescence surrogates could be used for monitoring and/or controlling NDMA formation during ozonation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Urban stress-induced biogenic VOC emissions impact secondary aerosol formation in Beijing

NASA Astrophysics Data System (ADS)

Ghirardo, A.; Xie, J.; Zheng, X.; Wang, Y.; Grote, R.; Block, K.; Wildt, J.; Mentel, T.; Kiendler-Scharr, A.; Hallquist, M.; Butterbach-Bahl, K.; Schnitzler, J.-P.

2015-08-01

Trees can significantly impact the urban air chemistry by the uptake and emission of reactive biogenic volatile organic compounds (BVOCs), which are involved in ozone and particle formation. Here we present the emission potentials of "constitutive" (cBVOCs) and "stress-induced" BVOCs (sBVOCs) from the dominant broadleaf woody plant species in the megacity of Beijing. Based on an inventory of BVOC emissions and the tree census, we assessed the potential impact of BVOCs on secondary particulate matter formation in 2005 and 2010, i.e., before and after realizing the large tree-planting program for the 2008 Olympic Games. We found that sBVOCs, such as fatty acid derivatives, benzenoids and sesquiterpenes, constituted a significant fraction (∼ 15 %) of the total annual BVOC emissions, and we estimated that the overall annual BVOC budget may have doubled from ∼ 3.6 × 109 g C year-1 in 2005 to ∼ 7.1 × 109 g C year-1 in 2010 due to the increase in urban greens, while at the same time, the emission of anthropogenic VOCs (AVOCs) could be lowered by 24 %. Based on our BVOC emission assessment, we estimated the biological impact on SOA mass formation in Beijing. Compared to AVOCs, the contribution of biogenic precursors (2-5 %) for secondary particulate matter in Beijing was low. However, sBVOCs can significantly contribute (∼ 40 %) to the formation of total secondary organic aerosol (SOA) from biogenic sources; apparently, their annual emission increased from 1.05 μg m-3 in 2005 to 2.05 μg m-3 in 2010. This study demonstrates that biogenic and, in particular, sBVOC emissions contribute to SOA formation in megacities. However, the main problems regarding air quality in Beijing still originate from anthropogenic activities. Nevertheless, the present survey suggests that in urban plantation programs, the selection of plant species with low cBVOC and sBVOC emission potentials have some possible beneficial effects on urban air quality.

Source Signature of Volatile Organic Compounds (VOCs) associated with oil and natural gas operations in Utah and Colorado

NASA Astrophysics Data System (ADS)

Gilman, J.; Lerner, B. M.; Warneke, C.; Holloway, J. S.; Peischl, J.; Ryerson, T. B.; Young, C. J.; Edwards, P.; Brown, S. S.; Wolfe, D. E.; Williams, E. J.; De Gouw, J. A.

2012-12-01

The U.S. Energy Information Administration has reported a sharp increase in domestic oil and natural gas production from "unconventional" reserves (e.g., shale and tight sands) between 2005 and 2012. The recent growth in drilling and fossil fuel production has led to environmental concerns regarding local air quality. Severe wintertime ozone events (greater than 100 ppb ozone) have been observed in Utah's Uintah Basin and Wyoming's Upper Green River Basin, both of which contain large natural gas fields. Raw natural gas is a mixture of approximately 60-95 mole percent methane while the remaining fraction is composed of volatile organic compounds (VOCs) and other non-hydrocarbon gases. We measured an extensive set of VOCs and other trace gases near two highly active areas of oil and natural gas production in Utah's Uintah Basin and Colorado's Denver-Julesburg Basin in order to characterize primary emissions of VOCs associated with these industrial operations and identify the key VOCs that are precursors for potential ozone formation. UBWOS (Uintah Basin Winter Ozone Study) was conducted in Uintah County located in northeastern Utah in January-February 2012. Two Colorado studies were conducted at NOAA's Boulder Atmospheric Observatory in Weld County in northeastern Colorado in February-March 2011 and July-August 2012 as part of the NACHTT (Nitrogen, Aerosol Composition, and Halogens on a Tall Tower) and SONNE (Summer Ozone Near Natural gas Emissions) field experiments, respectively. The C2-C6 hydrocarbons were greatly enhanced for all of these studies. For example, the average propane mixing ratio observed during the Utah study was 58 ppb (median = 35 ppb, minimum = 0.8, maximum = 520 ppb propane) compared to urban averages which range between 0.3 and 6.0 ppb propane. We compare the ambient air composition from these studies to urban measurements in order to show that the VOC source signature from oil and natural gas operations is distinct and can be clearly distinguished from typical urban emissions associated with on-road combustion sources. We show that each geologic basin has a unique VOC source signature. We will examine the effects of photochemical processing of the primary VOC emissions by comparing the composition and OH reactivity for the wintertime studies to the summertime when there is active photochemistry occurring.

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.

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.

An urban-forest control measure for ozone in the Sacramento, CA federal non-attainment area (SFNA) Sustainable Cities and Society

Treesearch

Haider Taha; James Wilkinson; Robert Bornstein; Qingfu Xiao; E. Gregory McPherson; Jim Simpson; Charles Anderson; Steven Lau; Janice Lam; Cindy Blain

2015-01-01

Urban forest strategies of gradually replacing high emitters of biogenic volatile organic compounds (BVOC) with low-emitting species are being considered as voluntary or emerging control measures for maintenance of the 8-h ozone standard in the Sacramento Federal Non-Attainment Area (SFNA). We describe a regulatory modeling study demonstrating the air-quality impacts...

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.

BROMIDE'S EFFECT ON DBP FORMATION, SPECIATION, AND CONTROL: PART 1, OZONATION

EPA Science Inventory

The effect of variable ozone dosage and bromide concentration on the formation of organic disinfection byproducts (DBPs) and bromate were evaluated. Low ozone dosages resulted in oxidation of organic precursors, yielding decreases in the formation potential for total trihalometha...

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.

CONCENTRATIONS AND PATTERNS OF PHOTOCHEMICAL OXIDANTS IN THE U.S.

EPA Science Inventory

The report describes ozone and PAN levels at urban sites in the U.S., and of ozone at selected nonurban sites. Sample diurnal curves for ozone at suburban and nonurban sites are presented. Highest concentrations of both oxidants occur in California, where the second-highest 1-hr ...

Volatile aromatic hydrocarbons and dicarboxylic acid concentrations in air at an urban site in the Southwestern US

NASA Astrophysics Data System (ADS)

Tran, Ngoc K.; Steinberg, Spencer M.; Johnson, Brian J.

Concentrations of benzene, toluene, ethylbenzene, o-xylene, and m- and p-xylene were measured at an urban sampling site in Las Vegas, NV by sorbent sampling followed by thermal desorption and determination by GC-PID. Simultaneously, measurements of oxalic, malonic, succinic, and adipic acids were made at the same site by collection on quartz filters, extraction, esterification, and determination by GC-FID. For the period from April 7, 1997 to June 11, 1997, 201 sets of hydrocarbon measurements and 99 sets of acid measurements were made. Additional measurements of dicarboxylic acids were made on samples that represented potential direct sources, e.g. green plants and road dust. Correlations between the hydrocarbon and CO concentrations (measured by the Clark County Health District at a nearby site) were highly significant and a strong negative correlation of hydrocarbon concentration with ozone concentration (also from the county site) was observed under quiescent atmospheric conditions. In general, dicarboxylic acid concentrations were well correlated with one another (with the exception of adipic acid) but not well correlated with hydrocarbon, CO, and ozone concentrations. Multiple sources and complex formation processes are indicated for the dicarboxylic acids.

Bromate formation in a hybrid ozonation-ceramic membrane filtration system.

PubMed

Moslemi, Mohammadreza; Davies, Simon H; Masten, Susan J

2011-11-01

The effect of pH, ozone mass injection rate, initial bromide concentration, and membrane molecular weight cut off (MWCO) on bromate formation in a hybrid membrane filtration-ozonation reactor was studied. Decreasing the pH, significantly reduced bromate formation. Bromate formation increased with increasing gaseous ozone mass injection rate, due to increase in dissolved ozone concentrations. Greater initial bromide concentrations resulted in higher bromate concentrations. An increase in the bromate concentration was observed by reducing MWCO, which resulted in a concomitant increase in the retention time in the system. A model to estimate the rate of bromate formation was developed. Good correlation between the model simulation and the experimental data was achieved. Copyright © 2011 Elsevier Ltd. All rights reserved.

Evaluation of concentrations of volatile organic compounds (VOCs) and particulate matter (PM) in an urban area downwind of major petrochemical complexes, in Harris County, Texas

NASA Astrophysics Data System (ADS)

Wilkerson, Daryl F.

Highly Reactive Volatile Organic Compounds (HRVOCs), in particular, the toxic ozone precursors, ethylene, propylene, butenes (1-butene, cis-2-butene, trans-2-butene) and 1, 3 butadiene found in the Houston area are the most critical in the formation of ozone. Exposure to such chemical can cause adverse health effect on the local population of the area, ranging from respiratory distress, asthma, COPD to Cancer. Urban ambient air samples were collected and analyzed from eight monitoring stations (Sites), encompassing the Houston Ship Channel (HSC), in Harris County, Texas. The data was interpreted and analyzed for changes in the concentration of air pollutants, data was collected daily (24 hours) over a time period from September 2013 to August 2014. One 40-minute sample was collected each hour and analyzed by automated gas chromatograph (Auto-GCs) on-site. A total of 70 compounds are measured hourly at each site, in this research the following chemicals were analysis for their average, seasonal and monthly concentrations: ethane, ethylene, propane, propylene, isobutane, n-butane, 1-butene, c-2-butene, t-2-butene and 1,3-butadiene. In this study, seasonal conditions in the area produced ranges from low to high concentrations of these compounds at certain locations. Two Stations had extremely high yearly average concentrations of butane and its isomers (c-2-butene, t-2-butene) and three stations, 1-butene and isobutene concentrations exceeded normal safety limits along with 1,3-butadiene. One station, in particular, close to the HSC had the highest yearly average propylene concentration. Local meteorology also promotes risk issues to the local health of persons within the area/community of interest. This research concluded that the analyzed results of ambient air samples in the urban areas surrounding the Houston Ship Channel (HSC) in Harris County, Texas posed a dual threat. The production of ozone in the daylight hours and depletion of ozone at night, as well as the continuous presence of these precursors in the atmosphere, are both harmful to mankind and toxic to the environment.

Wildfire Emissions and Their Interaction with Urban and Rural Pollution: Data and Simulations

NASA Technical Reports Server (NTRS)

Singh, H. B.

2014-01-01

In recent years NASA has conducted a series of airborne campaigns (e. g. SEAC4RS*, ARCTAS, INTEX-A/B) over North America using an instrumented DC-8 aircraft equipped to measure a very large number of gaseous and aerosol constituents including several unique tracers. In these campaigns wild fires were extensively sampled near source as well as downwind after aging. The data provided detailed information on the composition and chemistry of fire emissions under a variety of atmospheric conditions as well as their interactions with rural and urban air pollution. Major fires studied including the California Rim fire in 2013 (SEAC4RS), the 2008 California wildfires (ARCTAS), and the Alaskan fires downwind over eastern US (INTEX-A). Although some fire plumes contained virtually no O3 enhancement, others showed significant ozone formation. Over Los Angeles, the highest O3 mixing ratios were observed in fire influenced urban air masses. Attempts to simulate these interactions using state of the art models were only minimally successful and indicated several shortcomings in simulating fire emission influences on urban smog formation. A variety of secondary oxidation products (e. g. O3, PAN, HCHO) were substantially underestimated. We will discuss the data collected in fire influenced air masses and their potential air quality implications.

Modeling C1-C4 Alkyl Nitrate Photochemistry and Their Impacts on O3 Production in Urban and Suburban Environments of Hong Kong

NASA Astrophysics Data System (ADS)

Lyu, X. P.; Guo, H.; Wang, N.; Simpson, I. J.; Cheng, H. R.; Zeng, L. W.; Saunders, S. M.; Lam, S. H. M.; Meinardi, S.; Blake, D. R.

2017-10-01

As intermediate products of photochemical reactions, alkyl nitrates (RONO2) regulate ozone (O3) formation. In this study, a photochemical box model incorporating master chemical mechanism well reproduced the observed RONO2 at an urban and a mountainous site, with index of agreement in the range of 0.66-0.73. The value 0.0003 was identified to be the most appropriate branching ratio for C1 RONO2, with the error less than 50%. Although levels of the parent hydrocarbons and nitric oxide (NO) were significantly higher at the urban site than the mountainous site, the production of C2-C3 RONO2 was comparable to or even lower than at the mountainous site, due to the lower concentrations of oxidative radicals in the urban environment. Based on the profiles of air pollutants at the mountainous site, the formation of C2-C4 RONO2 was limited by NOx (volatile organic compounds (VOCs)) when total volatile organic compounds (TVOCs)/NOx was higher (lower) than 10.0 ± 0.4 parts per billion by volume (ppbv)/ppbv. This dividing ratio decreased (p < 0.05) to 8.7 ± 0.4 ppbv/ppbv at the urban site, mainly due to the different air pollutant profiles at the two sites. For the formation of C1 RONO2, the NOx-limited regime extended the ratio of TVOCs/NOx to as low as 2.4 ± 0.2 and 3.1 ± 0.1 ppbv/ppbv at the mountainous and urban site, respectively. RONO2 formation led to a decrease of simulated O3, with reduction efficiencies (O3 reduction/RONO2 production) of 4-5 parts per trillion by volume (pptv)/pptv at the mountainous site and 3-4 pptv/pptv at the urban site. On the other hand, the variations of simulated O3 induced by RONO2 degradation depended upon the regimes controlling O3 formation and the relative abundances of TVOCs and NOx.

Ozone Climate Penalty and Mortality in a Changing World

NASA Astrophysics Data System (ADS)

Hakami, A.; Zhao, S.; Pappin, A.; Mesbah, M.

2013-12-01

The expected increase in ozone concentrations with temperature is referred to as the climate penalty factor (CPF). Observed ozone trends have resulted in estimations of regional CPFs in the range of 1-3 ppb/K in the Eastern US, and larger values around the globe. We use the adjoint of a regional model (CMAQ) for attributing changes in ozone mortality and attainment metrics to increased temperature levels at each location in North America during the summer of 2007. Unlike previous forward sensitivity analysis studies, we estimate how changes in temperatures at various locations influence such policy-relevant metrics. Our analysis accounts for separate temperature impact pathways through gas-phase chemistry, moisture abundance, and biogenic emissions. We find that water vapor impact, while mostly negative, is positive and large for temperature changes in urban areas. We also find that increased biogenic emissions plays an important role in the overall temperature influence. Our simulations show a wide range of spatial variability in CPFs between -0.4 and 6.2 ppb/K with largest values in urban areas. We also estimate mortality-based CPFs of up to 4 deaths/K for each grid cell, again with large localization in urban areas. This amounts to an estimated 370 deaths/K for the 3-month period of the simulation. We find that this number is almost equivalent to 5% reduction in anthropogenic NOx emissions for each degree increase in temperature. We show how the CPF will change as the result progressive NOx emission controls from various anthropogenic sectors and sources at different locations. Our findings suggest that urban NOx control can be regarded as an adaptation strategy with regards to ozone air quality. Also, the strong temperature dependence in urban environments suggests that the health and attainment burden of urban heat island may be more substantial than previously thought. Spatial distribution of average adjoint-based CPFs Adjoint-based CPF and Mortality CPF (domainwide)

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

Modeling of Particulate Emissions

DTIC Science & Technology

2011-12-01

Concern Local Air Quality - A Continuing Concern Ground Level Troposphere Ozone Layer Depletion • H2O Ozone Depletion (ice formation) 5 Modeling... Ozone & Smog Formation Health Effects Local Air Quality 33,000-58,000 ft• NOx •Traffic Growth • CO2* • NOx O3* • NOx Reduces CH4 • H2O Vapor...Particulates • SOx Cloud Formation Global Warming * - Greenhouse Gases Ozone Layer Depletion - Not an Immediate Concern Global Warming - An Emerging

Identification of differentially expressed genes in Fiskeby III under ozone stress conditions

USDA-ARS?s Scientific Manuscript database

As the global climate changes, plants will be challenged by environmental stresses that are more extreme and more frequent leading to increased yield loss. Specifically, ozone stress is an increasing problem in both urban and rural areas. Soybeans are one of the plant species that are quite ozone se...

Some ozone advanced oxidation processes to improve the biological removal of selected pharmaceutical contaminants from urban wastewater.

PubMed

Espejo, Azahara; Aguinaco, Almudena; Amat, Ana M; Beltrán, Fernando J

2014-01-01

Removal of nine pharmaceutical compounds--acetaminophen (AAF), antipyrine (ANT), caffeine (CAF), carbamazepine (CRB), diclofenac (DCF), hydrochlorothiazide (HCT), ketorolac (KET), metoprolol (MET) and sulfamethoxazole (SMX)-spiked in a primary sedimentation effluent of a municipal wastewater has been studied with sequential aerobic biological and ozone advanced oxidation systems. Combinations of ozone, UVA black light and Fe(III) or Fe3O4 constituted the chemical systems. During the biological treatment (hydraulic residence time, HRT = 24 h), only AAF and CAF were completely eliminated, MET, SMX and HCT reached partial removal rates and the rest of compounds were completely refractory. With any ozone advanced oxidation process applied, the remaining pharmaceuticals disappear in less than 10 min. Fe3O4 or Fe(III) photocatalytic ozonation leads to 35% mineralization compared to 13% reached during ozonation alone after about 30-min reaction. Also, biodegradability of the treated wastewater increased 50% in the biological process plus another 150% after the ozonation processes. Both untreated and treated wastewater was non-toxic for Daphnia magna (D. magna) except when Fe(III) was used in photocatalytic ozonation. In this case, toxicity was likely due to the ferryoxalate formed in the process. Kinetic information on ozone processes reveals that pharmaceuticals at concentrations they have in urban wastewater are mainly removed through free radical oxidation.

Modelling the urban air quality in Hamburg with the new city-scale chemistry transport model CityChem

NASA Astrophysics Data System (ADS)

Karl, Matthias; Ramacher, Martin; Aulinger, Armin; Matthias, Volker; Quante, Markus

2017-04-01

Air quality modelling plays an important role by providing guidelines for efficient air pollution abatement measures. Currently, most urban dispersion models treat air pollutants as passive tracer substances or use highly simplified chemistry when simulating air pollutant concentrations on the city-scale. The newly developed urban chemistry-transport model CityChem has the capability of modelling the photochemical transformation of multiple pollutants along with atmospheric diffusion to produce pollutant concentration fields for the entire city on a horizontal resolution of 100 m or even finer and a vertical resolution of 24 layers up to 4000 m height. CityChem is based on the Eulerian urban dispersion model EPISODE of the Norwegian Institute for Air Research (NILU). CityChem treats the complex photochemistry in cities using detailed EMEP chemistry on an Eulerian 3-D grid, while using simple photo-stationary equilibrium on a much higher resolution grid (receptor grid), i.e. close to industrial point sources and traffic sources. The CityChem model takes into account that long-range transport contributes to urban pollutant concentrations. This is done by using 3-D boundary concentrations for the city domain derived from chemistry-transport simulations with the regional air quality model CMAQ. For the study of the air quality in Hamburg, CityChem was set-up with a main grid of 30×30 grid cells of 1×1 km2 each and a receptor grid of 300×300 grid cells of 100×100 m2. The CityChem model was driven with meteorological data generated by the prognostic meteorology component of the Australian chemistry-transport model TAPM. Bottom-up inventories of emissions from traffic, industry, households were based on data of the municipality of Hamburg. Shipping emissions for the port of Hamburg were taken from the Clean North Sea Shipping project. Episodes with elevated ozone (O3) were of specific interest for this study, as these are associated with exceedances of the World Health Organization (WHO) guideline concentration limits for O3 and of the regulatory limits for NO2. Model tests were performed with CityChem to study the ozone formation rate with simultaneous variation of emissions of nitrogen oxides (NOx) and volatile organic compounds (VOC). Emissions of VOC in urban areas are not well quantified as they may originate from various sources, including solvent usage, industry, combustion plants and vehicular traffic. The employed chemical mechanism contains large uncertainties with respect to ozone formation. Observed high-O3 episodes were analyzed by comparing modelled pollutant concentrations with concentration data from the Hamburg air quality surveillance network (http://luft.hamburg.de/). The analysis inspected possible reasons for too low modelled O3 in summer such as missing emissions of VOC from natural sources like green parks and the vertical exchange of O3 towards the surface.

Tropospheric ozone variability over Singapore from August 1996 to December 1999

NASA Astrophysics Data System (ADS)

Yonemura, S.; Tsuruta, H.; Maeda, T.; Kawashima, S.; Sudo, S.; Hayashi, M.

Vertical ozone profiles over Singapore (lat 1°20'N, long 103°53'E) have been monitored by ozonesondes twice a month since August 1996. We report the vertical ozone profiles over Singapore from August 1996 to the end of 1999. During this time, large ozone enhancements occurred during three periods: March-June 1997, September-November 1997, and February-May 1998. These ozone enhancements were larger over Singapore than over Malaysia. Backward trajectory analyses revealed that the enhancements during September-November 1997, and February-May 1998 were associated with biomass burning in Indonesia and Southeast Asia. Outside the three periods, ozone concentrations over Singapore differed from those over Malaysia by not more than 2.5% at altitudes of between 2.6 and 7.6 km and by not more than 12% at altitudes of between 1 and 13.5 km. The minimum ozone concentrations in the middle and the upper troposphere were about 20 ppbv and were observed when the wind was easterly from the Pacific Ocean. Ozone concentrations at the bottom of the troposphere were near zero when the wind was southerly to westerly (from the larger, more urbanized and industrialized part of Singapore and the Strait of Malacca), implying that ozone-destroying reactions were occurring with high concentrations of urban pollutants. We conclude that the ozone enhancements observed in the free troposphere resulted from the effects of extensive biomass burning combined with the modified circulation (suppressed convection of maritime air masses) that occurs during El Niño events.

N-nitrosodimethylamine (NDMA) formation from the ozonation of model compounds.

PubMed

Marti, Erica J; Pisarenko, Aleksey N; Peller, Julie R; Dickenson, Eric R V

2015-04-01

Nitrosamines are a class of toxic disinfection byproducts commonly associated with chloramination, of which several were included on the most recent U.S. EPA Contaminant Candidate List. Nitrosamine formation may be a significant barrier to ozonation in water reuse applications, particularly for direct or indirect potable reuse, since recent studies show direct formation during ozonation of natural water and treated wastewaters. Only a few studies have identified precursors which react with ozone to form N-nitrosodimethylamine (NDMA). In this study, several precursor compound solutions, prepared in ultrapure water and treated wastewater, were subjected to a 10 M excess of ozone. In parallel experiments, the precursor solutions in ultrapure water were exposed to gamma radiation to determine NDMA formation as a byproduct of reactions of precursor compounds with hydroxyl radicals. The results show six new NDMA precursor compounds that have not been previously reported in the literature, including compounds with hydrazone and carbamate moieties. Molar yields in deionized water were 61-78% for 3 precursors, 12-23% for 5 precursors and <4% for 2 precursors. Bromide concentration was important for three compounds (1,1-dimethylhydrazine, acetone dimethylhydrazone and dimethylsulfamide), but did not enhance NDMA formation for the other precursors. NDMA formation due to chloramination was minimal compared to formation due to ozonation, suggesting distinct groups of precursor compounds for these two oxidants. Hydroxyl radical reactions with the precursors will produce NDMA, but formation is much greater in the presence of molecular ozone. Also, hydroxyl radical scavenging during ozonation leads to increased NDMA formation. Molar conversion yields were higher for several precursors in wastewater as compared to deionized water, which could be due to catalyzed reactions with constituents found in wastewater or hydroxyl radical scavenging. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ozone formation behind pulsed-laser-generated blast waves in oxygen

NASA Astrophysics Data System (ADS)

Stricker, J.; Parker, J. G.

1984-12-01

The formation of ozone behind blast waves in oxygen generated by a pulsed laser has been investigated both experimentally and theoretically, over cell pressure range of 0.68-27 atm. Ozone buildup formed by successive pulses was monitored by recording UV absorption at 2540 Å. It was found that, as the number of pulses increase, the rate of ozone formation decreased until finally an equilibrium concentration was reached. This equilibrium magnitude was determined by the condition that the number of ozone molecules produced by the wave equals the number decomposed by the same wave. The decomposition and formation of O3 during a single pulse were monitored by time-resolved UV absorption measurements. In order to provide a fundamental basis for interpretation of the mechanism of ozone formation, a mathematical model was developed. Although qualitatively measurements and theory agree, the data, mainly on the number of O3 molecules produced per pulse, is in significant disagreement. Several possible explanations of this discrepancy are given.

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

EPA Science Inventory

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

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...

Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components.

PubMed

Onyango, Arnold N

2016-01-01

Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity.

Endogenous Generation of Singlet Oxygen and Ozone in Human and Animal Tissues: Mechanisms, Biological Significance, and Influence of Dietary Components

PubMed Central

2016-01-01

Recent studies have shown that exposing antibodies or amino acids to singlet oxygen results in the formation of ozone (or an ozone-like oxidant) and hydrogen peroxide and that human neutrophils produce both singlet oxygen and ozone during bacterial killing. There is also mounting evidence that endogenous singlet oxygen production may be a common occurrence in cells through various mechanisms. Thus, the ozone-producing combination of singlet oxygen and amino acids might be a common cellular occurrence. This paper reviews the potential pathways of formation of singlet oxygen and ozone in vivo and also proposes some new pathways for singlet oxygen formation. Physiological consequences of the endogenous formation of these oxidants in human tissues are discussed, as well as examples of how dietary factors may promote or inhibit their generation and activity. PMID:27042259

Aromatic VOCs global influence in the ozone production

NASA Astrophysics Data System (ADS)

Cabrera-Perez, David; Pozzer, Andrea

2016-04-01

Aromatic hydrocarbons are a subgroup of Volatile Organic Compounds (VOCs) of special interest in the atmosphere of urban and semi-urban areas. Aromatics form a high fraction of VOCs, are highly reactive and upon oxidation they are an important source of ozone. These group of VOCs are released to the atmosphere by processes related to biomass burning and fossil fuel consumption, while they are removed from the atmosphere primarily by OH reaction and by dry deposition. In addition, a branch of aromatics (ortho-nitrophenols) produce HONO upon photolysis, which is responsible of certain amount of the OH recycling. Despite their importance in the atmosphere in anthropogenic polluted areas, the influence of aromatics in the ozone production remains largely unknown. This is of particular relevance, being ozone a pollutant with severe side effects on air quality, health and climate. In this work the atmospheric impacts at global scale of the most emitted aromatic VOCs in the gas phase (benzene, toluene, xylenes, ethylbenzene, styrene, phenol, benzaldehyde and trimethylbenzenes) are analysed and assessed. Specifically, the impact on ozone due to aromatic oxidation is estimated, as this is of great interest in large urban areas and can be helpful for developing air pollution control strategies. Further targets are the quantification of the NOx loss and the OH recycling due to aromatic oxidation. In order to investigate these processes, two simulations were performed with the numerical chemistry and climate simulation ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The simulations compare two cases, one with ozone concentrations when aromatics are present or the second one when they are missing. Finally, model simulated ozone is compared against a global set of observations in order to better constrain the model accuracy.

Changes in air quality and tropospheric composition due to depletion of stratospheric ozone and interactions with changing climate: implications for human and environmental health.

PubMed

Madronich, S; Shao, M; Wilson, S R; Solomon, K R; Longstreth, J D; Tang, X Y

2015-01-01

UV radiation is an essential driver for the formation of photochemical smog, which includes ground-level ozone and particulate matter (PM). Recent analyses support earlier work showing that poor outdoor air quality is a major environmental hazard as well as quantifying health effects on regional and global scales more accurately. Greater exposure to these pollutants has been linked to increased risks of cardiovascular and respiratory diseases in humans and is associated globally with several million premature deaths per year. Ozone also has adverse effects on yields of crops, leading to loss of billions of US dollars each year. These detrimental effects also may alter biological diversity and affect the function of natural ecosystems. Future air quality will depend mostly on changes in emission of pollutants and their precursors, but changes in UV radiation and climate will contribute as well. Significant reductions in emissions, mainly from the energy and transportation sectors, have already led to improved air quality in many locations. Air quality will continue to improve in those cities/states that can afford controls, and worsen where the regulatory infrastructure is not available. Future changes in UV radiation and climate will alter the rates of formation of ground-level ozone and photochemically-generated particulate matter and must be considered in predictions of air quality. The decrease in UV radiation associated with recovery of stratospheric ozone will, according to recent global atmospheric model simulations, lead to increases in ground-level ozone at most locations. If correct, this will add significantly to future ground-level ozone trends. However, the spatial resolution of these global models is insufficient to inform policy at this time, especially for urban areas. UV radiation affects the atmospheric concentration of hydroxyl radicals, ˙OH, which are responsible for the self-cleaning of the atmosphere. Recent measurements confirm that, on a local scale, ˙OH radicals respond rapidly to changes in UV radiation. However, on large (global) scales, models differ in their predictions by nearly a factor of two, with consequent uncertainties for estimating the atmospheric lifetime and concentrations of key greenhouse gases and air pollutants. Projections of future climate need to consider these uncertainties. No new negative environmental effects of substitutes for ozone depleting substances or their breakdown-products have been identified. However, some substitutes for the ozone depleting substances will continue to contribute to global climate change if concentrations rise above current levels.

Beyond SHARP-- Primary Formaldehyde from Oil and Gas Exploration and Production in the Gulf of Mexico Region

NASA Astrophysics Data System (ADS)

Olaguer, E. P.

2010-12-01

Formaldehyde has been named by the EPA as a hazardous air pollutant that may be carcinogenic and also cause irritation to the eyes, nose, throat and lung. Moreover, it is a powerful radical and ozone precursor. The 2009 Study of Houston Atmospheric Radical Precursors (SHARP) was conceived by the Houston Advanced Research Center (HARC) on behalf of the Texas Environmental Research Consortium (TERC) to examine the relative importance of primary and secondary formaldehyde (HCHO) and nitrous acid (HONO) in ozone formation. SHARP confirmed that primary combustion sources of HCHO, such as flares end engines, may be underestimated (by an order of magnitude or more) in official emission inventories used for the purpose of air quality modeling in highly industrialized areas such as Houston. This presentation provides recently generated modeling and observational evidence that the same may be true in both rural and urban areas with oil and gas exploration and production (E&P) activities, such as the Upper Green River Basin of Wyoming and the Barnett Shale of Texas. Oil and gas E&P is increasing in the Gulf of Mexico region, particularly in the Barnett, Haynesville, Eagle Ford, Cana-Woodford, and Fayetteville shale basins. In the Barnett Shale, E&P activities are moving into urban neighborhoods, and may affect the ability to bring the Dallas-Ft. Worth region into attainment of the federal ozone standard. Data concerning formaldehyde emissions from drill rig and pipeline compressor engines, flares, and glycol or amine reboilers, should be obtained in order to more accurately model air quality in the Gulf of Mexico region.

Urban ecosystem services: tree diversity and stability of tropospheric ozone removal.

PubMed

Manes, Fausto; Incerti, Guido; Salvatori, Elisabetta; Vitale, Marcello; Ricotta, Carlo; Costanza, Robert

2012-01-01

Urban forests provide important ecosystem services, such as urban air quality improvement by removing pollutants. While robust evidence exists that plant physiology, abundance, and distribution within cities are basic parameters affecting the magnitude and efficiency of air pollution removal, little is known about effects of plant diversity on the stability of this ecosystem service. Here, by means of a spatial analysis integrating system dynamic modeling and geostatistics, we assessed the effects of tree diversity on the removal of tropospheric ozone (O3) in Rome, Italy, in two years (2003 and 2004) that were very different for climatic conditions and ozone levels. Different tree functional groups showed complementary uptake patterns, related to tree physiology and phenology, maintaining a stable community function across different climatic conditions. Our results, although depending on the city-specific conditions of the studied area, suggest a higher function stability at increasing diversity levels in urban ecosystems. In Rome, such ecosystem services, based on published unitary costs of externalities and of mortality associated with O3, can be prudently valued to roughly US$2 and $3 million/year, respectively.

Impacts of heterogeneous reactions to atmospheric peroxides: Observations and budget analysis study

NASA Astrophysics Data System (ADS)

Qin, Mengru; Chen, Zhongming; Shen, Hengqing; Li, Huan; Wu, Huihui; Wang, Yin

2018-06-01

Atmospheric peroxides play important roles in atmospheric chemistry, acting as reactive oxidants and reservoirs of HOX and ROX radicals. Field measurements of atmospheric peroxides were conducted over urban Beijing from 2015 to 2016, including dust storm days, haze days and different seasons. We employed a box model based on RACM2 mechanism to conduct concentration simulation and budget analysis of hydrogen peroxide (H2O2) and peroxyacetic acid (PAA). In this study, heterogeneous reaction is found to be a significant sink for atmospheric H2O2 and PAA in urban Beijing. Here, we recommend a suitable uptake coefficient formula considering the water effect for model research of peroxides. It is found that H2O2 and PAA unexpectedly maintained considerable concentrations on haze days, even higher than that on non-haze days. This phenomenon is mainly ascribed to relatively high levels of volatile organic compounds and ozone on haze days. In addition, high levels of water vapor in pollution episode can promote not only the heterogeneous uptake to aerosol phase but also the production of H2O2. Atmospheric PAA formation is suggested to be sensitive to alkenes and NOX in urban Beijing. In particular, with the help of peroxides, sulfate formation rate from heterogeneous uptake could increase by ∼4 times on haze days, indicating the potential effect of peroxides on enhancement of aerosol oxidative property and secondary sulfate formation.

Top-down NOX emissions over European cities from LOTOS-EUROS simulated and OMI observed tropospheric NO2 columns using the Exponentially Modified Gaussian approach

NASA Astrophysics Data System (ADS)

Verstraeten, Willem W.; Folkert Boersma, K.; Douros, John; Williams, Jason E.; Eskes, Henk H.; Delcloo, Andy

2017-04-01

High nitrogen oxides concentrations at the surface (NOX = NO + NO2) impact humans and ecosystem badly and play a key role in tropospheric chemistry. Surface NOX emissions drive major processes in regional and global chemistry transport models (CTM). NOX contributes to the formation of acid rain, act as aerosol precursors and is an important trace gas for the formation of tropospheric ozone (O3). Via tropospheric O3, NOX indirectly affects the production of the hydroxyl radical which controls the chemical lifetime of key atmospheric pollutants and reactive greenhouse gases. High NOX emissions are mainly observed in polluted regions produced by anthropogenic combustion from industrial, traffic and household activities typically observed in large and densely populated urban areas. Accurate NOX inventories are essential, but state-of the- art emission databases may vary substantially and uncertainties are high since reported emissions factors may differ in order of magnitude and more. To date, the modelled NO2 concentrations and lifetimes have large associated uncertainties due to the highly non-linear small-scale chemistry that occurs in urban areas and uncertainties in the reaction rate data, missing nitrogen (N) species and volatile organic compounds (VOC) emissions, and incomplete knowledge of nitrogen oxides chemistry. Any overestimation in the chemical lifetime may mask missing NOX chemistry in current CTM's. By simultaneously estimating both the NO2 lifetime and concentrations, for instance by using the Exponentially Modified Gaussian (EMG), a better surface NOX emission flux estimate can be obtained. Here we evaluate if the EMG methodology can reproduce the emissions input from the tropospheric NO2 columns simulated by the LOTOS-EUROS (Long Term Ozone Simulation-European Ozone Simulation) CTM model. We apply the EMG methodology on LOTOS-EUROS simulated tropospheric NO2 columns for the period April-September 2013 for 21 selected European urban areas under windy conditions (surface wind speeds > 3 m s-1). We then compare the top-down derived surface NOX emissions with the 2011 MACC-III emission inventory, used in the LOTOS-EUROS model as input to simulate the NO2 columns. We also apply the EMG methodology on OMI (Ozone Monitoring Instrument) tropospheric NO2 column data, providing us with real-time observation-based estimates of midday NO2 lifetime and NOX emissions over 21 European cities in 2013. Results indicate that the top-down derived NOX emissions from LOTOS-EUROS (respectively OMI) are comparable with the MACC-III inventory with a R2 of 0.99 (respectively R2 = 0.79). For St-Petersburg and Moscow the top-down NOX estimates from 2013 OMI data are biased low compared to the MACC-III inventory which uses a 2011 NOX emissions update.

Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation.

PubMed

De Vera, Glen Andrew; Stalter, Daniel; Gernjak, Wolfgang; Weinberg, Howard S; Keller, Jurg; Farré, Maria José

2015-12-15

When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and •OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6-8) and transferred ozone doses (0-1 mg/mg TOC). Although ozonation led to a 24-37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over •OH reactions (e.g., pH 8 and in the presence of H2O2). Compared to ozonation only, addition of H2O2 consistently enhanced formation of all DBP groups (20-61%) except trihalonitromethanes. This proves that •OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor •OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Reduction of N-nitrosodimethylamine formation from ranitidine by ozonation preceding chloramination: influencing factors and mechanisms.

PubMed

Zou, Rusen; Liao, Xiaobin; Zhao, Lei; Yuan, Baoling

2018-05-01

Formation of toxic N-nitrosodimethylamine (NDMA) by chloramination of ranitidine, a drug to block histamine, was still an ongoing issue and posed a risk to human health. In this study, the effect of ozonation prior to chloramination on NDMA formation and the transformation pathway were determined. Influencing factors, including ozone dosages, pH, hydroxyl radical scavenger, bromide, and NOM, were studied. The results demonstrated that small ozone dosage (0.5 mg/L) could effectively control NDMA formation from subsequent chloramination (from 40 to 0.8%). The NDMA molar conversion was not only influenced by pH but also by ozone dosages at various pre-ozonation pH (reached the highest value of 5% at pH 8 with 0.5 mg/L O 3 but decreased with the increasing pH with 1 mg/L O 3 ). The NDMA molar yield by chloramination of ranitidine without pre-ozonation was reduced by the presence of bromide ion due to the decomposition of disinfectant. However, due to the formation of brominated intermediate substances (i.e., dimethylamine (DMA), dimethyl-aminomethyl furfuryl alcohol (DFUR)) with higher NDMA molar yield than their parent substances, more NDMA was formed than that without bromide ion upon ozonation. Natural organic matter (NOM) and hydroxyl radical scavenger (tert-butyl alcohol, tBA) enhanced NDMA generation because of the competition of ozone and more ranitidine left. The NDMA reduction mechanism by pre-ozonation during chloramination of ranitidine may be due to the production of oxidation products with less NDMA yield (such as DMA) than parent compound. Based on the result of Q-TOF and GC-MS/MS analysis, three possible transformation pathways were proposed. Different influences of oxidation conditions and water quality parameters suggest that strategies to reduce NDMA formation should vary with drinking water sources and choose optimal ozone dosage.

Exhaust emissions of volatile organic compounds of powered two-wheelers: effect of cold start and vehicle speed. Contribution to greenhouse effect and tropospheric ozone formation.

PubMed

Costagliola, M Antonietta; Murena, Fabio; Prati, M Vittoria

2014-01-15

Powered two-wheeler (PTW) vehicles complying with recent European type approval standards (stages Euro 2 and Euro 3) were tested on chassis dynamometer in order to measure exhaust emissions of about 25 volatile organic compounds (VOCs) in the range C1-C7, including carcinogenic compounds as benzene and 1,3-butadiene. The fleet consists of a moped (engine capacity ≤ 50 cm(3)) and three fuel injection motorcycles of different engine capacities (150, 300 and 400 cm(3)). Different driving conditions were tested (US FPT cycle, constant speed). Due to the poor control of the combustion and catalyst efficiency, moped is the highest pollutant emitter. In fact, fuel injection strategy and three way catalyst with lambda sensor are able to reduce VOC motorcycles' emission of about one order of magnitude with respect to moped. Cold start effect, that is crucial for the assessment of actual emission of PTWs in urban areas, was significant: 30-51% of extra emission for methane. In the investigated speed range, moped showed a significant maximum of VOC emission factor at minimum speed (10 km/h) and a slightly decreasing trend from 20 to 60 km/h; motorcycles showed on the average a less significant peak at 10 km/h, a minimum at 30-40 km/h and then an increasing trend with a maximum emission factor at 90 km/h. Carcinogenic VOCs show the same pattern of total VOCs. Ozone Formation Potential (OFP) was estimated by using Maximum Incremental Reactivity scale. The greatest contribution to tropospheric ozone formation comes from alkenes group which account for 50-80% to the total OFP. VOC contribution effect on greenhouse effect is negligible with respect to CO2 emitted. © 2013.

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...

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

EPA Science Inventory

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

Regulatory ozone modeling: status, directions, and research needs.

PubMed Central

Georgopoulos, P G

1995-01-01

The Clean Air Act Amendments (CAAA) of 1990 have established selected comprehensive, three-dimensional, Photochemical Air Quality Simulation Models (PAQSMs) as the required regulatory tools for analyzing the urban and regional problem of high ambient ozone levels across the United States. These models are currently applied to study and establish strategies for meeting the National Ambient Air Quality Standard (NAAQS) for ozone in nonattainment areas; State Implementation Plans (SIPs) resulting from these efforts must be submitted to the U.S. Environmental Protection Agency (U.S. EPA) in November 1994. The following presentation provides an overview and discussion of the regulatory ozone modeling process and its implications. First, the PAQSM-based ozone attainment demonstration process is summarized in the framework of the 1994 SIPs. Then, following a brief overview of the representation of physical and chemical processes in PAQSMs, the essential attributes of standard modeling systems currently in regulatory use are presented in a nonmathematical, self-contained format, intended to provide a basic understanding of both model capabilities and limitations. The types of air quality, emission, and meteorological data needed for applying and evaluating PAQSMs are discussed, as well as the sources, availability, and limitations of existing databases. The issue of evaluating a model's performance in order to accept it as a tool for policy making is discussed, and various methodologies for implementing this objective are summarized. Selected interim results from diagnostic analyses, which are performed as a component of the regulatory ozone modeling process for the Philadelphia-New Jersey region, are also presented to provide some specific examples related to the general issues discussed in this work. Finally, research needs related to a) the evaluation and refinement of regulatory ozone modeling, b) the characterization of uncertainty in photochemical modeling, and c) the improvement of the model-based ozone-attainment demonstration process are presented to identify future directions in this area. Images Figure 7. Figure 7. Figure 7. Figure 8. Figure 9. PMID:7614934

The response of ozone to transportation technology and policy options

NASA Astrophysics Data System (ADS)

Holloway, T.

2008-12-01

As the global economy grows, there is a corresponding increase in the number of passenger cars on the road and in the volume of goods shipped. Building on novel methods to estimate these transportation emissions, we evaluate the regional air quality impacts of personal vehicles and heavy-duty diesel vehicles (HDDV) for freight transport. In particular, we quantify the potential of technological and policy-based solutions to reduce mean ozone concentrations and the frequency of high ozone events. Although transportation contributes to a range of air quality challenges, ozone chemistry is particularly sensitive to vehicle emissions, with on-road vehicles accounting for 44 percent of all man-made U.S. NOx emissions, and HDDV accounting for nearly 42 percent of this on-road contribution. Our studies focus on the Upper Midwestern United States, where urban development, agricultural activities, lake effect meteorology, and cross-continental freight transport are all major drivers of ozone chemistry and transport. Results will be presented from a range of recently completed and ongoing studies evaluating the ozone impacts of urban vehicle travel, the response of freight emissions to fuel-conserving speed reduction measures, and the consequences of increased biofuel use.

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.

A WRF-Chem model study of the impact of VOCs emission of a huge petro-chemical industrial zone on the summertime ozone in Beijing, China

NASA Astrophysics Data System (ADS)

Wei, Wei; Lv, Zhao Feng; Li, Yue; Wang, Li Tao; Cheng, Shuiyuan; Liu, Huan

2018-02-01

In China, petro-chemical manufacturing plants generally gather in the particular industrial zone defined as PIZ in some cities, and distinctly influence the air quality of these cities for their massive VOCs emissions. This study aims to quantify the local and regional impacts of PIZ VOCs emission and its relevant reduction policy on the surface ozone based on WRF-Chem model, through the case study of Beijing. Firstly, the model simulation under the actual precursors' emissions over Beijing region for July 2010 is conducted and evaluated, which meteorological and chemical predictions both within the thresholds for satisfactory model performance. Then, according to simulated H2O2/HNO3 ratio, the nature of photochemical ozone formation over Beijing is decided, the VOCs-sensitive regime over the urban areas, NOx-sensitive regime over the northern and western rural areas, and both VOCssbnd and NOx-mixed sensitive regime over the southern and eastern rural areas. Finally, a 30% VOCs reduction scenario (RS) and a 100% VOCs reduction scenario (ZS) for Beijing PIZ are additional simulated by WRF-Chem. The sensitivity simulations imply that the current 30% reduction policy would bring about an O3 increase in the southern and western areas (by +4.7 ppb at PIZ site and +2.1 ppb at LLH station), and an O3 decrease in the urban center (by -1.7 ppb at GY station and -2.5 ppb at DS station) and in the northern and eastern areas (by -1.2 ppb at MYX station), mainly through interfering with the circulation of atmospheric HOx radicals. While the contribution of the total VOCs emission of PIZ to ozone is greatly prominent in the PIZ and its surrounding areas along south-north direction (12.7% at PIZ site on average), but slight in the other areas of Beijing (<3% in other four stations on average).

Inter-comparison of HONO field measurements and its summertime variation in Seoul, Korea

NASA Astrophysics Data System (ADS)

Kim, J.; Lee, G.; Lee, D.; Cho, S.

2017-12-01

HONO is a key source of OH radical responsible for atmospheric oxidative capacity and plays an important role in heterogeneous oxidation of some species. To understand the oxidative mechanisms that lead to urban ozone and aerosol formation we need to know the sources and behavior of this trace gas. Despite its importance, HONO budgets, especially in the urban conditions in Korea are not well understood. In this study, HONO measurement was conducted in Olympic Park located in Seoul, Korea from May 19 to June 15 of 2016 using Quantum Cascade-Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS), High Efficiency Diffusion Scrubber-Ion Chromatography (HEDS-IC) and Monitor for AeRosols & Gases in ambient Air (MARGA). Overall, the measurements obtained with the three instruments agreed within analysis uncertainty. The resulting detection limits of all instruments were close to 0.10 ppbv for HONO. HONO concentrations over the measurement period varied from the detection limit to 3.46 ppbv (QC-TILDAS), 3.03 ppbv (HEDS-IC) and 4.81 ppbv (MARGA), respectively. Using a chemical box model including varying PBL heights and emissions, major paths of HONO production and its contributions to ozone was identified. The model showed significant underestimation compared to observations, which suggests additional unknown HONO production or direct HONO emission.

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.

POGO-FAN: Remarkable Empirical Indicators for the Local Chemical Production of Smog- Ozone and NOx-Sensitivity of Air Parcels

NASA Astrophysics Data System (ADS)

Chatfield, R. B.; Browell, E. V.; Brune, W. H.; Crawford, J. H.; Esswein, R.; Fried, A.; Olson, J. R.; Shetter, R. E.; Singh, H. B.

2006-12-01

We propose and evaluate two related and surprisingly simple empirical estimators for the local chemical production term for photochemical ozone; each uses two moderate-technology chemical measurements and a measurement of ultraviolet light. We nickname the techniques POGO-FAN: Production of Ozone by Gauging Oxidation: Formaldehyde and NO. (1) A non-linear function of a single three-factor index-variable, j (HCHO=>rads) [HCHO] [NO] seems to provide a good estimator of the largest single term in the production of smog ozone, the HOO+NO term, over a very wide range of situations. (2) By considering empirical contour plots summarizing isopleths of HOO+NO using j (HCHO=>rads) [HCHO] and [NO] separately as coordinates, we provide a slightly more complex 2-d indicator of smog ozone production that additionally allows an estimate of the NOx-sensitivity or NOx-saturation (i.e., VOC-sensitivity) of sampled air parcels. ~85 to >90 % of the variance is explained. The correspondence to "EKMA" contour plots, estimating afternoon ozone based on morningtime organics and NOx mixes, is not coincidental. We utilize a broad set of urban plume, regionally polluted and cleaner NASA DC-8 PBL samples from the Intercontinental Transport Experiment-North America (INTEX-NA), in which each of the variables was measured, to help establish our relationship. The estimator is described in terms both both of asymptotic smog photochemistry theory; primarily this suggests appropriate statistical approaches which can capture some of the complex interrelations of lower-tropospheric smog mix through correlation of reactive mixture components. HCHO is not only an important source of HOO radicals, but it more important serves as a "gauge" of all photochemical processing of volatile organic compounds. It probably captures information related to coincident VOC sources of various compounds and parallels in photochemical processing. Constrained modeling of observed atmospheric concentrations suggests that the prime source of ozone from HOO+NO reaction and other peroxy radical ozone formation reactions (ROO+NO), thus all ozone production, are closely related. Additionally, modeling allows us to follow ozone production and NOx-sensitivity throughout the varying photolytic cycle.

Photocatalytic ozonation of urban wastewater and surface water using immobilized TiO2 with LEDs: Micropollutants, antibiotic resistance genes and estrogenic activity.

PubMed

Moreira, Nuno F F; Sousa, José M; Macedo, Gonçalo; Ribeiro, Ana R; Barreiros, Luisa; Pedrosa, Marta; Faria, Joaquim L; Pereira, M Fernando R; Castro-Silva, Sérgio; Segundo, Marcela A; Manaia, Célia M; Nunes, Olga C; Silva, Adrián M T

2016-05-01

Photocatalytic ozonation was employed for the first time in continuous mode with TiO2-coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO2 catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01-0.20 ng L(-1)). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes (intI1, blaTEM, qnrS, sul1). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1, increased to values close to the pre-treatment levels, the ARGs (blaTEM, qnrS and sul1) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Land Use and Land Cover Change, Urban Heat Island Phenomenon, and Health Implications: A Remote Sensing Approach

NASA Technical Reports Server (NTRS)

Lo, C. P.; Quattrochi, Dale A.

2003-01-01

Land use and land cover maps of Atlanta Metropolitan Area in Georgia were produced from Landsat MSS and TM images for 1973,1979,1983,1987,1992, and 1997, spanning a period of 25 years. Dramatic changes in land use and land cover have occurred with loss of forest and cropland to urban use. In particular, low-density urban use, which includes largely residential use, has increased by over 119% between 1973 and 1997. These land use and land cover changes have drastically altered the land surface characteristics. An analysis of Landsat images revealed an increase in surface temperature and a decline in NDVI from 1973 to 1997. These changes have forced the development of a significant urban heat island effect and an increase in ground level ozone production to such an extent, that Atlanta has violated EPA's ozone level standard in recent years. The urban heat island initiated precipitation events that were identified between 1996 and 2000 tended to occur near high-density urban areas but outside the I-285 loop that traverses around the Central Business District, i.e. not in the inner city area, but some in close proximity to the highways. The health implications were investigated by comparing the spatial patterns of volatile organic compounds (VOC) and nitrogen oxides (NOx) emissions, the two ingredients that form ozone by reacting with sunlight, with those of rates of cardiovascular and chronic lower respiratory diseases. A clear core-periphery pattern was revealed for both VOC and NOx emissions, but the spatial pattern was more random in the cases of rates of cardiovascular and chronic lower respiratory diseases. Clearly, factors other than ozone pollution were involved in explaining the rates of these diseases. Further research is therefore needed to understand the health geography and its relationship to land use and land cover change as well as urban heat island effect. This paper illustrates the usefulness of a remote sensing approach for this purpose.

The determination and role of peroxyacetil nitrate in photochemical processes in atmosphere

PubMed Central

2012-01-01

Peroxyacetilnitrates (PAN) is the most characteristic photoxidant of a range of secondary pollutants formed by the photochemical reaction of hydrocarbons with nitrogen oxides in the atmosphere: it is phytotoxic and shows an increasing role in human health effects due to ambient air exposure, especially in presence of high ozone concentrations. Because of the similarity of the conditions required for their photochemical production PAN is observed in conjunction with elevated ozone concentrations. PAN has very low natural background concentrations so it is the very specific indicator of anthropogenic photochemical air pollution. In this paper we report PAN concentrations determined in Rome urban area during winter- and summer-period. PAN measurements were carried out by means of a gas-chromatograph equipped with an Electron Capture Detector (ECD) detector. For identifying the acute episodes of atmospheric photochemical pollutants the relationship between PAN and the variable Ox (=NO2+O3) which describes the oxidation process evolution is investigated. The role of Volatile Organic Compounds and PAN in the ozone formation is investigated as well the issue of taking in account the autovehicular emissions for checking the NOx fraction in fuel. PMID:22594443

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.

Estradiol prevents ozone-induced increases in brain lipid peroxidation and impaired social recognition memory in female rats.

PubMed

Guevara-Guzmán, R; Arriaga, V; Kendrick, K M; Bernal, C; Vega, X; Mercado-Gómez, O F; Rivas-Arancibia, S

2009-03-31

There is increasing concern about the neurodegenerative and behavioral consequences of ozone pollution in industrialized urban centers throughout the world and that women may be more susceptible to brain neurodegenerative disorders. In the present study we have investigated the effects of chronic (30 or 60 days) exposure to ozone on olfactory perception and memory and on levels of lipid peroxidation, alpha and beta estrogen receptors and dopamine beta-hydroxylase in the olfactory bulb in ovariectomized female rats. The ability of 17beta-estradiol to prevent these effects was then assessed. Results showed that ozone exposure for 30 or 60 days impaired formation/retention of a selective olfactory recognition memory 120 min after exposure to a juvenile stimulus animal with the effect at 60 days being significantly greater than at 30 days. They also showed impaired speed in locating a buried chocolate reward after 60 days of ozone exposure indicating some loss of olfactory perception. These functional impairments could all be prevented by coincident estradiol treatment. In the olfactory bulb, levels of lipid peroxidation were increased at both 30- and 60-day time-points and numbers of cells with immunohistochemical staining for alpha and beta estrogen receptors, and dopamine beta-hydroxylase were reduced as were alpha and beta estrogen receptor protein levels. These effects were prevented by estradiol treatment. Oxidative stress damage caused by chronic exposure to ozone does therefore impair olfactory perception and social recognition memory and may do so by reducing noradrenergic and estrogen receptor activity in the olfactory bulb. That these effects can be prevented by estradiol treatment suggests increased susceptibility to neurodegenerative disorders in aging women may be contributed to by reduced estrogen levels post-menopause.

Ozone in the southeastern United States: An observation-based model using measurements from the SEARCH network

NASA Astrophysics Data System (ADS)

Blanchard, C. L.; Hidy, G. M.; Tanenbaum, S.

2014-05-01

A generalized additive model (GAM) is used to examine the influence of meteorological factors, nitrogen oxides (NOx = NO + NO2), and non-methane hydrocarbons (NMOC) on daily peak 8-h ozone (O3) concentrations. Application to 2002-2011 monitoring data from the Southeastern Aerosol Research and Characterization (SEARCH) program showed sensitivity of peak 8-h O3 to morning concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) and to afternoon concentrations of NO2 reaction products (NOz). Peak O3 decreased with increasing NO and increased with increasing NO2 concentrations, consistent with reactions involving O3, NO, and NO2. Ozone production efficiency (OPE), estimated from the modeled relation between peak 8-h O3 and afternoon NOz, was ˜40-100 percent higher at rural compared to urban sites. OPE was nonlinear at all sites, decreasing with increasing NOz concentration. The mean ratio of NOz/NOy showed a two-fold increase from urban to rural sites, associated with chemical aging in stagnant air masses from one day (urban sites) to two or more days (non-urban sites). Peak 8-h O3 concentrations in Atlanta were sensitive to concentrations of both non-biogenic NMOC and NOz. Non-urban Yorkville, Georgia, peak 8-h O3 concentrations were sensitive to NOz but not to non-biogenic NMOC concentrations. The results are consistent with expected NMOC and NOx sensitivity in urban and non-urban locales.

Characterization of N-nitrosodimethylamine formation from the ozonation of ranitidine.

PubMed

Lv, Juan; Wang, Lin; Li, Yongmei

2017-08-01

N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product which is formed during water disinfection in the presence of amine-based precursors. Ranitidine, as one kind of amine-based pharmaceuticals, has been identified as NDMA precursor with high NDMA molar conversion during chloramination. This study focused on the characterization of NDMA formation during ozonation of ranitidine. Influences of operational variables (ozone dose, pH value) and water matrix on NDMA generation as well as ranitidine degradation were evaluated. The results indicate high reactivity of ranitidine with ozone. Dimethylamine (DMA) and NDMA were generated due to ranitidine oxidation. High pH value caused more NDMA accumulation. NDMA formation was inhibited under acid conditions (pH≤5) mainly due to the protonation of amines. Water matrix such as HCO 3 - and humic acid impacted NDMA generation due to OH scavenging. Compared with OH, ozone molecules dominated the productions of DMA and NDMA. However, OH was a critical factor in NDMA degradation. Transformation products of ranitidine during ozonation were identified using gas chromatography-mass spectrometry. Among these products, just DMA and N,N-dimethylformamide could contribute to NDMA formation due to the DMA group in the molecular structures. The NDMA formation pathway from ranitidine ozonation was also proposed. Copyright © 2017. Published by Elsevier B.V.

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.

The efficacy of gaseous ozone against different forms of Candida albicans

PubMed Central

Zargaran, M; Fatahinia, M; Zarei Mahmoudabadi, A

2017-01-01

Background and Purpose: Ozone is an inorganic molecule with effective antimicrobial properties. Clinical treatment of ozonated water was used for the elimination of Candida albicans, Enterococcus faecalis, endotoxins, and biofilms from root canals. In addition, its therapeutic effects for tinea pedis, ulcers, and leishmaniasis were investigated. The purpose of the present study was to evaluate the fungicidal effects of ozone on different forms of C. albicans. In addition, antifungal susceptibility profile of strains was assessed before and after exposure to ozone. Materials and Methods: Fifty strains of C. albicans were exposed to gaseous ozone at different times. Furthermore, biofilm formation and germ tube production were evaluated when yeast suspensions were exposed to ozone. In addition, antifungal susceptibility of ozone resistant colonies was investiagted as compared to controls. Results: Ozone was highly effective in killing C. albicans in yeast form and inhibition of germ tube formation during 210 and 180 s, respectively. Although with increasing exposure time biofilm production was considerably decreased, resistance to ozone was much higher among vaginal and nail isolates even after 60 min. All the strains were sensitive to fluconazole, caspofungin, and terbinafine pre- and post-ozone exposure. Resistance to amphotericin B was significantly enhanced after exposure to ozone. Conclusion: Although ozone was highly effective on the yeast form of C. albicans and it can inhibit the formation of germ tubes in C. albicans, the complete removal of biofilms did not happen even after 60 min. It seems that ozone therapy induces resistance to amphotericin B. PMID:29354778

Effect of ozonation on minocycline degradation and N-Nitrosodimethylamine formation.

PubMed

Lv, Juan; Li, Yong M

2018-06-07

The objective of this study was to assess reactivity of Minocycline (MNC) towards ozone and determine the effects of ozone dose, pH value, and water matrix on MNC degradation as well as to characterize N-Nitrosodimethylamine (NDMA) formation from MNC ozonation. The MNC initial concentration of the solution was set in the range of 2-20 mg/L to investigate NDMA formation during MNC ozonation. Four ozone doses (22.5, 37.2, 58.0, and 74.4 mg/min) were tested to study the effect of ozone dose. For the evaluation of effects of pH value, pH was adjusted from 5 to 9 in the presence of phosphate buffer. MNC ozonation experiments were also conducted in natural water to assess the influence of water matirx. The influence of the typical component of natural water was also investigated with the addition of HA and NaHCO 3 solution. Results indicated that ozone was effective in MNC removal. Consequently, NDMA and dimethylamine (DMA) were generated from MNC oxidation. Increasing pH value enhanced MNC removal but led to greater NDMA generation. Water matrices, such as HCO 3 - and humic acid, affected MNC degradation. Conversely, more NDMA accumulated due to the inhibition of NDMA oxidation by oxidant consumption. Though ⋅OH can enhance MNC degradation, ozone molecules were heavily involved in NDMA production. Seven transformation products were identified. However, only DMA and the unidentified tertiary amine containing DMA group contributed to NDMA formation.

Ozone in remote areas of the Southern Rocky Mountains

Treesearch

Robert C. Musselman; John L. Korfmacher

2014-01-01

Ozone (O3) data are sparse for remote, non-urban mountain areas of the western U.S. Ozone was monitored 2007e2011 at high elevation sites in national forests in Colorado and northeastern Utah using a portable battery-powered O3 monitor. The data suggest that many of these remote locations already have O3 concentrations that would contribute to exceedance of the current...

[Ru/AC catalyzed ozonation of recalcitrant organic compounds].

PubMed

Wang, Jian-Bing; Hou, Shao-Pei; Zhou, Yun-Rui; Zhu, Wan-Peng; He, Xu-Wen

2009-09-15

Ozonation and Ru/AC catalyzed ozonation of dimethyl phthalate (DMP), phenols and disinfection by-products precursors were studied. It shows that Ru/AC catalyst can obviously enhance the mineralization of organic compounds. In the degradation of DMP, TOC removal was 28.84% by ozonation alone while it was 66.13% by catalytic ozonation. In the oxidation of 23 kinds of phenols, TOC removals were 9.57%-56.08% by ozonation alone while they were 41.81%-82.32% by catalytic ozonation. Compared to ozonation alone, Ru/AC catalyzed ozonation was more effective for the reduction of disinfection by-products formation potentials in source water. The reduction of haloacetic acids formation potentials was more obvious than thichlomethane formation potentials. After the treatment by catalytic ozonation, the haloacetic acids formation potentials decreased from 144.02 microg/L to 58.50 microg/L, which was below the standard value of EPA. However ozonation alone could not make it reach the standard. The treatments of source water by BAC, O3 + BAC, O3/AC + BAC and Ru/AC + O3 + BAC were also studied. In the four processes, TOC removal was 3.80%, 20.14%, 27.45% and 48.30% respectively, COD removal was 4.37%, 27.22%, 39.91% and 50.00% respectively, UV254 removal was 8.16%, 62.24%, 67.03% and 84.95% respectively. Ru/AC + O3 + BAC process is more effective than the other processes for the removal of TOC, COD and UV254 and no ruthenium leaching observed in the solution. It is a promising process for the treatment of micro polluted source water.

75 FR 48582 - Approval and Promulgation of Implementation Plans and Operating Permits Program; State of Nebraska

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-11

... the basis that these compounds make a negligible contribution to tropospheric ozone formation. These... has a negligible contribution to tropospheric ozone formation, and need not be considered in..., Incorporation by reference, Intergovernmental relations, Nitrogen dioxide, Ozone, Particulate matter, Reporting...

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.

Biogenic volatile organic compounds from the urban forest of the Metropolitan Region, Chile.

PubMed

Préndez, Margarita; Carvajal, Virginia; Corada, Karina; Morales, Johanna; Alarcón, Francis; Peralta, Hugo

2013-12-01

Tropospheric ozone is a secondary pollutant whose primary sources are volatile organic compounds and nitrogen oxides. The national standard is exceeded on a third of summer days in some areas of the Chilean Metropolitan Region (MR). This study reports normalized springtime experimental emissions factors (EF) for biogenic volatile organic compounds from tree species corresponding to approximately 31% of urban trees in the MR. A Photochemical Ozone Creation Index (POCI) was calculated using Photochemical Ozone Creation Potential of quantified terpenes. Ten species, natives and exotics, were analysed using static enclosure technique. Terpene quantification was performed using GC-FID, thermal desorption, cryogenic concentration and automatic injection. Observed EF and POCI values for terpenes from exotic species were 78 times greater than native values; within the same family, exotic EF and POCI values were 28 and 26 times greater than natives. These results support reforestation with native species for improved urban pollution management. Copyright © 2013 Elsevier Ltd. All rights reserved.

Secondary Organic Aerosol Formation from the Photooxidation of Naphthalene

NASA Astrophysics Data System (ADS)

Zhou, S.; Chen, Y.; Wenger, J.

2009-04-01

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants that are released into the atmosphere as a by-product of combustion processes. The gas-phase PAHs can be chemically transformed via reaction with the hydroxyl radical to produce a range of oxidised organic compounds and other pollutants such as ozone and secondary organic aerosol (SOA). Epidemiological studies have established that exposure to this type of air pollution is associated with damaging effects on the respiratory and cardiovascular systems, and can lead to asthma, oxidative stress, health deterioration and even death. The major anthropogenic source of SOA in urban areas is believed to be aromatic hydrocarbons, which are present in automobile fuels and are used as solvents. As a result, research is currently being performed on the characterisation of SOA produced from aromatic hydrocarbons such as toluene, the xylenes and trimethylbenzenes. However, significant amounts of PAHs are also released into urban areas from automobile emissions and the combustion of fossil fuels for home heating. Naphthalene is regularly cited as the most abundant PAH in polluted urban air, with typical ambient air concentrations of 0.05 - 0.20 parts per billion (ppbV) in European cities, comparable to the xylenes. Since naphthalene reacts in an analogous manner to monocyclic aromatic compounds then it is also expected to make a significant contribution to ambient SOA. However, the yield and chemical composition of SOA produced from the atmospheric degradation of naphthalene is not well known. In this presentation, the effects of NOx level and relative humidity on the SOA formation from the phootooixdation of naphthalene will be presented. A series of experiments has been performed in a large atmospheric simulation chamber equipped with a gas chromatograph and analyzers for monitoring nitrogen oxides (NOx) and ozone. SOA formation from the photooxidation of naphthalene was measured using a scanning mobility particle sizer. The effect of NOx concentration on SOA formation was evaluated by varying the initial naphthalene and NOx concentrations. The results clearly show that a higher hydrocarbon to NOx ratio produces a higher yield of SOA. The SOA mass yields were also found to increase as the relative humidity was raised from 0 to 50%. A recently developed denuder-filter sampling technique was used to investigate the gas/particle partitioning behavior of the photooxidation products. This work is the first study of the formation of SOA from naphthalene and the results will be compared to those obtained from other aromatic compounds.

College Students' Understanding of Atmospheric Ozone Formation

ERIC Educational Resources Information Center

Howard, Kristen E.; Brown, Shane A.; Chung, Serena H.; Jobson, B. Thomas; VanReken, Timothy M.

2013-01-01

Research has shown that high school and college students have a lack of conceptual understanding of global warming, ozone, and the greenhouse effect. Most research in this area used survey methodologies and did not include concepts of atmospheric chemistry and ozone formation. This study investigates college students' understandings of atmospheric…

THE EFFECTS OF COMBINED OZONATION AND FILTRATION ON DISINFECTION BY-PRODUCT FORMATION. (R830908)

EPA Science Inventory

The effects of combined ozonation and membrane filtration on the removal of the natural organic matter (NOM) and the formation of disinfection by-products (DBPs) were investigated. Ozonation/filtration resulted in a reduction of up to 50% in the dissolved organic carbon (DOC) ...

Use of ozone-biofiltration for bulk organic removal and disinfection byproduct mitigation in potable reuse applications.

PubMed

Arnold, Mayara; Batista, Jacimaria; Dickenson, Eric; Gerrity, Daniel

2018-07-01

The purpose of this research was to investigate the impacts of ozone dose and empty bed contact time (EBCT) in ozone-biofiltration systems on disinfection byproduct (DBP) formation potential. The data were used to evaluate the possibility of using DBP formation potential as an alternative guideline for total organic carbon (TOC) removal in potable reuse applications. A pilot-scale ozone-biofiltration system was operated with O 3 /TOC ratios ranging from 0.1 to 2.25 and EBCTs ranging from 2 to 20 min. The biofiltration columns contained anthracite or biological activated carbon (BAC). Bench-scale chlorination was performed using the uniform formation conditions (UFC) approach, and quenched samples were analyzed for total trihalomethanes (TTHMs) and regulated haloacetic acids (HAA5s). The data demonstrated that ozone-biofiltration achieved TOC removals ranging from ∼10 to 30%, depending on operational conditions, but biofiltration without ozone generally achieved <10% TOC removal. UFC testing demonstrated that ozone alone was efficient in transforming bulk organic matter and reducing DBP formation potential by 10-30%. The synergistic combination of ozone and biofiltration achieved average overall reductions in TTHM and HAA5 formation potential of 26% and 51%, respectively. Finally, a maximum TOC concentration of 2.0 mg/L was identified as a recommended treatment target for reliable compliance with TTHM and HAA5 regulations for potable reuse systems in the United States. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

Gas-phase chemiluminescent reactions of ozone with monoterpenes

NASA Astrophysics Data System (ADS)

Arora, P. K.; Chatha, J. P. S.; Vohra, K. G.

1983-08-01

Chemiluminescent reactions of ozone with monoterpenes such as linallol, geraniol, d-limonene and α-pinene have been studied in the gas phase at low pressures. Methylglyoxal phosphorescence has been observed in the first two reactions. Emissions from HCHO( 1A 2) and glyoxal ( 3A u) are observed in the reaction of ozone with d-limonene and formation of excited glyoxal is found to be first order in ozone. The reaction of ozone with β-pinene gives rise to emission from a α-dicarbonyl compound and this is found to be first order in ozone. The mechanisms for the formation of excited species are proposed.

PHOTOCHEMICAL PRODUCTS IN URBAN MIXTURES ENHANCE INFLAMMATORY RESPONSES IN LUNG CELLS

EPA Science Inventory

Complex urban air mixtures that realistically mimic urban smog can be generated for investigating adverse health effects. "Smog chambers" have been used for over 30 yr to conduct experiments for developing and testing photochemical models that predict ambient ozone (O(3)) concent...

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.;

Inheritance of ozone resistance in tall fescue

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

Johnston, W.J.; Haaland, R.L.; Dickens, R.

Ozone is considered the most important air pollutant affecting vegetation. With progressive urbanization, ozone levels have steadily escalated. Reports suggest that ozone tolerance is a highly heritable characteristic and that the selection of resistant plants and breeding for ozone resistance should be possible. This study was undertaken to gain information on the inheritance of ozone resistance in tall fescue (Festuca arundinacea Schreb.).Progenies from a diallel among six tall fescue genotypes of diverse origin were evaluated for ozone resistance in a fumigation-chamber. Sixteen-day-old seedlings were exposed to 0.5 ppm ozone for 3 hours and scored for injury after 3 days. Generalmore » combining ability (GCA) and reciprocal effects were both highly significant; however, GCA constituted a major portion of the genotypic variation. Specific combining ability was not significant. The predominance of additive genetic variance observed indicates that breeding for ozone resistance in this tall fescue population should be possible.« less

Ozone concentrations at a selected high-elevation forest site downwind Mexico City

NASA Astrophysics Data System (ADS)

Torres-JArdon, R.

2013-05-01

Torres-Jardón, R.*, Rosas-Pérez, I., Granada-Macías, L. M., Ruiz-Suárez, L. G. Centro de Ciencias de la Atmósfera, UNAM, México D. F. México * rtorres@unam.mx For many years, the vegetation of forest species such as Abies religiosa in natural parks located in the southwest mountains of Mexico City has attracted much attention since these parks have been experiencing a severe decline of unclear etiology. The high ozone levels in the area and the observed naked eye macroscopic, histological and cytological injuries on these species, strongly suggest an important contribution of tropospheric ozone to this deterioration process. Apart of historical short monitoring campaigns for measuring ozone levels in these mountains, it is known just a little is known about the present exposure levels at which the local vegetation is exposed. A continuous ozone analyzer has been in operation since 2011 at a high-elevation forest site (Parque Nacional Miguel Hidalgo, PNMH; 3110 m above mean sea level) located downwind of Mexico City Metropolitan Area (MCMA), in order to characterize the local ozone diel amplitude and its seasonal trend, as well as the influence of MCMA on the local O3 concentrations. Hourly average ozone data in PNMH shows that in general, the diel of ozone concentrations in the forest site has a statistical significant correlation with the pattern of ozone levels observed in several monitoring sites (smog receptor sites) within the MCMA, although the high elevation O3 levels are relatively lower than those in the urban area (around 2200 m above mean sea level). It is possible that a part of the oxidants in the air masses are removed by sink deposition processes during the air mass transport across the hills. The diel amplitude of ozone concentrations is small in the cold season, increasing as the seasons advance to June. As in the city, the highest ozone concentrations occur in April or May and the lowest levels during the rainy season, which extends from July to September. Episodes of high concentrations occurred mainly during the dry warm months. Most of the year, nocturnal ozone levels were higher than those registered in the urban area due to the PMH altitude. As a great part of the mountain terrain regularly is above the nocturnal mixing layer formed each day on the valley floor, the ozone remanent levels above this layer in the mountains are kept isolated from urban NOx emissions generated at night. An evaluation of the AOT40 indicator shows that the forest zone is under a strong risk due to ozone pollution. A preliminary analysis of several ozone events in the PNMH shows the suppression of the diel peak, suggesting that a stratospheric intrusion of ozone occurs frequently in high-elevation sites surrounding MCMA.

Intercontinental Transport of Tropical Ozone from Biomass Burning: Views from Satellite and SHADOZ (Southern Hemisphere Additional Ozonesondes)

NASA Technical Reports Server (NTRS)

Thompson, A. M.; Witte, J. C.; Chatfield, R. B.; Guam, H.

2003-01-01

There has been interest in the connection between tropical fires and ozone since about 1980. Photochemically reactive gases released by fires (e.g. NO, CO, volatile organic carbon) interact as they do in an urban environment to form ozone. Interacting with chemical sources, tropical meteorology plays a part in tropospheric ozone distributions in the tropics, through large-scale circulation, deep convection, and regional phenomena like the West African and Asian monsoons. An overview of observations, taken from satellite and from ozone soundings, illustrates regional influences and intercontinental- range ozone transport in the tropics. One of the most striking findings is evidence for impacts of Indian Ocean pollution on the south Atlantic ozone maximum referred to as the "ozone paradox" [Thompson et al., GRL, 2000; JGR, 2003; Chatfield et al., GRL, 20031.

Improving emissions inventories in North America through systematic analysis of model performance during ICARTT and MILAGRO

NASA Astrophysics Data System (ADS)

Mena, Marcelo Andres

During 2004 and 2006 the University of Iowa provided air quality forecast support for flight planning of the ICARTT and MILAGRO field campaigns. A method for improvement of model performance in comparison to observations is showed. The method allows identifying sources of model error from boundary conditions and emissions inventories. Simultaneous analysis of horizontal interpolation of model error and error covariance showed that error in ozone modeling is highly correlated to the error of its precursors, and that there is geographical correlation also. During ICARTT ozone modeling error was improved by updating from the National Emissions Inventory from 1999 and 2001, and furthermore by updating large point source emissions from continuous monitoring data. Further improvements were achieved by reducing area emissions of NOx y 60% for states in the Southeast United States. Ozone error was highly correlated to NOy error during this campaign. Also ozone production in the United States was most sensitive to NOx emissions. During MILAGRO model performance in terms of correlation coefficients was higher, but model error in ozone modeling was high due overestimation of NOx and VOC emissions in Mexico City during forecasting. Large model improvements were shown by decreasing NOx emissions in Mexico City by 50% and VOC by 60%. Recurring ozone error is spatially correlated to CO and NOy error. Sensitivity studies show that Mexico City aerosol can reduce regional photolysis rates by 40% and ozone formation by 5-10%. Mexico City emissions can enhance NOy and O3 concentrations over the Gulf of Mexico in up to 10-20%. Mexico City emissions can convert regional ozone production regimes from VOC to NOx limited. A method of interpolation of observations along flight tracks is shown, which can be used to infer on the direction of outflow plumes. The use of ratios such as O3/NOy and NOx/NOy can be used to provide information on chemical characteristics of the plume, such as age, and ozone production regime. Interpolated MTBE observations can be used as a tracer of urban mobile source emissions. Finally procedures for estimating and gridding emissions inventories in Brazil and Mexico are presented.

N-nitrosodimethylamine formation upon ozonation and identification of precursors source in a municipal wastewater treatment plant.

PubMed

Sgroi, Massimiliano; Roccaro, Paolo; Oelker, Gregg L; Snyder, Shane A

2014-09-02

Ozone doses normalized to the dissolved organic carbon concentration were applied to the primary influent, primary effluent, and secondary effluent of a wastewater treatment plant producing water destined for potable reuse. Results showed the most N-Nitrosodimethylamine (NDMA) production from primary effluent, and the recycle streams entering the primary clarifiers were identified as the main source of NDMA precursors. The degradation of aminomethylated polyacrylamide (Mannich) polymer used for sludge treatment was a significant cause of precursor occurrence. A strong correlation between NDMA formation and ammonia concentration was found suggesting an important role of ammonia oxidation on NDMA production. During ozonation tests in DI water using dimethylamine (DMA) as model precursor, the NDMA yield significantly increased in the presence of ammonia and bromide due to the formation of hydroxylamine and brominated nitrogenous oxidants. In addition, NDMA formation during ozonation of dimethylformamide (DMF), the other model precursor used in this study, occurred only in the presence of ammonia, and it was attributable to the oxidation of DMF by hydroxyl radicals. Filtered wastewater samples (0.7 μm) produced more NDMA than unfiltered samples, suggesting that ozone reacted with dissolved precursors and supporting the hypothesis of polymer degradation. Particularly, the total suspended solids content similarly affected NDMA formation and the UV absorbance decrease during ozonation due to the different ozone demand created in filtered and unfiltered samples.

Measurements of the potential ozone production rate in a forest

NASA Astrophysics Data System (ADS)

Crilley, L.; Sklaveniti, S.; Kramer, L.; Bloss, W.; Flynn, J. H., III; Alvarez, S. L.; Erickson, M.; Dusanter, S.; Locoge, N.; Stevens, P. S.; Millet, D. B.; Alwe, H. D.

2017-12-01

Biogenic volatile organic compounds (BVOC) are a significant source of organic compounds globally and alongside NOx play a key role in the formation of ozone in the troposphere. Understanding how changes in NOx concentrations feed through to altered ozone production in BVOC dominated environments will aid our understanding of future atmospheric composition, notably as developing nations transition from NOx dominated to NOx limited chemistry as a result of mitigation strategies. Here we empirically investigate this ambient ozone formation potential. We report deployment of a custom built instrument to measure in near real time the potential for in situ chemical ozone production, using an artificial light source. Our results are thus indicative of the ozone formation potential for a sampled ambient air mixture, including full VOC complexity, i.e. independent of characterization of individual organic compounds. Ground level measurements were performed as part of the PROPHET-AMOS 2016 field campaign, at a site located within a Northern Michigan forest that has typically low NOx abundance, but high isoprene and terpenoid loadings. As the ambient NOx concentrations were low during the campaign, experiments were performed in which NO was artificially added to the sampled ambient air mixture, to quantify changes in the potential ozone production rate as a function of NOx, and hence the ozone forming characteristics of the ambient air. Preliminarily results from these experiments are presented, and indicate that while ozone production increases with added NO, significant variation was observed for a given NO addition, reflecting differences in the ambient VOC chemical reactivity and ozone formation tendency.

EFFECT OF OZONE ON DIESEL EXHAUST PARTICLE TOXICITY

EPA Science Inventory

Ambient particulate matter (PM) concentrations have been associated with mortality and morbidity. Diesel exhaust particles (DEP) are present in ambient urban air PM. Coexisting with DEP (and PM) is ozone (O(3)), which has the potential to react with some components of DEP. Some r...

Biodegradability of DBP precursors after drinking water ozonation.

PubMed

de Vera, Glen Andrew; Keller, Jurg; Gernjak, Wolfgang; Weinberg, Howard; Farré, Maria José

2016-12-01

Ozonation is known to generate biodegradable organic matter, which is typically reduced by biological filtration to avoid bacterial regrowth in distribution systems. Post-chlorination generates halogenated disinfection byproducts (DBPs) but little is known about the biodegradability of their precursors. This study determined the effect of ozonation and biofiltration conditions, specifically ozone exposure and empty bed contact time (EBCT), on the control of DBP formation potentials in drinking water. Ozone exposure was varied through addition of H 2 O 2 during ozonation at 1 mgO 3 /mgDOC followed by biological filtration using either activated carbon (BAC) or anthracite. Ozonation led to a 10% decrease in dissolved organic carbon (DOC), without further improvement from H 2 O 2 addition. Raising H 2 O 2 concentrations from 0 to 2 mmol/mmolO 3 resulted in increased DBP formation potentials during post-chlorination of the ozonated water (target Cl 2 residual after 24 h = 1-2 mg/L) as follows: 4 trihalomethanes (THM4, 37%), 8 haloacetic acids (HAA8, 44%), chloral hydrate (CH, 107%), 2 haloketones (HK2, 97%), 4 haloacetonitriles (HAN4, 33%), trichloroacetamide (TCAM, 43%), and adsorbable organic halogen (AOX, 27%), but a decrease in the concentrations of 2 trihalonitromethanes (THNM2, 43%). Coupling ozonation with biofiltration prior to chlorination effectively lowered the formation potentials of all DBPs including CH, HK2, and THNM2, all of which increased after ozonation. The dynamics of DBP formation potentials during BAC filtration at different EBCTs followed first-order reaction kinetics. Minimum steady-state concentrations were attained at an EBCT of about 10-20 min, depending on the DBP species. The rate of reduction in DBP formation potentials varied among individual species before reaching their minimum concentrations. CH, HK2, and THNM2 had the highest rate constants of between 0.5 and 0.6 min -1 followed by HAN4 (0.4 min -1 ), THM4 (0.3 min -1 ), HAA8 (0.2 min -1 ), and AOX (0.1 min -1 ). At an EBCT of 15 min, the reduction in formation potential for most DBPs was less than 50% but was higher than 70% for CH, HK2, and THNM2. The formation of bromine-containing DBPs increased with increasing EBCT, most likely due to an increase in Br - /DOC ratio. Overall, this study demonstrated that the combination of ozonation and biofiltration is an effective approach to mitigate DBP formation during drinking water treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Remote Sensing Characterization of the Urban Landscape for Improvement of Air Quality Modeling

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Estes, Maurice G., Jr.; Khan, Maudood

2005-01-01

The urban landscape is inherently complex and this complexity is not adequately captured in air quality models, particularly the Community Multiscale Air Quality (CMAQ) model that is used to assess whether urban areas are in attainment of EPA air quality standards, primarily for ground level ozone. This inadequacy of the CMAQ model to sufficiently respond to the heterogeneous nature of the urban landscape can impact how well the model predicts ozone pollutant levels over metropolitan areas and ultimately, whether cities exceed EPA ozone air quality standards. We are exploring the utility of high-resolution remote sensing data and urban growth projections as improved inputs to the meteorology component of the CMAQ model focusing on the Atlanta, Georgia metropolitan area as a case study. These growth projections include "business as usual" and "smart growth" scenarios out to 2030. The growth projections illustrate the effects of employing urban heat island mitigation strategies, such as increasing tree canopy and albedo across the Atlanta metro area, in moderating ground-level ozone and air temperature, compared to "business as usual" simulations in which heat island mitigation strategies are not applied. The National Land Cover Dataset at 30m resolution is being used as the land use/land cover input and aggregated to the 4km scale for the MM5 mesoscale meteorological model and the (CMAQ) modeling schemes. Use of these data has been found to better characterize low densityhburban development as compared with USGS 1 km land use/land cover data that have traditionally been used in modeling. Air quality prediction for fiture scenarios to 2030 is being facilitated by land use projections using a spatial growth model. Land use projections were developed using the 2030 Regional Transportation Plan developed by the Atlanta Regional Commission, the regional planning agency for the area. This allows the state Environmental Protection agency to evaluate how these transportation plans will affect fbture air quality.

Fluxes of ozone and Biogenic Volatile Organic Compounds in a mixed Mediterranean forest over a transition period between summer and fall

NASA Astrophysics Data System (ADS)

Fares, S.; Schnitzhofer, R.; Hansel, A.; Petersson, F.; Matteucci, G.; Scarascia Mugnozza, G.; Jiang, X.; Guenther, A. B.; Loreto, F.

2012-12-01

Mediterranean plant ecosystems are exposed to abiotic stressors that may be exacerbated by climate change dynamics. Moreover, plants need now to cope with increasing anthropogenic pressures, often associated with expanding impacts of urbanization. Anthropogenic stressors include harmful gases (e.g. ozone,) that are transported from anthropogenic pollution sources to the vegetation. They may alter ecophysiology and compromise metabolism of Mediterranean plants. A disproportionate number of Mediterranean ecosystems, many dominated by forest trees, are being transformed into "urban or pre-urban forests". This is in particular the case for Castelporziano Estate, a 6,000 ha Mediterranean forest located just 25 km from Rome downtown at the coast of the Mediterranean Sea. In September 2011 an intensive field campaign was performed in Castelporziano to investigate ozone deposition and biogenic emissions of volatile organic compounds (BVOC) from a mixed Mediterranean forest, mainly composed by Quercus suber, Quercus ilex, Pinus pinea. Measurements were performed at canopy level with fast real-time instruments (a fast ozone analyzer and a Proton Transfer Reaction-Time of Flight Mass Spectrometer) that allowed eddy covariant flux measurements of ozone and BVOC. In the transitional period from a warm and dry summer to a wet and moderately cool fall we typically observed tropospheric ozone volume mixing ratios (VMR) of 60 ppb at around noon, with high deposition fluxes (up to -10 nmol m-2 s-1) into the forest canopy. Canopy models were used to to calculate that up to 90% of ozone uptake can be attributed to non-stomatal sinks, suggesting that chemical reactions between ozone and reactive BVOC may have played an important role. The concentrations of reactive isoprenoids (e.g. sesquiterpenes) were indeed observed to decrease during the central hours of the day, in coincidence with increased ozone concentrations. Concentrations and fluxes of isoprenoid-ozone-oxidation-(methyl-vinyl-ketone and methacrolein) were found to increase during the day time hours, matching the dynamic pattern of non-stomatal ozone uptake. Monoterpenes were the most abundant BVOC emitted by the forest with fluxes up to 10 nmol m-2 s-1 in the warm days, followed by the oxygenated BVOCs: methanol, acetone, acetaldehyde. Isoprene was emitted at a low rate (less than 1 nmol m-2 s-1), and observations used to develop a new parameterization data for modelling activity. MEGAN was used to predict biogenic emissions from Mediterranean ecosystems. Model results using new basal emission factors (BEF) estimated from the collected data-set revealed considerable differences in the emission estimates compared with the standard parameterization, thus suggesting the importance of including basal emission factors from monoterpene-emitting Mediterranean ecosystems to obtain an accurate estimate in the global model. Future research by chemical transport modelling and smog chamber experiments are planned to investigate the "ex-situ" ozone-forming potential of emitted BVOC, to fully understand the role of Mediterranean urban forests in the complex interactions between biosphere and atmosphere over large Mediterranean conurbations.

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.

Bromide's effect on DBP formation, speciation, and control; Part 1: Ozonation

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

Shukairy, H.M.; Summers, R.S.; Miltner, R.J.

1994-06-01

The effect of variable ozone dosage and bromide concentration on the formation of organic disinfection by-products (DBPs) and bromate were evaluated. Low ozone dosages resulted in oxidation of organic precursors, yielding decreases in the formation potential for total trihalomethanes (THMs), six haloacetic acids (HAAs), and total organic halide (TOX). Increasing the ozone dosage oxidized bromide to bromate, decreasing the bromide for incorporation into DBPs. Bromate concentrations were linearly correlated with ozone residuals. Changes in the bromine incorporation factors n and n[prime] reflected differences in the resulting speciation of THMs and HAAs, respectively. Because TOX measurements based on chloride equivalence maymore » underestimate the halogenated DBP yield for high-bromide waters, a procedure is described whereby bromide and bromate concentrations were used to correct the TOX measurement.« less

Air quality in the megacity of São Paulo: Evolution over the last 30 years and future perspectives

NASA Astrophysics Data System (ADS)

Andrade, Maria de Fatima; Kumar, Prashant; de Freitas, Edmilson Dias; Ynoue, Rita Yuri; Martins, Jorge; Martins, Leila D.; Nogueira, Thiago; Perez-Martinez, Pedro; de Miranda, Regina Maura; Albuquerque, Taciana; Gonçalves, Fabio Luiz Teixeira; Oyama, Beatriz; Zhang, Yang

2017-06-01

We present a comprehensive review of published results from the last 30 years regarding the sources and atmospheric characteristics of particles and ozone in the Metropolitan Area of São Paulo (MASP). During the last 30 years, many efforts have been made to describe the emissions sources and to analyse the primary and secondary formation of pollutants under a process of increasing urbanisation in the metropolitan area. From the occurrence of frequent violations of air quality standards in the 1970s and 1980s (due to the uncontrolled air pollution sources) to a substantial decrease in the concentrations of the primary pollutants, many regulations have been imposed and enforced, although those concentrations do not yet conform to the World Health Organization guidelines. The greatest challenge currently faced by the São Paulo State Environmental Protection Agency and the local community is controlling secondary pollutants such as ozone and fine particles. Understanding the formation of these secondary pollutants, by experimental or modelling approaches, requires the description of the atmospheric chemical processes driven by biofuel, ethanol and biodiesel emissions. Exposure to air pollution is the cause of many injuries to human health, according to many studies performed not only in the region but also worldwide, and affects susceptible populations such as children and the elderly. The MASP is the biggest megacity in the Southern Hemisphere, and its specifics are important for other urban areas that are facing the challenge of intensive growth that puts pressure on natural resources and worsens the living conditions in urban areas. This text discusses how imposing regulations on air quality and emission sources, mainly related to the transportation sector, has affected the evolution of pollutant concentrations in the MASP.

Source Apportionment of Volatile Organic Compounds in an Urban Environment at the Yangtze River Delta, China.

PubMed

An, Junlin; Wang, Junxiu; Zhang, Yuxin; Zhu, Bin

2017-04-01

Volatile organic compounds (VOCs) were collected continuously during June-August 2013 and December 2013-February 2014 at an urban site in Nanjing in the Yangtze River Delta. The positive matrix factorization receptor model was used to analyse the sources of VOCs in different seasons. Eight and seven sources were identified in summer and winter, respectively. In summer and winter, the dominant sources of VOCs were vehicular emissions, liquefied petroleum gas/natural gas (LPG/NG) usage, solvent usage, biomass/biofuel burning, and industrial production. In summer, vehicular emissions made the most significant contribution to ambient VOCs (38%), followed by LPG/NG usage (20%), solvent usage (19%), biomass/biofuel burning (13%), and industrial production (10%). In winter, LPG/NG usage accounted for 36% of ambient VOCs, whereas vehicular emissions, biomass/biofuel burning, industrial production and solvent usage contributed 30, 18, 9, and 6%, respectively. The contribution of LPG/NG usage in winter was approximately four times that in summer, whereas the contribution from biomass/biofuel burning in winter was more than twice that in summer. The sources related to vehicular emissions and LPG/NG usages were important. Using conditional probability function analysis, the VOC sources were mainly associated with easterly, northeasterly and southeasterly directions, pointing towards the major expressway and industrial area. Using the propylene-equivalent method, paint and varnish (23%) was the highest source of VOCs in summer and biomass/biofuel burning (36%) in winter. Using the ozone formation potential method, the most important source was biomass/biofuel burning (32% in summer and 47% in winter). The result suggests that the biomass/biofuel burning and paint and varnish play important roles in controlling ozone chemical formation in Nanjing.

Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

NASA Astrophysics Data System (ADS)

Brown, S. S.; Dubé, W. P.; Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; Warneke, C.; de Gouw, J. A.; Washenfelder, R. A.; Atlas, E.; Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Schwarz, J. P.; Spackman, R.; Trainer, M.; Parrish, D. D.; Fehshenfeld, F. C.; Ravishankara, A. R.

2013-11-01

Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter category serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100-400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2-2.7 ppbv h-1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1 ppbv h-1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Some profiles may have been influenced by biomass burning sources as well, making quantitative attribution of organic aerosol sources difficult. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m-3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m-3.

Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

NASA Astrophysics Data System (ADS)

Brown, S. S.; Dubé, W. P.; Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; Warneke, C.; de Gouw, J. A.; Washenfelder, R. A.; Atlas, E.; Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Schwarz, J. P.; Spackman, R.; Trainer, M.; Parrish, D. D.; Fehshenfeld, F. C.; Ravishankara, A. R.

2013-05-01

Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100-400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2-2.7ppbv h-1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1ppbv h-1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m-3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m-3.

Causes of ozone pollution in summer in Wuhan, Central China.

PubMed

Zeng, P; Lyu, X P; Guo, H; Cheng, H R; Jiang, F; Pan, W Z; Wang, Z W; Liang, S W; Hu, Y Q

2018-06-15

In August 2016, continuous measurements of volatile organic compounds (VOCs) and trace gases were conducted at an urban site in Wuhan. Four high-ozone (O 3 ) days and twenty-seven non-high-O 3 days were identified according to the China's National Standard Level II (∼100 ppbv). The occurrence of high-O 3 days was accompanied by tropical cyclones. Much higher concentrations of VOCs and carbon monoxide (CO) were observed on the high-O 3 days (p < 0.01). Model simulations revealed that vehicle exhausts were the dominant sources of VOCs, contributing 45.4 ± 5.2% and 37.3 ± 2.9% during high-O 3 and non-high-O 3 days, respectively. Both vehicle exhausts and stationary combustion made significantly larger contributions to O 3 production on high-O 3 days (p < 0.01). Analysis using a chemical transport model found that local photochemical formation accounted for 74.7 ± 5.8% of the daytime O 3 , around twice the regional transport (32.2 ± 5.4%), while the nighttime O 3 was mainly attributable to regional transport (59.1 ± 9.9%). The local O 3 formation was generally limited by VOCs in urban Wuhan. To effectively control O 3 pollution, the reduction ratio of VOCs to NO x concentrations should not be lower than 0.73, and the most efficient O 3 abatement could be achieved by reducing VOCs from vehicle exhausts. This study contributes to the worldwide database of O 3 -VOC-NO x sensitivity research. Its findings will be helpful in formulating and implementing emission control strategies for dealing with O 3 pollution in Wuhan. Copyright © 2018 Elsevier Ltd. All rights reserved.

Options and limitations for bromate control during ozonation of wastewater.

PubMed

Soltermann, Fabian; Abegglen, Christian; Tschui, Manfred; Stahel, Sandro; von Gunten, Urs

2017-06-01

Wastewater treatment plants (WWTPs) are important point sources for micropollutants, which are harmful to freshwater organisms. Ozonation of wastewater is a powerful option to abate micropollutants, but may result in the formation of the potentially toxic oxidation by-product bromate in bromide-containing wastewaters. This study investigates options to reduce bromate formation during wastewater ozonation by (i) reducing the bromide concentration of the wastewater, (ii) lowering the ozone dose during wastewater treatment and (iii) adding hydrogen peroxide to limit the lifetime of ozone and quench the intermediates of the bromate formation pathway. Two examples demonstrate that a high share of bromide in wastewater can originate from single point sources (e.g., municipal waste incinerators or landfills). The identification of major point sources requires laborious sampling campaigns, but may facilitate the reduction of the bromide load significantly. To reduce the bromate formation by lowering the ozone dose interferes with the aim to abate micropollutants. Therefore, an additional treatment is necessary to ensure the elimination of micropollutants. Experiments at a pilot-plant illustrate that a combined treatment (ozone/powdered activated carbon) allows to eliminate micropollutants with low bromate yields. Furthermore, the addition of hydrogen peroxide was investigated at bench-scale. The bromate yields could be reduced by ∼50% and 65% for a hydrogen peroxide dose of 5 and 10 mg L -1 , respectively. In conclusion, there are options to reduce the bromate formation during wastewater ozonation, however, they are not simple with sometimes limited efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

Volatilization of low vapor pressure--volatile organic compounds (LVP-VOCs) during three cleaning products-associated activities: Potential contributions to ozone formation.

PubMed

Shin, Hyeong-Moo; McKone, Thomas E; Bennett, Deborah H

2016-06-01

There have been many studies to reduce ozone formation mostly from volatile organic compound (VOC) sources. However, the role of low vapor pressure (LVP)-VOCs from consumer products remains mostly unexplored and unaddressed. This study explores the impact of high production volume LVP-VOCs on ozone formation from three cleaning products-associated activities (dishwashing, clothes washing, and surface cleaning). We develop a model framework to account for the portion available for ozone formation during the use phase and from the down-the-drain disposal. We apply experimental studies that measured emission rates or models that were developed for estimating emission rates of organic compounds during the use phase. Then, the fraction volatilized (fvolatilized) and the fraction disposed down the drain (fdown-the-drain) are multiplied by the portion available for ozone formation for releases to the outdoor air (fO3|volatilized) and down-the-drain (fO3|down-the-drain), respectively. Overall, for chemicals used in three specific cleaning-product uses, fvolatilized is less than 0.6% for all studied LVP-VOCs. Because greater than 99.4% of compounds are disposed of down the drain during the use phase, when combined with fO3|volatilized and fO3|down-the-drain, the portion available for ozone formation from the direct releases to outdoor air and the down-the-drain disposal is less than 0.4% and 0.2%, respectively. The results from this study indicate that the impact of the studied LVP-VOCs on ozone formation is very sensitive to what occurs during the use phase and suggest the need for future research on experimental work at the point of use. Copyright © 2016 Elsevier Ltd. All rights reserved.

Free tropospheric ozone production following entrainment of urban plumes into deep convection

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Dickerson, Russell R.; Simpson, Joanne

1992-01-01

It is shown that rapid vertical transport of air from urban plumes through deep convective clouds can cause substantial enhancement of the rate of O3 production in the free troposphere. Simulation of convective redistribution and subsequent photochemistry of an urban plume from Oklahoma City during the 1985 PRESTORM campaign shows enhancement of O3 production in the free tropospheric cloud outflow layer by a factor of almost 4. In contrast, simulation of convective transport of an urban plume from Manaus, Brazil, into a prestine free troposphere during GTE/ABLE 2B (1987), followed by a photochemical simulation, showed enhancement of O3 production by a factor of 35. The reasons for the different enhancements are (1) intensity of cloud vertical motion; (2) initial boundary layer O3 precursor concentrations; and (3) initial amount of background free tropospheric NO(x). Convective transport of ozone precursors to the middle and upper troposphere allows the resulting O3 to spread over large geographic regions, rather than being confined to the lower troposphere where loss processes are much more rapid. Conversely, as air with lower NO descends and replaces more polluted air, there is greater O3 production efficiency per molecule of NO in the boundary layer following convective transport. As a result, over 30 percent more ozone could be produced in the entire tropospheric column in the first 24 hours following convective transport of urban plumes.

OZONE BYPRODUCT FORMATION

EPA Science Inventory

The use of ozone for water treatment has been increasing as ozone has great potential for degrading water pollutants and inactivating viruses, Giardia cysts, and Cryptosporidium oocysts. Although it appears that ozone generates less undesirable disinfection by-products (DBPs) th...

Spatio-temporal assessment and seasonal variation of tropospheric ozone in Pakistan during the last decade.

PubMed

Noreen, Asma; Khokhar, Muhammad Fahim; Zeb, Naila; Yasmin, Naila; Hakeem, Khalid Rehman

2018-03-01

This study uses the tropospheric ozone data derived from combined observations of Ozone Monitoring Instrument/Microwave Limb Sounder instruments by using the tropospheric ozone residual method. The main objective was to study the spatial distribution and temporal evolution in the troposphere ozone columns over Pakistan during the time period of 2004 to 2014. Results showed an overall increase of 3.2 ± 1.1 DU in tropospheric ozone columns over Pakistan. Spatial distribution showed enhanced ozone columns in the Punjab and southern Sindh consistent to high population, urbanization, and extensive anthropogenic activities, and exhibited statistically significant temporal increase. Seasonal variations in tropospheric ozone columns are driven by various factors such as seasonality in UV-B fluxes, seasonality in ozone precursor gases such as NO x and volatile organic compounds (caused by temperature dependent biogenic emission) and agricultural fire activities in Pakistan. A strong correlation of 96% (r = 0.96) was found between fire events and tropospheric ozone columns in Pakistan.

78 FR 11119 - Air Quality: Revision to Definition of Volatile Organic Compounds-Exclusion of trans

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-15

... tropospheric ozone formation. In the ``Rules and Regulations'' section of this Federal Register, we are making... compound makes a negligible contribution to tropospheric ozone formation.\\1\\ We are publishing a direct... standards for ozone under title I of the Clean Air Act (CAA). This proposed revision would add trans 1...

Catalytic ozonation of dimethyl phthalate and chlorination disinfection by-product precursors over Ru/AC.

PubMed

Wang, Jianbing; Zhou, Yunrui; Zhu, Wanpeng; He, Xuwen

2009-07-15

Catalytic ozonation of dimethyl phthalate (DMP) in aqueous solution (5mg/L) under various reactions was performed to examine the effect of catalyst dosage, catalyst particle size, ozone dosage, and gas flow rate on the mineralization of DMP. The mineralization of DMP can be achieved via ozonation and the presence of Ru/AC could greatly accelerate the mineralization rate of DMP in ozonation process. In the continuous experiment of the Ru/AC catalyzed ozonation of DMP, total organic carbon (TOC) removals were kept stable around 75% during 42 h reaction. No leaching of ruthenium was observed in the treated water samples. The treatment of natural water using Ru/AC+O(3), Ru/AC+O(2) and ozonation alone was studied. In the Ru/AC+O(3) process, TOC removals, the reductions of the haloacetic acid formation potentials (HAAFPs), and the reductions of the trihalomethane formation potentials (THMFPs) of 11 water samples were 22-44%, 39-61% and 50-65%, respectively. Ru/AC+O(3) process was much more effective than ozonation alone for TOC removal and the reduction of disinfection by-product formation potential (DBPFP) in the treatment of natural water. It is a promising water treatment technology.

Assessment of ozone variations and meteorological effects in an urban area in the Mediterranean Coast.

PubMed

Dueñas, C; Fernández, M C; Cañete, S; Carretero, J; Liger, E

2002-11-01

Ozone concentrations are valuable indicators of possible health and environmental impacts. However, they are also used to monitor changes and trends in the sources of both ozone and its precursors. For this purpose, the influence of meteorological variables is a confusing factor. This study presents an analysis of a year of ozone concentrations measured in a coastal Spanish city. Firstly, the aim of this study was to perceive the daily, monthly and seasonal variation patterns of ozone concentrations. Diurnal cycles are presented by season and the fit of the data to a normal distribution is tested. In order to assess ozone behaviour under temperate weather conditions, local meteorological variables (wind direction and speed, temperature, relative humidity, pressure and rainfall) were monitored together with ozone concentrations. The main relationships we could observe in these analyses were then used to obtain a regression equation linking diurnal ozone concentrations in summer with meteorological parameters.

The formation of ozone and UV radiation from high-power pulsed electric discharges

NASA Astrophysics Data System (ADS)

Piskarev, I. M.; Ushkanov, V. A.; Selemir, V. D.; Spirov, G. M.; Malevannaya Pikar', I. A.; Zuimach, E. A.

2008-09-01

High-power electric discharges with pulse energies of from 0.15 J to 4 kJ were studied. The yields of UV photons and ozone were found to be approximately equal, which led us to conclude that discharge conditions under which UV radiation and ozone fully destroyed each other were possible. If ozone formation was suppressed, as when a negative volume charge was created in the spark gap region, the flux of UV photons reached 3 × 1023 photons/(cm2 s).

Atlas of TOMS ozone data collected during the Genesis of Atlantic Lows Experiment (GALE), 1986

NASA Technical Reports Server (NTRS)

Larko, David E.; Uccellini, Louis W.; Krueger, Arlin J.

1986-01-01

Data from the TOMS (Total Ozone Mapping Spectrometer) instrument aboard the Nimbus-7 satellite were collected daily in real time during the GALE (Genesis of Atlantic Lows Experiment) from January 15 through March 15, l986. The TOMS ozone data values were processed into GEMPAK format and transferred from the Goddard Space Flight Center to GALE operations in Raleigh-Durham, NC, in as little as three hours for use, in part, to direct aircraft research flights recording in situ measurements of ozone and water vapor in areas of interest. Once in GEMPAK format, the ozone values were processed into gridded form using the Barnes objective analysis scheme and contour plots of the ozone created. This atlas provides objectively analyzed contour plots of the ozone for each of the sixty days of GALE as well as four-panel presentations of the ozone analysis combined on the basis of GALE Intensive Observing Periods (IOP's).

Evaluating Oil and Gas Speciation Profiles with Factor Analysis of Ambient Volatile Organic Compound Concentrations in the Colorado Front Range

NASA Astrophysics Data System (ADS)

Capps, S.; Paranjothi, G.; Pierce, G. E.; Milford, J. B.

2016-12-01

Increased oil and gas (O&G) development, particularly through the use of hydraulic fracturing, in the Denver-Julesburg Basin (DJB) in Colorado over the last decade has been identified as a source of emissions of air pollutants, which are now included in chemical transport modeling. As one effort to evaluate its impact, ambient concentrations of volatile organic compounds (VOCs) that serve as precursors to ozone formation were measured in an Ozone Precursor Study conducted by the Colorado Department of Public Health and Environment during 2013 and 2014. The study included 6 - 9 a.m. measurements of an extensive suite of ozone-precursor VOCs from a site in an area of intensive O&G development in Platteville, CO, and another site in downtown Denver, CO. To evaluate the influences of urban activity or O&G development on these ambient concentrations, we used the U.S. EPA's Positive Matrix Factorization (PMF) tool. A five-factor PMF solution was selected as providing the best fit to the dataset comprised of VOC measurements for both years and both sites. One PMF factor matches the VOC emissions speciation profile for the flashing gas composition for condensate tanks in the DJB that was developed by the Western Regional Air Partnership for use in chemical transport modeling in the region. The contribution of this factor to individual and total VOC concentrations and ozone production reactivity is evaluated for Platteville and Denver.

Urban airshed modeling of air quality impacts of alternative transportation fuel use in Los Angeles and Atlanta

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

NONE

1997-12-01

The main objective of NREL in supporting this study is to determine the relative air quality impact of the use of compressed natural gas (CNG) as an alternative transportation fuel when compared to low Reid vapor pressure (RVP) gasoline and reformulated gasoline (RFG). A table lists the criteria, air toxic, and greenhouse gas pollutants for which emissions were estimated for the alternative fuel scenarios. Air quality impacts were then estimated by performing photochemical modeling of the alternative fuel scenarios using the Urban Airshed Model Version 6.21 and the Carbon Bond Mechanism Version IV (CBM-IV) (Geary et al., 1988) Using thismore » model, the authors examined the formation and transport of ozone under alternative fuel strategies for motor vehicle transportation sources for the year 2007. Photochemical modeling was performed for modeling domains in Los Angeles, California, and Atlanta, Georgia.« less

Inflammatory Cytokines and White Blood Cell Counts Response to Environmental Levels of Diesel Exhaust and Ozone Inhalation Exposures

EPA Science Inventory

Epidemiological observations of urban inhalation exposures to diesel exhaust (DE) and ozone (O3) have shown pre-clinical cardiopulmonary responses in humans. Identifying the key biological mechanisms that initiate these health bioindicators is difficult due to variability in envi...

Measurements of Criteria Pollutants in Suburban Locations in the Mexico City Metropolitan Area

NASA Astrophysics Data System (ADS)

Fentanes, O.; Sanchez, A.; Garcia, A.; Martinez, A.

2004-12-01

In the town of Santa Ana in the southern part of the Mexico City Metropolitan Area (MCMA) at an approximate height of 370 meters above the Valley of Mexico, a series of criteria pollutants (nitrogen dioxide, ozone, sulfur dioxide, and carbon monoxide) and meteorological parameters (wind speed and direction, temperature and relative humidity) were measured during the MCMA-2003 field campaign during April 2003. Santa Ana is considered a border site, agriculture being the predominant activity. The generated data in Santa Ana was compared with those from two representative atmospheric monitoring stations from the southeast zone (CENICA Supersite) and southwest (Revolucion Station) of Mexico City. The carbon monoxide and ozone concentrations measured in Santa Ana are atypical for a rural area. The sulfur dioxide and nitrogen dioxide concentrations are characteristic of the local activity. The average obtained during the measurement time for carbon monoxide was 0.86 ppm, the presence of the contaminant was within a 0.3 to 1.5 ppm range, 5 to 95 percentile, and does not follow the observed behavior of the monitoring stations that are located inside the urban area, although during the night (10 pm to 6 am) the carbon monoxide in Santa Ana was preset in levels from 0.4 to 1.5 ppm, 5 to 95 percentiles, average 0.92 ppm, above the reported concentrations at Revolucion Station, levels from 0.1 to 1.7 ppm, 5 to 95 percentiles; average 0.72 ppm. The presence of this contaminant can be attributed to transportation and accumulation phenomena. The ozone daytime behavior is similar to the one observed in the CENICA and Revolucion stations, but with a lower magnitude, the daily maximum generally occuring 2 or 3 hours after the urban stations. The one-hour average maximum values were 133 ppb in Santa Ana area and 188 ppb in the city. During the night the average concentrations were 37 ppb in Santa Ana and 17 ppb in the urban area. Nevertheless, the ozone average value in Santa Ana during the study was 49 ppb, slightly higher than the one obtained in the urban area, which was 44 ppb. The presence of this contaminant can be possibly attributed to the transportation and accumulation factors as well as to the low reactivity due to the absence of NOx, as explained in Dommen Josef and Prévôt, S.H. André, 2002, Characterization of the photooxidant formation in the metropolitan area of Milan from aircraft measurements, Journal of Geophysical Research, 107 (D22): 8197, doi: 10.1029/2000JD000283.

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.

Characterizations of volatile organic compounds (VOCs) from vehicular emissions at roadside environment: The first comprehensive study in Northwestern China

NASA Astrophysics Data System (ADS)

Li, Bowei; Ho, Steven Sai Hang; Xue, Yonggang; Huang, Yu; Wang, Liqin; Cheng, Yan; Dai, Wenting; Zhong, Haobin; Cao, Junji; Lee, Shuncheng

2017-07-01

Vehicular emission (VE) is one of the important anthropogenic sources for ground-level volatile organic compounds (VOCs) in both urban and suburban areas. A first comprehensive campaign was conducted at an urban roadside in Xi'an, China in summer, 2016. A total of 57 VOCs, as known as critical surface ozone (O3) precursors, and other trace gases were measured simultaneously during the sampling period. Iso-pentane, a tracer of gasoline evaporation, was the most abundant VOC in the roadside samples, followed by isobutane and benzene, attributed to the largest composition (∼70%) of gasoline-fueled vehicles on the road. The molar ratio of toluene/benzene (T/B) in our study (0.36) is far lower than the range reported in other cities, indicating the stronger contributions from diesel emissions. The results of source apportionment achieved with positive matrix factorization (PMF) receptor model were highly consistent with the vehicles compositions, strongly evidenced that the precise characterization of the VE sources from those marker species. The degrees of individual compound contributed to O3 production were weighed by ozone formation potential (OFP). Propylene (20%), 1-butene (11%) and iso-pentane(10%) were the top three contributors at the roadside. The information of this study complements the VOCs database regarding to the VE sources in Northwestern China.

A survey of valleys and basins of the western United States for the capacity to produce winter ozone.

PubMed

Mansfield, Marc L; Hall, Courtney F

2018-04-18

High winter ozone in the Uintah Basin, Utah, and the Upper Green River Basin, Wyoming, occurs because of the confluence of three separate factors: (1) extensive oil or natural gas production, (2) topography conducive to strong multiple-day thermal inversions, and (3) snow cover. We surveyed 13 basins and valleys in the western United States for the existence and magnitude of these factors. Seven of the basins, because winter ozone measurements were available, were assigned to four different behavioral classes. Based on similarities among the basins, the remaining six were also given a tentative assignment. Two classes (1 and 2) correspond to basins with high ozone because all three factors just listed are present at sufficient magnitude. Class 3 corresponds to rural basins with ozone at background levels, and occurs because at least one of the three factors is weak or absent. Class 4 corresponds to ozone below background levels, and occurs, for example, in urban basins where emissions scavenge ozone. All three factors are present in the Wind River Basin, Wyoming, but compared to the Uintah or the Upper Green Basins, it has only moderate oil and gas production and is assigned to class 3. We predict that the Wind River Basin, as well as other class 3 basins that have inversions and snow cover, would transition from background (class 3) to high ozone behavior (class 1 or 2) if oil or gas production were to intensify, or to class 4 (low winter ozone) if they were to become urban. High ozone concentrations in winter only occur in basins or valleys that have an active oil and natural gas production industry, multiple-day thermal inversions, and snow cover, and have only been documented in two basins worldwide. We have examined a number of other candidate basins in the western United States and conclude that these factors are either absent or too weak to produce high winter ozone. This study illustrates how strong each factor needs to be before winter ozone can be expected, and can be used by planners and regulators to foresee the development of winter ozone problems.

Air Quality in the Puebla-Tlaxcala Airshed in Mexico during April 2009

NASA Astrophysics Data System (ADS)

Ruiz Suarez, L. G.; Torres Jardón, R.; Torres Jaramillo, J. A.; Barrera, H.; Castro, T.; Mar Morales, B. E.; García Reynoso, J. A.; Molina, L. T.

2012-04-01

East of the Mexico Megacity, is the metropolitan area of Puebla-Tlaxcala which is reproducing the same patterns of urban sprawl as in the Mexico City Metropolitan Area. Is an area of high industrial density, the fragmented urban sprawl boost the use of particular cars in detrimental of public transport use. Emissions inventories reflect this fact; they also show a considerable use of biomass energy in households and small using a set of industries and service business. In April 2009 we carried out a preliminary field campaign in the basin, we deployed three mobile units, one in the north, in a site connecting with the valley of Mexico basin, one in the south where it may connect with the Cuautla-Cuernavaca Airshed and one in a receptor site to the Puebla Metropolitan Area. In addition to the available data from local air quality network within the City of Puebla. Analysis of the 2009 data show a complex flow pattern induced by the Popocateptl and Iztaccihuatl volcanoes to the west and La Malinche volcano to the east. Excess NOx emissions in the urban and industrial core lead to very low ozone levels within but high ozone concentrations are observed in the peri-urban and rural areas, exceeding the Mexican Air Quality Standards. In our presentation we will describe and explain these observations and will describe a field campaign to be carried out in March-April 2012 aiming to better document the air quality in the Puebla-Tlaxcala Airshed. Hybrid observation-model maps for ozone critical levels show the population exposed to exeedences to the official standards. AOT40 maps also show that crops and forests in the region are exposed to unhealthy ozone levels. These results add to those from MILAGRO and CARIEM field campaigns on the regional scale of the air quality issues in central Mexico. A point is made on the need to update the Mexicp Air Quality Standard for ozone.

Photo-chemical transport modelling of tropospheric ozone: A review

NASA Astrophysics Data System (ADS)

Sharma, Sumit; Sharma, Prateek; Khare, Mukesh

2017-06-01

Ground level ozone (GLO), a secondary pollutant having adverse impact on human health, ecology, and agricultural productivity, apart from being a major contributor to global warming, has been a subject matter of several studies. In order to identify appropriate strategies to control GLO levels, accurate assessment and prediction is essential, for which elaborate simulation and modelling is required. Several studies have been undertaken in the past to simulate GLO levels at different scales and for various applications. It is important to evaluate these studies, widely spread over in literature. This paper aims to critically review various studies that have been undertaken, especially in the past 15 years (2000-15) to model GLO. The review has been done of the studies that range over different spatial scales - urban to regional and continental to global. It also includes a review of performance evaluation and sensitivity analysis of photo-chemical transport models in order to assess the extent of application of these models and their predictive capability. The review indicates following major findings: (a) models tend to over-estimate the night-time GLO concentrations due to limited titration of GLO with NO within the model; (b) dominance of contribution from far-off regional sources to average ozone concentration in the urban region and higher contribution of local sources during days of high ozone episodes; requiring strategies for controlling precursor emissions at both regional and local scales; (c) greater influence of NOx over VOC in export of ozone from urban regions due to shifting of urban plumes from VOC-sensitive regime to NOx-sensitive as they move out from city centres to neighbouring rural regions; (d) models with finer resolution inputs perform better to a certain extent, however, further improvement in resolutions (beyond 10 km) did not show improvement always; (e) future projections show an increase in GLO concentrations mainly due to rise in temperatures and biogenic VOC emissions.

Resolving uncertainties in the urban air quality, climate, and vegetation nexus through citizen science, satellite imagery, and atmospheric modeling

NASA Astrophysics Data System (ADS)

Jenerette, D.; Wang, J.; Chandler, M.; Ripplinger, J.; Koutzoukis, S.; Ge, C.; Castro Garcia, L.; Kucera, D.; Liu, X.

2017-12-01

Large uncertainties remain in identifying the distribution of urban air quality and temperature risks across neighborhood to regional scales. Nevertheless, many cities are actively expanding vegetation with an expectation to moderate both climate and air quality risks. We address these uncertainties through an integrated analysis of satellite data, atmospheric modeling, and in-situ environmental sensor networks maintained by citizen scientists. During the summer of 2017 we deployed neighborhood-scale networks of air temperature and ozone sensors through three campaigns across urbanized southern California. During each five-week campaign we deployed six sensor nodes that included an EPA federal equivalent method ozone sensor and a suite of meteorological sensors. Each node was further embedded in a network of 100 air temperature sensors that combined a randomized design developed by the research team and a design co-created by citizen scientists. Between 20 and 60 citizen scientists were recruited for each campaign, with local partners supporting outreach and training to ensure consistent deployment and data gathering. We observed substantial variation in both temperature and ozone concentrations at scales less than 4km, whole city, and the broader southern California region. At the whole city scale the average spatial variation with our ozone sensor network just for city of Long Beach was 26% of the mean, while corresponding variation in air temperature was only 7% of the mean. These findings contrast with atmospheric model estimates of variation at the regional scale of 11% and 1%. Our results show the magnitude of fine-scale variation underestimated by current models and may also suggest scaling functions that can connect neighborhood and regional variation in both ozone and temperature risks in southern California. By engaging citizen science with high quality sensors, satellite data, and real-time forecasting, our results help identify magnitudes of climate and air quality risk variation across scales and can guide individual decisions and urban policies surrounding vegetation to moderate these risks.

Ozone profiles from tethered balloon measurements in an urban plume experiment

NASA Technical Reports Server (NTRS)

Youngbluth, O., Jr.; Storey, R. W.; Clendenin, C. G.; Jones, S.; Leighty, B.

1981-01-01

NASA Langley Research Center used two tethered balloon systems to measure ozone in the general area of Norfolk, Va. The large balloon system which has an altitude range of 1,500 meters was located at Wallops Island, Va., and the smaller balloon which has an altitude range of 900 meters was located at Chesapeake, Va. Each balloon system measured ozone, temperature, humidity, wind speed, and wind direction from ground to its maximum altitude. From these measurements and from the location of the balloon sites, areas of ozone generation and ozone transport may be inferred. The measurements which were taken during August 1979 are discussed as well as the measurement techniques.

Large-scale pollution of the atmosphere over the remote Atlantic Ocean: Evidence from Bermuda

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

Dickerson, R.R.; Doddridge, B.G.; Kelley, P.

1995-05-20

Ozone acts as a greenhouse gas and controls much of the oxidizing capacity of the atmosphere. Photochemical production of ozone in urban areas (smog) is a serious environmental problem, but how far this process extends on regional or global scales remains a major unanswered question in atmospheric science. In summer, Bermuda basks in pristine marine air, but in spring, episodes of high ozone are common. From meteorological analyses and observation of ozone, carbon monoxide, and reactive nitrogen compounds, the authors conclude that half or more of the excess ozone in Bermuda originates from air pollution over eastern North America. 50more » refs., 7 figs., 2 tabs.« less

Past successes and future challenges: Improving the urban environment

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

Gade, M.

1994-12-31

The author discusses issues related to the Chicago urban environment from her perspective in the Illinois Environmental Protection Agency. Understanding of the ozone air pollution problem in the Chicago area has undergone significant changes in the past three years, and there is still more to be understood about the complex factors which contribute to ozone pollution over urban areas such as Chicago. Ability to address these problems to present clean air standards is not in hand at present. The author asserts that information, and the ability of governmental agencies to ingest and respond to that information in a timely mannermore » is a key to improvement of the environment in urban areas in reasonable time spans. In addition cost and price information on environmental control and protection needs to be more clearly presented to the people so they can understand the difficult choices which must be made in addressing these environmental problems.« less

Air quality modeling for the urban Jackson, Mississippi Region using a high resolution WRF/Chem model.

PubMed

Yerramilli, Anjaneyulu; Dodla, Venkata B; Desamsetti, Srinivas; Challa, Srinivas V; Young, John H; Patrick, Chuck; Baham, Julius M; Hughes, Robert L; Yerramilli, Sudha; Tuluri, Francis; Hardy, Mark G; Swanier, Shelton J

2011-06-01

In this study, an attempt was made to simulate the air quality with reference to ozone over the Jackson (Mississippi) region using an online WRF/Chem (Weather Research and Forecasting-Chemistry) model. The WRF/Chem model has the advantages of the integration of the meteorological and chemistry modules with the same computational grid and same physical parameterizations and includes the feedback between the atmospheric chemistry and physical processes. The model was designed to have three nested domains with the inner-most domain covering the study region with a resolution of 1 km. The model was integrated for 48 hours continuously starting from 0000 UTC of 6 June 2006 and the evolution of surface ozone and other precursor pollutants were analyzed. The model simulated atmospheric flow fields and distributions of NO2 and O3 were evaluated for each of the three different time periods. The GIS based spatial distribution maps for ozone, its precursors NO, NO2, CO and HONO and the back trajectories indicate that all the mobile sources in Jackson, Ridgeland and Madison contributing significantly for their formation. The present study demonstrates the applicability of WRF/Chem model to generate quantitative information at high spatial and temporal resolution for the development of decision support systems for air quality regulatory agencies and health administrators.

Trend and variability of atmospheric ozone over middle Indo-Gangetic Plain: impacts of seasonality and precursor gases.

PubMed

Shukla, K; Srivastava, Prashant K; Banerjee, T; Aneja, Viney P

2017-01-01

Ozone dynamics in two urban background atmospheres over middle Indo-Gangetic Plain (IGP) were studied in two contexts: total columnar and ground-level ozone. In terms of total columnar ozone (TCO), emphases were made to compare satellite-based retrieval with ground-based observation and existing trend in decadal and seasonal variation was also identified. Both satellite-retrieved (Aura Ozone Monitoring Instrument-Differential Optical Absorption Spectroscopy (OMI-DOAS)) and ground-based observations (IMD-O 3 ) revealed satisfying agreement with OMI-DOAS observation over predicting TCO with a positive bias of 7.24 % under all-sky conditions. Minor variation between daily daytime (r = 0.54; R 2  = 29 %; n = 275) and satellite overpass time-averaged TCO (r = 0.58; R 2  = 34 %; n = 208) was also recognized. A consistent and clear seasonal trend in columnar ozone (2005-2015) was noted with summertime (March-June) maxima (Varanasi, 290.9 ± 8.8; Lucknow, 295.6 ± 9.5 DU) and wintertime (December-February) minima (Varanasi, 257.4 ± 10.1; Lucknow, 258.8 ± 8.8 DU). Seasonal trend decomposition based on locally weighted regression smoothing technique identified marginally decreasing trend (Varanasi, 0.0084; Lucknow, 0.0096 DU year -1 ) especially due to reduction in monsoon time minima and summertime maxima. In continuation to TCO, variation in ground-level ozone in terms of seasonality and precursor gases were also analysed from September 2014 to August 2015. Both stations registered similar pattern of variation with Lucknow representing slightly higher annual mean (44.3 ± 30.6; range, 1.5-309.1 μg/m 3 ) over Varanasi (38.5 ± 17.7; range, 4.9-104.2 μg/m 3 ). Variation in ground-level ozone was further explained in terms water vapour, atmospheric boundary layer height and solar radiation. Ambient water vapour content was found to associate negatively (r = -0.28, n = 284) with ground-level ozone with considerable seasonal variation in Varanasi. Implication of solar radiation on formation of ground-level ozone was overall positive (Varanasi, 0.60; Lucknow, 0.26), while season-specific association was recorded in case of atmospheric boundary layer.

Influence of Urbanicity and County Characteristics on the ...

EPA Pesticide Factsheets

Background: Air pollution epidemiology studies, often conducted in large metropolitan areas due to proximity to regulatory monitors, are limited in their ability to examine potential associations between air pollution exposures and health effects in rural locations. Methods: In a time-stratified case-crossover framework, we examined associations between asthma emergency department (ED) visits in North Carolina (2006-2008) collected by a surveillance system, and short-term ozone exposures using predicted concentrations from the Community Multiscale Air Quality (CMAQ) model. Associations were estimated by county groupings based on four urbanicity classifications (representative of county size and urban proximity) and county health. Results: Ozone was associated with asthma ED visits in all-year and warm season (April-October) analyses [Odds Ratio (OR) =1.019; 95% CI: 0.998, 1.040; OR=1.020; 95% CI: 0.997, 1.044, respectively, for a 20 ppb increase in lag 0-2 days ozone]. The association was strongest in Less Urbanized counties, with no evidence of a positive association in Rural counties. Associations were similar when adjusted for fine particulate matter in copolluant models. Associations were stronger for children (5-17 years of age) compared with other age groups, and for individuals living in counties with poorer health status compared with counties that had the highest health rankings, although estimated associations for these subgroups were imprecise. Conclu

Modeling the Dynamic Change of Air Quality and its Response to Emission Trends

NASA Astrophysics Data System (ADS)

Zhou, Wei

This thesis focuses on evaluating atmospheric chemistry and transport models' capability in simulating the chemistry and dynamics of power plant plumes, evaluating their strengths and weaknesses in predicting air quality trends at regional scales, and exploring air quality trends in an urban area. First, the Community Mutlti-scale Air Quality (CMAQ) model is applied to simulate the physical and chemical evolution of power plant plumes (PPPs) during the second Texas Air Quality Study (TexAQS) in 2006. SO2 and NOy were observed to be rapidly removed from PPPs on cloudy days but not on cloud-free days, indicating efficient aqueous processing of these compounds in clouds, while the model fails to capture the rapid loss of SO2 and NOy in some plumes on the cloudy day. Adjustments to cloud liquid water content (QC) and the default metal concentrations in the cloud module could explain some of the SO 2 loss while NOy in the model was insensitive to QC. Second, CMAQ is applied to simulate the ozone (O3) change after the NO x SIP Call and mobile emission controls in the eastern U.S. from 2002 to 2006. Observed downward changes in 8-hour O3 concentrations in the NOx SIP Call region were under-predicted by 26%--66%. The under-prediction in O3 improvements could be alleviated by 5%--31% by constraining NOx emissions in each year based on observed NOx concentrations while temperature biases or uncertainties in chemical reactions had minor impact on simulated O3 trends. Third, changes in ozone production in the Houston area is assessed with airborne measurements from TexAQS 2000 and 2006. Simultaneous declines in nitrogen oxides (NOx=NO+NO2) and highly reactive Volatile Organic Compounds (HRVOCs) were observed in the Houston Ship Channel (HSC). The reduction in HRVOCs led to the decline in total radical concentration by 20-50%. Rapid ozone production rates in the Houston area declined by 40-50% from 2000 to 2006, to which the reduction in NOx and HRVOCs had the similar contribution. Houston petrochemical and urban plumes largely remained in a strong VOC-sensitive regime of ozone formation and maintained high Ozone Production Efficiency (OPE: 5-15).

NASA participation in the 1980 Persistent Elevated Pollution Episode/Northeast Regional Oxidant Study (PEPE/NROS) Project: Operational aspects

NASA Technical Reports Server (NTRS)

Maddrea, G. L., Jr.; Bendura, R. J.

1981-01-01

A field experiment designed to further understand the formation and transport of visibility reducing aerosols and to characterize regional scale air masses and urban plumes is described. Measurements were made primarily in the Ohio River Valley region. The NASA participation included obtaining measurements for the determination of mixing layer height and ozone profiles by using airborne remote sensor systems such as the ultraviolet differential absorption lidar, the high spectral resolution lidar, and the laser absorption spectrometer. Other NASA systems included the microwave atmospheric remote sensor, tethered balloons, an in situ measurements aircraft, and several photometer/transmissiometer systems.

Intercontinental Transport of Tropical Ozone from Biomass Burning: Views from Satellite and SHADOZ (Southern Hemisphere Additional Ozonesondes) Soundings

NASA Technical Reports Server (NTRS)

Thompson, Anne M.

2003-01-01

The atmospheric impacts of tropical fires came to attention in the 1970's and there has been interest in the connection between these fires and ozone since about 1980. Photochemically reactive gases released by fires (e.g. NO, CO, volatile organic carbon) interact as they do in an urban environment to form ozone. Tropical meteorology also plays a part in tropospheric ozone distributions in the tropics - through large-scale circulation, deep convection, regional phenomena (West African and Asian monsoon) - and variations associated with El-Nino and the Quasi- biennial Oscillation have been reported. This Poster is an overview of observations, taken from satellite and from ozone soundings, that illustrate regional influences and intercontinental-range ozone transport in the tropics.

Formation of assimilable organic carbon during oxidation of natural waters with ozone, chlorine dioxide, chlorine, permanganate, and ferrate.

PubMed

Ramseier, Maaike K; Peter, Andreas; Traber, Jacqueline; von Gunten, Urs

2011-02-01

Five oxidants, ozone, chlorine dioxide, chlorine, permanganate, and ferrate were studied with regard to the formation of assimilable organic carbon (AOC) and oxalate in absence and presence of cyanobacteria in lake water matrices. Ozone and ferrate formed significant amounts of AOC, i.e. more than 100 μg/L AOC were formed with 4.6 mg/L ozone and ferrate in water with 3.8 mg/L dissolved organic carbon. In the same water samples chlorine dioxide, chlorine, and permanganate produced no or only limited AOC. When cyanobacterial cells (Aphanizomenon gracile) were added to the water, an AOC increase was detected with ozone, permanganate, and ferrate, probably due to cell lysis. This was confirmed by the increase of extracellular geosmin, a substance found in the selected cyanobacterial cells. AOC formation by chlorine and chlorine dioxide was not affected by the presence of the cells. The formation of oxalate upon oxidation was found to be a linear function of the oxidant consumption for all five oxidants. The following molar yields were measured in three different water matrices based on oxidant consumed: 2.4-4.4% for ozone, 1.0-2.8% for chlorine dioxide and chlorine, 1.1-1.2% for ferrate, and 11-16% for permanganate. Furthermore, oxalate was formed in similar concentrations as trihalomethanes during chlorination (yield ∼ 1% based on chlorine consumed). Oxalate formation kinetics and stoichiometry did not correspond to the AOC formation. Therefore, oxalate cannot be used as a surrogate for AOC formation during oxidative water treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Review of plants to mitigate particulate matter, ozone as well as nitrogen dioxide air pollutants and applicable recommendations for green roofs in Montreal, Quebec.

PubMed

Gourdji, Shannon

2018-05-28

In urbanized regions with expansive impervious surfaces and often low vegetation cover, air pollution due to motor vehicles and other combustion sources, is a problem. The poor air quality days in Montreal, Quebec are mainly due to fine particulate matter and ozone. Businesses using wood ovens are a source of particulates. Careful vegetation selection and increased green roof usage can improve air quality. This paper reviews different green roofs and the capability of plants in particulate matter (PM), ozone (O 3 ) as well as nitrogen dioxide (NO 2 ) level reductions. Both the recommended green roof category and plants to reduce these pollutants in Montreal's zone 5 hardiness region are provided. Green roofs with larger vegetation including shrubs and trees, or intensive green roofs, remove air pollutants to a greater extent and are advisable to implement on existing, retrofitted or new buildings. PM is most effectively captured by pines. The small Pinus strobus 'Nana', Pinus mugho var. pumilio, Pinus mugho 'Slowmound' and Pinus pumila 'Dwarf Blue' are good candidates for intensive green roofs. Drought tolerant, deciduous broadleaved trees with low biogenic volatile organic compound emissions including Japanese Maple or Acer palmatum 'Shaina' and 'Mikawa-Yatsubusa' are options to reduce O 3 levels. Magnolias are tolerant to NO 2 and it is important in their metabolic pathways. The small cold-tolerant Magnolia 'Genie' is a good option to remove NO 2 in urban settings and to indirectly reduce O 3 formation. Given the emissions by Montreal businesses' wood ovens, calculations performed based on their respective complex roof areas obtained via Google Earth Pro indicates 88% Pinus mugho var. pumilio roof coverage can annually remove 92.37 kg of PM 10 of which 35.10 kg is PM 2.5 . The removal rates are 4.00 g/m 2 and 1.52 g/m 2 for PM 10 and PM 2.5 , respectively. This paper provides insight to addressing air pollution through urban rooftop greening. Copyright © 2018 Elsevier Ltd. All rights reserved.

Children's Models of the Ozone Layer and Ozone Depletion.

ERIC Educational Resources Information Center

Christidou, Vasilia; Koulaidis, Vasilis

1996-01-01

The views of 40 primary students on ozone and its depletion were recorded through individual, semi-structured interviews. The data analysis resulted in the formation of a limited number of models concerning the distribution and role of ozone in the atmosphere, the depletion process, and the consequences of ozone depletion. Identifies five target…

Photochemical production of ozone in the upper troposphere in association with cumulus convection over Indonesia

NASA Astrophysics Data System (ADS)

Kita, K.; Kawakami, S.; Miyazaki, Y.; Higashi, Y.; Kondo, Y.; Nishi, N.; Koike, M.; Blake, D. R.; Machida, T.; Sano, T.; Hu, W.; Ko, M.; Ogawa, T.

2002-02-01

The Biomass Burning and Lightning Experiment phase A (BIBLE-A) aircraft observation campaign was conducted from 24 September to 10 October 1998, during a La Niña period. During this campaign, distributions of ozone and its precursors (NO, CO, and nonmethane hydrocarbons (NMHCs)) were observed over the tropical Pacific Ocean, Indonesia, and northern Australia. Mixing ratios of ozone and its precursors were very low at altitudes between 0 and 13.5 km over the tropical Pacific Ocean. The mixing ratios of ozone precursors above 8 km over Indonesia were often significantly higher than those over the tropical Pacific Ocean, even though the prevailing easterlies carried the air from the tropical Pacific Ocean to over Indonesia within several days. For example, median NO and CO mixing ratios in the upper troposphere were 12 parts per trillion (pptv) and 72 parts per billion (ppbv) over the tropical Pacific Ocean and were 83 pptv and 85 ppbv over western Indonesia, respectively. Meteorological analyses and high ethene (C2H4) mixing ratios indicate that the increase of the ozone precursors was caused by active convection over Indonesia through upward transport of polluted air, mixing, and lightning all within the few days prior to observation. Sources of ozone precursors are discussed by comparing correlations of some NMHCs and CH3Cl concentrations with CO between the lower and upper troposphere. Biomass burning in Indonesia was nearly inactive during BIBLE-A and was not a dominant source of the ozone precursors, but urban pollution and lightning contributed importantly to their increases. The increase in ozone precursors raised net ozone production rates over western Indonesia in the upper troposphere, as shown by a photochemical model calculation. However, the ozone mixing ratio (˜20 ppbv) did not increase significantly over Indonesia because photochemical production of ozone did not have sufficient time since the augmentation of ozone precursors. Backward trajectories show that many air masses sampled over the ocean south of Indonesia and over northern Australia passed over western Indonesia 4-9 days prior to being measured. In these air masses the mixing ratios of ozone precursors, except for short-lived species, were similar to those over western Indonesia. In contrast, the ozone mixing ratio was higher by about 10 ppbv than that over Indonesia, indicating that photochemical production of ozone occurred during transport from Indonesia. The average rate of ozone increase (1.8 ppbv/d) during this transport is similar to the net ozone formation rate calculated by the photochemical model. This study shows that active convection over Indonesia carried polluted air upward from the surface and had a discernable influence on the distribution of ozone in the upper troposphere over the Indian Ocean, northern Australia, and the south subtropical Pacific Ocean, combined with NO production by lightning.

Photochemical production of ozone in the upper troposphere in association with cumulus convection over Indonesia

NASA Astrophysics Data System (ADS)

Kita, K.; Kawakami, S.; Miyazaki, Y.; Higashi, Y.; Kondo, Y.; Nishi, N.; Koike, M.; Blake, D. R.; Machida, T.; Sano, T.; Hu, W.; Ko, M.; Ogawa, T.

2003-02-01

The Biomass Burning and Lightning Experiment phase A (BIBLE-A) aircraft observation campaign was conducted from 24 September to 10 October 1998, during a La Niña period. During this campaign, distributions of ozone and its precursors (NO, CO, and nonmethane hydrocarbons (NMHCs)) were observed over the tropical Pacific Ocean, Indonesia, and northern Australia. Mixing ratios of ozone and its precursors were very low at altitudes between 0 and 13.5 km over the tropical Pacific Ocean. The mixing ratios of ozone precursors above 8 km over Indonesia were often significantly higher than those over the tropical Pacific Ocean, even though the prevailing easterlies carried the air from the tropical Pacific Ocean to over Indonesia within several days. For example, median NO and CO mixing ratios in the upper troposphere were 12 parts per trillion (pptv) and 72 parts per billion (ppbv) over the tropical Pacific Ocean and were 83 pptv and 85 ppbv over western Indonesia, respectively. Meteorological analyses and high ethene (C2H4) mixing ratios indicate that the increase of the ozone precursors was caused by active convection over Indonesia through upward transport of polluted air, mixing, and lightning all within the few days prior to observation. Sources of ozone precursors are discussed by comparing correlations of some NMHCs and CH3Cl concentrations with CO between the lower and upper troposphere. Biomass burning in Indonesia was nearly inactive during BIBLE-A and was not a dominant source of the ozone precursors, but urban pollution and lightning contributed importantly to their increases. The increase in ozone precursors raised net ozone production rates over western Indonesia in the upper troposphere, as shown by a photochemical model calculation. However, the ozone mixing ratio (~20 ppbv) did not increase significantly over Indonesia because photochemical production of ozone did not have sufficient time since the augmentation of ozone precursors. Backward trajectories show that many air masses sampled over the ocean south of Indonesia and over northern Australia passed over western Indonesia 4-9 days prior to being measured. In these air masses the mixing ratios of ozone precursors, except for short-lived species, were similar to those over western Indonesia. In contrast, the ozone mixing ratio was higher by about 10 ppbv than that over Indonesia, indicating that photochemical production of ozone occurred during transport from Indonesia. The average rate of ozone increase (1.8 ppbv/d) during this transport is similar to the net ozone formation rate calculated by the photochemical model. This study shows that active convection over Indonesia carried polluted air upward from the surface and had a discernable influence on the distribution of ozone in the upper troposphere over the Indian Ocean, northern Australia, and the south subtropical Pacific Ocean, combined with NO production by lightning.

Comparison of measured ozone in southeastern Virginia with computer predictions from a photochemical model

NASA Technical Reports Server (NTRS)

Wakelyn, N. T.; Gregory, G. L.

1980-01-01

Data for one day of the 1977 southeastern Virginia urban plume study are compared with computer predictions from a traveling air parcel model using a contemporary photochemical mechanism with a minimal description of nonmethane hydrocarbon (NMHC) constitution and chemistry. With measured initial NOx and O3 concentrations and a current separate estimate of urban source loading input to the model, and for a variation of initial NMHC over a reasonable range, an ozone increase over the day is predicted from the photochemical simulation which is consistent with the flight path averaged airborne data.

Air quality and urban form in U.S. urban areas: evidence from regulatory monitors.

PubMed

Clark, Lara P; Millet, Dylan B; Marshall, Julian D

2011-08-15

The layout of an urban area can impact air pollution via changes in emissions and their spatial distribution. Here, we explore relationships between air quality and urban form based on cross-sectional observations for 111 U.S. urban areas. We employ stepwise linear regression to quantify how long-term population-weighted outdoor concentrations of ozone, fine particulate matter (PM(2.5)), and other criteria pollutants measured by the U.S. Environmental Protection Agency depend on urban form, climate, transportation, city size, income, and region. Aspects of urban form evaluated here include city shape, road density, jobs-housing imbalance, population density, and population centrality. We find that population density is associated with higher population-weighted PM(2.5) concentrations (p < 0.01); population centrality is associated with lower population-weighted ozone and PM(2.5) concentrations (p < 0.01); and transit supply is associated with lower population-weighted PM(2.5) concentrations (p < 0.1). Among pollutants, interquartile range changes in urban form variables are associated with 4%-12% changes in population-weighted concentrations-amounts comparable, for example, to changes in climatic factors. Our empirical findings are consistent with prior modeling research and suggest that urban form could potentially play a modest but important role in achieving (or not achieving) long-term air quality goals.

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.

Isotope Effect in Ozone Formation: Assessing the Relationship Between Photon Energy and Stabilization

NASA Astrophysics Data System (ADS)

Gardner, D. A.; Chakraborty, S.; Thiemens, M. H.

2016-12-01

While it has been found that the isotopic fractionation of oxygen during processes such as evaporation or precipitation happens mass-dependently (i.e. δ17O = 0.52δ18O), it was discovered in the 1980's that during ozone (O3) formation, fractionation occurs mass-independently (i.e. δ17O = δ18O). The purpose of this series of photolysis experiments was to assess the relationship between incoming photon energy and anomalous oxygen enrichment during the formation of ozone from molecular oxygen, a topic that has not yet been explored in detail, to our knowledge. A UV lamp emitting wavelengths of 184.9 and 253.7 nm was used to photolyze molecular oxygen in a vacuum chamber to form ozone. The ozone was separated from unreacted oxygen by trapping ozone with liquid nitrogen in the reaction chamber finger. After the untrapped oxygen was evacuated, the ozone was collected in a sample tube with molecular sieve, which allows the ozone to break down to molecular oxygen. In these experiments, mass-spectroscopy was performed on molecular oxygen to measure the isotopic composition (δ17O and δ18O). A limited number of experiments were performed using two different collection methods: collection immediately following formation and collection at the end of photon exposure, allowing a certain amount of ozone to dissociate and recycle. We compared the enrichments of against in ozone from the two above mentioned cases. In the former case, the enrichment in δ17O and δ18O follow a linear relationship of 0.92 (normalized to starting composition), consistent with literature data. Whereas for the latter case, the measured slope value was 0.83. The individual δ17O and δ18O values were also relatively higher compared to the first case. Differences for these two cases may arise due to the additional contribution from ozone dissociation (follow a nearly mass-dependent slope, i.e. 0.5) in the second case. More experiments are underway in an attempt to understand the stabilization step of ozone formation (i.e. energy dependence) and associated isotope effect. Results from different photon energies (e.g. 116.5, 121.6, and 123.6 nm) from different UV lamps will be presented in the meeting.

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.

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

Newchurch, M.

The objectives of this research were to: (1) examine empirically the aerosol effect on Umkehr ozone profiles using SAGE II aerosol and ozone data; (2) examine theoretically the aerosol effect on Umkehr ozone profiles; (3) examine the differences between SAGE II ozone profiles and both old- and new-format Umkehr ozone profiles for ozone-trend information; (4) reexamine SAGE I-Umkehr ozone differences with the most recent version of SAGE I data; and (5) contribute to the SAGE II science team.

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.

Products of BVOC oxidation: ozone and organic aerosols

NASA Astrophysics Data System (ADS)

Wildt, Jürgen; Andres, Stefanie; Carriero, Giulia; Ehn, Mikael; Fares, Silvano; Hoffmann, Thorsten; Hacker, Lina; Kiendler-Scharr, Astrid; Kleist, Einhard; Paoletti, Elena; Pullinen, Iida; Rohrer, Franz; Rudich, Yinon; Springer, Monika; Tillmann, Ralf; Wahner, Andreas; Wu, Cheng; Mentel, Thomas

2015-04-01

Biogenic Volatile Organic Compounds (BVOC) are important precursors in photochemical O3 and secondary organic aerosol (SOA) formation. We conducted a series of laboratory experiments with OH-induced oxidation of monoterpenes to elucidate pathways and efficiencies of O3 and SOA formation. At high NOx conditions ([BVOC] / [NOx] < 7 ppbC / ppb) photochemical ozone formation was observed. For -pinene as individual BVOC as well as for the monoterpene mixes emitted from different plant species we observed increasing ozone formation with increasing [NOX]. Between 2 and 3 O3-molecules were formed from 1 monoterpene when ozone formation was BVOC limited. Under such high NOX conditions, new particle formation was suppressed. Increasing [BVOC] / [NOX] ratios caused increasing efficiency of new particle formation indicating that peroxy radicals are the key intermediates in both, photochemical ozone- and new particle formation. The classical chemistry of peroxy radicals is well established (e.g. Master Chemical Mechanism). Peroxy radicals are produced by addition of molecular oxygen to the alkyl radical formed after OH attack at the BVOC. They either react with NO which leads to ozone formation or they react with other peroxy radicals and form chemically stable products (hydroperoxides, alkoholes and ketones). Much less knowledge exists on such reactions for Highly Oxidized Peroxy Radicals, (HOPR). Such HOPR were observed during ozonolysis of several volatiles and, in case of monoterpenes as precursors, they can contain more than 12 Oxygen atoms (Mentel et al., 2015). Although the OH-initiated formation of HOPR is yet not fully understood, their basic gas phase reactions seem to follow classical photochemical rules. In reactions with NO they can act as precursor for O3 and in reactions with other HOPR or with classical less oxidized peroxy radicals they can form highly oxidized stable products and alkoxy radicals. In addition, HOPR-HOPR reactions lead to the formation of dimers that, in case of monoterpenes as reactants, consist of a skeleton with 20 carbon atoms. These dimers seem to play a major role in new particle formation and their existence may explain the observations of Wildt et al. (2014) who found power law dependence with an exponent approaching -2 between new particle formation and ozone formation. The monomer products of HOPR-HOPR reactions play a dominant role in SOA mass formation because their vapour pressures are low enough to allow condensation on pre-existing particulate matter (Ehn et al., 2014). Furthermore, the minor impacts of NOX on particle mass formation (Wildt et al., 2014) are explainable by similar yields of alkoxy radicals in HOPR-HOPR and HOPR-NO reactions, respectively.

Heat Waves, Urban Vegetation, and Air Pollution

NASA Astrophysics Data System (ADS)

Churkina, G.; Grote, R.; Butler, T. M.

2014-12-01

Fast-track programs to plant millions of trees in cities around the world aim at the reduction of summer temperatures, increase carbon storage, storm water control, provision of space for recreation, as well as poverty alleviation. Although these multiple benefits speak positively for urban greening programs, the programs do not take into account how close human and natural systems are coupled in urban areas. Elevated temperatures together with anthropogenic emissions of air and water pollutants distinguish the urban system. Urban and sub-urban vegetation responds to ambient changes and reacts with pollutants. Neglecting the existence of this coupling may lead to unforeseen drawbacks of urban greening programs. The potential for emissions from urban vegetation combined with anthropogenic emissions to produce ozone has long been recognized. This potential increases under rising temperatures. Here we investigate how global change induced heat waves affect emissions of volatile organic compounds (VOC) from urban vegetation and corresponding ground-level ozone levels. We also quantify other ecosystem services provided by urban vegetation (e.g., cooling and carbon storage) and their sensitivity to climate change. In this study we use Weather Research and Forecasting Model with coupled atmospheric chemistry (WRF-CHEM) to quantify these feedbacks in Berlin, Germany during the heat waves in 2003 and 2006. We highlight the importance of the vegetation for urban areas under changing climate and discuss associated tradeoffs.

Urban Landscape Characterization Using Remote Sensing Data For Input into Air Quality Modeling

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Estes, Maurice G., Jr.; Crosson, William; Khan, Maudood

2005-01-01

The urban landscape is inherently complex and this complexity is not adequately captured in air quality models that are used to assess whether urban areas are in attainment of EPA air quality standards, particularly for ground level ozone. This inadequacy of air quality models to sufficiently respond to the heterogeneous nature of the urban landscape can impact how well these models predict ozone pollutant levels over metropolitan areas and ultimately, whether cities exceed EPA ozone air quality standards. We are exploring the utility of high-resolution remote sensing data and urban growth projections as improved inputs to meteorological and air quality models focusing on the Atlanta, Georgia metropolitan area as a case study. The National Land Cover Dataset at 30m resolution is being used as the land use/land cover input and aggregated to the 4km scale for the MM5 mesoscale meteorological model and the Community Multiscale Air Quality (CMAQ) modeling schemes. Use of these data have been found to better characterize low density/suburban development as compared with USGS 1 km land use/land cover data that have traditionally been used in modeling. Air quality prediction for future scenarios to 2030 is being facilitated by land use projections using a spatial growth model. Land use projections were developed using the 2030 Regional Transportation Plan developed by the Atlanta Regional Commission. This allows the State Environmental Protection agency to evaluate how these transportation plans will affect future air quality.

Ozone kinetics in low-pressure discharges

NASA Astrophysics Data System (ADS)

Guerra, Vasco; Marinov, Daniil; Guaitella, Olivier; Rousseau, Antoine

2012-10-01

Ozone kinetics is quite well established at atmospheric pressure, due to the importance of ozone in atmospheric chemistry and to the development of industrial ozone reactors. However, as the pressure is decreased and the dominant three-body reactions lose importance, the main mechanisms involved in the creation and destruction of ozone are still surrounded by important uncertainties. In this work we develop a self-consistent model for a pulsed discharge and its afterglow operating in a Pyrex reactor with inner radius 1 cm, at pressures in the range 1-5 Torr and discharge currents of 40-120 mA. The model couples the electron Boltzmann equation with a system of equations for the time evolution of the heavy particles. The calculations are compared with time-dependent measurements of ozone and atomic oxygen. Parametric studies are performed in order to clarify the role of vibrationally excited ozone in the overall kinetics and to establish the conditions where ozone production on the surface may become important. It is shown that vibrationally excited ozone does play a significant role, by increasing the time constants of ozone formation. Moreover, an upper limit for the ozone formation at the wall in these conditions is set at 10(-4).

Identifying controlling factors of ground-level ozone levels over southwestern Taiwan using a decision tree

NASA Astrophysics Data System (ADS)

Chu, Hone-Jay; Lin, Chuan-Yao; Liau, Churn-Jung; Kuo, Yi-Ming

2012-12-01

Kaohsiung City and the suburban region of southwestern Taiwan have suffered from severe air pollution since becoming the largest center of heavy industry in Taiwan. The complex process of ozone (O3) formation and its precursor compounds (the volatile organic compounds (VOCs) and nitrogen oxide (NOx) emissions), accompanied by meteorological conditions, make controlling ozone difficult. Using a decision tree is especially appropriate for analyzing time series data that contain ozone levels and meteorological and explanatory variables for ozone formation. Results show that dominant variables such as temperature, wind speed, VOCs, and NOx can play vital roles in describing ozone variations among observations. That temperature and wind speed are highly correlated with ozone levels indicates that these meteorological conditions largely affect ozone variability. The results also demonstrate that spatial heterogeneity of ozone patterns are in coastal and inland areas caused by sea-land breeze and pollutant sources during high ozone episodes over southwestern Taiwan. This study used a decision tree to obtain quantitative insight into spatial distributions of precursor compound emissions and effects of meteorological conditions on ozone levels that are useful for refining monitoring plans and developing management strategies.

Long-term meteorologically independent trend analysis of ozone air quality at an urban site in the greater Houston area.

PubMed

Botlaguduru, Venkata S V; Kommalapati, Raghava R; Huque, Ziaul

2018-04-19

The Houston-Galveston-Brazoria (HGB) area of Texas has a history of ozone exceedances and is currently classified under moderate nonattainment status for the 2008 8-hr ozone standard of 75 ppb. The HGB area is characterized by intense solar radiation, high temperature, and humidity, which influence day-to-day variations in ozone concentrations. Long-term air quality trends independent of meteorological influence need to be constructed for ascertaining the effectiveness of air quality management in this area. The Kolmogorov-Zurbenko (KZ) filter technique used to separate different scales of motion in a time series, is applied in the current study for maximum daily 8-hr (MDA8) ozone concentrations at an urban site (EPA AQS Site ID: 48-201-0024, Aldine) in the HGB area. This site located within 10 miles of downtown Houston and the George Bush Intercontinental Airport, was selected for developing long-term meteorologically independent MDA8 ozone trends for the years 1990-2016. Results from this study indicate a consistent decrease in meteorologically independent MDA8 ozone between 2000-2016. This pattern could be partially attributed to a reduction in underlying NO X emissions, particularly that of lowering nitrogen dioxide (NO 2 ) levels, and a decrease in the release of highly reactive volatile organic compounds (HRVOC). Results also suggest solar radiation to be most strongly correlated to ozone, with temperature being the secondary meteorological control variable. Relative humidity and wind speed have tertiary influence at this site. This study observed that meteorological variability accounts for a high of 61% variability in baseline ozone (low-frequency component, sum of long-term and seasonal components), while 64% of the change in long-term MDA8 ozone post-2000 could be attributed to NO X emissions reduction. Long-term MDA8 ozone trend component was estimated to be decreasing at a linear rate of 0.412 ± 0.007 ppb/yr for the years 2000-2016, and 0.155 ± 0.005 ppb/yr for the overall period of 1990-2016. Implications Statement The effectiveness of air emission controls can be evaluated by developing long-term air quality trends independent of meteorological influences. KZ filter technique is a well-established method to separate an air quality time-series into: short-term, seasonal and long-term components. This paper applies the KZ filter technique to MDA8 ozone data between 1990-2016 at an urban site in the Greater Houston area and estimates the variance accounted for, by the primary meteorological control variables. Estimates for linear trends of MDA8 ozone are calculated and underlying causes are investigated to provide a guidance for further investigation into air quality management of the Greater Houston Area.

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.

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.

Reforestation as a novel abatement and compliance measure for ground-level ozone

PubMed Central

Kroeger, Timm; Escobedo, Francisco J.; Hernandez, José L.; Varela, Sebastián; Delphin, Sonia; Fisher, Jonathan R. B.; Waldron, Janice

2014-01-01

High ambient ozone (O3) concentrations are a widespread and persistent problem globally. Although studies have documented the role of forests in removing O3 and one of its precursors, nitrogen dioxide (NO2), the cost effectiveness of using peri-urban reforestation for O3 abatement purposes has not been examined. We develop a methodology that uses available air quality and meteorological data and simplified forest structure growth-mortality and dry deposition models to assess the performance of reforestation for O3 precursor abatement. We apply this methodology to identify the cost-effective design for a hypothetical 405-ha, peri-urban reforestation project in the Houston–Galveston–Brazoria O3 nonattainment area in Texas. The project would remove an estimated 310 tons of (t) O3 and 58 t NO2 total over 30 y. Given its location in a nitrogen oxide (NOx)-limited area, and using the range of Houston area O3 production efficiencies to convert forest O3 removal to its NOx equivalent, this is equivalent to 127–209 t of the regulated NOx. The cost of reforestation per ton of NOx abated compares favorably to that of additional conventional controls if no land costs are incurred, especially if carbon offsets are generated. Purchasing agricultural lands for reforestation removes this cost advantage, but this problem could be overcome through cost-share opportunities that exist due to the public and conservation benefits of reforestation. Our findings suggest that peri-urban reforestation should be considered in O3 control efforts in Houston, other US nonattainment areas, and areas with O3 pollution problems in other countries, wherever O3 formation is predominantly NOx limited. PMID:25201970

Reforestation as a novel abatement and compliance measure for ground-level ozone.

PubMed

Kroeger, Timm; Escobedo, Francisco J; Hernandez, José L; Varela, Sebastián; Delphin, Sonia; Fisher, Jonathan R B; Waldron, Janice

2014-10-07

High ambient ozone (O3) concentrations are a widespread and persistent problem globally. Although studies have documented the role of forests in removing O3 and one of its precursors, nitrogen dioxide (NO2), the cost effectiveness of using peri-urban reforestation for O3 abatement purposes has not been examined. We develop a methodology that uses available air quality and meteorological data and simplified forest structure growth-mortality and dry deposition models to assess the performance of reforestation for O3 precursor abatement. We apply this methodology to identify the cost-effective design for a hypothetical 405-ha, peri-urban reforestation project in the Houston-Galveston-Brazoria O3 nonattainment area in Texas. The project would remove an estimated 310 tons of (t) O3 and 58 t NO2 total over 30 y. Given its location in a nitrogen oxide (NOx)-limited area, and using the range of Houston area O3 production efficiencies to convert forest O3 removal to its NOx equivalent, this is equivalent to 127-209 t of the regulated NOx. The cost of reforestation per ton of NOx abated compares favorably to that of additional conventional controls if no land costs are incurred, especially if carbon offsets are generated. Purchasing agricultural lands for reforestation removes this cost advantage, but this problem could be overcome through cost-share opportunities that exist due to the public and conservation benefits of reforestation. Our findings suggest that peri-urban reforestation should be considered in O3 control efforts in Houston, other US nonattainment areas, and areas with O3 pollution problems in other countries, wherever O3 formation is predominantly NOx limited.

Effect of Substrate Character on Heterogeneous Ozone Reaction Rate with Individual PAHs and Their Reaction Mixtures

NASA Astrophysics Data System (ADS)

Holmen, B. A.; Stevens, T.

2009-12-01

Vehicle exhaust contains many unregulated chemical compounds that are harmful to human health and the natural environment, including polycyclic aromatic hydrocarbons (PAH), a class of organic compounds derived from fuel combustion that can be carcinogenic and mutagenic. PAHs have been quantified in vehicle-derived ultrafine particles (Dp<100nm), which are more toxic than larger particles and are linked to adverse health problems, including respiratory and cardiac disease. Once emitted into the atmosphere, particle-bound PAHs can undergo “aging” reactions with oxidants, such as ozone, to form more polar species. These polar reaction products include species such as quinones that can be more toxic than the parent PAH compounds. Here, 0.4ppm ozone was reacted over a 24-hour period with the 16 EPA priority PAHs plus coronene adsorbed to (i) a quartz fiber filter and (ii) NIST diesel PM. The difference in the PAH/O3 heterogeneous reaction rate resulting from the two substrates will be discussed. The experiments were completed by spiking a known PAH mixture to the solid, reacting the samples with gas-phase ozone, and determining both PAH loss over time and products formed, using thermal-desorption gas chromatography / mass spectrometry (TD-GC/MS). The individual PAHs anthracene, phenanthrene, and fluorene, adsorbed to a QFF were also separately reacted with 0.4 ppm ozone. A volatilization control and the collection of volatilized PAHs using a Tenax-packed thermal desorption vial completed the mass balance and aided determination parent-product relationships. Heterogeneous reaction products analyzed directly without derivatization indicate the formation of 9,10-anthracenedione, 9H-fluoren-9-one, and (1,1’-biphenyl)-2,2’-dicarboxaldehyde from the reaction of ozone with the PAH mix on a QFF, but only 9,10-anthracenedione was detected for the diesel PM reaction. The implications of these results for aging of diesel particulate in urban environments will be discussed.

Characterization of Fine Particulate Matter (PM) and Secondary PM Precursor Gases in the Mexico City Metropolitan Area

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

Molina, Luisa T.; Molina, Mario J.; Volkamer, Rainer

2008-10-31

This project was one of three collaborating grants funded by DOE/ASP to characterize the fine particulate matter (PM) and secondary PM precursors in the Mexico City Metropolitan Area (MCMA) during the MILAGRO Campaign. The overall effort of MCMA-2006, one of the four components, focused on i) examination of the primary emissions of fine particles and precursor gases leading to photochemical production of atmospheric oxidants and secondary aerosol particles; ii) measurement and analysis of secondary oxidants and secondary fine PM production, with particular emphasis on secondary organic aerosol (SOA), and iii) evaluation of the photochemical and meteorological processes characteristic of themore » Mexico City Basin. The collaborative teams pursued the goals through three main tasks: i) analyses of fine PM and secondary PM precursor gaseous species data taken during the MCMA-2002/2003 campaigns and preparation of publications; ii) planning of the MILAGRO Campaign and deployment of the instrument around the MCMA; and iii) analysis of MCMA-2006 data and publication preparation. The measurement phase of the MILAGRO Campaign was successfully completed in March 2006 with excellent participation from the international scientific community and outstanding cooperation from the Mexican government agencies and institutions. The project reported here was led by the Massachusetts Institute of Technology/Molina Center for Energy and the Environment (MIT/MCE2) team and coordinated with DOE/ASP-funded collaborators at Aerodyne Research Inc., University of Colorado at Boulder and Montana State University. Currently 24 papers documenting the findings from this project have been published. The results from the project have improved significantly our understanding of the meteorological and photochemical processes contributing to the formation of ozone, secondary aerosols and other pollutants. Key findings from the MCMA-2003 include a vastly improved speciated emissions inventory from on-road vehicles: the MCMA motor vehicles produce abundant amounts of primary PM, elemental carbon, particle-bound polycyclic aromatic hydrocarbons, carbon monoxide and a wide range of air toxics; the feasibility of using eddy covariance techniques to measure fluxes of volatile organic compounds in an urban core and a valuable tool for validating local emissions inventory; a much better understanding of the sources and atmospheric loadings of volatile organic compounds; the first spectroscopic detection of glyoxal in the atmosphere; a unique analysis of the high fraction of ambient formaldehyde from primary emission sources; characterization of ozone formation and its sensitivity to VOCs and NO x; a much more extensive knowledge of the composition, size distribution and atmospheric mass loadings of both primary and secondary fine PM, including the fact that the rate of MCMA SOA production greatly exceeded that predicted by current atmospheric models; evaluations of significant errors that can arise from standard air quality monitors for O 3 and NO 2; and the implementation of an innovative Markov Chain Monte Carlo method for inorganic aerosol modeling as a powerful tool to analyze aerosol data and predict gas phase concentrations where these are unavailable. During the MILAGRO Campaign the collaborative team utilized a combination of central fixed sites and a mobile laboratory deployed throughout the MCMA to representative urban and boundary sites to measure trace gases and fine particles. Analysis of the extensive 2006 data sets has confirmed the key findings from MCMA-2002/2003; additionally MCMA-2006 provided more detailed gas and aerosol chemistry and wider regional scale coverage. Key results include an updated 2006 emissions inventory; extension of the flux system to measure fluxes of fine particles; better understanding of the sources and apportionment of aerosols, including contribution from biomass burning and industrial sources; a comprehensive evaluation of metal containing particles in a complex urban environment; identification of a close correlation between the rate of production of SOA and “Odd Oxygen” (O 3 + NO 3) and primary organic PM with CO in the urban plume; a more sophisticated understanding of the relationship between ozone formation and ozone precursors: while ozone production in the urban area is VOC-limited, the response is mostly NOx-limited in the surrounding mountain. Comparison of the findings from 2003 and 2006 also confirm that the VOC levels have decreased during the three-year period, while NO x levels remain the same. The results from the 2002/2003 and 2006 have been presented at international conferences and communicated to Mexican government officials. In addition, a large number of graduate students and post-doctoral associates were involved in the project. All data sets and publications are available to the scientific community.« less

[Health impact of ozone in 13 Italian cities].

PubMed

Mitis, Francesco; Iavarone, Ivano; Martuzzi, Marco

2007-01-01

to estimate the health impact of ozone in 13 Italian cities over 200,000 inhabitants and to produce basic elements to permit the reproducibility of the study in other urban locations. the following data have been used: population data (2001), health data (2001 or from scientific literature), environmental data (2002-2004), from urban background monitoring station and concentration/response risk coefficients derived from recent metanalyses. The indicators SOMO35 and SOMO0 have been used as a proxi of the average exposure to calcolate attributable deaths (and years of life lost) and several causes of morbility for ozone concentrations over 70 microg/m3. acute mortality for all causes and for cardiovascular mortality, respiratory-related hospital admissions in elderly, asthma exacerbation in children and adults, minor restricted activity days, lower respiratory symptoms in children. over 500 (1900) deaths, the 0.6% (2.1%) of total mortality, equivalent to about 6000 (22,000) years of life lost are attributable to ozone levels over 70 microg/m3 in the 13 Italian cities under study. Larger figures, in the order of thousands, are attributable to less severe morbidity outcomes. The health impact of ozone in Italian towns is relevant in terms of acute mortality and morbidity, although less severe than PM10 impact. Background ozone levels are increasing. Abatement strategies for ozone concentrations should consider the whole summer and not only "peak" days and look at policies limiting the concentration of precursors produced by traffic sources. Relevant health benefits can be obtained also under levels proposed as guidelines in the present environmental regulations.

Non Urban Troposphere Composition Symposium, Hollywood, Fla., November 10-12, 1976, Proceedings

NASA Technical Reports Server (NTRS)

1977-01-01

Papers are presented which originate from a conference on 'The Non-Urban Troposphere Composition', held in 1976. Attention is given to distributions of nitrous oxide in the atmosphere, and to tropospheric and stratospheric compositions which are perturbed by NO(x) emissions from high-altitude aircraft. Ozone is studied in terms of in situ measurements; various meteorological analyses of tropopause folding, ozone measurements in the Boston area, and ozone measurements in rural areas are presented. A one-dimensional model used to study tropospheric photochemistry numerically is presented as are vertical profiles of tropospheric and stratospheric molecular hydrogen. The oxidation of ammonia, methane, and hydrogen sulfide is assessed in nonurban tropospheres along with nonurban measurements of ethane and methane for various atmospheric conditions. With reference to the particle size distribution of chloride in the marine aerosol, organic and inorganic chlorine concentrations are evaluated, and measurements of sea-air CO2 flux by eddy correlation are investigated.

Formation of aldehydes and carboxylic acids in ozonated surface water and wastewater: a clear relationship with fluorescence changes.

PubMed

Liu, Chen; Tang, Xiangyu; Kim, Jaeshin; Korshin, Gregory V

2015-04-01

This study examined the formation of aldehydes and carboxylic acids in ozonated surface water and municipal wastewater secondary effluent and addressed correlations between the generation of these compounds and concurrent changes of the fluorescence of natural/effluent organic matter (NOM/EfOM) substrates. Ozonation was effective in removing fluorophores in all excitation/emission matrix (EEM) regions, with those operationally assigned to humic- and protein-like species showing relatively higher reactivity than fulvic-like species. Examination of HO exposures and attendant changes of fluorescence-based parameters allows establishing strong linear relationships between formation of the aldehydes and carboxylic acids and the relative changes of integrated fluorescence (ΔIF/IF0). This demonstrates the feasibility of surrogate monitoring of the formation of biodegradable ozonation by-products via online measurements of water/wastewater EEM fluorescence. Copyright © 2014 Elsevier Ltd. All rights reserved.

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.

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.

Influence of local meteorology and NO2 conditions on ground-level ozone concentrations in the eastern part of Texas, USA.

PubMed

Gorai, A K; Tuluri, F; Tchounwou, P B; Ambinakudige, S

2015-02-01

The influence of local climatic factors on ground-level ozone concentrations is an area of increasing interest to air quality management in regards to future climate change. This study presents an analysis on the role of temperature, wind speed, wind direction, and NO 2 level on ground-level ozone concentrations over the region of Eastern Texas, USA. Ozone concentrations at the ground level depend on the formation and dispersion processes. Formation process mainly depends on the precursor sources, whereas, the dispersion of ozone depends on meteorological factors. Study results showed that the spatial mean of ground-level ozone concentrations was highly dependent on the spatial mean of NO 2 concentrations. However, spatial distributions of NO 2 and ozone concentrations were not uniformed throughout the study period due to uneven wind speeds and wind directions. Wind speed and wind direction also played a significant role in the dispersion of ozone. Temperature profile in the area rarely had any effects on the ozone concentrations due to low spatial variations.

Influence of local meteorology and NO2 conditions on ground-level ozone concentrations in the eastern part of Texas, USA

PubMed Central

Gorai, A. K.; Tuluri, F.; Tchounwou, P. B.; Ambinakudige, S.

2014-01-01

The influence of local climatic factors on ground-level ozone concentrations is an area of increasing interest to air quality management in regards to future climate change. This study presents an analysis on the role of temperature, wind speed, wind direction, and NO2 level on ground-level ozone concentrations over the region of Eastern Texas, USA. Ozone concentrations at the ground level depend on the formation and dispersion processes. Formation process mainly depends on the precursor sources, whereas, the dispersion of ozone depends on meteorological factors. Study results showed that the spatial mean of ground-level ozone concentrations was highly dependent on the spatial mean of NO2 concentrations. However, spatial distributions of NO2 and ozone concentrations were not uniformed throughout the study period due to uneven wind speeds and wind directions. Wind speed and wind direction also played a significant role in the dispersion of ozone. Temperature profile in the area rarely had any effects on the ozone concentrations due to low spatial variations. PMID:25755687

Field responses of Prunus serotina and Asclepias syriaca to ozone around southern Lake Michigan.

PubMed

Bennett, J P; Jepsen, E A; Roth, J A

2006-07-01

Higher ozone concentrations east of southern Lake Michigan compared to west of the lake were used to test hypotheses about injury and growth effects on two plant species. We measured approximately 1000 black cherry trees and over 3000 milkweed stems from 1999 to 2001 for this purpose. Black cherry branch elongation and milkweed growth and pod formation were significantly higher west of Lake Michigan while ozone injury was greater east of Lake Michigan. Using classification and regression tree (CART) analyses we determined that departures from normal precipitation, soil nitrogen and ozone exposure/peak hourly concentrations were the most important variables affecting cherry branch elongation, and milkweed stem height and pod formation. The effects of ozone were not consistently comparable with the effects of soil nutrients, weather, insect or disease injury, and depended on species. Ozone SUM06 exposures greater than 13 ppm-h decreased cherry branch elongation 18%; peak 1-h exposures greater than 93 ppb reduced milkweed stem height 13%; and peak 1-h concentrations greater than 98 ppb reduced pod formation 11% in milkweed.

Modeling ozone uptake by urban and peri-urban forest: a case study in the Metropolitan City of Rome.

PubMed

Fusaro, Lina; Mereu, Simone; Salvatori, Elisabetta; Agliari, Elena; Fares, Silvano; Manes, Fausto

2018-03-01

Urban and peri-urban forests are green infrastructures (GI) that play a substantial role in delivering ecosystem services such as the amelioration of air quality by the removal of air pollutants, among which is ozone (O 3 ), which is the most harmful pollutant in Mediterranean metropolitan areas. Models may provide a reliable estimate of gas exchanges between vegetation and atmosphere and are thus a powerful tool to quantify and compare O 3 removal in different contexts. The present study modeled the O 3 stomatal uptake at canopy level of an urban and a peri-urban forest in the Metropolitan City of Rome in two different years. Results show different rates of O 3 fluxes between the two forests, due to different exposure to the pollutant, management practice effects on forest structure and functionality, and environmental conditions, namely, different stressors affecting the gas exchange rates of the two GIs. The periodic components of the time series calculated by means of the spectral analysis show that seasonal variation of modeled canopy transpiration is driven by precipitation in peri-urban forests, whereas in the urban forest seasonal variations are driven by vapor pressure deficit of ambient air. Moreover, in the urban forest high water availability during summer months, owing to irrigation practice, leads to an increase in O 3 uptake, thus suggesting that irrigation may enhance air phytoremediation in urban areas.

THE EMERGING RELATIONSHIP BETWEEN GROUND LEVEL OZONE AND LANDSCAPE CHARACTERISTICS

EPA Science Inventory

One of the most serious environmental health problems facing our society is that of poor air quality caused primarily by the formation of ground level ozone. Although natural ozone is beneficial in the upper atmosphere as a filter for ultraviolet radiation, ground- level ozone is...

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.

Ozone monitoring at remote sites using low-power instrumentation

Treesearch

John L. Korfmacher; Robert C. Musselman

2014-01-01

Collection of non-urban ambient ozone data at regional or larger scales (for example, Peake and Fong 1990; Bytnerowicz et al. 2004) is cost- and labor-intensive. Collection efforts are often further complicated by difficulty of access to data collection sites, the need for climate-controlled facilities to house instrumentation, and a requirement for a connection to...

Transport aloft drives peak ozone in the Mojave Desert

NASA Astrophysics Data System (ADS)

VanCuren, Richard

2015-05-01

Transport of anthropogenic pollution eastward out of the Los Angeles megacity region in California has been periodically observed to reach the Colorado River and the Colorado Plateau region beyond. In the 1980s, anthropogenic halocarbon tracers measured in and near the Las Angeles urban area and at a mountain-top site near the Colorado River, 400 km downwind, were shown to have a correlated seven-day cycle explainable by transport from the urban area with a time lag of 1-2 days. Recent short term springtime intensive studies using aircraft observations and regional modeling of long range transport of ozone from the Southern California megacity region showed frequent and persistent ozone impacts at surface sites across the Colorado Plateau and Southern Rocky Mountain region, at distances up to 1500 km, also with time lags of 1-2 days. However, the timing of ozone peaks at low altitude monitoring sites within the Mojave Desert, at distances from 100 to 400 km from the South Coast and San Joaquin Valley ozone source regions, does not show the expected time-lag behavior seen in the larger transport studies. This discrepancy is explained by recognizing ozone transport across the Mojave Desert to occur in a persistent layer of polluted air in the lower free troposphere with a base level at approximately 1 km MSL. This layer impacts elevated downwind sites directly, but only influences low altitude surface ozone maxima through deep afternoon mixing. 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), from long-range transport from Asia, and stratospheric down-mixing. Recognition of the role of afternoon mixing during spring and summer over the Mojave explains and expands the significance of previously published reports of ozone and other pollutants observed in and over the Mojave Desert, and resolves an apparent paradox in the timing of ozone peaks due to short-range and long-range transport from the upwind basins.

Ozone sensitivity in hybrid poplar correlates with insensitivity to both salicylic acid and jasmonic acid. The role of programmed cell death in lesion formation.

PubMed

Koch, J R; Creelman, R A; Eshita, S M; Seskar, M; Mullet, J E; Davis, K R

2000-06-01

Our earlier studies demonstrated that the ozone-sensitive hybrid poplar clone NE-388 displays an attenuated level of ozone-, wound-, and phytopathogen-induced defense gene expression. To determine if this reduced gene activation involves signal transduction pathways dependent on salicylic acid (SA) and/or jasmonic acid (JA), we compared the responses of NE-388 and an ozone-tolerant clone, NE-245, to these signal molecules. JA levels increased in both clones in response to ozone, but only minimal increases in SA levels were measured for either clone. Treatment with SA and methyl jasmonate induced defense gene expression only in NE-245, indicating that NE-388 is insensitive to these signal molecules. DNA fragmentation, an indicator of programmed cell death (PCD), was detected in NE-245 treated with either ozone or an avirulent phytopathogen, but was not detected in NE-388. We conclude that these clones undergo two distinct mechanisms of ozone-induced lesion formation. In NE-388, lesions appear to be due to toxic cell death resulting from a limited ability to perceive and subsequently activate SA- and/or JA-mediated antioxidant defense responses. In NE-245, SA-dependent PCD precedes lesion formation via a process related to the PCD pathway activated by phytopathogenic bacteria. These results support the hypothesis that ozone triggers a hypersensitive response.

Ozone Sensitivity in Hybrid Poplar Correlates with Insensitivity to Both Salicylic Acid and Jasmonic Acid. The Role of Programmed Cell Death in Lesion Formation1

PubMed Central

Koch, Jennifer Riehl; Creelman, Robert A.; Eshita, Steven M.; Seskar, Mirjana; Mullet, John E.; Davis, Keith R.

2000-01-01

Our earlier studies demonstrated that the ozone-sensitive hybrid poplar clone NE-388 displays an attenuated level of ozone-, wound-, and phytopathogen-induced defense gene expression. To determine if this reduced gene activation involves signal transduction pathways dependent on salicylic acid (SA) and/or jasmonic acid (JA), we compared the responses of NE-388 and an ozone-tolerant clone, NE-245, to these signal molecules. JA levels increased in both clones in response to ozone, but only minimal increases in SA levels were measured for either clone. Treatment with SA and methyl jasmonate induced defense gene expression only in NE-245, indicating that NE-388 is insensitive to these signal molecules. DNA fragmentation, an indicator of programmed cell death (PCD), was detected in NE-245 treated with either ozone or an avirulent phytopathogen, but was not detected in NE-388. We conclude that these clones undergo two distinct mechanisms of ozone-induced lesion formation. In NE-388, lesions appear to be due to toxic cell death resulting from a limited ability to perceive and subsequently activate SA- and/or JA-mediated antioxidant defense responses. In NE-245, SA-dependent PCD precedes lesion formation via a process related to the PCD pathway activated by phytopathogenic bacteria. These results support the hypothesis that ozone triggers a hypersensitive response. PMID:10859179

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.

Tropospheric Ozone Lidar Network (TOLNet) Observations of Processes Controlling Spatio-Temporal Tropospheric-Ozone Distributions

NASA Astrophysics Data System (ADS)

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

2017-12-01

The Tropospheric Ozone Lidar Network, TOLNet, has matured into a credible scientific group of six ozone lidars that are capable of accurate, high-spatio-temporal-resolution measurement of tropospheric ozone structures and morphology These lidars have demonstrated their 10% accuracy in several intercomparison campaigns and have participated in several scientific investigations both in small and large instrumentation groups. They have investigated many scientific phenomena including stratosphere-to-troposphere exchange, boundary-layer development, the interaction between the boundary layer and the free troposphere, Front-range-ozone morphology, urban outflow, land/sea interactions, et al. These processes determine the ozone distribution affecting large portions of the population. The TOLNet group is now making significant contributions to the innovation of ozone lidar instrumentation and retrieval techniques. The campaigns proposed over the next few years build on demonstrated capability to address more difficult scientific issues, especially the ozone production potential and distribution from wildfires and prescribed burns. Through scientific cooperation with other ground-based profiling instrumentation, TOLNet is also contributing to the validation of the new measurement capabilities of TEMPO.

Long term changes of tropospheric Nitrogen Dioxide over Pakistan derived from Ozone Monitoring Instrument (OMI) during the time period of October 2004 to December 2014

NASA Astrophysics Data System (ADS)

Murtaza, Rabbia; Fahim Khokhar, Muhammad

2016-07-01

Urban air pollution is causing huge number of diseases and deaths annually. Nitrogen dioxide is an important component of urban air pollution and a precursor to particulate matter, ground level ozone, and acid rain. The satellite based measurements of nitrogen dioxide from Ozone Monitoring Instrument (OMI) can help in analyzing spatio temporal variability in ground level concentrations within a large urban area. In this study, the spatial and temporal distributions of tropospheric nitrogen dioxide Vertical Column Densities (VCDs) over Pakistan are presented from 2004 to 2014. The results showed that the winter season is having high nitrogen dioxide levels as compared to summers. The increase can be attributed to the anthropogenic activities especially thermal power generation and traffic count. Punjab is one of the major provinces with high nitrogen dioxide levels followed by Sindh, Khyber Pakhtunkhwa and Balochistan. Six hotspots have been examined in the present study such as Lahore, Islamabad, Karachi, Faisalabad, Okara and Multan. Emissions of nitrogen compounds from thermal power plants and transportation sector represent a significant fraction of the total nitrogen dioxide emissions to the atmosphere.

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

Volatile chemical products emerging as largest petrochemical source of urban organic emissions

NASA Astrophysics Data System (ADS)

McDonald, Brian C.; de Gouw, Joost A.; Gilman, Jessica B.; Jathar, Shantanu H.; Akherati, Ali; Cappa, Christopher D.; Jimenez, Jose L.; Lee-Taylor, Julia; Hayes, Patrick L.; McKeen, Stuart A.; Cui, Yu Yan; Kim, Si-Wan; Gentner, Drew R.; Isaacman-VanWertz, Gabriel; Goldstein, Allen H.; Harley, Robert A.; Frost, Gregory J.; Roberts, James M.; Ryerson, Thomas B.; Trainer, Michael

2018-02-01

A gap in emission inventories of urban volatile organic compound (VOC) sources, which contribute to regional ozone and aerosol burdens, has increased as transportation emissions in the United States and Europe have declined rapidly. A detailed mass balance demonstrates that the use of volatile chemical products (VCPs)—including pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products—now constitutes half of fossil fuel VOC emissions in industrialized cities. The high fraction of VCP emissions is consistent with observed urban outdoor and indoor air measurements. We show that human exposure to carbonaceous aerosols of fossil origin is transitioning away from transportation-related sources and toward VCPs. Existing U.S. regulations on VCPs emphasize mitigating ozone and air toxics, but they currently exempt many chemicals that lead to secondary organic aerosols.

Role of photoexcited nitrogen dioxide chemistry on ozone formation and emission control strategy over the Pearl River Delta, China

EPA Science Inventory

A new hydroxyl radical formation pathway via photo-excited nitrogen dioxide chemistry is incorporated into a chemistry-only box model as well as a 3D air quality model to examine its potential role on ozone formation and emission control strategy over the Pearl River Delta region...

Effects of ozonation pretreatment on natural organic matter and wastewater derived organic matter - Possible implications on the formation of ozonation by-products.

PubMed

Papageorgiou, Alexandros; Stylianou, Stylianos K; Kaffes, Pavlos; Zouboulis, Anastasios I; Voutsa, Dimitra

2017-03-01

The aim of this study was to investigate possible implications of natural and wastewater derived organic matter in river water that is subsequently used following treatment for drinking purposes. River water was subjected to lab-scale ozonation experiments under different ozone doses (0.1, 0.4, 0.8, 1.0 and 2.0 mgO 3 /mgC) and contact times (1, 3, 5, 8 and 10 min). Mixtures of river water with humic acids or wastewaters (sewage wastewater and secondary effluents) at different proportions were also ozonated. Dissolved organic carbon and biodegradable dissolved organic carbon concentrations as well as spectroscopic characteristics (UV absorbance and fluorescence intensities) of different types of dissolved organic matter and possible changes due to the ozonation treatment are presented. River water, humic substances and wastewater exhibited distinct spectroscopic characteristics that could serve for pollution source tracing. Wastewater impacted surface water results in higher formation of carbonyl compounds. However, the formation yield (μg/mgC) of wastewaters was lower than that of surface water possibly due to different composition of wastewater derived organic matter and the presence of scavengers, which may limit the oxidative efficiency of ozone. Copyright © 2016 Elsevier Ltd. All rights reserved.

Field responses of Prunus serotina and Asclepias syriaca to ozone around southern Lake Michigan

USGS Publications Warehouse

Bennett, J.P.; Jepsen, E.A.; Roth, J.A.

2006-01-01

Higher ozone concentrations east of southern Lake Michigan compared to west of the lake were used to test hypotheses about injury and growth effects on two plant species. We measured approximately 1000 black cherry trees and over 3000 milkweed stems from 1999 to 2001 for this purpose. Black cherry branch elongation and milkweed growth and pod formation were significantly higher west of Lake Michigan while ozone injury was greater east of Lake Michigan. Using classification and regression tree (CART) analyses we determined that departures from normal precipitation, soil nitrogen and ozone exposure/peak hourly concentrations were the most important variables affecting cherry branch elongation, and milkweed stem height and pod formation. The effects of ozone were not consistently comparable with the effects of soil nutrients, weather, insect or disease injury, and depended on species. Ozone SUM06 exposures greater than 13 ppm-h decreased cherry branch elongation 18%; peak 1-h exposures greater than 93 ppb reduced milkweed stem height 13%; and peak 1-h concentrations greater than 98 ppb reduced pod formation 11% in milkweed. Decreased cherry branch elongation, milkweed stem height and pod production, and foliar injury on both species occurred at sites around southern Lake Michigan at ozone exposures of 13 SUM06 ppm-h and 93a??98 ppb peak hourly.

The impacts of ozonation on oil sands process-affected water biodegradability and biofilm formation characteristics in bioreactors.

PubMed

Hwang, Geelsu; Dong, Tao; Islam, Md Sahinoor; Sheng, Zhiya; Pérez-Estrada, Leónidas A; Liu, Yang; Gamal El-Din, Mohamed

2013-02-01

To examine the effects of the ozonation process (as an oxidation treatment for water and wastewater treatment applications) on microbial biofilm formation and biodegradability of organic compounds present in oil sands process-affected water (OSPW), biofilm reactors were operated continuously for 6weeks. Two types of biofilm substrate materials: polyethylene (PE) and polyvinylchloride (PVC), and two types of OSPW-fresh and ozonated OSPWs-were tested. Endogenous microorganisms, in OSPW, quickly formed biofilms in the reactors. Without ozonation, the bioreactor (using endogenous microorganisms) removed 13.8% of the total acid-extractable organics (TAO) and 18.5% of the parent naphthenic acids (NAs) from fresh OSPW. The combined ozonation and biodegradation process removed 87.2% of the OSPW TAO and over 99% of the OSPW parent NAs. Further UPLC/HRMS analysis showed that NA biodegradability decreased as the NA cyclization number increased. Microbial biofilm formation was found to depend on the biofilm substrate type. Copyright © 2012 Elsevier Ltd. All rights reserved.

N-nitrosodimethylamine (NDMA) formation during ozonation of N,N-dimethylhydrazine compounds: Reaction kinetics, mechanisms, and implications for NDMA formation control.

PubMed

Lim, Sungeun; Lee, Woongbae; Na, Soyoung; Shin, Jaedon; Lee, Yunho

2016-11-15

Compounds with N,N-dimethylhydrazine moieties ((CH 3 ) 2 N-N-) form N-nitrosodimethylamine (NDMA) during ozonation, but the relevant reaction chemistry is hitherto poorly understood. This study investigated the reaction kinetics and mechanisms of NDMA formation during ozonation of unsymmetrical dimethylhydrazine (UDMH) and daminozide (DMZ) as structural model N,N-dimethylhydrazine compounds. The reaction of ozone with these NDMA precursor compounds was fast, and k O3 at pH 7 was 2 × 10 6  M -1  s -1 for UDMH and 5 × 10 5  M -1  s -1 for DMZ. Molar NDMA yields (i.e., Δ[NDMA]/Δ[precursor] × 100) were 84% and 100% for UDMH and DMZ, respectively, determined at molar ozone dose ratio ([O 3 ] 0 /[precursor] 0 ) of ≥4 in the presence of tert-butanol as hydroxyl radical (OH) scavenger. The molar NDMA yields decreased significantly in the absence of tert-butanol, indicating OH formation and its subsequent reaction with the parent precursors forming negligible NDMA. The k OH at pH 7 was 4.9 × 10 9  M -1  s -1 and 3.4 × 10 9  M -1  s -1 for UDMH and DMZ, respectively. Reaction mechanisms are proposed in which an ozone adduct is formed at the nitrogen next to N,N-dimethylamine which decomposes via homolytic and heterolytic cleavages of the -N + -O-O-O - bond, forming NDMA as a final product. The heterolytic cleavage pathway explains the significant OH formation via radical intermediates. Overall, significant NDMA formation was found to be unavoidable during ozonation or even O 3 /H 2 O 2 treatment of waters containing N,N-dimethylhydrazine compounds due to their rapid reaction with ozone forming NDMA with high yield. Thus, source control or pre-treatment of N,N-dimethylhydrazine precursors and post-treatment of NDMA are proposed as the mitigation options. Copyright © 2016 Elsevier Ltd. All rights reserved.

78 FR 44485 - Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-24

...] Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan... Rule Regarding ``Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State... ground-level ozone formation. B. What should I consider as I prepare my comments for the EPA? 1...

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

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Characterization of new particle and secondary aerosol formation during summertime in Beijing, China

NASA Astrophysics Data System (ADS)

Zhang, Y. M.; Zhang, X. Y.; Sun, J. Y.; Lin, W. L.; Gong, S. L.; Shen, X. J.; Yang, S.

2011-07-01

Size-resolved aerosol number and mass concentrations and the mixing ratios of O3 and various trace gases were continuously measured at an urban station before and during the Beijing Olympic and Paralympic Games (5 June to 22 September, 2008). 23 new particle formation (NPF) events were identified; these usually were associated with changes in wind direction and/or rising concentrations of gas-phase precursors or after precipitation events. Most of the NPF events started in the morning and continued to noon as particles in the nucleation mode grew into the Aitken mode. From noon to midnight, the aerosols grew into the accumulation mode through condensation and coagulation. Ozone showed a gradual rise starting around 10:00 local time, reached its peak around 15:00 and then declined as the organics increased. The dominant new particle species were organics (40-75% of PM1) and sulphate; nitrate and ammonium were more minor contributors.

Contrasting VOC Composition in London, UK and Beijing, China

NASA Astrophysics Data System (ADS)

Dunmore, R.; Hopkins, J. R.; Shaw, M.; Squires, F. A.; Lee, J. D.; Lewis, A. C.; Hamilton, J. F.

2017-12-01

With an increasing fraction of the world's population now living in megacities, urban air quality in those locations has the potential to be one of the largest controllable factors for public health. Both London and Beijing are classified as megacities, with the latter almost twice as densely populated. The key drivers and trajectory of air pollution are unique to each location; London has substantially reduced PM10 concentrations over the past two decades but continues to have high urban NO2. Beijing has had well-reported high levels of PM, is now in a phase of gradual decline, and has proportionately low NO2. Both locations however, continue to emit a mix of gas phase pollutants with the potential to form photochemical ozone. Whilst the abundance of NOx in each city is relatively straightforward to quantify, the VOC mixtures that are present differ between these two cities and this has consequential impacts on the downwind ozone formation potential. This work reports a comprehensive assessment of VOC speciation, reactivity and abundance in the two cities using a common set of inter-comparable measurement approaches. Hourly observations of VOCs over the range C2 - C13+ were made using two gas chromatography (GC) instruments; a PLOT column based GC for the most volatile fraction (C2-C7) and a comprehensive two-dimensional GC (GCxGC) for VOCs with more than 7 carbons. London has atmospheric VOC concentrations that in mass and reactivity terms are dominated by longer chain VOCs from diesel fuel. The VOC mixture in ambient Beijing air is dominated by short chain VOCs, a mix of both alkenes from incomplete combustion sources and alkanes and aromatics from petrochemical sources. The substantial difference in the fleet proportions of gasoline and diesel powered vehicles between the two cities is clearly reflected in ambient VOCs. In summertime, isoprene was a notable contributor to VOC reactivity in both cities despite both being highly urbanised locations. The absolute amount of VOC mass was on average a factor of approximately 2 higher in Beijing compared to London. The consequences arising from the markedly different speciation of VOCs between the two locations will be discussed in terms of both ozone and SOA formation.

Ozone response to a CO2 doubling - Results from a stratospheric circulation model with heterogeneous chemistry

NASA Technical Reports Server (NTRS)

Pitari, G.; Palermi, S.; Visconti, G.; Prinn, R. G.

1992-01-01

A spectral 3D model of the stratosphere has been used to study the sensitivity of polar ozone with respect to a carbon dioxide increase. The lower stratospheric cooling associated with an imposed CO2 doubling may increase the probability of polar stratospheric cloud (PSC) formation and this affect ozone. The ozone perturbation obtained with the inclusion of a simple parameterization for heterogeneous chemistry on PSCs is compared to that relative to a pure homogeneous chemistry. In both cases the temperature perturbation is determined by a CO2 doubling, while the total chlorine content is kept at the present level. It is shown that the lower temperature may increase the depth and the extension of the ozone hole by extending the area amenable to PSC formation. It may be argued that this effect, coupled with an increasing amount of chlorine, may produce a positive feedback on the ozone destruction.

Source apportionment of emissions from light-duty gasoline vehicles and other sources in the United States for ozone and particulate matter.

PubMed

Vijayaraghavan, Krish; Lindhjem, Chris; Koo, Bonyoung; DenBleyker, Allison; Tai, Edward; Shah, Tejas; Alvarez, Yesica; Yarwood, Greg

2016-02-01

Federal Tier 3 motor vehicle emission and fuel sulfur standards have been promulgated in the United States to help attain air quality standards for ozone and PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm). The authors modeled a standard similar to Tier 3 (a hypothetical nationwide implementation of the California Low Emission Vehicle [LEV] III standards) and prior Tier 2 standards for on-road gasoline-fueled light-duty vehicles (gLDVs) to assess incremental air quality benefits in the United States (U.S.) and the relative contributions of gLDVs and other major source categories to ozone and PM2.5 in 2030. Strengthening Tier 2 to a Tier 3-like (LEV III) standard reduces the summertime monthly mean of daily maximum 8-hr average (MDA8) ozone in the eastern U.S. by up to 1.5 ppb (or 2%) and the maximum MDA8 ozone by up to 3.4 ppb (or 3%). Reducing gasoline sulfur content from 30 to 10 ppm is responsible for up to 0.3 ppb of the improvement in the monthly mean ozone and up to 0.8 ppb of the improvement in maximum ozone. Across four major urban areas-Atlanta, Detroit, Philadelphia, and St. Louis-gLDV contributions range from 5% to 9% and 3% to 6% of the summertime mean MDA8 ozone under Tier 2 and Tier 3, respectively, and from 7% to 11% and 3% to 7% of the maximum MDA8 ozone under Tier 2 and Tier 3, respectively. Monthly mean 24-hr PM2.5 decreases by up to 0.5 μg/m(3) (or 3%) in the eastern U.S. from Tier 2 to Tier 3, with about 0.1 μg/m(3) of the reduction due to the lower gasoline sulfur content. At the four urban areas under the Tier 3 program, gLDV emissions contribute 3.4-5.0% and 1.7-2.4% of the winter and summer mean 24-hr PM2.5, respectively, and 3.8-4.6% and 1.5-2.0% of the mean 24-hr PM2.5 on days with elevated PM2.5 in winter and summer, respectively. Following U.S. Tier 3 emissions and fuel sulfur standards for gasoline-fueled passenger cars and light trucks, these vehicles are expected to contribute less than 6% of the summertime mean daily maximum 8-hr ozone and less than 7% and 4% of the winter and summer mean 24-hr PM2.5 in the eastern U.S. in 2030. On days with elevated ozone or PM2.5 at four major urban areas, these vehicles contribute less than 7% of ozone and less than 5% of PM2.5, with sources outside North America and U.S. area source emissions constituting some of the main contributors to ozone and PM2.5, respectively.

Power plant fuel switching and air quality in a tropical, forested environment

DOE PAGES

Medeiros, Adan S. S.; Calderaro, Gisele; Guimarães, Patricia C.; ...

2017-07-26

How a changing energy matrix for electricity production affects air quality is considered for an urban region in a tropical, forested environment. Manaus, the largest city in the central Amazon Basin of Brazil, is in the process of changing its energy matrix for electricity production from fuel oil and diesel to natural gas over an approximately 10-year period, with a minor contribution by hydropower. Three scenarios of urban air quality, specifically afternoon ozone concentrations, were simulated using the Weather Research and Forecasting (WRF-Chem) model. The first scenario used fuel oil and diesel for electricity production, which was the reality inmore » 2008. The second scenario was based on the fuel mix from 2014, the most current year for which data were available. The third scenario considered nearly complete use of natural gas for electricity production, which is the anticipated future, possibly for 2018. For each case, inventories of anthropogenic emissions were based on electricity generation, refinery operations, and transportation. Transportation and refinery operations were held constant across the three scenarios to focus on effects of power plant fuel switching in a tropical context. The simulated NO x and CO emissions for the urban region decrease by 89 and 55 %, respectively, after the complete change in the energy matrix. The results of the simulations indicate that a change to natural gas significantly decreases maximum afternoon ozone concentrations over the population center, reducing ozone by >70 % for the most polluted days. The sensitivity of ozone concentrations to the fuel switchover is consistent with a NO x-limited regime, as expected for a tropical forest having high emissions of biogenic volatile organic compounds, high water vapor concentrations, and abundant solar radiation. There are key differences in a shifting energy matrix in a tropical, forested environment compared to other world environments. Therefore, policies favoring the burning of natural gas in place of fuel oil and diesel have great potential for ozone reduction and improved air quality for growing urban regions located in tropical, forested environments around the world.« less

Power plant fuel switching and air quality in a tropical, forested environment

NASA Astrophysics Data System (ADS)

Medeiros, Adan S. S.; Calderaro, Gisele; Guimarães, Patricia C.; Magalhaes, Mateus R.; Morais, Marcos V. B.; Rafee, Sameh A. A.; Ribeiro, Igor O.; Andreoli, Rita V.; Martins, Jorge A.; Martins, Leila D.; Martin, Scot T.; Souza, Rodrigo A. F.

2017-07-01

How a changing energy matrix for electricity production affects air quality is considered for an urban region in a tropical, forested environment. Manaus, the largest city in the central Amazon Basin of Brazil, is in the process of changing its energy matrix for electricity production from fuel oil and diesel to natural gas over an approximately 10-year period, with a minor contribution by hydropower. Three scenarios of urban air quality, specifically afternoon ozone concentrations, were simulated using the Weather Research and Forecasting (WRF-Chem) model. The first scenario used fuel oil and diesel for electricity production, which was the reality in 2008. The second scenario was based on the fuel mix from 2014, the most current year for which data were available. The third scenario considered nearly complete use of natural gas for electricity production, which is the anticipated future, possibly for 2018. For each case, inventories of anthropogenic emissions were based on electricity generation, refinery operations, and transportation. Transportation and refinery operations were held constant across the three scenarios to focus on effects of power plant fuel switching in a tropical context. The simulated NOx and CO emissions for the urban region decrease by 89 and 55 %, respectively, after the complete change in the energy matrix. The results of the simulations indicate that a change to natural gas significantly decreases maximum afternoon ozone concentrations over the population center, reducing ozone by > 70 % for the most polluted days. The sensitivity of ozone concentrations to the fuel switchover is consistent with a NOx-limited regime, as expected for a tropical forest having high emissions of biogenic volatile organic compounds, high water vapor concentrations, and abundant solar radiation. There are key differences in a shifting energy matrix in a tropical, forested environment compared to other world environments. Policies favoring the burning of natural gas in place of fuel oil and diesel have great potential for ozone reduction and improved air quality for growing urban regions located in tropical, forested environments around the world.

Power plant fuel switching and air quality in a tropical, forested environment

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

Medeiros, Adan S. S.; Calderaro, Gisele; Guimarães, Patricia C.

How a changing energy matrix for electricity production affects air quality is considered for an urban region in a tropical, forested environment. Manaus, the largest city in the central Amazon Basin of Brazil, is in the process of changing its energy matrix for electricity production from fuel oil and diesel to natural gas over an approximately 10-year period, with a minor contribution by hydropower. Three scenarios of urban air quality, specifically afternoon ozone concentrations, were simulated using the Weather Research and Forecasting (WRF-Chem) model. The first scenario used fuel oil and diesel for electricity production, which was the reality inmore » 2008. The second scenario was based on the fuel mix from 2014, the most current year for which data were available. The third scenario considered nearly complete use of natural gas for electricity production, which is the anticipated future, possibly for 2018. For each case, inventories of anthropogenic emissions were based on electricity generation, refinery operations, and transportation. Transportation and refinery operations were held constant across the three scenarios to focus on effects of power plant fuel switching in a tropical context. The simulated NO x and CO emissions for the urban region decrease by 89 and 55 %, respectively, after the complete change in the energy matrix. The results of the simulations indicate that a change to natural gas significantly decreases maximum afternoon ozone concentrations over the population center, reducing ozone by >70 % for the most polluted days. The sensitivity of ozone concentrations to the fuel switchover is consistent with a NO x-limited regime, as expected for a tropical forest having high emissions of biogenic volatile organic compounds, high water vapor concentrations, and abundant solar radiation. There are key differences in a shifting energy matrix in a tropical, forested environment compared to other world environments. Therefore, policies favoring the burning of natural gas in place of fuel oil and diesel have great potential for ozone reduction and improved air quality for growing urban regions located in tropical, forested environments around the world.« less

Airborne lidar mapping of vertical ozone distributions in support of the 1990 Clean Air Act Amendments

NASA Technical Reports Server (NTRS)

Uthe, Edward E.; Nielsen, Norman B.; Livingston, John M.

1992-01-01

The 1990 Clean Air Act Amendments mandated attainment of the ozone standard established by the U.S. Environmental Protection Agency. Improved photochemical models validated by experimental data are needed to develop strategies for reducing near surface ozone concentrations downwind of urban and industrial centers. For more than 10 years, lidar has been used on large aircraft to provide unique information on ozone distributions in the atmosphere. However, compact airborne lidar systems are needed for operation on small aircraft of the type typically used on regional air quality investigations to collect data with which to develop and validate air quality models. Data presented in this paper will consist of a comparison between airborne differential absorption lidar (DIAL) and airborne in-situ ozone measurements. Also discussed are future plans to improve the airborne ultraviolet-DIAL for ozone and other gas observations and addition of a Fourier Transform Infrared (FTIR) emission spectrometer to investigate the effects of other gas species on vertical ozone distribution.

Air Quality Modeling for the Urban Jackson, Mississippi Region Using a High Resolution WRF/Chem Model

PubMed Central

Yerramilli, Anjaneyulu; Dodla, Venkata B.; Desamsetti, Srinivas; Challa, Srinivas V.; Young, John H.; Patrick, Chuck; Baham, Julius M.; Hughes, Robert L.; Yerramilli, Sudha; Tuluri, Francis; Hardy, Mark G.; Swanier, Shelton J.

2011-01-01

In this study, an attempt was made to simulate the air quality with reference to ozone over the Jackson (Mississippi) region using an online WRF/Chem (Weather Research and Forecasting–Chemistry) model. The WRF/Chem model has the advantages of the integration of the meteorological and chemistry modules with the same computational grid and same physical parameterizations and includes the feedback between the atmospheric chemistry and physical processes. The model was designed to have three nested domains with the inner-most domain covering the study region with a resolution of 1 km. The model was integrated for 48 hours continuously starting from 0000 UTC of 6 June 2006 and the evolution of surface ozone and other precursor pollutants were analyzed. The model simulated atmospheric flow fields and distributions of NO2 and O3 were evaluated for each of the three different time periods. The GIS based spatial distribution maps for ozone, its precursors NO, NO2, CO and HONO and the back trajectories indicate that all the mobile sources in Jackson, Ridgeland and Madison contributing significantly for their formation. The present study demonstrates the applicability of WRF/Chem model to generate quantitative information at high spatial and temporal resolution for the development of decision support systems for air quality regulatory agencies and health administrators. PMID:21776240

Production of NOx and other precursors of ozone formation in the Uinta Basin

NASA Astrophysics Data System (ADS)

Smith, E.; Lyman, S. N.; Martin, R. S.; Anderson, R.

2012-12-01

The Uinta Basin, located in northeastern Utah, sometimes experiences ozone mixing ratios greater than the EPA NAAQS during specific meteorological conditions that include a combination of snow cover and inversion. We monitored ozone and some of its precursors, including NO, NO2, NOx (NO + NO2), and NOy (sum of reactive nitrogen species), at two sites (Roosevelt and Horse Pool). The Roosevelt site is in a city of about 6,000 people, and the Horse Pool site is in an area of intensive oil and gas production. In February and March 2012, NO, NO2, and NOy mixing ratios were 0.5 ± 0.8, 5.2 ± 2.6, and 6.5 ± 3.9 ppb at Roosevelt and 0 ± 1.3, 2.8 ± 2.7, and 4.1 ± 4.4 ppb at Horse Pool, respectively (mean ± standard deviation). NO, NO2, and NOx were measured at 7 other sites around the Basin by other entities. The spatial and temporal patterns in NOx and NOy indicate the dominance of local source influences on observed mixing ratios. NOx at urban sites and in oil and gas production areas appeared strongly influenced by traffic patterns. At some sites, wind direction analysis and air trajectory analysis indicated that areas of oil and gas production are significant sources of NOx, though pinpointing individual NOx sources proved difficult.

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.

Characterization Urban Heat Island Effect and Modelling of Secondary Pollutant Formations at Urban Hotspots

NASA Astrophysics Data System (ADS)

Undi, G. S. N. V. K. S. N. S.

2017-12-01

More than 60 percent of the world population is living the urban zones by 2020. This socio of economic transformations will bring considerable changes to the ambient atmosphere. More than 70 percent of the air pollutants in the urban hotspots are from vehicular emissions. in the urban hotspots. In the urban hotspots, the meteorological and dispersion conditions will have different characteristics than in surrounding rural areas. Reactive pollutants transformations are drastically influenced by the local meteorological conditions. The complexity of urban structure alters the pollutants dispersion in the hotspots. This relationship between urban meteorology and air pollution is an important aspect of consideration. In the atmosphere, drastic changes have been noticed from micro to regional and global scales. However, the characteristics of air pollutant emissions vary with time and space, favorable dispersion conditions transport them from local to regional scale. In the present study, the impact of land cover change on Urban Heat Island effect (UHI) has been characterized by considering the three different zones with varying land use patterns. An attempt has been made to estimate the impact of UHI on secondary pollutants (O3) transformations. Envi-Met model has been used to characterize the UHI intensity for the selected zones. Meteorological and air quality measurements were carried out at the selected locations. The diurnal variations of Ozone (O3) concentration for three zones are correlated with the UHI intensity. And the monitoring and model results of O3 concentrations are in good agreement. It is observed from the obtained model results that the metrological parameters influence on local air quality is significant in urban zones.

Influence of ozone and nitrogen deposition on bark beetle activity under drought conditions

Treesearch

Michele Eatough Jones; Timothy D. Paine; Mark E. Fenn; Mark A. Poth

2004-01-01

Four years of severe drought from 1999 through 2003 led to unprecedented bark beetle activity in ponderosa and Jeffrey pine in the San Bernardino and San Jacinto Mountains of southern California. Pines in the San Bernardino Mountains also were heavily impacted by ozone and nitrogenous pollutants originating from urban and agricultural areas in the Los Angeles basin. We...

Controlling Urban Air Pollution: A Benefit-Cost Assessment.

ERIC Educational Resources Information Center

Krupnick, Alan J.; Portney, Paul R.

1991-01-01

The pros and cons of air pollution control efforts are discussed. Both national and regional air pollution control plans are described. Topics of discussion include benefit-cost analysis, air quality regulation, reducing ozone in the urban areas, the Los Angeles plan, uncertainties, and policy implications. (KR)

Urban Air Pollution: State of the Science.

ERIC Educational Resources Information Center

Seinfeld, John H.

1989-01-01

Describes the highly complex mixture of gaseous and particulate matter found in urban air. Explains progress made in the understanding of the physics and chemistry of air pollution, the effects of precursors on ozone, the role of biogenic hydrocarbons, and the principal benefit of methanol-fueled vehicles. (RT)

Remote Sensing and Spatial Growth Modeling Coupled with Air Quality Modeling to Assess the Impact of Atlanta, Georgia on the Local and Regional Environment

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Estes, Maurice G., Jr.; Crosson, William; Khan, Maudood

2006-01-01

The growth of cities, both in population and areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 80 percent of the world s population will live in cities. Directly aligned with the expansion of cities is urban sprawl. Urban expansion has profound impacts on a host of biophysical, environmental, and atmospheric processes. A reduction in air quality over cities is a major result of these impacts. Strategies that can be directly or indirectly implemented to help remediate air quality problems in cities and that can be accepted by political decision makers and the general public are now being explored to help bring down air pollutants and improve air quality. The urban landscape is inherently complex and this complexity is not adequately captured in air quality models, particularly the Community Multiscale Air Quality (CMAQ) model that is used to assess whether urban areas are in attainment of EPA air quality standards, primarily for ground level ozone. This inadequacy of the CMAQ model to sufficiently respond to the heterogeneous nature of the urban landscape can impact how well the model predicts ozone pollutant levels over metropolitan areas and ultimately, whether cities exceed EPA ozone air quality standards. We are exploring the utility of high-resolution remote sensing data and urban spatial growth modeling (SGM) projections as improved inputs to the meteorology component of the CMAQ model focusing on the Atlanta, Georgia metropolitan area as a case study. These growth projections include "business as usual" and "smart growth" scenarios out to 2030. The growth projections illustrate the effects of employing urban heat island mitigation strategies, such as increasing tree canopy and albedo across the Atlanta metro area, which in turn, are used to model how ozone and air temperature can potentially be moderated as impacts on elevating ground-level ozone, as opposed to not utilizing heat island mitigation strategies. The National Land Cover Dataset at 30m resolution is being used as the land use/land cover input and aggregated to the 4km scale for the MM5 mesoscale meteorological model and the (CMAQ) modeling schemes. Use of these data have been found to better characterize low density/suburban development as compared with USGS 1km land use/land cover data that have traditionally been used in modeling. Air quality prediction for future scenarios to 2030 is being facilitated by land use projections using a spatial growth model. Land use projections were developed using the 2030 Regional Transportation Plan developed by the Atlanta Regional Commission, the regional planning agency for the area. This allows the State Environmental Protection agency to evaluate how these transportation plans will affect future air quality. The coupled SGM and air quality modeling approach provides insight on what the impacts of Atlanta s growth will be on the local and regional environment and exists as a mechanism that can be used by policy makers to make rationale decisions on urban growth and sustainability for the metropolitan area in the future.

Presenting SAPUSS: Solving Aerosol Problem by Using Synergistic Strategies in Barcelona, Spain

NASA Astrophysics Data System (ADS)

Dall'Osto, M.; Querol, X.; Alastuey, A.; Minguillon, M. C.; Alier, M.; Amato, F.; Brines, M.; Cusack, M.; Grimalt, J. O.; Karanasiou, A.; Moreno, T.; Pandolfi, M.; Pey, J.; Reche, C.; Ripoll, A.; Tauler, R.; Van Drooge, B. L.; Viana, M.; Harrison, R. M.; Gietl, J.; Beddows, D.; Bloss, W.; O'Dowd, C.; Ceburnis, D.; Martucci, G.; Ng, N. L.; Worsnop, D.; Wenger, J.; Mc Gillicuddy, E.; Sodeau, J.; Healy, R.; Lucarelli, F.; Nava, S.; Jimenez, J. L.; Gomez Moreno, F.; Artinano, B.; Prévôt, A. S. H.; Pfaffenberger, L.; Frey, S.; Wilsenack, F.; Casabona, D.; Jiménez-Guerrero, P.; Gross, D.; Cots, N.

2013-09-01

This paper presents the summary of the key objectives, instrumentation and logistic details, goals, and initial scientific findings of the European Marie Curie Action SAPUSS project carried out in the western Mediterranean Basin (WMB) during September-October in autumn 2010. The key SAPUSS objective is to deduce aerosol source characteristics and to understand the atmospheric processes responsible for their generations and transformations - both horizontally and vertically in the Mediterranean urban environment. In order to achieve so, the unique approach of SAPUSS is the concurrent measurements of aerosols with multiple techniques occurring simultaneously in six monitoring sites around the city of Barcelona (NE Spain): a main road traffic site, two urban background sites, a regional background site and two urban tower sites (150 m and 545 m above sea level, 150 m and 80 m above ground, respectively). SAPUSS allows us to advance our knowledge sensibly of the atmospheric chemistry and physics of the urban Mediterranean environment. This is well achieved only because of both the three dimensional spatial scale and the high sampling time resolution used. During SAPUSS different meteorological regimes were encountered, including warm Saharan, cold Atlantic, wet European and stagnant regional ones. The different meteorology of such regimes is herein described. Additionally, we report the trends of the parameters regulated by air quality purposes (both gaseous and aerosol mass concentrations); and we also compare the six monitoring sites. High levels of traffic-related gaseous pollutants were measured at the urban ground level monitoring sites, whereas layers of tropospheric ozone were recorded at tower levels. Particularly, tower level night-time average ozone concentrations (80 ± 25 μg m-3) were up to double compared to ground level ones. The examination of the vertical profiles clearly shows the predominant influence of NOx on ozone concentrations, and a source of ozone aloft. Analysis of the particulate matter (PM) mass concentrations shows an enhancement of coarse particles (PM2.5-10) at the urban ground level (+64%, average 11.7 μg m-3) but of fine ones (PM1) at urban tower level (+28%, average 14.4 μg m-3). These results show complex dynamics of the size-resolved PM mass at both horizontal and vertical levels of the study area. Preliminary modelling findings reveal an underestimation of the fine accumulation aerosols. In summary, this paper lays the foundation of SAPUSS, an integrated study of relevance to many other similar urban Mediterranean coastal environment sites.

LABORATORY AND COMPUTATIONAL INVESTIGATIONS OF THE ATMOSPHERIC CHEMISTRY OF KEY OXIDATION PRODUCTS CONTROLLING TROPOSPHERIC OZONE FORMATION

EPA Science Inventory

Major uncertainties remain in our ability to identify the key reactions and primary oxidation products of volatile hydrocarbons that contribute to ozone formation in the troposphere. To reduce these uncertainties, computational chemistry, mechanistic and process analysis techniqu...

Tropospheric ozone over the North Pacific from ozonesonde observations

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Johnson, B. J.; Harris, J. M.; Thompson, A. M.; Liu, H. Y.; Chan, C. Y.; VöMel, H.; Fujimoto, T.; Brackett, V. G.; Chang, W. L.; Chen, J.-P.; Kim, J. H.; Chan, L. Y.; Chang, H.-W.

2004-08-01

As part of the Transport and Chemical Evolution over the Pacific (TRACE-P) mission, ozonesondes were used to make ozone vertical profile measurements at nine locations in the North Pacific. At most of the sites there is a multiyear record of observations. From locations in the western Pacific (Hong Kong; Taipei; Jeju Island, Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the central Pacific (Hilo, Hawaii), and a site on the west coast of the United States (Trinidad Head, California) both a seasonal and event specific picture of tropospheric ozone over the North Pacific emerges. Ozone profiles over the North Pacific generally show a prominent spring maximum throughout the troposphere. This maximum is tied to the location of the jet stream and its influence on stratosphere-troposphere exchange and the increase in photochemical ozone production through the spring. Prominent layers of enhanced ozone in the middle and upper troposphere north of about 30°N seem to be more closely tied to stratospheric intrusions while biomass burning leads to layers of enhanced ozone in the lower and upper troposphere at Hong Kong (22°N) and Taipei (25°N). The lower free tropospheric layers at Hong Kong are associated with burning in SE Asia, but the upper layer may be associated with either equatorial Northern Hemisphere burning in Africa or SE Asian biomass burning. In the boundary layer at Taipei very high mixing ratios of ozone were observed that result from pollution transport from China in the spring and local urban pollution during the summer. At the ozonesonde site near Tokyo (Tsukuba, 36°N) very large enhancements of ozone are seen in the boundary layer in the summer that are characteristic of urban air pollution. At sites in the mid and eastern Pacific the signature of transport of polluted air from Asia is not readily identifiable from the ozonesonde profile. This is likely due to the more subtle signal and the fact that from the ozone profile and meteorological data by themselves it is difficult to identify such a signal. During the TRACE-P intensive campaign period (February-April 2001), tropospheric ozone amounts were generally typical of those seen in the long-term records of the stations with multiyear soundings. The exception was the upper troposphere over Hong Kong and Taipei where ozone amounts were lower in 2001.

Determination of volatile organic compound emissions and ozone formation from spraying solvent-based pesticides.

PubMed

Kumar, Anuj; Howard, Cody J; Derrick, Doniche; Malkina, Irina L; Mitloehner, Frank M; Kleeman, Michael J; Alaimo, Christopher P; Flocchini, Robert G; Green, Peter G

2011-01-01

Large-scale agricultural activities have come under scrutiny for possible contributions to the emission of ozone precursors. The San Joaquin Valley (SJV) of California is an area with intense agricultural activity that exceeds the federal ozone standards for more than 30 to 40 d yr(-1) and the more stringent state standards for more than 100 d yr(-1). Pesticides are used widely in both agricultural and residential subregions of the SJV, but the largest use, by weight of "active ingredient," is in agriculture. The objective of the study was to determine the role of pesticide application on airborne volatile organic compounds (VOC) concentrations and ozone formation in the SJV. The ozone formation from the pesticide formulation sprayed on commercial orchards was studied using two transportable smog chambers at four application sites during the summers of 2007 and 2008. In addition to the direct measurements of ozone formation, airborne VOC concentrations were measured before and after pesticide spraying using canister and sorbent tube sampling techniques. Soil VOC concentrations were also measured to understand the distribution of VOCs between different environmental compartments. Numerous VOCs were detected in the air and soil samples throughout the experiment but higher molecular weight aromatic hydrocarbons were the primary compounds observed in elevated concentrations immediately after pesticide spraying. Measurements indicate that the ozone concentration formed by VOC downwind of the orchard may increase up to 15 ppb after pesticide application, with a return back to prespray levels after 1 to 2 d. by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Biogenic and anthropogenic isoprene in the near-surface urban atmosphere--a case study in Essen, Germany.

PubMed

Wagner, Patrick; Kuttler, Wilhelm

2014-03-15

Isoprene is emitted in large quantities by vegetation, exhaled by human beings and released in small quantities by road traffic. As a result of its high reactivity, isoprene is an important ozone precursor in the troposphere and can play a key role in atmospheric chemistry. Measurements of isoprene in urban areas in Central Europe are scarce. Thus, in Essen, Germany, the isoprene concentration was measured at various sites during different seasons using two compact online GC-PID systems. Isoprene concentrations were compared with those of benzene and toluene, which represent typical anthropogenic VOCs. In the summer, the diurnal variation in isoprene concentration was dependent on the biogenic emissions in the city. It was found that its maximum concentration occurred during the day, in contrast to the benzene and toluene concentrations. During the measurement period in the summer of 2012, the average hourly isoprene concentrations reached 0.13 to 0.17 ppb between 10 and 20 LST. At high air temperatures, the isoprene concentration exceeded the benzene and toluene concentrations at many of the sites. Isoprene became more important than toluene with regard to ozone formation in the city area during the afternoon hours of summer days with high air temperatures. This finding was demonstrated by the contributions to OH reactivity and ozone-forming potential. It contradicts the results of other studies, which were based on daily or seasonal average values. With an isoprene/benzene ratio of 0.02, the contribution of anthropogenic isoprene decreased substantially to a very low level during the last 20 years in Central Europe due to a strong reduction in road traffic emissions. In the vicinity of many people, isoprene concentrations of up to 0.54 ppb and isoprene/benzene ratios of up to 1.34 were found in the atmosphere due to isoprene exhaled by humans. Copyright © 2013. Published by Elsevier B.V.

Effects of air pollution on lung function and symptoms of asthma, rhinitis and eczema in primary school children.

PubMed

Altuğ, Hicran; Gaga, Eftade O; Döğeroğlu, Tuncay; Ozden, Ozlem; Ornektekin, Sermin; Brunekreef, Bert; Meliefste, Kees; Hoek, Gerard; Van Doorn, Wim

2013-09-01

Health effects of ambient air pollution were studied in three groups of schoolchildren living in areas (suburban, urban and urban-traffic) with different air pollution levels in Eskişehir, Turkey. This study involved 1,880 students aged between 9 and 13 years from 16 public primary schools. This two-season study was conducted from January 2008 through March 2009. Symptoms of asthma, rhinitis and eczema were determined by the International Study of Asthma and Allergies in Childhood questionnaire in 2008. Two lung function tests were performed by each child for summer and winter seasons with simultaneous ambient air measurements of ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2) by passive sampling. Effects of air pollution on impaired lung function and symptoms in schoolchildren were estimated by multivariate logistic regression analyses. Girls with impaired lung function (only for the summer season evaluation) were more observed in suburban and urban areas when compared to urban-traffic area ([odds ratio (OR) = 1.49; 95 % confidence interval (CI) 1.04-2.14] and [OR = 1.69 (95 % CI 1.06-2.71)] for suburban vs. urban-traffic and urban vs. urban-traffic, respectively). Significant association between ambient ozone concentrations and impaired lung function (for an increase of 10 μg m(-3)) was found only for girls for the summer season evaluation [OR = 1.11 (95 % CI 1.03-1.19)]. No association was found for boys and for the winter season evaluation. No association was found between any of the measured air pollutants and symptoms of current wheeze, current rhinoconjunctivitis and current itchy rash. The results of this study showed that increasing ozone concentrations may cause a sub-acute impairment in lung function of school aged children.

The formation and control of emerging disinfection by-products of health concern.

PubMed

Krasner, Stuart W

2009-10-13

When drinking water treatment plants disinfect water, a wide range of disinfection by-products (DBPs) of health and regulatory concern are formed. Recent studies have identified emerging DBPs (e.g. iodinated trihalomethanes (THMs) and acids, haloacetonitriles, halonitromethanes (HNMs), haloacetaldehydes, nitrosamines) that may be more toxic than some of the regulated ones (e.g. chlorine- and bromine-containing THMs and haloacetic acids). Some of these emerging DBPs are associated with impaired drinking water supplies (e.g. impacted by treated wastewater, algae, iodide). In some cases, alternative primary or secondary disinfectants to chlorine (e.g. chloramines, chlorine dioxide, ozone, ultraviolet) that minimize the formation of some of the regulated DBPs may increase the formation of some of the emerging by-products. However, optimization of the various treatment processes and disinfection scenarios can allow plants to control to varying degrees the formation of regulated and emerging DBPs. For example, pre-disinfection with chlorine, chlorine dioxide or ozone can destroy precursors for N-nitrosodimethylamine, which is a chloramine by-product, whereas pre-oxidation with chlorine or ozone can oxidize iodide to iodate and minimize iodinated DBP formation during post-chloramination. Although pre-ozonation may increase the formation of trihaloacetaldehydes or selected HNMs during post-chlorination or chloramination, biofiltration may reduce the formation potential of these by-products.

Spatial distribution of tropospheric ozone in western Washington, USA

USGS Publications Warehouse

Cooper, S.M.; Peterson, D.L.

2000-01-01

We quantified the distribution of tropospheric ozone in topographically complex western Washington state, USA (total area a??6000 km2), using passive ozone samplers along nine river drainages to measure ozone exposure from near sea level to high-elevation mountain sites. Weekly average ozone concentrations were higher with increasing distance from the urban core and at higher elevations, increasing a mean of 1.3 ppbv per 100 m elevation gain for all mountain transects. Weekly average ozone concentrations were generally highest in Cascade Mountains drainages east and southeast of Seattle (maximum=55a??67 pbv) and in the Columbia River Gorge east of Portland (maximum=59 ppbv), and lowest in the western Olympic Peninsula (maximum=34 ppbv). Higher ozone concentrations in the Cascade Mountains and Columbia River locations downwind of large cities indicate that significant quantities of ozone and ozone precursors are being transported eastward toward rural wildland areas by prevailing westerly winds. In addition, temporal (week to week) variation in ozone distribution is synchronous within and between all drainages sampled, which indicates that there is regional coherence in air pollution detectable with weekly averages. These data provide insight on large-scale spatial variation of ozone distribution in western Washington, and will help regulatory agencies optimize future monitoring networks and identify locations where human health and natural resources could be at risk.

MODELING CRYPTOSPORIDIUM PARVUM OOCYST INACTIVATION AND BROMATE IN A FLOW-THROUGH OZONE CONTACTOR TREATING NATURAL WATER

EPA Science Inventory

A reactive transport model was developed to simultaneously predict Cryptosporidium parvum oocyst inactivation and bromate formation during ozonation of natural water. A mechanistic model previously established to predict bromate formation in organic-free synthetic waters w...

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

Summary of 1978 Southeastern Virginia Urban Plume study: Aircraft results for carbon monoxide, methane, nonmethane hydrocarbons, and ozone

NASA Technical Reports Server (NTRS)

Hill, G. F.; Sachse, G. W.; Cofer, W. R., III

1981-01-01

The characteristics of the Southeastern Virginia urban plume were defined with emphasis on the photon-oxidant species. The measurement area was a rectangle, approximately 150 km by 100 km centered around Cape Charles, Virginia. Included in this area are the cities of Norfolk, Virginia Beach, Chesapeake, Newport News, and Hampton. The area is bounded on the north by Wallops Island, Virginia, and on the south by the Hampton Roads area of Tidewater Virginia. The major axis of the rectangle is oriented in the southwest-northeast direction. The data set includes aircraft measurements for carbon monoxide, methane, nonmethane hydrocarbons, and ozone. The experiment shows that CO can be successfully measured as a tracer gas and used as an index for determining localized and urban plumes. The 1978 data base provided sufficient data to assess an automated chromatograph with flame ionization detection used for measuring methane and nonmethane hydrocarbons in flight.

The 1979 Southeastern Virginia Urban Plume Study. Volume 1: Description of experiments and selected aircraft data

NASA Technical Reports Server (NTRS)

Gregory, G. L.; Lee, R. B., III; Mathis, J. J., Jr.

1981-01-01

The Southeastern Virginia Urban Plume Study (SEV-UPS) utilizes remote sensors and satellite platforms to monitor the Earth's environment and resources. SEV-UPS focuses on the application of specific remote sensors to the monitoring and study of specific air quality problems. The 1979 SEV-UPS field program was conducted with specific objectives: (1) to provide correlative data to evaluate the Laser Absorption spectrometer ozone remote sensors; (2) to demonstrate the utility of the sensor for the study of urban ozone problems; (3) to provide additional insights into air quality phenomena occuring in Southeastern Virginia; and (4) to compare measurement results of various in situ measurement platforms. The field program included monitoring from 12 surface stations, 4 aircraft, 2 tethered balloons, 2 radiosonde release sites, and numerous surface meteorological observation sites. The aircraft monitored 03, NO, NOX, Bscat, temperature, and dewpoint temperature.

Cellulose and lignin biosynthesis is altered by ozone in wood of hybrid poplar (Populus tremula×alba)

PubMed Central

Richet, Nicolas; Afif, Dany; Huber, Françoise; Pollet, Brigitte; Banvoy, Jacques; El Zein, Rana; Lapierre, Catherine; Dizengremel, Pierre; Perré, Patrick; Cabané, Mireille

2011-01-01

Wood formation in trees is a dynamic process that is strongly affected by environmental factors. However, the impact of ozone on wood is poorly documented. The objective of this study was to assess the effects of ozone on wood formation by focusing on the two major wood components, cellulose and lignin, and analysing any anatomical modifications. Young hybrid poplars (Populus tremula×alba) were cultivated under different ozone concentrations (50, 100, 200, and 300 nl l−1). As upright poplars usually develop tension wood in a non-set pattern, the trees were bent in order to induce tension wood formation on the upper side of the stem and normal or opposite wood on the lower side. Biosynthesis of cellulose and lignin (enzymes and RNA levels), together with cambial growth, decreased in response to ozone exposure. The cellulose to lignin ratio was reduced, suggesting that cellulose biosynthesis was more affected than that of lignin. Tension wood was generally more altered than opposite wood, especially at the anatomical level. Tension wood may be more susceptible to reduced carbon allocation to the stems under ozone exposure. These results suggested a coordinated regulation of cellulose and lignin deposition to sustain mechanical strength under ozone. The modifications of the cellulose to lignin ratio and wood anatomy could allow the tree to maintain radial growth while minimizing carbon cost. PMID:21357770

Application of validation data for assessing spatial interpolation methods for 8-h ozone or other sparsely monitored constituents.

PubMed

Joseph, John; Sharif, Hatim O; Sunil, Thankam; Alamgir, Hasanat

2013-07-01

The adverse health effects of high concentrations of ground-level ozone are well-known, but estimating exposure is difficult due to the sparseness of urban monitoring networks. This sparseness discourages the reservation of a portion of the monitoring stations for validation of interpolation techniques precisely when the risk of overfitting is greatest. In this study, we test a variety of simple spatial interpolation techniques for 8-h ozone with thousands of randomly selected subsets of data from two urban areas with monitoring stations sufficiently numerous to allow for true validation. Results indicate that ordinary kriging with only the range parameter calibrated in an exponential variogram is the generally superior method, and yields reliable confidence intervals. Sparse data sets may contain sufficient information for calibration of the range parameter even if the Moran I p-value is close to unity. R script is made available to apply the methodology to other sparsely monitored constituents. Copyright © 2013 Elsevier Ltd. All rights reserved.

Formation of Ozonic Compound and Used as Therapeutic Agent in Medicine

NASA Astrophysics Data System (ADS)

Zhu, Lei; Ye, Chunyong; Min, Xinmin

2018-03-01

It has some encouraging results to use ozone in medicine. However, as ozone is usually in gas state, unstable and strong oxidability, it is difficult to be stored and used commonly. Ozone, ethylene, acrylic acid and the ozonic compounds were calculated to study the interaction between ozone and carrier material to form ozonide. The stability of the ozonide, or the bond strength between ozone and ions of carrier are controlled felicitously to release ozone from the ozonide with proper velocity. Ozone antimicrobial has been composed on the above principle. It can be used conveniently, especially for common families. There are some characteristics of ozone antimicrobial or ozone, such as universal applicability, efficiency and rapidity, security, strong penetrability, no drug resistance and sterilization and treatment simultaneity.

Aromatic volatile organic compounds and their role in ground-level ozone formation in Russia

NASA Astrophysics Data System (ADS)

Berezina, E. V.; Moiseenko, K. B.; Skorokhod, A. I.; Elansky, N. F.; Belikov, I. B.

2017-05-01

This paper reports proton mass spectrometry data on aromatic volatile organic compounds (VOCs) (benzene, toluene, phenol, styrene, xylene, and propylbenzene) obtained in different Russian regions along the Trans-Siberian Railway from Moscow to Vladivostok, based on expedition data retrieved using the TRO-ICA-12 mobile laboratory in the summer of 2008. The contribution of aromatic VOCs to ozone formation in the cities and regions along the measurement route has been estimated quantitatively. The greatest contribution of aromatic VOCs to ozone formation is characteristic of large cities along the Trans-Siberian Railway (up to 7.5 ppbv O3) specified by the highest concentrations of aromatic VOCs (1-1.7 ppbv) and nitrogen oxides (>20 ppbv). The results obtained are indicative of a considerable contribution (30-50%) of anthropogenic emissions of VOCs to photochemical ozone generation in the large cities along the Trans-Siberian Railway in hot and dry weather against the background of a powerful natural factor such as isoprene emissions controlling the regional balance of ground-level ozone in warm seasons.

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.

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."

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.

Application of a photochemical grid model to milan metropolitan area

NASA Astrophysics Data System (ADS)

Silibello, C.; Calori, G.; Brusasca, G.; Catenacci, G.; Finzi, G.

High ozone levels are regularly reached during summer period in South-European urban areas, calling for careful design of primary pollutants emission reduction strategies. In this perspective the CALGRID modelling system has been applied to Milan metropolitan area, located in the Po Valley, the most industrialised and populated area in Italy. For the first modelling exercise, a simulation domain of 100×100 km 2 has been considered and a summer period, characterised by high photochemical activity, has been selected. Hourly emissions have been derived by spatially and temporally disaggregating national inventories data, while standard upper-air and ground-based meteorological data have been used as input to the CALMET pre-processor. A careful analysis of simulation results versus local network monitoring data has revealed some critical points, related to both modelling assumptions and practical data availability. A satisfactory reproduction of daytime ozone behaviour has been, in fact, accomplished, both in urban and suburban sites, while nighttime primary pollutants accumulations and consequent ozone consumption simulated by the model have not found correspondence in the measurements. Nitrogen dioxide has been also successfully modelled, mostly in city surroundings, whereas higher discrepancies have been found in some urban stations. Possible explanations of these facts are discussed in the paper, giving an insight for further work.

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.

Urban tropospheric ozone increases the prevalence of vitamin D deficiency among Belgian postmenopausal women with outdoor activities during summer.

PubMed

Manicourt, Daniel-Henri; Devogelaer, Jean-Pierre

2008-10-01

By absorbing sunlight UVB and thereby reducing cutaneous vitamin D photosynthesis, ozone, a common urban pollutant, could cause hypovitaminosis D. The objective of the study was to establish the characteristics and percentage of subjects with serum 25-hydroxyvitamin D [25(OH)D] less than 75 nmol/liter among postmenopausal women engaging in outdoor activities in either Brussels or the countryside. This was a cross-sectional study conducted in a university research hospital. Among 249 women consulting for either shoulder tendonitis or lumbar spine osteoarthritis, 121 free of conditions and drugs affecting bone and calcium metabolism completed two food-frequency questionnaires within 15 d and we selected the 85 subjects with retest scores within the +/- 15% of test scores. Other parameters included sun exposure index (SEI), PTH levels, and femoral neck T-score. Urban residents (n = 38) and rural residents (n = 47) did not differ in mean ages, body mass indices, and vitamin D intakes. When compared with rural inhabitants, urban inhabitants were exposed to ozone levels 3 times higher, and despite a higher mean SEI (113 vs. 87; P < 0.001), they had a higher prevalence of 25(OH)D less than 75 nmol/liter (84 vs. 38%). After adjusting for SEI, 25(OH)D was 2-fold higher in rural residents, and after adjusting for 25(OH)D, SEI was 3-fold higher in urban residents. Femoral neck T-scores correlated positively with 25(OH)D and negatively with PTH levels. Air pollution may be a neglected risk factor for hypovitaminosis D, which is known to compromise several health outcomes. As long as 25(OH)D is greater than 75 nmol/liter, calcium intakes greater than 17.5 mmol/d are unnecessary to prevent elevations in PTH levels.

The Southeastern Aerosol Research and Characterization (SEARCH) study: spatial variations and chemical climatology, 1999-2010.

PubMed

Blanchard, C L; Hidy, G M; Tanenbaum, S; Edgerton, E S; Hartsell, B E

2013-03-01

The Southeastern Aerosol Research and Characterization (SEARCH) study, which has been in continuous operation from 1999 to 2012, was implemented to investigate regional and urban air pollution in the southeastern United States. With complementary data from other networks, the SEARCH measurements provide key knowledge about long-term urban/nonurban pollution contrasts and regional climatology affecting inland locations and sites along the Gulf of Mexico coastline. Analytical approaches ranging from comparisons of mean concentrations to the application of air mass trajectories and principal component analysis provide insight into local and area-wide pollution. Gases (carbon monoxide, sulfur dioxide, nitrogen oxides, ozone, and ammonia), fine particle mass concentration, and fine particle species concentrations (including sulfate, elementary carbon, and organic carbon) are affected by a combination of regional conditions and local emission sources. Urban concentrations in excess of regional baselines and intraurban variations of concentrations depend on source proximity, topography, and local meteorological processes. Regional-scale pollution events (95th percentile concentrations) involving more than 6 of the 8 SEARCH sites are rare (< 2% of days), while subregional events affecting 4-6 sites occur on approximately 10% of days. Regional and subregional events are characterized by widely coincident elevated concentrations of ozone, sulfate, and particulate organic carbon, driven by persistent synoptic-scale air mass stagnation and higher temperatures that favor formation of secondary species, mainly in the summer months. The meteorological conditions associated with regional stagnation do not favor long-range transport of polluted air masses during episodes. Regional and subregional pollution events frequently terminate with southward and eastward penetration of frontal systems, which may initially reduce air pollutant concentrations more inland than along the Gulf Coast. Regional distribution of emission sources and synoptic-scale meteorological influences favoring stagnation lead to high regionwide pollution levels. The regional influence is greatest with secondary species, including ozone (03) particulate sulfate (SO4), and particulate organic matter, some of which is produced by atmospheric oxidation of volatile organic compounds (VOCs) from vegetation and anthropogenic sources. Other species, many of which are from primary emissions, are more influenced by local sources, especially within the Atlanta, GA, and Birmingham, AL, metropolitan areas. Limited measurements of modern and fossil total carbon point to the importance of biological and biogenic emissions in the Southeast.

Investigating the influence of photocatalytic cool wall adoption on meteorology and air quality in the Los Angeles basin

NASA Astrophysics Data System (ADS)

Zhang, J.; Tang, X.; Levinson, R.; Destaillats, H.; Mohegh, A.; Li, Y.; Tao, W.; Liu, J.; Ban-Weiss, G. A.

2017-12-01

Solar reflective "cool materials" can be used to lower urban temperatures, useful for mitigating the urban heat island effect and adapting to the local impacts of climate change. While numerous past studies have investigated the climate impacts of cool surfaces, few studies have investigated their effects on air pollution. Meteorological changes from increases in surface albedo can lead to temperature and transport induced modifications in air pollutant concentrations. In an effort to maintain high albedos in polluted environments, cool surfaces can also be made using photocatalytic "self-cleaning" materials. These photocatalytic materials can also remove NOx from ambient air, with possible consequences on ambient gas and particle phase pollutant concentrations. In this research, we investigate the impact of widespread deployment of cool walls on urban meteorology and air pollutant concentrations in the Los Angeles basin. Both photocatalytic and standard (not photocatalytic) high albedo wall materials are investigated. Simulations using a coupled meteorology-chemistry model (WRF-Chem) show that cool walls could effectively decrease urban temperatures in the Los Angeles basin. Preliminary results indicate that meteorology-induced changes from adopting standard cool walls could lead to ozone concentration reductions of up to 0.5 ppb. NOx removal induced by photocatalytic materials was modeled by modifying the WRF-Chem dry deposition scheme, with deposition rates informed by laboratory measurements of various commercially available materials. Simulation results indicate that increased deposition of NOx by photocatalytic materials could increase ozone concentrations, analogous to the ozone "weekend effect" in which reduced weekend NOx emissions can lead to increases in ozone. The impacts of cool walls on particulate matter concentrations are also discussed. Changes in particulate matter concentrations are found to be driven by albedo-induced changes in air pollutant transport in the basin, temperature induced changes in photochemistry and aerosol phase partitioning, and changes to secondary organic aerosol.

Nitryl chloride as a 'new' radical source and its role in production of ozone in polluted troposphere: an overview of the results from four field campaigns in China

NASA Astrophysics Data System (ADS)

Wang, Tao; Tham, Yee Jun; Xue, Likun; Wang, Zhe; Wang, Xinfeng; Wang, Weihao; Wang, Hao; Yun, Hui; Lu, Keding; Shao, Min; Louie, Peter K. K.; Blake, Donald R.; Brown, Steven S.; Zhang, Yuanhang

2016-04-01

Nitryl chloride (ClNO2) - a trace gas produced from heterogeneous reactions of dinitrogen pentoxide (N2O5) on aerosols containing chorine - can significantly affect radical budget and concentrations of ozone and other secondary pollutants. However, the abundance, formation kinetics, and impact of ClNO2are not fully understood under different environmental conditions. This presentation gives an overview of recent field campaigns of ClNO2 and related chemical constituents in China, including one at a mountain top (957 m a.s.l) in Hong Kong of South China in winter 2013 and three in North China (urban Ji'nan, semi-rural Wangdu, and Mt Tai (1534 m a.s.l)) in summer 2014. ClNO2 and N2O5 were measured with a chemical ionization mass spectrometry (CIMS) system with iodide as the primary ions. Ambient concentrations of several hundreds ppts and up to 4.7 ppbv of ClNO2were observed in these locations, suggesting existence of elevated ClNO2 in both coastal and inland atmospheres of China. Measurements in North China exhibited generally low concentrations of N2O5, indicative of its fast uptake of on aerosols under aerosol and humid conditions. Indications of anthropogenic sources of chloride were observed at all these sites. The impact of photolysis of ClNO2 on radical budget and ozone enhancement was assessed with a MCM model which was updated with detailed chlorine chemistry and constrained by measurement data for the southern and a northern site. The results show that the ClNO2 could increase ozone production by 2-16% in the following day. Overall, our study re-affirms the need to include ClNO2 related reactions in photochemical models for prediction of ground-level ozone in polluted environments.

DISINFECTION BY-PRODUCT FORMATION AND CONTROL BY OZONATION AND BIOTREATMENT

EPA Science Inventory

There is increasing interest in using ozone in water treatment because it is a strong disinfectant and is able to oxidize the precursors of some disinfection by-products (DBPs). However, ozonation itself produces DBPs, like aldehydes and ketones, and increases the concentration ...

Role of ozone and granular activated carbon in the removal of mutagenic compounds.

PubMed Central

Bourbigot, M M; Hascoet, M C; Levi, Y; Erb, F; Pommery, N

1986-01-01

The identification of certain organic compounds in drinking water has led water treatment specialists to be increasingly concerned about the eventual risks of such pollutants to the health of consumers. Our experiments focused on the role of ozone and granular activated carbon in removing mutagenic compounds and precursors that become toxic after chlorination. We found that if a sufficient dose of ozone is applied, its use does not lead to the creation of mutagenic compounds in drinking water and can even eliminate the initial mutagenicity of the water. The formation of new mutagenic compounds seems to be induced by ozonation that is too weak, although these mutagens can be removed by GAC filtration. Ozone used with activated carbon can be one of the best means for eliminating the compounds contributing to the mutagenicity of water. A combined treatment of ozone and activated carbon also decreases the chlorine consumption of the treated water and consequently reduces the formation of chlorinated organic compounds. PMID:3816720

Issues and progress in determining background ozone and particle concentrations

NASA Astrophysics Data System (ADS)

Pinto, J. P.

2011-12-01

Exposure to ambient ozone is associated with a variety of health outcomes ranging from mild breathing discomfort to mortality. For the purpose of health risk and policy assessments EPA evaluates the anthropogenic increase in ozone above background concentrations and has defined the North American (NA) background concentration of O3 as that which would occur in the U.S. in the absence of anthropogenic emissions of precursors in the U.S., Canada, and Mexico. Monthly average NA background ozone has been used to evaluate health risks, but EPA and state air quality managers must also estimate day specific ozone background levels for high ozone episodes as part of urban scale photochemical modeling efforts to support ozone regulatory programs. The background concentration of O3 is of more concern than other air pollutants because it typically represents a much larger fraction of observed O3 than do the backgrounds of other criteria pollutants (particulate matter (PM), CO, NO2, SO2). NA background cannot be determined directly from ambient monitoring data because of the influence of NA precursor emissions on formation of ozone within NA. Instead, estimates of NA background O3 have been based on GEOS-Chem using simulations in which NA anthropogenic precursor emissions are zeroed out. Thus, modeled NA background O3 includes contributions from natural sources of precursors (including CH4, NMVOCs, NOx, and CO) everywhere in the world, anthropogenic sources of precursors outside of NA, and downward transport of O3 from the stratosphere. Although monitoring data cannot determine NA background directly, measurements by satellites, aircraft, ozonesondes and surface monitors have proved to be highly useful for identifying sources of background O3 and for evaluating the performance of the GEOS-Chem model. Model simulated NA background concentrations are strong functions of location and season with large inter-day variability and with values increasing with elevation and higher in spring than in summer, and tend to be highest in the Intermountain West during spring. Estimates of annual average NA and other background definitions that have been considered will be presented. Issues associated with modeling background concentrations for both health-risk assessments and for episodic regulatory air quality programs will be discussed, and proposals for new atmospheric measurements and model improvements needed to quantify more accurately background contributions to ozone will also be presented. The views expressed are those of the author and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.

Nitrosamines in pilot-scale and full-scale wastewater treatment plants with ozonation.

PubMed

Gerrity, Daniel; Pisarenko, Aleksey N; Marti, Erica; Trenholm, Rebecca A; Gerringer, Fred; Reungoat, Julien; Dickenson, Eric

2015-04-01

Ozone-based treatment trains offer a sustainable option for potable reuse applications, but nitrosamine formation during ozonation poses a challenge for municipalities seeking to avoid reverse osmosis and high-dose ultraviolet (UV) irradiation. Six nitrosamines were monitored in full-scale and pilot-scale wastewater treatment trains. The primary focus was on eight treatment trains employing ozonation of secondary or tertiary wastewater effluents, but two treatment trains with chlorination or UV disinfection of tertiary wastewater effluent and another with full advanced treatment (i.e., reverse osmosis and advanced oxidation) were also included for comparison. N-nitrosodimethylamine (NDMA) and N-nitrosomorpholine (NMOR) were the most prevalent nitrosamines in untreated (up to 89 ng/L and 67 ng/L, respectively) and treated wastewater. N-nitrosomethylethylamine (NMEA) and N-nitrosodiethylamine (NDEA) were detected at one facility each, while N-nitrosodipropylamine (NDPrA) and N-nitrosodibutylamine (NDBA) were less than their method reporting limits (MRLs) in all samples. Ozone-induced NDMA formation ranging from <10 to 143 ng/L was observed at all but one site, but the reasons for the variation in formation remain unclear. Activated sludge, biological activated carbon (BAC), and UV photolysis were effective for NDMA mitigation. NMOR was also removed with activated sludge but did not form during ozonation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Secondary organic aerosol formation from ozone-initiated reactions with nicotine and secondhand tobacco smoke

NASA Astrophysics Data System (ADS)

Sleiman, Mohamad; Destaillats, Hugo; Smith, Jared D.; Liu, Chen-Lin; Ahmed, Musahid; Wilson, Kevin R.; Gundel, Lara A.

2010-11-01

We used controlled laboratory experiments to evaluate the aerosol-forming potential of ozone reactions with nicotine and secondhand smoke. Special attention was devoted to real-time monitoring of the particle size distribution and chemical composition of SOA as they are believed to be key factors determining the toxicity of SOA. The experimental approach was based on using a vacuum ultraviolet photon ionization time-of-flight aerosol mass spectrometer (VUV-AMS), a scanning mobility particle sizer (SMPS) and off-line thermal desorption coupled to mass spectrometry (TD-GC-MS) for gas-phase byproducts analysis. Results showed that exposure of SHS to ozone induced the formation of ultrafine particles (<100 nm) that contained high molecular weight nitrogenated species ( m/ z 400-500), which can be due to accretion/acid-base reactions and formation of oligomers. In addition, nicotine was found to contribute significantly (with yields 4-9%) to the formation of secondary organic aerosol through reaction with ozone. The main constituents of the resulting SOA were tentatively identified and a reaction mechanism was proposed to elucidate their formation. These findings identify a new component of thirdhand smoke that is associated with the formation of ultrafine particles (UFP) through oxidative aging of secondhand smoke. The significance of this chemistry for indoor exposure and health effects is highlighted.

High Spatial Resolution Thermal Remote Sensing of the Urban Heat Island Effect: Assessment of Risks to Human Health and Development of Mitigation Strategies for Sustainable Cities

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Luvall, Jeffrey C.; Rickman, Douglas L.; Estes, Maurice G., Jr.; Laymon, Charles A.; Crosson, William; Howell, Burgess F.; Gillani, Noor V.; Arnold, James E. (Technical Monitor)

2002-01-01

The growth of cities, both in population and in areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 80% of the world's population will live in cities. One of the more egregious side effects of urbanization is the deterioration in air quality as a result of increased vehicular traffic, industrialization and related activities. In the United States alone, under the more stringent air quality guidelines established by the U.S. Environmental Protection Agency (EPA) in 1997, nearly 300 counties in 34 states will not meet the new air quality standards for ground level ozone. The mitigation of one the physical/environmental characteristics of urbanization known as the urban heat island (UHI) effect, is now being looked at more closely as a possible way to bring down ground level ozone levels in cities and assist states in improving air quality. The UHI results from the replacement of "natural" land covers (e.g., trees, grass) with urban land surface types, such as pavement and buildings. Heat stored in these surfaces is released into the air and results in a "dome" of elevated air temperatures that presides over cities. The effect of this dome of elevated air temperatures is known as the UHI, which is most prevalent about 2-3 hours after sunset on days with intense solar radiation and calm winds. Given the local and regional impacts of the UHI, there are significant potential affects on human health, particularly as related to heat stress and ozone on body temperature regulation and on the cardiovascular and respiratory systems. In this study we are using airborne and satellite remote sensing data to analyze how differences in the urban landscape influence or drive the development of the UHI over four U.S. cities. Additionally, we are assessing what the potential impact is on risks to human health, and developing mitigation strategies to make urban areas more environmentally sustainable.

Remote Sensing of the Urban Heat Island Effect: Assessment of Risks to Human Health and Development of Mitigation Strategies for Sustainable Cities

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Luvall, Jeffrey C.; Rickman, Douglas L.; Estes, Maurice G., Jr.; Laymon, Charles A.; Crosson, William; Howell, Burgess F.; Gillani, Noor V.; Arnold, James E. (Technical Monitor)

2001-01-01

The growth of cities, both in population and in areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 80% of the world's population will live in cities. One of the more egregious side effects of urbanization is the deterioration in air quality as a result of increased vehicular traffic, industrialization and related activities. In the United States alone, under the more stringent air quality guidelines established by the U.S. Environmental Protection Agency (EPA) in 1997, nearly 300 counties in 34 states will not meet the new air quality standards for ground level ozone. The mitigation of one the physical/environmental characteristics of urbanization known as the urban heat island (UHI) effect, is now being looked at more closely as a possible way to bring down ground level ozone levels in cities and assist states in improving air quality. The UHI results from the replacement of "natural" land covers (e.g., trees, grass) with urban land surface types, such as pavement and buildings. Heat stored in these surfaces is released into the air and results in a "dome" of elevated air temperatures that presides over cities. The effect of this dome of elevated air temperatures is known as the UHI, which is most prevalent about 2-3 hours after sunset on days with intense solar radiation and calm winds. Given the local and regional impacts of the UHI, there are significant potential affects on human health, particularly as related to heat stress and ozone on body temperature regulation and on the cardiovascular and respiratory systems. In this study we are using airborne and satellite remote sensing data to analyze how differences in the urban landscape influence or drive the development of the UHI over four U.S. cities. Additionally, we are assessing what the potential impact is on risks to human health, and developing mitigation strategies to make urban areas more environmentally sustainable.

Trends of Rural Tropospheric Ozone at the Northwest of the Iberian Peninsula

PubMed Central

Saavedra, S.; Rodríguez, A.; Souto, J. A.; Casares, J. J.; Bermúdez, J. L.; Soto, B.

2012-01-01

Tropospheric ozone levels around urban and suburban areas at Europe and North America had increased during 80's–90's, until the application of NOx reduction strategies. However, as it was expected, this ozone depletion was not proportional to the emissions reduction. On the other hand, rural ozone levels show different trends, with peaks reduction and average increments; this different evolution could be explained by either emission changes or climate variability in a region. In this work, trends of tropospheric ozone episodes at rural sites in the northwest of the Iberian Peninsula were analyzed and compared to others observed in different regions of the Atlantic European coast. Special interest was focused on the air quality sites characterization, in order to guarantee their rural character in terms of air quality. Both episodic local meteorological and air quality measurements along five years were considered, in order to study possible meteorological influences in ozone levels, different to other European Atlantic regions. PMID:22649298

Trends of rural tropospheric ozone at the northwest of the Iberian Peninsula.

PubMed

Saavedra, S; Rodríguez, A; Souto, J A; Casares, J J; Bermúdez, J L; Soto, B

2012-01-01

Tropospheric ozone levels around urban and suburban areas at Europe and North America had increased during 80's-90's, until the application of NO(x) reduction strategies. However, as it was expected, this ozone depletion was not proportional to the emissions reduction. On the other hand, rural ozone levels show different trends, with peaks reduction and average increments; this different evolution could be explained by either emission changes or climate variability in a region. In this work, trends of tropospheric ozone episodes at rural sites in the northwest of the Iberian Peninsula were analyzed and compared to others observed in different regions of the Atlantic European coast. Special interest was focused on the air quality sites characterization, in order to guarantee their rural character in terms of air quality. Both episodic local meteorological and air quality measurements along five years were considered, in order to study possible meteorological influences in ozone levels, different to other European Atlantic regions.

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.

THE OZONE REACTION WITH BUTADIENE: FORMATION OF TOXIC PRODUCTS. (R826236)

EPA Science Inventory

Abstract

The formation yields of acrolein, 1,2-epoxy-3-butene and OH radicals have been measured from reaction of ozone with 1,3-butadiene at room temperature and atmosphere pressure. 1,3,5-Trimethyl benzene was added to scavenge OH radicals in measurements of product ...

Screening agrochemicals as potential protectants of plants against ozone phytotoxicity.

PubMed

Saitanis, Costas J; Lekkas, Dimitrios V; Agathokleous, Evgenios; Flouri, Fotini

2015-02-01

We tested seven contemporary agrochemicals as potential plant protectants against ozone phytotoxicity. In nine experiments, Bel-W3 tobacco plants were experienced weekly exposures to a) 80 nmol mol(-1) of ozone-enriched or ozone-free air in controlled environment chambers, b) an urban air polluted area, and c) an agricultural-remote area. Ozone caused severe leaf injury, reduced chlorophylls' and total carotenoids' content, and negatively affected photosynthesis and stomatal conductance. Penconazole, (35% ± 8) hexaconazole (28% ± 5) and kresoxim-methyl (28% ± 15) showed higher plants' protection (expressed as percentage; mean ± s.e.) against ozone, although the latter exhibited a high variability. Azoxystrobin (21% ± 15) showed lower protection efficacy and Benomyl (15% ± 9) even lower. Trifloxystrobin (7% ± 11) did not protect the plants at all. Acibenzolar-S-methyl + metalaxyl-M (Bion MX) (-6% ± 17) exhibited the higher variability and contrasting results: in some experiments it showed some protection while in others it intensified the ozone injury by causing phytotoxic symptoms on leaves, even in control plants. Copyright © 2014 Elsevier Ltd. All rights reserved.

Distribution ozone concentration in Klang Valley using GIS approaches

NASA Astrophysics Data System (ADS)

Sulaiman, A.; Rahman, A. A. Ab; Maulud, K. N. Abdul; Latif, M. T.; Ahmad, F.; Wahid, M. A. Abdul; Ibrahim, M. A.; Halim, N. D. Abdul

2017-05-01

Today, ozone has become one of the main air pollutants in Malaysia. The high ozone precursor concentrations have been encouraging the ozone production. The development of the Klang Valley, Malaysia has many types of physical activities such as urban commercial, industrial area, settlement area and others, which has increased the risk of atmospheric pollution. The purpose of this paper is to determine the spatial distribution between types of land use and ozone concentration that are occurred in the year 2014. The study areas for this paper include Shah Alam, Kajang, Petaling Jaya and Port Klang. Distribution of ozone concentration will be showed via spatial analysis tools in Geographic Information Systems (GIS) approached and the types of land use will be extracted using Remote Sensing technique. The result showed 97 ppb (parts-per-billion, 10-9) and 161 ppb recorded at Port Klang and Shah Alam respectively that are mainly represented by the settlement area. Therefore, the physical land use need to be monitor and controlled by the government in order to make sure the ozone production for daily per hour will not exceed the regulation allowed.

OZONE PRODUCTION FROM IRRADIATION OF ACETYLENE/CHLORINE MIXTURES IN AIR

EPA Science Inventory

The reaction of chlorine radicals with acetylene in air in the absence of oxides of nitrogen result In the formation of ozone. o ozone is observed when chlorine radicals react with methylacetylene or ethylacetylene under similar conditions. ormyl chloride is observed in all syste...

Forecasting ozone concentrations in the east of Croatia using nonparametric Neural Network Models

NASA Astrophysics Data System (ADS)

Kovač-Andrić, Elvira; Sheta, Alaa; Faris, Hossam; Gajdošik, Martina Šrajer

2016-07-01

Ozone is one of the most significant secondary pollutants with numerous negative effects on human health and environment including plants and vegetation. Therefore, more effort is made recently by governments and associations to predict ozone concentrations which could help in establishing better plans and regulation for environment protection. In this study, we use two Artificial Neural Network based approaches (MPL and RBF) to develop, for the first time, accurate ozone prediction models, one for urban and another one for rural area in the eastern part of Croatia. The evaluation of actual against the predicted ozone concentrations revealed that MLP and RBF models are very competitive for the training and testing data in the case of Kopački Rit area whereas in the case of Osijek city, MLP shows better evaluation results with 9% improvement in the correlation coefficient. Furthermore, subsequent feature selection process has improved the prediction power of RBF network.

Tropospheric ozone in the Nisqually River Drainage, Mount Rainier National Park

USGS Publications Warehouse

Peterson, D.L.; Bowers, Darci

1999-01-01

We quantified the summertime distribution of tropospheric ozone in the topographically complex Nisqually River drainage of Mount Rainier National Park from 1994 to 1997. Passive ozone samplers were used along an elevational transect to measure weekly average ozone concentrations ranging from 570 m to 2040 m elevation. Weekly average ozone concentrations were positively correlated with elevation, with the highest concentrations consistently measured at the highest sampling site (Panorama Point). Weekly average ozone concentrations at Mount Rainier National Park are considerably higher than those in the Seattle-Tacoma metropolitan area to the west. The anthropogenic contribution to ozone within the Nisqually drainage was evaluated by comparing measurements at this location with measurements from a 'reference' site in the western Olympic Mountains. The comparison suggests there is a significant anthropogenic source of ozone reaching the Cascade Range via atmospheric transport from urban areas to the west. In addition. temporal (week to week) variation in ozone distribution is synchronous within the Nisqually drainage, which indicates that subregional patterns are detectable with weekly averages. The Nisqually drainage is likely the 'hot spot' for air pollution in Mount Rainier National Park. By using passive ozone samplers in this drainage in conjunction with a limited number of continuous analyzers, the park will have a robust monitoring approach for measuring tropospheric ozone over time and protecting vegetative and human health.

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

PubMed

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

2010-02-01

The reaction of ozone with permethrin can potentially form phosgene. Published evidence on ozone levels and permethrin surface concentrations in aircraft cabins indicated that significant phosgene formation might occur in this setting. A derivatization technique was developed to detect phosgene with a lower limit of detection of 2 ppb. Chamber experiments were conducted with permethrin-coated materials (glass, carpet, seat fabric, and plastic) exposed to ozone under cabin-relevant conditions (150 ppb O(3), 4.5/h air exchange rate, <1% relative humidity, 1700 ng/cm(2) of permethrin). Phosgene was not detected in these experiments. Reaction of ozone with permethrin appears to be hindered by the electron-withdrawing chlorine atoms adjacent to the double bond in permethrin. Experimental results indicate that the upper limit on the reaction probability of ozone with surface-bound permethrin is approximately 10(-7). Extrapolation by means of material-balance modeling indicates that the upper limit on the phosgene level in aircraft cabins resulting from this chemistry is approximately 1 microg/m(3) or approximately 0.3 ppb. It was thus determined that phosgene formation, if it occurs in aircraft cabins, is not likely to exceed relevant, health-based phosgene exposure guidelines. Phosgene formation from ozone-initiated oxidation of permethrin in the aircraft cabin environment, if it occurs, is estimated to generate levels below the California Office of Environmental Health Hazard Assessment acute reference exposure level of 4 microg/m(3) or approximately 1 ppb.

Effect of Ozone Treatment on Nano-Sized Silver Sulfide in Wastewater Effluent.

PubMed

Thalmann, Basilius; Voegelin, Andreas; von Gunten, Urs; Behra, Renata; Morgenroth, Eberhard; Kaegi, Ralf

2015-09-15

Silver nanoparticles used in consumer products are likely to be released into municipal wastewater. Transformation reactions, most importantly sulfidation, lead to the formation of nanoscale silver sulfide (nano-Ag2S) particles. In wastewater treatment plants (WWTP), ozonation can enhance the effluent quality by eliminating organic micropollutants. The effect of ozonation on the fate of nano-Ag2S, however, is currently unknown. In this study, we investigate the interaction of ozone with nano-Ag2S and evaluate the effect of ozonation on the short-term toxicity of WWTP effluent spiked with nano-Ag2S. The oxidation of nano-Ag2S by ozone resulted in a stoichiometric factor (number of moles of ozone required to oxidize one mole of sulfide to sulfate) of 2.91, which is comparable to the results obtained for the reaction of bisulfide (HS(-)) with ozone. The second-order rate constant for the reaction of nano-Ag2S with ozone (k = 3.1 × 10(4) M(-1) s(-1)) is comparable to the rate constant of fast-reacting micropollutants. Analysis of the ozonation products of nano-Ag2S by transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) revealed that ozonation dominantly led to the formation of silver chloride in WWTP effluent. After ozonation of the Ag2S-spiked effluent, the short-term toxicity for the green algae Chlamydomonas reinhardtii increased and reached EC50 values comparable to Ag(+). This study thus reveals that ozone treatment of WWTP effluent results in the oxidation of Ag2S and, hence, an increase of the Ag toxicity in the effluent, which may become relevant at elevated Ag concentrations.

Photochemically consumed hydrocarbons and their relationship with ozone formation in two megacities of China

NASA Astrophysics Data System (ADS)

Chang, C.; Wang, J.; Liu, S.; Shao, M.; Zhang, Y.; Zhu, T.; Shiu, C.; Lai, C.

2010-12-01

Two on-site continuous measurements of ozone and its precursors in two megacities of China were carried out in an urban site of Beijing and a suburban site near Guangzhou in the Pearl River Delta (PRD) to estimate precursor consumption and to assess its relationship with oxidant (O3+NO2) formation level. An observation-based method (OBM) with the precursor consumption concept was adopted to assess the relationship between oxidant production and amounts of photochemically consumed non-methane hydrocarbons (NMHCs). In this approach, the ratio of ethylbenzene to m,p-xylenes was used to estimate the degree of photochemical processing, as well as the amounts of photochemically consumed NMHCs by reacting with OH. By trying to correlate the observed oxidant with the observed NMHC concentration, the two areas both revealed nearly no to low correlation between them. However, it existed fair to good correlations (R2=0.68 for Beijing, 0.53 for PRD) between the observed oxidant level and the degree of photochemical processing (ethylbenzene/m,p-xylenes). Furthermore, after taking the approach of consumption to estimate the consumed amounts of NMHCs, an interesting finding reveals that the definite correlation existed between the observed oxidant level and the total consumed NMHCs. The good correlations (R2=0.83 for Beijing, 0.81 for PRD) implies that the ambient oxidant level correlated to the amount of consumed NMHCs. The results of the two megacities in China by using the OBM with the precursor consumption concept can provide another pathway to explore the relationship between photochemically produced oxidant and consumed precursors, and will be helpful to validate model results and to reduce uncertainty of model predictions. However, the method has some room for uncertainty, as injection of fresh precursor emissions and additional boundary ozone involved, etc. could affect the estimation of consumed NMHCs and observed oxidant levels. Assistance of approaches in assessing the influence of the interfering factors would be helpful to acquire more reliable inferences of relationship between oxidant formation and precursor consumption.

Diagnostic Evaluation of Ozone Production and Horizontal Transport in a Regional Photochemical Air Quality Modeling System

EPA Science Inventory

A diagnostic model evaluation effort has been performed to focus on photochemical ozone formation and the horizontal transport process since they strongly impact the temporal evolution and spatial distribution of ozone (O₃) within the lower troposphere. Results from th...

Ozone: transport from an urban area and effects on infection of soybean and wild strawberry by bacterial plant pathogens

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

Laurence, J.A.

1976-01-01

Preliminary analysis of meteorological and ozone monitoring data indicate that ozone precursors, and at certain times, ozone can be transported to rural areas up to 75 kilometers from Minneapolis-St. Paul. Oxidant type symptoms have been observed on plants following these occurrences. Pseudomonas glycinea infection of Chippewa 64 soybeans was inhibited by exposure to high concentrations (490 ..mu..g/m/sup 3/, 4 hours) of ozone. In primary leaves, the inhibition lasted as long as non-fumigated leaves were susceptible to the bacterium. Inhibition of infection occured in both primary and trifoliolate leaves which had been exposed. Inhibition of infection occurrred in expanded trifoliolate leavesmore » which were exposed to ozone before expansion. At low concentrations of ozone (157 ..mu..g/m/sup 3/, 4 hours) similar trends were observed. Wild strawberry was sensitive to ozone at concentrations of 294 ..mu..g/m/sup 3/ (15 pphm) for 2 hours. Infection of wild strawberry by X. fragariae was inhibited when plants were exposed to high concentrations (392 ..mu..g/m/sup 3/, 3 hours) of ozone. Exposure to low concentrations (157 ..mu..g/m/sup 3/, 3 hours) did not result in consistent inhibition of infection.« less

Passive ozone network of Dallas: a modeling opportunity with community involvement. 2.

PubMed

Sather, M E; Varns, J L; Mulik, J D; Glen, G; Smith, L; Stallings, C

2001-11-15

Attaining the current lower tropospheric U.S. ozone standards continues to be a difficult task for many areas in the U.S. Concentrations of ozone above the standards negatively affects human health, agricultural crops, forests, and other ecosystem elements. This paper describes year two (1999) of a regional networking of passive and continuous ozone monitoring sites in the Dallas-Fort Worth (DFW) Metroplex region. The objectives of the second year of study were to (1) validate conclusions of the 1998 Passive Ozone Network of Dallas (POND) I study, (2) define the value of taking 12-h diurnal samples in addition to 24-h samples, and (3) add to the scientific knowledge base of rural/urban ozone comparison studies. Results of the POND II (1999) study demonstrated that ozone concentrations exceeding the new 8-h ozone standard could be recorded at least 130 km, or 80 miles, from the DFW Metroplex core in more rural areas. In addition, results of the POND II study indicated that ozone concentrations exceeding the 8-h standard probably occurred in areas recording a 12-h daytime ozone concentration above 60 parts per billion (ppb). The 12-h passive ozone data from POND II also suggests the relative magnitude of anthropogenic pollution influence could be assessed for rural passive ozone sites. The data from the POND II study provide modelers a rich database for future photochemical subgrid development for the DFW ozone nonattainment area. Indeed, the POND database provides a great amount of additional ozone ambient data covering 26 8-h and 13 1-h ozone standard exceedance days over an approximate 25000 km2 region. These data should help decrease uncertainties derived from future DFW ozone model exercises.

Rural southeast Texas air quality measurements during the 2006 Texas Air Quality Study.

PubMed

Schade, Gunnar W; Khan, Siraj; Park, Changhyoun; Boedeker, Ian

2011-10-01

The authors conducted air quality measurements of the criteria pollutants carbon monoxide, nitrogen oxides, and ozone together with meteorological measurements at a park site southeast of College Station, TX, during the 2006 Texas Air Quality Study II (TexAQS). Ozone, a primary focus of the measurements, was above 80 ppb during 3 days and above 75 ppb during additional 8 days in summer 2006, suggestive of possible violations of the ozone National Ambient Air Quality Standard (NAAQS) in this area. In concordance with other air quality measurements during the TexAQS II, elevated ozone mixing ratios coincided with northerly flows during days after cold front passages. Ozone background during these days was as high as 80 ppb, whereas southerly air flows generally provided for an ozone background lower than 40 ppb. Back trajectory analysis shows that local ozone mixing ratios can also be strongly affected by the Houston urban pollution plume, leading to late afternoon ozone increases of as high as 50 ppb above background under favorable transport conditions. The trajectory analysis also shows that ozone background increases steadily the longer a southern air mass resides over Texas after entering from the Gulf of Mexico. In light of these and other TexAQS findings, it appears that ozone air quality is affected throughout east Texas by both long-range and regional ozone transport, and that improvements therefore will require at least a regionally oriented instead of the current locally oriented ozone precursor reduction policies.

Satellite-Derived NO2 as an Indicator of Urban Air Quality and Emissions

NASA Astrophysics Data System (ADS)

Holloway, T.; Penn, E.; Harkey, M.

2016-12-01

Nitrogen dioxide (NO2) is the satellite-derived constituent with the most direct connection to fossil fuel emissions. At present the Ozone Monitoring Instrument aboard the NASA Aura satellite offers the highest resolution NO2retrievals, and new missions under development (TropOMI, TEMPO, GEMS, Sentinel-4) offer the potential for improved data in coming years. We present results applying satellite-derived NO2data to characterize air quality and emissions in U.S. cities. We highlight research findings geared toward increasing the relevance of satellite data to evaluate urban-scale air quality issues. This work reflects activities under the NASA Air Quality Applied Sciences Team (AQAST), and emerging work under the NASA Health and Air Quality Applied Sciences Team (H-AQAST). Among our results is a characterization of the diurnal cycle of nitrogen oxides using ground-based observations and satellite data. In situ monitoring from the U.S. EPA Air Quality System (AQS) shows that most locations have two daily peaks in NO2 (morning and evening) and a single daily peak in NO (morning). Spaced-based observations from the ESA Global Ozone Monitoring Experiment-2 (GOME-2), with a mid-morning overpass, and the NASA OMI, with an early afternoon overpass, support a complementary analysis for characterizing diurnal variability in NO2. Both ground-based monitors and satellite data show a reduction in the amplitude of the diurnal NO2 cycle. In the Western U.S., satellite data showed evidence of higher NO2 in urban centers in the afternoon (OMI) and higher NO2 in suburban areas in the morning (GOME-2), consistent with diurnal traffic patterns associated with commuting. Some power plants in the Western U.S. showed an increase in NO2in the afternoon, consistent with peak power demand associated with building air conditioning use. We extend this city-focused analysis satellite-derived HCHO:NO2 ratios as an indicator of ozone production regime, comparing modeled and measured ratios across major U.S. cities. Past studies have used the ratio of OMI HCHO to OMI NO2 to characterize whether ozone production in a particular location is NOx-limited or VOC-limited. We consider how this satellite-based ratio informs urban ozone chemistry across major U.S. cities.

Elimination of micropollutants and transformation products from a wastewater treatment plant effluent through pilot scale ozonation followed by various activated carbon and biological filters.

PubMed

Knopp, Gregor; Prasse, Carsten; Ternes, Thomas A; Cornel, Peter

2016-09-01

Conventional wastewater treatment plants are ineffective in removing a broad range of micropollutants, resulting in the release of these compounds into the aquatic environment, including natural drinking water resources. Ozonation is a suitable treatment process for micropollutant removal, although, currently, little is known about the formation, behavior, and removal of transformation products (TP) formed during ozonation. We investigated the elimination of 30 selected micropollutants (pharmaceuticals, X-ray contrast media, industrial chemicals, and TP) by biological treatment coupled with ozonation and, subsequently, in parallel with two biological filters (BF) or granular activated carbon (GAC) filters. The selected micropollutants were removed to very different extents during the conventional biological wastewater treatment process. Ozonation (specific ozone consumption: 0.87 ± 0.29 gO3 gDOC(-1), hydraulic retention time: 17 ± 3 min) eliminated a large number of the investigated micropollutants. Although 11 micropollutants could still be detected after ozonation, most of these were eliminated in subsequent GAC filtration at bed volumes (BV) of approximately 25,000 m(3) m(-3). In contrast, no additional removal of micropollutants was achieved in the BF. Ozonation of the analgesic tramadol led to the formation of tramadol-N-oxide that is effectively eliminated by GAC filters, but not by BF. For the antiviral drug acyclovir, the formation of carboxy-acyclovir was observed during activated sludge treatment, with an average concentration of 3.4 ± 1.4 μg L(-1) detected in effluent samples. Subsequent ozonation resulted in the complete elimination of carboxy-acyclovir and led to the formation of N-(4-carbamoyl-2-imino-5-oxo imidazolidin)-formamido-N-methoxyacetetic acid (COFA; average concentration: 2.6 ± 1.0 μg L(-1)). Neither the BF nor the GAC filters were able to remove COFA. These results highlight the importance of considering TP in the evaluation of advanced wastewater treatment processes. The results further indicate that post-treatment of ozonated wastewater with GAC filtration seems to be more suitable than BF, due to the sorption of formed TP to the activated carbon. Copyright © 2016 Elsevier Ltd. All rights reserved.

Deformation of the total ozone content field in the tropical zone

NASA Technical Reports Server (NTRS)

Vasilyev, Victor I.

1994-01-01

Presented are the ozone investigation results obtained in the tropical zone. Measurements of the total ozone content (TOC) were carried out by the ozonometer M-124. The ozonometer was automated to investigate the ozone intradiurnal variations and to increase precision of the TOC measurements. Obtained results allowed us to follow the effect of tropical cyclones (TC) on the TOC field. Several days before the TC formation the TOC increase is observed in daily mean course compared with the background one. Three types of trend can be singled out in the TOC intradiurnal course: zero, parabolic, quasi-linear. Maximum velocities of a trend are observed some days before the TC formation. Analogous harmonic constituents are mainly presented as spectrum of daily means of ozone, mean and absolute velocities of trend and dispersion as well as spectra of meteorological, hydrometeorological and actinometric values. Revealed is a number of day-to-day ozone variations concerned with large-scale circulations; moisture content in the atmosphere. Obtained are the data about short-period ozone waves (period less than a day). Thin-film silver sensors were used to measure the vertical ozone distribution (VOD). Atmospheric aerosol and VOD measurements were carried out simultaneously, they gave data of the VOD layered structure, where the VOD local minima coincided with the position of aerosol layers' maxima.

Characteristics of 1 year of observational data of VOCs, NOx and O3 at a suburban site in Guangzhou, China

NASA Astrophysics Data System (ADS)

Zou, Y.; Deng, X. J.; Zhu, D.; Gong, D. C.; Wang, H.; Li, F.; Tan, H. B.; Deng, T.; Mai, B. R.; Liu, X. T.; Wang, B. G.

2015-06-01

Guangzhou, one of China's megacities, is beset with frequent occurrence of high-concentration ozone events. In this study, online instruments were used to simultaneously monitor ozone, nitrogen oxides (NOx) and volatile organic compounds (VOCs) at GPACS (the Guangzhou Panyu Atmospheric Composition Station) of the China Meteorological Administration, from June 2011 to May 2012, in order to determine their characteristics, the effect of VOCs on ozone photochemical production and the relationship between VOC / NOx ratio and ozone formation. The results showed that during the observation period, the seasonal variation of ozone concentration was lower in spring and winter compared to summer and autumn, which is opposite that for VOCs and NOx. In terms of VOCs, aromatics had the largest ozone formation potential, among which toluene, xylenes, ethylbenzene, 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene were the most important species, with a total contribution of about 44%. As the VOC / NOx ratios were very high during high-concentration ozone events that occur all year round, we speculate ozone production was likely to be NOx-limited regime (12:00-16:00 LT) in Guangzhou. Further investigation based on numerical models is needed in the future to obtain more detailed and robust conclusions.

Analysis of TES Satellite Ozone Observations from 2005 to 2013 to Understand Global Air Pollution Transport

NASA Astrophysics Data System (ADS)

Kladar, R. M.; Cooper, O. R.

2015-12-01

To better understand the causes of ozone formation and transport, we create and analyze global satellite ozone retrieval products for ground level to upper tropospheric ozone concentrations over the years 2005 to 2013 using the Tropospheric Emission Spectrometer (TES) that rides aboard the NASA Aura satellite. Many global and regional tropospheric ozone trends are not fully understood. Observing many different pressure levels between 1000 hPa to 215 hPa, we focus on the areas where model and other observation strategies disagree, namely the Arabian Peninsula, the Australian outback, and the southern Sahara. We observe (and these areas may be experiencing) unusually high ozone concentrations. We also comment on the historically high ozone areas such as China, Northern India, western Europe, and the western and southern United States and how known phenomena compare to our observations. Many observations confirm known mechanisms of ozone formation and transport, such as the effect of the yearly monsoon cycle in South, Southeast, and East Asia. Others, such as the surprisingly high monthly average concentrations on the Arabian Peninsula and Southern Sahara, deserve more thorough investigation. Several hypotheses for these disagreement areas are put forward here. Lastly, we comment on the usefulness of the TES instrument for trends analysis and future global observations.

Emissions of terpenoids, benzenoids, and other biogenic gas-phase organic compounds from agricultural crops and their potential implications for air quality

NASA Astrophysics Data System (ADS)

Gentner, D. R.; Ormeño, E.; Fares, S.; Ford, T. B.; Weber, R.; Park, J.-H.; Brioude, J.; Angevine, W. M.; Karlik, J. F.; Goldstein, A. H.

2014-06-01

Agriculture comprises a substantial, and increasing, fraction of land use in many regions of the world. Emissions from agricultural vegetation and other biogenic and anthropogenic sources react in the atmosphere to produce ozone and secondary organic aerosol, which comprises a substantial fraction of particulate matter (PM2.5). Using data from three measurement campaigns, we examine the magnitude and composition of reactive gas-phase organic carbon emissions from agricultural crops and their potential to impact regional air quality relative to anthropogenic emissions from motor vehicles in California's San Joaquin Valley, which is out of compliance with state and federal standards for tropospheric ozone PM2.5. Emission rates for a suite of terpenoid compounds were measured in a greenhouse for 25 representative crops from California in 2008. Ambient measurements of terpenoids and other biogenic compounds in the volatile and intermediate-volatility organic compound ranges were made in the urban area of Bakersfield and over an orange orchard in a rural area of the San Joaquin Valley during two 2010 seasons: summer and spring flowering. We combined measurements from the orchard site with ozone modeling methods to assess the net effect of the orange trees on regional ozone. When accounting for both emissions of reactive precursors and the deposition of ozone to the orchard, the orange trees are a net source of ozone in the springtime during flowering, and relatively neutral for most of the summer until the fall, when it becomes a sink. Flowering was a major emission event and caused a large increase in emissions including a suite of compounds that had not been measured in the atmosphere before. Such biogenic emission events need to be better parameterized in models as they have significant potential to impact regional air quality since emissions increase by several factors to over an order of magnitude. In regions like the San Joaquin Valley, the mass of biogenic emissions from agricultural crops during the summer (without flowering) and the potential ozone and secondary organic aerosol formation from these emissions are on the same order as anthropogenic emissions from motor vehicles and must be considered in air quality models and secondary pollution control strategies.

THE GAS PHASE REACTION OF OZONE WITH 1,3-BUTADIENE: FORMATION YIELDS OF SOME TOXIC PRODUCTS. (R826236)

EPA Science Inventory

The formation yields of acrolein, 1,2-epoxy-3-butene and OH radicals have been measured from reaction of ozone with 1,3-butadiene at room temperature and atmosphere pressure. 1,3,5-Trimethyl benzene was added to scavenge OH radicals in measurements of product yields. In separa...

Analysis of air quality with numerical simulation (CMAQ), and observations of trace gases

NASA Astrophysics Data System (ADS)

Castellanos, Patricia

Ozone, a secondary pollutant, is a strong oxidant that can pose a risk to human health. It is formed from a complex set of photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs). Ambient measurements and air quality modeling of ozone and its precursors are important tools for support of regulatory decisions, and analyzing atmospheric chemical and physical processes. I worked on three methods to improve our understanding of photochemical ozone production in the Eastern U.S.: a new detector for NO2, a numerical experiment to test the sensitivity to the timing to emissions, and comparison of modeled and observed vertical profiles of CO and ozone. A small, commercially available cavity ring-down spectroscopy (CRDS) NO2 detector suitable for surface and aircraft monitoring was modified and characterized. The CRDS detector was run in parallel to an ozone chemiluminescence device with photolytic conversion of NO2 to NO. The two instruments measured ambient air in suburban Maryland. A linear least-squares fit to a direct comparison of the data resulted in a slope of 0.960+/-0.002 and R of 0.995, showing agreement between two measurement techniques within experimental uncertainty. The sensitivity of the Community Multiscale Air Quality (CMAQ) model to the temporal variation of four emissions sectors was investigated to understand the effect of emissions' daily variability on modeled ozone. Decreasing the variability of mobile source emissions changed the 8-hour maximum ozone concentration by +/-7 parts per billion by volume (ppbv). Increasing the variability of point source emissions affected ozone concentrations by +/-6 ppbv, but only in areas close to the source. CO is an ideal tracer for analyzing pollutant transport in AQMs because the atmospheric lifetime is longer than the timescale of boundary layer mixing. CO can be used as a tracer if model performance of CO is well understood. An evaluation of CO model performance in CMAQ was carried out using aircraft observations taken for the Regional Atmospheric Measurement, Modeling and Prediction Program (RAMMPP) in the summer of 2002. Comparison of modeled and observed CO total columns were generally in agreement within 5-10%. There is little evidence that the CO emissions inventory is grossly overestimated. CMAQ predicts the same vertical profile shape for all of the observations, i.e. CO is well mixed throughout the boundary layer. However, the majority of observations have poorly mixed air below 500 m, and well mixed air above. CMAQ appears to be transporting CO away from the surface more quickly than what is observed. Turbulent mixing in the model is represented with K-theory. A minimum Kz that scales with fractional urban land use is imposed in order to account for subgrid scale obstacles in urban areas and the urban heat island effect. Micrometeorological observations suggest that the minimum Kz is somewhat high. A sensitivity case where the minimum K z was reduced from 0.5 m2/s to 0.1 m2/s was carried out. Model performance of surface ozone observations at night increased significantly. The model better captures the observed ozone minimum with slower mixing, and increases ozone concentrations in the residual layer. Model performance of CO and ozone morning vertical profiles improves, but the effect is not large enough to bring the model and measurements into agreement. Comparison of modeled CO and O3 vertical profiles shows that turbulent mixing (as represented by eddy diffusivity) appears to be too fast, while convective mixing may be too slow.

Ozone formation during an episode over Europe: A 3-D chemical/transport model simulation

NASA Technical Reports Server (NTRS)

Berntsen, Terje; Isaksen, Ivar S. A.

1994-01-01

A 3-D regional photochemical tracer/transport model for Europe and the Eastern Atlantic has been developed based on the NASA/GISS CTM. The model resolution is 4x5 degrees latitude and longitude with 9 layers in the vertical (7 in the troposphere). Advective winds, convection statistics and other meteorological data from the NASA/GISS GCM are used. An extensive gas-phase chemical scheme based on the scheme used in our global 2D model has been incorporated in the 3D model. In this work ozone formation in the troposphere is studied with the 3D model during a 5 day period starting June 30. Extensive local ozone production is found and the relationship between the source regions and the downwind areas are discussed. Variations in local ozone formation as a function of total emission rate, as well as the composition of the emissions (HC/NO(x)) ratio and isoprene emissions) are elucidated. An important vertical transport process in the troposphere is by convective clouds. The 3D model includes an explicit parameterization of this process. It is shown that this process has significant influence on the calculated surface ozone concentrations.

Nitrogen Oxides in the Nocturnal Boundary Layer: Chemistry of Nitrous Acid (HONO) and the Nitrate Radical (N03)

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

Jochen Stutz

Summary Chemical processes occurring at night in the lowest part of the urban atmosphere, the so called nocturnal boundary layer (NBL), can influence the composition of the atmosphere during the night as well as the following day. They may impact the budgets of some of the most important pollutants, such as ozone and nitrogen oxides, as well as influence size and composition of particular matter. Few studies have thus far concentrated on the nocturnal chemistry of the urban NBL, most likely due to the strong influence of vertical transport and mixing, which requires the measurement of trace gas profiles insteadmore » of simple point observations. Motivated by our lack of observations and understanding of nocturnal chemistry, the focus of this project was the study of the vertical distribution of trace gases and the altitude dependence of nocturnal chemistry under polluted conditions through field observations and modeling studies. The analysis of three field experiments (TEXAQS, Houston, 2000; Phoenix Sunrise Ozone Experiment, 2001; NAPOX, Boston, 2002), two of which were performed in this project, showed that ozone concentrations typically increase with height in the lowest 150m, while NO2 typically decreases. NO3, the dominant nocturnal radical species, showed much higher concentrations in the upper part of the NBL, and was often not present at the ground. With the help of a one-dimensional chemical transport model, developed in this project, we found that the interaction of ground emissions of NOx and hydrocarbons, together with their vertical transport, is responsible for the vertical profiles. The dominant chemical reactions influencing ozone, NO2 and NO3 are the reaction of ozone and NO3 with freshly emitted NO. Sensitivity studies with our model showed that the magnitude of the trace gas gradients depend both on the emission rates and the vertical stability of the NBL. Observations and model analysis clearly show that nocturnal chemistry in urban areas is altitude dependent. Measurements at one altitude, for example at the ground, where most air quality monitoring stations are located, are not representative for the rest of the NBL. Our model also revealed that radical chemistry is, in general, altitude dependent at night. We distinguish three regions: an unreactive, NO rich, ground layer; an upper, O3 and NO3 dominated layer, and a reactive mixing layer, where RO2 radicals are mixed from aloft with NO from the ground. In this reactive layer an active radical chemistry and elevated OH radical levels can be found. The downward transport of N2O5 and HO2NO2, followed by their thermal decay, was also identified as a radical source in this layer. Our observations also gave insight into the formation of HONO in the NBL. Based on our field experiments we were able to show that the NO2 to HONO conversion was relative humidity dependent. While this fact was well known, we found that it is most likely the uptake of HONO onto surfaces which is R.H. dependent, rather than the NO2 to HONO conversion. This finding led to the proposal of a new NO2 to HONO conversion mechanism, which is based on solid physical chemical principles. Noteworthy is also the observation of enhanced NO2 to HONO conversion during a dust storm event in Phoenix. The final activity in our project investigated the influence of the urban canopy, i.e. building walls and surfaces, on nocturnal chemistry. For the first time the surface area of a city was determined based on a Geographical Information System database of the city of Santa Monica. The surface to volume areas found in this study showed that, in the 2 lower part of the NBL, buildings provide a much larger surface area than the aerosol. In addition, buildings take up a considerable amount of the volume near the ground. The expansion of our model and sensitivity studies based on the Santa Monica data revealed that the surface area of buildings considerably influences HONO levels in urban areas. The volume reduction leads to a decrease of O3 and an increase of NO2 near the ground due to the stronger impact of NO emissions. Our project shows that the urban canopy should be included in future air quality models to better represent nocturnal chemistry. This project has considerably advanced our understanding of the chemistry of the urban nocturnal boundary layer. The results of this project have implications for air quality studies in the urban nocturnal boundary layer. The study has also identified new questions on nocturnal processes, which we will continue to address through other projects.« less

Lidar Remote Sensing for Industry and Environment Monitoring

NASA Technical Reports Server (NTRS)

Singh, Upendra N. (Editor); Itabe, Toshikazu (Editor); Sugimoto, Nobuo (Editor)

2000-01-01

Contents include the following: 1. Keynote paper: Overview of lidar technology for industrial and environmental monitoring in Japan. 2. lidar technology I: NASA's future active remote sensing mission for earth science. Geometrical detector consideration s in laser sensing application (invited paper). 3. Lidar technology II: High-power femtosecond light strings as novel atmospheric probes (invited paper). Design of a compact high-sensitivity aerosol profiling lidar. 4. Lasers for lidars: High-energy 2 microns laser for multiple lidar applications. New submount requirement of conductively cooled laser diodes for lidar applications. 5. Tropospheric aerosols and clouds I: Lidar monitoring of clouds and aerosols at the facility for atmospheric remote sensing (invited paper). Measurement of asian dust by using multiwavelength lidar. Global monitoring of clouds and aerosols using a network of micropulse lidar systems. 6. Troposphere aerosols and clouds II: Scanning lidar measurements of marine aerosol fields at a coastal site in Hawaii. 7. Tropospheric aerosols and clouds III: Formation of ice cloud from asian dust particles in the upper troposphere. Atmospheric boundary layer observation by ground-based lidar at KMITL, Thailand (13 deg N, 100 deg. E). 8. Boundary layer, urban pollution: Studies of the spatial correlation between urban aerosols and local traffic congestion using a slant angle scanning on the research vessel Mirai. 9. Middle atmosphere: Lidar-observed arctic PSC's over Svalbard (invited paper). Sodium temperature lidar measurements of the mesopause region over Syowa Station. 10. Differential absorption lidar (dIAL) and DOAS: Airborne UV DIAL measurements of ozone and aerosols (invited paper). Measurement of water vapor, surface ozone, and ethylene using differential absorption lidar. 12. Space lidar I: Lightweight lidar telescopes for space applications (invited paper). Coherent lidar development for Doppler wind measurement from the International Space Station. 13. Space lidar II: Using coherent Doppler lidar to estimate river discharge. 14. Poster session: Lidar technology, optics for lidar. Laser for lidar. Middle atmosphere observations. Tropospheric observations (aerosols, clouds). Boundary layer, urban pollution. Differential absorption lidar. Doppler lidar. and Space lidar.

Formation of N-nitrosodimethylamine (NDMA) by ozonation of dyes and related compounds.

PubMed

Oya, Masami; Kosaka, Koji; Asami, Mari; Kunikane, Shoichi

2008-12-01

Formation of N-nitrosodimethylamine (NDMA) by ozonation of commercially available dyes and related compounds was investigated. Ozonation was conducted using a semi-batch type reactor, and ozone concentration in gas phase and the ozone gas flow were 10 mg L(-1) and 1.0 L min(-1), respectively. NDMA was formed by 15 min of ozonation of seven out of eight selected target compounds (0.05 mM) at pH 7. All the target compounds with N,N-dimethylamino functions were NDMA precursors in ozonation. The lowest and highest NDMA concentrations after ozonation of the target compounds were 13 ng L(-1) for N,N-dimethylformamide (DMF) and 1600 ng L(-1) for N,N-dimethyl-p-phenylenediamine (DMPD), respectively. NDMA concentrations after 15 min of ozonation of 0.05 mM methylene blue (MB) and DMPD increased with an increase in pH in its range of 6-8. The effects of coexisting compounds on NDMA concentrations after 15 min of ozonation of 0.05 mM MB and DMPD were examined at pH 7. NDMA concentrations after ozonation of MB and DMPD increased by the presence of 0.05 mM (0.7 mg L(-1) as N) nitrite (NO(2)(-)); 5000 ng L(-1) for MB and 4000 ng L(-1) for DMPD. NDMA concentration after MB ozonation decreased by the presence of 5mM tertiary butyl alcohol (TBA), a hydroxyl radical (HO.) scavenger, but that after DMPD ozonation was increased by the presence of TBA. NDMA concentrations after ozonation of MB and DMPD were not affected by the presence of 0.16 mM (5.3 mg L(-1)) hydrogen peroxide (H(2)O(2)). When 0.05 mM MB and DMPD were added to the Yodo and Tone river water samples, NDMA concentrations after 15 min of their ozonation at pH 7 increased compared with those in the case of addition to ultrapure water samples.

Changes in air quality and tropospheric composition due to depletion of stratospheric ozone and interactions with climate.

PubMed

Tang, X; Wilson, S R; Solomon, K R; Shao, M; Madronich, S

2011-02-01

Air pollution will be directly influenced by future changes in emissions of pollutants, climate, and stratospheric ozone, and will have significant consequences for human health and the environment. UV radiation is one of the controlling factors for the formation of photochemical smog, which includes tropospheric ozone (O(3)) and aerosols; it also initiates the production of hydroxyl radicals (˙OH), which control the amount of many climate- and ozone-relevant gases (e.g., methane and HCFCs) in the atmosphere. Numerical models predict that future changes in UV radiation and climate will modify the trends and geographic distribution of ˙OH, thus affecting the formation of photochemical smog in many urban and regional areas. Concentrations of ˙OH are predicted to decrease globally by an average of 20% by 2100, with local concentrations varying by as much as a factor of two above and below current values. However, significant differences between modelled and measured values in a limited number of case studies show that chemistry of hydroxyl radicals in the atmosphere is not fully understood. Photochemically produced tropospheric ozone is projected to increase. If emissions of anthropogenic air pollutants from combustion of fossil fuels, burning of biomass, and agricultural activities continue to increase, concentrations of tropospheric O(3) will tend to increase over the next 20-40 years in certain regions of low and middle latitudes because of interactions of emissions, chemical processes, and climate change. Climate-driven increases in temperature and humidity will also increase production of tropospheric O(3) in polluted regions, but reduce it in more pristine regions. Higher temperatures tend to increase emissions of nitrogen oxides (NO(x)) from some soils and release of biogenic volatile organic compounds (VOCs) from vegetation, leading to greater background concentrations of ozone in the troposphere. The net effects of future changes in UV radiation, meteorological conditions, and anthropogenic emissions may be large, thus posing challenges for prediction and management of air quality. Aerosols composed of organic substances have a major role in both climate and air quality, and contribute a large uncertainty to the energy budget of the atmosphere. These aerosols are mostly formed via the UV-initiated oxidation of VOCs from anthropogenic and biogenic sources, although the details of the chemistry are still poorly understood and current models under-predict their abundance. A better understanding of their formation, chemical composition, and optical properties is required to assess their significance for air quality and to better quantify their direct and indirect radiative forcing of climate. Emissions of compounds containing fluorine will continue to have effects on the chemistry of the atmosphere and on climate change. The HCFCs and HFCs used as substitutes for ozone-depleting CFCs can break down into trifluoroacetic acid (TFA), which will accumulate in oceans, salt lakes, and playas. Based on historical use and projections of future uses, including new products entering the market, such as the fluoro-olefins, increased loadings of TFA in these environmental sinks will be small. Even when added to existing amounts from natural sources, risks to humans or the environment from the historical use of CFCs or continued use of their replacements is judged to be negligible.

What Air Quality Models Tell Us About Sources and Sinks of Atmospheric Aldehydes

NASA Astrophysics Data System (ADS)

Luecken, D.; Hutzell, W. T.; Phillips, S.

2010-12-01

Atmospheric aldehydes play important roles in several aspects of air quality: they are critical radical sources that drive ozone formation, they are hazardous air pollutants that are national drivers for cancer risk, they participate in aqueous chemistry and potentially aerosol formation, and are key species for evaluating the accuracy of isoprene emissions. For these reasons, it is important to accurately understand their sources and sinks, and the sensitivity of their concentrations to emission controls. While both compounds have been included in air quality modeling for many years, current, state-of-the-science chemical mechanisms have difficulty reproducing measured values of aldehydes, which calls into question the robustness of ozone, HAPs and aerosol predictions. In the past, we have attributed discrepancies to measurement errors, inventory errors, or the focus on high-NOx urban regimes. Despite improvements in all of these areas, the measurements still diverge from model predictions, with formaldehyde often underpredicted by 50% and acetaldehyde showing a large degree of scatter - from 20% overprediction to 50% underprediction. To better examine the sources of aldehydes, we implemented the new SAPRC07T mechanism in the Community Multi-Scale Air Quality (CMAQ) model. This mechanism incorporates current recommendations for kinetic data and has the most detailed representation of product formation under a wide variety of conditions of any mechanism used in regional air quality models. We use model simulations to pinpoint where and when aldehyde concentrations tend to deviate from measurements. We demonstrate the role of secondary production versus primary emissions in aldehdye concentrations and find that secondary sources produce the largest deviations from measurements. We identify which VOCs are most responsible for aldehyde secondary production in the areas of the U.S. where the largest health effects are seen, and discuss how this affects consideration of control strategies.

Volatile organic compound mixing ratios above Beijing in November and December 2016

NASA Astrophysics Data System (ADS)

Acton, William; Shaw, Marvin; Huang, Zhonghui; Wang, Zhaoyi; Wang, Xinming; Zhang, Yanli; Davison, Brian; Langford, Ben; Mullinger, Neil; Nemitz, Eiko; Fu, Pingqing; Squires, Freya; Carpenter, Lucy; Lewis, Alastair; Hewitt, Nick

2017-04-01

Volatile organic compounds (VOCs) are emitted into the atmosphere from vegetation and anthropogenic sources such as fossil fuel combustion, biomass burning and the evaporation of petroleum products. These compounds play an important role in the chemistry of the lower atmosphere through secondary organic aerosol (SOA) formation and facilitating the formation of tropospheric ozone. As well as their indirect impact on human health via the formation of ozone and SOA, some VOCs, including benzene, directly affect human health adversely. Here we report VOC mixing ratios measured in Beijing during a 5 week intensive field campaign from the 7th November to the 10th December 2016. This work was carried out as part of the Sources and Emissions of Air Pollutants in Beijing (AIRPOLL-Beijing) work project within the Air Pollution and Human Health in a Developing Megacity (APHH-Beijing) research programme. APHH is a large multi-institutional study which aims to record the concentrations and identify the sources of urban air pollutants in Beijing, determine exposure, understand their effects on human health, and to identify solutions. VOC mixing ratios were recorded using a Proton Transfer Reaction-Time of Flight-Mass Spectrometer (PTR-ToF-MS, Ionicon Analytik) and a Selected Ion Flow Tube-Mass Spectrometer (SIFT-MS, SYFT Technologies). During the measurement period Beijing was subject to multiple pollution events that alternated with periods of relatively good air quality, allowing the VOCs within the polluted air masses to be identified and quantified. VOCs were sampled at 102 m with additional gradient measurements made at 3, 15, 32 and 64 m providing a vertical profile of VOC mixing ratios. Mixing ratios of methanol, acetonitrile, acetaldehyde, acetone, isoprene and aromatics species will be reported together with a discussion of potential sources. Comparisons will then be drawn with other large cities.

Estimating the Tropospheric Ozone Distribution by the Assimilation of Satellite Data

NASA Technical Reports Server (NTRS)

Hayashi, Hiroo; Stajner, Ivanka; Winslow, Nathan; Jones, Dylan B. A.; Pawson, Steven; Thompson, Anne M.

2003-01-01

Tropospheric ozone is important to the environment, because it acts as a strong oxidant to control the concentrations of many reduced gases (methane, carbon monoxide, ... ), its radiative forcing plays a significant role in the greenhouse effect, and direct contact with ozone is harmful to human health. Tropospheric ozone, whose main sources are intrusion from the stratosphere and chemical production from source gases associated with urban pollution or biomass burning, varies on a wide range of spatial and temporal scales. Its transport and chemistry can be influenced by weather, seasonal, or multiannual variability. Despite the importance of tropospheric ozone, it contributes only about 10% of the total ozone loading in the atmosphere. Consequently, satellite instruments lose sensitivity below the stratospheric ozone peak, and provide little information about middle and lower tropospheric ozone. This talk will discuss recent modifications made to the satellite ozone data assimilation system at NASA's Data Assimilation Office (DAO) in order to provide better tropospheric ozone columns and profiles. We use a version of the system that assimilates only the data from the Solar Backscatter UltraViolet/2 (SBUV/2) instrument. The quality of the assimilated ozone in the tropical troposphere is evaluated by comparison with independent observations obtained from the Southern Hemispheric Additional Ozonesondes (SHADOZ) network. It is shown that the quality of ozone fields is sensitive to the winds used in the transport model. Increasing the vertical resolution of the model also has a beneficial impact. The assimilated ozone in the lower troposphere was substantially improved by inclusion of tropospheric ozone production, loss, and dry deposition rates from the Harvard GEOS-CHEM model. The mechanisms behind these results will be examined and the implications for our understanding of tropospheric ozone will be discussed.

Use of AIRS, OMI, MLS, and TES Data in Assessing Forest Ecosystem Exposure to Ozone

NASA Technical Reports Server (NTRS)

Spruce, Joseph P.

2007-01-01

Ground-level ozone at high levels poses health threats to exposed flora and fauna, including negative impacts to human health. While concern is common regarding depletion of ozone in the stratosphere, portions of the urban and rural United States periodically have high ambient levels of tropospheric ozone on the ground. Ozone pollution can cause a variety of impacts to susceptible vegetation (e.g., Ponderosa and Jeffrey pine species in the southwestern United States), such as stunted growth, alteration of growth form, needle or leaf chlorosis, and impaired ability to withstand drought-induced water stress. In addition, Southern Californian forests with high ozone exposures have been recently subject to multiyear droughts that have led to extensive forest overstory mortality from insect outbreaks and increased incidence of wildfires. Residual forests in these impacted areas may be more vulnerable to high ozone exposures and to other forest threats than ever before. NASA sensors collect a wealth of atmospheric data that have been used recently for mapping and monitoring regional tropospheric ozone levels. AIRS (Atmospheric Infrared Sounder), OMI (Ozone Monitoring Instrument), MLS (Microwave Limb Sounder), and TES (Tropospheric Emission Spectrometer) data could be used to assess forest ecosystem exposure to ozone. Such NASA data hold promise for providing better or at least complementary synoptic information on ground-level ozone levels that Federal agency partners can use to assess forest health trends and to mitigate the threats as needed in compliance with Federal laws and mandates. NASA data products on ozone concentrations may be able to aid applications of DSTs (decision support tools) adopted by the USDA FS (U.S. Department of Agriculture Forest Service) and by the NPS (National Park Service), such as the Ozone Calculator, in which ground ozone estimates are employed to assess ozone impacts to forested vegetation.

Spatial Growth Modeling and High Resolution Remote Sensing Data Coupled with Air Quality Modeling to Assess the Impact of Atlanta, Georgia on the Local and Regional Environment

NASA Technical Reports Server (NTRS)

Quattrochi, Dale A.; Estes, Maurice G., Jr.; Crosson, William; Johnson, Hoyt; Khan, Maudood

2006-01-01

The growth of cities, both in population and areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 60 percent of the world s population will live in cities. Urban expansion has profound impacts on a host of biophysical, environmental, and atmospheric processes within an urban ecosystems perspective. A reduction in air quality over cities is a major result of these impacts. Because of its complexity, the urban landscape is not adequately captured in air quality models such as the Community Multiscale Air Quality (CMAQ) model that is used to assess whether urban areas are in attainment of EPA air quality standards, primarily for ground level ozone. This inadequacy of the CMAQ model to sufficiently respond to the heterogeneous nature of the urban landscape can impact how well the model predicts ozone levels over metropolitan areas and ultimately, whether cities exceed EPA ozone air quality standards. We are exploring the utility of high-resolution remote sensing data and urban spatial growth modeling (SGM) projections as improved inputs to a meteorological/air quality modeling system focusing on the Atlanta, Georgia metropolitan area as a case study. These growth projections include business as usual and smart growth scenarios out to 2030. The growth projections illustrate the effects of employing urban heat island mitigation strategies, such as increasing tree canopy and albedo across the Atlanta metro area, which in turn, are used to model how air temperature can potentially be moderated as impacts on elevating ground-level ozone, as opposed to not utilizing heat island mitigation strategies. The National Land Cover Dataset at 30m resolution is being used as the land use/land cover input and aggregated to the 4km scale for the MM5 mesoscale meteorological model and the CMAQ modeling schemes. Use of these data has been found to better characterize low density/suburban development as compared with USGS lkm land use/land cover data that have traditionally been used in modeling. Air quality prediction for future scenarios to 2030 is being facilitated by land use projections using a spatial growth model. Land use projections were developed using the 2030 Regional Transportation Plan developed by the Atlanta Regional Commission, the regional planning agency for the area. This allows the Georgia Environmental Protection Division to evaluate how these transportation plans will affect future air quality. The coupled SGM and air quality modeling approach provides insight on what the impacts of Atlanta s growth will be on the local and regional environment and exists as a mechanism that can be used by policy makers to make rational decisions on urban growth and sustainability for the metropolitan area in the future.

Remote Sensing and Spatial Growth Modeling Coupled With Air Quality Modeling to Assess the Impact of Atlanta, Georgia on the Local and Regional Environment

NASA Astrophysics Data System (ADS)

Quattrochi, D. A.; Estes, M. G.; Crosson, W. L.; Johnson, H.; Khan, M.

2006-05-01

The growth of cities, both in population and areal extent, appears as an inexorable process. Urbanization continues at a rapid rate, and it is estimated that by the year 2025, 60 percent of the world's population will live in cities. Urban expansion has profound impacts on a host of biophysical, environmental, and atmospheric processes within an urban ecosystems perspective. A reduction in air quality over cities is a major result of these impacts. Because of its complexity, the urban landscape is not adequately captured in air quality models such as the Community Multiscale Air Quality (CMAQ) model that is used to assess whether urban areas are in attainment of EPA air quality standards, primarily for ground level ozone. This inadequacy of the CMAQ model to sufficiently respond to the heterogeneous nature of the urban landscape can impact how well the model predicts ozone levels over metropolitan areas and ultimately, whether cities exceed EPA ozone air quality standards. We are exploring the utility of high-resolution remote sensing data and urban spatial growth modeling (SGM) projections as improved inputs to a meteorological/air quality modeling system focusing on the Atlanta, Georgia metropolitan area as a case study. These growth projections include "business as usual" and "smart growth" scenarios out to 2030. The growth projections illustrate the effects of employing urban heat island mitigation strategies, such as increasing tree canopy and albedo across the Atlanta metro area, which in turn, are used to model how air temperature can potentially be moderated as impacts on elevating ground-level ozone, as opposed to not utilizing heat island mitigation strategies. The National Land Cover Dataset at 30m resolution is being used as the land use/land cover input and aggregated to the 4km scale for the MM5 mesoscale meteorological model and the CMAQ modeling schemes. Use of these data has been found to better characterize low density/suburban development as compared with USGS 1km land use/land cover data that have traditionally been used in modeling. Air quality prediction for future scenarios to 2030 is being facilitated by land use projections using a spatial growth model. Land use projections were developed using the 2030 Regional Transportation Plan developed by the Atlanta Regional Commission, the regional planning agency for the area. This allows the Georgia Environmental Protection Division to evaluate how these transportation plans will affect future air quality. The coupled SGM and air quality modeling approach provides insight on what the impacts of Atlanta's growth will be on the local and regional environment and exists as a mechanism that can be used by policy makers to make rational decisions on urban growth and sustainability for the metropolitan area in the future.

Influence of Urbanicity and County Characteristics on the Association between Ozone and Asthma Emergency Department Visits in North Carolina

PubMed Central

Rappold, Ana G.; Davis, J. Allen; Richardson, David B.; Waller, Anna E.; Luben, Thomas J.

2014-01-01

Background: Air pollution epidemiologic studies, often conducted in large metropolitan areas because of proximity to regulatory monitors, are limited in their ability to examine potential associations between air pollution exposures and health effects in rural locations. Methods: Using a time-stratified case-crossover framework, we examined associations between asthma emergency department (ED) visits in North Carolina (2006–2008), collected by a surveillance system, and short-term ozone (O3) exposures using predicted concentrations from the Community Multiscale Air Quality (CMAQ) model. We estimated associations by county groupings based on four urbanicity classifications (representative of county size and urban proximity) and county health. Results: O3 was associated with asthma ED visits in all-year and warm season (April–October) analyses [odds ratio (OR) = 1.019; 95% CI: 0.998, 1.040; OR = 1.020; 95% CI: 0.997, 1.044, respectively, for a 20-ppb increase in lag 0–2 days O3]. The association was strongest in Less Urbanized counties, with no evidence of a positive association in Rural counties. Associations were similar when adjusted for fine particulate matter in copollutant models. Associations were stronger for children (5–17 years of age) compared with other age groups, and for individuals living in counties identified with poorer health status compared with counties that had the highest health rankings, although estimated associations for these subgroups had larger uncertainty. Conclusions: Associations between short-term O3 exposures and asthma ED visits differed by overall county health and urbanicity, with stronger associations in Less Urbanized counties, and no positive association in Rural counties. Results also suggest that children are at increased risk of O3-related respiratory effects. Citation: Sacks JD, Rappold AG, Davis JA Jr, Richardson DB, Waller AE, Luben TJ. 2014. Influence of urbanicity and county characteristics on the association between ozone and asthma emergency department visits in North Carolina. Environ Health Perspect 122:506–512; http://dx.doi.org/10.1289/ehp.1306940 PMID:24569869

Calibration of low-cost gas sensors for an urban air quality monitoring network

NASA Astrophysics Data System (ADS)

Scott, A.; Kelley, C.; He, C.; Ghugare, P.; Lehman, A.; Benish, S.; Stratton, P.; Dickerson, R. R.; Zuidema, C.; Azdoud, Y.; Ren, X.

2017-12-01

In a warming world, environmental pollution may be exacerbated by anthropogenic activities, such as climate change and the urban heat island effect, as well as natural phenomena such as heat waves. However, monitoring air pollution at federal reference standards (approximately 1 part per billion or ppb for ambient ozone) is cost-prohibitive in heterogeneous urban areas as many expensive devices are required to fully capture a region's geo-spatial variability. Innovation in low-cost sensors provide a potential solution, yet technical challenges remain to overcome possible imprecision in the data. We present the calibrations of ozone and nitrous dioxide from a low-cost air quality monitoring device designed for the Baltimore Open Air Project. The sensors used in this study are commercially available thin film electrochemical sensors from SPEC Sensor, which are amperometric, meaning they generate current proportional to volumetric fraction of gas. The results of sensor calibrations in the laboratory and field are presented.

The 1979 Southeastern Virginia Urban Plume Study (SEV-UPS): Surface and airborne studies

NASA Technical Reports Server (NTRS)

White, J. H.; Eaton, W. C.; Saeger, M. L.; Strong, R. B.; Tommerdahl, J. B.

1980-01-01

The operation of two surface monitoring stations (one in downtown Norfolk, Virginia, one south of the city near the Great Dismal Swamp) and the collection of 40 hours of airborne measurements is described. Surface site measurements of ozone, oxides of nitrogen, sulfur dioxide, temperature, dew point, b sub seat, and condensation nuclei were made. Instrument calibrations, quality assurance audits, and preliminary data analysis in support of the Urban Plume Study were also made. The air pollution problems that were addressed are discussed. Data handling procedures followed for the surface stations are presented. The operation of the aircraft sampling platform is described. Aircraft sampling procedures are discussed. A preliminary descriptive analysis of the aircraft data is given along with data or plots for surface sites, airborne studies, hydrocarbon species, and instrument performance audits. Several of the aircraft flights clearly show the presence of an urban ozone plume downwind of Norfolk in the direction of the mean wind flow.

Volatile chemical products emerging as largest petrochemical source of urban organic emissions.

PubMed

McDonald, Brian C; de Gouw, Joost A; Gilman, Jessica B; Jathar, Shantanu H; Akherati, Ali; Cappa, Christopher D; Jimenez, Jose L; Lee-Taylor, Julia; Hayes, Patrick L; McKeen, Stuart A; Cui, Yu Yan; Kim, Si-Wan; Gentner, Drew R; Isaacman-VanWertz, Gabriel; Goldstein, Allen H; Harley, Robert A; Frost, Gregory J; Roberts, James M; Ryerson, Thomas B; Trainer, Michael

2018-02-16

A gap in emission inventories of urban volatile organic compound (VOC) sources, which contribute to regional ozone and aerosol burdens, has increased as transportation emissions in the United States and Europe have declined rapidly. A detailed mass balance demonstrates that the use of volatile chemical products (VCPs)-including pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products-now constitutes half of fossil fuel VOC emissions in industrialized cities. The high fraction of VCP emissions is consistent with observed urban outdoor and indoor air measurements. We show that human exposure to carbonaceous aerosols of fossil origin is transitioning away from transportation-related sources and toward VCPs. Existing U.S. regulations on VCPs emphasize mitigating ozone and air toxics, but they currently exempt many chemicals that lead to secondary organic aerosols. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Modelling the dispersion and transport of reactive pollutants in a deep urban street canyon: using large-eddy simulation.

PubMed

Zhong, Jian; Cai, Xiao-Ming; Bloss, William James

2015-05-01

This study investigates the dispersion and transport of reactive pollutants in a deep urban street canyon with an aspect ratio of 2 under neutral meteorological conditions using large-eddy simulation. The spatial variation of pollutants is significant due to the existence of two unsteady vortices. The deviation of species abundance from chemical equilibrium for the upper vortex is greater than that for the lower vortex. The interplay of dynamics and chemistry is investigated using two metrics: the photostationary state defect, and the inferred ozone production rate. The latter is found to be negative at all locations within the canyon, pointing to a systematic negative offset to ozone production rates inferred by analogous approaches in environments with incomplete mixing of emissions. This study demonstrates an approach to quantify parameters for a simplified two-box model, which could support traffic management and urban planning strategies and personal exposure assessment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of the Community Multiscale Air Quality Model for Simulating Winter Ozone Formation in the Uinta Basin.

EPA Science Inventory

The Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ) models were used to simulate a 10 day high‐ozone episode observed during the 2013 Uinta Basin Winter Ozone Study (UBWOS). The baseline model had a large negative bias when compared to ozo...

Foliar phenolics in sugar maple (Acer saccharum) as a potential indicator of tropospheric ozone pollution.

PubMed

Sager, E P S; Hutchinson, T C; Croley, T R

2005-06-01

Tropospheric O3 has been implicated in the declining health of forest ecosystems in Europe and North America and has been shown to have negative consequences on human health. We have measured tropospheric ozone (O3) in the lower canopy through the use of passive monitors located in five woodlots along a 150 km urban-rural transect, originating in the large urban complex of Toronto, Canada. We also sampled foliage from 10 mature sugar maple trees in each woodlot and measured the concentration of a number of phenolic compounds and macronutrients. O3 concentrations were highest in the two rural woodlots, located approximately 150 km downwind of Toronto, when compared to the woodlots found within the Greater Toronto Area. Foliar concentrations of three flavonoids, avicularin, isoquercitrin, and quercitrin, were significantly greater and nitrogen concentrations significantly lower at these same rural woodlots, suggesting some physiological disruption is occurring in those sites where exposure to tropospheric O3 is greater. We suggest that foliar phenolics of sugar maple may be a biochemical indicator of tropospheric ozone exposure.

Chamber and field evaluations of air pollution tolerances of urban trees

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

Karnosky, D.F.

1981-04-01

Results are presented for a study of the relative air pollution tolerances of 32 urban-tree cultivars as determined by both chamber fumigations and field exposures. Tolerances to ozone and sulfur dioxide, alone and in combination, were determined using short-term, acute doses administered while the plants were inside a plastic fumigation chamber located inside the Cary Arboretum greenhouses. In a follow-up study still underway, representatives of the same cultivars were outplanted at four locations in the greater New York City area. To date, only oxidant-type injury has been observed on trees in the field plots. Cultivars tolerant to all chamber andmore » field exposures were Acer platanoides Cleveland, Crimson King, Emerald Queen, Jade Glen, and Summershade; Acer rubrum Autumn Flame and Red Sunset; Acer saccharum Green Mountain and Temple's Upright; Fagus sylvatica Rotundifolia; Fraxinus pennsylvanica Summit; and Ginkgo biloba Fastigate and Sentry. Cultivars sensitive to ozone as determined by the chamber and field tests and that may serve as bioindicators of the presence of ozone were Gleditsia triacanthos inermis imperial and Platanus acerifolia Bloodgood.« less

The lasting effect of limonene-induced particle formation on air quality in a genuine indoor environment.

PubMed

Rösch, Carolin; Wissenbach, Dirk K; von Bergen, Martin; Franck, Ulrich; Wendisch, Manfred; Schlink, Uwe

2015-09-01

Atmospheric ozone-terpene reactions, which form secondary organic aerosol (SOA) particles, can affect indoor air quality when outdoor air mixes with indoor air during ventilation. This study, conducted in Leipzig, Germany, focused on limonene-induced particle formation in a genuine indoor environment (24 m(3)). Particle number, limonene and ozone concentrations were monitored during the whole experimental period. After manual ventilation for 30 min, during which indoor ozone levels reached up to 22.7 ppb, limonene was introduced into the room at concentrations of approximately 180 to 250 μg m(-3). We observed strong particle formation and growth within a diameter range of 9 to 50 nm under real-room conditions. Larger particles with diameters above 100 nm were less affected by limonene introduction. The total particle number concentrations (TPNCs) after limonene introduction clearly exceed outdoor values by a factor of 4.5 to 41 reaching maximum concentrations of up to 267,000 particles cm(-3). The formation strength was influenced by background particles, which attenuated the formation of new SOA with increasing concentration, and by ozone levels, an increase of which by 10 ppb will result in a six times higher TPNC. This study emphasizes indoor environments to be preferred locations for particle formation and growth after ventilation events. As a consequence, SOA formation can produce significantly higher amounts of particles than transported by ventilation into the indoor air.

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.

Satellite-Based Tropospheric NO2 Column Trends in the Last 10 Years Over Mexican Urban Areas Measured by the Ozone Monitoring Instrument

NASA Astrophysics Data System (ADS)

Rivera, C. I.; Stremme, W.; Grutter, M.

2015-12-01

Population density and economic activities in urban agglomerations have drastically increased in many cities in Mexico during the last decade. Several factors are responsible for increased urbanization such as a shift of people from rural to urban areas while looking for better education, services and job opportunities as well as the natural growth of the urban areas themselves. Urbanization can create great social, economic and environmental pressures and changes which can easily be observed in most urban agglomerations in the world. In this study, we have focused on analyzing tropospheric NO2 (nitrogen dioxide) column trends over Mexican urban areas that have a population of at least one million inhabitants according to the latest 2010 population census. Differential Optical Absorption Spectroscopy (DOAS) measurements of NO2 conducted by the space-borne Ozone Monitoring Instrument (OMI) on board the Aura satellite between 2005 and 2014 have been used for this analysis. This dataset has allowed us to obtain a satellite-based 10-year tropospheric NO2 column trend over the most populated Mexican cities which include the dominating metropolitan area of Mexico City with more than twenty million inhabitants as well as ten other Mexican cities with a population ranging between one to five million inhabitants with a wide range of activities (commercial, agricultural or heavily industrialized) as well as two important border crossings. Distribution maps of tropospheric NO2 columns above the studied urban agglomerations were reconstructed from the analyzed OMI dataset, allowing to identify areas of interest due to clear NO2 enhancements inside these urban regions.

Effect of Pre-ozonation on Haloacetic Acids Formation in Ganga River Water at Kanpur, India

NASA Astrophysics Data System (ADS)

Naladala, Nagasrinivasa Rao; Singh, Rambabu; Katiyar, Kumud Lata Devi; Bose, Purnendu; Dutta, Venkatesh

2017-11-01

Almost all natural water bodies which are considered to be sustainable sources of drinking water contain organic matter in dissolved form and pathogens. This dissolved organic matter and pathogens cannot be removed effectively through traditional filtering processes in drinking water treatment plants. Chlorination of such water for disinfection results in large amounts of disinfection by-products (DBPs), mainly trihalomethanes and haloacetic acids (HAAs), which showed many health effects like cancer and reproductive problems in lab animals and in human beings as well. Complete removal of dissolved organic carbon (DOC), which is a precursor compound for HAAs formation, is impossible from a practical point of view; hence, it will be better if DOC activity towards DBPs formation can be reduced via some process. The present article describes the process of pre-ozonating post-coagulated Ganga River water at Kanpur in a continuous flow mode and its effect on HAAs formation. Nearly 58% reduction in HAAs formation was observed during this study at higher doses of ozone.

Ozone and limonene in indoor air: a source of submicron particle exposure.

PubMed Central

Wainman, T; Zhang, J; Weschler, C J; Lioy, P J

2000-01-01

Little information currently exists regarding the occurrence of secondary organic aerosol formation in indoor air. Smog chamber studies have demonstrated that high aerosol yields result from the reaction of ozone with terpenes, both of which commonly occur in indoor air. However, smog chambers are typically static systems, whereas indoor environments are dynamic. We conducted a series of experiments to investigate the potential for secondary aerosol in indoor air as a result of the reaction of ozone with d-limonene, a compound commonly used in air fresheners. A dynamic chamber design was used in which a smaller chamber was nested inside a larger one, with air exchange occurring between the two. The inner chamber was used to represent a model indoor environment and was operated at an air exchange rate below 1 exchange/hr, while the outer chamber was operated at a high air exchange rate of approximately 45 exchanges/hr. Limonene was introduced into the inner chamber either by the evaporation of reagent-grade d-limonene or by inserting a lemon-scented, solid air freshener. A series of ozone injections were made into the inner chamber during the course of each experiment, and an optical particle counter was used to measure the particle concentration. Measurable particle formation and growth occurred almost exclusively in the 0.1-0.2 microm and 0.2-0.3 microm size fractions in all of the experiments. Particle formation in the 0.1-0.2 microm size range occurred as soon as ozone was introduced, but the formation of particles in the 0.2-0.3 microm size range did not occur until at least the second ozone injection occurred. The results of this study show a clear potential for significant particle concentrations to be produced in indoor environments as a result of secondary particle formation via the ozone-limonene reaction. Because people spend the majority of their time indoors, secondary particles formed in indoor environments may make a significant contribution to overall particle exposure. This study provides data for assessing the impact of outdoor ozone on indoor particles. This is important to determine the efficacy of the mass-based particulate matter standards in protecting public health because the indoor secondary particles can vary coincidently with the variations of outdoor fine particles in summer. PMID:11133393

Ozone and limonene in indoor air: a source of submicron particle exposure.

PubMed

Wainman, T; Zhang, J; Weschler, C J; Lioy, P J

2000-12-01

Little information currently exists regarding the occurrence of secondary organic aerosol formation in indoor air. Smog chamber studies have demonstrated that high aerosol yields result from the reaction of ozone with terpenes, both of which commonly occur in indoor air. However, smog chambers are typically static systems, whereas indoor environments are dynamic. We conducted a series of experiments to investigate the potential for secondary aerosol in indoor air as a result of the reaction of ozone with d-limonene, a compound commonly used in air fresheners. A dynamic chamber design was used in which a smaller chamber was nested inside a larger one, with air exchange occurring between the two. The inner chamber was used to represent a model indoor environment and was operated at an air exchange rate below 1 exchange/hr, while the outer chamber was operated at a high air exchange rate of approximately 45 exchanges/hr. Limonene was introduced into the inner chamber either by the evaporation of reagent-grade d-limonene or by inserting a lemon-scented, solid air freshener. A series of ozone injections were made into the inner chamber during the course of each experiment, and an optical particle counter was used to measure the particle concentration. Measurable particle formation and growth occurred almost exclusively in the 0.1-0.2 microm and 0.2-0.3 microm size fractions in all of the experiments. Particle formation in the 0.1-0.2 microm size range occurred as soon as ozone was introduced, but the formation of particles in the 0.2-0.3 microm size range did not occur until at least the second ozone injection occurred. The results of this study show a clear potential for significant particle concentrations to be produced in indoor environments as a result of secondary particle formation via the ozone-limonene reaction. Because people spend the majority of their time indoors, secondary particles formed in indoor environments may make a significant contribution to overall particle exposure. This study provides data for assessing the impact of outdoor ozone on indoor particles. This is important to determine the efficacy of the mass-based particulate matter standards in protecting public health because the indoor secondary particles can vary coincidently with the variations of outdoor fine particles in summer.

Simultaneous removal of 2,4,6-tribromophenol from water and bromate ion minimization by ozonation.

PubMed

Gounden, Asogan N; Singh, Sooboo; Jonnalagadda, Sreekantha B

2018-06-02

The study investigates the degradation of 2,4,6-tribromophenol (2,4,6-TBP) and the influence of solution pH, alkalinity, H 2 O 2 and O 3 dosage. Debromination efficiency of 2,4,6-TBP was the highest in basic water (pH = 10.61). The extent of TOC removal compared favourably with the amount of substrate converted, suggesting favourable mineralization of oxygenated by-products (OBPs). Ozonation in basic water favoured the formation of toxicBrO 3 - , while in acidic water (pH = 2.27) BrO 3 - yield was lowest. In acidic water the presence of CO 3 2- showed negligible effect on conversion, TOC and  BrO 3 - yield compared to ozonation alone. In basic water both 2,4,6-TBP conversion and TOC removal decreased with an increase in CO 3 2- , hence minimizing BrO 3 - formation. The O 3 /H 2 O 2 process showed an improvement in the debromination efficiency and TOC data revealed that total mineralization of OBP's was achieved. However, only 10% H 2 O 2 was able to effectively decrease BrO 3 - formation. Increasing the ozone concentration from 20 to 100 ppm enhanced the conversion of 2,4,6-TBP and TOC removal. At low ozone concentrations poor mineralization of OBP's occurred, while complete mineralization was achieved at higher ozone dose. The reaction pathways for ozone degradation of 2,4,6-TBP in acidic and basic waters is proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

Atmospheric pollutants in peri-urban forests of Quercus ilex: evidence of pollution abatement and threats for vegetation.

PubMed

García-Gómez, Héctor; Aguillaume, Laura; Izquieta-Rojano, Sheila; Valiño, Fernando; Àvila, Anna; Elustondo, David; Santamaría, Jesús M; Alastuey, Andrés; Calvete-Sogo, Héctor; González-Fernández, Ignacio; Alonso, Rocío

2016-04-01

Peri-urban vegetation is generally accepted as a significant remover of atmospheric pollutants, but it could also be threatened by these compounds, with origin in both urban and non-urban areas. To characterize the seasonal and geographical variation of pollutant concentrations and to improve the empirical understanding of the influence of Mediterranean broadleaf evergreen forests on air quality, four forests of Quercus ilex (three peri-urban and one remote) were monitored in different areas in Spain. Concentrations of nitrogen dioxide (NO2), ammonia (NH3), nitric acid (HNO3) and ozone (O3) were measured during 2 years in open areas and inside the forests and aerosols (PM10) were monitored in open areas during 1 year. Ozone was the only air pollutant expected to have direct phytotoxic effects on vegetation according to current thresholds for the protection of vegetation. The concentrations of N compounds were not high enough to directly affect vegetation but could be contributing through atmospheric N deposition to the eutrophization of these ecosystems. Peri-urban forests of Q. ilex showed a significant below-canopy reduction of gaseous concentrations (particularly NH3, with a mean reduction of 29-38%), which indicated the feasibility of these forests to provide an ecosystem service of air quality improvement. Well-designed monitoring programs are needed to further investigate air quality improvement by peri-urban ecosystems while assessing the threat that air pollution can pose to vegetation.

The QBO and interannual variation in total ozone

NASA Technical Reports Server (NTRS)

Lait, Leslie R.; Schoeberl, Mark R.; Newman, Paul A.; Stolarski, Richard S.

1988-01-01

Garcia and Soloman (1987) have noted that the October monthly mean minimum total ozone amounts south of 30 S were modulated by a quasibiennial oscillation (QBO) signal. The precise mechanism behind this effect, however, is unclear. Is the modulation brought about by the circulation-produced QBO signal in the ozone concentration itself, or does the temperature QBO modulate the formation of polar stratospheric clouds (PSCs), leading to changes in the chemically induced Antarctic spring ozone decline rate. Or is some other phenomenon involved. To investigate the means through which the QBO effect occurs, a series of correlation studies has been made between polar ozone and QBO signal in ozone and temperature.

Combination of UV absorbance and electron donating capacity to assess degradation of micropollutants and formation of bromate during ozonation of wastewater effluents.

PubMed

Chon, Kangmin; Salhi, Elisabeth; von Gunten, Urs

2015-09-15

In this study, the changes in UV absorbance at 254 nm (UVA254) and electron donating capacity (EDC) were investigated as surrogate indicators for assessing removal of micropollutants and bromate formation during ozonation of wastewater effluents. To measure the EDC, a novel method based on size exclusion chromatography followed by a post-column reaction was developed and calibrated against an existing electrochemical method. Low specific ozone doses led to a more efficient abatement of EDC than of UVA254. This was attributed to the abatement of phenolic moieties in the dissolved organic matter (DOM), which lose their EDC upon oxidation, but are partially transformed into quinones, which still absorb in the measured UV range. For higher specific ozone doses, the relative EDC abatement was lower than the relative UVA abatement, which can be explained by the oxidation of UV absorbing moieties (e.g. non-activated aromatic compounds), which contribute less to EDC. The abatement of the selected micropollutants (i.e., 17α-ethinylestradiol (EE2), carbamazepine (CBZ), atenolol (ATE), bezafibrate (BZF), ibuprofen (IBU), and p-chlorobenzoic acid (pCBA)) varied significantly depending on their reactivity with ozone in the examined specific ozone dose range of 0-1.45 mgO3/mgDOC. The decrease of EE2 and CBZ with high ozone reactivity was linearly proportional to the reduction of the relative residuals of UVA254 and EDC. The abatement of ATE, BZF, IBU, and pCBA with intermediate to low ozone reactivities was not significant in a first phase (UVA254/UVA254,0 = 1.00-0.70; EDC/EDC0 = 1.00-0.56) while their abatement was more efficient than the degradation of the relative residual UVA254 and much more noticeable than the degradation of the relative residual EDC in a second phase (UVA254/UVA254,0 = 0.70-0.25; EDC/EDC0 = 0.56-0.25) because the partially destroyed UV absorbing and electron donating DOM moieties become recalcitrant to ozone attack. Bromate formation was pronounced for specific ozone doses >0.25 mgO3/mgDOC. At these ozone doses, the residual DOM competes less with bromide for ozone as the electron-rich DOM moieties are almost completely degraded. Overall, these results imply that a combination of the relative residual UVA254 and EDC more truly reflects the intrinsic reactivity of DOM associated with the removal of micropollutants and bromate formation than the single use of the UV absorbance-based surrogate indicators. Copyright © 2015 Elsevier Ltd. All rights reserved.

A measurement/model comparison of ozone photochemical loss in the Antarctic ozone hole using Polar Ozone and Aerosol Measurement observations and the Match technique

NASA Astrophysics Data System (ADS)

Hoppel, Karl; Bevilacqua, Richard; Canty, Timothy; Salawitch, Ross; Santee, Michelle

2005-10-01

The Polar Ozone and Aerosol Measurement (POAM III) instrument has provided 6 years (1998 to present) of Antarctic ozone profile measurements, which detail the annual formation of the ozone hole. During the period of ozone hole formation the measurement latitude follows the edge of the polar night and presents a unique challenge for comparing with model simulations. The formation of the ozone hole has been simulated by using a photochemical box model with an ensemble of trajectories, and the results were sampled at the measurement latitude for comparison with the measured ozone. The agreement is generally good but very sensitive to the model dynamics and less sensitive to changes in the model chemistry. In order to better isolate the chemical ozone loss the Match technique was applied to 5 years of data to directly calculate ozone photochemical loss rates. The measured loss rates are specific to the high solar zenith angle conditions of the POAM-Match trajectories and are found to increase slowly from July to early August and then increase rapidly until mid-September. The Match results are sensitive to the choice of meteorological analysis used for the trajectory calculations. The ECMWF trajectories yield the smallest, and perhaps most accurate, peak loss rates that can be reproduced by a photochemical model using standard JPL 2002 kinetics, assuming reactive bromine (BrOx) of 14 pptv based solely on contributions from CH3Br and halons, and without requiring ClOx to exceed the upper limit for available inorganic chlorine of 3.7 ppbv. Larger Match ozone loss rates are found for the late August and early September period if trajectories based on UKMO and NCEP analyses are employed. Such loss rates require higher values for ClO and/or BrO than can be simulated using JPL 2002 chemical kinetics and complete activation of chlorine. In these cases, the agreement between modeled and measured loss rates is significantly improved if the model employs larger ClOOCl cross sections (e.g., Burkholder et al., 1990) and BrOx of 24 ppt which reflects significant contributions from very short-lived bromocarbons to the inorganic bromine budget.

Regional ozone impacts of increased natural gas use in the Texas power sector and development in the Eagle Ford shale.

PubMed

Pacsi, Adam P; Kimura, Yosuke; McGaughey, Gary; McDonald-Buller, Elena C; Allen, David T

2015-03-17

The combined emissions and air quality impacts of electricity generation in the Texas grid and natural gas production in the Eagle Ford shale were estimated at various natural gas price points for the power sector. The increased use of natural gas in the power sector, in place of coal-fired power generation, drove reductions in average daily maximum 8 h ozone concentration of 0.6-1.3 ppb in northeastern Texas for a high ozone episode used in air quality planning. The associated increase in Eagle Ford upstream oil and gas production nitrogen oxide (NOx) emissions caused an estimated local increase, in south Texas, of 0.3-0.7 ppb in the same ozone metric. In addition, the potential ozone impacts of Eagle Ford emissions on nearby urban areas were estimated. On the basis of evidence from this work and a previous study on the Barnett shale, the combined ozone impact of increased natural gas development and use in the power sector is likely to vary regionally and must be analyzed on a case by case basis.

Ozone suppression of oat crown rust uredia development

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

Heagle, A.S.

1969-01-01

First foliage leaves of 10-day-old crown rust differential varieties of Avena sativa were inoculated with urediospores of race 264 of Puccinia coronata var. avenae and placed for 16 hr in a mist chamber at 23 C. Infected plants were then placed in two separate chambers at 25C, 80% relative humidity, 3000 ft-c, and a 16-hr photoperiod. Plants in one chamber were exposed to 10 pphm ozone (KI corrected Mast value) for 6 hr daily in the light for 10 days. Plants in the other chamber were not exposed to ozone. Visible ozone injury was restricted to minor flecking. In severalmore » varieties, a slight reddening appeared on inoculated leaves near the end of the experiment. The reaction to rust on ozone-exposed plants of all varieties was resistant, whereas the reaction on nonexposed plants of all differentials except 8, 9, and 10 was susceptible. The level of ozone used in this experiment is often surpassed in rural areas near urban centers, indicating that air pollution can influence rust development in the field.« less

Evaluation of Urban Air Quality By Passive Sampling Technique

NASA Astrophysics Data System (ADS)

Nunes, T. V.; Miranda, A. I.; Duarte, S.; Lima, M. J.

Aveiro is a flat small city in the centre of Portugal, close to the Atlantic coast. In the last two decades an intensive development of demographic, traffic and industry growth in the region was observed which was reflected on the air quality degrada- tion. In order to evaluate the urban air quality in Aveiro, a field-monitoring network by passive sampling with high space resolution was implemented. Twenty-four field places were distributed in a area of 3x3 Km2 and ozone and NO2 concentrations were measured. The site distribution density was higher in the centre, 250x250 m2 than in periphery where a 500x500 m2 grid was used. The selection of field places took into consideration the choice criteria recommendation by United Kingdom environmental authorities, and three tubes and a blank tube for each pollutant were used at each site. The sampling system was mounted at 3m from the ground usually profiting the street lampposts. Concerning NO2 acrylic tubes were used with 85 mm of length and an in- ternal diameter of 12mm, where in one of the extremities three steel grids impregnated with a solution of TEA were placed and fixed with a polyethylene end cup (Heal et al., 1999); PFA Teflon tube with 53 mm of length and 9 mm of internal diameter and three impregnated glass filters impregnated with DPE solution fixed by a teflon end cup was used for ozone sampling (Monn and Hargartner, 1990). The passive sampling method for ozone and nitrogen dioxide was compared with continuous measurements, but the amount of measurements wasnSt enough for an accurate calibration and validation of the method. Although this constraint the field observations (June to August 2001) for these two pollutants assign interesting information about the air quality in the urban area. A krigger method of interpolation (Surfer- Golden Software-2000) was applied to field data to obtain isolines distribution of NO2 and ozone concentration for the studied area. Even the used passive sampling method has many limitations it is possi- ble to say that the NO2 concentrations were strictly related with traffic intensity and in the centre 3 to 10 times higher values were observed than the incoming air to the city; on the contrary the ozone seems to be consumed where we observe the highest NO2 concentrations. Heal, M. R.; O'Donoghue, M. A. and Cape, J. N., Overestimation of Urban Nitrogen Dioxide by Passive Sampling Tubes: a comparative exposure and model study, Atmo- spheric Environment, Vol 33, pp 513-524, 1999 Monn, Ch., Hangartner, M., Passive Sampling for Ozone, J. of Air and Waste Management Association, Vol. 40, Nz 3, 1990

Interaction of ozone with wooden building products, treated wood samples and exotic wood species

NASA Astrophysics Data System (ADS)

Schripp, Tobias; Langer, Sarka; Salthammer, Tunga

2012-07-01

Wooden building products indoors are known to be able to affect the perceived air quality depending on their emission strength. The indoor application of modern ecological lacquer systems (eco-lacquers or 'green' lacquers) may be a much stronger source than the substrates itself. Especially with regard to the formation of ultrafine particles by gas-to-particle conversion in the presence of ozone or other reactive species the impact of the applied building products on the indoor air quality has to be addressed. The present study reports a two concentration step ozonation of OSB panels, painted beech boards, and a number of solid 'exotic' wood types in a 1 m³ emission test chamber. The emission of volatile organic compounds (VOC) was recorded as well as the formation of ultrafine particles in the range 7-300 nm. The products are characterized on the basis of their ozone deposition velocity; the obtained values of 0.008-0.381 cm s-1 are comparable with previously published data. Within the samples of the present study one eco-lacquer was the strongest source of VOC (total VOC ˜ 60 mg m-3) while the wooden building products (OSB) were of intermediate emission strength. The lowest emission was found for the solid (exotic) wood samples. The VOC release of the samples corresponded roughly to the particle formation potential. However, the strongest UFP formation was measured for one solid wood sample ('Garapa') which showed a strong surface reaction in the presence of ozone and formed a large number of particles <40 nm. Overall, the experiments demonstrated the necessity of real-life samples for the estimation of UFP indoor air pollution from the ozone chemistry of terpenes.

Role of carbonyls and aromatics in the formation of tropospheric ozone in Rio de Janeiro, Brazil.

PubMed

da Silva, Débora Bonfim Neves; Martins, Eduardo Monteiro; Corrêa, Sergio Machado

2016-05-01

The ozone in Rio de Janeiro has been in violation of national air quality standards. Among all of the monitoring stations, the Bangu neighbourhood has the most violations of the national standard of 160 μg m(-3) for the years 2012 and 2013. This study evaluated the reactivity of the carbonyls and aromatics in the tropospheric ozone formation processes. The samples were collected between July and October of 2013. Carbonyls were sampled using SiO2 cartridges coated with C18 and impregnated with 2,4-dinitrophenylhydrazine and were analysed by HPLC. Activated carbon cartridges and GC/MS were used to measure the concentration of monoaromatic hydrocarbons. An air quality monitoring station provided the concentrations of the criteria pollutants and the meteorological parameters. Cluster analysis and a Pearson correlation matrix were used to determine the formation of groups and the correlation of the variables. The evaluation of the volatile organic compounds (VOC) reaction with OH radicals and the MIR scale was used to extrapolate the reactivity of VOCs to the ozone formation. The average concentrations obtained were 19.7 and 51.9 μg m(-3) for formaldehyde and acetaldehyde, respectively. The mean concentrations obtained for aromatics were 1.5, 6.7, 1.5, 2.6 and 1.6 μg m(-3) for benzene, toluene, ethyl benzene, m+p-xylene and o-xylene, respectively. The cluster analysis indicated the presence of three similar groups, with one formed by gaseous criteria pollutants, another formed by the meteorological parameters, ozone and fine particles, and the last group formed by the aromatics. For the two reactivity scales evaluated, acetaldehyde and toluene were the main ozone precursors.

Plants as indicators of urban air pollution (ozone and trace elements) in Pisa, Italy.

PubMed

Nali, Cristina; Crocicchi, Lara; Lorenzini, Giacomo

2004-07-01

A biennial integrated survey, based on the use of vascular plants for the bioindication of the effects of tropospheric ozone, was performed in the area of Pisa (Tuscany, Central Italy). It also investigated the distribution of selected trace elements in plants and the data were compared with those obtained from the use of passive samplers, automatic analysers of ozone and lichen biodiversity. Photochemically produced ozone proved to be present during the warm season, with maximum hourly means surpassing 100 ppb: the use of supersensitive tobacco Bel-W3 confirmed the value of detailed, cost-effective, monitoring surveys. Trials with clover clones demonstrate that sensitive plants undergo severe biomass reduction in the current ozone regime. The mean NC-S (clover clone sensitive to ozone):NC-R (resistant) biomass ratio ranged from 0.7 (in 1999) to 0.5 (in 2000). The economic impact of these reductions deserves attention. The data obtained using passive ozone samplers exceeded those obtained using an automatic analyser. The mapping of epiphytic lichen biodiversity was not related to the geographical ozone distribution as can be seen from the tobacco's response. Lettuce plants grown under standardized conditions were used positively as bioaccumulators of trace elements: Pb was abundantly recovered, but a large portion of this element was removed by washing.

BAERLIN2014 - the influence of land surface types on and the horizontal heterogeneity of air pollutant levels in Berlin

NASA Astrophysics Data System (ADS)

Bonn, Boris; von Schneidemesser, Erika; Andrich, Dorota; Quedenau, Jörn; Gerwig, Holger; Lüdecke, Anja; Kura, Jürgen; Pietsch, Axel; Ehlers, Christian; Klemp, Dieter; Kofahl, Claudia; Nothard, Rainer; Kerschbaumer, Andreas; Junkermann, Wolfgang; Grote, Rüdiger; Pohl, Tobias; Weber, Konradin; Lode, Birgit; Schönberger, Philipp; Churkina, Galina; Butler, Tim M.; Lawrence, Mark G.

2016-06-01

Urban air quality and human health are among the key aspects of future urban planning. In order to address pollutants such as ozone and particulate matter, efforts need to be made to quantify and reduce their concentrations. One important aspect in understanding urban air quality is the influence of urban vegetation which may act as both emitter and sink for trace gases and aerosol particles. In this context, the "Berlin Air quality and Ecosystem Research: Local and long-range Impact of anthropogenic and Natural hydrocarbons 2014" (BAERLIN2014) campaign was conducted between 2 June and 29 August in the metropolitan area of Berlin and Brandenburg, Germany. The predominant goals of the campaign were (1) the characterization of urban gaseous and particulate pollution and its attribution to anthropogenic and natural sources in the region of interest, especially considering the connection between biogenic volatile organic compounds and particulates and ozone; (2) the quantification of the impact of urban vegetation on organic trace gas levels and the presence of oxidants such as ozone; and (3) to explain the local heterogeneity of pollutants by defining the distribution of sources and sinks relevant for the interpretation of model simulations. In order to do so, the campaign included stationary measurements at urban background station and mobile observations carried out from bicycle, van and airborne platforms. This paper provides an overview of the mobile measurements (Mobile BAERLIN2014) and general conclusions drawn from the analysis. Bicycle measurements showed micro-scale variations of temperature and particulate matter, displaying a substantial reduction of mean temperatures and particulate levels in the proximity of vegetated areas compared to typical urban residential area (background) measurements. Van measurements extended the area covered by bicycle observations and included continuous measurements of O3, NOx, CO, CO2 and point-wise measurement of volatile organic compounds (VOCs) at representative sites for traffic- and vegetation-affected sites. The quantification displayed notable horizontal heterogeneity of the short-lived gases and particle number concentrations. For example, baseline concentrations of the traffic-related chemical species CO and NO varied on average by up to ±22.2 and ±63.5 %, respectively, on the scale of 100 m around any measurement location. Airborne observations revealed the dominant source of elevated urban particulate number and mass concentrations being local, i.e., not being caused by long-range transport. Surface-based observations related these two parameters predominantly to traffic sources. Vegetated areas lowered the pollutant concentrations substantially with ozone being reduced most by coniferous forests, which is most likely caused by their reactive biogenic VOC emissions. With respect to the overall potential to reduce air pollutant levels, forests were found to result in the largest decrease, followed by parks and facilities for sports and leisure. Surface temperature was generally 0.6-2.1 °C lower in vegetated regions, which in turn will have an impact on tropospheric chemical processes. Based on our findings, effective future mitigation activities to provide a more sustainable and healthier urban environment should focus predominantly on reducing fossil-fuel emissions from traffic as well as on increasing vegetated areas.

Novel test procedure to evaluate the treatability of wastewater with ozone.

PubMed

Schindler Wildhaber, Yael; Mestankova, Hana; Schärer, Michael; Schirmer, Kristin; Salhi, Elisabeth; von Gunten, Urs

2015-05-15

Organic micropollutants such as pharmaceuticals, estrogens or pesticides enter the environment continuously through the effluent of municipal wastewater treatment plants (WWTPs). Enhanced treatment of wastewater (WW) by ozone (O3) is probably one of the simplest measures for abatement of organic micropollutants to avoid their discharge to the aquatic environment. During ozonation most organic micropollutants present in treated WW are oxidized either by a direct reaction with O3 or by secondarily formed hydroxyl radicals (OH). However, undesired oxidation by-products from the oxidative transformation of matrix components can also be formed. A modular laboratory decision tool based on the findings of previous investigations is presented to test the feasibility of ozonation as an option to upgrade specific WWTPs. These modules consist of investigations to assess (i) the matrix effects on ozone stability, (ii) the efficiency of micropollutant removal, (iii) the oxidation by-product formation, as well as (iv) bioassays to measure specific and unspecific toxicity of the treated WWs. Matrix effects on ozone stability (quantified as O3 and OH exposures) can give first indications on the suitability of an ozonation step. Ozonation of WWs yielding O3 and OH exposures and micropollutant abatement similar to reference values evoked a significant improvement of the water quality as indicated by a broad range of bioassays. Irregular behavior of the ozonation points towards unknown compounds, possibly leading to the formation of undesired degradation products. It has been observed that in such WWs ozonation partly enhanced toxicity. In summary, the presented tiered laboratory test procedure represents a relatively cheap and straight-forward methodology to evaluate the feasibility of ozonation to upgrade specific WWTPs for micropollutant removal based on chemical and biological measurements. Copyright © 2015 Elsevier Ltd. All rights reserved.

Levofloxacin oxidation by ozone and hydroxyl radicals: kinetic study, transformation products and toxicity.

PubMed

Hamdi El Najjar, Nasma; Touffet, Arnaud; Deborde, Marie; Journel, Romain; Leitner, Nathalie Karpel Vel

2013-10-01

This work was carried out to investigate the fate of the antibiotic levofloxacin upon oxidation with ozone and hydroxyl radicals. A kinetic study was conducted at 20 °C for each oxidant. Ozonation experiments were performed using a competitive kinetic method with carbamazepin as competitor. Significant levofloxacin removal was observed during ozonation and a rate constant value of 6.0×10(4) M(-1) s(-1) was obtained at pH 7.2. An H2O2/UV system was used for the formation of hydroxyl radicals HO. The rate constant of HO was determined in the presence of a high H2O2 concentration. The kinetic expressions yielded a [Formula: see text] value of 4.5×10(9) M(-1) s(-1) at pH 6.0 and 5.2×10(9) M(-1) s(-1) at pH 7.2. These results were used to develop a model to predict the efficacy of the ozonation process and pharmaceutical removal was estimated under different ozonation conditions (i.e. oxidant concentrations and contact times). The results showed that levofloxacin was completely degraded by molecular ozone during ozonation of water and that hydroxyl radicals had no effect in real waters conditions. Moreover, LC/MS/MS and toxicity assays using Lumistox test were performed to identify ozonation transformation products. Under these conditions, four transformation products were observed and their chemical structures were proposed. The results showed an increase in toxicity during ozonation, even after degradation of all of the observed transformation products. The formation of other transformation products not identified under our experimental conditions could be responsible for the observed toxicity. These products might be ozone-resistant and more toxic to Vibrio fisheri than levofloxacin. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Effects of Nitrogen Deposition, Ambient Ozone, and Climate Change on Forests in the Western U.S.

Treesearch

M. E. Fenn

2006-01-01

Nitrogen (N) deposition in the western United States is most severe near major urban areas or downwind of agricultural regions, particularly in areas where confined animal feeding operations such as dairies or feedlots are located. Nitrogen saturated ecosystems are predominantly found in hotspots located within 60 km of urban or agricultural emissions source areas,...

Spectroscopic signatures of ozone at the air–water interface and photochemistry implications

PubMed Central

Anglada, Josep M.; Martins-Costa, Marilia; Ruiz-López, Manuel F.; Francisco, Joseph S.

2014-01-01

First-principles simulations suggest that additional OH formation in the troposphere can result from ozone interactions with the surface of cloud droplets. Ozone exhibits an affinity for the air–water interface, which modifies its UV and visible light spectroscopic signatures and photolytic rate constant in the troposphere. Ozone cross sections on the red side of the Hartley band (290- to 350-nm region) and in the Chappuis band (450–700 nm) are increased due to electronic ozone–water interactions. This effect, combined with the potential contribution of the O3 + hν → O(3P) + O2(X3Σg−) photolytic channel at the interface, leads to an enhancement of the OH radical formation rate by four orders of magnitude. This finding suggests that clouds can influence the overall oxidizing capacity of the troposphere on a global scale by stimulating the production of OH radicals through ozone photolysis by UV and visible light at the air–water interface. PMID:25071195

The effects of welding parameters on ultra-violet light emissions, ozone and CrVI formation in MIG welding.

PubMed

Dennis, J H; Mortazavi, S B; French, M J; Hewitt, P J; Redding, C R

1997-01-01

This paper describes the relationships between ultra-violet emission, ozone generation and CrVI production in MIG welding which were measured as a function of shield gas flow rate, welding voltage, electrode stick-out and shield gas composition using an automatic welding rig that permitted MIG welding under reproducible conditions. The experimental results are interpreted in terms of the physico-chemical processes occurring in the micro- and macro-environments of the arc as part of research into process modification to reduce occupational exposure to ozone and CrVI production rates in MIG welding. We believe the techniques described here, and in particular the use of what we have termed u.v.-ozone measurements, will prove useful in further study of ozone generation and CrVI formation and may be applied in the investigation of engineering control of occupational exposure in MIG and other welding process such as Manual Metal Arc (MMA) and Tungsten Inert Gas (TIG).

78 FR 29032 - Approval and Promulgation of Implementation Plans Tennessee: Revisions to Volatile Organic...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-17

... tropospheric ozone formation. The compounds were added by EPA through a rulemaking action which provided for... consistent with federal law. Tropospheric ozone, commonly known as smog, occurs when VOC and nitrogen oxide (NO X ) react in the atmosphere. Because of the harmful health effects of ozone, EPA limits the amount...

Artificial neural network model for ozone concentration estimation and Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Gao, Meng; Yin, Liting; Ning, Jicai

2018-07-01

Air pollution in urban atmosphere directly affects public-health; therefore, it is very essential to predict air pollutant concentrations. Air quality is a complex function of emissions, meteorology and topography, and artificial neural networks (ANNs) provide a sound framework for relating these variables. In this study, we investigated the feasibility of using ANN model with meteorological parameters as input variables to predict ozone concentration in the urban area of Jinan, a metropolis in Northern China. We firstly found that the architecture of network of neurons had little effect on the predicting capability of ANN model. A parsimonious ANN model with 6 routinely monitored meteorological parameters and one temporal covariate (the category of day, i.e. working day, legal holiday and regular weekend) as input variables was identified, where the 7 input variables were selected following the forward selection procedure. Compared with the benchmarking ANN model with 9 meteorological and photochemical parameters as input variables, the predicting capability of the parsimonious ANN model was acceptable. Its predicting capability was also verified in term of warming success ratio during the pollution episodes. Finally, uncertainty and sensitivity analysis were also performed based on Monte Carlo simulations (MCS). It was concluded that the ANN could properly predict the ambient ozone level. Maximum temperature, atmospheric pressure, sunshine duration and maximum wind speed were identified as the predominate input variables significantly influencing the prediction of ambient ozone concentrations.

GEM-AQ, an On-line Global Multiscale Chemical Weather System: Model Description and Evaluation of Gas Phase Chemistry Processes

NASA Astrophysics Data System (ADS)

Neary, L.; Kaminski, J. W.; Struzewska, J.; Ainslie, B.; McConnell, J. C.

2007-12-01

Tropospheric chemistry and air quality processes were implemented on-line in the Global Environmental Multiscale model. The integrated model, GEM-AQ, has been developed as a platform to investigate chemical weather at scales from global to urban. On the global scale, the model was exercised for five years (2001-2005) to evaluate its ability to simulate seasonal variations and regional distributions of trace gases such as ozone, nitrogen dioxide and carbon monoxide. The model results are compared with observations from satellites, aircraft measurement campaigns and balloon sondes. The same model has also been evaluated on the regional (~15km resolution) and urban scale (~3km resolution). A simulation of the formation and transport of photooxidants during the European heat wave of 2006 was performed and compared with surface observations throughout central and eastern Europe. The complex topographic region of the Lower Fraser Valley in British Columbia was the focus of another model evaluation during the PACIFIC 2001 field campaign. Comparison of model results with observations during this period will be shown.

Optimized spectroscopic scheme for enhanced precision CO measurements with applications to urban source attribution

NASA Astrophysics Data System (ADS)

Nottrott, A.; Hoffnagle, J.; Farinas, A.; Rella, C.

2014-12-01

Carbon monoxide (CO) is an urban pollutant generated by internal combustion engines which contributes to the formation of ground level ozone (smog). CO is also an excellent tracer for emissions from mobile combustion sources. In this work we present an optimized spectroscopic sampling scheme that enables enhanced precision CO measurements. The scheme was implemented on the Picarro G2401 Cavity Ring-Down Spectroscopy (CRDS) analyzer which measures CO2, CO, CH4 and H2O at 0.2 Hz. The optimized scheme improved the raw precision of CO measurements by 40% from 5 ppb to 3 ppb. Correlations of measured CO2, CO, CH4 and H2O from an urban tower were partitioned by wind direction and combined with a concentration footprint model for source attribution. The application of a concentration footprint for source attribution has several advantages. The upwind extent of the concentration footprint for a given sensor is much larger than the flux footprint. Measurements of mean concentration at the sensor location can be used to estimate source strength from a concentration footprint, while measurements of the vertical concentration flux are necessary to determine source strength from the flux footprint. Direct measurement of vertical concentration flux requires high frequency temporal sampling and increases the cost and complexity of the measurement system.

Annual variability of ozone along alpine hillsides

NASA Technical Reports Server (NTRS)

Putz, Erich; Kosmus, Walter

1994-01-01

Over a period of more than two years (March 1989 till June 1991) ozone and nitrogen dioxide have been monitored along twelve alpine hillsides in the Austrian alps. The profiles had a height-resolution of 100 m and cover a range between 400 m and 1800 m asl, that is 100 m to 1100 m above the bottom of the valleys. They were situated in remote rural areas as well as in the vicinity of polluted urban and industrial areas. Both trace gases were monitored by means of integral chemical (SAM-surface active monitor) methods with a measuring cycle of two weeks. The concentration of ozone exhibits a substantial annual variation over the entire height range. In summer, highest ozone levels are observed near the ground and at the top of the mountains, whereas in winter the maxima are found mainly in the crest regions. The overall ozone burden shows a relative maximum near the temperature inversion layer in the valleys and an absolute maximum at the crest.

Co-Mitigation of Ozone and PM2.5 Pollution over the Beijing-Tianjin-Hebei Region

NASA Astrophysics Data System (ADS)

Liu, J.; Xiang, S.; Yi, K.; Tao, W.

2017-12-01

With the rapid industrialization and urbanization, emissions of air pollutants in China were increasing rapidly during the past few decades, causing severe particulate matter and ozone pollution in many megacities. Facing these knotty environmental problems, China has released a series of pollution control policies to mitigate air pollution emissions and optimize energy supplement structure. Consequently, fine particulate matters (PM2.5) decrease recently. However, the concentrations of ambient ozone have been increasing, especially during summer time and over megacities. In this study, we focus on the opposite trends of ozone and PM2.5 over the Beijing-Tianjin-Hebei region. We use the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem) to simulate and analyze the best emission reduction strategies, and adopt the Empirical Kinetics Modeling Approach (EKMA) to depict the influences of mitigating NOx and VOCs. We also incorporate the abatement costs for NOx and VOCs in our analysis to explore the most cost-effective mitigation strategies for both ozone and PM2.5.

Sensitivity analysis of ozone formation and transport for a central California air pollution episode.

PubMed

Jin, Ling; Tonse, Shaheen; Cohan, Daniel S; Mao, Xiaoling; Harley, Robert A; Brown, Nancy J

2008-05-15

We developed a first- and second-order sensitivity analysis approach with the decoupled direct method to examine spatial and temporal variations of ozone-limiting reagents and the importance of local vs upwind emission sources in the San Joaquin Valley of central California for a 5 day ozone episode (Jul 29th to Aug 3rd, 2000). Despite considerable spatial variations, nitrogen oxides (NO(x)) emission reductions are overall more effective than volatile organic compound (VOC) control for attaining the 8 h ozone standard in this region for this episode, in contrast to the VOC control that works better for attaining the prior 1 h ozone standard. Interbasin source contributions of NO(x) emissions are limited to the northern part of the SJV, while anthropogenic VOC (AVOC) emissions, especially those emitted at night, influence ozone formation in the SJV further downwind. Among model input parameters studied here, uncertainties in emissions of NO(x) and AVOC, and the rate coefficient of the OH + NO2 termination reaction, have the greatest effect on first-order ozone responses to changes in NO(x) emissions. Uncertainties in biogenic VOC emissions only have a modest effect because they are generally not collocated with anthropogenic sources in this region.

Comparison of Wintertime Ozone Production Associated With Oil and Gas Extraction Activity in Wyoming and Utah

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Schnell, R. C.; Mefford, T. K.; Neely, R. R., III

2012-12-01

The wintertime cold, reduced sunlight conditions of the mid-latitudes of continental interior locations are normally not considered to be conducive to significant ozone production. Recent observations have shattered this expectation with hourly ozone mixing ratios regularly exceeding 100 ppb measured in January, February and March in the states of Wyoming and Utah in the United States. Maximum daily eight hour average ozone mixing ratios have exceeded 100 ppb, far exceeding the U.S. threshold of 75 ppb. Conditions under which this dramatic ozone production takes place include a mix of high levels of ozone precursors (NOx and VOCs), a very stable and shallow boundary layer, snow cover providing enhanced UV radiation, and air confining terrain features. The high levels of precursors have been tied to oil and gas extraction activities in the affected regions. Under the requisite meteorological conditions where high pressure, low winds, and snow-covered ground are present extremely stable and shallow (~50-200 m) boundary layers persist. The highly reflective snow cover provides enhanced photolysis rates that in February can exceed those in June. For several winters in Utah and Wyoming with large ozone enhancements, the time series of various meteorological (wind, temperature, solar radiation, snow cover) and chemical parameters (ozone and NOx) show a somewhat different progression of high ozone events between the two locations. In the Unitah Basin of Utah high ozone formation conditions are more persistent throughout the winter than in the Pinedale Anticline region of Wyoming. This is likely a function of the differing topography of the two areas. However, for individual events the two sites show a similar progression of rapid ozone formation each day. Sites in both Utah and Wyoming just outside the oil and gas extraction activity areas show little or no enhanced ozone. Winters without the requisite meteorological conditions also do not experience high ozone events.

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

Meadows, J.; Smith, R.C.

Uric acid effectively reduced hemolysis and methemoglobin formation in bovine and swine erythrocytes bubbled with ozone in vitro. In bovine erythrocytes, formation of thiobarbituric acid-reactive material was inhibited by uric acid, but there was little immediate protection for the swine cells. Antioxidant protection was due to preferential degradation of the uric acid by ozone. These results provide evidence to support the hypothesis that in plasma, uric acid can provide antioxidant protection for erythrocytes.

Polar stratospheric clouds and ozone depletion

NASA Technical Reports Server (NTRS)

Toon, Owen B.; Turco, Richard P.

1991-01-01

A review is presented of investigations into the correlation between the depletion of ozone and the formation of polar stratospheric clouds (PSCs). Satellite measurements from Nimbus 7 showed that over the years the depletion from austral spring to austral spring has generally worsened. Approximately 70 percent of the ozone above Antarctica, which equals about 3 percent of the earth's ozone, is lost during September and October. Various hypotheses for ozone depletion are discussed including the theory suggesting that chlorine compounds might be responsible for the ozone hole, whereby chlorine enters the atmosphere as a component of chlorofluorocarbons produced by humans. The three types of PSCs, nitric acid trihydrate, slowly cooling water-ice, and rapidly cooling water-ice clouds act as important components of the Antarctic ozone depletion. It is indicated that destruction of the ozone will be more severe each year for the next few decades, leading to a doubling in area of the Antarctic ozone hole.

Ozonation of cooling tower waters

NASA Technical Reports Server (NTRS)

Humphrey, M. F.; French, K. R.; Howe, R. D. (Inventor)

1979-01-01

Continuous ozone injection into water circulating between a cooling tower and heat exchanger with heavy scale deposits inhibits formation of further deposits, promotes flaking of existing deposits, inhibits chemical corrosion and controls algae and bacteria.

Organic aerosol formation in citronella candle plumes.

PubMed

Bothe, Melanie; Donahue, Neil McPherson

2010-09-01

Citronella candles are widely used as insect repellants, especially outdoors in the evening. Because these essential oils are unsaturated, they have a unique potential to form secondary organic aerosol (SOA) via reaction with ozone, which is also commonly elevated on summer evenings when the candles are often in use. We investigated this process, along with primary aerosol emissions, by briefly placing a citronella tealight candle in a smog chamber and then adding ozone to the chamber. In repeated experiments, we observed rapid and substantial SOA formation after ozone addition; this process must therefore be considered when assessing the risks and benefits of using citronella candle to repel insects.

LIDAR mapping of ozone-episode dynamics in Paris and intercomparison with spot analyzers Supplementary material available at http://link.springer.de/journals/apb

NASA Astrophysics Data System (ADS)

Thomasson, A.; Geffroy, S.; Frejafon, E.; Weidauer, D.; Fabian, R.; Godet, Y.; Nominé, M.; Ménard, T.; Rairoux, P.; Moeller, D.; Wolf, J. P.

Continuous mapping of an ozone episode in Paris in June 1999 has been performed using a differential absorption lidar system. The 2D ozone concentration vertical maps recorded over 33 h at the Champ de Mars are compiled in a video clip that gives access to local photochemical dynamics with unprecedented precision. The lidar data are compared over the whole period with point monitors located at 0-, 50-, and 300-m altitudes on the Eiffel Tower. Very good agreement is found when spatial resolution, acquisition time, and required concentration accuracy are optimized. Sensitivity to these parameters for successful intercomparison in urban areas is discussed.

Constant volume balloons measurements in the urban Marseille and Fos-Berre industrial ozone plumes during ESCOMPTE experiment

NASA Astrophysics Data System (ADS)

Bénech, Bruno; Ezcurra, Agustin; Lothon, Marie; Saïd, Frédérique; Campistron, Bernard; Lohou, Fabienne; Durand, Pierre

ESCOMPTE programme aims at studying the emissions of primary pollutants in industrial and urban areas, their transport, diffusion and transformation in the atmosphere. This experiment, carried out in southeast France, can be used to validate and to improve meteorological and chemical mesoscale models. One major goal of this experiment was to follow the pollutant plumes, and to investigate its thermodynamic and physico-chemical time evolution. This was realized by means of constant volume balloons, located by global position satellite (GPS) and equipped with thermodynamic and ozone sensors, flying at constant density levels. During the two ESCOMPTE campaigns that took place in June and July 2000 and 2001, 40 balloons were launched, 17 of them equipped with ozone sensors during the day from 0800 to 1800 UTC. Balloons' altitudes flight levels ranged between 400 and 1200 m altitude with Mistral (northerly synoptic flow) and Sea Breeze (southerly breeze) conditions. The atmospheric boundary layer (ABL) topography of the experimental domain is complex and varies strongly from day to day. Its depth presents a large gradient from the sea coast to the north part of the ESCOMPTE domain, and also more complex variability within the domain. The balloons' trajectories describe the evolution of the pollutant plume emitted from the industrial area of Fos-Berre or from the Marseille urban area. Constant volume balloons give a good description of the trajectories of these two plumes. The balloons, which fly at an isopicnic level, cross different atmospheric layers chiefly depending on the ABL height in relation with the constant volume balloons flight level. Thus, each balloon flight is decomposed into different segments that correspond to the same atmospheric layer. In each segment, the ozone content variation is analyzed in relation to other thermodynamical parameters measured by the balloon and mainly to the vapor mixing ratio content. During ESCOMPTE campaign, the mean linear rate of chemical net ozone production at the top of the atmospheric boundary layer was found to be around 6 ppb h -1.

An Integrated Approach to Economic and Environmental Aspects of Air Pollution and Climate Interactions

NASA Astrophysics Data System (ADS)

Sarofim, M. C.

2007-12-01

Emissions of greenhouses gases and conventional pollutants are closely linked through shared generation processes and thus policies directed toward long-lived greenhouse gases affect emissions of conventional pollutants and, similarly, policies directed toward conventional pollutants affect emissions of greenhouse gases. Some conventional pollutants such as aerosols also have direct radiative effects. NOx and VOCs are ozone precursors, another substance with both radiative and health impacts, and these ozone precursors also interact with the chemistry of the hydroxyl radical which is the major methane sink. Realistic scenarios of future emissions and concentrations must therefore account for both air pollution and greenhouse gas policies and how they interact economically as well as atmospherically, including the regional pattern of emissions and regulation. We have modified a 16 region computable general equilibrium economic model (the MIT Emissions Prediction and Policy Analysis model) by including elasticities of substitution for ozone precursors and aerosols in order to examine these interactions between climate policy and air pollution policy on a global scale. Urban emissions are distributed based on population density, and aged using a reduced form urban model before release into an atmospheric chemistry/climate model (the earth systems component of the MIT Integrated Global Systems Model). This integrated approach enables examination of the direct impacts of air pollution on climate, the ancillary and complementary interactions between air pollution and climate policies, and the impact of different population distribution algorithms or urban emission aging schemes on global scale properties. This modeling exercise shows that while ozone levels are reduced due to NOx and VOC reductions, these reductions lead to an increase in methane concentrations that eliminates the temperature effects of the ozone reductions. However, black carbon reductions do have significant direct effects on global mean temperatures, as do ancillary reductions of greenhouse gases due to the pollution constraints imposed in the economic model. Finally, we show that the economic benefits of coordinating air pollution and climate policies rather than separate implementation are on the order of 20% of the total policy cost.

Potential sources of nitrous acid (HONO) and their impacts on ozone: A WRF-Chem study in a polluted subtropical region

NASA Astrophysics Data System (ADS)

Zhang, Li; Wang, Tao; Zhang, Qiang; Zheng, Junyu; Xu, Zheng; Lv, Mengyao

2016-04-01

Current chemical transport models commonly undersimulate the atmospheric concentration of nitrous acid (HONO), which plays an important role in atmospheric chemistry, due to the lack or inappropriate representations of some sources in the models. In the present study, we parameterized up-to-date HONO sources into a state-of-the-art three-dimensional chemical transport model (Weather Research and Forecasting model coupled with Chemistry: WRF-Chem). These sources included (1) heterogeneous reactions on ground surfaces with the photoenhanced effect on HONO production, (2) photoenhanced reactions on aerosol surfaces, (3) direct vehicle and vessel emissions, (4) potential conversion of NO2 at the ocean surface, and (5) emissions from soil bacteria. The revised WRF-Chem was applied to explore the sources of the high HONO concentrations (0.45-2.71 ppb) observed at a suburban site located within complex land types (with artificial land covers, ocean, and forests) in Hong Kong. With the addition of these sources, the revised model substantially reproduced the observed HONO levels. The heterogeneous conversions of NO2 on ground surfaces dominated HONO sources contributing about 42% to the observed HONO mixing ratios, with emissions from soil bacterial contributing around 29%, followed by the oceanic source (~9%), photochemical formation via NO and OH (~6%), conversion on aerosol surfaces (~3%), and traffic emissions (~2%). The results suggest that HONO sources in suburban areas could be more complex and diverse than those in urban or rural areas and that the bacterial and/or ocean processes need to be considered in HONO production in forested and/or coastal areas. Sensitivity tests showed that the simulated HONO was sensitive to the uptake coefficient of NO2 on the surfaces. Incorporation of the aforementioned HONO sources significantly improved the simulations of ozone, resulting in increases of ground-level ozone concentrations by 6-12% over urban areas in Hong Kong and the Pearl River Delta region. This result highlights the importance of accurately representing HONO sources in simulations of secondary pollutants over polluted regions.

Observational Insights into N2O5 Heterogeneous Chemistry: Influencing Factors and Contribution to Wintertime Air Pollution

NASA Astrophysics Data System (ADS)

McDuffie, E. E.; Fibiger, D. L.; Womack, C.; Dube, W. P.; Lopez-Hilfiker, F.; Goldberger, L.; Thornton, J. A.; Shah, V.; Jaegle, L.; Guo, H.; Weber, R. J.; Schroder, J. C.; Campuzano Jost, P.; Jimenez, J. L.; Franchin, A.; Middlebrook, A. M.; Baasandorj, M.; Brown, S. S.

2017-12-01

Chemical mechanisms that underlie wintertime air pollution, including tropospheric ozone and aerosol nitrate, are poorly characterized. Due to colder temperatures and fewer hours of solar radiation, nocturnal heterogeneous uptake of N2O5 plays a relatively larger role during wintertime in controlling the oxidation of NOx (=NO+NO2) and its influence on ozone and soluble nitrate. After uptake to aerosol, N2O5 can act as both a nocturnal NOx reservoir and sink depending on the partitioning between its nitric acid and photo labile, ClNO2 reaction products. In addition, N2O5 itself can act as a NOx reservoir if the aerosol uptake coefficient is small. As a result, the nocturnal fate of N2O5 dictates the amount of NOx in an air parcel and the subsequent formation of aerosol nitrate and following-day ozone. Models of winter air pollution therefore require accurate parameterization of the N2O5 uptake coefficient, as well as factors that control its magnitude and N2O5 product partitioning. There are currently only a small number of ambient N2O5 and ClNO2 observations during the winter season concurrent with measurements of relevant variables such as aerosol size distributions and composition. The Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign conducted 10 nighttime research flights with the NCAR C-130 over the eastern U.S. during February and March, 2015. The more recent Utah Wintertime Fine Particulate Study (UWFPS) conducted over 20 research flights with the NOAA twin otter aircraft during January-February 2017 in three mountain basins near and including Salt Lake City, Utah. The two campaigns were similarly instrumented and have provided the first aircraft observations of N2O5, ClNO2, and aerosol composition in the wintertime boundary layer in these urban-influenced regions. Analysis of heterogeneous chemistry under a wide range of real environmental conditions provides insight into the factors controlling the N2O5 uptake coefficient, product partitioning, and contribution of N2O5 to wintertime pollution events in urban regions across the U.S.

User's guide for SBUV/TOMS ozone derivative products

NASA Technical Reports Server (NTRS)

Fleig, A. J.; Wellemeyer, C.; Oslik, N.; Lee, D.; Miller, J.; Magatani, R.

1984-01-01

A series of products are available derived from the total-ozone and ozone vertical profile results for the Solar Backscattered Ultraviolet/Total-Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus-7 operation. Products available are (1) orbital height-latitude cross sections of the SBUV profile data, (2) daily global total ozone contours in polar coordinates, (3) daily averages of total ozone in global 5x5 degree latitude-longitude grid, (4) daily, monthly and quarterly averages of total ozone and profile data in 10 degree latitude zones, (5) tabular presentation of zonal means, (6) daily global total ozone and profile contours in polar coordinates. The ""Derivative Products User's Guide'' describes each of these products in detail, including their derivation and presentation format. Information is provided on how to order the tapes and microfilm from the National Space Science Data Center.

The effect of pre-oxidation on NDMA formation and the influence of pH.

PubMed

Selbes, Meric; Kim, Daekyun; Karanfil, Tanju

2014-12-01

N-nitrosodimethylamine (NDMA), a probable human carcinogen, is a disinfection by-product that has been detected in chloraminated drinking water systems. Pre-oxidation of the NDMA precursors prior to chloramination can be a viable approach for water utilities to control the NDMA levels. This study examined the effects of (i) commonly used oxidants (i.e., chlorine, chlorine dioxide and ozone) in water treatment, (ii) oxidant concentration and contact time (CT), and (iii) pre-oxidation pH on the formation of NDMA from subsequent chloramination. Fifteen model precursors with NDMA molar yields ranging from approximately 0.1%-90% were examined. Pre-chlorination reduced NDMA formation from most precursors by 10%-50% except quaternary amine polymers (i.e., PolyDADMAC, PolyACRYL, PolyAMINE). Pre-oxidation with chlorine dioxide and ozone achieved the same or higher deactivation of NDMA precursors (e.g., ranitidine) while increasing NDMA formation for some other precursors (e.g., daminozid). The increases with chlorine dioxide exposure were attributed to the release of oxidation products with dimethylamine (DMA) moiety, which may form more NDMA upon chloramination than the unoxidizied parent compound. On the other hand, chlorine dioxide was effective, if a precursors NDMA yield were higher than DMA. The ozone-triggered increases could be related to direct NDMA formation from DMA which are released by ozonation of amines with DMA moiety, amides or hydrazines. However, hydroxyl radicals formed from the decomposition of ozone would be also involved in decomposition of formed NDMA, reducing the overall NDMA levels at longer contact times. pH conditions influenced significantly the effectiveness of deactivation of precursors depending on the type of precursor and oxidant used. Copyright © 2014 Elsevier Ltd. All rights reserved.

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.

78 FR 11583 - Approval and Promulgation of Implementation Plans Tennessee: Revisions to Volatile Organic...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-19

... exclusion list for VOC on the basis that they have a negligible effect on tropospheric ozone formation. Tropospheric ozone, commonly known as smog, occurs when VOC and nitrogen oxide (NO X ) react in the atmosphere. Because of the harmful health effects of ozone, EPA limits the amount of VOC and NO X that can be released...

Modeling ozone and aerosol formation and transport in the pacific northwest with the community Multi-Scale Air Quality (CMAQ) modeling system.

PubMed

O'Neill, Susan M; Lamb, Brian K; Chen, Jack; Claiborn, Candis; Finn, Dennis; Otterson, Sally; Figueroa, Cristiana; Bowman, Clint; Boyer, Mike; Wilson, Rob; Arnold, Jeff; Aalbers, Steven; Stocum, Jeffrey; Swab, Christopher; Stoll, Matt; Dubois, Mike; Anderson, Mary

2006-02-15

The Community Multi-Scale Air Quality (CMAQ) modeling system was used to investigate ozone and aerosol concentrations in the Pacific Northwest (PNW) during hot summertime conditions during July 1-15, 1996. Two emission inventories (El) were developed: emissions for the first El were based upon the National Emission Trend 1996 (NET96) database and the BEIS2 biogenic emission model, and emissions for the second El were developed through a "bottom up" approach that included biogenic emissions obtained from the GLOBEIS model. The two simulations showed that elevated PM2.5 concentrations occurred near and downwind of the Interstate-5 corridor along the foothills of the Cascade Mountains and in forested areas of central Idaho. The relative contributions of organic and inorganic aerosols varied by region, but generally organic aerosols constituted the largest fraction of PM2.5. In wilderness areas near the 1-5 corridor, organic carbon from anthropogenic sources contributed approximately 50% of the total organic carbon with the remainder from biogenic precursors, while in wilderness areas in Idaho, biogenic organic carbon accounted for 80% of the total organic aerosol. Regional analysis of the secondary organic aerosol formation in the Columbia River Gorge, Central Idaho, and the Olympics/Puget Sound showed that the production rate of secondary organic carbon depends on local terpene concentrations and the local oxidizing capacity of the atmosphere, which was strongly influenced by anthropogenic emissions. Comparison with observations from 12 IMPROVE sites and 21 ozone monitoring sites showed that results from the two El simulations generally bracketed the average observed PM parameters and that errors calculated for the model results were within acceptable bounds. Analysis across all statistical parameters indicated that the NW-AIRQUEST El solution performed better at predicting PM2.5, PM1, and beta(ext) even though organic carbon PM was over-predicted, and the NET96 El solution performed better with regard to the inorganic aerosols. For the NW-AIRQUEST El solution, the normalized bias was 30% and the normalized absolute error was 49% for PM2.5 mass. The NW-AIRQUEST solution slightly overestimated peak hourly ozone downwind of urban areas, while the NET96 solution slightly underestimated peak values, and both solutions over-predicted average 03 concentrations across the domain by approximately 6 ppb.

Forests and ozone: productivity, carbon storage, and feedbacks.

PubMed

Wang, Bin; Shugart, Herman H; Shuman, Jacquelyn K; Lerdau, Manuel T

2016-02-22

Tropospheric ozone is a serious air-pollutant, with large impacts on plant function. This study demonstrates that tropospheric ozone, although it damages plant metabolism, does not necessarily reduce ecosystem processes such as productivity or carbon sequestration because of diversity change and compensatory processes at the community scale ameliorate negative impacts at the individual level. This study assesses the impact of ozone on forest composition and ecosystem dynamics with an individual-based gap model that includes basic physiology as well as species-specific metabolic properties. Elevated tropospheric ozone leads to no reduction of forest productivity and carbon stock and to increased isoprene emissions, which result from enhanced dominance by isoprene-emitting species (which tolerate ozone stress better than non-emitters). This study suggests that tropospheric ozone may not diminish forest carbon sequestration capacity. This study also suggests that, because of the often positive relationship between isoprene emission and ozone formation, there is a positive feedback loop between forest communities and ozone, which further aggravates ozone pollution.

Comparing Model Ozone Loss during the SOLVE and SOLVE-2 Winters

NASA Technical Reports Server (NTRS)

Drdla, K.

2003-01-01

Model simulations have been used to analyze the factors influencing ozone loss during the 1999-2000 and 2002-2003 js. For both winters, the evolution of the Arctic vortex from November to April has been simulated using a trajectory-based microphysical and photochemical model. Extensive PSC formation and strong ozone depletion are evident in both winters. However, the ozone loss begins earlier in the 2002-2003 winter, with significant ozone depletion by early January. Analysis of the model results shows that during December 2002 not only cold temperatures but also the vortex structure was critical, allowing PSC-processed air parcels to experience significant solar exposure. The resultant ozone loss can be differentiated from ozone loss that occurs in the springtime, in particular because of the continued exposure to PSCs. For example, chlorine reactivation by the PSCs causes ozone loss to be insensitive to denitrification. Therefore, diagnosing the extent of ozone loss early in the winter is critical In understanding the overall winter-long ozone depletion.

Response surface modeling-based source contribution analysis and VOC emission control policy assessment in a typical ozone-polluted urban Shunde, China.

PubMed

You, Zhiqiang; Zhu, Yun; Jang, Carey; Wang, Shuxiao; Gao, Jian; Lin, Che-Jen; Li, Minhui; Zhu, Zhenghua; Wei, Hao; Yang, Wenwei

2017-01-01

To develop a sound ozone (O 3 ) pollution control strategy, it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O 3 . Using the "Shunde" city as a pilot summer case study, we apply an innovative response surface modeling (RSM) methodology based on the Community Multi-Scale Air Quality (CMAQ) modeling simulations to identify the O 3 regime and provide dynamic analysis of the precursor contributions to effectively assess the O 3 impacts of volatile organic compound (VOC) control strategy. Our results show that Shunde is a typical VOC-limited urban O 3 polluted city. The "Jiangmen" city, as the main upper wind area during July 2014, its VOCs and nitrogen oxides (NO x ) emissions make up the largest contribution (9.06%). On the contrary, the contribution from local (Shunde) emission is lowest (6.35%) among the seven neighbor regions. The local VOCs industrial source emission has the largest contribution comparing to other precursor emission sectors in Shunde. The results of dynamic source contribution analysis further show that the local NO x control could slightly increase the ground O 3 under low (10.00%) and medium (40.00%) reduction ratios, while it could start to turn positive to decrease ground O 3 under the high NO x abatement ratio (75.00%). The real-time assessment of O 3 impacts from VOCs control strategies in Pearl River Delta (PRD) shows that the joint regional VOCs emission control policy will effectively reduce the ground O 3 concentration in Shunde. Copyright © 2016. Published by Elsevier B.V.

Bromine-Chlorine Coupling in the Antarctic Ozone Hole

NASA Technical Reports Server (NTRS)

Danilin, Michael Y.; Sze, Nien-Dak; Ko, Malcolm K. W.; Rodriquez, Jose M.; Prather, Michael J.

1996-01-01

The contribution from the chlorine and bromine species in the formation of the Antarctic ozone hole is evaluated. Since chlorine and bromine compounds are of different industrial origin, it is desirable, from a policy point of view, to be able to attribute chlorine-catalyzed loss of ozone with those reactions directly involving chlorine species, and likewise for bromine-catalyzed loss. In the stratosphere, however, most of the chemical families are highly coupled, and, for example, changes in the chlorine abundance will alter the partitioninig in other families and thus the rate of ozone loss. This modeling study examines formation of the Antarctic ozone hole for a wide range of bromine concentrations (5 - 25 pptv) and for chlorine concentrations typical of the last two decades (1.5, 2.5 and 3.5 ppbv). We follow the photochemical evolution of a single parcel of air, typical of the inner Antarctic vortex (50 mbar, 70 deg. S, NO(sub y) = 2 ppbv, with Polar Stratospheric Clouds(PSC)) from August 1 to November 1. For all of these ranges of chlorine and bromine loading, we would predict a substantial ozone hole (local depletion greater than 90%) within the de-nitrified, PSC- perturbed vortex. The contributions of the different catalytic cycles responsible for ozone loss are tabulated. The deep minimum in ozone is driven primarily by the chlorine abundance. As bromine levels decrease, the magnitude of the chlorine-catalyzed ozone loss increases to take up the slack. This is because bromine suppresses ClO by accelerating the conversion of ClO an Cl2O2 back to HCI. For this range of conditions, the local relative efficiency of ozone destruction per bromine atom to that per chlorine atom (alpha-factor) ranges from 33 to 55, decreasing with increase of bromine.

The 1979 Southeastern Virginia Urban Plume Study. Volume 2: Data listings for NASA Cessna aircraft

NASA Technical Reports Server (NTRS)

Gregory, G. L.; Lee, R. B., III; Mathis, J. J., Jr.

1981-01-01

The data reported are these measured onboard the NASA Langley chartered Cessna aircraft. Data include ozone, nitrogen oxides, light scattering coefficient, temperature, dewpoint, and aircraft altitude.

Removal of micropollutants from Sakarya River water by ozone and membrane processes.

PubMed

Yaman, Fatma Büşra; Çakmakcı, Mehmet; Yüksel, Ebubekir; Özen, İsmail; Gengeç, Erhan

2017-09-01

The removal of some pollutants in the Sakarya River was investigated in this study. Sakarya River located in Turkey flows from the northeast of Afyonkarahisar City to the Black Sea. Nineteen different micropollutants including trihalomethanes (THMs), haloacetic acids (HAAs), endocrine disrupting compound (EDC) and pharmaceuticals personal care product (PPCP) groups, and water quality parameters such as dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm wavelength (UV 254 ), hardness, and conductivity values were examined. To remove the micropollutants and improve the water quality, the treatment was performed with ozone, microfiltration (MF), and ultra-filtration (UF) membranes. The highest treatment efficiency was obtained with 1 mg/L ozone dosage and UP005 UF membrane. The trihalomethan formation potential (THMFP) and haloacetic acid formation potential (HAAFP) decreased with ozone + membrane at a concentration of 79 and 75%, respectively. After the treatment with ozone + membrane, the concentration of the micropollutants in the EDC and PPCP group remained below the detection limit. It was found that by using only membrane and only ozone, the maximum DOC removal efficiency achieved was 46 and 18%, respectively; and with ozone + membrane, this efficiency increased up to 82%. The results from the High-Pressure Size Exclusion Chromatography (HPSEC) analyses pointed that the substances with high molecular weight were converted into substances with low molecular weight after the treatment. The Fourier Transform Infrared (FTIR) analysis results showed that the aromatic and aliphatic functional groups in water changed after the treatment with ozone and that the peak values decreased more after the ozone + membrane treatment.

Airborne volatile organic compounds in urban and industrial locations in four developing countries

NASA Astrophysics Data System (ADS)

Do, Duc Hoai; Walgraeve, Christophe; Amare, Abebech Nuguse; Barai, Krishna Rani; Parao, Amelia Estigoy; Demeestere, Kristof; van Langenhove, Herman

2015-10-01

Volatile organic compounds (VOCs) represent an important class of air pollutants, however their concentration levels in developing countries have scarcely been reported in literature. Therefore, concentration levels of 60 VOCs were determined at 27 urban and industrial locations in seven different cities in Ethiopia, Vietnam, the Philippines and Bangladesh between 2011 and 2014. Active sampling using Tenax TA as a sorbent was employed followed by TD-GC-MS analysis using internal standard calibration. It was found that TVOCs concentration levels in Dhaka, Bangladesh (arithmetic mean: 343 and 399 μg/m3 for urban and industrial campaign, respectively) were more than 10 times higher when compared to TVOCs levels observed in Mekelle, Ethiopia. ∑BTEX concentration at street sites ranges from 36 μg/m3 in Mekelle, to 100 and 250 μg/m3 in Hanoi, Vietnam and Dhaka, Bangladesh, respectively. The indoor to outdoor concentration ratios were found to be dependent on the country, type of environment, VOC compound and outdoor reference location. The highest Ozone Formation Potential (OFP, 2150 μg/m3), calculated from the same set of seven aromatic VOCs, was obtained at the street site in Dhaka. This OFP value is a factor three and four times higher than the OFP value observed at the street sites in Hanoi, and Manila, respectively. Finally, the Cumulative Cancer Risk (CCR) calculated for four carcinogenic VOCs ranged from 97 × 10-6 in urban Mekelle to 299 × 10-6 in urban Dhaka. This work provides for the first time comparisons of CCR in urban and industrial environments in the selected developing countries.

Missing ozone-induced potential aerosol formation in a suburban deciduous forest

NASA Astrophysics Data System (ADS)

Nakayama, T.; Kuruma, Y.; Matsumi, Y.; Morino, Y.; Sato, K.; Tsurumaru, H.; Ramasamy, S.; Sakamoto, Y.; Kato, S.; Miyazaki, Y.; Mochizuki, T.; Kawamura, K.; Sadanaga, Y.; Nakashima, Y.; Matsuda, K.; Kajii, Y.

2017-12-01

As a new approach to investigating formation processes of secondary organic aerosol (SOA) in the atmosphere, ozone-induced potential aerosol formation was measured in summer at a suburban forest site surrounded by deciduous trees, near Tokyo, Japan. After passage through a reactor containing high concentrations of ozone, increases in total particle volume (average of 1.4 × 109 nm3/cm3, which corresponds to 17% that of pre-existing particles) were observed, especially during daytime. The observed aerosol formations were compared with the results of box model simulations using simultaneously measured concentrations of gaseous and particulate species. According to the model, the relative contributions of isoprene, monoterpene, and aromatic hydrocarbon oxidation to SOA formation in the reactor were 24, 21, and 55%, respectively. However, the model could explain, on average, only ∼40% of the observed particle formation, and large discrepancies between the observations and model were found, especially around noon and in the afternoon when the concentrations of isoprene and oxygenated volatile organic compounds were high. The results suggest a significant contribution of missing (unaccounted-for) SOA formation processes from identified and/or unidentified volatile organic compounds, especially those emitted during daytime. Further efforts should be made to explore and parameterize this missing SOA formation to assist in the improvement of atmospheric chemistry and climate models.

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.

Adjoint estimation of ozone climate penalties

NASA Astrophysics Data System (ADS)

Zhao, Shunliu; Pappin, Amanda J.; Morteza Mesbah, S.; Joyce Zhang, J. Y.; MacDonald, Nicole L.; Hakami, Amir

2013-10-01

adjoint of a regional chemical transport model is used to calculate location-specific temperature influences (climate penalties) on two policy-relevant ozone metrics: concentrations in polluted regions (>65 ppb) and short-term mortality in Canada and the U.S. Temperature influences through changes in chemical reaction rates, atmospheric moisture content, and biogenic emissions exhibit significant spatial variability. In particular, high-NOx, polluted regions are prominently distinguished by substantial climate penalties (up to 6.2 ppb/K in major urban areas) as a result of large temperature influences through increased biogenic emissions and nonnegative water vapor sensitivities. Temperature influences on ozone mortality, when integrated across the domain, result in 369 excess deaths/K in Canada and the U.S. over a summer season—an impact comparable to a 5% change in anthropogenic NOx emissions. As such, we suggest that NOx control can be also regarded as a climate change adaptation strategy with regard to ozone air quality.

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.

Kinetic assessment and modeling of an ozonation step for full-scale municipal wastewater treatment: micropollutant oxidation, by-product formation and disinfection.

PubMed

Zimmermann, Saskia G; Wittenwiler, Mathias; Hollender, Juliane; Krauss, Martin; Ort, Christoph; Siegrist, Hansruedi; von Gunten, Urs

2011-01-01

The kinetics of oxidation and disinfection processes during ozonation in a full-scale reactor treating secondary wastewater effluent were investigated for seven ozone doses ranging from 0.21 to 1.24 g O(3) g(-1) dissolved organic carbon (DOC). Substances reacting fast with ozone, such as diclofenac or carbamazepine (k(P, O3) > 10(4) M(-1) s(-1)), were eliminated within the gas bubble column, except for the lowest ozone dose of 0.21 g O(3) g(-1) DOC. For this low dose, this could be attributed to short-circuiting within the reactor. Substances with lower ozone reactivity (k(P, O3) < 10(4) M(-1) s(-1)) were only fully eliminated for higher ozone doses. The predictions of micropollutant oxidation based on coupling reactor hydraulics with ozone chemistry and reaction kinetics were up to a factor of 2.5 higher than full-scale measurements. Monte Carlo simulations showed that the observed differences were higher than model uncertainties. The overestimation of micropollutant oxidation was attributed to a protection of micropollutants from ozone attack by the interaction with aquatic colloids. Laboratory-scale batch experiments using wastewater from the same full-scale treatment plant could predict the oxidation of slowly-reacting micropollutants on the full-scale level within a factor of 1.5. The Rct value, the experimentally determined ratio of the concentrations of hydroxyl radicals and ozone, was identified as a major contribution to this difference. An increase in the formation of bromate, a potential human carcinogen, was observed with increasing ozone doses. The final concentration for the highest ozone dose of 1.24 g O(3) g(-1) DOC was 7.5 μg L(-1), which is below the drinking water standard of 10 μg L(-1). N-Nitrosodimethylamine (NDMA) formation of up to 15 ng L(-1) was observed in the first compartment of the reactor, followed by a slight elimination during sand filtration. Assimilable organic carbon (AOC) increased up to 740 μg AOC L(-1), with no clear trend when correlated to the ozone dose, and decreased by up to 50% during post-sand filtration. The disinfection capacity of the ozone reactor was assessed to be 1-4.5 log units in terms of total cell counts (TCC) and 0.5 to 2.5 log units for Escherichia coli (E. coli). Regrowth of up to 2.5 log units during sand filtration was observed for TCC while no regrowth occurred for E. coli. E. coli inactivation could not be accurately predicted by the model approach, most likely due to shielding of E. coli by flocs. Copyright © 2010 Elsevier Ltd. All rights reserved.

A national day with near zero emissions and its effect on primary and secondary pollutants

NASA Astrophysics Data System (ADS)

Levy, Ilan

2013-10-01

Traffic related air pollution is a major health concern in many countries. The potential costs and benefits of different abatement policies are usually estimated by either models, case studies or previously implemented intervention measures. Such estimations have, however, limited ability to predict the effect of a reduction in primary pollutants' emissions on secondary pollutants such as ozone, because of the nonlinear nature of the photochemical reactions. This study examines the short term effects of a drastic change in emissions on a national scale during the Jewish holiday of Day of Atonement (DA) in Israel. During the holiday nearly all anthropogenic emission sources are ceased for a period of 25 h, including all vehicles, commercial, industrial and recreational activities. DAs during the 15 years period of 1998-2012 are analyzed at three sites with respect to primary and secondary air pollutants, and in greater details for 2001. A dramatic decrease in primary pollutants emissions (83-98% in NO) causes an 8 ppbv increase in ozone at the urban core. Downwind (27 km), ozone decreases by only 5 ppbv. Nighttime O3 is shown to increase to 20 ppbv at the urban sites and 30 ppbv downwind. In spite of the striking reduction in emissions, changes in ozone are not greater than what is reported in the literature about less significant events like the ozone weekend effect. Changes in ambient pollution levels observed during DA provide some indication to the possible outcomes of a major change in anthropogenic emissions. These may be considered as the best case scenario for emissions reduction intervention measures and thus aid policy makers in evaluating potential benefits of such measures.

Ground-high altitude joint detection of ozone and nitrogen oxides in urban areas of Beijing.

PubMed

Chen, Pengfei; Zhang, Qiang; Quan, Jiannong; Gao, Yang; Zhao, Delong; Meng, Junwang

2013-04-01

Based on observational data of ozone (O3) and nitrogen oxide (NO(x)) mixing ratios on the ground and at high altitude in urban areas of Beijing during a period of six days in November 2011, the temporal and spatial characteristics of mixing ratios were analyzed. The major findings include: urban O3 mixing ratios are low and NO(x) mixing ratios are always high near the road in November. Vertical variations of the gases are significantly different in and above the planetary boundary layer. The mixing ratio of O3 is negatively correlated with that of NO(x) and they are positively correlated with air temperature, which is the main factor directly causing vertical variation of O3 and NO(x) mixing ratios at 600-2100 m altitude. The NO(x) mixing ratios elevated during the heating period, while the O3 mixing ratios decreased: these phenomena are more significant at high altitudes compared to lower altitudes. During November, air masses in the urban areas of Beijing are brought by northwesterly winds, which transport O3 and NO(x) at low mixing ratios. Due to Beijing's natural geographical location, northwest air currents are beneficial to the dilution and dispersion of pollutants, which can result in lower O3 and NO(x) background values in the Beijing urban area.

Ozone Production and Its Sensitivity to NOx and VOCs: Results from the DISCOVER-AQ Field Experiment, Houston 2013

NASA Astrophysics Data System (ADS)

Ren, X.; Mazzuca, G.; Loughner, C.; Estes, M. J.; Crawford, J. H.; Weinheimer, A. J.; Pickering, K. E.; Dickerson, R. R.

2016-12-01

An observation-constrained box model based on the Carbon Bond mechanism, Version 5 (CB05), was used to study photochemical processes along the NASA P-3B flight track and spirals over eight surface sites during the September 2013 Houston, Texas deployment of the NASA DISCOVER-AQ campaign. Data from this campaign provided an opportunity to examine and improve our understanding of atmospheric photochemical oxidation processes related to the formation of secondary air pollutants such as ozone (O3). O3 production and its sensitivity to NOx and VOCs were calculated at different locations and times of day. Ozone production efficiency (OPE), defined as the ratio of the ozone production rate to the NOx oxidation rate, was calculated using the observations and the simulation results of the box and Community Multiscale Air Quality (CMAQ) models. Correlation of these results with other parameters, such as radical sources and NOx mixing ratio, was also evaluated. It was generally found that O3 production tends to be more VOC sensitive in the morning along with high ozone production rates, suggesting that control of VOCs may be an effective way to control O3 in Houston. In the afternoon, O3 production was found to be mainly NOx sensitive with some exceptions. O3 production at near major emissions sources such as Deer Park was mostly VOC sensitive for the entire day, other urban areas near Moody Tower and Channelview were VOC sensitive or in the transition regime, and areas farther from downtown Houston such as Smith Point and Conroe were mostly NOx sensitive for the entire day. It was also found that the control of NOx emissions has reduced O3 concentrations over Houston, but led to larger OPE values. The results from this work strengthen our understanding of O3 production; they indicate that controlling NOx emissions will provide air quality benefits over the greater Houston metropolitan area in the long run, but in selected areas controlling VOC emissions will also be beneficial.

Ozone production and its sensitivity to NOx and VOCs: results from the DISCOVER-AQ field experiment, Houston 2013

NASA Astrophysics Data System (ADS)

Mazzuca, Gina M.; Ren, Xinrong; Loughner, Christopher P.; Estes, Mark; Crawford, James H.; Pickering, Kenneth E.; Weinheimer, Andrew J.; Dickerson, Russell R.

2016-11-01

An observation-constrained box model based on the Carbon Bond mechanism, version 5 (CB05), was used to study photochemical processes along the NASA P-3B flight track and spirals over eight surface sites during the September 2013 Houston, Texas deployment of the NASA Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign. Data from this campaign provided an opportunity to examine and improve our understanding of atmospheric photochemical oxidation processes related to the formation of secondary air pollutants such as ozone (O3). O3 production and its sensitivity to NOx and volatile organic compounds (VOCs) were calculated at different locations and times of day. Ozone production efficiency (OPE), defined as the ratio of the ozone production rate to the NOx oxidation rate, was calculated using the observations and the simulation results of the box and Community Multiscale Air Quality (CMAQ) models. Correlations of these results with other parameters, such as radical sources and NOx mixing ratio, were also evaluated. It was generally found that O3 production tends to be more VOC-sensitive in the morning along with high ozone production rates, suggesting that control of VOCs may be an effective way to control O3 in Houston. In the afternoon, O3 production was found to be mainly NOx-sensitive with some exceptions. O3 production near major emissions sources such as Deer Park was mostly VOC-sensitive for the entire day, other urban areas near Moody Tower and Channelview were VOC-sensitive or in the transition regime, and areas farther from downtown Houston such as Smith Point and Conroe were mostly NOx-sensitive for the entire day. It was also found that the control of NOx emissions has reduced O3 concentrations over Houston but has led to larger OPE values. The results from this work strengthen our understanding of O3 production; they indicate that controlling NOx emissions will provide air quality benefits over the greater Houston metropolitan area in the long run, but in selected areas controlling VOC emissions will also be beneficial.

Ozone inhibits corrosion in cooling towers

NASA Technical Reports Server (NTRS)

French, K. R.; Howe, R. D.; Humphrey, M. F.

1980-01-01

Commercially available corona discharge ozone generator, fitted onto industrial cooling tower, significantly reduces formation of scales (calcium carbonate) and corrosion. System also controls growth of algae and other microorganisms. Modification lowers cost and improves life of cooling system.

[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.

Mid-21st century air quality at the urban scale under the influence of changed climate and emissions - case studies for Paris and Stockholm

NASA Astrophysics Data System (ADS)

Markakis, Konstantinos; Valari, Myrto; Engardt, Magnuz; Lacressonniere, Gwendoline; Vautard, Robert; Andersson, Camilla

2016-02-01

Ozone, PM10 and PM2.5 concentrations over Paris, France and Stockholm, Sweden were modelled at 4 and 1 km horizontal resolutions respectively for the present and 2050 periods employing decade-long simulations. We account for large-scale global climate change (RCP-4.5) and fine-resolution bottom-up emission projections developed by local experts and quantify their impact on future pollutant concentrations. Moreover, we identify biases related to the implementation of regional-scale emission projections by comparing modelled pollutant concentrations between the fine- and coarse-scale simulations over the study areas. We show that over urban areas with major regional contribution (e.g. the city of Stockholm) the bias related to coarse-scale projections may be significant and lead to policy misclassification. Our results stress the need to better understand the mechanism of bias propagation across the modelling scales in order to design more successful local-scale strategies. We find that the impact of climate change is spatially homogeneous in both regions, implying strong regional influence. The climate benefit for ozone (daily mean and maximum) is up to -5 % for Paris and -2 % for Stockholm city. The climate benefit on PM2.5 and PM10 in Paris is between -5 and -10 %, while for Stockholm we estimate mixed trends of up to 3 % depending on season and size class. In Stockholm, emission mitigation leads to concentration reductions up to 15 % for daily mean and maximum ozone and 20 % for PM. Through a sensitivity analysis we show that this response is entirely due to changes in emissions at the regional scale. On the contrary, over the city of Paris (VOC-limited photochemical regime), local mitigation of NOx emissions increases future ozone concentrations due to ozone titration inhibition. This competing trend between the respective roles of emission and climate change, results in an increase in 2050 daily mean ozone by 2.5 % in Paris. Climate and not emission change appears to be the most influential factor for maximum ozone concentration over the city of Paris, which may be particularly interesting from a health impact perspective.

Mid-21st century air quality at the urban scale under the influence of changed climate and emissions: case studies for Paris and Stockholm

NASA Astrophysics Data System (ADS)

Markakis, K.; Valari, M.; Engardt, M.; Lacressonnière, G.; Vautard, R.; Andersson, C.

2015-10-01

Ozone, PM10 and PM2.5 concentrations over Paris, France and Stockholm, Sweden were modeled at 4 and 1 \\unit{km} horizontal resolutions respectively for the present and 2050 periods employing decade-long simulations. We account for large-scale global climate change (RCP-4.5) and fine resolution bottom-up emission projections developed by local experts and quantify their impact on future pollutant concentrations. Moreover, we identify biases related to the implementation of regional scale emission projections over the study areas by comparing modeled pollutant concentrations between the fine and coarse scale simulations. We show that over urban areas with major regional contribution (e.g., the city of Stockholm) the bias due to coarse emission inventory may be significant and lead to policy misclassification. Our results stress the need to better understand the mechanism of bias propagation across the modeling scales in order to design more successful local-scale strategies. We find that the impact of climate change is spatially homogeneous in both regions, implying strong regional influence. The climate benefit for ozone (daily average and maximum) is up to -5 % for Paris and -2 % for Stockholm city. The joined climate benefit on PM2.5 and PM10 in Paris is between -10 and -5 % while for Stockholm we observe mixed trends up to 3 % depending on season and size class. In Stockholm, emission mitigation leads to concentration reductions up to 15 % for daily average and maximum ozone and 20 % for PM and through a sensitivity analysis we show that this response is entirely due to changes in emissions at the regional scale. On the contrary, over the city of Paris (VOC-limited photochemical regime), local mitigation of NOx emissions increases future ozone concentrations due to ozone titration inhibition. This competing trend between the respective roles of emission and climate change, results in an increase in 2050 daily average ozone by 2.5 % in Paris. Climate and not emission change appears to be the most influential factor for maximum ozone concentration over the city of Paris, which may be particularly interesting in a health impact perspective.

Nighttime Chemistry and Morning Isoprene Can Drive Urban Ozone Downwind of a Major Deciduous Forest.

PubMed

Millet, Dylan B; Baasandorj, Munkhbayar; Hu, Lu; Mitroo, Dhruv; Turner, Jay; Williams, Brent J

2016-04-19

Isoprene is the predominant non-methane volatile organic compound emitted to the atmosphere and shapes tropospheric composition and biogeochemistry through its effects on ozone, other oxidants, aerosols, and the nitrogen cycle. Isoprene is emitted naturally by vegetation during daytime, when its photo-oxidation is rapid, and in the presence of nitrogen oxides (NOx) produces ozone and degrades air quality in polluted regions. Here, we show for a city downwind of an isoprene-emitting forest (St. Louis, MO) that isoprene actually peaks at night; ambient levels then endure, owing to low nighttime OH radical concentrations. Nocturnal chemistry controls the fate of that isoprene and the likelihood of a high-ozone episode the following day. When nitrate (NO3) radicals are suppressed, high isoprene persists through the night, providing photochemical fuel upon daybreak and leading to a dramatic late-morning ozone peak. On nights with significant NO3, isoprene is removed before dawn; days with low morning isoprene then have lower ozone with a more typical afternoon peak. This biogenic-anthropogenic coupling expands the daily high-ozone window and likely has an opposite O3-NOx response to what would otherwise be expected, with implications for exposure and air-quality management in cities that, like St. Louis, are downwind of major isoprene-emitting forests.

A Study of the Role of Clouds in the Relationship Between Land Use/Land Cover and the Climate and Air Quality of the Atlanta Area

NASA Technical Reports Server (NTRS)

Kidder, Stanley Q.; Hafner, Jan

2001-01-01

The goal of Project ATLANTA is to derive a better scientific understanding of how land cover changes associated with urbanization affect climate and air quality. In this project the role that clouds play in this relationship was studied. Through GOES satellite observations and RAMS modeling of the Atlanta area, we found that in Atlanta (1) clouds are more frequent than in the surrounding rural areas; (2) clouds cool the surface by shading and thus tend to counteract the warming effect of urbanization; (3) clouds reflect sunlight, which might other wise be used to produce ozone; and (4) clouds decrease biogenic emission of ozone precursors, and they probably decrease ozone concentration. We also found that mesoscale modeling of clouds, especially of small, summertime clouds, needs to be improved and that coupled mesoscale and air quality models are needed to completely understand the mediating role that clouds play in the relationship between land use/land cover change and the climate and air quality of Atlanta. It is strongly recommended that more cities be studied to strengthen and extend these results.

CMAQ modeling of near-ground ozone pollution during the CAREBeijing-2006 campaign in Beijing, China

NASA Astrophysics Data System (ADS)

Wang, Xuesong; Song, Yu; Zhang, Yuanhang; Hu, Min; Zeng, Limin; Zhu, Tong

2010-05-01

The Community Multiscale Air Quality (CMAQ) modeling system, a 3-D regional chemical transport model, was used to simulate the O3 episodes during the Campaign of Air Quality Research in Beijing and surrounding areas in 2006 (CAREBeijing-2006). The model reproduced the temporal and spatial variations of the observed ozone and precursors well during the campaign. The modeling results showed the evolution of near ground O3 and the feature of vertical O3 profile on pollution days with different meteorological conditions. Process analysis was applied to investigate the contributions of local production and regional transport, and found different relative importance at different locations of Beijing. O3-NOx-VOCs sensitivity was also addressed with different precursor emission scenarios. The Beijing downtown area and downwind urban plume were usually in VOC-limited regime, whereas the upwind regions and northern mountain areas were generally characterized by NOx-sensitive chemistry. Ozone production efficiency of NOx was also calculated based on simulation results and compared with that derived from observations. For reducing O3 levels in Beijing, the above results suggest a regional emission control strategy with more emphasis on VOCs reduction in Beijing urban areas.

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

NASA Astrophysics Data System (ADS)

Monks, P. S.; Archibald, A. T.; Colette, A.; Cooper, O.; Coyle, M.; Derwent, R.; Fowler, D.; Granier, C.; Law, K. S.; Mills, G. E.; Stevenson, D. S.; Tarasova, O.; Thouret, V.; von Schneidemesser, E.; Sommariva, R.; Wild, O.; Williams, M. L.

2015-08-01

Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

78 FR 23149 - Air Quality: Revision to Definition of Volatile Organic Compounds-Exclusion of trans 1-chloro-3,3...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-18

... contribution to tropospheric ozone formation. Because EPA received one adverse comment, we are withdrawing the... air quality standards (NAAQS) for ozone under title I of the Clean Air Act (CAA). The direct final... of preparing SIPs to attain the NAAQS for ozone under title I of the CAA. If it had become effective...

78 FR 4796 - Approval and Promulgation of Implementation Plans; South Carolina: New Source Review-Prevention...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-23

... on the basis that they have a negligible contribution to tropospheric formation of ozone.\\17\\ EPA has... changes. \\17\\ Tropospheric ozone, commonly known as smog, occurs when VOC and nitrogen oxide (NO X ) react... for PM 2.5, PM 10 , ozone and lead that are found at Regulation 61.62-5, Standard No. 2. The four SIP...

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.

Impact of shipping emissions on ozone levels over Europe: assessing the relative importance of the Standard Nomenclature for Air Pollution (SNAP) categories.

PubMed

Tagaris, Efthimios; Stergiou, Ioannis; Sotiropoulou, Rafaella-Eleni P

2017-06-01

The impact of shipping emissions on ozone mixing ratio over Europe is assessed for July 2006 using the Community Multiscale Air Quality modeling system and the Netherlands Organization for Applied Scientific Research anthropogenic emission inventory. Results suggest that ship-induced ozone contribution to the total surface ozone exceeds 5% over the sea and near the coastline, while an increase up to 5% is simulated over a large portion of the European land. The largest impact (i.e., an increase up to 30%) is simulated over the Mediterranean Sea. In addition, shipping emissions are simulated to increase NO 2 mixing ratio more than 90%, locally, and to modify the oxidizing capacity of the atmosphere through hydroxyl radical formation (increase by 20-60% over the sea along the European coasts and near the coastal zone). Therefore, emissions from ships may counteract the benefits derived from the anthropogenic emissions reduction strategies over the continent. Simulations suggest regions where shipping emissions have a major impact on ozone mixing ratio compared to individual anthropogenic emission sector categories. Shipping emissions are estimated to play an important role on ozone levels compared to road transport sector near the coastal zone. The impact of shipping emissions on ozone formation is also profound over a great part of the European land compared to the rest of anthropogenic emission categories.

Contribution of ozone to airborne aldehyde formation in Paris homes.

PubMed

Rancière, Fanny; Dassonville, Claire; Roda, Célina; Laurent, Anne-Marie; Le Moullec, Yvon; Momas, Isabelle

2011-09-15

Indoor aldehydes may result from ozone-initiated chemistry, mainly documented by experimental studies. As part of an environmental investigation included in the PARIS birth cohort, the aim of this study was to examine ozone contribution to airborne aldehyde formation in Paris homes. Formaldehyde, acetaldehyde and hexaldehyde levels, as well as styrene, nitrogen dioxide and nicotine concentrations, comfort parameters and carbon dioxide levels, were measured twice during the first year of life of the babies. Ambient ozone concentrations were collected from the closest background station of the regional air monitoring network. Traffic-related nitrogen oxide concentrations in front of the dwellings were estimated by an air pollution dispersion model. Home characteristics and families' way of life were described by questionnaires. Stepwise multiple linear regression models were used to link aldehyde levels with ambient ozone concentrations and a few aldehyde precursors involved in oxidation reactions, adjusting for other indoor aldehyde sources, comfort parameters and traffic-related nitrogen oxides. A 4 and 11% increase in formaldehyde and hexaldehyde levels was pointed out when 8-hour ozone concentrations increased by 20 μg/m(3). The influence of potential precursors such as indoor styrene level and frequent use of air fresheners, containing unsaturated volatile organic compounds as terpenes, was also found. Thus, our results suggest that ambient ozone can significantly impact indoor air quality, especially with regard to formaldehyde and hexaldehyde levels. Copyright © 2011 Elsevier B.V. All rights reserved.

Sensitivities of NOx transformation and the effects on surface ozone and nitrate

NASA Astrophysics Data System (ADS)

Lei, H.; Wang, J. X. L.

2013-08-01

As precursors for tropospheric ozone and nitrate aerosols, Nitrogen oxides (NOx) in present atmosphere and its transformation in responding to emission and climate perturbations are studied by CAM-Chem model and air quality measurements including National Emission Inventory (NEI), Clean Air Status and Trends Network (CASTNET) and Environmental Protection Agency Air Quality System (EPA AQS). It is found that not only the surface ozone formation but also the nitrate formation is associated with the relative emissions of NOx and volatile organic compounds (VOC). Due to the availability of VOC and associated NOx titration, ozone productions in industrial regions increase in warmer conditions and slightly decrease against NOx emission increase, which is converse to the response in farming region. The decrease or small increase in ozone concentrations over industrial regions result in the responded nitrate increasing rate staying above the increasing rate of NOx emissions. It is indicated that ozone concentration change is more directly affected by changes in climate and precursor emissions, while nitrate concentration change is also affected by local ozone production types and their seasonal transfer. The sensitivity to temperature perturbations shows that warmer climate accelerates the decomposition of odd nitrogen (NOy) during the night. As a result, the transformation rate of NOx to nitrate decreases. Examinations on the historical emission and air quality records on typical pollution areas further confirm the conclusion drawn from modeling experiments.

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.

Chemical composition of gas-phase organic carbon emissions from motor vehicles and implications for ozone production.

PubMed

Gentner, Drew R; Worton, David R; Isaacman, Gabriel; Davis, Laura C; Dallmann, Timothy R; Wood, Ezra C; Herndon, Scott C; Goldstein, Allen H; Harley, Robert A

2013-10-15

Motor vehicles are major sources of gas-phase organic carbon, which includes volatile organic compounds (VOCs) and other compounds with lower vapor pressures. These emissions react in the atmosphere, leading to the formation of ozone and secondary organic aerosol (SOA). With more chemical detail than previous studies, we report emission factors for over 230 compounds from gasoline and diesel vehicles via two methods. First we use speciated measurements of exhaust emissions from on-road vehicles in summer 2010. Second, we use a fuel composition-based approach to quantify uncombusted fuel components in exhaust using the emission factor for total uncombusted fuel in exhaust together with detailed chemical characterization of liquid fuel samples. There is good agreement between the two methods except for products of incomplete combustion, which are not present in uncombusted fuels and comprise 32 ± 2% of gasoline exhaust and 26 ± 1% of diesel exhaust by mass. We calculate and compare ozone production potentials of diesel exhaust, gasoline exhaust, and nontailpipe gasoline emissions. Per mass emitted, the gas-phase organic compounds in gasoline exhaust have the largest potential impact on ozone production with over half of the ozone formation due to products of incomplete combustion (e.g., alkenes and oxygenated VOCs). When combined with data on gasoline and diesel fuel sales in the U.S., these results indicate that gasoline sources are responsible for 69-96% of emissions and 79-97% of the ozone formation potential from gas-phase organic carbon emitted by motor vehicles.

EMISSION OF OZONE IN THE VALE DO PARAÍBA REGION, IN SOUTHEASTERN BRAZIL, FOR THE YEAR 2007

NASA Astrophysics Data System (ADS)

Dos Santos Zepka, A.; Sales, A. B.; Alvalá, P. C.

2009-12-01

The city of São José dos Campos (São Paulo, Brazil) in recent years has shown strong growth and current increase in industrial economy, leading to a sharp urban development and consequent problems of air pollution. The ozone is a major greenhouse gas, present in the troposphere by photochemical reactions in natural emissions of anthropogenic and biogenic hydrocarbons such as volatile organic compounds and nitrogen oxides, which can come from lightning and soil. Due to the fact that this gas is considered the main pollutant responsible for poor air quality, the objective of this study was to characterize the behavior of the emission of ozone in the Vale do Paraíba region, in Southeastern Brazil, in association with meteorological parameters. Researches in this area are essential, because of the need for better knowledge on air quality at regional and global. The motivation for this study was based on the fact that the ozone near the surface can be considered a gas harmful to human and animal health, crops and forests as well of urban areas in general, besides being used as a major indicators of air quality by agencies of monitoring environment, such as the IPCC (Intergovernmental Panel on Climate Change), for example. This study is an initial analysis that will lead to a better understanding of chemical and physical processes that occur in the atmosphere of the city and region. Ozone and meteorological data were obtained from two locations in the city, known as INPE (23°12,04'S; 45°51,06'W) and UNIVAP (23°12,05'S; 45°57,02'W) during the year 2007. The ozone data were obtained every 15 minutes and converted in hourly and daily averages. In addition, were collected the maximum and minimum measure daily. The ozone showed similar behavior to temperature and irradiance for the period studied. In spring and summer there was an increase of ozone mixing ratio, which was produced photochemically during the increase of solar irradiance. Moreover, the periods of autumn and winter, which irradiance in São José dos Campos city is lower due to the combination between the inclination of the Earth rotation axis with the local latitude, presented a reduction in the gas mixture ratio. The daily average curves of the ozone and irradiance shown that there is a difference of approximately two hours between them. This behavior suggests that this is the time required for happen the photochemical reactions involving the production of ozone. The maximum values of ozone were observed at around 15 pm (local time), when occurred the maximum daytime temperature, increasing the production of gas compared to consumption reactions. In spring and summer (stations of higher temperatures), the daily average curve was proportional between ozone and temperature. The same relationship has not been observed in autumn and winter, because in such seasons the concentrations of ozone began to increase after the increase in temperature. Contrary to what was observed in UNIVAP, in the INPE, there were measures of the lower concentration of ozone, suggesting that perhaps this low concentration is not due the transport of ozone pollution for the region, but by the low intensity of the wind and also by higher humidity, which favors the consumption of ozone at site.

Identification of intermediates and assessment of ecotoxicity in the oxidation products generated during the ozonation of clofibric acid.

PubMed

Rosal, Roberto; Gonzalo, María S; Boltes, Karina; Letón, Pedro; Vaquero, Juan J; García-Calvo, E

2009-12-30

The degradation of an aqueous solution of clofibric acid was investigated during catalytic and non-catalytic ozonation. The catalyst, TiO(2), enhanced the production of hydroxyl radicals from ozone and raised the fraction or clofibric acid degraded by hydroxyl radicals. The rate constant for the reaction of clofibric acid and hydroxyl radicals was not affected by the presence of the catalyst. The toxicity of the oxidation products obtained during the reaction was assessed by means of Vibrio fischeri and Daphnia magna tests in order to evaluate the potential formation of toxic by-products. The results showed that the ozonation was enhanced by the presence of TiO(2,) the clofibric acid being removed completely after 15 min at pH 5. The evolution of dissolved organic carbon, specific ultraviolet absorption at 254 nm and the concentration of carboxylic acids monitored the degradation process. The formation of 4-chlorophenol, hydroquinone, 4-chlorocatechol, 2-hydroxyisobutyric acid and three non-aromatic compounds identified as a product of the ring-opening reaction was assessed by exact mass measurements performed by liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF-MS). The bioassays showed a significant increase in toxicity during the initial stages of ozonation following a toxicity pattern closely related to the formation of ring-opening by-products.

Assessment of nitrogen oxides and ground-level ozone behavior in a dense air quality station network: case study in the lesser antilles arc.

PubMed

Plocoste, Thomas; Dorville, Jean-François; Monjoly, Stéphanie; Jacoby-Koaly, Sandra; André, Maïna

2018-04-30

This paper presents a study on ground-level ozone (O 3 ), nitrogen oxides (NO x  = NO + NO 2 ) concentration and their variabilities in the ambient air of three sites of a tropical archipelago moderately urbanized. Statistical analysis were performed on quite complete (> 80%) five years of measurements (2008-2012). There are few studies on those pollutants and their seasonal behavior in the Caribbean area where pollution level and cities configuration are different from megacities. Analyses are focus on pollutant variations at the scale of the day, the week and the seasons using hourly data. The observations show that NO x concentrations are more elevated during wet season whereas O 3 concentrations are higher in dry season. Amplitudes of ozone cycles are strongly influenced by meteorological conditions (temperature, global radiation and wind speed) and prevailing levels of NO x . An ozone weekend effect is detected with the highest amplitude in the city where anthropogenic activity is the lowest during the weekend. Due to the nature and the origin of pollutants, NO x shows higher variability than O 3 on time series. Our results evince the need of continuous measurements of Volatile Organic Compounds (VOCs) in order to better quantify their contribution in O 3 formation in insular context where numerous natural sources have been identified. Implication Statement Statistical analysis of observed NO x and O 3 concentrations for five years for a typical low industrialized site of the Caribbean area have been done. Air quality for those components is correct based on the standards of the WHO, pollutant source spatial distributions and level of industrialization. Observations show the same patterns as in megacities but also a strong impact of weather conditions and road traffic. Behaviors of O 3 cannot be fully explained without VOCs monitoring. Localization and type of AQS should be reconsidered to improve the accuracy of concentrations of the pollutant and better understand their behaviors.

77 FR 50021 - Revisions to the California State Implementation Plan, San Joaquin Valley Unified Air Pollution...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-20

..., such as owners of mobile sources that also contribute to ozone formation. EPA also believes that... percent of the ozone precursor emissions, while mobile sources are responsible for approximately 80...

78 FR 24997 - Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-Depleting Substances-Fire...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-29

... manufacturer submitted a late comment disagreeing with these statements and indicating that hydrate formation... gem-diol hydrates and will thus not have appreciable effects in any organisms that might be exposed to...

Sensitivity-Based VOC Reactivity Calculation

EPA Science Inventory

Volatile Organic Compound (VOC) reactivity scales are used to compare the ozone-forming potentials of various compounds. The comparison allows for substitution of compounds to lessen formation of ozone from paints, solvents, and other products. Current reactivity scales for VOC c...

Kinetics of the formation of ozone and nitrogen oxides due to a pulsed microwave discharge in air

NASA Astrophysics Data System (ADS)

Larin, V. F.; Rumiantsev, S. A.

1989-03-01

The paper presents results of a numerical simulation of the kinetics of plasma-chemical processes induced by a single microwave pulse in the stratosphere. It is shown that the gas temperature is one of the main factors influencing the concentration ratio of ozone and nitrogen oxides formed under the effect of a microwave pulse. Long pulses, producing considerable gas heating, favor the formation of nitrogen oxides.

Effect of trichlorofluoromethane and molecular chlorine on ozone formation by simulated solar radiation

NASA Technical Reports Server (NTRS)

Bittker, D. A.; Wong, E. L.

1977-01-01

Mixtures of air with either Cl2 or CFCl3 were photolyzed in a reaction chamber by simulated solar radiation. Ozone formation was temporarily inhibited by Cl2 and permanently inhibited by CFCl3. A chemical mechanism including gas phase and wall reactions is proposed to explain these results. The CFCl3 is assumed to be adsorbed on the chamber walls and to poison the sites for Cl destruction.

In-situ Measurements of Ozone Production Rates and Comparisons to Model-derived Production Rates During the Houston, TX and Denver, CO DISCOVER-AQ Campaigns

NASA Astrophysics Data System (ADS)

Baier, B. C.; Brune, W. H.; Miller, D. O.; Lefer, B. L.

2015-12-01

Tropospheric ozone (O3) is a secondary pollutant that has harmful effects on human and plant life. The climate and urban emissions in Houston, TX and Denver, CO can be conducive for significant ozone production and thus, high ozone events. Tighter government strategies for ozone mitigation have been proposed, which involve reducing the current EPA eight-hour ozone standard from 75 ppb to 65-70 ppb. These strategies rely on the reduction of ozone precursors in order to decrease the ozone production rate, P(O3). The changes in the ozone concentration at a certain location are dependent upon P(O3), so decreasing P(O3) can decrease ozone levels provided that it has not been transported from other areas. Air quality models test reduction strategies before they are implemented, locate ozone sources, and predict ozone episodes. Traditionally, P(O3) has been calculated by models. However, large uncertainties in model emissions inventories, chemical mechanisms, and meteorology can reduce confidence in this approach. A new instrument, the Measurement of Ozone Production Sensor (MOPS) directly measures P(O3) and can provide an alternate approach to determining P(O3). An updated version of the Penn State MOPS (MOPSv2.0) was deployed to Houston, TX and Denver, CO as a part of NASA's DISCOVER-AQ field campaign in the summers of 2013 and 2014, respectively. We present MOPS directly-measured P(O3) rates from these areas, as well as comparisons to zero-dimensional and three-dimensional modeled P(O3) using the RACM2 and MCMv2.2 mechanisms. These comparisons demonstrate the potential of the MOPS to test and evaluate model-derived P(O3), to advance the understanding of model chemical mechanisms, and to improve predictions of high ozone events.

Effect of low-level ozone fumigations on crown rust of oats

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

Heagle, A.S.

1970-02-01

Exposure of crown rust differential varieties of Avena spp. to 10 pphm ozone for 6 hr in the light for 10 days after infection with Puccinia coronata significantly reduced the growth of uredia. Urediospores produced on the plants exposed to ozone germinated as well, produced as many appressoria, and resulted in as much infection as spores produced on unexposed leaves. Exposure on dry leaves to 20 pphm ozone for 3 hr for 1-5 days did not affect urediospore germination, appressoria formation, or penetration. 9 references, 1 figure, 3 tables.

Vertical Ozone Concentration Profiles in the Middle East: WRF-Chem Predictions vs. Balloon Measurements

NASA Astrophysics Data System (ADS)

Fountoukis, C.; Ayoub, M.; Ackermann, L.; Gladich, I.; Hoehn, R.

2017-12-01

The greater Middle Eastern area is made up by more than 20 countries with over 400 million inhabitants. Due to extensive land conversion, intense industrialization and rapid urban population growth in recent years, the region's air quality is changing. High ozone levels affected by free tropospheric subsidence, long range transport and local production in large metropolitan areas of the region are of major concern. In this study we analyze data from i) continuously (24/7) operated ground monitoring stations, and ii) an ozonesonde station, operated in Doha by the Qatar Environment and Energy Research Institute coupled with simulations using a three-dimensional regional air quality model (WRF-Chem). Ozonesondes were launched at 1300 LT (1000 UTC) weekly during a summertime month (August 2015) representative of extremely hot and humid atmospheric conditions and a wintertime period (January/February 2016) of cool and dry conditions in the area. This is the first application of WRF-Chem in the Middle East focusing on vertical ozone concentrations on the lower troposphere (0 - 6 km) combined with high frequency vertical measurement (balloon) data. A triple nested model configuration has been selected with high spatial resolution over the domain of interest (2 × 2 km2). We examine different meteorological regimes and test the sensitivity of model predictions to planetary boundary layer parameterizations. Comparison of model predictions against observations show high correlation coefficients and encouragingly low biases in all meteorological variables. During wintertime, ozone is overall well predicted (Fractional Bias = -0.1) while the summertime comparison is more challenging. We suggest that the YSU scheme is more representative of the region and should be the scheme of choice in future WRF-Chem applications in the Middle East. Furthermore, we highlight the importance of revising the available anthropogenic emission inventory to account rapidly-changing urban environments of the Middle East. Results from the development of a new traffic-emissions inventory for urban environments will be discussed.

Nighttime Chemistry in the Polluted Boundary Layer (Invited)

NASA Astrophysics Data System (ADS)

Stutz, J.; Wong, K.; Tsai, C.; Pikelnaya, O.

2009-12-01

Chemistry in the urban nocturnal boundary layer (NBL) has received surprisingly little attention in the past. Surface observations often see low ozone and high NO levels, which lead to low nocturnal radical levels and consequently slow chemistry near the ground. Above the surface, however, ozone and radical levels, for example of NO3, are considerably higher, and more efficient chemical pathways for the removal of gaseous pollutants such as nitrogen oxides, ozone, and hydrocarbons, are active. The influence of nocturnal chemistry on aerosol composition is also largest aloft. These processes are poorly understood due to a lack of observations in the altitude range from 20 - 500m. The strong influence of vertical mixing and transport on the composition of the NBL poses an additional challenge, requiring the measurement of vertical concentration profiles and the use of chemical transport models for their interpretation. In addition, heterogeneous processes on the ground and on aerosol surfaces play an important role in the nocturnal atmosphere. In this presentation we will review our current understanding of nocturnal chemistry in the lowest 300m of the polluted atmosphere, with a focus on nitrogen compounds. A number of field experiments in recent years have given insight into the vertical distribution of some of the most important nocturnal trace gases in urban areas, such as ozone, NO2, NO3, N2O5, and HONO. In particular, two 6-week long experiments in Houston, TX, in 2006 and 2009, have shown the strong and persistent impact of vertical mixing on the distribution of all trace gases, as well as the chemistry in the lowest 300m of the atmosphere. These observations were accompanied by detailed meteorological observations and in-situ measurements of chemical species at 70m above the ground. The observations in Houston were interpreted with a 1D chemical transport model that allows quantification of chemistry and transport at night. Our results identify gaps in our understanding of the polluted nocturnal urban boundary layer will be discussed.

Urban Heat Islands and Their Mitigation vs. Local Impacts of Climate Change

NASA Astrophysics Data System (ADS)

Taha, H.

2007-12-01

Urban heat islands and their mitigation take on added significance, both negative and positive, when viewed from a climate-change perspective. In negative terms, urban heat islands can act as local exacerbating factors, or magnifying lenses, to the effects of regional and large-scale climate perturbations and change. They can locally impact meteorology, energy/electricity generation and use, thermal environment (comfort and heat waves), emissions of air pollutants, photochemistry, and air quality. In positive terms, on the other hand, mitigation of urban heat islands (via urban surface modifications and control of man-made heat, for example) can potentially have a beneficial effect of mitigating the local negative impacts of climate change. In addition, mitigation of urban heat islands can, in itself, contribute to preventing regional and global climate change, even if modestly, by helping reduce CO2 emissions from power plants and other sources as a result of decreased energy use for cooling (both direct and indirect) and reducing the rates of meteorology-dependent emissions of air pollutants. This presentation will highlight aspects and characteristics of heat islands, their mitigation, their modeling and quantification techniques, and recent advances in meso-urban modeling of California (funded by the California Energy Commission). In particular, the presentation will focus on results from quantitative, modeling-based analyses of the potential benefits of heat island mitigation in 1) reducing point- and area-source emissions of CO2, NOx, and VOC as a result of reduced cooling energy demand and ambient/surface temperatures, 2) reducing evaporative and fugitive hydrocarbon emissions as a result of lowered temperatures, 3) reducing biogenic hydrocarbon emissions from existing vegetative cover, 4) slowing the rates of tropospheric/ground-level ozone formation and/or accumulation in the urban boundary layer, and 5) helping improve air quality. Quantitative estimates of the above will be presented based on recent and earlier meteorological, energy, thermal environmental, emissions, and photochemical modeling studies for California and Texas.

Trends of NOx, NO2 and O3 concentrations at three different types of air quality monitoring stations in Athens, Greece

NASA Astrophysics Data System (ADS)

Mavroidis, I.; Ilia, M.

2012-12-01

This work presents a systematic analysis and evaluation of the historic and current levels of atmospheric pollution in the Athens metropolitan region, regarding nitrogen oxides (NOx = NO + NO2), ozone (O3) and the NO2/NOx and NO/NO2 concentration ratios. Hourly, daily, monthly, seasonal and annual pollutant variations are examined and compared, using the results of concentration time series from three different stations of the national network for air pollution monitoring, one urban-traffic, one urban-background and one suburban-background. Concentration data are also related to meteorological parameters. The results show that the traffic affected station of Patission Street presents the higher NOx values and the lower concentrations of O3, while it is the station with the highest number of NO2 limit exceedances. The monitoring data suggest, inter alia, that there is a change in the behaviour of the suburban-background station of Liossia at about year 2000, indicating that the exact location of this station may need to be reconsidered. Comparison of NOx concentrations in Athens with concentrations in urban areas of other countries reveal that the Patission urban-traffic station records very high NOx concentrations, while remarkably high is the ratio of NO2 concentrations recorded at the urban-traffic vs. the urban-background station in Athens, indicating the overarching role of vehicles and traffic congestion on NO2 formation. The NO2/NOx ratio in the urban-traffic station appears to be almost constant with time, while it has been increasing in other urban areas, such as London and Seoul, suggesting an increased effect of primary NO2 in these areas. Diesel passenger cars were only recently allowed in Athens and, therefore, NO2 trends should be carefully monitored since a possible increase in primary NO2 may affect compliance with NO2 air quality standards.

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

NASA Astrophysics Data System (ADS)

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

2005-03-01

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

Ozone production by corona discharges during a convective event in DISCOVER-AQ Houston

NASA Astrophysics Data System (ADS)

Kotsakis, Alexander; Morris, Gary A.; Lefer, Barry; Jeon, Wonbae; Roy, Anirban; Minschwaner, Ken; Thompson, Anne M.; Choi, Yunsoo

2017-07-01

An ozonesonde launched near electrically active convection in Houston, TX on 5 September 2013 during the NASA DISCOVER-AQ project measured a large enhancement of ozone throughout the troposphere. A separate ozonesonde was launched from Smith Point, TX (∼58 km southeast of the Houston site) at approximately the same time as the launch from Houston and did not measure that enhancement. Furthermore, ozone profiles for the descent of both sondes agreed well with the ascending Smith Point profile, suggesting a highly localized event in both space and time in which an anomalously large enhancement of 70-100 ppbv appeared in the ascending Houston ozonesonde data. Compared to literature values, such an enhancement appears to be the largest observed to date. Potential sources of the localized ozone enhancement such as entrainment of urban or biomass burning emissions, downward transport from the stratosphere, photochemical production from lightning NOx, and direct ozone production from corona discharges were investigated using model simulations. We conclude that the most likely explanation for the large ozone enhancement is direct ozone production by corona discharges. Integrating the enhancement seen in the Houston ozone profile and using the number of electrical discharges detected by the NLDN (or HLMA), we estimate a production of 2.48 × 1028 molecules of ozone per flash which falls within the range of previously recorded values (9.89 × 1026-9.82 × 1028 molecules of ozone per flash). Since there is currently no parameterization for the direct production of ozone from corona discharges we propose the implementation of an equation into a chemical transport model. Ultimately, additional work is needed to further understand the occurrence and impact of corona discharges on tropospheric chemistry on short and long timescales.

Ozone Production by Corona Discharges During a Convective Event in DISCOVER-AQ Houston

NASA Technical Reports Server (NTRS)

Kotsakis, Alexander; Morris, Gary A.; Lefer, Barry; Jeon, Wongbae; Roy, Anirban; Minschwaner, Ken; Thompson, Anne M.; Choi, Yunsoo

2017-01-01

An ozonesonde launched near electrically active convection in Houston, TX on 5 September 2013 during the NASA DISCOVER-AQ project measured a large enhancement of ozone throughout the troposphere. A separate ozonesonde was launched from Smith Point, TX (approx. 58 km southeast of the Houston site) at approximately the same time as the launch from Houston and did not measure that enhancement. Furthermore, ozone profiles for the descent of both sondes agreed well with the ascending Smith Point profile, suggesting a highly localized event in both space and time in which an anomalously large enhancement of 70 - 100 ppbv appeared in the ascending Houston ozonesonde data. Compared to literature values, such an enhancement appears to be the largest observed to date. Potential sources of the localized ozone enhancement such as entrainment of urban or biomass burning emissions, downward transport from the stratosphere, photochemical production from lightning NO(sub x), and direct ozone production from corona discharges were investigated using model simulations. We conclude that the most likely explanation for the large ozone enhancement is direct ozone production by corona discharges. Integrating the enhancement seen in the Houston ozone profile and using the number of electrical discharges detected by the NLDN (or HLMA), we estimate a production of 2.48 x 10(exp. 28) molecules of ozone per flash which falls within the range of previously recorded values (9.89 x 10(exp. 26) - 9.82 x 10)exp. 28) molecules of ozone per flash). Since there is currently no parameterization for the direct production of ozone from corona discharges we propose the implementation of an equation into a chemical transport model. Ultimately, additional work is needed to further understand the occurrence and impact of corona discharges on tropospheric chemistry on short and long timescales.

Variability of Ozone, OX and NOx in Rural and Urban Areas in Marmara Region of Turkey

NASA Astrophysics Data System (ADS)

Kasparoǧlu, Sabin; İncecik, Selahattin; Topçu, H. Sema

2017-04-01

Marmara region is located in northwest of Turkey and it is bordered by Greece and the Aegean Sea to the west, and Bulgaria, the Black Sea to the north covers about 11,000 km2. Sea of Marmara is located at the center of the region. The region has the largest population in Turkey with about 23 million inhabitants. It is Turkey's main industrial region and It is the territory which is provided by a quarter of the Turkish economy. Moreover, the region is economically the most developed area of Turkey. Its agricultural potential is very rich. For example, about 73% of the sunflower production and 30 % of corn production of Turkey is done in this region. The aim of the study is to assess the spatial and temporal variations in O3, NO, and NO2 in Marmara region of Turkey based on the analysis of hourly concentrations collected at 22 monitoring stations (7 rural and 15 urban) over three years (2013-2016). This is the first study in the region. In this way possible reasons of the results will be useful in the design of control strategies for photochemical pollution in this region. For this purpose, diurnal variations of NOx, O3 and OX were examined for rural and urban sites. The total levels of oxidant (OX) which are considered to be sum of O3 and NO2 were determined. In rural sites, NOx concentrations are generally lower than at urban and polluted sites of Marmara region. We found that usually O3 peak time in rural areas are occurred at around 15:00 LST while mean peak values vary between 70-85 µg/m3. The highest mean concentrations of NO were also observed at 09:00 LST around 35-50 µg/m3 in rural areas while varies at the highest at around 75-85 µg/m3 in polluted sites. Due to the NOx -dependent contribution corresponds to local production of ozone and the NOx -independent contribution corresponds to regional concentrations, we examined OX versus NOx for daytime (10:00-18:00LST) and nighttime (19:00-09:00LST)periods to understand the contaminants of NOx from local sources or regional contribution in the region. We found that total OX appears to increase linearly with NOx in rural sites. Moreover, 3-day isentropic HYSPLIT back-trajectory analysis ending at 500m agl for ozone season are analyzed for the ozone season (1st May to 30th September). In the presented study, the prevailing mesoscale meteorological conditions occurring during ozone season over the Marmara region are examined from the reanalysis data of NOAA ESRL. Finally, AOT40 index under EU ozone Directive are examined for vegetation and forest areas in Marmara region.

Ozone formation along the California-Mexican border region during Cal-Mex 2010 field campaign

NASA Astrophysics Data System (ADS)

Li, Guohui; Bei, Naifang; Zavala, Miguel; Molina, Luisa T.

2014-05-01

The purpose of this study is to evaluate the ozone (O3) formation along the California-Mexico border region using the WRF-CHEM model in association with the Cal-Mex 2010 field campaign. Four two-day episodes in 2010 are chosen based on plume transport patterns: 1) May 15-16 (plume north), 2) May 29-30 (plume southwest), 3) June 4-5 (plume east), and 4) June 13-14 (plume southeast). Generally, the predicted O3 spatial patterns and temporal variations agree well with the observations at the ambient monitoring sites in the San Diego-Tijuana region, but in the Calexico-Mexicali region, the model frequently underestimates the observation. In the San Diego-Tijuana region, the morning anthropogenic precursor emissions in the urbanized coastal plain are carried inland and mixed with the local biogenic emissions during transport, causing the high O3 level over the mountain region. Biogenic emissions enhance the O3 concentrations by up to 40 ppb over the mountain region in the afternoon. The factor separation approach is used to evaluate the contributions of trans-boundary transport of emissions from California and Baja California to the O3 level in the California-Mexico border region. The Baja California emissions play a minor role in the O3 formation in the San Diego region and do not seem to contribute to the O3 exceedances in the region, but have large potential to cause O3 exceedances in the Calexico region. The California emissions can considerably enhance the O3 level in the Tijuana region. Generally, the California emissions play a more important role than the Baja California emissions on O3 formation in the border region (within 40 km to the California-Mexico border). On average, the O3 concentrations in the border region are decreased by 2-4 ppb in the afternoon due to the interactions of emissions from California and Baja California. Further studies need to be conducted to improve the sea breeze simulations in the border region for evaluating O3 formation.

Characteristics, determinants, and spatial variations of ambient fungal levels in the subtropical Taipei metropolis

NASA Astrophysics Data System (ADS)

Wu, Yi-Hua; Chan, Chang-Chuan; Rao, Carol Y.; Lee, Chung-Te; Hsu, Hsiao-Hsien; Chiu, Yueh-Hsiu; Chao, H. Jasmine

This study was conducted to investigate the temporal and spatial distributions, compositions, and determinants of ambient aeroallergens in Taipei, Taiwan, a subtropical metropolis. We monitored ambient culturable fungi in Shin-Jhuang City, an urban area, and Shi-Men Township, a rural area, in Taipei metropolis from 2003 to 2004. We collected ambient fungi in the last week of every month during the study period, using duplicate Burkard portable samplers and Malt Extract Agar. The median concentration of total fungi was 1339 colony-forming units m -3 of air over the study period. The most prevalent fungi were non-sporulating fungi, Cladosporium, Penicillium, Curvularia and Aspergillus at both sites. Airborne fungal concentrations and diversity of fungal species were generally higher in urban than in rural areas. Most fungal taxa had significant seasonal variations, with higher levels in summer. Multivariate analyses showed that the levels of ambient fungi were associated positively with temperature, but negatively with ozone and several other air pollutants. Relative humidity also had a significant non-linear relationship with ambient fungal levels. We concluded that the concentrations and the compositions of ambient fungi are diverse in urban and rural areas in the subtropical region. High ambient fungal levels were related to an urban environment and environmental conditions of high temperature and low ozone levels.

N-nitrosodimethylamine (NDMA) formation potential of amine-based water treatment polymers: Effects of in situ chloramination, breakpoint chlorination, and pre-oxidation.

PubMed

Park, Sang Hyuck; Padhye, Lokesh P; Wang, Pei; Cho, Min; Kim, Jae-Hong; Huang, Ching-Hua

2015-01-23

Recent studies show that cationic amine-based water treatment polymers may be important precursors that contribute to formation of the probable human carcinogen N-nitrosodimethylamine (NDMA) during water treatment and disinfection. To better understand how water treatment parameters affect NDMA formation from the polymers, the effects of in situ chloramination, breakpoint chlorination, and pre-oxidation on the NDMA formation from the polymers were investigated. NDMA formation potential (NDMA-FP) as well as dimethylamine (DMA) residual concentration were measured from poly(epichlorohydrin dimethylamine) (polyamine) and poly(diallyldimethylammonium chloride) (polyDADMAC) solutions upon reactions with oxidants including free chlorine, chlorine dioxide, ozone, and monochloramine under different treatment conditions. The results supported that dichloramine (NHCl2) formation was the critical factor affecting NDMA formation from the polymers during in situ chloramination. The highest NDMA formation from the polymers occurred near the breakpoint of chlorination. Polymer chain breakdown and transformation of the released DMA and other intermediates were important factors affecting NDMA formation from the polymers in pre-oxidation followed by post-chloramination. Pre-oxidation generally reduced NDMA-FP of the polymers; however, the treatments involving pre-ozonation increased polyDADMAC's NDMA-FP and DMA release. The strategies for reducing NDMA formation from the polymers may include the avoidance of the conditions favorable to NHCl2 formation and the avoidance of polymer exposure to strong oxidants such as ozone. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

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

Kim, S.; Kim, S. -Y.; Lee, M.

Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NO x, SO 2,more » ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HO x (OH, HO 2, and RO 2) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with near-explicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HO x distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO 2 + HO 2 or HO 2 + RO 2) could be more efficient than radical recycling (RO 2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone–VOC–NO x sensitivity and VOC oxidation product formation rates. Overall, the NO x limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO 2 levels are positively correlated with oxygenated VOCs (OVOCs) production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher-than-expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.« less

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

DOE PAGES

Kim, S.; Kim, S. -Y.; Lee, M.; ...

2015-04-29

Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NO x, SO 2,more » ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HO x (OH, HO 2, and RO 2) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with near-explicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HO x distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO 2 + HO 2 or HO 2 + RO 2) could be more efficient than radical recycling (RO 2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone–VOC–NO x sensitivity and VOC oxidation product formation rates. Overall, the NO x limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO 2 levels are positively correlated with oxygenated VOCs (OVOCs) production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher-than-expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.« less

Impact of Model Resolution and Snow Cover Modification on the Performance of Weather Forecasting and Research (WRF) Models of Winter Conditions that Contribute to Ozone Pollution in the Uintah Basin, Eastern Utah, Winter 2013. Trang T. Tran, Marc Mansfield and Seth Lyman Bingham Research Center, Utah State University

NASA Astrophysics Data System (ADS)

Tran, T. T.; Mansfield, M. L.; Lyman, S.

2013-12-01

The Uintah Basin of Eastern Utah, USA, has experienced winter ozone pollution events with ozone concentrations exceeding the National Ambient Air Quality Standard of 75 ppb. With a total of four winter seasons of ozone sampling, winter 2013 is the worst on record for ozone pollution in the basin. Emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from oil and gas industries and other activities provide the precursors for ozone formation. The chemical mechanism of ozone formation is non-linear and complicated depending on the availability of VOCs and NOx. Moreover, meteorological conditions also play an important role in triggering ozone pollution. In the Uintah Basin, high albedo due to snow cover, a 'bowl-shaped' terrain, and strong inversions that trap precursors within the boundary layer are important factors contributing to ozone pollution. However, these local meteorological phenomena have been misrepresented by recent numerical modeling studies, probably due to misrepresenting the snow cover and complex terrain of the basin. In this study, Weather Research and Forecasting (WRF) simulations are performed on a model domain covering the entire Uintah Basin for winter 2013 (Dec 2012 - Mar 2013) to test the impacts of several grid resolutions (e.g., 4000, 1300 and 800m) and snow cover modification on performance of models of the local weather conditions of the basin. These sensitivity tests help to determine the best model configurations to produce appropriate meteorological input for air-quality simulations.

Influence of ozone and meteorological parameters on levels of polycyclic aromatic hydrocarbons in the air

NASA Astrophysics Data System (ADS)

Pehnec, Gordana; Jakovljević, Ivana; Šišović, Anica; Bešlić, Ivan; Vađić, Vladimira

2016-04-01

Concentrations of ten polycyclic aromatic hydrocarbons (PAHs) in the PM10 particle fraction were measured together with ozone and meteorological parameters at an urban site (Zagreb, Croatia) over a one-year period. Data were subjected to regression analysis in order to determine the relationship between the measured pollutants and selected meteorological variables. All of the PAHs showed seasonal variations with high concentrations in winter and autumn and very low concentrations during summer and spring. All of the ten PAHs concentrations also correlated well with each other. A statistically significant negative correlation was found between the concentrations of PAHs and ozone concentrations and concentrations of PAHs and temperature, as well as a positive correlation between concentrations of PAHs and PM10 mass concentration and relative humidity. Multiple regression analysis showed that concentrations of PM10 and ozone, temperature, relative humidity and pressure accounted for 43-70% of PAHs variability. Concentrations of PM10 and temperature were significant variables for all of the measured PAH's concentrations in all seasons. Ozone concentrations were significant for only some of the PAHs, particularly 6-ring PAHs.

Mexico City's active photochemistry: conclusions from the MCMA-2003 study

NASA Astrophysics Data System (ADS)

Brune, W.; Shirley, T.; Lesher, R.; Mao, J.; Volkamer, R.; Molina, L.; Molina, M.; Velasco, E.; Westberg, H.; Lamb, B.; Jobson, T.; Alexander, M.; Gonzalez, B. C.

2004-12-01

Mexico City Metropolitan Area's active photochemistry was studied using an extensive suite of measurements on the CENICA environmental laboratory's roof, as part of the MCMA-2003 field study. Intense morning sunlight photolyzed HONO and HCHO, producing hydrogen oxides (OH and HO2) at high rates. The HOx interacted with rush-hour volatile organic compounds (VOCs) and nitrogen oxides (NOx), amplifying the production rate of ozone and nitric acid. With typically 100 ppbv of NOx and 1 ppmC of VOCs, ozone production rates exceeded 30 ppbv/hour, routinely creating in excess of 150 ppbv of ozone, even though the midday mixed layer was more than 3 km deep. Analyses of glyoxal, a product of VOC oxidation, and the hydroperoxyl radical (HO2) indicate that MCMA's ozone production was VOC-limited during morning rush hour, when typically 1/2 of the ozone is produced, and for a significant number of days during midday and afternoon at the site. Aspects of Mexico City's active photochemistry will be compared to the observed photochemistry in U.S. urban areas.

78 FR 19994 - Approval and Promulgation of Implementation Plans; South Carolina: New Source Review-Prevention...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-03

... on the basis that they have a negligible contribution to tropospheric formation of ozone to be... table at Regulation 61-62.5, Standard No. 2 to (1) add the 2008 8-hour ozone NAAQS of 75 parts per billion, (2) amend the lead \\11\\ NAAQS to 0.15 [micro]g/m\\3\\ and (3) remove the 1-hour ozone NAAQS, which...

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.

A DIGE analysis of developing poplar leaves subjected to ozone reveals major changes in carbon metabolism.

PubMed

Bohler, Sacha; Bagard, Matthieu; Oufir, Mouhssin; Planchon, Sébastien; Hoffmann, Lucien; Jolivet, Yves; Hausman, Jean-François; Dizengremel, Pierre; Renaut, Jenny

2007-05-01

Tropospheric ozone pollution is described as having major negative effects on plants, compromising plant survival. Carbon metabolism is especially affected. In the present work, the effects of chronic ozone exposure were evaluated at the proteomic level in developing leaves of young poplar plants exposed to 120 ppb of ozone for 35 days. Soluble proteins (excluding intrinsic membrane proteins) were extracted from leaves after 3, 14 and 35 days of ozone exposure, as well as 10 days after a recovery period. Proteins (pI 4 to 7) were analyzed by 2-D DIGE experiments, followed by MALDI-TOF-TOF identification. Additional observations were obtained on growth, lesion formation, and leaf pigments analysis. Although treated plants showed large necrotic spots and chlorosis in mature leaves, growth decreased only slightly and plant height was not affected. The number of abscised leaves was higher in treated plants, but new leaf formation was not affected. A decrease in chlorophylls and lutein contents was recorded. A large number of proteins involved in carbon metabolism were identified. In particular, proteins associated with the Calvin cycle and electron transport in the chloroplast were down-regulated. In contrast, proteins associated with glucose catabolism increased in response to ozone exposure. Other identified enzymes are associated with protein folding, nitrogen metabolism and oxidoreductase activity.

Ozone impacts of natural gas development in the Haynesville Shale.

PubMed

Kemball-Cook, Susan; Bar-Ilan, Amnon; Grant, John; Parker, Lynsey; Jung, Jaegun; Santamaria, Wilson; Mathews, Jim; Yarwood, Greg

2010-12-15

The Haynesville Shale is a subsurface rock formation located beneath the Northeast Texas/Northwest Louisiana border near Shreveport. This formation is estimated to contain very large recoverable reserves of natural gas, and during the two years since the drilling of the first highly productive wells in 2008, has been the focus of intensive leasing and exploration activity. The development of natural gas resources within the Haynesville Shale is likely to be economically important but may also generate significant emissions of ozone precursors. Using well production data from state regulatory agencies and a review of the available literature, projections of future year Haynesville Shale natural gas production were derived for 2009-2020 for three scenarios corresponding to limited, moderate, and aggressive development. These production estimates were then used to develop an emission inventory for each of the three scenarios. Photochemical modeling of the year 2012 showed increases in 2012 8-h ozone design values of up to 5 ppb within Northeast Texas and Northwest Louisiana resulting from development in the Haynesville Shale. Ozone increases due to Haynesville Shale emissions can affect regions outside Northeast Texas and Northwest Louisiana due to ozone transport. This study evaluates only near-term ozone impacts, but the emission inventory projections indicate that Haynesville emissions may be expected to increase through 2020.

Enhanced degradation of p-chlorophenol in a novel pulsed high voltage discharge reactor.

PubMed

Bian, Wenjuan; Ying, Xiangli; Shi, Junwen

2009-03-15

The yields of active specie such as ozone, hydrogen peroxide and hydroxyl radical were all enhanced in a novel discharge reactor. In the reactor, the original formation rate of hydroxyl radical was 2.27 x 10(-7) mol L(-1)s(-1), which was about three times than that in the contrast reactor. Ozone was formed in gas-phase and was transferred into the liquid. The characteristic of mass transfer was better in the novel reactor than that in the contrast reactor, which caused much higher ozone concentration in liquid. The dissociation of hydrogen peroxide was more evident in the former, which promoted the formations of hydroxyl radical. The p-chlorophenol (4-CP) degradation was also enhanced. Most of the ozone transferred into the liquid and hydrogen peroxide generated by discharge could be utilized by the degradation process of 4-CP. About 97% 4-CP was removed in 36 min discharge in the novel reactor. Organic acids such as formic, acetic, oxalic, propanoic and maleic acid were generated and free chloride ions were released in the degradation process. With the formation of organic acid, the pH was decreased and the conductivity was increased.

Atmospheric Hydroxyl Radical Production from Electronically Excited NO2 and H2O

NASA Astrophysics Data System (ADS)

Li, Shuping; Matthews, Jamie; Sinha, Amitabha

2008-03-01

Hydroxyl radicals are often called the “detergent” of the atmosphere because they control the atmosphere’s capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation.

Atmospheric hydroxyl radical production from electronically excited NO2 and H2O.

PubMed

Li, Shuping; Matthews, Jamie; Sinha, Amitabha

2008-03-21

Hydroxyl radicals are often called the "detergent" of the atmosphere because they control the atmosphere's capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation.

Ozone Health Risk Assessment for Selected Urban Areas

EPA Pesticide Factsheets

The health risk assessment described in this report estimated various health effects associated with O3 exposures as well as the reduced risks for one O3 season associated with just meeting the current O3 NAAQS.

PHOTOCHEMICAL REACTIVITY OF PERCHLOROETHYLENE

EPA Science Inventory

Perchloroethylene (PCE), a solvent used in dry cleaning, has been suspected of contributing significantly to photochemical ozone/oxidant (O3/Ox) problems in urban atmospheres. Past evidence, however, was neither complete nor consistent. To interpret more conclusively the past evi...

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.

Ozone production, nitrogen oxides, and radical budgets in Mexico City: observations from Pico de Tres Padres

NASA Astrophysics Data System (ADS)

Wood, E. C.; Herndon, S. C.; Onasch, T. B.; Kroll, J. H.; Canagaratna, M. R.; Kolb, C. E.; Worsnop, D. R.; Neuman, J. A.; Seila, R.; Zavala, M.; Knighton, W. B.

2008-08-01

Observations at a mountain-top site within the Mexico City basin are used to characterize ozone production and destruction, the nitrogen oxide budget, and the radical budget during the MILAGRO campaign. An ozone production rate of ~50 ppbv/h was observed in a stagnant air mass during the afternoon of 12 March 2006, which is among the highest observed anywhere in the world. Approximately half of the ozone destruction was due to the oxidation of NO2. During this time period ozone production was VOC-limited, deduced by a comparison of the radical production rates and the formation rate of NOx oxidation products (NOz) For [NOx]/[NOy] values between 0.2 and 0.8, gas-phase HNO3 typically accounted for less than 10% of NOz and accumulation-mode particulate nitrate (NO3-(PM)) accounted for 20% 70% of NOz, consistent with high ambient NH3 concentrations. The fraction of NOz accounted for by the sum of HNO3(g) and NO3-(PM) decreased with photochemical processing. This decrease is apparent even when dry deposition of HNO3 is accounted for, and indicates that HNO3 formation decreased relative to other NOx "sink" processes during the first 12 h of photochemistry and/or a significant fraction of the nitrate was associated with the coarse aerosol size mode. The ozone production efficiency of NOx on 11 and 12 March 2006 was approximately 7 on a time scale of one day. A new metric for ozone production efficiency that relates the dilution-adjusted ozone mixing ratio to cumulative OH exposure is proposed.

Atomic layer deposition of a high-k dielectric on MoS2 using trimethylaluminum and ozone.

PubMed

Cheng, Lanxia; Qin, Xiaoye; Lucero, Antonio T; Azcatl, Angelica; Huang, Jie; Wallace, Robert M; Cho, Kyeongjae; Kim, Jiyoung

2014-08-13

We present an Al2O3 dielectric layer on molybdenum disulfide (MoS2), deposited using atomic layer deposition (ALD) with ozone/trimethylaluminum (TMA) and water/TMA as precursors. The results of atomic force microscopy and low-energy ion scattering spectroscopy show that using TMA and ozone as precursors leads to the formation of uniform Al2O3 layers, in contrast to the incomplete coverage we observe when using TMA/H2O as precursors. Our Raman and X-ray photoelectron spectroscopy measurements indicate minimal variations in the MoS2 structure after ozone treatment at 200 °C, suggesting its excellent chemical resistance to ozone.