scholarly journals Ozone production chemistry in the presence of urban plumes

2016 ◽  
Vol 189 ◽  
pp. 169-189 ◽  
Author(s):  
W. H. Brune ◽  
B. C. Baier ◽  
J. Thomas ◽  
X. Ren ◽  
R. C. Cohen ◽  
...  
Keyword(s):  
Urban Areas ◽  
Ozone Production ◽  
Ozone Pollution ◽  
Minimal Impact ◽  
Organic Species ◽  
Important Discrepancy ◽  
Measurement Suite ◽  
Ozone Photochemistry ◽  
Urban Plumes ◽  
No Emissions

Ozone pollution affects human health, especially in urban areas on hot sunny days. Its basic photochemistry has been known for decades and yet it is still not possible to correctly predict the high ozone levels that are the greatest threat. The CalNex_SJV study in Bakersfield CA in May/June 2010 provided an opportunity to examine ozone photochemistry in an urban area surrounded by agriculture. The measurement suite included hydroxyl (OH), hydroperoxyl (HO2), and OH reactivity, which are compared with the output of a photochemical box model. While the agreement is generally within combined uncertainties, measured HO2 far exceeds modeled HO2 in NOx-rich plumes. OH production and loss do not balance as they should in the morning, and the ozone production calculated with measured HO2 is a decade greater than that calculated with modeled HO2 when NO levels are high. Calculated ozone production using measured HO2 is twice that using modeled HO2, but this difference in calculated ozone production has minimal impact on the assessment of NOx-sensitivity or VOC-sensitivity for midday ozone production. Evidence from this study indicates that this important discrepancy is not due to the HO2 measurement or to the sampling of transported plumes but instead to either emissions of unknown organic species that accompany the NO emissions or unknown photochemistry involving nitrogen oxides and hydrogen oxides, possibly the hypothesized reaction OH + NO + O2 → HO2 + NO2.

scholarly journals Closing the peroxy acetyl (PA) radical budget: observations of acyl peroxy nitrates (PAN, PPN, and MPAN) during BEARPEX 2007

2009 ◽  
Vol 9 (2) ◽  
pp. 9879-9926 ◽  
Author(s):  
B. W. LaFranchi ◽  
G. M. Wolfe ◽  
J. A. Thornton ◽  
S. A. Harrold ◽  
E. C. Browne ◽  
...  
Keyword(s):  
Urban Areas ◽  
Ozone Production ◽  
Methyl Glyoxal ◽  
Good Test ◽  
Peroxy Nitrates ◽  
Detailed Evaluation ◽  
Urban Plume ◽  
No2 Formation ◽  
Urban Plumes ◽  
Detailed Chemical

Abstract. Acyl peroxy nitrates (APNs, also known as PANs) are formed from the oxidation of aldehydes and other oxygenated VOC (oVOC) in the presence of NO2. Formation of APNs suppresses NOx (NOx≡NO+NO2) in urban areas and enhances NOx downwind in urban plumes, increasing the rate of ozone production throughout an urban plume. APNs also redistribute NOx on global scales, enhancing NOx and thus ozone production. There are both anthropogenic and biogenic oVOC precursors to APNs, but a detailed evaluation of their chemistry against observations has proven elusive. Here we describe measurements of PAN, PPN, and MPAN along with the majority of chemicals that participate in their production and loss, including OH, HO2, numerous oVOC, and NO2. Observations were made during the Biosphere Effects on AeRosols and Photochemistry Experiment (BEARPEX 2007) in the outflow of the Sacramento urban plume. These observations are used to evaluate a detailed chemical model of APN ratios and concentrations. We find the ratios of APNs are nearly independent of the loss mechanisms and thus an especially good test of our understanding of their sources. We show that oxidation of methylvinyl ketone, methacrolein, methyl glyoxal, biacetyl and acetaldehyde are all significant sources of the PAN+peroxy acetyl (PA) radical reservoir, with methylvinyl ketone (MVK) often being the primary non-acetaldehyde source. At high temperatures, oxidation of non-acetaldehyde PA radical sources contributes over 60% to the total PA production rate. An analysis of absolute APN concentrations reveals a missing APN sink that can be resolved by increasing the PA+∑RO2 rate constant by a factor of 3.

scholarly journals Daytime atmospheric oxidation capacity in four Chinese megacities during the photochemically polluted season: a case study based on box model simulation

2019 ◽  
Vol 19 (6) ◽  
pp. 3493-3513 ◽  
Author(s):  
Zhaofeng Tan ◽  
Keding Lu ◽  
Meiqing Jiang ◽  
Rong Su ◽  
Hongli Wang ◽  
...  
Keyword(s):  
Urban Areas ◽  
Fine Particle ◽  
Fine Particles ◽  
Model Simulation ◽  
Ozone Production ◽  
Atmospheric Oxidation ◽  
Ozone Pollution ◽  
Oxidation Capacity ◽  
Radical Chemistry ◽  
Budget Analysis

Abstract. Atmospheric oxidation capacity is the basis for converting freshly emitted substances into secondary products and is dominated by reactions involving hydroxyl radicals (OH) during daytime. In this study, we present in situ measurements of ROx radical (hydroxy OH, hydroperoxy HO2, and organic peroxy RO2) precursors and products; the measurements are carried out in four Chinese megacities (Beijing, Shanghai, Guangzhou, and Chongqing) during photochemically polluted seasons. The atmospheric oxidation capacity is evaluated using an observation-based model and radical chemistry precursor measurements as input. The radical budget analysis illustrates the importance of HONO and HCHO photolysis, which account for ∼50 % of the total primary radical sources. The radical propagation is efficient due to abundant NO in urban environments. Hence, the production rate of secondary pollutants, that is, ozone (and fine-particle precursors (H2SO4, HNO3, and extremely low volatility organic compounds, ELVOCs) is rapid, resulting in secondary air pollution. The ozone budget demonstrates its high production in urban areas; also, its rapid transport to downwind areas results in rapid increase in local ozone concentrations. The O3–NOx–VOC (volatile organic compound) sensitivity tests show that ozone production is VOC-limited and that alkenes and aromatics should be mitigated first for ozone pollution control in the four studied megacities. In contrast, NOx emission control (that is, a decrease in NOx) leads to more severe ozone pollution. With respect to fine-particle pollution, the role of the HNO3–NO3 partitioning system is investigated using a thermal dynamic model (ISORROPIA 2). Under high relative humidity (RH) and ammonia-rich conditions, nitric acid converts into nitrates. This study highlights the efficient radical chemistry that maintains the atmospheric oxidation capacity in Chinese megacities and results in secondary pollution characterized by ozone and fine particles.

scholarly journals The effects of global changes upon regional ozone pollution in the United States

2009 ◽  
Vol 9 (4) ◽  
pp. 1125-1141 ◽  
Author(s):  
J. Chen ◽  
J. Avise ◽  
B. Lamb ◽  
E. Salathé ◽  
C. Mass ◽  
...  
Keyword(s):  
Urban Areas ◽  
The United States ◽  
Base Case ◽  
Global Changes ◽  
Ozone Pollution ◽  
Modeling Framework ◽  
Voc Emissions ◽  
The Us ◽  
The Future ◽  
Future Case

Abstract. A comprehensive numerical modeling framework was developed to estimate the effects of collective global changes upon ozone pollution in the US in 2050. The framework consists of the global climate and chemistry models, PCM (Parallel Climate Model) and MOZART-2 (Model for Ozone and Related Chemical Tracers v.2), coupled with regional meteorology and chemistry models, MM5 (Mesoscale Meteorological model) and CMAQ (Community Multi-scale Air Quality model). The modeling system was applied for two 10-year simulations: 1990–1999 as a present-day base case and 2045–2054 as a future case. For the current decade, the daily maximum 8-h moving average (DM8H) ozone mixing ratio distributions for spring, summer and fall showed good agreement with observations. The future case simulation followed the Intergovernmental Panel on Climate Change (IPCC) A2 scenario together with business-as-usual US emission projections and projected alterations in land use, land cover (LULC) due to urban expansion and changes in vegetation. For these projections, US anthropogenic NOx (NO+NO2) and VOC (volatile organic carbon) emissions increased by approximately 6% and 50%, respectively, while biogenic VOC emissions decreased, in spite of warmer temperatures, due to decreases in forested lands and expansion of croplands, grasslands and urban areas. A stochastic model for wildfire emissions was applied that projected 25% higher VOC emissions in the future. For the global and US emission projection used here, regional ozone pollution becomes worse in the 2045–2054 period for all months. Annually, the mean DM8H ozone was projected to increase by 9.6 ppbv (22%). The changes were higher in the spring and winter (25%) and smaller in the summer (17%). The area affected by elevated ozone within the US continent was projected to increase; areas with levels exceeding the 75 ppbv ozone standard at least once a year increased by 38%. In addition, the length of the ozone season was projected to increase with more pollution episodes in the spring and fall. For selected urban areas, the system projected a higher number of pollution events per year and these events had more consecutive days when DM8H ozone exceed 75 ppbv.

scholarly journals Modelling the impact of megacities on local, regional and global tropospheric ozone and the deposition of nitrogen species

2013 ◽  
Vol 13 (24) ◽  
pp. 12215-12231 ◽  
Author(s):  
Z. S. Stock ◽  
M. R. Russo ◽  
T. M. Butler ◽  
A. T. Archibald ◽  
M. G. Lawrence ◽  
...  
Keyword(s):  
Air Quality ◽  
Urban Areas ◽  
Climate Model ◽  
Surface Ozone ◽  
Global Scale ◽  
Chemical Environment ◽  
Ozone Production ◽  
The Uk ◽  
The Impact ◽  
Local Emissions

Abstract. We examine the effects of ozone precursor emissions from megacities on present-day air quality using the global chemistry–climate model UM-UKCA (UK Met Office Unified Model coupled to the UK Chemistry and Aerosols model). The sensitivity of megacity and regional ozone to local emissions, both from within the megacity and from surrounding regions, is important for determining air quality across many scales, which in turn is key for reducing human exposure to high levels of pollutants. We use two methods, perturbation and tagging, to quantify the impact of megacity emissions on global ozone. We also completely redistribute the anthropogenic emissions from megacities, to compare changes in local air quality going from centralised, densely populated megacities to decentralised, lower density urban areas. Focus is placed not only on how changes to megacity emissions affect regional and global NOx and O3, but also on changes to NOy deposition and to local chemical environments which are perturbed by the emission changes. The perturbation and tagging methods show broadly similar megacity impacts on total ozone, with the perturbation method underestimating the contribution partially because it perturbs the background chemical environment. The total redistribution of megacity emissions locally shifts the chemical environment towards more NOx-limited conditions in the megacities, which is more conducive to ozone production, and monthly mean surface ozone is found to increase up to 30% in megacities, depending on latitude and season. However, the displacement of emissions has little effect on the global annual ozone burden (0.12% change). Globally, megacity emissions are shown to contribute ~3% of total NOy deposition. The changes in O3, NOx and NOy deposition described here are useful for quantifying megacity impacts and for understanding the sensitivity of megacity regions to local emissions. The small global effects of the 100% redistribution carried out in this study suggest that the distribution of emissions on the local scale is unlikely to have large implications for chemistry–climate processes on the global scale.

scholarly journals Benzene and Toluene in the surface air of North Eurasia from TROICA-12 campaign along the Trans-Siberian railway

2016 ◽  
Author(s):  
Andrey I. Skorokhod ◽  
Elena V. Berezina ◽  
Konstantin B. Moiseenko ◽  
Nikolai F. Elansky ◽  
Igor B. Belikov
Keyword(s):  
Motor Vehicle ◽  
Regional Scale ◽  
Proton Transfer Reaction ◽  
Urban Atmosphere ◽  
Ozone Production ◽  
Anthropogenic Sources ◽  
Total Contribution ◽  
South Siberia ◽  
Ozone Photochemistry ◽  
Anthropogenic Pollutant

Abstract. Volatile organic compounds (VOCs) were measured by proton transfer reaction – mass spectrometry (PTR-MS) on a mobile laboratory in a transcontinental TROICA-12 (21.07.2008–04.08.2008) campaign along the Trans-Siberian railway from Moscow to Vladivostok. Surface concentrations of benzene (C6H6) and toluene (C7H8) along with non-methane hydrocarbons (NMHCs), CO, O3, SO2, NO, NO2 and meteorology are analyzed in this study to identify the main sources of benzene and toluene along the Trans-Siberian railway. The most measurements in the TROICA-12 campaign were conducted under low-wind/stagnant conditions in moderately (~ 78 % of measurements) to weakly polluted (~ 20 % of measurements) air directly affected by regional anthropogenic sources adjacent to the railroad. Only 2 % of measurements were identified as characteristic of highly polluted urban atmosphere. Maximum values of benzene and toluene during the campaign reached 36.5 ppb and 45.6 ppb, correspondingly, which is significantly less than their one-time maximum permissible concentrations (94 and 159 ppb for benzene and toluene, correspondingly). About 90 % of benzene and 65 % of toluene content is attributed to motor vehicle transport and 10 % and 20 %, correspondingly, provided by the other local and regional-scale sources. The highest average concentrations of benzene and toluene are measured in the industrial regions of the European Russia (up to 0.3 and 0.4 ppb for benzene and toluene, correspondingly) and south Siberia (up to 0.2 and 0.4 ppb for benzene and toluene, correspondingly). Total contribution of benzene and toluene to photochemical ozone production along the Trans-Siberian railway is about 16 % compared to the most abundant biogenic VOC – isoprene. This contribution, however, is found to be substantially higher (up to 60–70 %) in urbanized areas along the railroad suggesting important role of anthropogenic pollutant sources in regional ozone photochemistry and air quality.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

scholarly journals Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas

2011 ◽  
Vol 11 (6) ◽  
pp. 17337-17373 ◽  
Author(s):  
J. Xu ◽  
J. Z. Ma ◽  
X. L. Zhang ◽  
X. B. Xu ◽  
X. F. Xu ◽  
...  
Keyword(s):  
Rural Areas ◽  
Surface Ozone ◽  
Regional Scale ◽  
Rural Site ◽  
Traffic Density ◽  
Prevailing Wind ◽  
Ozone Pollution ◽  
Rural Sites ◽  
Urban And Rural Areas ◽  
Urban Plumes

Abstract. Sea-land and mount-valley circulations are the dominant mesoscale synoptic systems affecting the Beijing area during summertime. Under the influence of these two circulations, the prevailing wind is southwesterly from afternoon to midnight, and then changes to northeasterly till forenoon. In this study, surface ozone (O3), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxide (NOx) and non-methane hydrocarbons (NMHCs) were measured at four sites located along the route of prevailing wind, including two upwind urban sites (Fengtai (FT) and Baolian (BL)), an upwind suburban site (Shunyi (SY)) and a downwind rural site (Shangdianzi (SDZ)) during 20 June–16 September 2007. The purpose is to improve our understanding of ozone photochemistry in urban and rural areas of Beijing and the influence of urban plumes on ozone pollution in downwind rural areas. It is found that ozone pollution was synchronism in the urban and rural areas of Beijing, coinciding with the regional-scale synoptic processes. Due to the high traffic density and local emissions, the average levels of reactive gases NOx and NMHCs at the non-rural sites were much higher than those at SDZ. The level of long-lived gas CO at SDZ was comparable to and slightly lower than it was at other sites. The daily-averaged ozone concentration at SDZ was much higher than at other sites due to weak titration. Ranking by OH loss rate coefficient (LOH), alkenes played a dominant role in total NMHCs reactivity at both urban and rural sites during the experiment, accounting for 48.6 % and 52.1 % of total LOH, respectively. The NMHCs data were also used to estimate the ozone potential formation (OFP) in Beijing. The leading contributors to ozone formation were aromatics at both urban and rural sites during the experiment, which accounts for 55.5 % and 49.4 % of total OFP, respectively. The ozone peak values are found to lag behind one site after another along the route of prevailing wind from SW to NE. Intersection analyses of trace gases reveal that polluted air masses arriving at SDZ were more aged with both higher O3 and Ox concentrations than those at BL. The results indicate that urban plume can transport not only O3 but its precursors, the latter leading more photochemical O3 production when being mixed with background atmosphere in the downwind rural area.

scholarly journals Ozone production in the megacities of Tianjin and Shanghai, China: a comparative study

2012 ◽  
Vol 12 (4) ◽  
pp. 9161-9194 ◽  
Author(s):  
L. Ran ◽  
C. S. Zhao ◽  
W. Y. Xu ◽  
M. Han ◽  
X. Q. Lu ◽  
...  
Keyword(s):  
Comparative Study ◽  
Surface Ozone ◽  
Regional Scale ◽  
Yangtze River Delta ◽  
Scientific Basis ◽  
Ozone Production ◽  
Ozone Pollution ◽  
Light Alkenes ◽  
Highly Nonlinear ◽  
Ozone Precursor

Abstract. Rapid economic growth has given rise to a significant increase in ozone precursor emissions in many regions of China, especially in the densely populated North China Plain (NCP) and Yangtze River Delta (YRD). Improved understanding of ozone formation in response to different precursor emissions is imperative to address the highly nonlinear ozone problem and to provide a solid scientific basis for efficient ozone abatement in these regions. A comparative study on ozone photochemical production in summer has thus been carried out in the megacities of Tianjin (NCP) and Shanghai (YRD). Two intensive field campaigns were carried out respectively at an urban and a suburban site of Tianjin, in addition to routine monitoring of trace gases in Shanghai, providing data sets of surface ozone and its precursors including nitrogen oxides (NOx) and various volatile organic compounds (VOCs). Ozone pollution was found to be more severe in Tianjin than in Shanghai during the summer, either based on the frequency or the duration of high ozone events. Such differences might be attributed to the large amount of highly reactive VOC mixture in the Tianjin region. It is found that industry related species like light alkenes were of particular importance in both urban and suburban Tianjin, while in Shanghai aromatics dominate. In general, the ozone problem in Shanghai is on an urban scale. Stringent control policies on local emissions would help reduce the occurrence of high ozone concentrations. By contrast, ozone pollution in Tianjin is a regional problem. Combined efforts to reduce ozone precursor emissions on a regional scale must be undertaken to bring the ozone problem under control.

scholarly journals Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas

2011 ◽  
Vol 11 (23) ◽  
pp. 12241-12252 ◽  
Author(s):  
J. Xu ◽  
J. Z. Ma ◽  
X. L. Zhang ◽  
X. B. Xu ◽  
X. F. Xu ◽  
...  
Keyword(s):  
Rural Areas ◽  
Rural Site ◽  
Ozone Formation ◽  
Prevailing Wind ◽  
Ozone Pollution ◽  
Ozone Formation Potential ◽  
Rural Sites ◽  
Urban And Rural Areas ◽  
Urban Plumes ◽  
Urban Sites

Abstract. Sea-land and mount-valley circulations are the dominant mesoscale synoptic systems affecting the Beijing area during summertime. Under the influence of these two circulations, the prevailing wind is southwesterly from afternoon to midnight, and then changes to northeasterly till forenoon. In this study, surface ozone (O3), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxide (NOx) and non-methane hydrocarbons (NMHCs) were measured at four sites located along the route of prevailing wind, including two upwind urban sites (Fengtai "FT" and Baolian "BL"), an upwind suburban site (Shunyi "SY") and a downwind rural site (Shangdianzi "SDZ") during 20 June–16 September 2007. The purpose is to improve our understanding of ozone photochemistry in urban and rural areas of Beijing and the influence of urban plumes on ozone pollution in downwind rural areas. It is found that ozone pollution was synchronism in the urban and rural areas of Beijing, coinciding with the regional-scale synoptic processes. Due to the high traffic density and local emissions, the average levels of reactive gases NOx and NMHCs at the non-rural sites were much higher than those at SDZ. The level of long-lived gas CO at SDZ was comparable to, though slightly lower than, at the urban sites. We estimate the photochemical reactivity (LOH and the ozone formation potential (OFP) in the urban (BL) and rural (SDZ) areas using measured CO and NMHCs. The OH loss rate coefficient (LOH by total NMHCs at the BL and SDZ sites are estimated to be 50.7 s-1 and 15.8 s-1, respectively. While alkenes make a major contribution to the LOH, aromatics dominate OFP at both urban and rural sites. With respect to the individual species, CO has the largest ozone formation potential at the rural site, and at the urban site aromatic species are the leading contributors. While the O3 diurnal variations at the four sites are typical for polluted areas, the ozone peak values are found to lag behind one site after another along the route of prevailing wind from SW to NE. Intersection analyses of trace gases reveal that polluted air masses arriving at SDZ were more aged with both higher O3 and Ox concentrations than those at BL. The results indicate that urban plume can transport not only O3 but its precursors, the latter leading more photochemical O3 production when being mixed with background atmosphere in the downwind rural area.

scholarly journals Atmospheric oxidation capacity in Chinese megacities during photochemical polluted season: radical budget and secondary pollutants formation

2018 ◽  
Author(s):  
Zhaofeng Tan ◽  
Keding Lu ◽  
Meiqing Jiang ◽  
Rong Su ◽  
Hongli Wang ◽  
...  
Keyword(s):  
Fine Particle ◽  
Fine Particles ◽  
Nox Reduction ◽  
Ozone Production ◽  
Atmospheric Oxidation ◽  
Ozone Pollution ◽  
Oxidation Capacity ◽  
Radical Chemistry ◽  
Budget Analysis ◽  
Secondary Pollutants

Abstract. Atmospheric oxidation capacity is the core of converting fresh-emitted substances to secondary pollutants. In this study, we present the in-situ measurements at four Chinese megacities (Beijing, Shanghai, Guangzhou, and Chongqing) in China during photochemical polluted seasons. The atmospheric oxidation capacity is evaluated using an observational-based model with the input of radical chemistry precursor measurements. The radical budget analysis illustrates the importance of HONO and HCHO photolysis, which contribute nearly half of the total radical primary sources. The radical propagation is efficient due to abundant of NO in the urban environments. Hence, the production rate of secondary pollutants, i.e. ozone and fine particle precursors (H2SO4, HNO3, and ELVOCs) is fast resulting in secondary air pollution. The ozone budget demonstrates that strong ozone production occurs in the urban area which results in fast ozone concentration increase locally and further transported to downwind areas. On the other hand, the O3-NOx-VOC sensitivity tests show that ozone production is VOC-limited, among which alkenes and aromatics should be first mitigated for ozone pollution control in the presented four megacities. However, NOx emission control will lead to more server ozone pollution due to the drawback-effect of NOx reduction. For fine particle pollution, the role of HNO3−NO3− partitioning system is investigated with a thermal dynamic model (ISORROPIA2) due to the importance of particulate nitrate during photochemical polluted seasons. The strong nitrate acid production converts efficiently to nitrate particles due to high RH and ammonium-rich conditions during photochemical polluted seasons. This study highlights the efficient radical chemistry maintains the atmospheric oxidation capacity in Chinese megacities, which results in secondary pollutions characterized by ozone and fine particles.

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