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

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.

[1]  Tao Wang,et al.  Heterogeneous N2O5 uptake coefficient and production yield of ClNO2 in polluted northern China: roles of aerosol water content and chemical composition , 2018, Atmospheric Chemistry and Physics.

[2]  A. Hofzumahaus,et al.  Experimental budgets of OH, HO2, and RO2 radicals and implications for ozone formation in the Pearl River Delta in China 2014 , 2018, Atmospheric Chemistry and Physics.

[3]  S. Xie,et al.  Spatiotemporal variations of ambient volatile organic compounds and their sources in Chongqing, a mountainous megacity in China. , 2018, The Science of the total environment.

[4]  Qiang Zhang,et al.  Nitrate-driven urban haze pollution during summertime over the North China Plain , 2018 .

[5]  Qiang Zhang,et al.  Identifying Ammonia Hotspots in China Using a National Observation Network. , 2018, Environmental science & technology.

[6]  D. Blake,et al.  Observations and Explicit Modeling of Summertime Carbonyl Formation in Beijing: Identification of Key Precursor Species and Their Impact on Atmospheric Oxidation Chemistry , 2018 .

[7]  A. Lewis,et al.  Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo) , 2017 .

[8]  Tao Wang,et al.  Observations of N2O5 and ClNO2 at a polluted urban surface site in North China: High N2O5 uptake coefficients and low ClNO2 product yields , 2017 .

[9]  Tao Wang,et al.  Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China , 2016 .

[10]  Kebin He,et al.  Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China , 2016, Science Advances.

[11]  A. Hofzumahaus,et al.  OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget , 2016 .

[12]  D. Blake,et al.  Oxidative capacity and radical chemistry in the polluted atmosphere of HongKong and Pearl River Delta region: analysis of a severe photochemical smogepisode , 2016 .

[13]  A. Hofzumahaus,et al.  Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO 2 and RO 2 radicals , 2016 .

[14]  Ying Zhang,et al.  Exploring the nitrous acid (HONO) formation mechanism in winter Beijing: direct emissions and heterogeneous production in urban and suburban areas. , 2016, Faraday discussions.

[15]  R. Volkamer,et al.  Measurements of hydroxyl and hydroperoxy radicals during CalNex‐LA: Model comparisons and radical budgets , 2016 .

[16]  J. Smith,et al.  Rapid cycling of reactive nitrogen in the marine boundary layer , 2016, Nature.

[17]  D. Blake,et al.  Observations of nitryl chloride and modeling its source and effect on ozone in the planetary boundary layer of southern China , 2015 .

[18]  A. Piazzalunga,et al.  High secondary aerosol contribution to particulate pollution during haze events in China , 2014, Nature.

[19]  Chih-Chung Chang,et al.  Maximum efficiency in the hydroxyl-radical-based self-cleansing of the troposphere , 2014 .

[20]  T. Stavrakou,et al.  Hydroxyl radical recycling in isoprene oxidation driven by hydrogen bonding and hydrogen tunneling: the upgraded LIM1 mechanism. , 2014, The journal of physical chemistry. A.

[21]  T. Zhu,et al.  Daytime HONO formation in the suburban area of the megacity Beijing, China , 2014, Science China Chemistry.

[22]  H. Dorn,et al.  Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation , 2013 .

[23]  A. Ding,et al.  Ozone and fine particle in the western Yangtze River Delta: an overview of 1 yr data at the SORPES station , 2013 .

[24]  W. Stockwell,et al.  The regional atmospheric chemistry mechanism, version 2 , 2013 .

[25]  Y. H. Zhang,et al.  Missing OH source in a suburban environment near Beijing: observed and modelled OH and HO 2 concentrations in summer 2006 , 2013 .

[26]  G. Ancellet,et al.  Radical budget analysis in a suburban European site during the MEGAPOLI summer field campaign , 2012 .

[27]  Y. H. Zhang,et al.  Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China , 2011 .

[28]  Chih-Chung Chang,et al.  Observation and modelling of OH and HO 2 concentrations in the Pearl River Delta 2006: a missing OH source in a VOC rich atmosphere , 2011 .

[29]  Min Hu,et al.  Regional Integrated Experiments on Air Quality over Pearl River Delta 2004 (PRIDE-PRD2004): Overview , 2008 .

[30]  Min Shao,et al.  Regional ozone pollution and observation-based approach for analyzing ozone–precursor relationship during the PRIDE-PRD2004 campaign , 2008 .

[31]  Y. Yokouchi,et al.  Urban photochemistry in central Tokyo: 2. Rates and regimes of oxidant (O3 + NO2) production , 2008 .

[32]  K. Emmerson,et al.  Urban Atmospheric Chemistry During the PUMA Campaign 2: Radical Budgets for OH, HO2 and RO2 , 2005 .

[33]  J. Schauer,et al.  Seasonal trends in PM2.5 source contributions in Beijing, China , 2005 .

[34]  Zifa Wang,et al.  The air-borne particulate pollution in Beijing—concentration, composition, distribution and sources , 2004 .

[35]  A. Sullivan,et al.  Variability in ammonium nitrate formation and nitric acid depletion with altitude and location over California , 2003 .

[36]  A. Hofzumahaus,et al.  Measurements of OH and HO2 radical concentrations and photolysis frequencies during BERLIOZ , 2003 .

[37]  L. Kleinman,et al.  Ozone production efficiency in an urban area , 2002 .

[38]  Kebin He,et al.  The characteristics of PM2.5 in Beijing, China , 2001 .

[39]  S. Liu.  Possible effects on fropospheric O 3 and OH due to No emissions , 1977 .

[40]  Yusheng Wu,et al.  Exploration of the formation mechanism and source attribution of ambient ozone in Chongqing with an observation-based model , 2017, Science China Earth Sciences.

[41]  J. Lelieveld,et al.  Opposite OH reactivity and ozone cycles in the Amazon rainforest and megacity Beijing: Subversion of biospheric oxidant control by anthropogenic emissions , 2016 .

[42]  W. Brune,et al.  Behavior of OH and HO2 in the winter atmosphere in New York City , 2006 .