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Daytime atmosphericoxidation capacity infour Chinesemegacities during thephotochemicallypolluted season: acase study based onbox model simulation Zhaofeng TanKeding LuMeiqing Jiang2019 год

Daytime atmospheric oxidation capacity in four Chinese megacities during the photochemically polluted season: a case study based on box model simulation
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Аннотация: 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.
Год издания: 2019
Авторы: Zhaofeng Tan, Keding Lu, Meiqing Jiang, Rong Su, Hongli Wang, Shengrong Lou, Qingyan Fu, Chongzhi Zhai, Qinwen Tan, Dingli Yue, Duohong Chen, Zhanshan Wang, Shaodong Xie, Limin Zeng, Yuanhang Zhang
Издательство: Copernicus Publications
Источник: Atmospheric chemistry and physics
Ключевые слова: Atmospheric chemistry and aerosols, Air Quality and Health Impacts, Air Quality Monitoring and Forecasting
Другие ссылки: Atmospheric chemistry and physics (PDF)
Atmospheric chemistry and physics (HTML)
DOAJ (DOAJ: Directory of Open Access Journals) (HTML)
JuSER (Forschungszentrum Jülich) (HTML)