Production of N 2O 5 and ClNO 2 in summer in urban Beijing, China

Zhou, Wei; Zhao, Jian; Ouyang, Bin; Mehra, Archit; Xu, Weiqi; Wang, Yuying; Bannan, Thomas J.; Worrall, Stephen D.; Priestley, Michael; Bacak, Asan; Chen, Qi; Xie, Conghui; Wang, Qingqing; Wang, Junfeng; Du, Wei; Zhang, Yingjie; Ge, Xinlei; Ye, Penglin; Lee, James D.; Fu, Pingqing; Wang, Zifa; Worsnop, Douglas; Jones, Roderic; Percival, Carl J.; Coe, Hugh; Sun, Yele

The heterogeneous hydrolysis of dinitrogen pentoxide (inline-formulaN2O5) has a significant impact on both nocturnal particulate nitrate formation and photochemistry on the following day through the photolysis of nitryl chloride (inline-formulaClNO2), yet these processes in highly polluted urban areas remain poorly understood. Here we present measurements of gas-phase inline-formulaN2O5 and inline-formulaClNO2 by high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) during summer in urban Beijing, China as part of the Air Pollution and Human Health (APHH) campaign. inline-formulaN2O5 and inline-formulaClNO2 show large day-to-day variations with average (inline-formula±1σ) mixing ratios of inline-formula79.2±157.1 and inline-formula174.3±262.0 pptv, respectively. High reactivity of inline-formulaN2O5, with inline-formulaτ (inline-formulaN2Oinline-formula5)−1 ranging from 0.20 inline-formula× 10inline-formula−2 to 1.46 inline-formula× 10inline-formula−2 sinline-formula−1, suggests active nocturnal chemistry and a large nocturnal nitrate formation potential via inline-formulaN2O5 heterogeneous uptake. The lifetime of inline-formulaN2O5, inline-formulaτ (inline-formulaN2O5), decreases rapidly with the increase in aerosol surface area, yet it varies differently as a function of relative humidity with the highest value peaking at inline-formula∼ 40 %. The inline-formulaN2O5 uptake coefficients estimated from the product formation rates of inline-formulaClNO2 and particulate nitrate are in the range of 0.017–0.19, corresponding to direct inline-formulaN2O5 loss rates of 0.00044–0.0034 sinline-formula−1. Further analysis indicates that the fast inline-formulaN2O5 loss in the nocturnal boundary layer in urban Beijing is mainly attributed to its indirect loss via inline-formulaNO3, for example through the reactions with volatile organic compounds and NO, while the contribution of the heterogeneous uptake of inline-formulaN2O5 is comparably small (7–33 %). High inline-formulaClNO2 yields ranging from 0.10 to 0.35 were also observed, which might have important implications for air quality by affecting nitrate and ozone formation.



Zhou, Wei / Zhao, Jian / Ouyang, Bin / et al: Production of N2O5 and ClNO2 in summer in urban Beijing, China. 2018. Copernicus Publications.


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