Abundant NH3 in China Enhances Atmospheric HONO Production by Promoting the Heterogeneous Reaction of SO2 with NO2

• DOI: 10.1021/acs.est.9b04196
• Publication Date: 2019-11-11T17:54:13Z
• Authors: Shuangshuang Ge; Gehui Wang; Si Zhang; Dapeng Li; Yuning Xie; Can Wu; Qi Yuan; Jianmin Chen; Hongliang Zhang
• Keywords: Haze; Oxidizing agent; Nitrous acid

High levels of HONO have frequently been observed in Chinese haze periods and underestimated by current models due to some unknown sources formation mechanisms. Combining lab-chamber simulations field measurements Xi'an Beijing, China, we found that NH3 can significantly promote via the reduction–oxidation SO2 with NO2 aqueous phase hygroscopic particles (e.g., NaCl). Concentrations formed aerosol showed an exponential increase (R2 = 0.91) under chamber conditions a linear growth two cities. The uptake coefficient on NaCl ranged from 2.0 × 10–5 1.7 10–4, 3–4 orders magnitude larger than water droplets. Our results further accounted for 4–33% total chamber, indicating aerosol-phase is important source especially periods. Since NH3, SO2, abundantly coexist positive effect could enhance atmospheric oxidizing capacity country, causing severe secondary pollution. work suggests emission control imperative mitigating air pollution China.