Exploring the amplified role of HCHO in the formation of HMS and O3 during the co-occurring PM2.5 and O3 pollution in a coastal city of southeast China

• DOI: 10.5194/acp-23-10795-2023
• Publication Date: 2023-09-28T12:39:07Z
• Authors: Youwei Hong; Keran Zhang; Dan Liao; Gaojie Chen; Min Zhao; Yiling Lin; Xiaoting Ji; Ke Xu; Yu Wu; Ruilian Yu; Gongren Hu; Sung-Deuk Choi; Likun Xue; Jinsheng Chen
• Keywords: Atmospheric chemistry

Abstract. To develop effective strategies for controlling both PM2.5 and O3 levels, it is crucial to understand their synergistic mechanisms key precursors the atmospheric physiochemical processes involved. In this study, a wintertime co-occurring pollution event in coastal city southeast China was investigated based on high-time-resolution measurements of criteria air pollutants chemical compositions PM2.5, precursors, such as NOx, HCHO, volatile organic compounds (VOCs). The results study revealed characteristics positively correlated MDA8 concentrations, an increase oxidation capacity (AOC) during cold seasons. Strong correlations (R2= 0.415–0.477) between Fe, Mn, sulfate concentrations were observed, suggesting influence catalyzed city. Through observation-based model (OBM) analysis coupled with Regional Atmospheric Chemistry Mechanism, version 2 (RACM2) Chemical Aqueous-Phase Radical 3.0 (CAPRAM 3.0), we found that high (SO2 HCHO), relative humidity, moderately acidic pH conditions enhanced heterogeneous formation hydroxymethanesulfonate (HMS) PM2.5. Furthermore, by employing OBM Master Mechanism (OBM-MCM), verified disabling HCHO mechanism could decrease daytime net production rates reducing HO2 + NO. These consistent daily values AOC, OH, HO2, RO2 concentrations. This contributes better understanding significance photochemical reactions HMS