Relative Humidity Changes the Role of SO 2 in Biogenic Secondary Organic Aerosol Formation

作者：Li Xu, Narcisse T. Tsona, Lin Du · 发表于：The Journal of Physical Chemistry Letters · 年份：2021 · DOI：10.1021/acs.jpclett.1c01550 · 被引用次数：32 · 研究领域：Atmospheric chemistry and aerosols、Air Quality and Health Impacts、Air Quality Monitoring and Forecasting

SO 2 influences secondary organic aerosol (SOA) and organosulfates (OSs) formation but mechanisms remain elusive. This study focuses on this topic by investigating biogenic γ-terpinene ozonolysis under various SO 2 and relative humidity (RH) conditions. With a constant SO 2 concentration (∼110 ppb), the increase in RH transformed SO 2 sinks from stabilized Criegee intermediates (sCIs) to peroxides in aerosol particles. The associated changes in particle acidity and liquid water content may collectively first lead to decreased and then increased SOA yield with increasing RH, with the turning point appearing at ∼30% RH. The abundance of most OSs formed under 45% RH was more than 5 times higher than that of OSs formed under 10% RH, possibly due to interactions of dissolved SO 2 with hydroperoxides (ROOH) in SOA. ROOHs formed from the autoxidation processes of alkylperoxy radicals were proposed to be precursors for highly oxidized OSs (HOOSs) that decreased SOA volatility and showed a certain abundance in ambient aerosols. This study highlights that high RH potentially enhances the contribution of SO 2 to OSs formation, and particularly, HOOSs formation during monoterpene ozonolysis in the atmosphere.