Secondary organic aerosol formation from mixed volatile organic compounds: Effect of RO2 chemistry and precursor concentration

Abstract

Secondary organic aerosol (SOA) plays a significant role in contributing to atmospheric fine particles, as well as in global air quality and climate. However, the current understanding of the atmospheric formation of SOA and its simulation is still highly uncertain due to the complexity of its precursor VOCs. In our study, SOA formation in different mixed VOC scenarios was investigated using a 30 m3 indoor smog chamber. By comparing SOA formation in individual VOC scenarios, it was found that SOA formation from anthropogenic VOCs (AVOCs) can be positively (+ 83.9%) affected by coexisting AVOCs, while inhibited (-51.4%) by the presence of isoprene, via the OH scavenging effect. The cross-reactions of peroxyl radical (RO2) generated from different AVOCs were proved to be the main contributor (up to 39.0%) to SOA formation, highlighting the importance of RO2 + RʹO2 reactions in mixed VOC scenarios. Meanwhile, the formation of gas-phase organic intermediates of different volatility categories from the RO2 reactions was also affected by the precursor concentration, and a higher SOA yield was found at lower precursor concentrations due to the larger contribution of intermediates with lower volatility. Our study provides new insights into SOA formation by considering the interactions between intermediate products from mixed VOCs.