Volatility of Cl-Initiated C₁₂–C₁₄ n-Alkylcyclohexane Secondary Organic Aerosol: Effects of NO_x and Photoaging

Abstract

Long-chain alkanes are important components of intermediate-volatility organic compounds, especially for C12–C14 cyclic compounds. In this study, we focus on the volatilities of C12–C14 n-alkylcyclohexane secondary organic aerosol (SOA) initiated by Cl atoms and investigate the influence of NO x , aging time, precursors, and SOA mass loading. Dilution and precursors seem to have little effect on the SOA volatility. Low-volatility organic compounds (LVOCs) account for a dominant part of SOA volatility distribution. Due to the presence of NO x , more fractions of extremely low-volatility OCs (ELVOCs) and a higher carbon oxidation state ( ) result in a decrease in the SOA volatility. During the aging period, the fraction of ELVOCs increased, and semi-volatile organic compounds (SVOCs) decreased simultaneously. Even after 9 h of photoaging, the particle fractions of ELVOCs exceeded those of SVOCs to be the second largest part following LVOCs under high-NO x conditions. The particle-phase oligomerization is the dominant way that influenced the SOA volatility during the photoaging period, according to the product analysis. This study emphasizes the importance of Cl-initiated alkane SOA in the polluted region with high NO x levels.