Relative contributions of selected multigeneration products to chamber SOA formed from photooxidation of a range (C10–C17) of n-alkanes under high NOx conditions

Abstract

A series of chamber experiments was conducted to investigate the composition of secondary organic aerosol (SOA) following oxidation of a range of parent n-alkanes (C10–C17) in the presence of NOx. The relative contribution of selected species representing first, second, and higher generation products to SOA mass was measured using a high-resolution aerosol mass spectrometer. Gas chromatography was also used for a limited set of amenable species. Relative contributions varied substantially across the range of investigated alkanes reflecting slight changes in SOA composition. The contribution of first-generation cyclic hemiacetal is minimal toward the small end of the investigated range and gradually increases with n-alkane size. The relative contributions of second generation and higher nitrate-containing species, in contrast, decrease with an increased alkane size. A similar trend is observed for relative contribution of organonitrates to SOA. Finally, SOA yield and composition are sensitive to water vapor concentrations. This sensitivity is limited to a narrow range (dry to ~15% RH) with little, if any, impact above 15% suggesting that this impact may be negligible under ambient conditions. The impact of water vapor also appears to decrease with increasing alkane carbon number.