Results from field studies have shown that atmospheric organic aerosol (OA) is subject to oxidative “aging” processes that lead to increases in particle loading and carbon oxidation state. However the chemical mechanisms that underlie such processes are not well-understood. Here we describe a series of laboratory experiments aimed at better understanding the chemistry of OA aging, with a particular focus on the phase in which aging occurs. Secondary organic aerosol (SOA) was formed and aged in a series of chamber experiments, under conditions in which further oxidation by the hydroxyl radical (OH) could occur either in the gas phase or in the aqueous (deliquesced-particle) phase. The evolving partitioning and oxidation state of the organic carbon was investigated as a function of this phase, as well as of relative humidity and precursor hydrocarbon structure. These measurements enable estimates of aging timescales as a function of reaction conditions, and therefore provide insight into viable mechanisms for the oxidative aging of atmospheric OA.

Gas-phase vs. aqueous-phase aging of secondary organic aerosol

249th National Meeting (2015)

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