Session: Aquatic Photochemistry:

Organosulfates (R–OSO3-, OS) are ubiquitous constituents of atmospheric particulate matter (PM) formed via a wide range of pathways, including nucleophilic reactions of sulfate anion with epoxides and addition of sulfate radical anion to unsaturated organic compounds. Recent field studies have estimated that OS can contribute up to 5–10% of fine PM; in addition, laboratory studies have shown that this class of compounds can influence the light absorption and cloud-forming properties of PM. However, there is still a dearth of studies on their atmospheric fate. Here, we report the aqueous phase hydroxyl radical (OH) oxidation kinetics of a suite of atmospherically relevant OS. In particular, we explore the effects of OS structural properties, pH and ionic strength on the observed rate constants, all of which will provide valuable input for atmospheric models. We also investigate the OH oxidation products, and thereby gain insight into the mechanisms of these transformations, and their potential impacts on aqueous aerosol composition and properties. This study presents, for the first time, the cloud water and aerosol particle reactivities of OS, and their compositional evolution, which represent a significant advance in our understanding of the atmospheric fate of OS.

Daniel Gweme

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