The Influence of Halogen-Containing Oxidants in Sulfate Aerosol Formation in the Marine Boundary Layer

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This research will test the hypothesis that halogen-containing oxidants (such as HOBr) play a significant role in sulfate aerosol formation in the marine boundary layer. Because HOBr and HOCl transfer unique isotopic signatures of oxygen to their oxidation products, the oxygen isotopic composition of the measured sulfate reflects the relative importance of the different mechanisms of oxidation. Measurements of Delta(17)Oxygen in sulfate, a value dependent only on the oxidation pathway of SO2 to sulfate, will be made on aerosol filter samples previously collected from nearly every major ocean basin. The global chemical transport model GEOS-Chem will be run for the days that the filter samples were collected. The modeled data for Delta(17)Oxygen will be compared with observations to provide constraints on the relative importance of hypohalous acid (HOX) in sulfate formation at each location.The results of this effort are important for understanding sulfate formation in the remote marine boundary layer. Sulfate is a major component of atmospheric aerosol and is especially important in the formation of new aerosol. This research is highly relevant for gaining a better understanding of cloud-aerosol chemistry and climate change.