RUI: The Production and Degradation of Acetone in Seawater

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Hydroxyl radicals are the most important oxidants in the atmosphere, playing a critical role in atmospheric chemistry. Oxygenated hydrocarbons like acetone are a major source of hydroxyl radicals in the drier upper troposphere. The role of the oceans in cycling acetone into or out of the troposphere is believed to be important but is currently not well established. A better understanding of the production and destruction processes that control acetone concentrations in the sea would ultimately allow scientists to estimate the global air-sea flux of acetone and its impact on tropospheric chemistry. In this project, researchers at Chapman University will study the sea-air flux of acetone by addressing four short-term goals: (1) determining acetone at nanomolar levels in seawater with a method compatible with undergraduate student research capabilities; (2) determining acetone concentrations in surface seawater at coastal sites in Southern California over several diurnal periods in the dry and wet rainy season; (3) estimating the biological and photochemical production rates of acetone in seawater; and (4) estimating the photochemical and biological degradation rates for acetone in seawater. The long term goals are to improve the overall understanding of the processing of acetone in surface seawaters and ultimately the flux of acetone across the air-sea interface. The proposed research builds on the PIs? extensive previous experience in the analysis of trace gases produced in the surface ocean and the photochemistry of CDOM in coastal waters and will use existing analytical facilities in the PIs? laboratories at Chapman. This proposal will have significant broader impacts on the integrated research and educational experience of undergraduate students at Chapman University. Chapman is a small private liberal arts-based university located in a culturally diverse community in Southern California. In addition to providing significant research opportunities to undergraduate students, findings and methods from this study will be incorporated into the curriculum and laboratories of undergraduate courses taught by the PIs in Advanced Topics in Environmental Chemistry: Atmospheric Chemistry, Instrumental Analysis and Physical Chemistry, taken by 10-20 chemistry majors per year.