Atmospheric Sulfur Dioxide Over the Southern Ocean: Shipboard and Land-based Measurements During the ACE-1 Experiment

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9420157 Saltzman This project is part of the Southern Hemisphere Marine Aerosol Characterization Experiment (ACE-1), which will be conducted in the remote Southern Pacific in 1995 using aircraft, ship-board, and ground-based measurements of a wide variety of chemical species, physical and meteorological parameters with the central goal of investigating the formation, evolution, and optical properties of atmospheric aerosol. In this component, atmospheric sulfur dioxide will be measured aboard the research vessel Discoverer and at Cape Grim, Tasmania. The instruments to be used are HPLC-fluorescent devices which are capable of detecting 10 ppt sulfur dioxide with a measurement period of less than 10 minutes. In addition to sulfur dioxide, filter-based fluorescence decay measurements of hydrogen sulfide in air will be made on board the ship. Hydrogen sulfide is a precursor to sulfur dioxide and no data are currently available from this region of the oceans. The goal of this project is to construct a budget for sulfur dioxide in the marine boundary layer over the Southern Ocean, south of Tasmania. Specifically, the following quantities will be estimated: 1) the yield of sulfur dioxide from the oxidation of dimethyl sulfide, 2) the photochemical loss rate to gas phase sulfuric acid, and 3) the relative importance of losses to clouds, sea-salt aerosols and to the sea surface. The interpretation of the field data will be done using a photochemical box model of the marine boundary layer coupled to a detailed model of heterogeneous chemistry. Ultimately, this work will contribute to the development of mechanistic models for the production and growth of sulfuric acid aerosols in marine air. Such models are clearly needed in order to develop a predictive capability for the interrelation between global change and the aerosol/cloud component of the earth s radiative budget.