9634129 Keene Chemical processes involving sea-salt aerosol in the marine boundary layer (MBL) may significantly impact tropospheric oxidation processes; sulfur cycling, radiation balance and climate; and trace-metal fertilization of the surface ocean. Solution pH controls many chemical processes involving atmospheric sea salt. However, acid-base relationships in sea-salt aerosol are very poorly characterized; estimates of aerosol pH based on measurements and models range from <1 to >9. Reliable measurements would provide critical constraints in resolving the chemical cycling of halogens, sulfur, nitrogen, and trace metals in the MBL. The specific research objectives of this study are: (1) to sample size-segregated marine aerosol during discrete day and night periods and to measure major ionic constituents; (2) to estimate sea-salt aerosol pH as a function of particle size via direct measurements in the field using micro-electrodes, measurement of total carbonate in extracts, and ion-balance analyses; and (3) to assess related implications for aqueous- phase and multi-phase chemical processes in marine air. MBL air will be sampled during late April and May 1997 at the AEROCE station on Bermuda. Aerosols will be collected with high-volume cascade impactors over discrete, 12-hour, day or night periods. The concentrations of ozone, carbon monoxide, black carbon, and radon, the ionic composition of bulk aerosols, the physical and optical properties of aerosols, as well as site meteorological parameters will be measured concurrently during all or some intervals, and routine air parcel trajectory calculations will be available. ***
