HR: 0800h
AN: A51B-0043    [Abstracts]
TI: The Isotope Composition of Methanesulphonic Acid for Aerosols Over the Pacific Ocean
AU: Sanusi, A
EM: sanusi@phas.ucalgary.ca
AF: The University of Calgary, Physics & Astronomy 2500 University Dr. N.W., Calgary, AB T2N 1N4 Canada
AU: * Norman, A
EM: annlisen@phas.ucalgary.ca
AF: The University of Calgary, Physics & Astronomy 2500 University Dr. N.W., Calgary, AB T2N 1N4 Canada
AU: Burridge, C
EM: ccburridge@hotmail.com
AF: Memorial University, Earth Sciences , St. John's, NF A1B 3X5 Canada
AU: Wadleigh, M A
EM: moire@esd.mun.ca
AF: Memorial University, Earth Sciences , St. John's, NF A1B 3X5 Canada
AB: Methanesulphonic acid (MSA) is the end product of the oxidation of dimethylsulphide (DMS), a gas released from the ocean surface and an indicator of phytoplankton productivity. Its ratio to non sea salt sulphate is used as a proxy for biogenic sulphate, a compound that promotes CCN formation over the open ocean and is postulated, in the CLAW hypothesis, to have a significant role in the global radiation budget. Isotope measurements of aerosol sulphate are used to define the proportion of biogenic sulphate present in aerosols near coastal regions and in the Arctic. A key assumption in the utility of isotope abundance measurements, is that there is little to no isotope fractionation on DMS oxidation. No measurements are available to test this hypothesis. In this study, the isotope composition of MSA from a shipboard aerosol measurement campaign were examined. MSA is formed solely from DMS oxidation. If isotope fractionation were important, the sulphur isotope composition of MSA would be expected to change as the proportion of DMS oxidized to MSA varied. Natural sulphur isotope abundance measurements of aerosol MSA from a shipboard campaign associated with the SOLAS ocean iron fertilization experiment SERIES cruise 2002 are described.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0322 Constituent sources and sinks
DE: 0330 Geochemical cycles (1030)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005