Laboratory Studies of Tropospheric Sulfur Chemistry

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This research project is a laboratory study aimed at elucidating the kinetics and reaction mechanisms which control the atmospheric oxidation of sulfur compounds. The emphasis of this project is on oxidation pathways for dimethylsulfide (DMS, CH3SCH3), and its intermediate oxidation products dimethylsulfoxide (DMSO, CH3S(O)CH3) and methanesulfinic acid (MSIA, CH3S(O)OH). There is currently considerable interest in atmospheric sulfur oxidation in order to facilitate our understanding of (1) past climate as interpreted from ice core analyses and (2) the role sulfur plays in particle formation and growth in the atmosphere and its resulting impact on current and future climate. Specific experimental investigations which will be undertaken include (1) studies of the kinetics and mechanisms of the reactions of BrO radicals with DMS and DMSO, as well as the reactions of Cl, Br, and O atoms with DMSO; (2) a study of the CH3SCH2OO + HO2 radical-radical reaction; (3) studies of the aqueous phase reactions of OH, SO4-, NO3, and Cl2- radicals with DMSO, MSIA, MSA, and dimethylsulfone (DMSO2, CH3(O)S(O)CH3); (4) studies of the reaction kinetics of MSIA(g); and (5) development of optical and/or mass spectrometric techniques for detection of CH3SOx (x = 1-3) radicals. A new, high pressure turbulent flow reactor will be constructed and utilized during the course of this research. The flow reactor will be coupled with CIMS (chemical ionization mass spectrometry, PIMS (photoionization mass spectrometry), and TDLAS (tunable diode laser absorption spectroscopy) detectors.