9412237 Wine This four year program will involve continuing research aimed at elucidating the kinetics and reaction mechanisms which control the atmospheric oxidation of sulfur compounds, with particular emphasis oxidation pathways for dimethylsulfide (CH3 SCH3, DMS). The goals of the program is the definitive determination of the rates and mechanisms for conversion of reduced sulfur compounds to relatively stable S(IV and S(VI) and products such as sulfur dioxide (SO2), sulfuric acid (H2S04), sulfoxides, sulfones and sulfonic acids. Direct, "real time" observations of reactive intermediates and stable end products is emphasized because only through such observations can results with a unique interpretation be obtained. The research will contribute significantly to our understanding of the global sulfur cycle, thus facilitating accurate assessment of the contribution of both biogenic and anthropogenic sulfur to such problems as climate modification (or regulation), visibility reduction, and acid precipitation. Specific experimental investigations will focus on DMS, DMS adducts, DMSO (CH3SOCH3), carbonyl sulfide (OCS), and S03 H2) adducts. The experimental methodology will involve coupling radical generation by laser flash photolysis with a number of time-resolved detection techniques including pulsed laser induced fluorescence, atomic resonance fluorescence, UV-visible absorption using both incoherent and laser light sources, infrared tunable diode laser absorption, photoionization mass spectrometry, and resonance enhanced multiphoton ionization mass spectrometry. In these mechanistic studies, th ability to obtain time-resolved data on 10- 7-10-3 s time scales is critical to defining the detailed reaction sequences leading to product formation. The investigators will, of course, keep abreast of progress in other laboratories and new developments in the area of tropospheric chemistry, and may alter their sub-tasks somewhat to accomm odate newly identified research needs. ***
