A wide variety of hydrocarbons are emitted into the atmosphere from both natural and anthropogenic sources. Isoprene (2-methyl- 1,3-butadiene) is of particular interest because it has the largest global flux of any single hydrocarbon species with the possible exception of methane, Isoprene reacts rapidly with hydroxyl radical (OH) and ozone (O3) in the presence of NOx forming 3-buten-2 one( methyl vinyl ketone, MVK) and 2-methyl-2-propenal (methacrolein, MACR). Once formed, tropospheric MVK and MACR, as well as many other hydrocarbon oxidation products, may undergo a variety of reactions in the gas phase. It is likely that MVK, MACR and other hydrocarbon oxidation products can also partition into atmospheric water drops and undergo subsequent aqueous-phase reactions leading to the formation of peroxyl radicals (HO2/RO2) and other oxidant species, and there by, consuming MVK and MACR. Peroxyl radicals can destroy tropospheric O3 and form peroxides that rapidly oxidize sulfur dioxide (SO2) in the aqueous phase. The sulfate aerosol that is subsequently formed efficiently backscatters incoming solar radiation and exerts a significant cooling effect upon climate. These researchers therefore will study: 1) partitioning of MVK, MACR and other hydrocarbon oxidation products from the gas phase into water, 2) aqueous-phase photochemistry of MVK, MACR, and other hydrocarbon oxidation products under conditions that are typical of atmospheric water drops, and 3) aqueous-phase reactions of MVK, MACR and other hydrocarbon oxidation products with selected photochemical oxidants.
