Aqueous reaction kinetics of ozone and dimethylsulfide and its atmospheric implications

Abstract

In order to understand and predict the budgets and distributions of ozone (03) and dimethylsulfide (DMS) in the marine atmosphere, it is necessary to determine the rates of aqueous reactions in clouds and surface water that may influence the lifetimes of these species. We studied the kinetics of the aqueous phase reaction of 03 and DMS in the laboratory using a bubbler-type gas-liquid reactor at sub-parts-perbillion (ppb) gas phase concentrations. The steady state reaction rate was determined from the decrease of gas phase DMS concentration in the effluent gas as ozone was simultaneously added. The reaction stoichiometry was found to be 1' 1 with respect to the two reagents. Fitting the data to a kinetics scheme appropriate for a gas-liquid reaction in the slow reaction regime where the reaction rate is governed by both chemical reaction and convective mass transfer, we determined an intrinsic secondorder aqueous rate coefficient of O3-DMS reaction of 4 x 108 (___40%) M -1 s -1 at 15.0øC. The implications of this reaction include (1) the atmosl•heric lifetime of DMS against in-cloud O3-DMS reaction at 30 ppb of 03 and 1 g m -• liquid waterconcentration is calculated to be --•3 days and is comparable to that against the gas phase reaction with OH radicals at 1 x 10 6 molecules cm-3; (2) the deposition of atmospheric 03 to the ocean surface is only slightly enhanced by the O3-DMS reaction at the highest reported surface DMS concentrations, (--•40 nM); and (3) the sea to air flux of DMS is not affected by this reaction at 03 concentrations typical of the marine atmosphere. a considerable amount of effort has been devoted to eluci-oxidants such as OH [Atkinson et al., 1989], NO 3 [Wayne et al., 1991], and 03 [Martinez and Herron, 1978]. Although a detailed analysis of gaseous oxidation of DMS has been presented for varied atmospheric conditions [Y in et al., 1990a], important gaps remain in our understanding of the role DMS plays in CCN formation. For example, despite the prediction that SO2 is the dominant product over methanesulfonic acid in the OH-radical-induced DMS oxidation under low NOx concentrations pertinent to a remote marine atmosphere [Y in et al., 1990b], methanesulfonic acid has been found to correlate with CCN [Ayers and Gras, 1991] and nonseasalt sulfate [Prospero et al., 1991], whereas SO2 was found to exhibit little correlation with DMS [Bandy et al., 1992]. Consequently, it has been suggested that DMS can be converted to condensation nuclei without involving SO2 as an intermediate [Lin and Chameides, 1993]. With respect to aqueous phase oxidation, the reaction of DMS and OH radicals was found to be rapid [Bonioeacic et al ., 1975]; on the other hand, reaction with H202 was found to be slow [Adewuyi, 1989]. However, the aqueous oxidation of DMS by ozone has not been examined before, perhaps because its kinetics is too fast to be conveniently studied.Since 03 is present at a substantial concentration in the atmosphere, including remote marine boundary layer air, and its aqueous phase reaction with a...

Gaseous (DMS, MSA, SO<sub>2</sub>, H<sub>2</sub>SO<sub>4</sub> and DMSO) and particulate (sulfate and methanesulfonate) sulfur species over the northeastern coast of Crete

“…In the case of XO-initiated atmospheric DMS oxidation (X = Br, Cl), DMSO yield is expected to be around 100% (Barnes et al, 1991;Ingham et al, 1999). DMSO is also produced via multiphase reactions of DMS with O 3 (Lee and Zhu, 1994). To our knowledge the present gaseous DMSO measurements are the first to have been conducted in the Mediterranean area.…”

Theoretical study of adducts of dimethyl sulfide with hydroperoxyl and hydroxyl radicals

“…It has also been shown that DMS is oxidized by chlorine atom, and that this is probably important in the atmosphere [9][10][11]. DMS oxidation by halogen oxides in the gas phase [12][13][14][15], and via heterogeneous reactions [16], for example, with aqueous phase ozone (O 3 ) [17,18], may also be important. Some model calculations over predict the concentration of DMS in the marine boundary layer (MBL), suggesting that there may be a missing sink [19].…”

DMS atmospheric concentrations and sulphate aerosol indirect radiative forcing: a sensitivity study to the DMS source representation and oxidation

“…The aqueous-phase reaction of DMS and O 3 expected to occur in cloud droplets, has been indicated to be of atmospheric importance (Lee and Zhou, 1994;Gershenzon et al, 2001). This reaction, as well as that in the gas phase, is usually not considered in global models of the sulphur cycle.…”