The role of multiphase chemistry in the oxidation of dimethylsulphide (DMS). A latitude dependent analysis

A kinetic model for the OH-initiated homogeneous gas phase oxidation of dimethylsulfide (DMS) in the atmosphere (Saltelli and Hjorth, 1995), has been extended here to include the liquid phase chemistry. The updated model has then been employed to predict the temperature dependency of the MSA/nss-SO42- ratio. Model predictions have been compared with observational data reported in Bates et al. (1992). Sensitivity and uncertainty analysis has been performed in a Monte Carlo fashion to identify which are the important uncertainties on the input parameters and which are the possible combinations of parameter values that could explain the field observations. Results of the analysis have indicated that the temperature dependencies of the interactions between gas phase and liquid phase chemistry may to a large extent explain the observed T-dependence of the MSA/nss-SO42- ratio. The potential role of multi-phase atmospheric chemistry, not only in the case of SO2 but also of other oxidation products of DMS and, particularly, of DMS itself, has been highlighted.