Spring–summer Emission of Dimethyl Sulphide from the North-western Mediterranean Sea

Sea-to-air emission fluxes of dimethyl sulphide (DMS) from the NW Mediterranean Sea were estimated from aqueous concentrations, seawater temperatures and wind speeds measured during three cruises in spring and summer of 1993 and 1994. Fluxes averaged 11•2 and 2•5 μmol m−2day−1for shelf and open-sea stations, respectively. Annual extrapolation of these spring–summer fluxes resulted in a DMS emission of 8•8×103 t(S) year−1for the whole NW Mediterranean basin. This is the first estimate of the outflux of biogenic sulphur in the region based on experimental data. It is concluded that the NW Mediterranean is a source of biogenic sulphur to the atmosphere, but DMS fluxes are moderate overall and closer to fluxes from temperate open oceanic regions than to those from other marginal seas. The marine emission represents only 0•3% of the surrounding continental anthropogenic sulphur emissions.