Biogenic emission of dimethylsulfide from a highly eutrophicated coastal region, Masan Bay, South Korea

Atmospheric dimethylsulfide (DMS), water-soluble ionic species in aerosol such as non-seasalt sulfate and methanesulfonic acid (MSA), and seawater DMS were measured in highly eutrophicated Masan Bay, Korea in July-August 1997. Mean (median) concentrations of atmospheric DMS, seawater DMS, non-seasalt sulfate, and MSA during the experiment were 188pptv (49pptv), 6.3nM (5.3nM), 3.0μgm^-3 (2.3μgm^-3), and 0.010μgm^-3 (0.008μgm^-3), respectively. The vertical profiles of seawater, especially in inner bay, reveal that DMS concentrations were enhanced near the bottom coincidently with extremely low levels of chlorophyll-a and depleted oxygen. There were several episodes of high DMS mixing ratios up to a few ppbv, which was associated with strong wind and elevated DMS but very low chlorophyll-a and relatively low dissolved oxygen contents in the surface water. It indicates that DMS accumulated in anoxic bottom water was often transferred to the overlying water column, consequently leading to elevated DMS in the atmosphere. The mean (median) molar ratio of MSA to non-seasalt sulfate was 0.41% (0.30%), which implies the major contribution of anthropogenic SO ₂ to sulfur budget in the study area. The median flux of DMS from sea to air was estimated to 3.2μmm^-2d^-1.