Spatial distributions of volatile sulfur compounds in surface seawater and overlying atmosphere in the northwestern Pacific Ocean, eastern Indian Ocean, and Southern Ocean

摘要

+AFs- 1+AF0- Distributions of volatile sulfur compounds ( carbonyl sulfide ( COS), carbon disulfide (CS2), hydrogen sulfide (H2S), dimethyl sulfide (DMS)) in surface seawater and overlying atmosphere were measured in the northwestern Pacific, eastern Indian, and Southern Oceans (40 degrees N - 66 degrees S, 40 degrees E - 140 degrees E) in November - December 1996 during the 38th Japanese Antarctic Research Expedition cruise. Seawater measurements revealed that DMS was the dominant sulfur compound, with concentrations of 0.5 - 15.8 nM. High values were found in the Southern Ocean's marginal ice zone (84 degrees E - 63 degrees E, 59 degrees S - 63 degrees S), suggesting that the area during the bloom acts as an important source of atmospheric DMS. Atmospheric concentrations were 456 - 471 pptv for OCS, n. d. ( not detected level) - 13 pptv for CS2, n. d. - 17 pptv for H2S, and n. d. - 755 pptv for DMS. Concentrations of OCS were nearly constant. Concentrations of CS2 and H2S were high in terrigenic air masses and low in those of oceanic origin. Comparison of atmospheric DMS data and a steady state box model using sea-to-air fluxes of DMS and assumed OH radical concentrations revealed that atmospheric DMS concentrations in the equatorial region and most of the Southern Ocean were balanced with local oceanic emission residues and photochemical oxidation. Simultaneous measurements in the atmosphere showed DMS was the dominant sulfur gas that was oxidized rapidly to sulfate aerosols in the marine atmosphere.