Concentrations of Sulfur Compounds (MSA, SO₂ and nss-SO₄^2-) in the Marine Atmosphere and Estimation of Biogenic Sulfur Emission from the Sea

Sulfur compounds (methane sulfonic acid (MSA), SO₂ and non sea salt sulfate (nss-S0₄²~)) in the marine atmosphere were investigated at the cource of the Antarctic Exploration ship “Shirase” over the North Pacific Ocean, the Indian Ocean and the Anlarctic Ocean at Oahu Island over the North Pacific Ocean and at Bermuda Island over the North Atlantic Ocean. In any marine atmosphere, an existence of MSA was confirmed. Therefore, it was found that dimethyl sulfide (DMS) as a precursor of MSA was emitted globally from sea water to atmosphere. Moreover, a high concentration of MSA in Bermuda was observed during early summer when marine phytoplankton propagated. It suggestes that MSA is biogenic product. From this work, the mean concentrations in the unpolluted open sea atmosphere were 0. 03 μ;g/m³ for MSA, 0. 4 μ;g/rn³ for nss-SO₄^2- (non seasalt sulfate), O.O5 ppb for SO_2. On the base of these measured concentrations, the global emission of biogenic sulfur compounds from sea water to atmosphere is estimated to be about 50 TgS/y. This value is comparable to 40% of the sulfur emission (126 x 10¹² gS/y) from anthropogenic sources.