九州地方で採取した大気中二酸化硫黄・エアロゾルおよび総降下物中硫酸イオンの硫黄同位体比と起源推定

抄録

The δ³⁴S values of atmospheric SO₂, and of SO₄^2- in aerosols and in bulk precipitation collected over Kyushu Island were measured, and the sulfur sources were identified by comparing the δ³⁴S values with those of the sources. The δ³⁴S values of SO₂ were fairly close to those of SO₂ emitted from local sulfur sources such as petroleum combustion or fumaroles, suggesting that the contribution of the local sources to the atmosphere is relatively large. The δ³⁴S_nss values of nss-SO₄^2- in aerosols and in bulk precipitation showed seasonal variations with a maximum in winter. The high δ³⁴S_nss values observed in winter could not be explained only by an isotopic fractionation effect during the oxidation of SO₂ to SO₄^2-, suggesting that SO₄^2- with high δ³⁴S values must be present. It is considered that the desert soil SO₄^2- and SO₄^2- from coal combustion with high δ³⁴S values are transported from continental Asia to Kyushu Island by the northwest seasonal winds in winter, so that the δ³⁴S_nss values become high in winter. The results indicate that there is strong possibility of long-range transport of SO₄^2- from continental Asia to Kyushu Island.