Sulfur isotopic view on the sources of sulfur in atmospheric fallout along the coast of the Sea of Japan

Sulfur isotopic ratios of atmospheric fallout collected from Niigata Prefecture, Japan, were measured to understand the cause(s) of the seasonal variation of sulfate fallout along the coast of the Sea of Japan. The amount of sulfate fallout increased in winter. The PʹS values ranged from + 0.9 to + 12.30/00, clearly showing a winter maximum and a summer minimum. This seasonal variation can be explained by taking into account sulfur from coal combustion in northeastern Asia, in addition to the variation in contribution of sea salt, local anthropogenic, biogenic and volcanic sulfur to the atmospheric fallout of the study area. Material balance calculations suggest that the winter fallout contains about 20% contribution of sulfur released by combustion of coals in northeastern Asia.