CONTRIBUTION OF VARIOUS SULFUR SOURCES TO ATMOSPHERIC SULFATE DEPOSITION IN NIIGATA PREFECTURE, JAPAN

Atmospheric sulfate deposition varies markedly with season along the c oast of Sea of Japan where the northwesterly wind dominates in winter. The sulfur isotopic ratios (deltaS-34) of the sulfate have been measu red over 7 years in Niigata Prefecture, Japan, in order to investigate the sources of sulfur in the deposits. Remarkable seasonal variation of deltaS-34 of the sulfate (0-12parts per thousand) indicates that co ntribution of seasalt sulfate is very high in winter and that relative contribution of different sulfate sources to non-seasalt-sulfate in t he deposits varies with season. Sulfate produced by coal combustion in China has high contribution (20%) in winter, whereas other sulfur sou rces such as volcanic gases, local anthropogenic sources and biologica l production become significant in other seasons.