Abstract
Source apportionments of domestic/overseas impacts on non-seasalt sulfate aerosol (nss-SO42-) concentration in Japan were analyzed on the basis of tagged tracer method in regional chemical transport model. The emission source groups were categorized into anthropogenic sources from China, Korea, and Japan, and natural sources from volcanic activity. To investigate the seasonal dependency of source apportionments, the representative months of January, April, July, and October on the year of 2005 were chosen in this analysis. A distinguishable feature of this study is that source apportionments of sulfur dioxide (SO2), which is a precursor of nss-SO42-, were also investigated. Modeling system with 36 km horizontal resolution well captured the seasonal variability of both SO2 and nss-SO42-. In Japan, domestic impacts on SO2 concentration was leading contributor (66.3% on average), however, transboundary air pollution with the contribution from China was dominant throughout seasons for nss-SO42- (50.6% on average). This is because the SO2 concentration in China was one order of magnitude greater than that in Japan, therefore, nss-SO42- was chemically produced during long-range transport. During summer, SO2 emitted from China was fully (> 95%) converted into nss-SO42- and affected Japan. Impact from volcanic activity was also identified as the major contributor of nss-SO42- concentration in Japan; they surpassed the anthropogenic Japanese domestic impacts during spring and autumn.
