An intensive observation campaign at Cape Hedo, Okinawa, Japan was conducted from late October to early November 2015 to investigate the behavior of long-range transported atmospheric pollutants. During this period, sulfate (SO4 2–) was the dominant aerosol component. The sources of SO4 2– were estimated by using the air quality model with the tagged tracer method. The main source of high SO4 2– concentration varied day-to-day. When the westerly wind was dominant (October 27), the main source was anthropogenic SO2 emissions in China. When the northerly wind prevailed (November 1), the impact of volcanoes in western Japan was significant and the conversion ratio from SO2 to SO4 2– was lowest, at less than 70%, because of the faster transport. During the latter part of the campaign, the northerly to easterly winds were prominent, and the impacts of Korea, Japan, and ships on SO4 2– observed at Cape Hedo were also clear. When the contributions from Korea, Japan, and ships were the highest (November 4), the conversion ratio was also the highest, at greater than 95% because of long-range transport. The modeled sources of volcanoes and ship emissions corresponded well with the observed coarse-mode SO4 2– and V/Mn ratio, respectively. The mutual evaluation of sources from model and observations enable SO4 2– sources to be estimated with higher confidence.
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