Contribution of Asian dust to atmospheric deposition of radioactive cesium (137Cs)

Both Asian dust (kosa) transported from the East Asian continent and locally suspended dust near monitoring sites contribute to the observed atmospheric deposition of Cs-137 in Japan. To estimate the relative contribution of these dust phenomena to the total Cs-137 deposition, we monitored weekly deposition of mineral particles and Cs-137 in spring. Deposition of Cs-137 from a single Asian dust event was 62.3 mBq m(-2) and accounted for 67% of the total Cs-137 deposition during the entire monitoring period. Furthermore, we found high Cs-137 specific activity in the Asian dust deposition sample. Although local dust events contributed to 137Cs deposition, their contribution was considerably smaller than that of Asian dust. We conclude that the primary source of atmospheric Cs-137 in Japan is dust transported from the East Asian continent. (C) 2008 Elsevier B.V. All rights reserved.