干旱区生态环境知识资源中心

Plutonium was determined in monthly atmospheric deposition samples from 2000 to the end of 2003 collected at Tsukuba, Japan, together with monthly thorium deposition. Monthly (239,240)Pu and thorium depositions showed a typical seasonal variation with a maximum in spring. The (230)Th/(232)Th activity ratios in the deposition samples differed from that of surface soils near Tsukuba. These results reveal that a significant part of the (239,240)Pu deposition observed in Japan is attributable to resuspension of deposited plutonium originating from the East Asian continent deserts and arid areas.