Anthropogenic radionuclides in sediment in the Japan Sea; Distribution and transport processes of particulate radionuclides

Otosaka, Shigeyoshi ; Amano, Hikaru; Ito, Toshimichi ; Kawamura, Hideyuki ; Kobayashi, Takuya ; Suzuki, Takashi ; Togawa, Orihiko ; Chaykovskaya, E. L.*; Lishavskaya, T. S.*; Novichkov, V. P.*; Karasev, E. V.*; Tkalin, A. V.*; Volkov, Y. N.*

Distributions of radionuclides (Sr, Cs and Pu) in seabed sediment in the Japan Sea were observed during 1998-2002. Observed inventories of anthropogenic radionuclides in sediment ranged 0.1-86 Bq m for Sr, 23-379 Bq m for Cs and 0.1-86 Bq m for Pu. In the deep part ( 2 km depth) of the western Japan Basin, Pu/Cs inventory ratios were larger than those in the central Yamato Basin although inventories of radionuclides were not different between basins. The higher Pu/Cs ratios in the western Japan Basin were derived by the production of Pu-enriched particle in the surface layer and effective sinking of particulate materials in this region. In the marginal Yamato Basin and the Ulleung Basin, both inventories and Pu/Cs ratios in sediment were larger than those in the central Yamato Basin. In the eastern/southern Japan Sea, it was suggested that the supply of particulate radionuclides by the TWC enhanced accumulation of radionuclides in this region.