Anthropogenic radionuclides in sediment in the Japan Sea

Otosaka, Shigeyoshi  ; Aramaki, Takafumi*; Suzuki, Takashi  ; Kobayashi, Takuya ; Ito, Toshimichi ; Togawa, Orihiko ; Chaykovskaya, E. L.*; Dunaev, A. L.*; Karasev, E. V.*; Novichkov, V. P.*; Tkalin, A. V.*; Volkov, Y. N.*

Seabed sediments were collected at 22 stations in the Japan Sea, and anthropogenic radionuclides were measured in order to understand distributions and accumulation processes of these materials. Averaged concentrations of Cs in sediment in the Japan Basin and the Yamato Basin were 1.0 Bq/kg and 1.0 Bq/kg, respectively. Although there was no significant difference in mean Cs concentration between the Japan Basin and the Yamato Basin, distributions of radionuclides in these 2 basins showed different features. In the Japan Basin, the spatial variation of concentration of radionuclides was smaller than that at the Yamato Basin. At most stations in the Yamato Basin, significant concentrations of radionuclides were not detected, but remarkable large activities were observed at several stations in the Yamato Basin. For all radionuclides, the highest concentration was observed in the southeastern margin of the Yamato Basin. These results would suggest that there were different accumulation processes of radionuclides between the Japan Basin and the Yamato Basin.