239+240Pu and137Cs distributions in seawater from the Yamato Basin and the Tsushima Basin in the Japan Sea

Abstract

Seawater samples were collected from the Yamato Basin and the Tsushima Basin in the Japan Sea and analyzed for their239+240Pu and137Cs concentrations. The concentration of239+240Pu was 7.4 mBq/m3 in the surface water and increased with depth to a maximum value of 38.6 mBq/m3 at 500 m at the Yamato Basin station. The subsurface maximum may be produced by scavenging of239+240Pu in surface water and release of239+240Pu from settling particles. The239+240Pu inventories in the water column were 86.6 and 85.2 Bq/m2 at the two basin stations, suggesting that 90% of239+240Pu delivered to the Japan Sea is still present in the water column.