DISTRIBUTION AND INVENTORY OF FALLOUT PU AND CS IN THE SEDIMENT OF THE EAST SEA OF KOREA

Sediment samples were collected from the Ulleung Basin in the East Sea of Korea and analyzed for Pu-239,Pu-240, Pu-238 and Cs-137 concentrat ions and excess Pb-210. The apparent sedimentation rate was estimated to be 0.069 cm year(-1) for Station 1 sediment and 0.061 cm year(-1) f or Station 2 sediment. From depth profiles, the maximum concentrations of Pu-239,Pu-240 and Cs-137 appeared at 2-4 cm depth in sediments on the continental slope and at 2-3 cm depth in the Ulleung Basin, corres ponding to the deposits laid down in the years 1950-1975. The inventor ies of Pu-239,Pu-240 and Cs-137 were estimated to be 59.4 and 338.6 Bq m(-2) for Station 1 sediment and 65.5 and 247.4 Bq m(-2) for Station 2 sediment. The activity ratios of Pu-238/Pu-239,Pu-240 in sediments w ere found to be within the narrow range of 0.028-0.052 with a mean val ue of 0.041. No significant changes in Pu-239,Pu-240/Cs-137 ratios occ ur with depth in the East Sea sediments. The activity ratios of Pu-239 ,Pu-240/Cs-137 in the surface sediment were higher than the ratio due to global fallout. (C) 1998 Elsevier Science Ltd. All rights reserved.