title: Factors controlling the spatiotemporal variation of (137)Cs in seabed sediment off the Fukushima coast: implications from numerical simulations.
abstract: We used numerical simulations to investigate major controls on spatiotemporal variations of (137)Cs activities in seabed sediments off the Fukushima coast during the first year after the Fukushima Daiichi Nuclear Power Plant accident. The numerical model we used includes (137)Cs transfer between bottom water and sediment by adsorption and desorption, and radioactive decay. The model successfully reproduced major features of the observed spatiotemporal variations of (137)Cs activities in sediments. The spatial pattern of (137)Cs in sediments, which mainly reflected the history of (137)Cs activities in bottom water overlying the sediments and the sediment particle size distribution, became established during the first several months after the accident. The simulated temporal persistence of the (137)Cs activity in the sediments was due to adsorption of (137)Cs onto the sediment mineral fraction having a long desorption timescale of (137)Cs. The simulated total (137)Cs inventory in sediments integrated over the offshore area, where most of the monitoring stations were located, was on the order of 10(13) Bq; this value is consistent with a previous estimate based on observed data. Taking into account (137)Cs activities in sediments in both the coastal area and in the vicinity of the power plant, the simulated total inventory of (137)Cs in sediments off the Fukushima coast increased to a value on the order of 10(14) Bq.
authors: Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko, Chiba 270-1194, Japan. Electronic address: misumi@criepi.denken.or.jp.
authors: Kazuhiro
authors: K
authors: Misumi
authors: Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko, Chiba 270-1194, Japan.
authors: Daisuke
authors: D
authors: Tsumune
authors: Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko, Chiba 270-1194, Japan.
authors: Takaki
authors: T
authors: Tsubono
authors: Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko, Chiba 270-1194, Japan.
authors: Yutaka
authors: Y
authors: Tateda
authors: Institute of Environmental Radioactivity, Fukushima University, 1 Kanayagawa, Fukushima, Fukushima 960-1296, Japan.
authors: Michio
authors: M
authors: Aoyama
authors: Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai, Ibaraki 319-1195, Japan.
authors: Takuya
authors: T
authors: Kobayashi
authors: Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan.
authors: Katsumi
authors: K
authors: Hirose
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis; D062406:Fukushima Nuclear Accident; D019015:Geologic Sediments / Q000032:analysis*; D007564:Japan; D008962:Models, Theoretical; D010140:Pacific Ocean; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Cesium; Fukushima accident; Numerical model; Sediment