title: Radioactive cesium dynamics derived from hydrographic observations in the Abukuma River Estuary, Japan.
abstract: Large quantities of radioactive materials were released into the air and the ocean as a result of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, caused by the 2011 Tohoku earthquake and the subsequent major tsunami off the Pacific coast. There is much concern about radioactive contamination in both the watershed of the Abukuma River, which flows through Fukushima Prefecture, and its estuary, where it discharges into the sea in Miyagi Prefecture. We investigated radioactive cesium dynamics using mixing diagrams obtained from hydrographic observations of the Abukuma River Estuary. Particulate radioactive cesium dominates the cesium load in the river, whereas the dissolved form dominates in the sea. As the salinity increased from <0.1 to 0.1-2.3, the mixing diagram showed that dissolved radioactive cesium concentrations increased, because of desorption. Desorption from suspended particles explained 36% of dissolved radioactive cesium in estuarine water. However, the dissolved and particulate radioactive cesium concentrations in the sea decreased sharply because of dilution. It is thought that more than 80% of the discharged particulate radioactive cesium was deposited off the river mouth, where the radioactive cesium concentrations in sediment were relatively high (217-2440 Bq kg(-1)). Radioactive cesium that was discharged to the sea was transported southward by currents driven by the density distribution.
authors.affiliation: Tohoku National Fisheries Research Institute, Fisheries Research Agency, 3-27-5 Shinhama-cho, Shiogama, Miyagi 985-0001, Japan. Electronic address: kakehi@affrc.go.jp.
authors.forename: Shigeho
authors.initials: S
authors.lastname: Kakehi
authors.affiliation: National Research Institute of Fisheries Sciences, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kaeriyama
authors.affiliation: National Research Institute of Fisheries Sciences, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ambe
authors.affiliation: National Research Institute of Fisheries Sciences, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Ono
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Ito
authors.affiliation: National Research Institute of Fisheries Sciences, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Yugo
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Tohoku National Fisheries Research Institute, Fisheries Research Agency, 3-27-5 Shinhama-cho, Shiogama, Miyagi 985-0001, Japan.
authors.forename: Tomowo
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D063366:Estuaries; D062406:Fukushima Nuclear Accident; D007564:Japan; D011834:Radiation Monitoring; D045483:Rivers / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Abukuma river estuary; Deposition; Desorption; Fukushima Dai-ichi Nuclear Power Plant Accident; Mixing diagram; Radioactive cesium