title: Five-minute resolved spatial distribution of radiocesium in sea sediment derived from the Fukushima Dai-ichi Nuclear Power Plant.
abstract: The spatial distributions of radiocesium concentration in sea sediment to a core depth of 14 cm were investigated in the offshore region from the Fukushima Prefecture to the northern part of the Ibaraki Prefecture in February and July 2012, at a spatial resolution of 5 min of latitude and longitude. The concentrations in the area south of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) were generally higher than those in the area north of it. In the southern area, a band of especially high concentration with a width about 20 km was present in the region shallower than 100 m, and a narrow minimal concentration band was found along the 200-m isobaths. In more than half of all cases, the vertical core profiles of radiocesium concentration generally showed an exponential decreasing trend with depth. However, in the area north of the FDNPP, where the radiocesium concentrations tended to be very low, radiocesium concentrations that had similar or larger magnitude compared with those of the most-surface layer were often found in deeper layers. Relatively good correlations were found between radiocesium concentrations and grain sizes of the most-surface sediment. The vertical profile of radiocesium concentration also had a relationship with grain size. In other case, the radiocesium concentration in the sediment seems to have had a dependence on the radiocesium concentration in bottom seawater, suggesting that the quantity of radiocesium supplied and the grain size were major factors determining the spatial distribution pattern of the radiocesium concentration after the FDNPP accident.
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan. Electronic address: ambe@affrc.go.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ambe
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kaeriyama
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Shigenobu
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Fujimoto
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Ono
authors.affiliation: National Research Institute of Fisheries Engineering, Fisheries Research Agency, 7620-7, Hasaki, Kamisu, Ibaraki 314-0408, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sawada
authors.affiliation: National Research Institute of Fisheries Engineering, Fisheries Research Agency, 7620-7, Hasaki, Kamisu, Ibaraki 314-0408, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Saito
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Shizuho
authors.initials: S
authors.lastname: Miki
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Setou
authors.affiliation: Fisheries Agency, 1-2-1, Kasumigaseki, Chiyoda-ward, Tokyo 100-8907, Japan.
authors.forename: Takami
authors.initials: T
authors.lastname: Morita
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa-ward, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Tomowo
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D002586:Cesium / Q000032:analysis*; D002588:Cesium Radioisotopes / Q000032:analysis; D062406:Fukushima Nuclear Accident; D019015:Geologic Sediments / Q000032:analysis*; D007564:Japan; D010140:Pacific Ocean; D011834:Radiation Monitoring; D062206:Spatial Analysis; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive; D002586:Cesium
keywords: Bottom seawater; Cs-134 and Cs-137; Grain size; Nuclear accident; Organic matter; Sea sediment