title: Distribution of local 137Cs anomalies on the seafloor near the Fukushima Dai-ichi Nuclear Power Plant.
abstract: An estimated 3.5±0.7×10(15) Bq of (137)Cs is thought to have been discharged into the ocean following the melt down at Fukushima Dai-ichi Nuclear Power Plant (F1NPP). While efforts have been made to monitor seafloor radiation levels, the sampling techniques used cannot capture the continuous distribution of radionuclides. In this work, we apply in situ measurement techniques using a towed gamma ray spectrometer to map the continuous distribution of (137)Cs on the seafloor within 20 km of the F1NPP. The results reveal the existence of local (137)Cs anomalies, with levels of (137)Cs an order of magnitude higher than the surrounding seafloors. The sizes of the anomalies mapped in this work range from a few meters to a few hundreds of meters in length, and it is demonstrated that the distribution of these anomalies is strongly influenced by meter scale features of the terrain.
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. Electronic address: blair@iis.u-tokyo.ac.jp.
authors.forename: Blair
authors.initials: B
authors.lastname: Thornton
authors.forename: Seiki
authors.initials: S
authors.lastname: Ohnishi
authors.forename: Tamaki
authors.initials: T
authors.lastname: Ura
authors.forename: Naoteru
authors.initials: N
authors.lastname: Odano
authors.forename: Shun
authors.initials: S
authors.lastname: Sasaki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Fujita
authors.forename: Tomowo
authors.initials: T
authors.lastname: Watanabe
authors.forename: Kaoru
authors.initials: K
authors.lastname: Nakata
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Ono
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ambe
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D019015:Geologic Sediments / Q000737:chemistry*; D007564:Japan; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Fukushima Dai-ichi Nuclear Power Plant; Marine sediment; Radioactive cesium; Terrain features; Towed gamma ray spectrometer