title: Southwest intrusion of 134Cs and 137Cs derived from the Fukushima Dai-ichi nuclear power plant accident in the Western North Pacific.
abstract: Enormous quantities of radionuclides were released into the ocean via both atmospheric deposition and direct release as a result of the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. This study discusses the southward dispersion of FNPP-derived radioactive cesium (Cs) in subsurface waters. The southernmost point where we found the FNPP-derived (134)Cs (1.5-6.8 Bq m(-3)) was 18 °N, 135 °E, in September 2012. The potential density at the subsurface peaks of (134)Cs (100-500 m) and the increased water column inventories of (137)Cs between 0 and 500 m after the winter of 2011-2012 suggested that the main water mass containing FNPP-derived radioactive Cs was the North Pacific Subtropical Mode Water (NPSTMW), formed as a result of winter convection. We estimated the amount of (134)Cs in core waters of the western part of the NPSTMW to be 0.99 PBq (decay-corrected on 11 March 2011). This accounts for 9.0% of the (134)Cs released from the FNPP, with our estimation revealing that a considerable amount of FNPP-derived radioactive Cs has been transported to the subtropical region by the formation and circulation of the mode water.
authors.affiliation: Research Center for Fisheries Oceanography and Marine Ecosystem, 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.forename: Yugo
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ambe
authors.forename: Masachika
authors.initials: M
authors.lastname: Masujima
authors.forename: Yuya
authors.initials: Y
authors.lastname: Shigenobu
authors.forename: Ken
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Ono
authors.forename: Kou
authors.initials: K
authors.lastname: Nishiuchi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Taneda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kurogi
authors.forename: Takashi
authors.initials: T
authors.lastname: Setou
authors.forename: Hiroya
authors.initials: H
authors.lastname: Sugisaki
authors.forename: Tadafumi
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Hidaka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hiroe
authors.forename: Akira
authors.initials: A
authors.lastname: Kusaka
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Kodama
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kuriyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Morita
authors.forename: Kaoru
authors.initials: K
authors.lastname: Nakata
authors.forename: Kenji
authors.initials: K
authors.lastname: Morinaga
authors.forename: Takami
authors.initials: T
authors.lastname: Morita
authors.forename: Tomowo
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D007564:Japan; D055848:Nuclear Power Plants; D010140:Pacific Ocean; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive