title: Impact of the Fukushima accident on tritium, radiocarbon and radiocesium levels in seawater of the western North Pacific Ocean: A comparison with pre-Fukushima situation.
abstract: Tritium, radiocarbon and radiocesium concentrations in water column samples in coastal waters offshore Fukushima and in the western North Pacific Ocean collected in 2011-2012 during the Ka'imikai-o-Kanaloa (KoK) cruise are compared with other published results. The highest levels in surface seawater were observed for134Cs and137Cs in seawater samples collected offshore Fukushima (up to 1.1 Bq L-1), which represent an increase by about three orders of magnitude when compared with the pre-Fukushima concentration. Tritium levels were much lower (up to 0.15 Bq L-1), representing an increase by about a factor of 6. The impact on the radiocarbon distribution was measurable, but the observed levels were only by about 9% above the global fallout background. The137Cs (and similarly134Cs) inventory in the water column of the investigated western North Pacific region was (2.7 ± 0.4) PBq, while for3H it was only (0.3 ± 0.2) PBq. Direct releases of highly contaminated water from the damaged Fukushima NPP, as well as dry and wet depositions of these radionuclides over the western North Pacific considerably changed their distribution patterns in seawater. Presently we can distinguish Fukushima labeled waters from global fallout background thanks to short-lived134Cs. However, in the long-term perspective when134Cs will decay, new distribution patterns of3H,14C and137Cs in the Pacific Ocean should be established for future oceanographic and climate change studies in the Pacific Ocean.
authors.affiliation: Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, 84248 Bratislava, Slovakia. Electronic address: povinec@fmph.uniba.sk.
authors.forename: P P
authors.initials: PP
authors.lastname: Povinec
authors.affiliation: Environment Laboratories, International Atomic Energy Agency, MC 98000 Monaco.
authors.forename: L
authors.initials: L
authors.lastname: Liong Wee Kwong
authors.affiliation: Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, 84248 Bratislava, Slovakia.
authors.forename: J
authors.initials: J
authors.lastname: Kaizer
authors.affiliation: Institute for Nuclear Research (ATOMKI), 4026 Debrecen, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Molnár
authors.affiliation: Environment Laboratories, International Atomic Energy Agency, MC 98000 Monaco.
authors.forename: H
authors.initials: H
authors.lastname: Nies
authors.affiliation: Institute for Nuclear Research (ATOMKI), 4026 Debrecen, Hungary.
authors.forename: L
authors.initials: L
authors.lastname: Palcsu
authors.affiliation: Institute for Nuclear Research (ATOMKI), 4026 Debrecen, Hungary.
authors.forename: L
authors.initials: L
authors.lastname: Papp
authors.affiliation: Environment Laboratories, International Atomic Energy Agency, MC 98000 Monaco.
authors.forename: M K
authors.initials: MK
authors.lastname: Pham
authors.affiliation: LSCE, CEA-CNRS-UVSQ, CEA/Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Jean-Baptiste
mesh_terms: D002250:Carbon Radioisotopes / Q000032:analysis*; D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D010140:Pacific Ocean; D011834:Radiation Monitoring; D012623:Seawater / Q000737:chemistry; D014316:Tritium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002250:Carbon Radioisotopes; D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive; D014316:Tritium
keywords: Fukushima accident; GEOSECS; KoK cruise; Radionuclides in seawater; WOCE; WOMARS