title: Novel insights into Fukushima nuclear accident from isotopic evidence of plutonium spread along coastal rivers.
abstract: The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident led to important releases of radionuclides into the environment, and trace levels of plutonium (Pu) were detected in northeastern Japan. However, measurements of Pu isotopic atom and activity ratios are required to differentiate between the contributions of global nuclear test fallout and FDNPP emissions. In this study, we used a double-focusing sector field ICP-MS to measure Pu atom and activity ratios in recently deposited sediment along rivers draining the most contaminated part of the inland radioactive plume. Results showed that plutonium isotopes (i.e., (239)Pu, (240)Pu, (241)Pu, and (242)Pu) were detected in all samples, although in extremely low concentrations. The (241)Pu/(239)Pu atom ratios measured in sediment deposits (0.0017-0.0884) were significantly higher than the corresponding values attributed to the global fallout (0.00113 ± 0.00008 on average for the Northern Hemisphere between 31°-71° N: Kelley, J. M.; Bond, L. A.; Beasley, T. M. Global distribution of Pu isotopes and (237)Np. Sci. Total. Env. 1999, 237/238, 483-500). The results indicated the presence of Pu from FDNPP, in slight excess compared to the Pu background from global fallout that represented up to ca. 60% of Pu in the analyzed samples. These results demonstrate that this radionuclide has been transported relatively long distances (∼45 km) from FDNPP and been deposited in rivers representing a potential source of Pu to the ocean. In future, the high (241)Pu/(239)Pu atom ratio of the Fukushima accident sourced-Pu should be measured to quantify the supply of continental-originating material from Fukushima Prefecture to the Pacific Ocean.
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), Unité Mixte de Recherche 8212 (CEA/CNRS/UVSQ) , 91198 Gif-sur-Yvette Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Evrard
authors.forename: Fabien
authors.initials: F
authors.lastname: Pointurier
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Onda
authors.forename: Caroline
authors.initials: C
authors.lastname: Chartin
authors.forename: Amélie
authors.initials: A
authors.lastname: Hubert
authors.forename: Hugo
authors.initials: H
authors.lastname: Lepage
authors.forename: Anne-Claire
authors.initials: AC
authors.lastname: Pottin
authors.forename: Irène
authors.initials: I
authors.lastname: Lefèvre
authors.forename: Philippe
authors.initials: P
authors.lastname: Bonté
authors.forename: J Patrick
authors.initials: JP
authors.lastname: Laceby
authors.forename: Sophie
authors.initials: S
authors.lastname: Ayrault
mesh_terms: D062406:Fukushima Nuclear Accident; D007564:Japan; D055848:Nuclear Power Plants; D010140:Pacific Ocean; D011005:Plutonium / Q000032:analysis* / Q000737:chemistry; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D011868:Radioisotopes / Q000032:analysis; D045483:Rivers / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D011847:Radioactive Fallout; D011868:Radioisotopes; D014875:Water Pollutants, Radioactive; D011005:Plutonium