Biogeosciences Discuss., 10, 6377-6416, 2013
www.biogeosciences-discuss.net/10/6377/2013/
doi:10.5194/bgd-10-6377-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout
P. P. Povinec1, M. Aoyama2, D. Biddulph3, R. Breier1, K. Buesseler4, C. C. Chang3,5, R. Golser6, X. L. Hou7, M. Ješkovský1, A. J. T. Jull3,5,8, J. Kaizer1, M. Nakano9, H. Nies10, L. Palcsu8, L. Papp8, M. K. Pham10, P. Steier6, and L. Y. Zhang7
1Centre for Nuclear and Accelerator Technologies, Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, 84248 Bratislava, Slovakia
2Department of Geochemistry, Meteorological Research Institute, Tsukuba, Japan
3NSF Arizona AMS Laboratory, University of Arizona, Tucson, Arizona 85721, USA
4Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, USA
5Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
6VERA Laboratory, Faculty of Physics, University of Vienna, Austria
7Center for Nuclear Technology, Technical University of Denmark, Risø, Roskilde, Denmark
8Institute for Nuclear Research (ATOMKI), 4026 Debrecen, Hungary
9Japan Atomic Energy Agency, Tokai-mura, Japan
10Environment Laboratories, International Atomic Energy Agency, Monaco

Abstract. Radionuclide impact of the Fukushima Dai-ichi nuclear power plant accident on the distribution of radionuclides in seawater of the NW Pacific Ocean is compared with global fallout from atmospheric tests of nuclear weapons. Surface and water column seawater samples collected during the international expedition in June 2011 were analyzed for 134Cs, 137Cs, 129I and 3H. The 137Cs, 129I and 3H levels in surface seawater offshore Fukushima varied between 0.002–3.5 Bq L−1, 0.01–0.8 μ Bq L−1, and 0.05–0.15 Bq L−1, respectively. At the sampling site about 40 km from the coast, where all three radionuclides were analyzed, the Fukushima impact on the levels of these three radionuclides represent an increase above the global fallout background by factors of about 1000, 30 and 3, respectively. The water column data indicate that the transport of Fukushima-derived radionuclides downward to the depth of 300 m has already occurred. The observed 137Cs levels in surface waters and in the water column are in reasonable agreement with predictions obtained from the Ocean General Circulation Model, which indicates that the radionuclides have been transported from the Fukushima coast eastward. The 137Cs inventory in the water column (the area from 34 to 37° N, and from 142 to 147° E) due to the Fukushima accident is estimated to be about 2.2 PBq. The amount of 129I and 3H released and deposited on the NW Pacific Ocean after the Fukushima accident was estimated to be about 7 GBq and 0.1 PBq, respectively. Due to a suitable residence time in the ocean, Fukushima-derived radionuclides will provide useful tracers for isotope oceanography studies on the transport of water masses in the NW Pacific Ocean.

Citation: Povinec, P. P., Aoyama, M., Biddulph, D., Breier, R., Buesseler, K., Chang, C. C., Golser, R., Hou, X. L., Ješkovský, M., Jull, A. J. T., Kaizer, J., Nakano, M., Nies, H., Palcsu, L., Papp, L., Pham, M. K., Steier, P., and Zhang, L. Y.: Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout, Biogeosciences Discuss., 10, 6377-6416, doi:10.5194/bgd-10-6377-2013, 2013.
 
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