134Cs and 137Cs in the North Pacific Ocean derived from the March 2011 TEPCO Fukushima Dai-ichi Nuclear Power Plant accident, Japan. Part two: estimation of 134Cs and 137Cs inventories in the North Pacific Ocean

Journal of Oceanography volume 72, pages67–76(2016)Cite this article

Abstract

We estimated the inventories of radiocaesium released by the Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident to the North Pacific Ocean by using compiled data and model simulations. By comparing the observed inventories with model-simulated results, we obtained 12–15 PBq of 137Cs for the atmospheric deposition released by the FNPP1 accident in the North Pacific Ocean. Before the Fukushima accident, 137Cs activity in the North Pacific Ocean was about 69 PBq. Therefore, the 12–15 PBq of 137Cs newly added by atmospheric deposition together with the 3.5 ± 0.7 PBq added by direct discharge increased the total 137Cs inventory in the North Pacific Ocean by 22–27 %. We also estimated the total amount of 137Cs released to the atmosphere to be 15–20 PBq, and the total amount of 137Cs released to the environment to be 19–24 PBq, respectively. Observed 134Cs to 137Cs activity ratio at the time of accident was close to 1 and extremely uniform, therefore, the total amount of 134Cs deposition in the North Pacific Ocean, that of released to the atmosphere, that of direct discharge to the ocean and that of released to the environment were the same amounts as those of 137Cs.

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Acknowledgments

This study was supported in part by the radioactive survey and research fund of Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (Houshanou-chousa-kenkyuhi, FY2011-2014), in part by the J-RAPID fund of the Japan Science and Technology Agency as part of a project entitled “Investigation and Prediction of Impacts of The 2011 off the Pacific coast of Tohoku Earthquake on Marine Environment, FY2011-2012”, and by a Grant-in-Aid for Scientific Research (A) (No. 23253001) from MEXT. The authors thank Yukiko Suda and Aoi Mori for preparing the tables and figures for this article.

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Affiliations

  1. Institute of Environmental Radioactivity, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan

    Michio Aoyama

  2. Meteorological Research Institute, 1-1 Nagamine, Tsukuba-Shi, Ibaraki-ken, 305-0052, Japan

    Mizuo Kajino, Taichu Y. Tanaka & Tsuyoshi Thomas Sekiyama

  3. RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minamimach, Chuo-ku, Kobe, Hyogo, 650-0047, Japan

    Mizuo Kajino

  4. Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-Shi, Chiba-ken, 270-1194, Japan

    Daisuke Tsumune & Takaki Tsubono

  5. Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Nomi, Ishikawa, 923-1224, Japan

    Yasunori Hamajima

  6. Atmospheric Research Department, Asia Center For Air Pollution Research, 1182 Sowa, Nishi-ku, Niigata, 950-2144, Japan

    Yayoi Inomata

  7. Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8564, Japan

    Toshitaka Gamo

Authors
  1. Michio Aoyama
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  2. Mizuo Kajino
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Correspondence to Michio Aoyama.

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Aoyama, M., Kajino, M., Tanaka, T.Y. et al. 134Cs and 137Cs in the North Pacific Ocean derived from the March 2011 TEPCO Fukushima Dai-ichi Nuclear Power Plant accident, Japan. Part two: estimation of 134Cs and 137Cs inventories in the North Pacific Ocean. J Oceanogr 72, 67–76 (2016). https://doi.org/10.1007/s10872-015-0332-2

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Keywords

  • Fukushima Dai-Ichi Nuclear Power Plant accident
  • Atmospheric release
  • Direct discharge
  • Inventory
  • 134Cs
  • 137Cs
  • Radiocaesium
  • Land deposition