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Journal of Oceanography

, Volume 72, Issue 1, pp 67–76 | Cite as

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

  • Michio Aoyama
  • Mizuo Kajino
  • Taichu Y. Tanaka
  • Tsuyoshi Thomas Sekiyama
  • Daisuke Tsumune
  • Takaki Tsubono
  • Yasunori Hamajima
  • Yayoi Inomata
  • Toshitaka Gamo
Special Section: Original Article Oceanographic observations after the 2011 earthquake off the Pacific coast of Tohoku

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.

Keywords

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

Notes

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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Copyright information

© The Oceanographic Society of Japan and Springer Japan 2015

Authors and Affiliations

  • Michio Aoyama
    • 1
  • Mizuo Kajino
    • 2
    • 3
  • Taichu Y. Tanaka
    • 2
  • Tsuyoshi Thomas Sekiyama
    • 2
  • Daisuke Tsumune
    • 4
  • Takaki Tsubono
    • 4
  • Yasunori Hamajima
    • 5
  • Yayoi Inomata
    • 6
  • Toshitaka Gamo
    • 7
  1. 1.Institute of Environmental RadioactivityFukushima UniversityFukushimaJapan
  2. 2.Meteorological Research InstituteTsukuba-ShiJapan
  3. 3.RIKEN Advanced Institute for Computational ScienceKobeJapan
  4. 4.Environmental Science Research LaboratoryCentral Research Institute of Electric Power IndustryAbiko-ShiJapan
  5. 5.Low Level Radioactivity Laboratory, Institute of Nature and Environmental TechnologyKanazawa UniversityNomiJapan
  6. 6.Atmospheric Research DepartmentAsia Center For Air Pollution ResearchNiigataJapan
  7. 7.Atmosphere and Ocean Research InstituteThe University of TokyoKashiwa-shiJapan

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