Vertical profiles of 228Ra and 226Ra activities in the Sea of Japan and their implications on water circulation

Journal of Radioanalytical and Nuclear Chemistry volume 303, pages1309–1312(2015)Cite this article

Abstract

We analyzed a total of 25 seawater samples collected from 2 columns within the Sea of Japan for 226Ra (half life 1,600 years) and 228Ra (half life 5.75 years) by employing low-background γ-spectrometry. The 228Ra activity level in the deep proper water (DPW) (~0.13 mBq/L) was found to be higher than that of deep waters from the Pacific and Atlantic Oceans (<0.1 mBq/L), indicating its continuous delivery to the DPW by active water circulation before complete radioactive decay. Using a steady state box model of 226Ra and 228Ra, the turn-over time in the DPW was calculated to be ~80 years.

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Acknowledgments

We thank the researchers, captain, and crew of the R/V Soyo Maru for their assistance during sampling. This study was supported partly by a Grant-in-Aid for Scientific Research No. 21510011 (M. Inoue) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

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Author notes

  1. M. Minakawa

    Present address: National Research Institute of Aquaculture, Fisheries Research Agency, Nakatsuhamaura, Minami-Ise, Mie, 516-0193, Japan

Affiliations

  1. Low Level Radioactivity Laboratory, Kanazawa University, Nomi, Ishikawa, 923-1224, Japan

    M. Inoue, K. Yoshida, Y. Nakano, H. Kofuji, S. Nagao, Y. Hamajima & M. Yamamoto

  2. National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, 236-8648, Japan

    M. Minakawa

  3. Japan Marine Science Foundation, Minato, Mutsu, Aomori, 035-0064, Japan

    H. Kofuji

Authors
  1. M. Inoue
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  2. M. Minakawa
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  3. K. Yoshida
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  4. Y. Nakano
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  5. H. Kofuji
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  6. S. Nagao
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  7. Y. Hamajima
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  8. M. Yamamoto
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Correspondence to M. Inoue.

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Inoue, M., Minakawa, M., Yoshida, K. et al. Vertical profiles of 228Ra and 226Ra activities in the Sea of Japan and their implications on water circulation. J Radioanal Nucl Chem 303, 1309–1312 (2015). https://doi.org/10.1007/s10967-014-3492-4

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Keywords

  • 228Ra
  • 226Ra
  • Low-background γ-spectrometry
  • Deep proper water
  • Sea of Japan
  • Turn-over time