²²⁸Ra/²²⁶Ra ratio and ⁷Be concentration in the Sea of Japan as indicators for water transport: comparison with migration pattern of Fukushima Dai-ichi NPP-derived ¹³⁴Cs and ¹³⁷Cs

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• 作者：M. Inoue ; Y. Furusawa ; K. Fujimoto ; M. Minakawa ; H. Kofuji ; S. Nagao ; M. Yamamoto ; Y. Hamajima ; K. Yoshida ; Y. Nakano ; K. Hayakawa ; S. Oikawa ; J. Misonoo ; Y. Isoda
• 关键词：228Ra/226Ra ratio ; 7Be ; 134Cs ; Current profiles ; Fukushima Dai-ichi Nuclear Power Plant accident ; Sea of Japan
• 刊名：Journal of Environmental Radioactivity
• 出版年：December, 2013
• 年：2013
• 卷：126
• 期：Complete
• 页码：176-187
• 全文大小：1257 K

文摘

To assess the migration patterns of radiocesium emitted from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we analyzed ²²⁸Ra/²²⁶Ra ratios and ⁷Be concentrations and compared them with ¹³⁴Cs and ¹³⁷Cs concentrations in seawater samples collected within the Sea of Japan before and after the FDNPP accident (i.e., during the period 2007-2012) using low-background 纬-spectrometry. The ²²⁸Ra/²²⁶Ra ratios in surface waters exhibited lateral and seasonal variations, reflecting the flow patterns of surface water. This indicates the transport patterns of the FDNPP-derived radiocesium by surface water. Cosmogenic ⁷Be (half-life: 53.3 d) exhibited markedly high concentrations (5-10聽mBq/L) at depths shallower than 50聽m, with concentrations decreasing steeply (0.2-2聽mBq/L) at depths of 50-250聽m. The distribution of ⁷Be concentrations suggests that the downward delivery of the FDNPP-derived radiocesium to below 50聽m depth was negligible for a few months prior to its removal from the Sea of Japan.