量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果(学会誌発表論文、学会発表、研究開発報告書、特許等)を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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The distributions of dissolved 137Cs in river, nearshore, and offshore waters on the east and west coasts of the Japanese island of Honshu were studied in 2018–2021, 7–10 years after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. On the east side along the north western North Pacific (Fukushima Prefecture), estuarine processes, including desorption from riverine particles and dissolution into pore water from riverine particles that had settled to the seafloor, contributed to the maintenance of high dissolved 137Cs activities in nearshore and offshore waters. A survey and mass-balance calculation in a semi-enclosed estuarine area, the Matsukawa-ura, in the northern part of Fukushima, provided convincing evidence that rivers contributed to the influx of 137Cs to coastal waters. In contrast, the extremely low activities of dissolved and particulate 137Cs in the Tedori River of Ishikawa Prefecture on the western side of Japan along the Japan Sea suggested that inputs of riverine 137Cs made a negligible contribution to the increase of dissolved 137Cs activities in the nearshore and offshore waters. The relatively high dissolved 137Cs activities observed in the offshore waters of the Japan Sea were due to movement of FDNPP-derived 137Cs into the Japan Sea via the Tsushima Warm Current. Mechanisms controlling the distributions of 137Cs activities in coastal waters of the eastern and western sides of Japan therefore differ.