Takata Hyoe, Wada Toshihiro, Aono Tatsuo, Inoue Mutsuo, Kanasashi Tsutomu, Suzuki Shotaro, Amano Yosuke
Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima 960-1296, Japan.
Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima 960-1296, Japan.
Sci Total Environ. 2022 Feb 1;806(Pt 3):151216. doi: 10.1016/j.scitotenv.2021.151216. Epub 2021 Oct 27.
The distributions of dissolved Cs 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 Cs 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 Cs to coastal waters. In contrast, the extremely low activities of dissolved and particulate Cs in the Tedori River of Ishikawa Prefecture on the western side of Japan along the Japan Sea suggested that inputs of riverine Cs made a negligible contribution to the increase of dissolved Cs activities in the nearshore and offshore waters. The relatively high dissolved Cs activities observed in the offshore waters of the Japan Sea were due to movement of FDNPP-derived Cs into the Japan Sea via the Tsushima Warm Current. Mechanisms controlling the distributions of Cs activities in coastal waters of the eastern and western sides of Japan therefore differ.
2018 - 2021年，即福岛第一核电站事故发生7 - 10年后，研究了日本本州岛东西两岸河流、近岸和近海水中溶解态铯的分布情况。在西北太平洋沿岸东侧（福岛县），河口过程，包括从河流颗粒物上解吸以及溶解到沉降至海底的河流颗粒物的孔隙水中，有助于维持近岸和近海水中较高的溶解态铯活度。在福岛北部半封闭河口区域松川浦进行的一项调查和质量平衡计算，提供了令人信服的证据，表明河流导致铯流入沿海水域。相比之下，在日本西侧日本海沿岸石川县的手取川中，溶解态和颗粒态铯的活度极低，这表明河流铯输入对近岸和近海水中溶解态铯活度增加的贡献可忽略不计。在日本海近海水域观测到的相对较高的溶解态铯活度，是由于福岛第一核电站产生的铯通过对马暖流进入日本海。因此，控制日本东西两岸沿海水域铯活度分布的机制有所不同。
