Atmospheric and Marine Environmental Sector, Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko, Chiba, 270-1194, Japan.
Department of Ocean Sciences, Graduate Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-8477, Japan.
Sci Rep. 2021 Mar 11;11(1):5664. doi: 10.1038/s41598-021-85085-w.
A part of the radiocaesium from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was emitted as glassy, water-resistant caesium-bearing microparticles (CsMPs). Here, we isolated and investigated seven CsMPs from marine particulate matter and sediment. From the elemental composition, the Cs/Cs activity ratio, and the Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3, as suggested by (i) the presence of calcium and absence of zinc and (ii) the direction of the atmospheric plume during the radionuclide emission event from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.
福岛第一核电站（Fukushima Daiichi Nuclear Power Plant，FDNPP）事故中释放出一部分放射性铯，以耐水玻璃状含铯微颗粒（CsMPs）的形式存在。在这里，我们从海洋颗粒物和沉积物中分离并研究了七种 CsMPs。根据元素组成、Cs/Cs 活度比和单位体积 Cs 活度的结果，我们推断出从颗粒物中收集到的五个 CsMPs 是从 FDNPP 的 2 号机组排放的，而从海洋沉积物中收集到的两个 CsMPs 可能是从 3 号机组排放的，这是因为 (i) 存在钙而不存在锌，以及 (ii) 在 3 号机组放射性核素排放期间大气羽流的方向。CsMPs 的存在可能导致海洋沉积物和颗粒物中 Cs 的固-水分配系数被高估，以及海洋生物的放射性铯表观浓度系数偏高。从流经高度污染区的河流的河口收集到的来自 2 号机组的 CsMPs，可能已经在陆地上沉积，然后被河流输送。相比之下，可能是 3 号机组排放的 CsMPs 被风吹向东，并直接沉积在海洋表面上。
