Sedimentary cesium-137 concentrations around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were measured from 2011 to 2017 at eight stations. Although high values were observed until 2013, decreasing trends were observed at the surface sediments of seven stations. We isolated 25 radioactive Cs-bearing microparticles (CsMPs; 1.0–5385 Bq per particle). The contribution ratio of CsMPs to each sample ranged from 4.1% to 99.5% (median 58.8%), with the contribution ratio of the CsMPs in the southern part of the FDNPP was low compared to that from the northern part. In the southern part of the FDNPP, small CsMPs that could not be isolated in this study were present in large quantities immediately after the accident, and gradually diffused away and/or were dissolved over time. In contrast, the CsMPs in the northern part of the FDNPP have most likely accumulated over time, as suggested by the silty nature of the sediments there.

在2011年至2017年期间，对福岛第一核电站（FDNPP）周围137个沉积物中的铯137浓度进行了测量。尽管直到2013年都观测到高值，但七个站的地表沉积物却出现了下降趋势。我们分离了25个含Cs的放射性微粒（CsMPs；每个微粒1.0-5385 Bq）。CsMP对每个样品的贡献率在4.1％到99.5％之间（中位数58.8％），而FDNPP南部的CsMPs贡献率低于北部。在FDNPP的南部，事故发生后立即存在大量本研究中无法分离的小CsMP，并随时间逐渐扩散和/或溶解。相反，