Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169 Sukakeba, Minamisoma, Fukushima, 975-0036, Japan.
NESI Inc, 38 Shinko-cho, Hitachinaka, Ibaraki, 312-0005, Japan.
Sci Rep. 2021 Nov 30;11(1):23175. doi: 10.1038/s41598-021-02646-9.
Large quantities of volatile radionuclides were released into the atmosphere and the hydrosphere following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March, 2011. Monitoring of radiocesium in sediment is important for evaluating the behavior of radiocesium in the environment and its effect on aquatic organisms. In this study, the radiocesium distribution in the surface sediment around the FDNPP was visualized as a radiocesium concentration map using periodical survey data from a towed gamma-ray detection system. The uncertainty of the radiocesium map was evaluated via comparison with a large amount of sediment core sample data. The characteristics of the radiocesium distribution were examined considering the seafloor topography and a geological map, which were obtained via acoustic wave survey. The characteristics of the formation of Cs anomaly at the estuaries were analyzed using a contour map of Cs concentration combined with water depth. Validation of the created map showed that it was comparable with actual sediment core samples. The map generated using the towed radiation survey depicted the Cs concentration distribution as the position resolution of a 1 km mesh. Finally, the Cs concentration decreased with time in consideration of such uncertainty.
大量易挥发的放射性核素于 2011 年 3 月福岛第一核电站（FDNPP）事故后被释放到大气和水圈中。监测沉积物中的放射性铯对于评估放射性铯在环境中的行为及其对水生生物的影响非常重要。在这项研究中，使用拖曳式伽马射线探测系统的定期调查数据，将福岛第一核电站周围表层沉积物中的放射性铯分布可视化，生成放射性铯浓度图。通过与大量沉积物芯样本数据进行比较，评估了放射性铯图的不确定性。考虑到海底地形和通过声波测量获得的地质图，研究了放射性铯分布的特征。通过结合水深的 Cs 浓度等高线图分析了河口 Cs 异常形成的特征。对生成的地图进行验证的结果表明，它与实际的沉积物芯样本相当。使用拖曳辐射调查生成的地图以 1 公里网格的位置分辨率描绘了 Cs 浓度分布。最后，考虑到这种不确定性，Cs 浓度随时间而降低。
