2015 年 13 巻 5 号 p. 383-394
Radioactive contamination resulting from the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station disaster following the Great East Japan earthquake and tsunami on March 11, 2011, has affected large areas of land in Fukushima, Japan. At present, agriculture has been limited to some areas, and there are concerns that radioactive substances carried by rainwater might contaminate water bodies such as ponds and rivers. In order to resume safe agricultural activities, evaluating the dynamics of radioactive substances in agricultural water is essential. In this study, we measured the concentration and analyzed the impact of radioactive cesium in irrigation water on rice in five districts having limited residential population. Further, we analyzed the radioactive cesium balance and soil samples from decontaminated paddy fields. The main findings of the study are (1) radioactive cesium in agricultural water was mainly in suspended form at the experimental locations within the 40 km zone; (2) most of the radioactive cesium in the irrigation water was accumulated in the paddy field, but radioactive cesium in irrigation water had limited impact on brown rice cultivation; and (3) continual monitoring of areas with radiation levels higher than those recorded in this study is recommended.