Investigation of Spatial Distribution of Radiocesium in a Paddy Field as a Potential Sink

Surface soils, under various land uses, were contaminated by radionuclides that were released by the Fukushima Daiichi Nuclear Power Plant accident. Because paddy fields are one of the main land uses in Japan, we investigated the spatial distribution of radiocesium and the influence of irrigation water in a paddy field during cultivation. Soil core samples collected at a paddy field in Fukushima showed that plowing had disturbed the original depth distribution of radiocesium. The horizontal distribution of radiocesium did not show any evidence for significant influence of radiocesium from irrigation water, and its accumulation within the paddy field, since the original amount of radiocesium was much larger than was added into the paddy field by irrigation water. However, it is possible that rainfall significantly increases the loading of radiocesium.

在多种土地利用方式下，地表土壤受到了由福岛第一核电站事故释放的放射性核素污染。鉴于稻米田在日本土地利用中的主要地位，本研究对稻米田种植期间铯-137的空间分布及灌溉水的影响进行了调查。在福岛县一稻米田采集的土壤芯样表明，耕作已扰乱了铯-137的原有深度分布。铯-137的水平分布并未显示出灌溉水中铯-137对土壤的显著影响，且在稻米田内的积累量，相较于灌溉水所加入的铯-137总量而言，已相当可观。然而，降雨可能显著增加了铯-137的负荷。