Abstracts of Nipon Dojo-Hiryogaku Zasshi

We investigated changes in radiocesium concentrations in a Japanese chestnut (Castanea crenata Sieold &; Zucc.) orchard in Ibaraki prefecture for 3 years after the Tokyo Electric Power Company’s Fukushima Daiichi nuclear power plant accident in March 2011. The radiocesium concentrations in the aboveground organs of Japanese chestnut trees were almost the same, while the concentration in the roots was the lowest among all the organs investigated. The concentration of radiocesium decreased exponentially for 3 years in nuts, leaves and current shoots. The radiocesium concentrations in soils were higher in the surface layer, and the trend of an annual decrease in radiocesium in the soils was similar to that of the natural decay of radiocesium. The transfer factor of radiocesium from soils to nuts of Japanese chestnut decreased annually. These results suggest that radiocesium adhered directly to the aboveground organs of Japanese chestnut trees in March 2011, and that the accumulation of radiocesium in nuts is mainly due to radiocesium transfer from the branches and trunk to nuts several years after the nuclear power plant accident.