Assessment on the behavior of radionuclides released from the Fukushima nuclear accident in the environment

After the accident of Fukushima Daiichi Nuclear Plants, environmental monitoring was carried out by several organizations including MEXT and MAFF and obtained a great deal of data to know the levels of radiation doses and distribution of radiocesium in Fukushima Prefecture and others. However, there are still lack of information to understand the behavior of radionuclides in the environment and ecosystem. In this study we have studied the transfer of radionuclides from soil to plants with a special reference to the effect of soil types as well as that of plant types. Translocation of radiocesium from leaves and barks to fruits and behavior of radiocesium in forest ecosystem were also investigated. In relation to radioiodine, we have carried out analyses of I-129 (half-life: 16 million years) in soil to reconstruct the deposition of I-131 (half-life: 8 days) at the time of the accident, since radioiodine accumulates in thyroid gland. (author)