量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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It has been recognized that 14C is one of the dominant radionuclides affecting dose from TRU wastes. This radionuclide has a decay half-life of 5,730 years, and 14C-organic materials have very low sorption properties to clay and rock in the environment. This raises some concerns about the releases of 14C to the biosphere from radioactive waste repositories. For the safety assessment of TRU waste disposal, we studied the behavior of 14C in rice paddy field soils. We also determined key parameters such as soil-soil solution distribution coefficients (Kds) and soil-to-rice plant transfer factors (TFs) of 14C in the field soils. The TFs were obtained in laboratory and field experiments. In our laboratory experiments, we used [1,2-14C] sodium acetate as a source of 14C because it has been suggested that low-molecular-weight organic-14C compounds are released from metallic TRU wastes. The results showed that 14C-bearing sodium acetate in irrigated paddy soils was rapidly decomposed by indigenous bacteria. Although some of the 14C was assimilated into the bacterial cells, most of the 14C was released into the air as gaseous compounds. The main chemical species of 14C gases was 14CO2, and a part of the released 14CO2 gas was used by rice plants during photosynthesis. Only a negligible amount of 14C was absorbed through the roots. Therefore, the contamination of rice plants is mainly caused by gasification of 14C, and microorganisms are responsible for driving this process. The activity of microorganisms is a key issue in the behavior of 14C in paddy fields.
雑誌名
Environmental Transfer of carbon-14 in Japanese paddy fields
Environmental Transfer of carbon-14 in Japanese paddy fields
