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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Due to limited numbers of radium-226 (226Ra) soil-to-plant transfer data, it has been difficult to analyze the sampling area differences. In this study, we measured 226Ra concentrations in brown rice and associated soils collected from 61 locations throughout Japan and obtained soil-to-rice transfer factors (TFs). Concentrations of 226Ra in the soils collected in southwestern Japan were higher than those in northeastern Japan (t-test, p<0.001); for example, the geometric mean (GM) of 226Ra in southwestern Japan was 40.4 Bq/kg-dry (N=33) and it was 27.8 Bq/kg (N=28) in northeastern Japan, reflecting geological differences between these areas. Using the measured data, we compared TFs in these two areas and found no difference, i.e., the GM in southwest was 4.6x10-4 and it was 4.9x10-4 in northeast. The observed TFs were about one order of magnitude lower than the previously reported TF values for cereals (maize, wheat, and rice), but in the same range for previously reported data for white rice. Among the alkaline earth metals, TF for Ba was well correlated to TF for Ra, but because Ba and Ra concentrations in brown rice were highly correlated, the TF would also be expected to correlate.