Monthly Change in Radioactivity Concentration of 137Cs, 134Cs, and 40K of Paddy Soil and Rice Plants in Fukushima Prefecture

• Published in: RADIATION SAFETY MANAGEMENT Vol. 19; pp. 10 - 22
• Main Authors: TSUJIMOTO, Masaya, MIYASHITA, Sunao, NGUYEN, Hai Thanh, NAKASHIMA, Satoru
• Format: Journal Article
• Language: English
• Published: Nagoya Japan Science and Technology Agency 2020
• Subjects: Cesium; Cesium 134; Cesium 137; Cesium isotopes; Cesium radioisotopes; Fieldwork; Germanium; Leaves; Potassium; Potassium 40; Radioactive contamination; Radioactive pollution; Radioactivity; Rice; Rice fields; Roots; Seasonal variations; Soil contamination; Soils
• ISSN: 1347-1511; 1884-9520
• DOI: 10.12950/rsm.181219

Monthly fieldwork was conducted in the paddies of Fukushima Prefecture in 2016, to obtain samples of the paddy soil and rice plants. The monthly change in the radioactivity concentrations of 137Cs, 134Cs, and 40K of the samples was investigated, using a germanium semiconductor detector. Three-phase transfer factors (TFs) of 137Cs from the paddy soil to the roots (TF1), from the roots to the leaves (TF2), and from the leaves to the ears (TF3) of rice plants were calculated. The results showed that the radioactivity concentration of 137Cs and 134Cs in the paddy soil varied seasonally, while the concentration of 40K showed an almost opposite seasonal change compared to 137Cs and 134Cs. The radioactivity concentration of 137Cs and 134Cs in the roots increased 60 days after planting, while the concentration of 40K decreased. Furthermore, the radioactivity concentration of 137Cs, 134Cs, and 40K in the leaves and ears decreased over time. Correlations of the TFs of 137Cs with the radioactivity concentration of 40K suggested that 137Cs and 40K were competitively absorbed by the roots, however, they were transported to the leaves and ears in the same manner. In conclusion, the transportation of 137Cs (TF2 and TF3) in rice plants was high despite the low absorption of 137Cs (TF1) in the early stage of rice growth. Therefore, it is recommended that the potassium concentration in the paddy should be high during the early stage of growth to prevent radioactive cesium contamination.