Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 69(11): 341-352 (2020)


東京電力福島第一原子力発電所事故由来のI-131及び放射性セシウムの葉菜類のウェザリング半減期の主要因に関する考察(1)実測値によるウェザリング半減期Major Factors Affecting Weathering Half-lives of Iodine-131 and Radiocaesium in Leafy Vegetables Directly Contaminated by Fukushima Dai-ichi Nuclear Power Plant Accident Fallout(1) Calculating Weathering Half-lives of Leafy Vegetables Using Data Observed after the Fukushima Nuclear Accident

量子科学技術研究開発機構量子医学・医療部門放射線医学総合研究所National Institutes for Quantum and Radiological Science and Technology, Quantum Medical Science Directorate, National Institute of Radiological Sciences

受付日:2020年5月13日Received: May 13, 2020
受理日:2020年8月5日Accepted: August 5, 2020
発行日:2020年11月15日Published: November 15, 2020

葉菜類に直接沈着した放射性物質濃度の減少の速さは,ウェザリング半減期(Tw)で推定できる。しかし実環境で得た葉菜類のTw値はこれまで報告がなかった。そこで我々は東京電力福島第一原子力発電所事故直後の2011年3–4月に測定したフキ及び厚労省の食品モニタリングで報告された野菜の131Iと放射性Cs濃度データから,Twを導出した。その結果,Twの幾何平均値は131Iが8.4 d, 放射性Csが7.6 dであり,核種間に有意差はなかった。

Radioactivity-concentration decline rates from leafy vegetables after receiving direct deposition of radionuclides can be estimated using weathering half-life (Tw). However, Tw data for leafy vegetables observed under the field conditions are not reported yet. Therefore, we calculated Tw values for 131I and radiocaesium using our data for giant butterbur leaves, and also using vegetable data from food monitoring conducted by the Ministry of Health, Labour and Welfare; both were observed in March to April 2011, just after the occurrence of the Fukushima Dai-ichi Nuclear Power Plant Accident. The results showed that the geometric mean Tw values for 131I was 8.4 d, and for radiocaesium was 7.6 d; no significant difference was observed between Tw values of these radionuclides.

Key words: effective half-life; direct deposition; translocation; leafy vegetables; outdoor cultivation; growth dilution effect

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