Elucidation of the mechanism of additional contamination by radioactive cesium in shiitake mushrooms cultivated on bed logs

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K06177
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40020:Wood science-related
• Research Institution: Forest Research and Management Organization
• Principal Investigator: Hiraide Masakazu 国立研究開発法人森林研究・整備機構, 森林総合研究所, 主任研究員 等 (20353823)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 追加汚染 / 原木栽培シイタケ / 交換性セシウム

Outline of Final Research Achievements

The purpose of this study was to elucidate the mechanism of additional contamination of shiitake mushrooms grown on bed logs in a radiation-contaminated area, and to examine whether radiocesium in the soil is transferred to the fruiting bodies through the bed log. Before clarification, it was found that the concentration of cesium absorbed by the fruiting-bodies was strongly influenced by the concentration of ion-exchange-form cesium in the bed logs. After 15 months of bed log cultivation on soil containing radioactive cesium collected in Fukushima Prefecture, no transfer of radioactive cesium from soil to bed logs was observed, and no significant contamination of the fruiting-bodies was observed. It is assumed that the radiocesium in the soil is not an additional source of contamination because the radiocesium in the soil is tightly adsorbed on soil minerals.

Free Research Field

きのこ学

Academic Significance and Societal Importance of the Research Achievements

汚染地域における原木しいたけ栽培は、直接汚染と追加汚染による被害を被った。直接汚染の汚染源がフォールアウトであるのに対して追加汚染の汚染源は土壌中の放射性セシウムであり、これらがほだ木へ移行することにより追加汚染が生じると推測された。しかし、原発事故から10年以上経過して放射性セシウムは土壌鉱物に強固に吸着されたためか、土壌からほだ木への放射性セシウムの移行は認められず、また栽培現場からも追加汚染による被害は聞かれなくなった。なお、ほだ木下部に発生した子実体にはまれに若干の汚染が認められたが、これらは土壌との偶発的な接触によるためと考えられる。