Establishment of monitoring methods for the residual status of radioactive materials in the forest floor in Fukushima

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K22351
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 41:Agricultural economics and rural sociology, agricultural engineering, and related fields
• Research Institution: Tokyo University of Agriculture
• Principal Investigator: Adati Taro 東京農業大学, 国際食料情報学部, 教授 (50385506)
• Project Period (FY): 2019-06-28 – 2023-03-31
• Keywords: 原発事故 / 福島 / 放射性セシウム / 生物指標 / モニタリング

Outline of Final Research Achievements

To clarify the actual status of the transfer of radioactive cesium (Cs) remaining in forest floor and grassland in Fukusima, radioactive Cs in soil, plants and the short-winged rice grasshopper, Oxya yezoensis, for three years. The results showed significant annual variations in the cesium-137 (137Cs) concentration in grasshoppers and the plant-insect transfer factor. There was a strong positive correlation between the concentrations of 137Cs in grasshoppers collected in 10 m square plots and the spatial radiation dose rates measured in each plot, and the concentrations of 137Cs in food grasses collected near the plots where grasshoppers were collected. These results suggest that the concentration of 137Cs in grasshoppers reflects the level of contamination over a relatively narrow range and is a useful indicator for monitoring the status of remaining radioactive Cs.

Free Research Field

応用昆虫学

Academic Significance and Societal Importance of the Research Achievements

福島の森林には、いまなお多量の放射性Csが残存しており、これを人為的に除去することは容易ではない。広大な面積の除染には膨大なコストがかかり、拙速な実施は生態系の破壊をまねくおそれがある。だが、土壌に沈着している放射性Csの分布には濃淡があり、これを正確に把握できれば、除染を加速できる可能性がある。コバネイナゴは汚染地域の森林周辺の草地に生息し、容易に採集することができる。本研究により本種が放射性Csの残存状況を反映する指標としての有効性がしめされたことは、福島の復興をすすめるうえで学術的・社会的な意義があるといえよう。