The Influence of Remedial Actions on Ambient Dose Rates in Fukushima Forests

This study evaluates the long-term impact of government-led decontamination efforts on air dose rates in Fukushima forests affected by the 2011 nuclear disaster. While decontamination successfully mitigated radiation risks, its influence on air dose rates over time remains understudied, particularly in comparison to non-remediated forests. A comprehensive assessment spanning 2013 to 2020 was conducted, utilizing governmental decontamination data and monitoring adjacent untreated forests. Despite initial increases post-decontamination, air dose rates generally stabilized, following a trend indicative of physical decay. The study found that dominate tree species in forests influenced dose rate reduction. Broadleaf forests maintained lower post-decontamination dose rates compared to untreated counterparts, while cedar forests experienced increased post-decontamination rates, reverting to pre-decontamination levels. Both forest types exhibited similar annual decrease trends due to physical and environmental decay, with red pine in non-decontaminated forests showing the slowest decline. Analysis of radioactive cesium concentrations in organic matter and soil revealed a gradual transfer from organic matter to soil. Decontamination reduced concentrations in organic material but had no discernible effect on soil concentrations, indicating an ongoing transfer of radioactive materials from organic matter to soil. This emphasizes the need for future remediation strategies to assess local natural restoration potential and this study offers crucial insights for refining forest decontamination strategies and underscores the importance of factoring in ecosystem dynamics in radiation remediation planning.