Temporal change of Cs-137 concentration in fruit in the non-decontaminated biotope in Saitama, Japan, after the Fukushima Daiichi Nuclear Power Plant accident

抄録

We measured Cs-137 concentrations in persimmon and yuzu (citron) fruits within a non-decontaminated biotope in Saitama Prefecture, which was affected by the Fukushima Daiichi Nuclear Power Plant (FDNPP) incident in 2011, spanning from 2011 to 2019. In 2011, the Cs-137 concentration in yuzus was five times higher than that in persimmons. In 2019, the Cs-137 concentrations in the two fruits were almost the same. Additionally, these values were nearly equal to the yuzus collected in Fukushima Prefecture before the FDNPP accident occurred. The effective half-lives of Cs-137 calculated based on the survey results were 380 days and 310 days for persimmons and yuzus, respectively.

The findings indicated that the Cs-137 concentration in fruits in non-decontaminated areas decreased faster than predicted by the physical half-life of Cs-137, which is 30 years.