Low 137Cs retention capability of organic layers in Japanese forest ecosystems affected by the Fukushima nuclear accident

Quantitative understanding of Cs-137 retention behavior in organic layers in Japanese forest ecosystems is of primary importance in the assessment of long-term radioecological impacts of the Fukushima nuclear accident. Litter samples were collected at five forest sites in Fukushima in 2011, 2015, and 2017, and separated into eight fractions with different precursor species and degrees of degradation; afterward, Cs-137 inventory was determined. All fractions exhibited a significant decrease in Cs-137 inventory over the six-year period. The results suggested that the organic layers in Japanese forest ecosystems have a low Cs-137 retention capability, although it differs depending on the forest type.