The impact of radiocesium input forms on its extractability in Fukushima forest soils

The effects of ¹³⁷Cs deposit forms on its ageing in soil have not yet been reported. Soluble and Solid ¹³⁷Cs input forms were mixed with the mineral soils collected under Fukushima's coniferous and broadleaf forests, incubated under controlled laboratory, and examined the evolution of ¹³⁷Cs availability over time. Results show that the extracted ¹³⁷Cs fraction with water was less than 1% for the soluble input form and below detection limit for the solid input forms. Likewise, with an acetate reagent, the extracted ¹³⁷Cs fraction ranged from 46 to 56% for the soluble input and from 2 to 15% for the solid input, implying that the nature of the ¹³⁷Cs contamination strongly influences its extractability and mobility in soil. Although the degradation of organic materials was apparent, its impact on the ¹³⁷Cs extractability was found to be weak. Nevertheless, more Ac-available ¹³⁷Cs was obtained from broadleaf organic material mixes than the coniferous counterparts, suggesting that the lignified nature of latter tend to retain more ¹³⁷Cs. When extrapolated to a field context, more available ¹³⁷Cs fraction may be expected from wet-derived contaminated forest soils than contaminated via solid-derived inputs. Such information could be helpful for radioecological management schemes in contaminated forest environments.