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

The effects of Cs deposit forms on its ageing in soil have not yet been reported. Soluble and Solid Cs 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 Cs availability over time. Results show that the extracted Cs 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 Cs 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 Cs contamination strongly influences its extractability and mobility in soil. Although the degradation of organic materials was apparent, its impact on the Cs extractability was found to be weak. Nevertheless, more Ac-available Cs was obtained from broadleaf organic material mixes than the coniferous counterparts, suggesting that the lignified nature of latter tend to retain more Cs. When extrapolated to a field context, more available Cs 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.