Main content area

Impact of drying and wetting cycles on 137Cs ageing in forest soils contaminated with different input forms

Teramage, Mengistu T., Carasco, Loic, Coppin, Frederic
Journal of environmental radioactivity 2019 v.203 pp. 93-97
acetates, cesium, detection limit, forests, plant litter, polluted soils, radioactivity, radionuclides, soil amendments, wet-dry cycles, Japan
Water and acetate extractable radiocesium (137Cs) concentrations were monitored for >400 days in soils that were amended with aqueous 137Cs or solid organic sources of 137Cs (plant litter or fragmented organic materials) and subjected to a series of wet-dry cycles. The soils were collected from broadleaf and cedar forests in Fukushima, Japan. In soils amended with aqueous 137Cs, the water extractable 137Cs fraction was very low (<1%) and decreased over time while it was below the detection limit in soils amended with solid organic sources of 137Cs. The acetate extractable 137Cs in soil amended with aqueous 137Cs also exhibited an exponential decrease over time (∼55%–30%) but, remained higher than in soils amended by solid organic sources of 137Cs which remained stable (ranging from 2% to 15%). These results collectively indicate that: (1) drying and wetting cycles have little impact on 137Cs availability, possibly due to the relatively short observation period; (2) 137Cs ageing (increased binding to soil) was apparent only when 137Cs was applied in the aqueous form; and (3) both the water and acetate-extractable 137Cs fractions were greater for aqueous amended than for solid organic amended soils. More acetate extractable 137Cs was observed in soils contaminated with broadleaf materials compared to their cedar counterparts, which may be linked to the nature of the organic material itself. For natural conditions, such kind of information is useful to improve our understanding of the evolution of 137Cs availability with time from different contamination sources.