Effect of Soil Organic Matter on the Enhancement of Caesium Fixation by Soil Mixed with Minerals

Abstract

Wastes containing high concentrations of radiocaesium released from the Fukushima Dai-ichi Nuclear Power Plant have been disposed in controlled landfill sites. In these landfill sites, soil layers were installed around the waste to prevent leaching of radiocaesium from the waste via precipitation. The objective of this study was to enhance Cs retention in the soil layers by mixing clay minerals. In andosol and brown forest soil, the amount of Cs fixed in the soil increased with the mineral mixing ratio; however, the amount of Cs fixed in gray lowland soil was independent of the mineral mixing ratio. In addition, the inhibition of Cs sorption by organic matter dissolved from each soil was examined by comparing the estimated amount with the actual amount of sorbed Cs. The obtained results suggest that the inhibition of Cs sorption onto clay minerals mixed with soil occurred due to the organic matter sorbed by the minerals.