Investigation of cesium adsorption on soil and sediment samples from Fukushima Prefecture by sequential extraction and EXAFS technique

Previous studies have shown that radiocesium (mainly Cs-132) was retained at the very surface of soils in Fukushima Prefecture. Clay minerals and micas are assumed as the main sorbents for cesium (Cs) in Fukushima, but direct evidence is lacking for this hypothesis. In this study, racliocesium in the natural sample (soil and sediment) from Fukushima Prefecture was investigated through sequential extraction experiment (modified BCR method), which showed that more than 94% of Cs-137 was fixed in the residual phase. The results indicated that most of Cs occurred in the interlayer of phyllosilicate minerals. Furthermore, Cs L-III-edge extended X-ray absorption fine structure (EXAFS) showed that the Cs species adsorbed on the natural samples were very similar to those adsorbed on clay minerals and micas. This finding provided the direct evidence on the significant contribution of clay minerals or micas to Cs retention in soils from Fukushima Prefecture.