Abstract
Understanding the behaviors of Cs+ in soils is crucial for evaluation of the impacts of disposal of soils contaminated by radiocesium, 137Cs. The desorption rate of Cs+ evaluated in relatively short periods of time may not be adequate for such a purpose. In this study, we investigated long-term desorption kinetics of 137Cs and 133Cs from soils collected in Fukushima Prefecture by batch desorption experiments in the presence of cation exchange resin as a sorbent. The sorbent can keep the concentration of Cs+ in the aqueous phase low and prevent re-sorption of desorbed Cs+. Up to 60% of 137Cs was desorbed after 139 d in dilute KCl media, which was larger than the desorption by conventional short-term extraction with 1 M ammonium acetate. Desorption of 137Cs continued even after this period. It was also found that high concentration of K+ prevented desorption of Cs+ in the initial stage of desorption, but the effect was alleviated with time. The desorbed fraction of stable Cs was smaller than that of 137Cs. This indicated that 137Cs may gradually move to more stable states in soils. The half-life of 137Cs desorption from the slowest sorption site was estimated to be at least two years by a three-site desorption model.
Published Version
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