Effect of the Ionic Status and Drying on Radiocesium Adsorption and Desorption in Organic Soils

Radiocesium (RCs) interaction in organic soils has been studied using adsorption and desorption experiments, and the effects of the ionic status and drying were evaluated. Four organic soils were used: three peaty podzols containing illite and a peat without illitic materials. RCs solid−liquid distribution coefficients ( K D ) were determined for each soil in water and in several solutions containing Ca, K, or a mixture of the two. RCs contamination was performed either with a single equilibration or after a three-step preequilibration. Whereas the ionic strength of the solution controlled RCs adsorption in the peat, the level of monovalent species was the most important factor in RCs adsorption in the peaty podzols. Reversibility of RCs adsorbed in the different conditions was assessed in the moist sample and after drying by single and consecutive extractions with either CaCl 2 or CH 3 COONH 4 . RCs adsorption was totally reversible in the peat regardless of the ionic status and the desorption approach used. For the three peaty podzols, due to the presence of specific sites, adsorption reversibility was dependent on the scenario in which this adsorption was performed and on the cation used in desorption. Finally, although NH 4 is known to desorb RCs specifically adsorbed in the soil, it was shown to induce interlayer collapse, and consecutive extractions with CaCl 2 led to higher desorption yields.