Uranium(VI) Sorption on Organogenic and Mineral Soil Horizons

The uranium(VI) sorption in organogenic and mineral horizons of peaty-podzolic-gleyic and alluvial sod-gley soils collected in Nelidovo raion, Tver oblast was studied. The fraction of adsorbed uranium and the process kinetics are determined by the soil horizon composition. In deep horizons with high content of nonsilicate iron, the uranium adsorption occurs rapidly (within less than a day) and quantitatively. In upper horizons with high organic matter content, the fraction of adsorbed uranium showed pronounced dependence on time and on the amount of dissolved organic matter in the solution. The local surrounding of uranium was analyzed by X-ray absorption spectroscopy and by sequential extraction. The uranium valence state and the main soil components responsible for uranium binding were determined by X-ray absorption spectroscopy. The uranium availability fractions were analyzed by sequential extraction. The set of data obtained using independent analysis methods significantly supplements the existing views on the uranium(VI) behavior in soils.