The influence of soil properties on sorption-desorption of beryllium at a low level radioactive legacy waste site

This study examined the influence of soil physicochemical properties on the sorption, desorption and kinetics of beryllium (Be) uptake and release on soils from a legacy waste site in Australia. This infor-mation is needed to help explain the current distribution of Be at the site and evaluate potential future environmental risks. Sorption was determined by a batch study and key soil properties were assessed to explain Be retention. The soil was favourable for sorption of Be (up to 99%) due to organic content, negative surface charge, soil oxyhydroxides (Fe/Al/Mn-O/OH) and the porosity of the soil structure. Lesser sorption was observed in the presence of a background electrolyte (NaNO3). Sorption closely followed pseudo second order kinetics and was best described by the Langmuir model. FTIR analysis suggested that chemisorption was the predominant mechanism of Be sorption. Desorption was very low and best described by the Freundlich model. The low desorption reflected the high Kd (up to 6624 L/kg), and the presence of hysteresis suggested partially irreversible binding of Be with active surfaces of the soil matrix (minerals, SOM, oxyhydroxides of Fe/Al/Mn etc.). Intra-particle diffusion of Be and entrap-ment in the pores contribute to the irreversible binding. The sorption behaviour of Be helped to explain the relative immobility of Be at the site despite the significant quantities of Be disposed. Soil physicochemical properties were significant for Be sorption, through influencing both the uptake and desorption, and this demonstrates the implications of these measurements for evaluating potential future risks to the environment. Crown Copyright (C) 2021 Published by Elsevier Ltd. All rights reserved.