Isotopic investigation of the colloidal mobility of depleted uranium in a podzolic soil

• Published in: Chemosphere (Oxford) 2014-05, Vol.103, p.343-348
• Main Authors: Harguindeguy, S., Crançon, P., Pointurier, F., Potin-Gautier, M., Lespes, G.
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Applied sciences; Batch experiments; Biological and physicochemical properties of pollutants. Interaction in the soil; Chemical Sciences; Colloids; Colloids - chemistry; Depleted uranium; Exact sciences and technology; Isotopes; Leaching; Mobility; Pollution; Soil - chemistry; Soil and sediments pollution; Soil Pollutants, Radioactive - analysis; Ultrafiltration; Uranium - analysis; Water Pollutants, Radioactive - analysis
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2013.12.033

•We investigated the colloidal transport of uranium in a contaminated site.•We clearly shows the importance of colloids in uranium mobilization and migration.•Mobilization of anthropogenic uranium is enhanced compared to native uranium.•Smaller colloids are likely to dominate for the sorption of anthropogenic uranium.•Native natural uranium is mainly associated with coarser fractions. The mobility and colloidal migration of uranium were investigated in a soil where limited amounts of anthropogenic uranium (depleted in the 235U isotope) were deposited, adding to the naturally occurring uranium. The colloidal fraction was assumed to correspond to the operational fraction between 10kDa and 1.2μm after (ultra)filtration. Experimental leaching tests indicate that approximately 8–15% of uranium is desorbed from the soil. Significant enrichment of the leachate in the depleted uranium (DU) content indicates that uranium from recent anthropogenic DU deposit is weakly bound to soil aggregates and more mobile than geologically occurring natural uranium (NU). Moreover, 80% of uranium in leachates was located in the colloidal fractions. Nevertheless, the percentage of DU in the colloidal and dissolved fractions suggests that NU is mainly associated with the non-mobile coarser fractions of the soil. A field investigation revealed that the calculated percentages of DU in soil and groundwater samples result in the enhanced mobility of uranium downstream from the deposit area. Colloidal uranium represents between 10% and 32% of uranium in surface water and between 68% and 90% of uranium in groundwater where physicochemical parameters are similar to those of the leachates. Finally, as observed in batch leaching tests, the colloidal fractions of groundwater contain slightly less DU than the dissolved fraction, indicating that DU is primarily associated with macromolecules in dissolved fraction.