To gain insights into the risks associated with uranium (U) mining and processing, we investigated the biogeochemical controls of U bioavailability in the model freshwater species Lymnaea stagnalis (Gastropoda). Bioavailability of dissolved U(VI) was characterized in controlled laboratory experiments over a range of water hardness, pH, and in the presence of complexing ligands in the form of dissolved natural organic matter (DOM). Results show that dissolved U is bioavailable under all the geochemical conditions tested. Uranium uptake rates follow first order kinetics over a range encompassing most environmental concentrations. Uranium uptake rates in L. stagnalis ultimately demonstrate saturation uptake kinetics when exposure concentrations exceed 100 nM, suggesting uptake via a finite number of carriers or ion channels. The lack of a relationship between U uptake rate constants and Ca uptake rates suggest that U does not exclusively use Ca membrane transporters. In general, U bioavailability decreases with increasing pH, increasing Ca and Mg concentrations, and when DOM is present. Competing ions did not affect U uptake rates. Speciation modeling that includes formation constants for U ternary complexes reveals that the aqueous concentration of dicarbonato U species (UO2(CO3)2-2) best predicts U bioavailability to L. stagnalis, challenging the free-ion activity model postulate.
CITATION STYLE
Croteau, M. N., Fuller, C. C., Cain, D. J., Campbell, K. M., & Aiken, G. (2016). Biogeochemical Controls of Uranium Bioavailability from the Dissolved Phase in Natural Freshwaters. Environmental Science and Technology, 50(15), 8120–8127. https://doi.org/10.1021/acs.est.6b02406
Mendeley helps you to discover research relevant for your work.