Christopher C. Fuller
Daniel J. Cain
Kate M. Campbell
George R. Aiken
Marie Noele Croteau
2016
<p><span>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</span><i>Lymnaea stagnalis</i><span> (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 </span><i>L. stagnalis</i><span> 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 (UO</span><span>2</span><span>(CO</span><span>3</span><span>)</span><span>2</span><sup><span>–2</span></sup><span>) best predicts U bioavailability to </span><i>L. stagnalis</i><span>, challenging the free-ion activity model postulate.</span></p>
application/pdf
10.1021/acs.est.6b02406
en
ACS Publications
Biogeochemical controls of uranium bioavailability from the dissolved phase in natural freshwaters
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