Biogeochemical controls of uranium bioavailability from the dissolved phase in natural freshwaters

Environmental Science & Technology
By: , and 

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Abstract

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 speciesLymnaea 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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Biogeochemical controls of uranium bioavailability from the dissolved phase in natural freshwaters
Series title Environmental Science & Technology
DOI 10.1021/acs.est.6b02406
Volume 50
Issue 15
Year Published 2016
Language English
Publisher ACS Publications
Contributing office(s) Toxic Substances Hydrology Program, Colorado Water Science Center, National Research Program - Central Branch, National Research Program - Western Branch
Description 8 p.
First page 8120
Last page 8127
Online Only (Y/N) N
Additional Online Files (Y/N) N