Löv, Åsa
- Royal Institute of Technology (KTH)
Abstract
Elevated concentrations of uranium (U) from natural sources have been measured in drinking water from private drilled wells in Sweden and many other countries world-wide. Although U is a radioactive element, radioactivity is not the main concern, but rather chemical toxicity, e. g. kidney damage. Uranium chemistry is complex and U in water has a very high tendency to form complexes with other compounds. Since speciation is crucial for the properties of U, and therefore the removal efficiency, this study determined theoretical U species in drinking water from private drilled wells using the geochemical model Visual MINTEQ. The drinking water samples used in modelling were from two datasets: (1) 76 water samples selected from a previous survey of 722 wells; and (2) samples of drinking water from 21 private wells sampled in May 2013. The results showed that neutrally charged U complexes dominated in the pH range 6.7-7.8, which is common in private drilled wells. This has important implications for removal method, since charge is an important factor for U removal efficiency. In the alkaline pH range, one of two calcium-UO2 carbonate complexes dominated and calcium (Ca) concentration proved to be a key factor determining the Ca-UO2 carbonate complex formed: the neutral Ca2UO2(CO3)(3)(0)(aq) or the negative CaUO2(CO3)(3)(2). Complexes with organic carbon (C) varied greatly in the acidic range, indicating that it is crucial to measure organic C content in the water since it is critical for the dissolved organic matter (DOM)-UO2 complex formation. Therefore before U removal method is selected, some crucial parameters for complex formation should be measured. Based on our results, such measurements should include pH, Ca, alkalinity and organic C concentration, as these determine the type of complexes formed and their charge.(C) 2014 Elsevier Ltd. All rights reserved.
Published in
Applied Geochemistry
2014, volume: 51, pages: 148-154
SLU Authors
UKÄ Subject classification
Environmental Sciences
Geochemistry
Publication identifier
- DOI: https://doi.org/10.1016/j.apgeochem.2014.10.005
Permanent link to this page (URI)
https://res.slu.se/id/publ/88269