Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6335102 | Applied Geochemistry | 2014 | 7 Pages |
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)30(aq) or the negative CaUO2(CO3)32â. 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.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Ann Catrine Norrström, Ã
sa Löv,