Thermodynamic data dilemma

Abstract

Calculations practically are the only option to determine the uranium speciation because there is a lack of analytical techniques to analyze uranium species in natural waters. A comparison of common data sets distributed with geochemical codes shows that results differ considerable. Several important species are often not included. With respect to uranium minerals the situation is similar with differing log-k values for some minerals and not considering certain secondary uranium minerals that might be important for limiting uranium concentrations. Most problematic is the situation for data concerning ion exchange and surface complexation although such data is available in literature. Thus it can be stated that all available databases are not fit for purpose. Users of geochemical codes have to cope with the problem compiling or completing the data sets by deleting certain data and adding other. However, the difficulty is to define under which conditions thermodynamic data should be selected or deselected.