Modelling partition coefficients of radium in soils
2019
Urso, L. | Hormann, V. | Diener, A. | Achatz, M.
A thermodynamic sorption model is used to calculate partition coefficients (Kd) of radium in soils. It accounts for the dominant chemical interactions of radium with soil by assuming that non-available thermodynamic constants for radium can be replaced by those of barium. The retention processes considered include sorption on clay surfaces, on organic matter and on hydrous ferric oxide as well as the co-precipitation of radium with barium. The modelled Kd values are compared to experimental Kd values available in the relevant literature. The results show that the experimental Kd values are within a factor of 2–3. The model is also applied to two representative German soil types. The calculated Kd values agree with the finding that Kd values for radium are generally low. The conclusion is that radium retention can be modelled reasonably well, but that it is necessary to account for specific properties such as the ability of radium to co-precipitate with barium and competition from other alkaline earth metals for surface sites.
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