This mechanism accounts for the existence of many ore bodies. Addition of alum and softening chemicals in drinking water treatment plants similarly precipitates radium with the other minerals. Oxidation-reduction potential can affect solubility. Variation in oxidation state affects solubility since complex formation depends strongly on oxidation state. For example, water exposed to sulfur-bearing minerals generally exhibits reducing potential, which may alter the oxidation state of other minerals in contact with the water.
Adsorption depends on the substrate and the specific species in question.
Adsorption of radon on activated charcoal is an equilibrium process. Ion exchange is used to control water chemistry, typically to remove contaminants, soften potable water, or remove radium. Ion exchange does not cause mobilization of radionuclides, but once mobilized in water, any subsequent treatment by ion exchange has clear potential for reconcentration. Temperature-dependent variations in solubility result in increased concentrations of radionuclides, together with other elements in geothermal waters. Thermal processes can mobilize radionuclides.