Abstract
226Ra is radioactive nuclide (half life of 1600 year) released to the environment via uranium mining and water pumping from deep thermal groundwater. Because of positive correlations between 226Ra and salt concentrations in groundwater, inhibition effects of salts on 226Ra sorption have been suggested. Clay minerals are ubiquitous geological minerals with high cation exchange capacity (CEC) and specific surface area. They are expected to regulate 226Ra concentration in groundwater as a function of salt concentrations. However, 226Ra sorption mechanisms by clay minerals are not simple ion-exchange, making 226Ra behavior in groundwater difficult to evaluate. In this context, we investigated the mechanisms of salt concentrations to affect sorbed amount of 226Ra by clay minerals. The effects of clay contents and their types on the salt concentration dependency were also discussed.
