Experimental Assessment of CO2-Mineral-Toxic Ion Interactions in a Simplified Freshwater Aquifer: Implications for CO2 Leakage from Deep Geological Storage
2013
Montes-Hernandez, German | Renard, François | Lafay, Romain
The possible intrusion of CO₂ into a given freshwater aquifer due to leakage from deep geological storage involves a decrease in pH, which has been directly associated with the remobilization of hazardous trace elements via mineral dissolution and/or via desorption processes. In an effort to evaluate the potential risks to potable water quality, the present study is devoted to experimental investigation of the effects of CO₂ intrusion on the mobility of toxic ions in simplified equilibrated aquifers. We demonstrate that remobilization of trace elements by CO₂ intrusion is not a universal physicochemical effect. In fact goethite and calcite, two minerals frequently found in aquifers, could successfully prevent the remobilization of adsorbed Cu(II), Cd(II), Se(IV), and As(V) if CO₂ is intruded into a drinking water aquifer. Furthermore, a decrease in pH resulting from CO₂ intrusion could reactivate the adsorption of Se(IV) and As(V) if goethite and calcite are sufficiently available in underground layers. Our results also suggest that adsorption of cadmium and copper could be promoted by calcite dissolution. These adsorbed ions on calcite are not remobilized when CO₂ is intruded into the system, but it intensifies calcite dissolution. On the other hand, arsenite As(III) is significantly adsorbed on goethite, but is partially remobilized by CO₂ intrusion.
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