Potential impacts of leakage from CO2geological storage ongeochemical processes controlling fresh groundwater quality : A review
Résumé
tLeakage of CO2or brine coming from CO2geological storage sites constitutes a risk for overlying freshgroundwater resources. One of the main risks is the potential alteration of groundwater quality by theintrusion of contaminants such as trace elements. This paper reviews studies that address the potentialimpacts of CO2geological storage leakage on fresh groundwater quality.Leakage can directly modify the chemical properties of fresh water (pH, redox potential, chemicalcomposition) and, as a result, indirectly modify the effect of biogeochemical processes controlling traceelement availability. The ability of a CO2or brine leak to introduce or mobilize trace elements and poten-tially degrade the quality of water in an overlying aquifer depends on the composition and quantityof the leaking fluids, the nature of the solid phases making up the aquifer (buffering and scavengingcapacity) and the concentrations of undesirable or toxic elements that can be mobilized following anysuch modification. Furthermore, hydrogeological conditions will control the potential dissemination intogroundwater. To date, studies have shown that trace elements can be significantly mobilized without nec-essarily exceeding quality thresholds. In a few cases where aquifers are naturally rich in trace elements(i.e. whose natural concentrations in groundwater are already high), CO2is able to mobilize these traceelements (e.g. Fe, Mn, Ni, As, Ba, U) and increase concentrations up to or exceeding threshold values.This literature review provides a return on experience essential for both assessing biogeochemicalrisks prior to the installation of future CO2geological storage sites and designing and installing freshgroundwater quality monitoring networks.