Geochemical modeling of changes in shallow groundwater chemistry observed during the MSU-ZERT CO2 injection experiment

► Because the possibility of CO2 leakage cannot be completely ruled out, the potential impact of CO2 intrusion on the quality of fresh water aquifers overlying CO2 storage sites needs to be investigated. ► Geochemical data from a field experiment involving the release of carbon dioxide (CO2) into a shallow aquifer were evaluated. ► Geochemical model used to assess possible geochemical processes responsible for the observed increases in the concentrations of dissolved constituents. ► Reasonable agreement between observed and modeled data suggests that increases in the concentrations of most major and trace metal cations except Fe could be a result of Ca+2-driven exchange reactions and the release of anions from adsorption sites due to competitive adsorption of carbonate could explain the observed trends of most anions.