Major ions, especially calcium (Ca), magnesium (Mg), potassium (K), and silicon (Si), show obvious enrichment, indicating mobilization of these ions from aquifer sediments to groundwater that may be dominated by dissolution of silicates and possibly carbonate minerals. Stable carbon isotope (¦Ä13C) of DIC of the recovered samples also suggests potential dissolution of carbonates. Whereas concentrations of trace elements were elevated after injection of CO2-enriched groundwater, their maximum concentrations remained below the EPA's maximum contamination levels (MCLs). Mobilization of trace elements could be due to dissolution of silicates and carbonates and desorption from a clay surface. Mass-balance calculations suggest that ion mobilization is limited, and, therefore, potential risks of CO2 are low, especially for arsenic and lead, which appeared in the recovered samples at concentrations of approximately 3 % of the EPA MCL. Overall reaction rates estimated from the push-pull test were generally smaller than overall reaction rates in a batch experiment. Results of the push-pull test suggest that groundwater pH, DIC, and ¦Ä13C of DIC may be helpful in detecting CO2 leakage signals. Our study indicated that single-well push-pull tests can be a valuable approach for assessing potential impacts of CO2 leakage on drinking water resources at geological CO2 sequestration sites.