Effect of potential CO2 leakage from carbon capture and storage sites on soil and leachate chemistry

Potential leakages from a carbon capture and storage (CCS) site can have an impact on the unsaturated zone of groundwater, which may affect the saturated zone through leaching. Therefore, the effect of possible CO2 leakage on soil and leachate chemistry were investigated by conducting a leaching experiment from soils that were exposed to 100% CO2 for 32 days. The leaching was conducted by arranging CO2 treated mineral and organic soils into two layers in a custom made column. The leachates collected from the leaching were analyzed for pH, base cations and Dissolved Organic Carbon (DOC). Prior to that, the CO2 treated soils were analyzed for pH, DOC, CEC, exchangeable acidity and Al3+. The CO2 treatment significantly reduced the pH of the organic soil, mineral soil and leachates. After CO2 treatment, the DOC significantly increased in organic soil, while it decreased in the mineral soil. DOC and base cations significantly increased in the leachates. CEC did not change in the CO2 treated soils, but significant increases in exchangeable acidity and Al3+ were observed in the CO2 treated mineral soil. The results of this study showed that high soil CO2 can affect the soil chemistry, which can further affect the groundwater chemistry through leaching.