Environmental consequences of potential leaks of CO2 in soil

Abstract

Carbon Capture and Storage (CCS) is expected to make a key contribution to the mitigation of climate change as a safe and effective short-term way to reduce the atmospheric emissions of CO2 produced by human activity. However, during the CCS process, there is a small possibility of leakage via pipeline transportation, through abandoned wells near the storage place or through natural pathways such as fractures and faults in the host formation. The stored gas may contain impurities that are more toxic and dangerous than pure CO2, potentially causing more serious environmental issues. Therefore, it is critical to assess the potential risks caused by CO2 leakage to ensure public acceptance of CCS as safe and reliable strategy for global warming mitigation. With 100% CO2 incubation in a pressure reactor, a direct correlation was found between the soil moisture and the uptake of CO2 during the process. Small changes in CaCl2-exchangeable metal concentration were observed after CO2 incubation, for example increases in Mg, K, Al, Cr, Mn, Fe, Pb, while there were decreases in Zn and Cd. However, the mobilised metal concentrations remained below plant tolerance levels. Further research will investigate the potential environmental consequences (on soil and plants) of leaks of impure CO2, focusing on the effects of controlled exposure to different concentrations of CO2/SO2 mixtures in a new continuous flow reactor.