Increased N2O emission by inhibited plant growth in the CO2 leaked soil environment: Simulation of CO2 leakage from carbon capture and storage (CCS) site

Atmospheric carbon dioxide (CO2) concentrations is continuing to increase due to anthropogenic activity, and geological CO2 storage via carbon capture and storage (CCS) technology can be an effective way to mitigate global warming due to CO2 emission. However, the possibility of CO2 leakage from reservoirs and pipelines exists, and such leakage could negatively affect organisms in the soil environment. Therefore, to determine the impacts of geological CO2 leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO2. Cabbage, which has been reported to be vulnerable to high soil CO2, was grown under BI (no injection), NI (99.99% N2 injection), and CI (99.99% CO2 injection). Mean soil CO2 concentration for CI was 66.8–76.9% and the mean O2 concentrations in NI and CI were 6.6–12.7%, which could be observed in the CO2 leaked soil from the pipelines connected to the CCS sites. The soil N2O emission was increased by 286% in the CI, where NO3−-N concentration was 160% higher compared to that in the control. This indicates that higher N2O emission from CO2 leakage could be due to enhanced nitrification process. Higher NO3−-N content in soil was related to inhibited plant metabolism. In the CI treatment, chlorophyll content decreased and chlorosis appeared after 8th day of injection. Due to the inhibited root growth, leaf water and nitrogen contents were consistently lowered by 15% under CI treatment. Our results imply that N2O emission could be increased by the secondary effects of CO2 leakage on plant metabolism. Hence, monitoring the environmental changes in rhizosphere would be very useful for impact assessment of CCS technology. [Display omitted] •High soil CO2 concentration inhibited plant growth, resulting in lower uptake of soil mineral N.•Accumulation of soil mineral N by stunted plant under high soil CO2 increased the N2O emission.•Monitoring the changes in N2O emission could be utilized for detection of CO2 leakage in the CCS sites.