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

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<P><B>Abstract</B></P> <P>Atmospheric carbon dioxide (CO<SUB>2</SUB>) concentrations is continuing to increase due to anthropogenic activity, and geological CO<SUB>2</SUB> storage via carbon capture and storage (CCS) technology can be an effective way to mitigate global warming due to CO<SUB>2</SUB> emission. However, the possibility of CO<SUB>2</SUB> leakage from reservoirs and pipelines exists, and such leakage could negatively affect organisms in the soil environment. Therefore, to determine the impacts of geological CO<SUB>2</SUB> leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO<SUB>2</SUB>. Cabbage, which has been reported to be vulnerable to high soil CO<SUB>2</SUB>, was grown under BI (no injection), NI (99.99% N<SUB>2</SUB> injection), and CI (99.99% CO<SUB>2</SUB> injection). Mean soil CO<SUB>2</SUB> concentration for CI was 66.8–76.9% and the mean O<SUB>2</SUB> concentrations in NI and CI were 6.6–12.7%, which could be observed in the CO<SUB>2</SUB> leaked soil from the pipelines connected to the CCS sites. The soil N<SUB>2</SUB>O emission was increased by 286% in the CI, where NO<SUB>3</SUB> <SUP>−</SUP>-N concentration was 160% higher compared to that in the control. This indicates that higher N<SUB>2</SUB>O emission from CO<SUB>2</SUB> leakage could be due to enhanced nitrification process. Higher NO<SUB>3</SUB> <SUP>−</SUP>-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 N<SUB>2</SUB>O emission could be increased by the secondary effects of CO<SUB>2</SUB> leakage on plant metabolism. Hence, monitoring the environmental changes in rhizosphere would be very useful for impact assessment of CCS technology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High soil CO<SUB>2</SUB> concentration inhibited plant growth, resulting in lower uptake of soil mineral N. </LI> <LI> Accumulation of soil mineral N by stunted plant under high soil CO<SUB>2</SUB> increased the N<SUB>2</SUB>O emission. </LI> <LI> Monitoring the changes in N<SUB>2</SUB>O emission could be utilized for detection of CO<SUB>2</SUB> leakage in the CCS sites. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>