Effects of high soil CO2 concentrations on seed germination and soil microbial activities

To ensure the safety of carbon capture and storage (CCS) technology, we assessed the impacts of potential CO2 leakage on the soil and ecosystem by performing laboratory experiments. In particular, we investigated the effects of high soil CO2 concentration on germination rates of four different plant species and soil physicochemical/microbial parameters. Cabbage, corn, bean, and wheat were exposed to different soil CO2 concentrations (LOW: 3.5%, MEDIUM: 12.0%, HIGH: 29.4%, EXTREME: 52.9%). Soil pH and O2 concentration decreased sharply immediately after the gases were injected. Final germination rates were not affected by LOW CO2 treatment, but the germination of cabbage, corn, and bean was delayed. Germination of all plants was retarded by MEDIUM CO2 treatment. No seeds were germinated when exposed to HIGH or EXTREME CO2. The contents of soil total C, total N, and soil microbial activities were not affected by CO2 injection. Our results suggest that a soil CO2 concentration of 3-4% does not inhibit germination. Wheat was the most resistant plant of those exposed to high CO2 concentrations. Soil microbial parameters were tolerant to short-term CO2 injection. We conclude that CO2 leakage with high concentration (>30%) can have a severe effect on seed germination, but soil microbial activity was not affected by short-term exposure.