Effects of Simulated CO ₂ Leakage on Soil Microbial Communities in a Greenhouse Experiment

Carbon capture and storage (CCS) is a key technology for mitigating global climate change, yet the environmental risks of potential CO 2 leakage from storage sites require thorough evaluation. The short‐term impacts of simulated CO 2 leakage on soil microbial communities in a controlled greenhouse experiment was investigated in this study. High‐purity CO 2 was injected at 100 mL min −1 for 30 days into mesocosms planted with maize ( Zea mays ). The CO 2 injection significantly increased soil CO 2 concentrations (mean 20.3% at 5 cm, 42.9% at 15 cm) and depleted O 2 concentrations. Elevated soil CO 2 inhibited plant growth and nutrient uptake, leading to a significant accumulation of inorganic nitrogen (ammonium and nitrate) in the soils. This nutrient shift corresponded with a significant decrease in N ‐acetyl‐glucosaminidase activity, an enzyme mediating microbial nitrogen acquisition. Although bacterial alpha diversity (richness and evenness) remained unchanged, the community composition was significantly altered. The relative abundance of Proteobacteria decreased, whereas that of Saccharibacteria_TM7 increased in CO 2 ‐injected soils. Furthermore, the abundance of important nitrogen‐fixing families, including Bradyrhizobiaceae and Phyllobacteriaceae, was significantly reduced. These findings indicate that short‐term CO 2 leakage indirectly alters soil microbial communities by inhibiting plant growth, which subsequently changes soil nutrient availability. Monitoring these plant–microbe interactions is therefore important for the environmental assessment of CCS sites.