Short-term effects of CO leakage on the soil bacterial community in a simulated gas leakage scenario.

The technology of carbon dioxide (CO) capture and storage (CCS) has provided a new option for mitigating global anthropogenic emissions with unique advantages. However, the potential risk of gas leakage from CO sequestration and utilization processes has attracted considerable attention. Moreover, leakage might threaten soil ecosystems and thus cannot be ignored. In this study, a simulation experiment of leakage from CO geological storage was designed to investigate the short-term effects of different CO leakage concentration (from 400 g m day to 2,000 g m day) on soil bacterial communities. A shunt device and adjustable flow meter were used to control the amount of CO injected into the soil. Comparisons were made between soil physicochemical properties, soil enzyme activities, and microbial community diversity before and after injecting different CO concentrations. Increasing CO concentration decreased the soil pH, and the largest variation ranged from 8.15 to 7.29 ( < 0.05). Nitrate nitrogen content varied from 1.01 to 4.03 mg/Kg, while Olsen-phosphorus and total phosphorus demonstrated less regular downtrends. The fluorescein diacetate (FDA) hydrolytic enzyme activity was inhibited by the increasing CO flux, with the average content varying from 22.69 to 11.25 mg/(Kg h) ( < 0.05). However, the increasing activity amplitude of the polyphenol oxidase enzyme approached 230%, while the urease activity presented a similar rising trend. Alpha diversity results showed that the Shannon index decreased from 7.66 ± 0.13 to 5.23 ± 0.35 as the soil CO concentration increased. The dominant phylum in the soil samples was , whose proportion rose rapidly from 28.85% to 67.93%. In addition, the proportion of decreased from 19.64% to 9.29% ( < 0.01). Moreover, the abundances of genera , , and increased, while , and decreased. Canonical correlation analysis results suggested that there was a correlation between the abundance variation of , , and the increasing nitrate nitrogen, urease and polyphenol oxidase enzyme activities, as well as the decreasing FDA hydrolytic enzyme activity, Olsen-phosphorus and total phosphorus contents. These results might be useful for evaluating the risk of potential CO leakages on soil ecosystems.