Influence of CO2 on Water Chemistry and Bacterial Community Structure and Diversity: An Experimental Study in the Laboratory

As the second largest carbon pool, soil has a high CO₂ content, and it has an important impact on water–rock interactions and the bacterial community structure and diversity in soils. In this paper, three sets of laboratory simulation experiments under six levels of partial pressure CO₂ (pCO₂) conditions were used to analyze and study the CO₂–water–rock interactions and the bacterial community structure and diversity changes in soil under normal temperature and pressure. Results (1) The change of pCO₂ had an obvious influence on the chemical components. The dissolution of CO₂ led to the dissolution of dolomite and calcite, which increased the concentrations of HCO₃^?, Ca²⁺, and Mg²⁺ significantly. (2) The influence of pCO₂ on the bacterial community structure and diversity was different, and the bacterial community structure became more complex and diverse with the extension of the experiment time. In the experiments, Proteobacteria and Firmicutes were the main dominant phyla, and Gammaproteobacteria and Bacilli were the main dominant classes. The abundance of Bacteroidetes and Bacteroidia was significantly increased with the increasing pCO₂. (3) pH had a significant influence on the bacterial community structure during the experiments, and the influences of different chemical components, such as HCO₃^?, Ca²⁺, Mg²⁺, total dissolved solids (TDS), and K⁺, on the abundance of different bacterial species were significantly different. This work can provide a theoretical basis for the technology of bacterial–geological storage of CO₂, and it has important significance for the protection of the groundwater environment and the soil ecosystem.