Experimental study on the effects of underground CO2 leakage on soil microbial consortia

A CO2 leakage simulation platform was constructed, and the high-throughput 16S rRNA gene sequencing technique was performed on the Illumina platform to compare the responses of soil microbial communities. In the CO2 leakage group, the content of soil organic matter increased continuously up to a high of 29.4% while electrical conductivity, pH and nitrate continuously declined, with the nitrate concentration never exceeding 85.5%. Rarefaction results showed that the Chao indexes increased by 18.40% ± 2.40% and the Shannon index increased by 6.20% ± 1.20% as the amount of CO2 leakage increased. In addition, as CO2 flux increased, the relative abundance of Bacteroidetes phylum decreased, whereas the relative abundance of Firmicutes, Acidobacteria and Chloroflexi phyla increased. Within the Bacteroidetes phylum, the Bacteroidales order decreased sharply during the period of highest CO2 flux. Beta diversity of microbial community was significantly correlated with the CO2 leakage gradient (p < 0.01). Redundancy analysis (RDA) revealed that differences in bacterial communities were significantly affected by soil properties (p < 0.01). The relative abundance of Bacteroidales demonstrated great variability, which may be used as a microbial sensitivity index to assess leakage risks on soil bacterial communities in other systems.