Impacts of NO 2 Impurities on the Indigenous Microbial Community Structure and Diversity in CO 2 -Saline-Sandstone Interaction System

Laboratory experiments (150 days) were performed to analyze the influence of NO 2 impurities on indigenous microbial communities and diversity with 16S rRNA sequence at real GCS site (Geological CO 2 Sequestration, ordos, China) conditions (pressure: 15 MPa, temperature: 55 °C). The possible impact of metabolic activity on the GCS process was investigated through the BLASTn search. Compared with the pure CO 2 , results demonstrate that the biomass and biodiversity were lower, due to the lower pH, within 60 days after the co-injection of 0.1% NO 2 . Subsequently, the pH was quickly buffered through the corrosion of feldspar and clay, and the impact of NO 2 had almost no obvious effect on the microbial structure except the abundance of phylum and genus after 90 days. In addition, acid-producing bacteria appeared after 60 days, such as Bacillus , Acinetobacter, and Lactococcus , etc., lower the pH in the solution and accelerate the dissolution of minerals. The Fe (III)-reducing microbes Citrobacter freundii reduce the Fe (III) released from minerals to Fe (II) and induce siderite (FeCO 3 ) biomineralization through biogeochemical processes. Therefore, the co-injection of trace NO 2 will not significantly affect the growth of microorganisms on long timescale.