Impacts of NO2 Impurities on the Indigenous Microbial Community Structure and Diversity in CO2-Saline-Sandstone Interaction System

Abstract

Laboratory experiments (150 days) were performed to analyze the influence of NO2 impurities on indigenous microbial communities and diversity with 16S rRNA sequence at real GCS site (Geological CO2 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 CO2, results demonstrate that the biomass and biodiversity were lower, due to the lower pH, within 60 days after the co-injection of 0.1% NO2. Subsequently, the pH was quickly buffered through the corrosion of feldspar and clay, and the impact of NO2 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 (FeCO3) biomineralization through biogeochemical processes. Therefore, the co-injection of trace NO2 will not significantly affect the growth of microorganisms on long timescale.