Impacts Of NO₂ Impurity On The Interacton Systerm Of Microbially Mediated CO₂-Saline-Rock

Global warming has become prominent due to the increase of CO₂ in atmosphere because of the fossil combustion.However,CO₂ capture and storage in deep saline aquifer is considered as one of the potential technologies for the reduction of CO₂emission due to its large storage space and high safety.The CO_2,captured from heavy oil processing or power plants with post-combustion capture,usually contains a certain amount of NO_x.The acidity and oxidative of NO_x will inevitably affect the biogeochemistry in GCS.So,the actual site of CO₂ saline aquifer storage established in the Ordos Basin of China was taken as the research object,and the impact of 0.1%NO₂ impurity on microbially mediated CO₂-salt-sandstone interaction was carried in high-pressure reactors at 55°C,15 Mpa for 150 days.Firstly,the impact of NO₂ on the microbial community was studied with the technology of 16S rRNA and qPCR.The results of simulation experiment in the high pressure reactor showed:?1?After the co-injection of 0.1%NO₂,the biomass and biodiversity were lower than that after only CO₂ injection due to the lower pH in the early stage.However,the pH could be quickly buffered through the corrosion of feldspar and clay,and the impact of NO₂ on pH was not obvious in the middle and later stage.NO₂ co-injection increased the concentrations of NO₃^-and Fe³⁺,which could be used as electron acceptors to enhance biological metabolism,and the biomass and biodiversity increased and were gradually greater than that after only CO₂ injection in the later stage.?2?The changes of pH,NO₃^-and Fe³⁺after co-injection of 0.1%NO₂ almost had no effect on the microbial classification but abundance of phylum and genus.Proteobacteria and Firmicutes were the dominant phylum.In the early stage,there were the acid-tolerant and salt-tolerant bacteria of Burkholderia,Sphingomonas,Brevundimonas,Caulobacter and Stenotrophomonas as the dominant genus.In the medium term,there were the acid-producing bacteria of Bacillus and Lactococcus,and salt-tolerant bacteria of Oceanobacillus as the dominant genus.In the later stage,there were the iron-reducing bacteria of Citrobacter,acid-producing bacteria of Exiguobacterium,Acinetobacter,and acid-resistant denitrifying bacteria of Pseudomonas as the dominant genus.But,the abundance of Burkholderia after NO₂co-injection was higher than that after only CO₂ injection in the early stage,the abundance of Citrobacter and Pseudomonas after NO₂ co-injection was higher than that after only CO₂ injection in the later stage.Secondly,the impact of co-injection of 0.1%NO₂ on biogeochemistry was studied.The results of simulation experiment in the high pressure reactor showed:?1?0.1%NO₂ co-injection promoted the corrosion of feldspar and clay,and the pH could be buffered in a short period.The concentrations of Ca²⁺,Fe²⁺and Mg²⁺in saline were higher than that after only CO₂ injection,which was helpful for carbonates trapping in the later time when pH was buffered.?2?The acid-producing bacteria induced by 0.1%NO₂ co-injection further promoted the corrosion of feldspar and clay,and increased the concentrations of Ca²⁺,Fe²⁺and Mg²⁺.The higher concentrations of T-Fe and NO₃^-enhanced the activity of denitrification and iron-reducing bacteria.And with the function of adsorption and mineralization by biofilm,the secondary ankerite and calcite were preferentially generated in the CO₂-NO₂-microbes group on the 150^th days.The results showed that a small amount of NO₂ co-injection had feasibility in the GCS technology.And it was beneficial to the microbial growth in the later stage and the preferential generation of carbonates in biogeochemistry.It would also be beneficial to reduce the cost of CO₂ purification and weaken the NO_x pollution to atmosphere.