title: Thermodynamic and Kinetic Response of Microbial Reactions to High CO2.
abstract: Geological carbon sequestration captures CO2from industrial sources and stores the CO2in subsurface reservoirs, a viable strategy for mitigating global climate change. In assessing the environmental impact of the strategy, a key question is how microbial reactions respond to the elevated CO2concentration. This study uses biogeochemical modeling to explore the influence of CO2on the thermodynamics and kinetics of common microbial reactions in subsurface environments, including syntrophic oxidation, iron reduction, sulfate reduction, and methanogenesis. The results show that increasing CO2levels decreases groundwater pH and modulates chemical speciation of weak acids in groundwater, which in turn affect microbial reactions in different ways and to different extents. Specifically, a thermodynamic analysis shows that increasing CO2partial pressure lowers the energy available from syntrophic oxidation and acetoclastic methanogenesis, but raises the available energy of microbial iron reduction, hydrogenotrophic sulfate reduction and methanogenesis. Kinetic modeling suggests that high CO2has the potential of inhibiting microbial sulfate reduction while promoting iron reduction. These results are consistent with the observations of previous laboratory and field studies, and highlight the complexity in microbiological responses to elevated CO2abundance, and the potential power of biogeochemical modeling in evaluating and quantifying these responses.
authors.affiliation: Department of Earth Sciences, University of Oregon Eugene, OR, USA.
authors.forename: Qusheng
authors.initials: Q
authors.lastname: Jin
authors.affiliation: Department of Geology, Kansas State University Manhattan, KS, USA.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Kirk
keywords: available energy; biogeochemical modeling; carbon sequestration; iron reduction; microbial kinetics; sulfate reduction