Kinetic Modeling of Microbially-Driven Redox Chemistry of Radionuclides in Subsurface Environments: Coupling Transport, Microbial Metabolism and Geochemistry;Journal of Contaminant Hydrology

摘要

Microbial degradation of organic matter is a driving force in many subsurface geochemical systems, and therefore may have significant impacts on the fate of radionuclides released into subsurface environments. In this paper, we present a general reaction-transport model for microbial metabolism, redox chemistry, and radionuclide migration in subsurface systems. The model explicitly accounts for biomass accumulation and the coupling of radionuclide redox reactions with major biogeochemical processes. Based on the consideration that the biomass accumulation in subsurface environments is likely to achieve a quasi-steady state, we have accordingly modified the traditional microbial growth kinetic equation. We justified the use of the biogeochemical models without the explicit representation of biomass accumulation, if the interest of modeling is in the net impact of microbial reactions on geochemical processes. We then applied our model to a scenario in which an oxic water flow containing both uranium and complexing organic ligands is recharged into an oxic aquifer in a carbonate formation. The model simulation shows that uranium can be reduced and therefore immobilized in the anoxic zone created by microbial degradation.