Select Publications in this Area of Study
Microbial geochemistry is useful for determining microbe:water:rock interactions in aqueous environments. I use geochemical data, with working knowledge of microbial metabolic redox transformations of metals and organic compounds, to make determinations about bioremediation potential in aquifers as well as bioclogging during biostimulation. Much of my research in this area focuses on how microbial surfaces and metabolic processes impact mineral equilibria. These studies are often helpful in modeling the evolution of porosity in a sediment or rock due to preferential dissolution or microbially-driven cementation. Microbial-redox transformations can also result in precipitation or dissolution of iron or manganese phases.
My research program includes microbial geochemical investigation related to the characterization of the deep, saline, Arbuckle Aquifer located in the central United States, which is targeted for CO2injection and storage. My research in this area is collaborative and funded by the Department of Energy. In field study, distinct geochemical signatures and microbial communities found in the Arbuckle Aquifer were determined to signify isolated geologic units, despite heterogeneity and thinning of seal units between the Mississippi Lime and underlying aquifer. Subsequent laboratory experimentation was performed on these same units at reservoir temperatures and pressures.
These studies demonstrated a 6-11% decrease in aquifer porosity upon reaction with supercritical CO2, while the reservoir seals were not significantly impacted (Jackson, 2015). We determined that aquifer carbonate mineralogy and geochemistry-controlled solubility caused small changes in the abundance of more soluble phases, making this the diagnostic factor in porosity enhancement. Research performed by my MS students to characterize the fluid geochemistry and microbial ecology of the Arbuckle Aquifer also demonstrated unequivocal hydraulic disconnection between reservoirs and seals, which is critical for EPA support of pilot-scale CO2injection (Scheffer, 2013). Together, these experiments provide useful data that improves predictive models for subsurface CO2injection and storage.
My research has also focused on the hydraulic connectivity of freshwater aquifers, and I have previously lent my expertise in microbial growth and experimental design to a number of studies that demonstrated that microbial clogging of porous media (e.g. Schillig et al., 2010; 2011; McGlashan et al., 2011; Devlin et al., 2011) and subsequent flow diversion decrease the efficiency of in situ bioremediation of organic contaminants. I have additionally contributed expertise to studies of how redox geochemistry impacts microbial biotransformation of hydrocarbons (Bennett et al., 2000; 2001; Rogers and Bennett, 2004) and chlorinated solvents (Sturm and Roberts, 2016; unpublished report for US Army Corps). I welcome future collaborations in the area of microbial geochemistry and hydrochemistry.