Dominant Terminal Electron Accepting Processes Occurring at a Landfill Leachate-Impacted Site as Indicated by Field and Laboratory Measures

By Steve H. Harris, Glenn A. Ulrich, and Joseph M. Suflita

ABSTRACT

We used soluble and solid phase geochemical profiles as well as microbiological rate experiments to evaluate the dominant terminal electron accepting processes occurring in an aquifer polluted by leachate from the closed municipal landfill in Norman, OK. Sulfate reduction and methanogenesis were identified as dominant processes influencing the biodegradation of aquifer contaminants. Interestingly, both of these processes were governed, at least in part, by the ambient concentration of sulfate. Consequently, the supply of sulfate in the aquifer was a major determinant governing the biodegradation of contaminant materials. We were able to determine that the supply of this electron acceptor was a function of several processes including the oxidation of iron sulfides near the water table, the advective flux of sulfate from background subsurface locations, and the dissolution of barite minerals.