Microbial Activity in Ground Water at a Chemical Waste Disposal Site
Armstrong, Anthony Q.
Lewis, David L.
Hodson, Robert E.
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Selected ground water microbial processes were monitored in wells upslope and downslope from a research chemical waste disposal site on the campus of the University of Georgia. Burial of waste at the site was discontinued by the middle of the 1970's. Recently, it was determined that ground water at the site contained elevated levels of potentially toxic pollutants such as iron, manganese, benzene, methylene chloride, toluene, and xylene. Indices of microbial activity (e.g., uptake and mineralization of D-glucose) showed activity to be inhibited 2 to 5 fold in contaminated ground water relative to upslope control. Population switching experiments revealed no enhanced tolerance to the pollutant mixture of bacteria in the contaminated wells relative to control populations. However, rates of degradation of toluene, a compound of the pollutant mixture, were >20 fold higher in contaminated ground water than in control ground water, suggesting adaptation for enhanced degradation for a specific pollutant. Kinetics of toluene degradation by the microbial populations in the contaminated wells were multiphasic with the kinetic parameters K and V[max] varying widely with substrate concentration. Such kinetic diversity has not been demonstrated previously for pollutant degradation in subsurface waters and has significant implications for modeling pollutant persistence and exposure.