| Anaerobic aquifer environments have a large potential to be adversely impacted by anthropogenic contamination. Two major sources of ground water contamination are leaking underground gasoline storage tanks and leachate produced in landfills. Thus, it is imperative to determine the metabolic fate of gasoline and refuse once placed under anaerobic conditions.;However, in many instances, mineralization of these substrates does not occur. One parameter that is critically important in anaerobic fermentations is hydrogen. The relationship between hydrogen and methanogenesis was investigated in 42 samples taken from two landfills. Samples with H;To that end, the anaerobic biodegradation of alkanes and oxygenates was evaluated under methanogenic, sulfate-, and nitrate-reducing conditions in landfill leachate-contaminated aquifer slurries. There was little or no evidence for alkane degradation under any of the conditions tested. The biodegradation of the oxygenates was found to be dependent on the degree of branching in the molecular structure of the substrate. The unbranched compounds, except the ethers, were readily degraded under all redox conditions tested while the highly branched oxygenates degraded slowly or not at all. These same trends were evident when samples from other chronically contaminated environments were similarly assayed for anaerobic oxygenate biodegradation. Under all conditions tested, the ethers generally proved recalcitrant. The anaerobic metabolic fate of the oxygenates was unknown prior to this study. In contrast, refuse is largely composed of material known to be readily degradable. |
