Methanogenesis in freshwater sediments: inherent variability and effects of environmental contaminants.

Temporal and spatial variability of methanogenesis and the effects of environmental contamination on methanogenesis were examined in freshwater sediments. Temporal and spatial variation was found to be significant in uncontaminated freshwater reservoir sediments. The relative concentration of organic matter and temperature explained approximately 43% of the total variability. Known environmental contaminants marginally inhibited methanogenesis and only a coal conversion effluent and phenanthrene, 100 mg L-1, demonstrated statistically significant inhibition of methanogenesis under acute dosing conditions. Methyl viologen, a potent inhibitor of pure culture methanogenesis, inhibited sediment methanogenesis at high concentrations, i.e., 2570 mg L-1, indicating that the sediment environment protected the methanogenic population from the toxic effects of the environmental contaminants.