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Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction
Author(s) -
Van Stempvoort Dale,
Maathuis Harm,
Jaworski Ed,
Mayer Bernhard,
Rich Kathleen
Publication year - 2005
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2005.0005.x
Subject(s) - sulfate , methane , environmental chemistry , bicarbonate , hydrogen sulfide , anaerobic oxidation of methane , sulfide , chemistry , sulfur , environmental science , geology , organic chemistry
When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature (∼5°C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34 S and 18 O. Sulfate concentrations had a strong positive correlation with δ 13 C values of bicarbonate, and sulfide was depleted in 34 S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13 C. Modeling indicates that the main source of this excess 13 C‐depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada.