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Factors Influencing Methane Distribution in Texas Ground Water
Author(s) -
Zhang Chuanlun,
Grossman Ethan L.,
Ammerman James W.
Publication year - 1998
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.1745-6584.1998.tb01065.x
Subject(s) - environmental science , methane , distribution (mathematics) , groundwater , mathematics , geology , ecology , biology , geotechnical engineering , mathematical analysis
To determine the factors that influence the distribution of methane in Texas ground water, water samples were collected from 40 wells in east‐central and central Texas aquifers. Among the chemical parameters examined, sulfate is most important in controlling methane distribution. Methane occurs in high concentration (>10 μM) in east‐central Texas only where sulfate concentration is low (<1 μM), supporting the hypothesis that abundant microbial methane production does not begin until sulfate is depleted. Because water samples from central Texas are high in either oxygen (up to 172 μM) or sulfate (up to 28.7 μM), methane concentrations are low (<5 μM) in these waters. A positive correlation between methane and sulfate in these waters indicates a different, perhaps thermogenic, origin for the trace methane. The 13 C/ 12 C ratios of dissolved methane ranged from ‐80%o to ‐21%o in east‐central Texas and from ‐41.2%e to ‐8.5%e in central Texas. Low values of < −50%e in the east‐central Texas ground water indicate a microbial origin for methane and are consistent with the observed sulfate‐methane relationship; high 13 C/ 12 C ratios of > −31%e likely result from bacterial methane oxidation. Similarly, methane with high 13 C/ 12 C ratios in central Texas may reflect partial oxidation of the methane pool. Overall, water samples from both regions show a positive correlation between sulfate concentration and the 13 C/ 12 C ratio of methane, suggesting that methane oxidation may be associated with sulfate reduction in Texas ground water.