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Evidence for iron‐mediated anaerobic methane oxidation in a crude oil‐contaminated aquifer
Author(s) -
Amos R. T.,
Bekins B. A.,
Cozzarelli I. M.,
Voytek M. A.,
Kirshtein J. D.,
Jones E. J. P.,
Blowes D. W.
Publication year - 2012
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2012.00341.x
Subject(s) - environmental chemistry , aquifer , chemistry , anaerobic oxidation of methane , electron acceptor , redox , carbon fibers , groundwater , methanogenesis , sediment , organic matter , dissolved organic carbon , total organic carbon , methane , inorganic chemistry , geology , photochemistry , organic chemistry , paleontology , materials science , geotechnical engineering , composite number , composite material
In a methanogenic crude oil contaminated aquifer near Bemidji, Minnesota, the decrease in dissolved CH 4 concentrations along the groundwater flow path, along with the positive shift in δ 13 C CH 4 and negative shift in δ 13 C DIC , is indicative of microbially mediated CH 4 oxidation. Calculations of electron acceptor transport across the water table, through diffusion, recharge, and the entrapment and release of gas bubbles, suggest that these processes can account for at most 15% of the observed total reduced carbon oxidation, including CH 4 . In the anaerobic plume, the characteristic F e( III )‐reducing genus G eobacter was the most abundant of the microbial groups tested, and depletion of labile sediment iron is observed over time, confirming that reduced carbon oxidation coupled to iron reduction is an important process. Electron mass balance calculations suggest that organic carbon sources in the aquifer, BTEX and non‐volatile dissolved organic carbon, are insufficient to account for the loss in sediment F e( III ), implying that CH 4 oxidation may also be related to F e( III ) reduction. The results support a hypothesis of F e( III )‐mediated CH 4 oxidation in the contaminated aquifer.