Carbon isotope fractionation during anaerobic biodegradation of BTEX; implications for intrinsic bioremediation

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Authors:Ahad, J. M.; Sherwood Lollar, B.; Edwards, E. A.; Slater, G. F.; Sleep, B. E.
Author Affiliations:Primary:
University of Toronto, Department of Geology, Toronto, ON, Canada
Volume Title:Geological Society of America, 1999 annual meeting
Source:Abstracts with Programs - Geological Society of America, 31(7), p.216; Geological Society of America, 1999 annual meeting, Denver, CO, Oct. 25-28, 1999. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592
Publication Date:1999
Note:In English
Summary:Carbon isotope fractionation produced by anaerobic biodegradation of toluene was evaluated in laboratory experiments under both methanogenic and sulfate-reducing conditions. Toluene was chosen as a proxy for the BTEX (benzene, toluene, ethylbenzene, and meta-, para-, and ortho-xylene) group of contaminants; relatively water soluble monoaromatic hydrocarbons which comprise a significant percentage of petroleum. The methanogenic culture was a well-defined mixed consortium enriched from gasoline-contaminated aquifer sediments from Pensacola, Florida. The sulfate-reducing culture was a mixed consortium originally collected from an oil refinery site in Oklahoma chronically exposed to hydrocarbon contamination.Accuracy and reproducibility typical of GC-C-IRMS (gas chromatograph-combustion - isotope ratio mass spectrometry) is plus/minus 0.5 per mil. Within these limits, a small (∼2 per mil), but highly reproducible carbon-13 enrichment in the residual toluene at advanced stages of microbial transformation was observed in both cultures, reflecting the preferential biodegradation of isotopically light (carbon-12 containing) toluene. The maximum isotopic enrichment observed in the delta carbon-13 value of the residual toluene was +2.0 per mil and +2.4 per mil for the methanogenic and sulfate-reducing cultures, respectively. The key implication of this study is that the potential does exist to use stable carbon isotopic signatures, in conjunction with other methodologies, as a means of identifying intrinsic biodegradation at BTEX-contaminated sites. However, the relatively small isotopic effects imply that such an approach must be taken carefully. Since the magnitude of fractionation observed is the same for both terminal electron-accepting processes (TEAP), carbon isotopic fractionation effects will not provide a means to distinguish between which of these two types of microbial populations is active at a given site.
Subjects:Accuracy; Anaerobic environment; Aquifers; Aromatic hydrocarbons; Biodegradation; Bioremediation; BTEX; C-13/C-12; Carbon; Experimental studies; Gas chromatograms; Gasoline; Ground water; Hydrocarbons; Isotope fractionation; Isotope ratios; Isotopes; Mass spectra; Organic compounds; Petroleum products; Pollutants; Pollution; Remediation; Spectra; Stable isotopes; Toluene; Water pollution; Escambia County Florida; Florida; Gulf Coastal Plain; Oklahoma; Pensacola Florida; United States
Coordinates:N302600 N302600 W0871200 W0871200
Record ID:2001013168
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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