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TitleDirect evaluation of in situ biodegradation in Athabasca oil sands tailings ponds using natural abundance radiocarbon
AuthorAhad, J M EORCID logo; Pakdel, H
SourceEnvironmental Science & Technology (ES & T) vol. 47, no. 18, 2013 p. 10214-10222,
Alt SeriesEarth Sciences Sector, Contribution Series 20130051
PublisherAmerican Chemical Society (ACS)
Mediapaper; on-line; digital
File formatpdf
NTS73E; 73L; 73M; 74D; 74E; 83F; 83G; 83H; 83I; 83J; 83K; 83N; 83O; 83P; 84A; 84B; 84C; 84F; 84G; 84H
AreaAthabasca; Peace River; Cold Lake
Lat/Long WENS-118.0000 -110.0000 58.0000 53.0000
Subjectsenvironmental geology; fossil fuels; isotopes; radiocarbon dates; carbon; carbon isotopes; tailings; tailings analyses; oil pollution; pollutants; environmental analysis; environmental studies; environmental impacts; Athabaska Oil Sands; Peace River Oil Sands; Cold Lake Oil Sands
Illustrationshistograms; tables; plots
ProgramEnvironmental Geoscience Coal & Oil Resources Environmental Sustainability
Released2013 09 09
AbstractCompound-specific stable (d13C) and radiocarbon (d14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. Algal-specific PLFAs were absent at three of the four sites investigated, and d13CPLFA values were generally within ~3per-mille of that reported for oil sands bitumen ( ~-30per-mille), suggesting that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. d14CPLFA values ranged from -906 to -586per-mille and pointed to significant uptake of fossil carbon, particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively heavier d14C values found in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population. Since the main carbon pools in tailings sediment were essentially "radiocarbon dead" (i.e., d14C -1000per-mille), the principal source for this relatively modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential utilization of the minor amount of younger and presumably more labile material present in systems otherwise dominated by petroleum carbon has important implications for remediation strategies, since it implies that organic contaminants may persist long after reclamation has begun. Alternatively, this young organic matter could play a vital and necessary role in supporting the microbial utilization of fossil carbon via cometabolism or priming processes.
Summary(Plain Language Summary, not published)
Under the framework of the Earth Science Sector's Environmental Geosciences Program, this is the first study to use natural abundance 13C and 14C isotopes to evaluate microbial carbon sources in oil sands tailings ponds. We determined that a significant amount (up to ~90%) of the carbon utilized by aerobic bacteria was derived from petroleum. Young organic matter originating from the Athabasca River, the main water source used in bitumen extraction, was also an important carbon source. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by difficult-to-degrade petroleum has important implications for remediation strategies, since it implies that organic contaminants could persist long after reclamation has begun. On the other hand, it may be that this young organic matter plays an important and necessary role in supporting the microbial utilization of petroleum carbon.

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