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TitleEvaluating microbial carbon sources in Athabasca oil sands tailings ponds using natural abundance stable and radiocarbon isotopes
AuthorAhad, J M E; Pakdel, K
SourceAmerican Geophysical Union (AGU) Fall Meeting 2013, abstracts; B42A-03, 2013 p. 1
Year2013
Alt SeriesEarth Sciences Sector, Contribution Series 20140137
PublisherAmerican Geophysical Union
MeetingAmerican Geophysical Union (AGU) Fall 2013 Meeting; San Francisco; US; December 9-13, 2013
Documentbook
Lang.English
Mediaon-line; digital
File formathtml
Subjectsgeochronology; carbon; carbon isotopes; carbon ratios; carbon-14 dates; Athabasca oil sands
ProgramCoal & Oil Resources Environmental Sustainability, Environmental Geoscience
LinksOnline - En ligne
AbstractNatural abundance stable (delta13C) and radiocarbon (Delta14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate the carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. The absence of algal-specific PLFAs at three of the four sites investigated, in conjunction with delta13C signatures for PLFAs that were generally within ~30/00 of that reported for oil sands bitumen (~ -300/00), indicated that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. The Delta14C values of PLFAs ranged from -906 to -5860/00 and pointed to a significant uptake of fossil carbon (up to ~90% of microbial carbon derived from petroleum), particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively higher levels of 14C in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population (~50-80% of microbial carbon derived from petroleum). Since the main carbon pools in tailings sediment were essentially 'radiocarbon dead' (i.e., no detectable 14C), the principal source for this modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by recalcitrant petroleum constituents has important implications for remediation strategies. On the one hand, it implies that mining-related organic contaminants could persist in the environment long after tailings pond reclamation has begun. Alternatively, it may be that the young, labile organic matter provided by the Athabasca River plays an important role in stimulating or supporting the microbial utilization of petroleum carbon in oil sands tailings ponds via co-metabolism or priming processes. Further research needs to examine the role which priming processes play in controlling the fate of organic contaminants in Athabasca oil sands tailings ponds, such as understanding to what extent the addition of labile material may hinder or enhance microbial uptake of fossil carbon. This knowledge can be subsequently used to optimize conditions which favour natural attenuation processes in reclamation sites following mine closure.
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.
GEOSCAN ID294861