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TitleIn situ biodegradation of naphthenic acids in groundwater near oil sands tailings ponds
AuthorAhad, J M E; Pakdel, H; Gammon, P R; Siddique, T; Kuznetsova, A; Savard, M M
SourceSETAC (Society of Environmental Toxicology and Chemistry) North American 38th Annual Meeting, 12-16 November, Minneapolis, MN, USA, abstract volume; 2017, 1 pages
Year2017
Alt SeriesNatural Resources Canada, Contribution Series 20170317
PublisherSETAC
MeetingSETAC (Society of Environmental Toxicology and Chemistry) North American 38th Annual Meeting; Minneapolis, MN; US; 12-16 November, 2017
Documentbook
Lang.English
Mediapaper; on-line; digital
File formatpdf
Subjectshydrogeology; Health and Safety; oil sands; bituminous sands; aromatic hydrocarbons; hydrocarbons; tailings; tailings geochemistry; tailings analyses; groundwater geochemistry; groundwater pollution; pollutants; pollution; biodegradation; cyclohexanedicarboxylic acid; 1-adamantanecarboxylic acid); Dechloromonas aromatic; Betaproteobacteria
ProgramSources, Environmental Geoscience
LinksOnline - En ligne (full, complet)
AbstractPotential seepage of naphthenic acids (NAs) from tailings ponds into surface water and groundwater is one of the main environmental concerns associated with oil sands mining operations. While a growing number of studies have demonstrated the microbial breakdown of NAs under both aerobic and anaerobic conditions in controlled laboratory experiments, the direct verification of in situ biodegradation of NAs in impacted groundwater remains a challenge. Here we report the application of 13C-labelled NA surrogate compounds to evaluate intrinsic biodegradation of NAs along two separate groundwater flow-paths originating from two different major oil sands tailings ponds. Microcosms containing the labelled NA surrogates (cyclohexanecarboxylic acid, 1,2- cyclohexanedicarboxylic acid and 1-adamantanecarboxylic acid) were lowered into monitoring wells for several months to allow sufficient time for substrate degradation and formation of a biofilm in conditions characteristic of the local aquifer. The subsequent determination of highly 13C-enriched carbon isotope (delta-13C) values in phospholipid fatty acids (PLFAs) - biomarkers for the active microbial population - confirmed the microbial breakdown of NAs in the subsurface. Along one groundwater flow-path, where the drive-point well containing the microcosm was situated in an area dominated by muskeg, microbial community analysis revealed a large component of Dechloromonas aromatic, an aromatic hydrocarbon-degrading Betaproteobacteria. The in situ biodegradation of low molecular weight (n < 12) NAs demonstrates that these compounds can be readily broken down by the indigenous microbial population found in the shallow subsurface near tailings ponds. Since many low molecular weight NAs are considered some of the most harmful compounds in oil sands process-affected water (OSPW), this study has shown that a reduction in OSPW toxicity can occur in impacted groundwater prior to surface discharge.
Summary(Plain Language Summary, not published)
Potential seepage of naphthenic acids (NAs) from tailings ponds into surface water and groundwater is one of the main environmental concerns associated with oil sands mining operations. Here we report the application of 13C-labelled NA surrogate compounds to evaluate in situ biodegradation of NAs in groundwater near two different tailings ponds. Microcosms containing the labelled compounds were lowered into monitoring wells for several months to allow sufficient time for substrate degradation. The measurement of 13C-enrichment substantially above natural abundance levels of 13C in microbial biomarkers provided unequivocal evidence for in situ biodegradation of low molecular weight surrogates. In contrast, there was no such 13C-enrichment in microcosms seeded with a slightly higher molecular weight surrogate, implying certain toxic constituents may persist in the environment after seepage into groundwater.
GEOSCAN ID306390