In-situ oil sands operations have been the dominant method of bitumen extraction in Canada since 2012; however, research on contaminants attributed to this method is limited in the peer-reviewed scientific literature, compared to that of open-pit mining. The Cold Lake oil sands region operates using exclusively thermal in-situ extraction techniques, raising the issue of whether oil sands activity is resulting in petroleum hydrocarbon (PHC) contamination in the absence of open-pit mines, upgraders, refineries, tailings ponds, and other bitumen processing operations. The lack of baseline contamination levels prior to oil sands development hampers debate on contamination from the oil sands industry. We address this shortcoming by using regional lake sediment cores to characterize petroleum hydrocarbons and trace their origin within the Cold Lake oil sands deposit. Petroleum hydrocarbons are hydrophobic compounds that bind to sediments, therefore persisting and accumulating in aquatic environments. This thesis examines historical levels of polycyclic aromatic hydrocarbons (PACs), petroleum biomarkers, and n-alkanes in radiometrically dated sediment cores collected from the depocenter of lakes within the Cold Lake heavy oil field. We used alkylated PACs and a suite of petroleum biomarkers to evaluate in-situ operations as potential petroleum-derived contamination sources. We predicted that similarly to open-pit mining, concentrations of PHCs in lake sediments would increase with industrial activity corresponding to proximity from in-situ operations. Like open-pit regions, alkylated PACs in Cold Lake sediments were elevated when compared to unsubstituted parent PACs and were significantly enriched in lake sediments deposited after the onset of oil sands operations. These findings imply that in-situ oil sands activity is driving the enrichment; however, diagnostic ratios and pyrogenic indices confirm a strongly pyrogenic origin in both pre-industrial and more recent sediments. When compared to a Cold Lake bitumen sample, the principal components driving PHC enrichment do not resemble bitumen. Likewise, diagnostic ratios of petroleum biomarkers and n-alkanes do not support bitumen as a significant source of hydrocarbons. PHC inputs in lake sediments are instead from terrestrial vegetation and plant waxes. These findings suggest that bitumen is not significantly contributing to petroleum hydrocarbon enrichment to lakes within the Cold Lake oil field; however, emissions from in-situ activity (natural gas burning, diesel trucks, seismic line cutting etc.) is increasingly abundant in more recent sediment.
With >80 % of Canadian bitumen reserves requiring in-situ techniques for extraction, this thesis provides the first assessment of the spatial and temporal relationship between contaminant loading and proximity to in-situ oil sands operations. Additionally, this study allows for the environmental implications of open-pit mining operations to now be compared to that of in-situ techniques.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/41155 |
| Date | 01 October 2020 |
| Creators | Smythe, Kirsten |
| Contributors | Blais, Jules |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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