Evaluating the impact that airborne contamination associated with Athabasca oil sands (AOS) mining operations has on the surrounding boreal forest ecosystem requires a rigorous approach to source ...discrimination. This study presents a century-long historical record of source apportionment of polycyclic aromatic hydrocarbons (PAHs) in dated sediments from two headwater lakes located approximately 40 and 55 km east from the main area of open pit mining activities. Concentrations of the 16 Environmental Protection Agency (EPA) priority PAHs in addition to retene, dibenzothiophene (DBT), and six alkylated groups were measured, and both PAH molecular diagnostic ratios and carbon isotopic signatures (δ13C) of individual PAHs were used to differentiate natural from anthropogenic inputs. Although concentrations of PAHs in these lakes were low and below the Canadian Council of Ministers of the Environment (CCME) guidelines, diagnostic ratios pointed to an increasingly larger input of petroleum-derived (i.e., petrogenic) PAHs over the past 30 years concomitant with δ13C values progressively shifting to the value of unprocessed AOS bitumen. This petrogenic source is attributed to the deposition of bitumen in dust particles associated with wind erosion from open pit mines.
The objective of this study was to advance analytical methods for detecting oil sands process-affected water (OSPW) seepage from mining containments and discriminating any such seepage from the ...natural bitumen background in groundwaters influenced by the Alberta McMurray formation. Improved sampling methods and quantitative analyses of two groups of monoaromatic acids were employed to analyze OSPW and bitumen-affected natural background groundwaters for source discrimination. Both groups of monoaromatic acids showed significant enrichment in OSPW, while ratios of O2/O4 containing heteroatomic ion classes of acid extractable organics (AEOs) did not exhibit diagnostic differences. Evaluating the monoaromatic acids to track a known plume of OSPW-affected groundwater confirmed their diagnostic abilities. A secondary objective was to assess anthropogenically derived artificial sweeteners and per- and polyfluoroalkyl substances (PFAS) as potential tracers for OSPW. Despite the discovery of acesulfame and PFAS in most OSPW samples, trace levels in groundwaters influenced by general anthropogenic activities preclude them as individual robust tracers. However, their inclusion with the other metrics employed in this study served to augment the tiered, weight of evidence methodology developed. This methodology was then used to confirm earlier findings of OSPW migrations into groundwater reaching the Athabasca River system adjacent to the reclaimed pond at Tar Island Dyke.
Fugitive dust associated with surface mining activities is one of the principal vectors for transport of airborne contaminants in Canada’s Athabasca oil sands region (AOSR). Effective environmental ...management requires quantitative identification of the sources of this dust. Using natural abundance radiocarbon (Δ14C) and dual (δ13C, δ2H) compound-specific isotope analysis (CSIA), this study investigated the sources of dust and particulate-bound polycyclic aromatic compounds (PACs) deposited in AOSR lake snowpack. Lower Δ14C values, higher particulate and PAC loadings, and lower δ13C values for phenanthrene and C1-alkylated phenanthrenes/anthracenes (C1-Phen) at sites closer to the mining operations indicated unprocessed oil sand and/or petroleum coke (petcoke–a byproduct of bitumen upgrading) as major sources of anthropogenic fugitive dust. However, a Bayesian isotopic mixing model that incorporated both δ13C and δ2H could discriminate petcoke from oil sand, and determined that petcoke comprised between 44 and 95% (95% credibility intervals) of a C1-Phen isomer at lakes <25 km from the heart of the mining operations, making it by far the most abundant source. This study is the first to demonstrate the potential of CSIA to provide accurate PAC source apportionment in snowpack and reveals that petcoke rather than oil sand is the main source of mining-related particulate PACs deposited directly to AOSR lakes.
Some of the parental material for hydrocarbons produced from low-permeability reservoirs in Western Canada corresponds to thermal products from biodegraded oil. This has been proved by the occurrence ...of framboidal pyrite, which is often formed during microbial sulfate reduction (MSR). In addition, the identified pyrite framboids are associated with the presence of phosphorus (P). Phosphorus (as phosphate) is a key nutrient and energy carrier for sulfate-reducing bacteria. The pyrite-P assemblage occurs embedded in solid bitumen (thermal residue), which confirms that migrated hydrocarbons provided the environment for microbial growth. Molecular products of severe biodegradation such as 17-nortricyclic terpanes were also detected. Biodegradation effects have been masked not only by thermal degradation of biodegraded oil during maximum burial, but also due to hydrocarbon mixing with late gas-condensate charges. Suitable conditions for biodegradation (< 80 °C, basin uplift) occurred during the Early Cretaceous. The confirmation of paleo-biodegradation means that there was a significant hydrocarbon loss that we have not accounted for. Likewise, MSR and Early Cretaceous seawater sulfate might have played an important role in the generation of the hydrogen sulfide (H
S) detected today.
Distinguishing between naphthenic acids (NAs) associated with oil sands process-affected water (OSPW) and those found naturally in groundwaters in contact with the bituminous McMurray Formation poses ...a considerable analytical challenge to environmental research in Canada’s oil sands region. Previous work addressing this problem combined high-resolution Orbitrap mass spectrometry with carbon isotope values generated by online pyrolysis (δ13Cpyr) to characterize and quantify the acid extractable organics (AEOs) fraction containing NAs in the subsurface near an oil sands tailings pond. Here, we build upon this work through further development and application of these techniques at two different study sites near two different tailings ponds, in conjunction with the use of an additional isotopic toolsulfur isotope analysis (δ34S) of AEOs. The combined use of both δ13Cpyr and δ34S allowed for discrimination of AEOs into the three end-members relevant to ascertaining the NA environmental footprint within the region: (1) OSPW; (2) McMurray Formation groundwater (i.e., naturally occurring bitumen), and; (3) naturally occurring non-bitumen. A Bayesian isotopic mixing model was used to determine the relative proportions of these three sources in groundwater at both study sites. Although background levels of OSPW-derived AEOs were generally low, one sample containing 49–99% (95% credibility interval) OSPW-derived AEOs was detected within an inferred preferential flow-path, highlighting the potential for this technique to track tailings pond seepage.
The downstream accumulation of polycyclic aromatic hydrocarbons (PAHs) in the Peace-Athabasca Delta (PAD), an ecologically important landscape, is a key issue of concern given the rapid development ...of the oil sands industry in Northern Alberta, Canada. In addition to PAHs derived from industrial activity (i.e., oil sands mining) within the Athabasca watershed, however, forest fires and erosion of fossil fuel deposits within both the Athabasca and Peace watersheds are two potentially important natural sources of PAHs delivered to the PAD. Consequently, evaluating the environmental impact of mining activities requires a quantitative understanding of natural, background PAHs. Here, we utilize molecular-level natural-abundance radiocarbon measurements on an amalgamated sediment record from a Peace River flood-susceptible oxbow lake in the northern Peace sector of the PAD to quantitatively discriminate sources of naturally occurring alkylated PAHs (fossil and modern biomass). A radiocarbon mass balance quantified a predominantly natural petrogenic source (93% petrogenic, 7% forest fire) for alkylated PAHs during the past ∼50 years. Additionally, a significant petrogenic component determined for retene, a compound usually considered a biomarker for softwood combustion, suggests that its use as a unique forest fire indicator may not be suitable in PAD sediments receiving Peace watershed-derived fluvial inputs.
Surface oil sands mining and extraction in northern Alberta’s Athabasca oil sands region produce large volumes of oil sands process–affected water (OSPW). OSPW is a complex mixture containing major ...contaminant classes including trace metals, polycyclic aromatic hydrocarbons, and naphthenic acid fraction compounds (NAFCs). Naphthenic acids (NAs) are the primary organic toxicants in OSPW, and reducing their concentrations is a priority for oil sands companies. Previous evidence has shown that constructed wetland treatment systems (CWTSs) are capable of reducing the concentration of NAs and the toxicity of OSPW through bioremediation. In this study, we constructed greenhouse mesocosms with OSPW or lab process water (LPW) (i.e., water designed to mimic OSPW minus the NAFC content) with three treatments: (1) OSPW planted with
Carex aquatilis
; (2) OSPW, no plants; and (3) LPW, no plants. The OSPW–
C. aquatilis
treatment saw a significant reduction in NAFC concentrations in comparison to OSPW, no plant treatments, but both changed the distribution of the NAFCs in similar ways. Upon completion of the study, treatments with OSPW saw fewer high-molecular-weight NAs and an increase in the abundance of O
3
- and O
4
-containing formulae
.
Results from this study provide invaluable information on how constructed wetlands can be used in future remediation of OSPW in a way that previous studies were unable to achieve due to uncontrollable environmental factors in field experiments and the active, high-energy processes used in CWTSs pilot studies.
A wide variety of sampling techniques and strategies are needed to analyze polycyclic aromatic compounds (PACs) and interpret their distributions in various environmental media (i.e., air, water, ...snow, soils, sediments, peat and biological material). In this review, we provide a summary of commonly employed sampling methods and strategies, as well as a discussion of routine and innovative approaches used to quantify and characterize PACs in frequently targeted environmental samples, with specific examples and applications in Canadian investigations. The pros and cons of different analytical techniques, including gas chromatography – flame ionization detection (GC-FID), GC low-resolution mass spectrometry (GC-LRMS), high performance liquid chromatography (HPLC) with ultraviolet, fluorescence or MS detection, GC high-resolution MS (GC-HRMS) and compound-specific stable (δ13C, δ2H) and radiocarbon (Δ14C) isotope analysis are considered. Using as an example research carried out in Canada’s Athabasca oil sands region (AOSR), where alkylated polycyclic aromatic hydrocarbons and sulfur-containing dibenzothiophenes are frequently targeted, the need to move beyond the standard list of sixteen EPA priority PAHs and for adoption of an AOSR bitumen PAC reference standard are highlighted.
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•Review of methods to collect samples for PAC analysis in the Canadian environment.•Review of techniques used to quantify or characterize PACs in environmental samples.•High-resolution MS and compound-specific isotope analysis offer unparalleled insight.•The list of 16 EPA PAHs is insufficient for studies in Canada’s oil sands region.•The adoption of an Athabasca oil sands bitumen PAC reference standard is proposed.
A comprehensive review of sampling methods, strategies and analytical techniques used to quantify and characterize PACs in the Canadian environment.
Mercury (Hg) is a pollutant of concern across Canada and transboundary anthropogenic Hg sources presently account for over 95% of national anthropogenic Hg deposition. This study applies novel ...statistical analyses of 82 high-resolution dated lake sediment cores collected from 19 regions across Canada, including nearby point sources and in remote regions and spanning a full west–east geographical range of ∼4900 km (south of 60°N and between 132 and 64°W) to quantify the recent (1990–2018) spatial and temporal trends in anthropogenic atmospheric Hg deposition. Temporal trend analysis shows significant synchronous decreasing trends in post-1990 anthropogenic Hg fluxes in western Canada in contrast to increasing trends in the east, with spatial patterns largely driven by longitude and proximity to known point source(s). Recent sediment-derived Hg fluxes agreed well with the available wet deposition monitoring. Sediment-derived atmospheric Hg deposition rates also compared well to the modeled values derived from the Hg model, when lake sites located nearby (<100 km) point sources were omitted due to difficulties in comparison between the sediment-derived and modeled values at deposition “hot spots”. This highlights the applicability of multi-core approaches to quantify spatio-temporal changes in Hg deposition over broad geographic ranges and assess the effectiveness of regional and global Hg emission reductions to address global Hg pollution concerns.
Increased oil production in Canada has resulted in proposals to extend or develop new oil pipelines. Many of these proposals have been met by concerns from the public over potential environmental ...impacts related to construction and the potential for oil spills to negatively affect groundwater quality. Crude oil sourced from the Alberta oil sands represents a significant proportion of this increase in production. This crude oil is produced as bitumen, which is subsequently diluted with light hydrocarbons to lower viscosity to allow for pipeline transport producing diluted bitumen. In this study, we pumped water through tanks filled with sand to simulate groundwater flow. Tanks were injected with either conventional crude or diluted bitumen to simulate a crude oil spill from a pipeline rupture occurring below the water table representing a pipeline river crossing scenario. Water samples were collected from the downstream end of the tanks throughout the experiment period (∼two months). Compared to water quality guidelines, effluent waters from both conventional crude and diluted bitumen tanks contained elevated concentrations of dissolved organic compounds, particularly benzene, ethylbenzene, toluene and xylenes (BTEX). The effluent from each tank had similar concentrations of benzene, whereas discharge water from conventional crude tanks contained higher concentrations of ethylbenzene, toluene and xylenes. In both tanks, and as expected, the BTEX concentrations appeared to be proportional to those determined in their injected crude oils. The measured dissolved concentrations of benzene, ethylbenzene and toluene are lower than predicted which is attributed largely due to dilution along the flow path. In addition to organic constituents, effluent sampled from the diluted bitumen tank contained some metals (Co, Cr, Fe and V) which measured constituents of the oil.
•Comparison of impacts of a spill of diluted bitumen vs. conventional crude to groundwater.•Initial BTEX concentrations in water proportional to concentrations in oil.•Lower BTEX concentrations in water from spill of diluted bitumen.•BTEX concentrations greater than Alberta Tier 1 guidelines.
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