Characterization of Naphthenic Acids and Other Dissolved Organics in Natural Water from the Athabasca Oil Sands Region, Canada

Comprehensive characterization of organics in oil sands process water in constructed mesocosms utilizing multiple analytical methods

This study aims to provide a thorough characterization of dissolved organics in oil sands process water (OSPW) in field-based aquatic mesocosms at both molecular and bulk measurement levels using multiple analytical methods. In a 3-year outdoor mesocosm experiment, the analysis of naphthenic acid (NA) species was conducted using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS). The results revealed the removal of both total NAs (38% and 35%) and classical NAs (O2-NAs, 58% and 49%) in undiluted and half-diluted OSPW, respectively. The increased ratios of oxidized NAs (O3-O6 NAs) to classical NAs suggested a transformation trend. The results also indicated that O2-NAs with higher carbon number and lower double bond equivalent (DBE) were more easily degraded in the mesocosm systems. Biomimetic extraction using solid-phase microextraction (BE-SPME) measurement displayed 26% (undiluted OSPW) and 30% (half-diluted OSPW) decrease in total bioavailable organics over 3 years. Naphthenic acids fraction compounds (NAFCs) obtained by liquid-liquid extraction (LLE) were also determined using Fourier transform infrared spectroscopy (FTIR). Reduction in acute toxicity for undiluted (43%) and half-diluted (26%) OSPW was observed over 3 years, which are well correlated with the decreases of NAs and BE-SPME concentrations. Moreover, BE-SPME values were found to be linearly correlated with total NAs concentrations (r = 0.96) and NAFCs (r = 0.96). Additionally, the linear relationships of individual O2-O6 NA species and BE-SPME concentrations unveiled the changes in the relative abundances of O2-O6 NA species in total bioavailable organics over time in the mesocosms. The present study has provided comprehensive insights by integrating various analytical methods, contributing valuable information for assessing the effectiveness of aquatic mesocosm systems in studying the temporal changes of organics in OSPW.

Sample preparation, analytical characterization, monitoring, risk assessment and treatment of naphthenic acids in industrial wastewater and surrounding water impacted by unconventional petroleum production

Industrial extraction of unconventional petroleum results in notable volumes of oil sands process water (OSPW), containing elevated concentrations of naphthenic acids (NAs). The presence of NAs represents an intricate amalgamation of dissolved organic constituents, thereby presenting a notable hurdle for the domain of environmental analytical chemistry. There is growing concern about monitoring the potential seepage of OSPW NAs into nearby groundwater and river water. This review summarizes recent studies on sample preparation, characterization, monitoring, risk assessment, and treatment of NAs in industrial wastewater and surrounding water. Sample preparation approaches, such as liquid-liquid extraction, solid phase microextraction, and solid phase extraction, are crucial in isolating chemical standards, performing molecular level analysis, assessing aquatic toxicity, monitoring, and treating OSPW. Instrument techniques for NAs analysis were reviewed to cover different injection modes, ionization sources, and mass analyzers. Recent studies of transfer and transformation of NAs provide insights to differentiate between anthropogenic and natural bitumen-derived sources of NAs. In addition, related risk assessment and treatment studies were also present for elucidation of environmental implication and reclamation strategies. The synthesis of the current state of scientific knowledge presented in this review targets government regulators, academic researchers, and industrial scientists with interests spanning analytical chemistry, toxicology, and wastewater management.

Site-specific spatiotemporal occurrence and molecular congener distributions of naphthenic acids in Athabasca oil sands wetlands of Alberta, Canada

The Athabasca oil sands region (AOSR) of Alberta, Canada is notable for its considerable unconventional petroleum extraction projects, where bitumen is extracted from naturally-occurring oil sands ore. The large scale of these heavy crude oil developments raises concerns because of their potential to distribute and/or otherwise influence the occurrence, behaviour, and fate of environmental contaminants. Naphthenic acids (NAs) are one such contaminant class of concern in the AOSR, so studies have examined the occurrence and molecular profiles of NAs in the region. We catalogued the spatiotemporal occurrence and characteristics of NAs in boreal wetlands in the AOSR over a 7-year period, using derivatized liquid chromatography-tandem mass spectrometry (LC-MS/MS). Comparing median concentrations of NAs across these wetlands revealed a pattern of NAs suggesting NAs in surface waters derived from oil sands deposits. Opportunistic wetlands that formed adjacent to reclaimed overburden and other reclamation activities had the highest concentrations of NAs and consistent patterns suggestive of bitumen-derived inputs. However, similar patterns in the occurrence of NAs were also observed in undeveloped natural wetlands located above the known surface-mineable oil sands deposit that underlies the region. Intra-annual sampling results along with inter-annual comparisons across wetlands demonstrated that differences in the spatial and temporal NA concentrations were dependent on local factors, particularly when naturally occurring oil sands ores were observed in the wetland or drainage catchment.

Chemical communication in wood frog (Rana sylvatica) tadpoles is influenced by early-life exposure to naphthenic acid fraction compounds

Environmental pollutants can disrupt chemical communication between aquatic organisms by interfering with the production, transmission, and/or detection of, as well as responses to, chemical cues. Here, we test the hypothesis that early-life exposure to naphthenic acid fraction compounds (NAFCs) from oil sands tailings disrupts antipredator-associated chemical communication in larval amphibians. Wild adult wood frogs (Rana sylvatica) captured during their natural breeding period were combined (1 female:2 males) in six replicate mesocosms filled with either uncontaminated lakewater or with NAFCs isolated from an active tailings pond in Alberta, Canada, at nominal 5 mg/L concentrations. Egg clutches were incubated and tadpoles maintained in their respective mesocosms for ∼40 days post-hatch. Tadpoles (Gosner stage 25-31) were then transferred individually to trial arenas filled with uncontaminated water and exposed to one of six chemical alarm cue (AC) stimuli solutions following a 3 × 2 × 2 design (3 AC types × 2 stimulus carriers × 2 rearing exposure groups). Relative to control tadpoles, NAFC-exposed tadpoles demonstrated higher baseline activity levels (line crosses and direction changes) when introduced to uncontaminated water. Antipredator responses differed in graded fashion with AC type, with control ACs eliciting the greatest latency to resume activity, water the least, and NAFC-exposed ACs intermediate. Pre- to post-stimulus difference scores were non-significant in control tadpoles, while NAFC-exposed tadpoles demonstrated significantly greater variation. While this suggests that exposure to NAFCs from fertilization through hatching may have interfered with AC production, it is unclear whether the quality or quantity of cues was affected. There was also no clear evidence that NAFC carrier water interfered with ACs or the alarm response in unexposed control tadpoles. These results emphasize the importance of understanding how behavioral and physiological effects of early-life NAFC exposure on critical antipredator responses may persist across life history stages.

Evaluation of negative effect of Naphthenic acids (NAs) on physiological metabolism and polycyclic aromatic hydrocarbons adsorption of Phragmites australis

Toxic substances in the environment disturb the adsorption of pollutants in plants but little is known about the underlying mechanisms of these processes. This study evaluated the PAH adsorption by Phragmites australis under NAs stress. Results showed that Naphthenic acids (NAs) significantly decreased the adsorption of PAHs and had higher selectivity for type and structure. P. australis root cell growth and mitosis were significantly affected by NAs, which was accompanied by serious disturbances in mitochondrial function. The physiological evaluation showed the NAs could increase Reactive Oxygen Species (ROS) accumulation by around 16-fold and cause damage to the root cell normal redox equilibrium. The levels of three key related antioxidants, PLA, CAT and POD, decreased significantly to 35-50% under NAs stress and were dependent upon NAs concentration. Furthermore, NAs could significantly change the concentration and species of root exudates of P. ausralis. Autotoxic substances, including alcohol and amines, increased by 28.63% and 23.96, respectively. Sixteen compounds were identified and assumed as potential biomarkers. Galactonic, glyceric, and octadecanoic acid had the general effect of activating PAH in soil. The global view of the metabolic pathway suggests that NAs influenced the citric acid cycle, fatty acid synthesis, amino acid metabolism and the phenylpropanoid pathway. Detection data results indicated that the energy products cause hypoxia and oxidative stress, which are the main processes under the NAs. Furthermore, verification of these processes was fulfilled through gene expression and biomarkers quantification. Our results provide novel metabolic insights into the mechanisms of PAHs adsorption by P. australis under NAs disturbance, suggesting that monitoring NAs in phytoremediation applications is necessary.

Persistent Cytotoxicity and Endocrine Activity in the First Oil Sands End-Pit Lake

Oil sands process-affected water (OSPW) is a byproduct of bitumen extraction that has persistent toxicity owing to its complex mixture of organics. A prominent remediation strategy that involves aging OSPW in end-pit lakes and Base Mine Lake (BML) is the first full-scale test. Its effectiveness over the first 5 years was investigated here using real-time cell analysis, yeast estrogenic and androgenic screens (YES/YAS), and ultra-high-resolution mass spectrometry. HepG2 cytotoxicity per volume of BML organics extracted decreased with age; however, the toxic potency (i.e., toxicity per mass of extract) was not significantly different between years. This was consistent with mass spectral evidence showing no difference in chemical profiles, yet lower total abundance of organics in field-aged samples, suggestive that dilution explains the declining cytotoxicity in BML. The IC50's of BML extracts for YES/YAS antagonism were at environmental concentrations and were similar despite differences in field-age. Persistent YES/YAS antagonism and cytotoxicity were detected in experimental pond OSPW field-aged >20 years, and while organic acids were depleted here, non-acid chemical classes were enriched compared to BML, suggesting these contribute to persistent toxicity of aged OSPW. To avoid a legacy of contaminated sites, active water treatment may be required to accelerate detoxification of end-pit lakes.

A review of the occurrence, distribution, and impact of bitumen seeps on soil and groundwater in parts of southwestern Nigeria

The impact of bitumen components on soil and groundwater resources is of environmental importance. Contaminants' influx into the environment from bitumen components through anthropogenic activities such as exploration, mining, transportation, and usage of bitumen in all its forms have been reported globally. However, gaps exist in the geogenic occurrence of bitumen in the shallow subsurface such as in southwest Nigeria, contaminating the soil and groundwater resources. This review presents in situ bitumen seeps as a source of geogenic soil and groundwater contaminants in southwestern Nigeria. We conducted a systematic review of literatures based on defined selection criteria. We derived information on the state of knowledge about bitumen seep occurrences and distribution in southwestern Nigeria. Also, the processes that exacerbate bitumen contaminants' influx into soil and groundwater were enunciated. At the same time, case examples highlighted areas for possible in situ bitumen contamination studies in Nigeria. The results of this review showed that a multidisciplinary approach has been employed to assess and monitor the contaminants resulting from the various activities involving the exploitation and application of bitumen in Nigeria. These studies emphasize bitumen contaminants as emanating from anthropogenic sources. The results also suggested that bitumen studies have been mainly exploratory to improve the understanding of the economic potential of the hydrocarbon reserve. Also, recent advances in bitumen contaminants studies accounted for the heterogeneous nature of the bitumen. This allows for the optimized categorization of the mechanism and processes undergone by the different bitumen components when released as environmental contaminants. However, a knowledge gap exists in characterizing and understanding the effects of in situ bitumen seeps as a geogenic source of soil and groundwater contamination. This review identifies the possibility of geogenic soil and groundwater contamination by in situ bitumen seeps in the coastal plain sand of the Dahomey basin in southwestern Nigeria. The impact of the bitumen contaminants on the environment was discussed, while methods for accessing the occurrence and distribution of the bitumen contaminants were highlighted.

Naphthenic acid fraction compounds reduce the reproductive success of wood frogs (Rana sylvatica) by affecting offspring viability

Understanding the toxicity of organic compounds in oil sands process-affected water (OSPW) is necessary to inform the development of environmental guidelines related to wastewater management in Canada's oil sands region. In the present study, we investigated the effects of naphthenic acid fraction compounds (NAFCs), one of the most toxic components of OSPW, on mating behaviour, fertility, and offspring viability in the wood frog (Rana sylvatica). Wild adult wood frogs were exposed separately from the opposite sex to 0, 5, or 10 mg/L of OSPW-derived NAFCs for 24 h and then combined in outdoor lake water mesocosms containing the same NAFC concentrations (n = 2 males and 1 female per mesocosm, n = 3 mesocosms per treatment). Mating events were recorded for 48 h and egg masses were measured to determine adult fertility. NAFC exposure had no significant effect on mating behaviour (probability of amplexus and oviposition, amplexus and oviposition latency, total duration of amplexus and number of amplectic events) or fertility (fertilization success and clutch size). Tadpoles (50 individuals per mesocosm at hatching, and 15 individuals per mesocosm from 42 d post-hatch) were reared in the same mesocosms under chronic NAFC exposure until metamorphic climax (61-85 d after hatching). Offspring exposed to 10 mg/L NAFCs during development were less likely to survive and complete metamorphosis, grew at a reduced rate, and displayed more frequent morphological abnormalities. These abnormalities included limb anomalies at metamorphosis, described for the first time after NAFC exposure. The results of this study suggest that NAFCs reduce wood frog reproductive success through declines in offspring viability and therefore raise the concern that exposure to NAFCs during reproduction and development may affect the recruitment of native amphibian populations in the oil sands region.

The acute toxicity of bitumen-influenced groundwaters from the oil sands region to aquatic organisms

The extraction of surface mined bitumen from oil sands deposits in northern Alberta, Canada produces large quantities of liquid tailings waste, termed oil sands process-affected water (OSPW), which are stored in large tailings ponds. OSPW-derived chemicals from several tailings ponds migrating past containment structures and through groundwater systems pose a concern for surface water contamination. The present study investigated the toxicity of groundwater from near-field sites adjacent to a tailings pond with OPSW influence and far-field sites with only natural oil sands bitumen influence. The acute toxicity of unfractionated groundwater and isolated organic fractions was assessed using a suite of aquatic organisms (Pimephales promelas, Oryzias latipes, Daphnia magna, Hyalella azteca, Lampsilis spp., Ceriodaphnia dubia, Hexagenia spp., and Vibrio fischeri). Assessment of unfractionated groundwater demonstrated toxicity towards all invertebrates in at least one far-field sample, with both near-field and far-field samples with bitumen influence toxic towards P. promelas, while no toxicity was observed for O. latipes. When assessing the unfractionated groundwater and isolated organic fractions from near-field and far-field groundwater sites, P. promelas and H. azteca were the most sensitive to organic components, while D. magna and L. cardium were most sensitive to the inorganic components. Groundwater containing appreciable amounts of dissolved organics exhibited similar toxicities to sensitive species regardless of an OSPW or natural bitumen source. The lack of a clear distinction in relative acute toxicities between near-field and far-field samples indicates that the water-soluble chemicals associated with bitumen are acutely toxic to several aquatic organisms. This result, combined with the similarities in chemical profiles between bitumen-influenced groundwater originating from OSPW and/or natural sources, suggests that the industrial bitumen extraction processes corresponding to the tailings pond in this study are not contributing unique toxic substances to groundwater, relative to natural bitumen compounds present in groundwater flow systems.

Incorporating Industrial and Climatic Covariates into Analyses of Fish Health Indicators Measured in a Stream in Canada’s Oil Sands Region

Industrial and other human activities in Canada’s oil sands region (OSR) influence the environment. However, these impacts can be challenging to separate from natural stresses in flowing waters by comparing upstream reference sites to downstream exposure locations. For example, health indicators of lake chub (Couesius plumbeus) compared between locations in the Ells River (Upper and Lower) in 2013 to 2015 and 2018 demonstrated statistical differences. To further examine the potential sources of variation in fish, we also analyzed data at sites over time. When fish captured in 2018 were compared to pooled reference years (2013–2015), results indicated multiple differences in fish, but most of the differences disappeared when environmental covariates were included in the Elastic Net (EN) regularized regression models. However, when industrial covariates were included separately in the EN, the large differences in 2018 also disappeared, also suggesting the potential influence of these covariables on the health of fish. Further ENs incorporating both environmental and industrial covariates along with other variables which may describe industrial and natural influences, such as spring or summer precipitation and summer wind speeds and distance-based penalty factors, also support some of the suspected and potential mechanisms of impact. Further exploratory analyses simulating changes from zero and the mean (industrial) activity levels using the regression equations respectively suggest effects exceeding established critical effect sizes (CES) for fish measurements may already be present or effects may occur with small future changes in some industrial activities. Additional simulations also suggest that changing regional hydrological and thermal regimes in the future may also cause changes in fish measurements exceeding the CESs. The results of this study suggest the wide applicability of the approach for monitoring the health of fish in the OSR and beyond. The results also suggest follow-up work required to further evaluate the veracity of the suggested relationships identified in this analysis.

Fathead Minnows Exposed to Organic Compounds from Oil Sands Tailings as Embryos Have Reduced Survival, Impaired Development, and Altered Behaviors That Persist into Larval Stages

Our study evaluated whether exposure to naphthenic acid fraction compounds (NAFCs) extracted from oil sands process-affected waters (OSPW) has adverse effects on fish embryos that persist into later life. We exposed fathead minnow (Pimephales promelas) embryos to concentrations of NAFCs found in OSPW (2.5-54 mg/L) for 7 days (1 day postfertilization to hatch), then raised surviving larvae in outdoor mesocosms of uncontaminated lake water for 1 month. Embryos exposed to NAFCs were more likely to exhibit malformations (by up to 8-fold) and had slower heart rates (by up to 24%) compared to controls. Fish raised in uncontaminated lake water following exposure to NAFCs as embryos, were 2.5-fold less likely to survive during the larval stage than control fish. These fish also showed up to a 45% decrease in swim activity and a 36% increase in swim burst events during behavioral tests relative to controls. We conclude that exposure to NAFCs during the embryonic stage can have lasting effects on fish survival, physiology, and behavior that persist at least through the larval stage. These findings of delayed mortalities and persistent sublethal effects of embryonic NAFC exposure are relevant to informing the development of regulations on treated OSPW releases from mining operations. Environ Toxicol Chem 2022;41:1319-1332. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A critical review of the ecological status of lakes and rivers from Canada's oil sands region

We synthesize the information available from the peer-reviewed literature on the ecological status of lakes and rivers in the oil sands region (OSR) of Canada. The majority of the research from the OSR has been performed in or near the minable region and examines the concentrations, flux, or enrichment of contaminants of concern (CoCs). Proximity to oil sands facilities and the beginning of commercial activities tend to be associated with greater estimates of CoCs across studies. Research suggests the higher measurements of CoCs are typically associated with wind-blown dust, but other sources also contribute. Exploratory analyses further suggest relationships with facility production and fuel use data. Exceedances of environmental quality guidelines for CoCs are also reported in lake sediments, but there are no indications of toxicity including those within the areas of the greatest atmospheric deposition. Instead, primary production has increased in most lakes over time. Spatial differences are observed in streams, but causal relationships with industrial activity are often confounded by substantial natural influences. Despite this, there may be signals associated with site preparation for new mines, potential persistent differences, and a potential effect of petroleum coke used as fuel on some indices of health in fish captured in the Steepbank River. There is also evidence of improvements in the ecological condition of some rivers. Despite the volume of material available, much of the work remains temporally, spatially, or technically isolated. Overcoming the isolation of studies would enhance the utility of information available for the region, but additional recommendations for improving monitoring can be made, such as a shift to site-specific analyses in streams and further use of industry-reported data. Integr Environ Assess Manag 2022;18:361-387. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Direct analysis of naphthenic acids in produced water and crude oil by NH2-surface-modified wooden-tip electrospray ionization mass spectrometry

This work describes the surface coating of wooden toothpicks with amino groups (NH₂) for electrospray ionization mass spectrometry (MS) analysis of naphthenic acids (NAs) in produced water samples and crude oil fractions. NH₂ was introduced into the cellulosic material through a silanization reaction using aminopropyltriethoxysilane. An NH₂-modified toothpick was inserted into the analyte extraction sample and was subsequently used as an electrospray emitter for MS analysis. The extraction conditions were optimized by analyzing NAs (benzoic acid, 1-naphthoic acid, decanoic acid, 3,5-dimethyladamantane-1-carboxylic acid, and 3,5-dimethyladamantane-1-acetic acid) in pure water, and the best condition was using 5 min of extraction time with the samples under agitation. Modified and unmodified wooden toothpicks were compared, and the intensities of all NAs were higher when using the modified substrates than when using the unmodified ones. Limit of detection (LOD), limit of quantification (LOQ), linearity, precision, and recovery were determined by analyzing decanoic acid in seawater samples. The LOD and LOQ were 2 and 5 μg mL^-1, respectively, and a linear correlation (R² = 0.9927) was obtained with concentrations ranging from 5 to 250 μg mL^-1. Precision values ranged from 6 to 13% and recoveries from 89 to 106%. The technique was also employed to analyze three produced water samples, in which decanoic acid was semi-quantified, and the concentrations ranged from 10 to 13 μg mL^-1. High abundances of acidic compounds of class O2 with DBEs (double bond equivalents) ranging from 1 to 3 and carbon numbers going from 8 to 12 were detected in the produced water samples. The results suggest that the modification of wooden toothpicks with NH₂ might offer a significant advancement in the knowledge of cheap substrates that can improve the sensitivity of analysis of NAs in water samples.

Ionization selectivity of electrospray and atmospheric pressure photoionization FT-ICR MS for petroleum refinery wastewater dissolved organic matter

Dissolved organic matter (DOM) in petroleum refinery wastewater is an extremely complex mixture. A better understanding of chemical compositions of DOM at the molecular level is necessary for the design and optimization of wastewater treatment processes. In this study, two largely different DOM samples, one from a petroleum refinery wastewater and the other from the Suwannee river water, were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with positive-/negative-ion electrospray ionization (ESI), and positive-ion atmospheric pressure photoionization (APPI). For wastewater DOM, a total of 6226 molecular formulae were assigned in the three ionization modes. However, only 1182 molecular formulae were common in all three mass spectra, indicating that the techniques were highly complementary in the types of molecules they ionize. Acid O_x (x = 1-9) and basic N₁O_x (x = 0-2) classes were dominant in the wastewater DOM detected in negative-ion and positive-ion ESI mode, respectively. And the wastewater DOM contains considerable amounts of polycyclic aromatic hydrocarbons that did not respond to ESI but can be ionized selectively by APPI. Compared with riverine DOM, the refinery wastewater DOM has a higher molecular complexity and is more enriched in hydrocarbon, and nitrogen- and sulfur-containing compounds. The results show that the major components of refinery wastewater DOM were distinctive from those of the natural organic matter. Though not quantitative, the results obtained by various ionization techniques were found to be complementary, and are helpful to our understanding of the selectivity of different ionization techniques as well as the molecular compositions of DOM.

Characterization of naphthenic acid fraction compounds in water from Athabasca oil sands wetlands by Orbitrap high-resolution mass spectrometry

Classical naphthenic acids (NAs) are known to be primary aquatic toxicants of concern in the Athabasca oil sands region (AOSR), and are a component of naphthenic acid fraction compounds (NAFCs). Recent studies conducted in the AOSR have examined metals and polycyclic aromatic hydrocarbons in regional wetlands. However, few studies have described NAs and/or NAFCs in AOSR wetlands. To address this gap, we examined NAFC profiles in the water of different wetlands in the AOSR, including naturalized borrow pits (i.e., abandoned pits created by excavation of road-building materials), and opportunistically-formed wetlands associated with reclamation activities. For comparison, NAFC profiles from these wetlands were compared to an opportunistic wetland formed from tailings pond dyke seepage. Samples were prepared using solid-phase extraction and analyzed using negative-ion high-resolution Orbitrap mass spectrometry. Principal component analyses (PCA) revealed patterns to the NAFC profiles in the wetlands. The first distinct grouping of wetlands included water bodies associated with reclamation activities that are located on and/or adjacent to mining overburden. One other wetland, HATS5w, separated from all other wetlands during PCA, and had a unique NAFC profile; detailed examination of NAFCs revealed HATS5w contained the heaviest (i.e., high m/z components) and most unsaturated NAFCs among study locations, demonstrating the usefulness of high-resolution mass spectrometry for characterizing individual wetlands. The NAFCs of HATS5w are also substantially different from bitumen-derived inputs in overburden-adjacent opportunistic wetlands. Collectively, the NAFC profiles presented provide new information on background levels of polar bitumen-derived organics in AOSR wetlands.

Solar photocatalytic treatment of model and real oil sands process water naphthenic acids by bismuth tungstate: Effect of catalyst morphology and cations on the degradation kinetics and pathways

Bitumen extraction from oil sands produces large quantities of oil sands process water (OSPW), which contains recalcitrant naphthenic acids (NAs). In this study, three different morphologies of bismuth tungstate (Bi₂WO₆) photocatalysts were prepared by hydrothermal method. The prepared catalyst was characterized to obtain its structural, textural and chemical properties and tested for the degradation of model NAs and real OSPW under simulated solar irradiation. Nanoplate, flower-like and swirl-like Bi₂WO₆ were prepared and the results showed that the flower-like structure exhibited the highest specific surface area and total pore volume. The highest photocatalytic activity for the degradation of NAs was also demonstrated by the flower-like Bi₂WO₆, achieving complete degradation of cyclohexanoic acid (CHA) at fluence-based rate constant of 0.0929 cm²/J. Superoxide radicals (O₂^•-) and holes were identified as the major reactive species generated during the photocatalytic process. The effect of metallic ions on the degradation rates of S-containing and N-containing NAs differed and the heteroatom was found to be the main reactive site. The by-products of heteroatomic NAs were identified and degradation pathways were reported for the first time. The concentration changes of each byproduct were further estimated by mass balance. This research provides valuable information for the treatment of NAs by engineered passive solar-based approaches.

Co-biodegradation of naphthenic acids in anoxic denitrifying biofilm reactors

Anoxic co-biodegradation of linear and cyclic naphthenic acids (NAs) namely octanoic acid, trans-4-methyl-1-cyclohexane carboxylic acid (trans-4MCHCA), cis- and trans-4-methyl-1-cyclohexane-acetic acids (cis-4MCHAA and trans-4MCHAA) was investigated in denitrifying biofilm reactors. In all evaluated compositions, co-biodegradation of NAs was coupled to denitrification, with octanoic acid showing the fastest biodegradation rate (1180.4 mg L^-1 h^-1 at loading rate of 1180.4 mg L^-1 h^-1), followed by trans-4MCHCA (398.1 mg L^-1 h^-1 at loading rate of 435.8 mg L^-1 h^-1), trans-4MCHAA (25.7 mg L^-1 h^-1 at loading rate of 221.7 mg L^-1 h^-1), and cis-4MCHAA (5.3 mg L^-1 h^-1 at loading rate of 16.9 mg L^-1 h^-1). Biodegradation of octanoic acid and trans-4MCHCA were not influenced by the presence of recalcitrant NAs (cis- and trans-4MCHAA). Co-biodegradation of cis- and trans-4MCHAA with octanoic acid, trans-4MCHCA, or their combination enhanced the biodegradability of these recalcitrant NAs, with the positive impact being more pronounced for trans-4MCHCA. Finally anoxic co-biodegradation of NAs under denitrifying conditions proceeded at rates that were faster than the aerobic rates obtained in similar mixtures. Anoxic biodegradation, therefore, is an effective alternative for in situ treatment of oil sands process water in anoxic stabilization ponds amended with nitrate, or as an ex situ treatment approach in denitrifying bioreactors whereby the cost and technical challenges of aeration are eliminated.

Characterization of raw and ozonated oil sands process water utilizing atmospheric pressure gas chromatography time-of-flight mass spectrometry combined with solid phase microextractionun

This work describes a novel application of atmospheric pressure gas chromatography time-of-flight mass spectrometry (APGC-TOF-MS) combined with solid-phase microextraction (SPME) for the simultaneous analysis of hydrocarbons and naphthenic acids (NAs) species in raw and ozone-treated oil sands process water (OSPW). SPME method using polydimethylsiloxane (PDMS)-coated fibers was validated using gas chromatography with flame ionization detector (GC-FID) to ensure the SPME extractions were operated appropriately. The ionization pathways of the hydrocarbon species in OSPW in the APGC source were verified by analyzing a mixture of eight polyaromatic hydrocarbons which were ionized primarily via charge transfer to produce [M⁺] while NAs in OSPW were found to be ionized through protonation to generate [MH⁺] in the wet APGC source. SPME/APGC-TOF-MS analysis demonstrated a different composition profile in OSPW #1, with 74.5% of hydrocarbon species, 23.4% of O₂-NAs, and 2.1% of the oxidized NA species at extraction pH 2.0 compared with that obtained by UPLC-TOF-MS analysis (36.9% of O₂-NAs, 26.8% of O₃-NAs, 24.9% of O₄-NAs, 9.1% of O₅-NAs, 2.3% of O₆-NAs). Moreover, the peak areas of the total NAs and the total peak areas of NAs + hydrocarbons measured by SPME/APGC-TOF-MS correlated excellently with the total NA concentration determined by UPLC-TOF-MS (R² = 0.90) and the concentrations of the total acid-extractable organics determined by SPME/GC-FID (R² = 0.98), respectively. APGC-TOF-MS integrated with the SPME techniques could extend the range of target compounds and be a promising alternative to evaluate and characterize NAs and hydrocarbon in different water types.

Non-target profiling of bitumen-influenced waters for the identification of tracers unique to oil sands processed-affected water (OSPW) in the Athabasca watershed of Alberta, Canada

RATIONALE

The objective of this study was to identify unique chemical tracers of oil sands process-affected water (OSPW) to enable definitive discrimination of tailings pond seepage from natural bitumen-influenced waters from the Canadian Alberta McMurray formation.

METHODS

The approach involved comparing unknowns from an unprecedented sample set of OSPW (n = 4) and OSPW-affected groundwaters (n = 15) with natural bitumen-influenced groundwaters (n = 20), using high-performance liquid chromatography/electrospray ionisation high-resolution mass spectrometry (HPLC/ESI-HRMS) operated in both polarities.

RESULTS

Four unknown chemical entities were identified as potential tracers of OSPW seepage and subsequently subjected to structural elucidation. One potential tracer, tentatively identified as a thiophene-containing carboxylic acid [C₁₅ H₂₃ O₃ S]^- , was only detected in OSPW and OSPW-affected samples, thereby showing the greatest diagnostic potential. The remaining three unknowns, postulated to be two thiochroman isomers [C₁₇ H₂₅ O₃ S]⁺ and an ethyl-naphthalene isomer [C₁₆ H₂₁ ]⁺ , were detected in one and two background groundwaters, respectively.

CONCLUSIONS

We advanced the state of knowledge for tracers of tailings seepage beyond heteroatomic classes, to identifying diagnostic substances, with structures postulated. Synthesis of the four proposed structures is recommended to enable structural confirmations. This research will guide and inform the Oil Sands Monitoring Program in its efforts to assess potential influences of oil sands development on the Athabasca River watershed.

Potential Influence of Sewage Phosphorus and Wet and Dry Deposition Detected in Fish Collected in the Athabasca River North of Fort McMurray

The health of fish is a primary indicator of ecosystem response in the Oil Sands Region of northeastern Alberta. However, industrial activity is accompanied by other stressors, such as the discharge of sewage, municipal activity, forest fires, and natural weathering and erosion of bitumen. To combat the spatial confounding influences, we examined white sucker (Catostomus commersonii) captured in the Athabasca River at sites over time (2011–2019) and included covariates to account for the possible sources of influence. The analyses suggest spatially heterogeneous influences of natural factors on fish, such as discharge and air temperature, but also the influence of sewage phosphorus and precipitation. Among the stressors examined here, precipitation may be the most complex and may include a mixture of sources including inputs from tributaries, urban activity, industrial development, and forest fires. Although suggestive, the attribution of variance and detection of changes are affected by sample sizes in some years; these analyses may have missed effects or misspecified important relationships, especially in males. Despite these limitations, the analyses suggest potential differences may be associated with precipitation and highlight the need to integrate robust information on known and suspected stressors in future monitoring of aquatic ecosystems in the oil sands region and beyond.

Long-term spatial and temporal trends, and source apportionment of polycyclic aromatic compounds in the Athabasca Oil Sands Region

We investigated the spatio-temporal trends of polycyclic aromatic compounds (PACs) deposition in the Athabasca Oil Sands Region (AOSR) between 2008 and 2017, and applied source apportionment tools to assess sources using snowpacks. Estimated PAC mass deposition was significantly correlated with crude oil production (R² = 0.48, p = 0.03), and increased between 2008 and 2017. Loadings of alkylated PACs c1-, c2-fluorenes/pyrenes and c1-, c3-benzo[a]anthracenes/chrysenes/triphenylenes significantly increased at mid-field sites (25-50 km from central industrial reference site, AR6) (Mann-Kendall, p < 0.05) reflecting physical expansion of the AOSR. The distance from emission sources was important in the deposition of PACs, including the distance from AR6 (R² = 0.69-0.91), nearest petcoke storage (R² = 0.77-0.88), 0.89) and upgrader stack (R² = 0.56-0.61). Source apportionment PAC distribution profiles of the source materials (petcokes, oil sand ores, road dust) did not show unique matching profiles with the snowpacks. However, the minimal presence of retene in petcokes and an abundance of benzo[ghi]fluoranthene in road dust was observed, and suggests potential for these compounds as chemical markers in distinguishing sources. Furthermore, correlations between PACs and selected metal(loid)s in the AOSR snowpacks were assessed to infer potential common sources. Significant positive (p < 0.05) correlations between metal(loid)s enriched in bitumen (vanadium, molybdenum, nickel) and PACs, at near to mid-field (0-50 km from AR6) sites suggests common sources or similar transfer and fate processes. The results of our study convey data necessary for monitoring studies in the constantly developing AOSR, advance our knowledge of PACs profiles in source materials (including the much less studied alkylated PACs and dibenzothiophenes), which will be valuable for other studies related to oil pollution, urban run-off and forest fires. PACs mass deposition increasing between 2008 and 2017 coincident with crude oil production, and retene and benzo[ghi]fluoranthene show potential in distinguishing AOSR sources.

Isomer-specific monitoring of naphthenic acids at an oil sands pit lake by comprehensive two-dimensional gas chromatography-mass spectrometry

Naphthenic acids (NAs) are persistent, toxic contaminants that are found to accumulate in oil sands process-affected water (OSPW) and tailings after bitumen extraction. A number of strategies for the reclamation of oil sands tailings are currently being tested, including the development of the first demonstration pit lake by Syncrude Canada, Base Mine Lake (BML). An important component of reclamation activities is understanding the source and cycling of NAs in such reclamation systems. However, NAs exist as a highly complex mixture of thousands of compounds which makes their analysis an ongoing challenge. Herein, comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry (GC × GC/TOFMS) was used to analyze the methylated extracts of water samples from the water cap and fluid fine tailings (FFT) deposit of BML to characterize the variations in NA distributions between geochemical zones. A collection of (alkylated) monocyclic-, bicyclic-, adamantane-, and thiophene-type carboxylic acids were identified. Total relative abundances were calculated for each NA class (by summation of peak areas of all detected isomers) and minimal variability was detected in the water cap. Total relative abundances for each NA class were either similar or higher in the FFT, relative to the water cap. Examination of isomer distributions indicated that differences in abundance values were generally driven by variations in only one or two isomers of a given NA class. Furthermore, GC × GC revealed distinct isomer profiles were observed between two FFT samples and between the FFT and water cap. While it is not yet clear whether these differences are due to differences in sources of NAs or in their environmental processing, these results illustrate the capability of GC × GC to investigate these questions and thus contribute to the management of these compounds within reclamation or environmental systems.

Fourier transform infrared spectroscopy as a surrogate tool for the quantification of naphthenic acids in oil sands process water and groundwater

Naphthenic acid fraction compounds (NAFCs), defined herein as the polar organic compounds extracted from the acidified oil sands process water (OSPW) samples using dichloromethane, are becoming the research hotspot due to their presence in large amount in OSPW and along with other potentially NA-contaminated water streams from the mining site. Fourier transform infrared spectroscopy (FTIR) method is commonly used to quantify NAFCs and assumes that the total NA concentration is measured as the sum of the responses for all carboxylic acid functional groups. In this study, the NAFCs in various OSPW and groundwater (GW) samples from an active oil sands mining site were analyzed using FTIR. All water samples were pretreated using either solid-phase extraction (SPE) or liquid-liquid extraction (LLE) methods before analysis. The results showed that SPE produced higher recoveries of NAFCs than LLE for most water samples under current experimental conditions. For the quantification of NAFCs, commercial Fluka NA mixture and a pre-calibrated OSPW extract were employed as the calibration standards. The NAFCs calibrated with Fluka NA mixture and OSPW extract had clear linear relationships. The concentrations of NAFCs obtained using OSPW extract standard curve were 2.5 times the NAFC concentrations obtained using the Fluka NA mixture standard curve. Additionally, good linear correlations were observed between the total NAs and O₂-O₆ NA species determined by ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC-TOFMS) and the NAFCs measured by FTIR. According to these correlations, the NA compositions in NAFCs were developed, and the relative abundances of O₂-O₆ NA species in NAFCs were similar for SPE and LLE pretreated samples. The findings of this study demonstrated that FTIR could be used as a promising tool to monitor total NA species and to estimate the NA profile in different environmental water samples.

Enhancing data acquisition for the analysis of complex organic matter in direct-infusion Orbitrap mass spectrometry using micro-scans

RATIONALE

Acquisition quality in analytical science is key to obtaining optimal data from a sample. In very high-resolution mass spectrometry, quality is driven by the optimization of multiple parameters, including the use of scans and micro-scans (or transients) for performing a Fourier transformation.

METHODS

Thirty-nine mass spectra of a single synthesized complex sample were acquired using various numbers of scans and micro-scans determined through a simple experimental design. An electrospray ionization source coupled with an LTQ Orbitrap XL™ mass spectrometer was used, and acquisition was performed using a single mass range. All the resulting spectra were treated in the same way to enable comparisons of assigned stoichiometric formulae between acquisitions.

RESULTS

Converting the number of scans into micro-scans enhances signal quality by lowering noise and reducing artifacts. This modification also increases the number of attributed stoichiometric formulae for an equivalent acquisition time, giving access to a larger molecular diversity for the analyzed complex sample.

CONCLUSIONS

For complex samples, the use of long acquisition times leads to optimal data quality, and the use of micro-scans instead of scans-only maximizes the number of attributed stoichiometric formulae.

Engineering Microbes for Remediation of Oil Sands Tailings

Synthetic biology and adaptive laboratory evolution are key tools for developing biotechnology platforms for the remediation of oil sands tailings. However, field deployment and subsequent regulation of engineered and/or evolved strains is rife with uncertainties and risks. Here, we detail an innovation strategy to derisk and deploy engineered bioremediation platforms.

Direct analysis of naphthenic acids in constructed wetland samples by condensed phase membrane introduction mass spectrometry

The application of direct mass spectrometry techniques to the analysis of complex samples has a number of advantages including reduced sample handling, higher sample throughput, in situ process monitoring, and the potential for adaptation to on-site analysis. We report the application of a semi-permeable capillary hollow fibre membrane probe (immersed directly into an aqueous sample) coupled to a triple quadrupole mass spectrometer by a continuously flowing methanol acceptor phase for the rapid analysis of naphthenic acids with unit mass resolution. The intensity of the naphthenic acid-associated peaks in the mass spectrum are normalized to an internal standard in the acceptor phase for quantitation and the relative abundance of the peaks in the mass spectrum are employed to monitor compositional changes in the naphthenic acid mixture using principle component analysis. We demonstrate the direct analysis of a synthetic oil sands process-affected water for classical naphthenic acids (C_nH_2n+zO₂) as they are attenuated through constructed wetlands containing sedge (Carex aquatilis), cattail (Typha latifolia), or bulrush (Schoenoplectus acutus). Quantitative results for on-line membrane sampling compare favourably to those obtained by solid-phase extraction high-resolution mass spectrometry. Additionally, chemometric analysis of the mass spectra indicates a clear discrimination between naphthenic acid-influenced and natural background waters. Furthermore, the compositional changes within complex naphthenic acid mixtures track closely with the degree of attenuation. Overall, the technique is successful in following changes in both the concentration and composition of naphthenic acids from synthetic oil sands process-affected waters, with the potential for high throughput screening and environmental forensics.

Photodegradation of bitumen-derived organics in oil sands process-affected water

The chemical composition of water-soluble organics in oil sands process-affected water (OSPW) is primarily composed of natural constituents of bitumen that are solubilized and concentrated during aqueous extraction of oil sands. OSPW organics are persistent and acutely toxic, and a leading remediation strategy is long-term ageing in end-pit lakes, despite limited data available on its photochemical fate. Here, direct photolysis of whole OSPW, or of its constituent fractions, was examined at environmentally relevant wavelengths (>290 nm) in bench-top studies. Changes in the chemical profiles of whole OSPW, acid- (AEO), and base-extractable organics (BEO) were characterized by liquid chromatography with ultra-high resolution mass spectrometry in negative (-) and positive (+) ionization modes. Following 18 d of irradiation, photolysis reduced the total ion intensity in all samples in both modes. The most photo-labile species included the O₂^-, O₃^-, O₄^-, O₂S^-, and O₄S^- chemical classes, which were depleted in whole OSPW by 93-100% after only 5 d. In positive mode, detected species were more recalcitrant than those detected in negative mode, with an average reduction across all heteroatomic classes of 75 ± 11.0% after 18 d. Estimated environmental half-lives for heteroatomic classes ranged from 57 d (O₄S^-) to 545 d (O₃N⁺), with a greater recalcitrance for classes detected in positive mode compared to negative mode. Under field conditions in end-pit lakes, natural photolysis may be an important mechanism for effective OSPW remediation, and we suggest that future end-pit lakes be shallow to maximize light penetration and natural photolysis in ageing OSPW.

Bioaccumulation potential of naphthenic acids and other ionizable dissolved organics in oil sands process water (OSPW) - A review

Bitumen recovery via mining in Alberta's Athabasca region generates large quantities of oil sands process water (OSPW). Aquatic toxicity of OSPW has been well-studied and the class of organic compounds referred to as naphthenic acids (NAs) are consistently implicated as the primary driver. Proposed lease closure options include treated produced waters in reclaimed landscapes such as pit lakes and wetlands. Consequently, it is crucial to understand the bioaccumulation potential of NAs and other OSPW dissolved organics in these environments. Early studies were focussed only on NAs due to analytical limitations, however, later studies investigated additional classes of dissolved organics in OSPW. Reported bioconcentration factors (BCFs) for NAs in fish and amphibians range from 0.24 to 53 L/kg wet-weight. Most quantitative assessments of NAs bioaccumulation potential evaluated commercial NAs mixtures as a surrogate for OSPW and used using single-ion monitoring for measuring NAs concentrations. The resulting BCF values are based on the NA isomers that conform to the formula, C₁₃H₂₂O₂. More recently, an advanced analytical technique capable of determining the profile of different isomer classes in OSPW showed that NAs and other OSPW ionizable dissolved organics (OSPW-IDO) have low partitioning to simulated biological storage lipids, suggesting low bioaccumulation potential. Using the same analytical technique to assess in vivo fish exposures, a subsequent study reported a range of BCFs for OSPW NAs between 0.7 and 53 L/kg wet-weight and heteroatomic isomer classes containing S or N heteroatoms had BCFs between 0.6 and 28 L/kg wet-weight. Reported BCFs for all isomer classes of the OSPW-IDO fraction were less than the Canadian standard for bioaccumulative designation (i.e., BCF ≥ 5000).

Distinguishing Natural from Anthropogenic Sources of Acid Extractable Organics in Groundwater near Oil Sands Tailings Ponds

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 (δ¹³C_pyr) 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 tool-sulfur isotope analysis (δ³⁴S) of AEOs. The combined use of both δ¹³C_pyr 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.

Diagnostic Ratio Analysis: A New Concept for the Tracking of Oil Sands Process-Affected Water Naphthenic Acids and Other Water-Soluble Organics in Surface Waters

A diagnostic ratio forensics tool, similar to that recognized internationally for oil spill source identification, is proposed for use in conjunction with existing LC/QToF quantitative methodology for bitumen-derived water-soluble organics (WSOs). The concept recognizes that bitumen WSOs bear a chemical skeletal relationship to stearane and hopane oil biomarkers. The method uses response ratios for 50 selected WSOs compared between samples by their relative percent difference and adopted acceptance criteria. Oil sands process-affected water (OSPW) samples from different locations within a single tailings pond were shown to match, while those from different industrial sites did not. Acid extractable organic samples collected over 3 weeks from the same location within a single tailings pond matched with each other; as did temporal OSPW samples a year apart. Blind quality assurance samples of OSPW diluted in surface waters were positively identified to their corresponding OSPW source. No interferences were observed from surface waters, and there was no match between bitumen-influenced groundwater and OSPW samples, as expected for different sources. Proof of concept for OSPW source identification using diagnostic ratios was demonstrated, with anticipated application in the tracking of OSPW plumes in surface receiving waters, together with the potential for confirmation of source.

Advances in Distinguishing Groundwater Influenced by Oil Sands Process-Affected Water (OSPW) from Natural Bitumen-Influenced Groundwaters

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.

Colloid chemistry and experimental techniques for understanding fundamental behaviour of produced water in oil and gas production

Due to increasing volumes of produced water and environmental concerns related to its discharge, water treatment has become a major challenge during the production of crude oil and natural gas. With continuously stricter regulations for discharging produced water to sea, the operators are obliged to look for ways to improve the treatment processes or re-use the water in a beneficial way, for example as a pressure support during oil recovery (produced water re-injection). To improve the knowledge of the underlying phenomena governing separation processes, detailed information of the composition and interfacial properties of produced water is undoubtedly useful and could provide valuable input for better understanding and improving separation models. This review article summarizes knowledge gained about produced water composition and the most common treatment technologies, which are later used to describe the fundamental phenomena occurring during separation. These colloidal interactions, such as coalescence of oil droplets, bubble-droplet attachment or partitioning of components between oil and water, are of crucial importance for the performance of various technologies and are sometimes overlooked in physical considerations of produced water treatment. The last part of the review deals with the experimental methodologies that are available to study these phenomena, provide data for models and support development of more efficient separation processes.

Current knowledge of seepage from oil sands tailings ponds and its environmental influence in northeastern Alberta

Seepage of oil sand process-affected waters (OSPW) from tailings ponds into surface waters is a common concern in the minable oil sands region of northeast Alberta. Research on seepage has been extensive, but few comprehensive treatments evaluating all aspects relevant to the phenomenon are available. In this work, the current information relevant for understanding the state of seepage from tailings ponds was reviewed. The information suggests the infiltration of OSPW into groundwater occurs near some ponds. OSPW may also be present in sediments beneath the Athabasca River adjacent to one pond, but there are no clear observations of OSPW in the river water. Similarly, most water samples from tributaries also show no evidence of OSPW, but these observations are limited by the lack of systematic, systemic, and repeated surveys, missing baseline data, standard analytical approaches, and reference materials. Waters naturally influenced by bitumen, discharge of saline groundwaters, and dilution also potentially affect the consolidation of information and certainty of any conclusions. Despite these challenges, some data suggest OSPW may be present in two tributaries of the Athabasca River adjacent to tailings ponds: McLean Creek and Lower Beaver River. Irrespective of the possible source(s), constituents of OSPW often affect organisms exposed in laboratories, but research in all but one study suggests the concentrations of organics in the surface water bodies assessed are below the standard toxicological effect thresholds for these compounds. In contrast, many samples of groundwater, irrespective of source, likely affect biota. Biomonitoring of surface waters suggests generic responses to stressors, but the influence of natural phenomena and occasionally nutrient enrichment are often suggested by data. In summary, valuable research has been done on seepage. The data suggest infiltration into groundwater is common, seepage into surface waters is not, and anthropogenic biological impacts are not likely.

Overview of Existing Science to Inform Oil Sands Process Water Release: A Technical Workshop Summary

The extraction of oil sands from mining operations in the Athabasca Oil Sands Region uses an alkaline hot water extraction process. The oil sands process water (OSPW) is recycled to facilitate material transport (e.g., ore and tailings), process cooling, and is also reused in the extraction process. The industry has expanded since commercial mining began in 1967 and companies have been accumulating increasing inventories of OSPW. Short- and long-term sustainable water management practices require the ability to return treated water to the environment. The safe release of OSPW needs to be based on sound science and engineering practices to ensure downstream protection of ecological and human health. A significant body of research has contributed to the understanding of the chemistry and toxicity of OSPW. A multistakeholder science workshop was held in September 2017 to summarize the state of science on the toxicity and chemistry of OSPW. The goal of the workshop was to review completed research in the areas of toxicology, chemical analysis, and monitoring to support the release of treated oil sands water. A key outcome from the workshop was identifying research needs to inform future water management practices required to support OSPW return. Another key outcome of the workshop was the recognition that methods are sufficiently developed to characterize chemical and toxicological characteristics of OSPW to address and close knowledge gaps. Industry, government, and local indigenous stakeholders have proceeded to utilize these insights in reviewing policy and regulations. Integr Environ Assess Manag 2019;15:519-527. © 2019 SETAC.

Variation in toxicity and ecological risks associated with some oil sands groundwaters

The surface mining of oil sands deposits requires the removal of groundwater to stabilize the deposit (depressurization) and make it safe for mining. The chemistry and toxicity of deep groundwaters (from 45 to 144 m below an active mining operation) were characterized to determine if the release of groundwaters would pose a risk to a receiving aquatic environment. Concentrations of conventional chemicals such as nutrients and metals were generally below CCME chronic guidelines. Concentrations of oil sands naphthenic acids (NAs) varied depending on the method of measurement and were routinely >1 mg L^-1. Groundwaters rarely caused lethality to fish and invertebrates in standard acute and chronic toxicity tests. Algal cell production was negatively correlated with chlorides and potentially negatively with NAs. Other chronic toxicity variations were less obviously correlated with measured chemistry. The groundwaters had moderately-high oxygen demand (2 to 33 mg L^-1), likely associated with nutrients and organic substances, and thus have the potential to enrich receiving surface water environments if left untreated and depending on the receiving environment. This paper presents for the first time a comprehensive (3 year) pairing of water chemistry and toxicity data on groundwaters collected from aquifer depressurization wells below an active oil sands operation. These data will contribute to a better understanding of the environmental risk these waters potentially pose, and ultimately, to the improvement of water management strategies and the reduction of the overall surface mining footprint of oil sands operations.

Spatial assessment of major and trace element concentrations from Lower Athabasca Region Trout-perch (Percopsis omiscomaycus) otoliths

The Lower Athabasca Region (LAR) is home to the largest bitumen deposit in Alberta, and has seen industrial development related to the extraction and processing of bituminous sands since the late 1960s. Along with industrial and economic growth related to oil sands development, environmental concerns have increased in recent decades, including those about potential effects on fish. We measured major and trace element concentrations in Trout-perch otoliths from the Athabasca and Clearwater Rivers in the LAR, to illustrate spatial variations and identify possible industrial impacts. Both laser ablation ICP-MS and solution-based ICP-MS methods were employed. Of the trace elements enriched in bitumen (V, Ni, Mo and Re), only Ni and Re were above the limits of detection using at least one of the methods. The only significant differences in element concentrations between upstream and downstream locations were found for Li, Cu, and Pb which were more abundant upstream of industry. For comparison and additional perspective, otoliths from the same fish species, but taken from the Batchawana River in northern Ontario, were also examined. The fish from Alberta yielded greater concentrations of Ba, Bi, Li, Mg, Na, Re, Sc, Th and Y, but the Ontario fish had more Cr, Rb and Tl, likely because of differences in geology.

Profiling of individual naphthenic acids at a composite tailings reclamation fen by comprehensive two-dimensional gas chromatography-mass spectrometry

Naphthenic acids (NAs) are naturally occurring in the Athabasca oil sands region (AOSR) and accumulate in tailings as a result of water-based extraction processes. NAs exist as a complex mixture, so the development of an analytical technique to characterize them has been an on-going challenge. The aim of this study was to use comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry to monitor individual NAs within a wetland reclamation site in the AOSR. Samples were collected from four monitoring wells at the site and the extracts were found to contain numerous resolved isomers of classical (monocyclic-, bicyclic-, adamantane-, indane-, and tetralin-type carboxylic acids) and sulfur-containing NAs (thiamonocyclic- and thiophene-type carboxylic acids). The absolute abundances of the monitored NAs were compared between four monitoring wells and unique profiles were observed at each well. Few significant changes in absolute abundances were observed over the sampling period, with the exception of one well (Well 6A). In addition, isomeric percent compositions were calculated for each set of structural isomers, and one-way analysis of variance (ANOVA) and two-dimensional hierarchical cluster analysis revealed high spatial variation at the site. However, consistent distributions were observed at each of the monitoring wells for some sets of NA isomers (such as: adamantane NAs), which may be useful for forensic applications, such as identifying sources of contamination or demonstrating biodegradation. The methods and results presented in this study demonstrate the utility of monitoring individual NAs, since both changes in absolute abundances of individual NAs and the distribution of NA isomers have the ability to provide insight into their sources and the processes controlling their concentrations that are not only of relevance to the Alberta Oil Sands, but also to other petroleum deposits and environmental systems.

Monitoring of classical, oxidized, and heteroatomic naphthenic acids species in oil sands process water and groundwater from the active oil sands operation area

The classical, oxidized, and heteroatomic naphthenic acids (NAs) species were monitored in the oil sands process water (OSPW) and groundwater from the active oil sands operation area, using solid phase extraction sample preparation and high resolution mass spectrometry analysis. Groundwater samples include Pleistocene channel aquifer groundwater (PLCA) and oil sands basal aquifer groundwater (OSBA) from different depth of underground. The concentrations of O_x-NAs decreased from OSPW to PLCA, and then increased from PLCA to OSBA, which is deeper than PLCA. The NAs in PLCA mainly comprised of O_x-NAs and N-NAs and the percentage of S-NAs was negligible. Results revealed relative abundances of individual NA species in total NAs varies among different water layers and the potential environmental impacts are expected to be variable. Principal component analysis results of O₂-NAs or O₄-NAs could be used for differentiation of water types. O₂-NAs with n = 12-16 and |Z| = 4-6, and O₄-NAs with n = 14-20 and |Z| = 6-8, were identified as marker compounds that could serve as surrogates of the larger complex NA mixture for source differentiation. This work utilized a combination of sample preparation, instrumental analysis, and statistical analysis methods to obtain knowledge of the occurrence, composition, and transfer of NAs in the groundwater of the Alberta oil sands operation area.

Selenium in surface waters of the lower Athabasca River watershed: Chemical speciation and implications for aquatic life

Selenium in the lower Athabasca River (Alberta, Canada) is of concern due to potential inputs from the weathering of shallow bitumen deposits and emissions from nearby surface mines and upgraders. Understanding the source of this Se, however, is complicated by contributions from naturally saline groundwater and organic matter-rich tributaries. As part of a two-year multi-disciplinary study to assess natural and anthropogenic inputs, Se and its chemical speciation were determined in water samples collected along a ∼125 km transect of the Athabasca River and associated tributaries. Selenium was also determined in the muscle of Trout-perch (Percopsis omiscomaycus), a non-migratory fish species, that were sampled from selected locations. Dissolved (<0.45 μm) Se in the Athabasca River was consistently low in 2014 (0.11 ± 0.02 μg L^-1; n = 14) and 2015 (0.16 ± 0.02 μg L^-1; n = 21), with no observable increase from upstream to downstream. Selenate was the predominant inorganic form (∼60 ng L^-1) and selenite was below detection limits at most locations. The average concentration of Se in Trout-perch muscle was 2.2 ± 0.4 mg kg^-1 (n = 34), and no significant difference (p > 0.05) was observed between upstream and midstream (industrial) or downstream reaches. Tributary waters contained very low concentrations of Se (typically < 0.1 μg L^-1), which was most likely present in the form of dissolved organic colloids.

Petroleomic analysis of the treatment of naphthenic organics in oil sands process-affected water with buoyant photocatalysts

The persistence of toxicity associated with the soluble naphthenic organic compounds (NOCs) of oil sands process-affected water (OSPW) implies that a treatment solution may be necessary to enable safe return of this water to the environment. Due to recent advances in high-resolution mass spectrometry (HRMS), the majority of the toxicity of OSPW is currently understood to derive from a subset of toxic classes, comprising only a minority of the total NOCs. Herein, oxidative treatment of OSPW with buoyant photocatalysts was evaluated under a petroleomics paradigm: chemical changes across acid-, base- and neutral-extractable organic fractions were tracked throughout the treatment with both positive and negative ion mode electrospray ionization (ESI) Orbitrap MS. Elimination of detected OS⁺ and NO⁺ classes of concern in the earliest stages of the treatment, along with preferential degradation of high carbon-numbered O₂^- acids, suggest that photocatalysis may detoxify OSPW with higher efficiency than previously thought. Application of petroleomic level analysis offers unprecedented insights into the treatment of petroleum impacted water, allowing reaction trends to be followed across multiple fractions and thousands of compounds simultaneously.

The effect of naphthenic acids on physiological characteristics of the microalgae Phaeodactylum tricornutum and Platymonas helgolandica var. tsingtaoensis

Naphthenic acids (NAs) account for 1-2% of crude oil and represent its main acidic component. However, the aquatoxic effects of NAs on marine phytoplankton and their ecological risks have remained largely unknown. Using the marine microalgae Phaeodactylum tricornutum and Platymonas helgolandica var. tsingtaoensis as the target, we studied the effects of NAs on their growth, cell morphology and physiological characteristics. The cell density decreased as the concentrations of NAs increased, indicating that they had an adverse effect on growth of the investigated algae in a concentration-dependent manner. Moreover, scanning electron microscopy revealed NAs exposure caused damage such as deformed cells, shrunken surface and ruptured cell structures. Exposure to NAs at higher concentrations for 48 h significantly increased the content of chlorophyll (Chl) a and b in P. tricornutum, but decreased their levels in P. helgolandica var. tsingtaoensis. NAs with concentrations no higher than 4 mg/L gradually enhanced the Chl fluorescence (ChlF) parameters and decreased the ChlF parameters at higher concentrations for the two marine microalgae. Additionally, NAs induced hormesis on photosynthetic efficiency of the two microalgae and also have the species difference in their aquatic toxicity. Overall, the results of this study provide a better understanding of the physiological responses of phytoplankton and will enable better risk assessments of NAs.

Fate and behavior of oil sands naphthenic acids in a pilot-scale treatment wetland as characterized by negative-ion electrospray ionization Orbitrap mass spectrometry

Large volumes of oil sands process-affected water (OSPW) are generated during the extraction of bitumen from oil sands in the Athabasca region of northeastern Alberta, Canada. As part of the development of treatment technologies, molecular characterization of naphthenic acids (NAs) and naphthenic acid fraction compounds (NAFC) in wetlands is a topic of research to better understand their fate and behavior in aquatic environments. Reported here is the application of high-resolution negative-ion electrospray Orbitrap-mass spectrometry for molecular characterization of NAs and NAFCs in a non-aerated constructed treatment wetland. The effectiveness of the wetlands to remove OSPW-NAs and NAFCs was evaluated by monitoring the changes in distributions of NAFC compounds in the untreated sample and non-aerated treatment system. After correction for measured evapotranspiration, the removal rate of the classical NAs followed approximately first-order kinetics, with higher rates observed for structures with relatively higher number of carbon atoms. These findings indicate that constructed wetland treatment is a viable method for removal of classical NAs in OSPW. Work is underway to evaluate the effects of wetland design on water quality improvement, preferential removal of different NAFC species, and reduction in toxicity.