Oil Sands Process-affected Water Research Articles

Evaluating the attenuation of naphthenic acids in constructed wetland mesocosms planted with Carex aquatilis

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 O3- and O4-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.

Online Membrane Sampling for the Mass Spectrometric Analysis of Oil Sands Process Affected Water-Derived Naphthenic Acids in Real-World Samples

Large volumes of oil sands process-affected waters (OSPW) result from heavy oil extraction in Alberta, Canada. Currently, a toxic legacy of ca. 500 Mm3 is stored in tailings ponds under a zero-discharge policy. OSPW is a complex mixture of suspended and dissolved materials including a wide range of inorganic and organic contaminants. Classically defined naphthenic acids (NAs; CnH2n+ZO2) are one of the primary toxic fractions in OSPW and have therefore been the subject of considerable research interest. Most studies employ considerable sample cleanup followed by liquid chromatography and/or high-resolution mass spectrometry (HRMS) for the characterization of these complex mixtures. However, these strategies can be time- and cost-intensive, limiting the scope of research and adoption for regulatory purposes. Condensed phase membrane introduction mass spectrometry (CP-MIMS) is emerging as a “fit-for-purpose” approach for the analysis of NAs. This technique directly interfaces the mass spectrometer with an aqueous sample using a hydrophobic semi-permeable membrane, requiring only pH adjustment to convert NAs to a membrane-permeable form. Here, we examine the perm-selectivity of classical NAs (O2) relative to their more oxidized counterparts (O3–O7) and heteroatomic (N, S) species collectively termed naphthenic acid fraction compounds (NAFCs). The investigation of 14 model compounds revealed that classically defined NAs are greater than 50-fold more membrane permeable than their oxidized/heteroatomic analogs. HRMS analysis of real OSPW extracts with and without membrane clean-up further supported selectivity towards the toxic O2 class of NAs, with >85% of the overall signal intensity attributable to O2 NAs in the membrane permeate despite as little as 34.7 ± 0.6% O2 NAs observed in the directly infused mixture. The information collected with HRMS is leveraged to refine our method for analysis of NAs at unit mass resolution. This new method is applied to 28 archived real-world samples containing NAs/NAFCs from constructed wetlands, OSPW, and environmental monitoring campaigns. Concentrations ranged from 0–25 mg/L O2 NAs and the results measured by CP-MIMS (unit mass) and SPE-HRMS (Orbitrap) showed good agreement (slope = 0.80; R2 = 0.76).

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.

Adsorption of single‐ring model naphthenic acid from oil sands tailings pond water using physically activated petroleum coke

AbstractPetroleum coke‐derived activated cokes were prepared and used for the adsorptive removal of a single‐ring naphthenic acid (NA) from synthetic oil sands process affected water (OSPW). CO2 activation produced carbon with a larger mesopore volume fraction (0.67) than steam activation (0.25). Interestingly, prolonging the activation time of CO2 from 6 to 9 h led to a simultaneous increase in specific surface area (276–405 m2/g) and mesopore volume (0.51–0.67). Furthermore, a positive relationship was found between the pseudo‐second‐order kinetic rate constant and the mesoporous volume of the activated coke. This suggests both the importance of pore size on kinetics and the fact that physical activation with a reagent such as CO2 may be better suited than chemical activation due to its ability to create mesopores. Although enlarging the pores and accelerating the adsorption rate, post‐oxidation had detrimental effects on adsorption capacity, resulting in a decrease in equilibrium adsorbed amount from 115 to 34 mg/g, a 70% decrease, when post‐oxidized with O2, due to the negative charge of oxygen‐containing functional groups. On the other hand, the measured adsorption capacity increased by over 60% when activated coke was treated with ammonia, a result of the positively charged nitrogen‐containing surface groups. Finally, in real OSPW, the activated coke had a much lower capacity for total acid‐extractable organics than for the model NA. Therefore, activated petroleum coke may not be the best choice for treating raw tailings pond water and may be better suited for polishing.

Water quality monitoring with in vitro bioassays to compare untreated oil sands process-affected water with unimpacted rivers

The selected battery of in vitro bioassays may be used to monitor exceedances of effect-based trigger (EBT) values in environments potentially receiving treated oil sands process-affected water.

A Vegetation Assessment of the Kearl Treatment Wetland following Exposure to Oil Sands Process-Affected Water

Treatment wetlands have emerged as a potential option for the treatment of oil sands process-affected water (OSPW). The long-term viability of these treatment systems relies, in part, on the health and productivity of wetland vegetation. The aim of this study is to investigate the physiological and community-level effects on wetland vegetation at the Kearl Treatment Wetland (KTW) following exposure to different OSPW sources. Annual vegetation assessments were performed during 2016–2021 to monitor species composition, total percent cover, species richness, species morphology (plant stem density, leaf length, and leaf width), and plant vigor in the KTW. Cattail was found to dominate the deep-water zones whereas water sedge was found to dominate the shallow-water zones of the wetland. Species richness in the KTW decreased with time which is typical of constructed wetlands receiving industrial effluents. No changes in plant stem density of cattails or water sedge were observed; however, leaf length decreased from 2019 to 2021, and leaf width decreased from 2020 to 2021. Plant vigor ratings increased in the KTW each year suggesting that the vegetation does not show any major signs of phytotoxicity from OSPW exposure. These results demonstrate the complex dynamics and resiliency of the vegetative community in treatment wetlands, but continued efforts to monitor plant uptake and accumulation are needed to fully assess the phytotoxic effects of OSPW exposure.

Augmentation of field fluorescence measures for improved in situ contaminant detection.

This research proposes a new method that fuses data from the field and lab-based optical measures coupled with machine learning algorithms to quantify the concentrations of toxic contaminants found in fuels and oil sands process-affected water. Selected pairs of excitation/emission intensities at key wavelengths are inputs to an augmentation neural network (NN), trained using lab-based measurements, that generates synthetic high-resolution spectra. Then, an image processing NN is used to estimate the contaminant concentrations from the spectra generated from a few key wavelengths. The presented approach is tested using naphthenic acids, phenol, fluoranthene and pyrene spiked into natural waters. The spills or loss of containment of these contaminants represent a significant risk to the environment and public health, requiring accurate and rapid detection methods to protect the surrounding aquatic environment. Results were compared with models based on only the corresponding peak intensities of each contaminant and with an image processing NN using the original spectra. Naphthenic acids, fluoranthene and pyrene were easy to detect by all methods; however, performance for more challenging signals to identify, such as phenol, was optimized by the proposed method (peak picking with mean absolute error (MAE) of 30.48µg/L, generated excitation-emission matrix with MAE of 8.30µg/L). Results suggested that data fusion and machine learning techniques can improve the detection of contaminants in the aquatic environment at environmentally relevant concentrations.

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.

Naphthenic acid fraction components from oil sands process-affected water from the Athabasca Oil Sands Region impair murine osteoblast differentiation and function.

The extraction of bitumen from surface mining in the Athabasca Oil Sands Region (AOSR) produces large quantities of oil sands process-affected water (OSPW) that needs to be stored in settling basins near extraction sites. Chemical constituents of OSPW are known to impair bone health in some organisms, which can lead to increased fracture risk and lower reproductive fitness. Naphthenic acid fraction components (NAFCs) are thought to be among the most toxic class of compounds in OSPW; however, the effect of NAFCs on osteoblast development is largely unknown. In this study, we demonstrate that NAFCs from OSPW inhibit osteoblast differentiation and deposition of extracellular matrix, which is required for bone formation. Extracellular matrix deposition was inhibited in osteoblasts exposed to 12.5-125 mg/L of NAFC for 21 days. We also show that components within NAFCs inhibit the expression of gene markers of osteoblast differentiation and function, namely, alkaline phosphatase (Alp), osteocalcin, and collagen type 1 alpha 1 (Col1a1). These effects were partially mediated by the induction of glucocorticoid receptor (GR) activity; NAFC induces the expression of the GR activity marker genes Sgk1 (12.5mg/L) and p85a (125 mg/L) and inhibits GR protein (125 mg/L) and Opg RNA (12.5mg/L) expression. This study provides evidence that NAFC concentrations of 12.5mg/L and above can directly act on osteoblasts to inhibit bone formation and suggests that NAFCs contain components that can act as GR agonists, which may have further endocrine disrupting effects on exposed wildlife.

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.

Using immune cell-based bioactivity assays to compare the inflammatory activities of oil sands process-affected waters from a pilot scale demonstration pit lake

In this study, we provide evidence that oil sands process-affected waters (OSPW) contain factors that activate the antimicrobial and proinflammatory responses of immune cells. Specifically, using the murine macrophage RAW 264.7 cell line, we establish the bioactivity of two different OSPW samples and their isolated fractions. Here, we directly compared the bioactivity of two pilot scale demonstration pit lake (DPL) water samples, which included expressed water from treated tailings (termed the before water capping sample; BWC) as well as an after water capping (AWC) sample consisting of a mixture of expressed water, precipitation, upland runoff, coagulated OSPW and added freshwater. Significant inflammatory (i.e. macrophage activating) bioactivity was associated with the AWC sample and its organic fraction (OF), whereas the BWC sample had reduced bioactivity that was primarily associated with its inorganic fraction (IF). Overall, these results indicate that at non-toxic exposure doses, the RAW 264.7 cell line serves as an acute, sensitive and reliable biosensor for the screening of inflammatory constituents within and among discrete OSPW samples.

Development of novel mixed matrix membranes (MMMs) for oil sands wastewater treatment: A critical review

AbstractWhile oil sands production plays a significant role in Canada's economy, the rise in oil sands production leads to increasing water withdrawal, consumption, storage and contamination that threaten the sustainability of water sources, biodiversity, ecosystem and public health. Effective treatment and reuse of oil sands process‐affected water (OSPW) can be a strategic solution for these issues. Membrane technology has emerged as a favourite choice for OSPW treatment with high removal and energy efficiency, small footprint and facile operation, installation and scale‐up. However, challenges also exist for membrane technologies related to fouling that causes a rapid decline in membrane performance. Mixed matrix membranes (MMMs) prepared by mixing superhydrophilic zwitterionic materials and inorganic nanoparticles into host membranes are anticipated as next‐generation membrane designs with significant potential for OSPW treatment by achieving multifunctionalities including fouling resistance, improved water permeability, selectivity and mechanical strength. Reproducibility and feasibility for large‐scale industrial applications remain important research questions for the production of MMMs for OSPW treatment. This study provides new insight on the performance, stability and durability of MMMs, outlooking to the commercialization prospect of MMMs. The research outcomes therefore can provide valuable knowledge for the design and development of high‐quality membranes with the required characteristics for OSPW treatment applications.

Interlaboratory Comparison of a Biomimetic Extraction Method Applied to Oil Sands Process-Affected Waters.

Biomimetic extraction using solid‐phase microextraction is a passive sampling analytical method that can predict the aquatic toxicity of complex petroleum substances. The method provides a nonanimal alternative to traditional bioassays with the potential to reduce both vertebrate and invertebrate aquatic toxicity testing. The technique uses commercially available polydimethylsiloxane‐coated fibers that, following nondepletive extraction of water samples, are injected into a gas chromatograph with flame ionization detection. As the predictive nature of the method is operationally defined, it is critical that its application be harmonized with regard to extraction, analysis, and standardization parameters. Results are presented from a round robin program comparing the results from 10 laboratories analyzing four different sample sets of dissolved organics in water. Samples included two incurred oil sands process–affected waters and a cracked gas oil water accommodated fraction. A fourth sample of cracked gas oil blended in an oil sands process–affected water was analyzed to demonstrate the method's ability to differentiate between neutral and ionizable dissolved hydrocarbons. Six of the 10 laboratories applied an automated version of the method using a robotic autosampler where the critical extraction steps are precisely controlled and which permits batch screening of water samples for aquatic toxicity potential. The remaining four laboratories performed the solid‐phase microextraction manually. The automated method demonstrated good reproducibility with between‐laboratory variability across the six laboratories and four samples yielding a mean relative standard deviation of 14%. The corresponding between‐laboratory variability across the four laboratories applying the manual extraction was 53%, demonstrating the importance of precisely controlling the extraction procedure. Environ Toxicol Chem 2022;41:1613–1622. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Treatment of naphthenic acids in oil sands process-affected waters with a surface flow treatment wetland: mass removal, half-life, and toxicity-reduction

This study is the first to investigate the removal of naphthenic acids in a full-scale constructed wetland within the Alberta Oil Sands region. The average mass-removal efficiency for all O2-naphthenic acids measured in three separate deployments in the wetland ranged from 7.5% to 68.9% and appeared sensitive to physicochemical properties of the naphthenic acids, environmental conditions, and water quality. Treatment efficiency of individual naphthenic acids was found to increase with increasing carbon number and decreasing number of double bond equivalents in the molecule. Treatment efficiency was also found to increase with both higher initial turbidity in OSPW entering the wetland, and warmer average OSPW temperatures during wetland operation. Half-life times of naphthenic acids in the treatment wetland ranged between 8.9 and 39 days and were substantially lower than those in tailings ponds (i.e., 12.9–13.6 years) and laboratory studies focussed on bench-scale aerobic microbial biodegradation (i.e., 44–315 days). Using published dose-response data, biomimetic extraction measurements using solid phase microextraction fibers indicate that 14 days of wetland treatment resulted in a reduction in (4 d) deformity of Danio rerio from 50 to 16%, while exhibiting less than 1% toxic response for less sensitive toxic endpoints. The study concludes that wetland treatment is a feasible and productive treatment method for naphthenic acids in oil sands process-affected water due to a combination of sorption and biodegradation.

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.

Insights into ultrasound-promoted degradation of naphthenic acid compounds in oil sands process affected water. Part II: In silico quantum screening of hydroxyl radical initiated and propagated degradation of benzoic acid

In Part I, we outlined the importance of sustainable sonochemical treatment to intensify oil sands process affected water (OSPW) treatment empirically and hypothesized degradation pathways. Herein, we elucidate the formation of intermediate products with well-defined molecular level solutions. Proposed mechanisms describe hydroxylation, decarboxylation and bond scission which drive the degradation of intermediates towards mineralization. This comprehensive first study on in silico screening of sonochemical degradation investigates quantum methods using density functional theory to explain the postulated degradation mechanisms through a theoretical radical attack approach, based on condensed Fukui reactivity indicators. A nudged elasticity band (NEB) approach is applied to find a minimum energy path (MEP), allowing the determination of intermediate products and energy barriers associated with naphthenic acid degradation. This approach provides structures and energies of the breakdown compounds formed along the reaction pathway enabling the determination of molecular reaction kinetics.In continuation of Part 1, the focus of this study is to evaluate sonochemically-induced hydroxyl radical (OH•) reactions of benzoic acid using density functional theory. Hydroxylation and decarboxylation mechanisms of the model naphthenic acid compound and its intermediates were simulated to determine the prospective pathway to ideal mineralization. DFT was applied to calculate interaction energies, Mulliken charges, Hirshfeld population analysis, dipole moments, frontier orbitals, and polarizability. Electronic properties and frontier orbital trends were also compared to computational work by Riahi et al.[1] to confirm the transition states by Nudged Elastic Band Transition State theory (NEB-TS). In combination with Hirshfeld Population analysis, Fukui indices suggest a more linear degradation pathway narrowed down from earlier experimental work by Singla et al.[2]. The linear free energy relationship for the newly suggested computational benzoic acid degradation can be determined by lnkTST/W=-1.677ΔG-15.41 with a R2 of 0.9997 according to classic transition state theory and Wigner tunneling. This computational method can be used to explore possible degradation pathways of other NAs and bridges molecular-to-macroscale sonochemical degradation of NA’s through a manifestation of molecular solutions.

The effects of oil sands process-affected water naphthenic acid fraction components on GDF15 secretion in extravillous trophoblast cells

Exposure to compounds present in petroleum and wastewaters from oil and gas extraction sites in the Alberta Oil Sands Region can impair reproductive health. It has been established that acid extractable organics found in oil sands process-affected water (OSPW) such as naphthenic acids (NA-fraction components; NAFC) can adversely affect reproductive outcomes. We have shown that NAFC exposure results in a significant upregulation of GDF15 in placental trophoblasts, a cellular stress marker known to be involved in human embryonic development and necessary for the maintenance of pregnancy. However, little is known regarding the mechanism(s) underlying NAFC-induced increases in GDF15 production during early placentation. The goal of this study was to examine the effects of NAFC exposure on the regulation of critical transcription factors of GDF15 in extravillous trophoblast cells. Of these transcription factors, inflammatory mediators including prostaglandins have been reported to inhibit proliferation and migration of trophoblast cells in vitro. Hence, the secondary goal of this study was to determine whether inflammation mediated through prostaglandin production is critical to GDF15 secretion. HTR-8/SVneo cells were exposed to an NAFC for 6 and 24 h to assess the expression of key transcriptional regulators, GDF15 secretion, and prostaglandin (PGE2) output. Treatment with NAFC (125 mg/L only) significantly increased GDF15 expression and secretion in association with upregulation of the transcription factors KLF4, EGR1, ATF3 and TP53. Similarly, PTGS2 (i.e. COX2) expression and PGE2 output were significantly increased at the same concentration. However, co-treatment with a COX2 selective antagonist (SC236) only partially blocked the NAFC-induced increase in PGE2 output and did not block GDF15 expression or secretion. These findings suggest that while NAFC may affect GDF15 production, it is not exclusively a result of prostaglandin-mediated inflammation. This study provides new insights into the mechanisms by which NAFC may adversely affect placental trophoblast cell function in mammals.

Application of machine learning methods for rapid fluorescence-based detection of naphthenic acids and phenol in natural surface waters

Approximately 1.4 billion m3 of fluid tailings produced from oil sands mining operations are currently being held in Alberta, Canada and pose a significant risk to the environment if not properly treated and managed. The ability to quantify levels of toxic compounds, such as naphthenic acids (NAs) and phenol, accurately and rapidly in the produced oil sands process-affected water (OSPW) is required to ensure the protection of the surrounding aquatic environment. In this paper, fluorescence techniques are investigated to rapidly quantify NAs and phenol concentrations in natural surface waters. Machine learning approaches were applied to identify relevant spectral features to improve detection accuracy in the presence of background interference from organic matter in natural waters. NAs were relatively easy to detect by all methods, however deep convolutional neural networks (CNN) resulted in optimized performance for phenol with mean absolute errors of 1.78 – 1.81 mg/L and 4.68–5.41 µg/L, respectively. Visualization of spectral areas of importance revealed that deep CNNs utilized logical areas of the fluorescence spectra associated with NAs and phenol signals. Results suggest machine learning approaches to interpreting fluorescence data can accurately predict individual toxic components of OSPW in natural waters at environmentally relevant concentrations.

Insights into ultrasound-promoted degradation of naphthenic acid compounds in oil sands process affected water. Part I: Accelerated H-abstraction and decarboxylation of aromatic and alicyclic compounds

Propelled by enormous increase in demand for fuel sources, Canadian oil sands are becoming increasingly important as a fuel source due to their abundance and upgrading capability. However, extraction of bitumen, a high acid crude (HAC) oil, requires 2–3 units of water per unit of oil resulting in naphthenic acid (NA)-rich oil sands process affected water (OSPW) collected in effluent ponds. This study illustrates the role of sonochemistry in the accelerated degradation through H-abstraction and subsequent decarboxylation of aromatic and alicyclic naphthenic acid model compounds. Benzoic acid and 3-methylcyclohexane carboxylic acid were selected as model NA compounds to investigate the mechanism of hydroxyl radical (OH•) initiated carboxylic acid degradation in 378 KHz sonochemical reactor. Established FTIR methods with low resolution LCMS spectroscopy confirmation were applied to determine the extent of carboxylic acid degradation and identify the formation of products. FTIR monitoring showed a non-linear degradation of carboxylic acids with formation of many intermediates highlighting the shift from cyclic carboxylic acids to cyclic alcohols during BA degradation. Subsequent decrease in carboxylic acid groups signifies scission of cyclic structures before complete mineralization. This is confirmed with the LCMS identification of products such as: 3-hydroxybenzoic acid and phenol. This study postulated new breakdown pathways for degradation of benzoic acid with complete mineralization at a sonochemical reaction time (SRT) of 4 h. A radical quenching process was also inferred through the formation of conglomerates during sonochemical degradation of BA. Extension of the study to 3-methylcyclohexane carboxylic acid (3mCHA) shows similar non-linearity with an increase in carboxylic acid groups indicating H-abstraction followed by ring-opened compounds. However, due to the complex nature of 3mCHA’s ring-opened compounds, complete mineralization is not achieved. The putative role of sonochemistry is a promising and sustainable degradation method for mitigating NAs in OSPW, but sonication periods need to be considered carefully to ensure adequate mineralization of their constituents and combinatorial methods with other advanced oxidation methods may be needed to enhance industrial application.In Part II, an in silico screening approach using first principles is reported to identify the breakdown of the organic compounds and determine molecular rates of reaction to confirm the mechanistic origins of the compounds formed.

Inflammation of Gill Epithelia in Fish Causes Increased Permeation of Petrogenic Polar Organic Chemicals via Disruption of Tight Junctions.

The epithelial cell layer that lines the gills of fish controls paracellular permeation of chemicals through tight junctions. The integrity of tight junctions can be affected by inflammation, which likely affects the bioavailability of chemicals. Here, the inflammation of the rainbow trout gill cell line RTgill-W1 was induced via exposure to bacterial lipopolysaccharides (LPS). Cells were then coexposed to extracts of oil sands process-affected water (OSPW), which contain complex mixtures of chemicals. After 24 h of exposure, cells exposed to LPS showed a reduction in transepithelial electrical resistance, an indicator of tight junction integrity. Quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis determined that abundances of transcripts of genes coding for tight junction proteins were significantly less in cells exposed to 20, 50, or 100 mg L-1 LPS. Chemical analysis revealed increased permeation of constituents of OSPW across epithelia at all studied LPS concentrations. These in vitro findings were confirmed in vivo in rainbow trout exposed to LPS and OSPW for 48 h, which resulted in greater accumulation of chemicals relative to that for fish exposed to OSPW alone. Our results demonstrated that inflammation and disruption of tight junctions could lead to greater uptake of potentially harmful chemicals from the environment, which has implications for mixture risk assessment.