Oil Sands Process-affected Water Research Articles

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 (CnH2n+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.

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 (δ13Cpyr) to characterize and quantify the acid extractable organics (AEOs) fraction containing NAs in the subsurface near an oil sands tailings pond. Here, we build upon this work through further development and application of these techniques at two different study sites near two different tailings ponds, in conjunction with the use of an additional isotopic tool-sulfur isotope analysis (δ34S) of AEOs. The combined use of both δ13Cpyr and δ34S allowed for discrimination of AEOs into the three end-members relevant to ascertaining the NA environmental footprint within the region: (1) OSPW; (2) McMurray Formation groundwater (i.e., naturally occurring bitumen), and; (3) naturally occurring non-bitumen. A Bayesian isotopic mixing model was used to determine the relative proportions of these three sources in groundwater at both study sites. Although background levels of OSPW-derived AEOs were generally low, one sample containing 49-99% (95% credibility interval) OSPW-derived AEOs was detected within an inferred preferential flow-path, highlighting the potential for this technique to track tailings pond seepage.

Biodegradation of naphthenic acids: identification of Rhodococcus opacus R7 genes as molecular markers for environmental monitoring and their application in slurry microcosms.

Nowadays, the increase of the unconventional oil deposit exploitation and the amount of oil sands process-affected waters (OSPW) in tailing ponds emerges the importance of developing bio-monitoring strategies for the restoration of these habitats. The major constituents of such deposits are naphthenic acids (NAs), emerging contaminant mixtures with toxic and recalcitrant properties. With the aim of developing bio-monitoring strategies based on culture-independent approach, we identified genes coding for enzymes involved in NA degradation from Rhodococcus opacus R7 genome, after the evaluation of its ability to mineralize model NAs. R. opacus R7 whole-genome analysis unveiled the presence of pobA and chcpca gene clusters putatively involved in NAs degradation. Gene expression analysis demonstrated the specific induction of R7 aliA1 gene, encoding for a long-chain-fatty-acid-CoA ligase, in the presence of cyclohexanecarboxylic acid (CHCA) and hexanoic acid (HA), selected as representative compounds for alicyclic and linear NAs, respectively. Therefore, aliA1 gene was selected as a molecular marker to monitor the biodegradative potential of slurry-phase sand microcosms in different conditions: spiked with CHCA, in the presence of R. opacus R7, the autochthonous microbial community, and combining these factors. Results revealed that the aliA1-targeting culture-independent approach could be a useful method for bio-monitoring of NA degradation in a model laboratory system.

Profiling low molecular weight organic compounds from naphthenic acids, acid extractable organic mixtures, and oil sands process-affected water by SPME-GC-EIMS

Naphthenic acids (NAs) are complex mixtures of carboxylic acids from petroleum that have industrial applications and that may be released to the environment after oil spills. There is significant research on the chemical composition and toxicity of water-soluble NAs derived from oil sands mining in Alberta, Canada. Yet, little is known about low molecular weight organic compounds (LMWOC) from these sources. Headspace solid-phase microextraction coupled to gas chromatography-electron impact mass spectrometry was used for LMWOC profiling of commercial NA blends, and an acid-extractable organics (AEOs) mixture from a tailings pond. From Sigma 1, Sigma 2, Merichem NAs and the AEO extract, 54, 56, 40 and 4 compounds were identified, respectively. These include aliphatic and cyclic hydrocarbons, carboxylic acids, alkylbenzenes, phenols, naphthalene and alkyl-naphthalene, and decalin compounds. A sample of oil sands process-affected water (OSPW) and aqueous solutions of the NA blends were evaluated for matrix effects on LMWOC profiles. Principal component and clustering analyses revealed that LMWOC profiles of commercial extracts were closely related but distinct from the AEO and OSPW samples. Some of the identified LMWOC are reported to be genotoxic or carcinogenic, and therefore the NA mixtures and AEOs should be considered hazardous materials and further evaluated.

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.

Can the toxicity of naphthenic acids in oil sands process-affected water be mitigated by a green photocatalytic method?

Our study evaluates the efficacy of a “green” (i.e., sustainable, recyclable, and reusable) technology to treat waste waters produced by Canada’s oil sands industry. We examined the ability of a novel advanced oxidative method—ultra-violet photocatalysis over titanium dioxide (TiO2)-coated microparticles—to reduce the toxicity of naphthenic acid fraction components (NAFC) to early life stages of the fathead minnow ( Pimephales promelas). Lengthening the duration of photocatalysis resulted in greater removal of NAFC from bioassay exposure waters; low- and high-intensity treatments reduced NAFC concentrations to about 20 and 3 mg/L (by Fourier-transformed infrared spectroscopy, FTIR), respectively. Treatments reduced the acute lethality of NAFC to fathead minnows by over half after low-intensity treatment and three-fold after high-intensity treatment. However, incomplete degradation in low-intensity treatments increased the incidence of chronic toxicity relative to untreated NAFC solutions and cardiovascular abnormalities were common even with >80% of NAFC degraded. Our findings demonstrate that photocatalysis over TiO2 microparticles is a promising method for mitigating the toxicity of oil sands process-affected water-derived NAFC to fish native to the oil sands region, but the intensity of the photocatalytic treatment needs to be considered carefully to ensure adequate mineralization of toxic constituents.

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.

Diamondoids are not forever: microbial biotransformation of diamondoid carboxylic acids.

SummaryOil sands process‐affected waters (OSPW) contain persistent, toxic naphthenic acids (NAs), including the abundant yet little‐studied diamondoid carboxylic acids. Therefore, we investigated the aerobic microbial biotransformation of two of the most abundant, chronically toxic and environmentally relevant diamondoid carboxylic acids: adamantane‐1‐carboxylic acid (A1CA) and 3‐ethyl adamantane carboxylic acid (3EA). We inoculated into minimal salts media with diamondoid carboxylic acids as sole carbon and energy source two samples: (i) a surface water sample (designated TPW) collected from a test pit from the Mildred Lake Settling Basin and (ii) a water sample (designated 2 m) collected at a water depth of 2 m from a tailings pond. By day 33, in TPW enrichments, 71% of A1CA and 50% of 3EA was transformed, with 50% reduction in EC20 toxicity. Similar results were found for 2 m enrichments. Biotransformation of A1CA and 3EA resulted in the production of two metabolites, tentatively identified as 2‐hydroxyadamantane‐1‐carboxylic acid and 3‐ethyladamantane‐2‐ol respectively. Accumulation of both metabolites was less than the loss of the parent compound, indicating that they would have continued to be transformed beyond 33 days and not accumulate as dead‐end metabolites. There were shifts in bacterial community composition during biotransformation, with Pseudomonas species, especially P. stutzeri, dominating enrichments irrespective of the diamondoid carboxylic acid. In conclusion, we demonstrated the microbial biotransformation of two diamondoid carboxylic acids, which has potential application for their removal and detoxification from vast OSPW that are a major environmental threat.

Predicting Naphthenic Acid Migration Through the Foundation of Oil Sands Tailing Pond

In this paper, a conceptual model was developed to predict the seepage of oil sands process-affected water with capabilities of evaluating the transport and attenuation of naphthenic acids through the dykes and the foundations of oil sands tailings pond. The model incorporates naphthenic acid diffusion, adsorption, dispersion, advection, and biodegradation, and was modeled through the commercial software tools to predict naphthenic acid fate in both spatial and time scales. The tailing pond of the Muskeg River Mine in the Athabasca oil sands deposit was investigated in the case study. The comparison between the onsite monitoring data and the simulation results was in good agreement. In addition, limiting factors for migration of naphthenic acid were also discussed based on a parametric sensitivity study.

Transcriptome Analysis Reveals That Naphthenic Acids Perturb Gene Networks Related to Metabolic Processes, Membrane Integrity, and Gut Function in Silurana (Xenopus) tropicalis Embryos

Naphthenic acids (NAs) are oil-derived mixtures of carboxylic acids and are considered emerging contaminants with the potential to disrupt development of aquatic species. In the Oil Sands Region of Canada, NAs are components of the water released following processing of the bitumen-containing sand. The aim of this research was to identify potential mechanisms of toxicity of NA mixtures. Silurana (Xenopus) tropicalis embryos were raised in water spiked with commercial oil-derived NA extracts (S1 and S2) at a sub-lethal concentration (2 mg/L). The transcriptomic responses of the whole 4-day old embryos following exposure were assessed using a custom oligonucleotide microarray. Both NA mixtures induced embryonic abnormalities that included edema, and cardiac and gut abnormalities. Exposure to NAs also affected morphometric parameters and decreased total length, tail length, and interorbital distance of the embryos. Gene ontology analysis revealed that 18 biological processes, 5 cellular components, and 19 molecular functions were significantly enriched after both S1 and S2 exposures. Sub-network enrichment analysis revealed pathways that were related to phenotypic abnormalities; these included gut function, edema, and cartilage differentiation. Other notable networks affected by NAs included metabolism and cell membrane integrity. In a separate dose-response experiment, the expression of key genes identified by microarray (cyp4b1, abcg2, slc26a6, eprs, and slc5a1) was determined by Real-Time qPCR in S. tropicalis embryos exposed to the commercial NAs and to acid-extractable organics (AEOs) prepared from Oil Sands Process-Affected Water. In general, the RT-qPCR data agreed with the microarray data. In S. tropicalis embryos exposed to the AEOs, the mRNA levels of eprs (bifunctional glutamate/proline-tRNA ligase) and slcs5a1 (sodium/glucose cotransporter 1) were significantly decreased compared to the controls. Such changes are likely indicative of increased edema and disrupted gut function, respectively. These data suggest that NAs have multiple modes of action to induce developmental toxicity in amphibians. Some modes of action may be shared between commercial NAs and AEOs.

Tolerance and cytotoxicity of naphthenic acids on microorganisms isolated from oil sands process-affected water

The expansion of oil sands has made remediation of oil sands process-affected water (OSPW) critical. As naphthenic acids (NAs) are the primary contributors to toxicity, remediation is required. Bioremediation by native microorganisms is potentially effective, however, toxicity of NAs towards native microorganisms is poorly understood. The aim of this study was to isolate microorganisms from OSPW, assess tolerance to stressors, including naturally sourced NAs and examine exposure effect of NAs on cell membranes. Microorganisms were isolated from OSPW, including the first reported isolation of a fungus (Trichoderma harzianum) and yeast (Rhodotorula mucilaginosa). Isolates tolerated alkaline pH, high salinity, and NA concentrations far exceeding those typical of OSPW indicating toxic effects of OSPW are likely the result of interactions between OSPW components. Comparisons of toxicity determined that OSPW exhibited higher cytotoxicity than NAs. The fungal isolate was able to grow using commercial NAs as its sole carbon source, indicating high resistance to NAs' cytotoxic effects. Future studies will focus on the organisms' ability to degrade NAs, and subsequent effects on toxicity. Characterization of OSPW constituents should be investigated with focus on the synergistic toxic effects of dissolved compounds. A better understanding of OSPW toxicity would enable more effective and targeted bioremediation schemes by native microorganisms.

Persistent and transgenerational effects of raw and ozonated oil sands process-affected water exposure on a model vertebrate, the zebrafish

Exposure to oil sands process-affected water (OSPW), a by-product of Canadian oil sands mining operations, can cause both acute and chronic adverse effects in aquatic life. Ozonation effectively degrades naphthenic acids in OSPW, mitigating some of the toxicological effects of exposure. In this study we examined the effect of developmental exposure to raw and ozonated OSPW had on the breeding success, prey capture, and alarm cue response in fish months/years after exposure and the transgenerational effect exposure had on gene expression, global DNA methylation, and larval basal activity. Exposure to raw and ozonated OSPW had no effect on breeding success, and global DNA methylation. Exposure altered the expression of vtg and nkx2.5 in the unexposed F1 generation. Exposure to both raw and ozonated OSPW had a transgenerational impact on larval activity levels, anxiety behaviors, and maximum swim speed compared to the control population. Prey capture success was unaffected, however, the variability in the behavioral responses to the introduction of prey was decreased. Fish developmentally exposed to either treatment were less active before exposure and did not have an anxiety response to the alarm cue hypoxanthine-3-n-oxide. Though ozonation was able to mitigate some of the effects of OSPW exposure, further studies are needed to understand the transgenerational effects and the implications of exposure on complex fish behaviors.

Transcriptome Profiling in Larval Fathead Minnow Exposed to Commercial Naphthenic Acids and Extracts from Fresh and Aged Oil Sands Process-Affected Water.

Surface mining and extraction of oil sands results in the generation of and need for storage of large volumes of oil sands process-affected water (OSPW). More structurally complex than classical naphthenic acids (NAs), naphthenic acid fraction components (NAFCs) are key toxic constituents of OSPW, and changes in the NAFC profile in OSPW over time have been linked to mitigation of OSPW toxicity. Molecular studies targeting individual genes have indicated that NAFC toxicity is likely mediated via oxidative stress, altered cell cycles, ontogenetic differentiation, endocrine disruption, and immunotoxicity. However, the individual-gene approach results in a limited picture of molecular responses. This study shows that NAFCs, from aged or fresh OSPW, have a unique effect on the larval fathead minnow transcriptome and provides initial data to construct adverse outcome pathways for skeletal deformities. All three types of processed NAs (fresh, aged, and commercial) affected the immunome of developing fish. These gene networks included immunity, inflammatory response, B-cell response, platelet adhesion, and T-helper lymphocyte activity. Larvae exposed to both NAFCs and commercial NA developed cardiovascular and bone deformities, and transcriptomic networks reflected these developmental abnormalities. Gene networks found only in NAFC-exposed fish suggest NAFCs may alter fish cardiovascular health through altered calcium ion regulation. This study improves understanding regarding the molecular perturbations underlying developmental deformities following exposure to NAFCs.

Comparison of the Effects of Extraction Techniques on Mass Spectrometry Profiles of Dissolved Organic Compounds in Oil Sand Process-Affected Water

Recent advances in mass spectrometry have facilitated chemical characterization and profiling of complex environmental mixtures such as oil sand process-affected water (OSPW) and identification of previously unresolved chemicals. However, because OSPW is a complex mixture of salts, metals, suspended particulate matter, and dissolved organics, extraction techniques are required to reduce the effects of signal suppression/enhancement. In this work, Orbitrap, ultrahigh resolution mass spectrometry was used to perform a comprehensive comparison of solid phase extraction (SPE) and liquid–liquid extraction (LLE) techniques on profiling of dissolved organic chemicals in OSPW. When operated in negative ion mode, extraction of naphthenic acid (NAs–O2) was dependent on acidification of OSPW samples for C18 and LLE techniques. However, when applying a hydrophilic lipophilic balance (HLB) sorbent (ABN) SPE technique, the extractability of NAs was independent of pH. When operated in positive ion mode, for all extracti...

Model naphthenic acids removal by microalgae and Base Mine Lake cap water microbial inoculum

Naphthenic acids (NAs) originate from bitumen and are considered a major contributor to acute toxicity in oil sands process-affected water (OSPW) produced from bitumen extraction processes. To reclaim oil sands tailings and remediate OSPW, in-pit fluid fine tailings can be water-capped as end pit lakes (EPL). Addressing NAs present in OSPW, either through removal, dilution or degradation, is an objective for oil sands reclamation. EPLs can remediate NAs through degradation or dilution or both. To assess and understand degradation potential, Chlorella kessleri and Botryococcus braunii were tested for their tolerance to, and ability to biodegrade, three model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, and cyclohexanebutyric acid). Water sourced from the industry's first EPL, the Base Mine Lake (BML), was used alone as an inoculum or co-cultured with C. kessleri to biodegrade cyclohexanecarboxylic acid and cyclohexanebutyric acid. All cultures metabolized the model compounds via β-oxidation. Biodegradation by the co-culture of C. kessleri and BML inoculum was most effective and rapid: the cyclohexaneacetic acid generated from cyclohexanebutyric acid could be further degraded by the co-culture, while the cyclohexaneacetic acid generated could not be consumed by pure algal cultures or BML inoculum alone. Adding C. kessleri greatly increased the diversity of the microbial community in the BML inoculum; many known hydrocarbon and NA degraders were identified from the 16S rRNA gene sequencing from this co-culture. This more diverse microbial community could have potential for EPL remediation.

Method for routine “naphthenic acids fraction compounds” determination in oil sands process-affected water by liquid-liquid extraction in dichloromethane and Fourier-Transform Infrared Spectroscopy

Formerly classified as naphthenic acids, “naphthenic acids fraction compounds” (NAFC) have become the subject of increasing research, in particular in view of their ubiquitous presence in the Canadian oil sands of Northern Alberta and oil sands process-affected waters (OSPW). NAFC, defined herein as the polar acid-extractable organics fraction of OSPW extractable in dichloromethane, are released into OSPW during the aqueous extraction of oil sands. A method for determining total NAFC concentration based on acidification, liquid-liquid extraction, and Fourier-Transform Infrared Spectroscopy (FT-IR) was developed by Jivraj et al. in 1995. It has become widely used in the oil sands industry for routine monitoring of NAFC. Since then, multiple variations of the method are practiced by different laboratories using different calibration materials and different extraction solvents, differences which were found to affect the results by as much as 38 and 64 percent respectively. The goal of this study was to establish a robust method for routinely quantifying NAFC that does not require complex and expensive laboratory equipment such as mass spectrometers. Described improvements include a semi-automated rolling extraction and the use of a vacuum evaporator unit to reduce the method's environmental impact. The improved FT-IR method avoids emulsions, is precise, provides good agreement with gravimetric determinations of NAFC, increases sample throughput, is inexpensive compared to MS methods, and offers a typical reporting limit of 0.1 mg kg−1. The residue recovered by this method with minimal losses can be further analyzed by MS techniques to characterize and identify individual NAFC components if desired.

Exposure to Organic Fraction Extracted from Oil Sands Process-Affected Water Has Negligible Impact on Pregnancy and Lactation of Mice.

Dissolved organic compounds are major contaminants in oil sands process-affected water (OSPW), of which naphthenic acids (NAs) are one of the main persistent toxicants. In the present study, we explore the toxic effects of the organic fraction extracted from OSPW (OSPW-OF) in mice during pregnancy and lactation. Here, we report that acute oral exposure of female Balb/c mice during gestation, and subchronic exposure throughout gestation and lactation to OSPW-OF (containing naturally occurring levels of NAs found in tailings ponds), had negligible effects on their reproductive performance. Specifically, mating behavior, pregnancy success, embryonic implantation, gestation period, litter size, and offspring viability were not affected by OSPW-OF containing up to 55 mg/L NAs. OSPW-OF exposure also did not affect plasma concentrations of pregnancy-associated hormones or pro- and anti-inflammatory cytokines, and it had minimal effects on liver stress gene expression. This study presents the first comprehensive in vivo analysis of mammalian toxicity associated with OSPW-OF exposure. Overall, our results suggest that the risk of acute and subchronic toxicity to mice exposed to OSPW-OF at environmentally relevant concentrations of NAs in contaminated drinking water is likely negligible.

Models for the acute and chronic aqueous toxicity of vanadium to Daphnia pulex under a range of surface water chemistry conditions

Alberta's oil sands petroleum coke (PC) generation has in recent years surpassed 10 million tonnes. Petroleum coke has been proposed as an industrial-scale sorbent to reduce concentrations of organic chemicals in oil sands process-affected water (OSPW). However, PC contains up to 1000 mg of vanadium (V) per kg of PC, and during the treatment it leaches from coke reaching levels of up to 7 mg/L in “treated” OSPW. Little information is available on how common water quality variables affect the toxicity of V to aquatic organisms. Here descriptive relationships are presented to describe how site-specific surface water characteristics representative of the Alberta oil sands region influence the toxicity of V to Daphnia pulex. Results revealed that when D. pulex was exposed to an increase in pH, a threshold relationship was found where acute V toxicity increased from a lethal median concentration (LC50) of 1.7 to 1.2 mg V/L between pH 6 and 7 and then levelled off at around 1 mg V/L. When alkalinity (from 75 to 541 mg/L as CaCO3) and sulphate (from 54 to 394 mg/L) increased, the acute toxicity of V decreased slightly with LC50s changing from 0.6 to 1.6, and from 0.9 to 1.4, respectively. When the length of V exposure was extended (from 2 to 21 d), only an increase of sulphate from 135 to 480 mg/L caused a slight increase in V toxicity from a LC50 of 0.6 to 0.4 mg V/L, the opposite trend seen in the acute exposures. In addition, the influence of two OSPW representative mixtures of increasing sodium and sulphate, and increasing alkalinity and sulphate on V acute toxicity to D. pulex were evaluated; only the mixture of increasing sodium (from 18 to 536 mg/L) and sulphate (from 55 to 242 mg/L) caused a slight decrease in V acute toxicity (LC50 1.0–2.1 mg V/L). Evidence is presented that variations in surface water chemistry can affect V toxicity to daphnids, although only to a small degree (i.e. within a maximum factor of 2 in all cases evaluated here). These relationships should be considered when creating new water quality guidelines or local benchmarks for V.

Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Characterization of Oil Sand Process-Affected Water in Constructed Wetland Treatment

The remediation of oil sand process-affected water (OSPW) generated during the bitumen extraction in the oil sand region of Canada is an area of ongoing research interest. One of the primary remediation challenges is the removal of residual complex organic compounds present in the OSPW. In the present study, the molecular constitution of OSPW from aerated and nonaerated wetland treatments were characterized in constructed wetland treatment systems. Negative-ion and positive-ion atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to provide extensive molecular-level analysis of the samples. Multiple aerated and nonaerated treatment wetland systems were characterized in terms of naphthenic acids (NAs), oxy-NAs, heteroatom NAs class, and double bond equivalent (DBE) versus carbon number to evaluate their molecular composition and variability. A broad range of heteroatom compound classes with variable relative abundances were identified....