Naphthenic Acids Mixtures Research Articles

Solar photocatalytic degradation of model naphthenic acids mixtures by Bi2WO6 and Bi2WO6/NiO/Ag: Exploring the influence of inorganic fraction of oil sands process water

This study investigates the comparative photocatalytic degradation of six model naphthenic acids, key organic constituents responsible for the toxicity of oil sands process water, using the semiconductor photocatalysts Bi2WO6 and Bi2WO6/NiO/Ag in both buffered solution and the inorganic fraction of OSPW. The heterojunction catalyst (Bi2WO6/NiO/Ag) exhibited the highest removal efficiencies for these organic pollutants with k values 0.048, 0.036, 0.019, 0.283, 0.026, and 0.075 min−1 for 1-adamantanecarboxylic acid, cyclohexanecarboxylic acid, tetrahydropyran-4-carboxylic acid, tetrahydro-2H-thiopyran-4-carboxylic acid, isonipecotic acid, and 4,5-dihydronaphtho[1,2-b]thiophene-2-carboxylic acid, respectively. Experimental analysis suggested that chloride and bicarbonate inhibited the photocatalytic degradation of the target naphthenic acids, while nitrate could accelerate the production of aminyl radicals, enhancing the degradation of isonipecotic acid. Notably, four additional nitrated and hydroxylated by-products were identified during 1-adamantanecarboxylic acid degradation in the presence of nitrate. The addition of the catalyst not only accelerated the degradation rate of 1-adamantanecarboxylic acid but also helped mitigate the formation of potentially toxic by-products. Additionally, the transformation products of 4,5-dihydronaphtho[1,2-b] thiophene-2-carboxylic acid were identified. Degradation pathways were further elucidated with the assistance of density functional theory calculations, identifying the β-carbon as the initial reactive site, with the sulfur atom also playing a significant role in reactivity. These findings contribute to the understanding of the water matrix-induced transformation process of model naphthenic acids during photocatalytic treatment, enhancing the environmental applicability of photocatalytic treatments.

Effect of the structural characteristics of naphthenic acids on the corrosion kinetics of an AISI SAE 1005

Processing crudes with high naphthenic acid content causes corrosion problems on the crude oil distillation units. The total acid number (TAN) is commonly used to evaluate the corrosivity of crude oils; thus for decision-making related to corrosion mitigation and control in refineries. However, the TAN only represents the number of carboxylic groups present in the crude oil and does not consider the structural characteristics of the naphthenic acids, nor their reactivity, which are highly relevant to corrosion. On the other hand, the study of naphthenic acids as fractions with specific structural characteristics should enable the identification of differences in the corrosivity of crude oil with the same naphthenic acid concentration. In this research work, the fractioning of a commercial mixture of naphthenic acids was performed using the ionic strength of their respective salts. The structural characterization of the obtained fractions was conducted using Fourier-transform infrared and mass spectroscopy, gel permeation chromatography, and nuclear magnetic resonance. Furthermore, the corrosion rate of AISI SAE 1005 steel exposed to each fraction of naphthenic acids in the temperature range between 270 and 350 ºC was determined. Based on these results, a kinetic model of parallel reactions for predicting the concentration of dissolved iron in crude oil containing a mixture of naphthenic acids is proposed and validated.

Influence of interfacial responses of Berea Sandstone in low-salinity waterflooding environments

Wetting conditions and fluid–fluid interfacial properties are essential to understanding oil recovery in the context of low-salinity and smart waterflooding. Many have deemed wettability alteration to be the dominant interaction, while some highlight the importance of fluid–fluid interactions. In some rock-fluid systems, benefits from the use of additives can arise to favor hydrocarbon production. Understanding the balance between the fluid–fluid and rock-fluid interactions when utilizing additives is crucial to evaluate benefits in improved efficiency. Ultimately, this understanding will shed light on recovery mechanisms. Regarding oil recovery, previous studies indicate that the injection of a naphthenic acid (NA) blend dissolved in an injection brine improves oil recovery in Berea Sandstone, particularly under low-salinity conditions. Interfacial rheology results for the brine-oil interface correlated well with the recovery response. This observation was speculated to serve as a potential improved recovery mechanism through oil-trapping suppression. However, the said studies did not evaluate potentially concurrent rock wettability alteration during recovery or the initial wetting condition. The purpose of this work is to determine the production behavior in systems with NAs, namely NA-10 (3-Cyclohexanepropinoic acid), NA-14 (Cyclopentane carboxylic acid), NA-18 (Cyclohexane carboxylic acid), and NA-mix (Naphthenic acid mixture), at different initial wetting conditions under spontaneous imbibition. In addition, we tested the NAs ability to alter wettability in Berea Sandstone and determine each “additive’s” capacity to improve recovery. Time-domain nuclear magnetic resonance (TD-NMR), contact angle, and Amott cell tests, i.e. spontaneous imbibition, were used to analyze the influence of the selected naphthenic acids on oil displacement under different initial wetting conditions. Our results indicate that individual naphthenic acids indeed have potential as additives in low-salinity waterflooding for oil-wet systems while negatively impacting recovery in water-wet systems. However, results suggest that the evolution of the interfacial properties and wettability conditions are equally important on the recovery behavior.

Impacts of bioreactor operating parameters on removal efficiency, biodegradation rate, molecular distribution, and toxicity of commercial naphthenic acids.

Effects of naphthenic acids (NAs) concentration (50-200mg NA L-1; 35-140mg TOC L-1) and loading rate (1.4-1249mg NA L-1h-1; 1-874mg TOC L-1h-1) on removal efficiency, removal rate, and molecular distribution of NAs, and effluent toxicity were evaluated for biodegradation of commercial NAs mixture in circulating packed bed bioreactors (CPBBs). Increase of NAs concentration and loading rate (shorter residence times) increased the removal rate, while removal efficiency initially declined and then stabilized. The maximum biodegradation rates for 50, 100, 150, and 200mg NA L-1 were 128.0, 321.7, 430.2, and 630.0mg TOC L-1h-1 at loading rates of 218.5, 455.6, 673.5 and 874.0mg TOC L-1h-1, respectively, with removal efficiencies of 58.6, 70.6, 63.9 and 72.1%. Analysis of influent and treated effluents with gas chromatography-mass spectrometry showed that molecular weight and cyclicity (C and Z numbers) affected the biodegradation, with low molecular weight acyclic NAs (C = 6-12) were the most amenable to biodegradation and those with intermediate and high molecular weights (C = 13-22) and moderate cyclicity (Z = -4, -6) were the most recalcitrant. In the biofilm, Proteobacteria and Actinobacteria were the most abundant phyla, and Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the dominant classes. Toxicity analyses with Artemia salina and Vibrio fischeri (Microtox) showed that high influent concentrations and loading rates (short residence times) led to higher NAs residual concentration and effluent toxicity. To design and operate large-scale CPBBs, intermediate loading rates and residence times that result in high removal efficiency, reasonable removal rates, and low toxicity are recommended.

Isolation of tetrameric acids from naphthenates deposits and characterization by high-resolution analytical techniques

Calcium naphthenate deposits consist of an insoluble salt of polymeric structure and high interfacial activity, formed in the oil/water interface due to a specific tetrameric group of naphthenic acids containing high molecular weight (Mw, about 1230 Da), usually named ARN. These acids are made up of four carboxylic acid terminations that allow these species to cross-link with divalent cations (mainly calcium ions) present in the produced water in oil production fields. Herein, we present an alternative method of specific isolation of ARN from calcium naphthenate deposits, which includes cleaning the deposit, followed by converting naphthenate salts into organic acids (naphthenic acids (NAs) and their separation using sequential elution. For this purpose, we used silica-based with aminopropyl groups, a sorbent material previously selected. Thus, they were characterized by high-resolution analytical techniques such as NMR, ESI(–)FT-ICR MS, and ESI(–)Orbitrap MS and complementary such as FTIR. The ESI(–)FT-ICR MS results showed that the strategy provided an optimal separation of acids with a distinct Mw range. The high resolution and mass accuracy indicated that one of the fractions (fourth fraction) concentrated only the ARN species, which they were identified from their characteristic fragmentation patterns by ESI(-)MS/MS experiments, with 94.5% purity. The data from ESI(–)Orbitrap MS corroborated with the FT-ICR MS results, showing consistency in relation to the fractionation provided by the specific isolation of ARN. The integrations of the 1H and 13C NMR spectra of the acidic fractions highlighted the expressive presence of alkyl compounds and the absence of aromatic hydrogens in the subfraction of interest. Orbitrap MS offered high-resolution power and mass accuracy like FT-ICR MS, proving to be advantageous and promising and elucidating complex mixtures of naphthenic acids with an important differential in the economic viability offered by the technique.

Differential protein expression during growth on model and commercial mixtures of naphthenic acids in Pseudomonas fluorescens Pf-5.

Naphthenic acids (NAs) are carboxylic acids with the formula (C n H 2n + Z O2) and are among the most toxic, persistent constituents of oil sands process‐affected waters (OSPW), produced during oil sands extraction. Currently, the proteins and mechanisms involved in NA biodegradation are unknown. Using LC‐MS/MS shotgun proteomics, we identified proteins overexpressed during the growth of Pseudomonas fluorescens Pf‐5 on a model NA (4′‐n‐butylphenyl)‐4‐butanoic acid (n‐BPBA) and commercial NA mixture (Acros). By day 11, >95% of n‐BPBA was degraded. With Acros, a 17% reduction in intensity occurred with 10–18 carbon compounds of the Z family −2 to −14 (major NA species in this mixture). A total of 554 proteins (n‐BPBA) and 631 proteins (Acros) were overexpressed during growth on NAs, including several transporters (e.g., ABC transporters), suggesting a cellular protective response from NA toxicity. Several proteins associated with fatty acid, lipid, and amino acid metabolism were also overexpressed, including acyl‐CoA dehydrogenase and acyl‐CoA thioesterase II, which catalyze part of the fatty acid beta‐oxidation pathway. Indeed, multiple enzymes involved in the fatty acid oxidation pathway were upregulated. Given the presumed structural similarity between alkyl‐carboxylic acid side chains and fatty acids, we postulate that P. fluorescens Pf‐5 was using existing fatty acid catabolic pathways (among others) during NA degradation.

New suitable deprotonating matrices for the analysis of carboxylic acids and some acidic compounds by matrix-assisted laser desorption/ionization mass spectrometry in negative ion mode.

Direct non-derivatization analysis of organic acids and acidic compounds by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) in positive ion mode is not always possible due to the low ionization efficiency of analytes. Some new efficient deprotonating matrices were suggested that allowed the production of negative ions from acidic compounds during MALDI-MS experiments. Various tested carboxyl-containing compounds as well as compounds with acidic properties were mixed with the suggested deprotonating matrices [4-dimethylaminobenzaldehyde (DMABA), N,N-dimethylamino-p-phenylenediamine or 3-aminoquinoline] and applied on a standard MALDI target followed by recording MALDI mass spectra in negative ion mode. All the tested acidic compounds mixed with the suggested deprotonating matrices produced abundant [M - H]- ions under MALDI conditions. DMABA produced the strongest signals reflecting greater sensitivity of analysis. The suggested deprotonating matrices are commercially available compounds and are good alternatives to well-known matrices of this kind and, in particular, the often used 9-aminoacridine. DMABA is the best of the tested potential matrices and is suitable for the detection of low molecular weight carboxyl-containing compounds, substituted phenols, and mixtures of naphthenic acids by (-)MALDI-MS.

The effects of a technical mixture of naphthenic acids on placental trophoblast cell function

There is considerable concern that naphthenic acids (NA) related to oil extraction can negatively impact reproduction in mammals, yet the mechanisms are unknown. Since placental dysfunction is central to many adverse pregnancy outcomes, the goal of this study was to determine the effects of NA exposure on placental trophoblast cell function. HTR-8/SVneo cells were exposed to a commercial technical NA mixture for 24 hours to assess transcriptional regulation of placentation-related pathways and functional assessment of migration, invasion, and angiogenesis. Pathway analysis suggests that NA treatment resulted in increased epithelial-to-mesenchymal transition. However, there was reduced migration and invasive potential. NA treatment increased angiogenesis-related pathways with a concomitant increase in tube formation. Since decreased trophoblast invasion/migration and aberrant angiogenesis have been associated with placental dysfunction, these findings suggest that it is biologically plausible that exposure to NA may result in altered placental development and/or function.

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.

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.

Risks of Mixtures of Oil Sands Contaminants to a Sensitive Mayfly Sentinel, Hexagenia

Tailings ponds in northeastern Alberta, Canada contain massive amounts of oil sands process water (OSPW) that cannot currently be released due to the toxicity of some components. Limited space and the need for reclamation of oil sands operation sites will necessitate the release of OSPW in the near future. Knowledge of the composition and toxicity of OSPW is lacking yet is crucial for both risk assessment and management planning. This study examines chronic toxicity of a mixture of OSPW components sodium naphthenate and naphthenic acid (NA) to nymphs of the mayfly Hexagenia spp. in control and polycyclic aromatic hydrocarbons (PAH)-spiked sediment treatments. The objective of this study was to determine whether the addition of the PAH-spiked sediment significantly contributed to or masked responses of these sensitive mayflies to mixtures of NA. Mean survival in nymphs exposed to NA and PAH-spiked sediment treatments was reduced by 48% compared to those exposed to the NA mixture alone. Lethal responses were observed in all of the PAH-spiked sediment treatments. However, within PAH-spiked and control sediment treatments, there was no significant difference in nymph survival due to NA concentration, indicating that changes in survivorship were predominantly a reflection of increased mortality associated with sediment PAHs and not to the NA mixture treatment. Sublethal effects on body segment ratios suggest that mayflies exposed to NA and PAH-spiked sediment, as well as those exposed to the highest NA concentration tested (1 mg/L) and control sediment, made developmental trade-offs in order to emerge faster and escape a stressful environment. These results reveal that the release of OSPW to the surrounding environment could cause a reduction in mayfly populations. Mayflies provide ecosystem services and are an important food source for higher trophic levels in both the aquatic and terrestrial communities.

Electro-oxidation by graphite anode for naphthenic acids degradation, biodegradability enhancement and toxicity reduction

Electro-oxidation (EO) by using graphite anode and at relatively low current densities was successfully applied for the degradation of commercial naphthenic acids (NAs) mixture in water samples. At current densities of 0.5, 2.5, and 5 mA/cm2, acid extractable fraction (AEF) was removed by 42.2%, 57.0% and 67.9%, respectively, while classical NAs were degraded by 76.9%, 77.6% and 82.4%, respectively. EO reactivity towards NAs increased with increasing the carbon number (n) and was higher for cyclic NAs compared to the acyclic component. Oxidized NAs containing O3 and O4 were also degraded effectively during EO. The biodegradability of organics in the NA mixture was clearly improved by 1.7, 2.5 and 2.7 folds when the samples were pre-treated with EO at current densities of 0.5, 2.5, and 5 mA/cm2, respectively. The aromatic fraction in the commercial NA mixture consisted mainly of single-ring aromatics and was degraded effectively by EO. Biodegradation alone was able to reduce the toxicity of the commercial NA mixture towards Vibrio fischeri; however, the combination of EO with biodegradation resulted in a complete removal of the toxicity, showing a synergistic effect of combining these two processes. Coupling EO with aerobic biodegradation can result in an effective and energy-efficient treatment option for NA-bearing waters such as oil sands process water (OSPW) and refinery effluents.

Equilibrium Partitioning of Naphthenic Acid Mixture Part 2: Crude Oil-Extracted Naphthenic Acids

Crude oil naphthenic acids can partition into the water phase during oil production. Variations in production parameters such as temperature, pressure, pH, and water cut affect partitioning. In a previous article, a method was developed to determine the partition ratio for mixtures of naphthenic acids and tested on a commercial acid mixture. In this study, the method is implemented on a naphthenic acid mixture extracted from an acidic crude oil. Compositional analysis of the extracted acid mixture reveals a broad structural distribution consisting mainly of saturated ring structures with 2 to 3 rings. Examination of the GC/MS method revealed a distribution bias toward low molecular weight compounds, and a correction method was explained and applied. The equilibrium partitioning as a function of pH for the acid mixture and molecular mass ranges within the acid mixture was determined by GC/MS. An extracted crude oil acid mixture dissolved in toluene was used as oil phase, and 3.5 wt % NaCl aqueous buffers were used as water phase. Dividing the acid mixture into molecular weight ranges, characterized by a single partition ratio Pwo allowed the oil–water partitioning to be successfully modeled. The variation of the cologarithm of the partition ratio pPwo with naphthenic acid molecular weight was compared with previously published experimental and simulated data. The presence of calcium reduced the partitioning of the acid mixture at high pH for larger acid molecules. Analysis of the resulting oil phase revealed a calcium content consistent with oil-soluble calcium naphthenate in agreement with results found for a commercial acid mixture.

Investigation of isomeric structures in a commercial mixture of naphthenic acids using ultrahigh pressure liquid chromatography coupled to hybrid traveling wave ion mobility-time of flight mass spectrometry

The separation of isomeric naphthenic acids (NAs) is of high importance to obtain more detailed and therefore useful information to understand their fate, transport, toxicity and potential removal treatment methodologies. In the current study, the capabilities of the ultrahigh pressure liquid chromatography/traveling wave ion mobility-time of flight mass spectrometry (UPLC/TWIM-TOF-MS) to separate and study different isomeric structures of NAs were investigated. Fifty seven standard compounds belonging to different chemical families of classical NAs were analyzed to obtain their experimental drift times in addition to chromatographic retention time and mass-to-charge information (m/z). These acyclic and cyclic molecules yielded ions with collision cross section (CCS) values ranging from 110 to 210 Å2. The feasibility of the UPLC/TWIM-TOF-MS method to provide a higher degree of confidence in the identification of isomeric structures was evaluated by analyzing the commercial (Sigma-Aldrich) NAs mixture. Identification and structure confirmation of several alicyclic compounds of similar m/z in the NAs mixture were possible by this method. For instance, the presence of previously tentatively identified compounds by the ultrahigh pressure liquid chromatography/quadrupole time of flight mass spectrometry (UPLC/QTOF-MS), such as 4-tert-butylcyclohexanoic acid, 4-dicyclohexylacetic acid or 3,5-dimethyladamantane-1-carboxylic acid, was confirmed. Combining ion mobility separation with UPLC/TOF-MS gives a higher level of selectivity to the overall method by selective interrogation of specific retention time, mass-to-charge and mobility regions. However, there are cases where it is not possible to resolve many similar molecules such as acyclic isomeric compounds in commercial NAs mixture by this technique. This was likely due to the very small CCS area differences among the structural isomeric species. Considerable improvements in the ion mobility resolution and separation will be required for this technique to be able to resolve isomeric species with slight differences in physicochemical properties (e.g., size and structure).

Equilibrium Partitioning of Naphthenic Acid Mixture, Part 1: Commercial Naphthenic Acid Mixture

Crude oil contains naphthenic acids that can partition into water. This phenomenon is a function of several parameters, such as the naphthenic acid composition, pH, and water phase salinity. This article is a continuation of previous work regarding the partitioning between oil and water of model acids and bases in model systems, with regard to pH and salinity. The present work will focus on a commercial naphthenic acid mixture from Fluka, while the next work will deal with extracted naphthenic acids from a crude oil. The composition of the acid mixture was determined by GC/MS and it was found that the commercial naphthenic acid mixture is mostly composed of saturated acids with 0–3 ring structures. The partitioning of the commercial naphthenic acid mixture was determined. The equilibrium partitioning of acids with different molecular weight was determined over a large pH interval, using toluene as the oil phase and 3.5 wt % NaCl aqueous buffers as the water phase. The partitioning of the naphthenic acid m...

Electrochemical mineralization and detoxification of naphthenic acids on boron-doped diamond anodes.

Electrochemical oxidation (ELOX) with boron-doped diamond (BDD) anodes was successfully applied to degrade a model aqueous solution of a mixture of commercial naphthenic acids (NAs). The model mixture was prepared resembling the NA and salt composition of oil sands process-affected water (OSPW) as described in the literature. The initial concentration of NAs between 70 and 120mg/L did not influence the electrooxidation kinetics. However, increasing the applied current density from 20 to 100A/m2 and the initial chloride concentration from 15 to 70 and 150mg/L accelerated the rate of NA degradation. At higher chloride concentration, the formation of indirect oxidative species could contribute to the faster oxidation of NAs. Complete chemical oxygen demand removal at an initial NA concentration of 120mg/L, 70mg/L of chloride and applied 50A/m2 of current density was achieved, and 85% mineralization, defined as the decrease of the total organic carbon (TOC) content, was attained. Moreover, after 6h of treatment and independently on the experimental conditions, the formation of more toxic species, i.e. perchlorate and organochlorinated compounds, was not detected. Finally, the use of ELOX with BDD anodes produced a 7 to 11-fold reduction of toxicity (IC50 towards Vibrio fischeri) after 2h of treatment.

Toxicity of naphthenic acids to invertebrates: Extracts from oil sands process-affected water versus commercial mixtures

The toxicity of oil sands process-affected water (OSPW) has been primarily attributed to polar organic constituents, including naphthenic acid fraction components (NAFCs). Our objective was to assess the toxicity of NAFCs derived from fresh and aged OSPW, as well as commercial naphthenic acid (NA) mixtures. Exposures were conducted with three aquatic species: Hyalella azteca (freshwater amphipod), Vibrio fischeri (marine bacterium, Microtox® assay), and Lampsilis cardium (freshwater mussel larvae (glochidia)). Commercial NAs were more toxic than NAFCs, with differences of up to 30-, 4-, and 120-fold for H. azteca, V. fischeri, and L. cardium, respectively, demonstrating that commercial NAs are not reliable surrogates for assessing the toxicity of NAFCs. Differences in toxicity between species were striking for both commercial NAs and NAFCs. Overall, V. fischeri was the least sensitive and H. azteca was the most sensitive organism. Responses of V. fischeri and H. azteca to NAFC exposures were consistent (< 2-fold difference) regardless of source and age of OSPW; however, effects on L. cardium ranged 17-fold between NAFCs. NAFCs derived from fresh OSPW sources were similarly or less toxic to those from aged OSPW. Our results support the need to better characterize the complex mixtures associated with bitumen-influenced waters, both chemically and toxicologically.

An investigation of the immunotoxicity of oil sands processed water and leachates in trout leukocytes

Increased oil sands (OS) mining activity has raised concerns about impacts on aquatic organisms. This study sought to examine the effects of single representative compounds from OS (benzo(a)pyrene, naphthalene), a mixture of naphthenic acids (NAs), OS-processed water (OSPW) and OS leachate (OSL) extracts on rainbow trout leukocytes. Primary cultures of trout leukocytes were exposed to increasing concentrations of benzo(a)pyrene, naphthalene, NAs, OSPW and OSL for 48h at 18°C. Immunocompetence was followed by measuring changes in lymphocyte and macrophage viability and phagocytosis. Changes in the expression of 10 transcripts were also followed: interleukin 1, 2 and 6 (Il-1, Il-2 and Il-6), calreticulin (CRT), caspase 9 (Cas9), aryl hydrocarbon receptor (AhR), cyclooxygenase-2 (COX2), glutathione S-transferase (GST), catalase (CAT) and p53 tumor suppressor. The results revealed that exposure to OSPW extracts decreased the capacity of macrophages to engulf three beads or more, while the other compounds generally increased phagocytosis activity. Lymphocyte apoptosis was increased by all compounds and mixtures except naphthalene. Both OSPW and OSL induced apoptosis in macrophages. At the gene expression level, Cas9, CRT, Il-1 (inhibition) and Il-2 were specifically influenced by OSPW, while CAT, p53, COX2 and Il-1 (induction) transcripts were specifically expressed by OSL. Leukocyte exposure to OSPW produced characteristic changes in immunocompetence and genes involved in proinflammatory, apoptosis and protein damage (CRT) pathways which could not be explained by OSL, benzo(a)pyrene, naphthalene and NA mixture.

A traceable reference for direct comparative assessment of total naphthenic acid concentrations in commercial and acid extractable organic mixtures derived from oil sands process water

ABSTRACTThe advantage of using naphthenic acid (NA) mixtures for the determination of total NA lies in their chemical characteristics and identification of retention times distinct from isobaric interferences. However, the differing homolog profiles and unknown chemical structures of NA mixtures do not allow them to be considered a traceable reference material. The current study provides a new tool for the comparative assessment of different NA mixtures by direct reference to a single, well-defined and traceable compound, decanoic-d19 acid. The method employed an established liquid chromatography time-of-flight mass spectrometry (LC/QToF) procedure that was applicable both to the classic O2 NA species dominating commercial mixtures and additionally to the O4 species known to be present in acid extractable organics (AEOs) derived from oil sands process water (OSPW). Four different commercial NA mixtures and one OSPW-derived AEOs mixture were comparatively assessed. Results showed significant difference among Merichem Technical, Aldrich, Acros, and Kodak commercial NA mixtures with respect to “equivalent to decanoic-d19 acid” concentration ratios to nominal. Furthermore, different lot numbers of single commercial NA mixtures were found to be inconsistent with respect to their homolog content by percent response. Differences in the observed homolog content varied significantly, particularly at the lower (n = 9–14) and higher (n = 20–23) carbon number ranges. Results highlighted the problem between using NA mixtures from different sources and different lot numbers but offered a solution to the problem from a concentration perspective. It is anticipated that this tool may be utilized in review of historical data in addition to future studies, such as the study of OSPW derived acid extractable organics (AEOs) and fractions employed during toxicological studies.

Analysis of naphthenic acid mixtures as pentafluorobenzyl derivatives by gas chromatography-electron impact mass spectrometry

In this study, we report for the first time the efficiency of pentafluorobenzyl bromide (PFBBr) for naphthenic acid (NA) mixtures derivatization, and the comparison in the optimal conditions to the most common NAs derivatization reagents, BF3/MeOH and N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA). Naphthenic acids are carboxylic acid mixtures of petrochemical origin. These compounds are important for the oil industry because of their corrosive properties, which can damage oil distillation infrastructure. Moreover, NAs are commercially used in a wide range of products such as paint and ink driers, wood and fabric preservatives, fuel additives, emulsifiers, and surfactants. Naphthenic acids have also been found in sediments after major oils spills in the United States and South Korea. Furthermore, the toxicity of the oil sands process-affected water (OSPW), product of the oil sands extraction activities in Canada's oil sands, has largely been attributed to NAs. One of the main challenges for the chromatographic analysis of these mixtures is the resolution of the components. The derivatization optimization was achieved using surface response analysis with molar ratio and time as factors for derivatization signal yield. After gas chromatography-electron impact mass spectrometry (GC/EIMS) analysis of a mixture of NA standards, it was found that the signal produced by PFB-derivatives was 2.3 and 1.4 times higher than the signal produced by methylated and MTBS-derivatives, respectively. The pentafluorobenzyl derivatives have a characteristic fragment ion at 181m/z that is diagnostic for the differentiation of carboxylic and non-carboxylic acid components within mixtures. In the analysis of a Sigma and a Merichem derivatized oil extract NA mixtures, it was found that some peaks lack the characteristic fragment ion; therefore they are not carboxylic acids. Open column chromatography was used to obtain a hexane and a methanol fraction of the Sigma and Merichem mixtures. The components in the hexane fraction, presumably hydrocarbons that did not react with PFBBr were ~7% by weight. The effectiveness of PFBBr was confirmed when the two NA oil extracts were spiked with 8 distinct NA standards and identified by GC/EIMS in the methanol fraction. Here, we also report retention indices of the methyl, MTBS and PFB derivatives of these 8 NAs. The use of PFBBr increases sensitivity, chromatographic resolution, and identification accuracy for the analysis of standards and mixtures of NAs compared to MTBSTFA and BF3/MeOH. This methodology will have wide applications in the elucidation of NA mixtures.