Total Naphthenic Acids Research Articles

Fate of dissolved organics and generated sulfate ions during biofiltration of oil sands process water pretreated with sulfate radical advanced oxidation process

Fate of dissolved organics and sulfate ions was studied in fixed bed biofilters (FBBs) treating pre-treated oil sands process water (OSPW) in the presence of industrially relevant substrates namely petroleum coke (PC) and sand. For pre-treatment, the solar-activated sulfate radical advanced oxidation process (SR-AOP) was performed using 2.5 and 5 mM peroxymonosulfate (PMS) as a precursor with solar irradiation of 119.5 W h m−2. Excellent degradation of naphthenic acids (NAs) was attained by SR-AOP, attaining 88 % and 97 % total NAs after 9 h of treatment at 2.5 and 5 mM of PMS, respectively. However, the treatment increased the toxicity due to byproducts and metabolites following the poor removal of dissolved organics, i.e., 13 % and 21.5 %, respectively. Electron paramagnetic resonance spectrometry (EPR) analysis exhibited that hydroxyl radical (⋅OH) and singlet oxygen (1O2) were the predominant active species produced during SR-AOP. The post-treatment biofiltration improved the mineralization of dissolved organics (45 %) and NAs (99 %) as well as removed the residual toxicity (>80 %). Taxonomy-based transcriptomics analyses (RNA) confirmed the enrichment of microbes involved in the degradation of hydrocarbons and carboxylic acids, methylotrophy, and potentially C(1)-sulfur compounds metabolism. Scanning electron microscopy with energy-dispersive X-ray spectroscopy indicated the potential of PC to support sulfur deposition, but at slower rates. This study indicates that the produced water can be efficiently reclaimed by using advanced oxidation and biofiltration approaches.

Characterization of Athabasca lean oil sands and mixed surficial materials: Comparison of capillary electrophoresis/low-resolution mass spectrometry and high-resolution mass spectrometry.

Oil sands mining in Alberta, Canada, requires removal and stockpiling of considerable volumes of near-surface overburden material. This overburden includes lean oil sands (LOS) which cannot be processed economically but contain sparingly soluble petroleum hydrocarbons and naphthenic acids, which can leach into environmental waters. In order to measure and track the leaching of dissolved constituents and distinguish industrially derived organics from naturally occurring organics in local waters, practical methods were developed for characterizing multiple sources of contaminated water leakage. Capillary electrophoresis/positive-ion electrospray ionization low-resolution time-of-flight mass spectrometry (CE/LRMS), high-resolution negative-ion electrospray ionization Orbitrap mass spectrometry (HRMS) and conventional gas chromatography/flame ionization detection (GC/FID) were used to characterize porewater samples collected from within Athabasca LOS and mixed surficial materials. GC/FID was used to measure total petroleum hydrocarbon and HRMS was used to measure total naphthenic acid fraction components (NAFCs). HRMS and CE/LRMS were used to characterize samples according to source. The amounts of total petroleum hydrocarbon in each sample as measured by GC/FID ranged from 0.1 to 15.1mg/L while the amounts of NAFCs as measured by HRMS ranged from 5.3 to 82.3mg/L. Factors analysis (FA) on HRMS data visually demonstrated clustering according to sample source and was correlated to molecular formula. LRMS coupled to capillary electrophoresis separation (CE/LRMS) provides important information on NAFC isomers by adding analyte migration time data to m/z and peak intensity. Differences in measured amounts of total petroleum hydrocarbons by GC/FID and NAFCs by HRMS indicate that the two methods provide complementary information about the nature of dissolved organic species in a soil or water leachate samples. NAFC molecule class Ox Sy is a possible tracer for LOS seepage. CE/LRMS provides complementary information and is a feasible and practical option for source evaluation of NAFCs in water.

Treatment of oil sands process-affected waters using a pilot-scale hybrid constructed wetland

Constructed wetland treatment systems (CWTSs) could provide a passive, low-energy strategy for mitigating risks associated with oil sands process-affected waters (OSPWs). Due to the large volumes (over 975 million m3), heterogeneous composition, and acute and chronic toxicity of OSPW, passive and efficient treatment to decrease risks to biota will be necessary once operators obtain regulatory permission to discharge into aquatic receiving systems. The research objective was to design, assemble, and measure performance of a pilot-scale hybrid CWTS for treatment of OSPW. Constituents of concern (COCs) identified in OSPW included NAs, oil and grease, As, B, Cu, Pb, and Zn. Oxidizing conditions (net sediment redox > −50 mV) were promoted to allow aerobic degradation of organic constituents, and co-precipitation of arsenic with iron oxyhydroxides. Treatment of Cu, Pb, and Zn was targeted through precipitation with sulfides in reducing “micro-environments” in wetland sediments. Solar photocatalytic reactors (hybrid components) were used to remove recalcitrant organics. Performance was assessed using rates and extents of removal of COCs and changes in toxicity as indicated by Ceriodaphnia dubia. Mean total naphthenic acid fraction compound concentrations decreased from approximately 43 mg/L in untreated OSPW to 10 mg/L following a 16-d retention time in the hybrid CWTS. Mean As and Zn concentrations decreased from 0.026 mg/L and 0.129 mg/L in untreated OSPW to 0.011–0.014 mg/L and 0.052–0.062 mg/L in wetland outflows, respectively. Cu and Pb mass decreased by 13–26% in the CWTS; however, evaporative concentration masked removal (in terms of total metal concentrations). Toxicity (in terms of C. dubia survival and reproduction) of OSPW was eliminated following treatment. Results demonstrate that hybrid CWTSs can effectively degrade NAs and alleviate toxicity associated with metals and organics in OSPW.

Meltwater from snow contaminated by oil sands emissions is toxic to larval fish, but not spring river water

To assess the toxicity of winter-time atmospheric deposition in the oil sands mining area of Northern Alberta, embryo-larval fathead minnow (Pimephales promelas) were exposed to snowmelt samples. Snow was collected in 2011–2014 near (<7km) oil sands open pit mining operations in the Athabasca River watershed and at sites far from (>25km) oil sands mining. Snow was shipped frozen back to the laboratory, melted, and amended with essential ions prior to testing. Fertilized fathead minnow eggs were exposed (<24h post-fertilization to 7–16days post-hatch) to a range of 25%–100% snowmelt. Snow samples far from (25–277km away) surface mining operations and upgrading facilities did not affect larval fathead minnow survival at 100%. Snow samples from sites near surface mining and refining activities (<7km) showed reduced larval minnow survival. There was some variability in the potencies of snow year-to-year from 2011 to 2014, and there were increases in deformities in minnows exposed to snow from 1 site on the Steepbank River. Although exposure to snowmelt from sites near oil sands surface mining operations caused effects in larval fish, spring melt water from these same sites in late March–May of 2010, 2013 and 2014 showed no effects on larval survival when tested at 100%. Snow was analyzed for metals, total naphthenic acid concentrations, parent PAHs and alkylated PAHs. Naphthenic acid concentrations in snow were below those known to affect fish larvae. Concentrations of metals in ion-amended snow were below published water quality guideline concentrations. Compared to other sites, the snowmelt samples collected close to mining and upgrading activities had higher concentrations of PAHs and alkylated PAHs associated with airborne deposition of fugitive dusts from mining and coke piles, and in aerosols and particles from stack emissions. CapsuleSnow collected close to oil sands surface mining sites is toxic to larval fathead minnows in the lab; however spring melt water samples from the same sites do not reduce larval fish survival.

Standard method design considerations for semi-quantification of total naphthenic acids in oil sands process affected water by mass spectrometry: A review

Naphthenic acids are a complex class of thousands of naturally occurring aliphatic and alicyclic carboxylic acids found in oil sands bitumen and in the wastewater generated from bitumen processing. Dozens of analytical methods have been developed for the semiquantification of total naphthenic acids in water samples. However, different methods can give different results, prompting investigation into the comparability of the many methods. A review of important methodological features for analyzing total naphthenic acids is presented and informs the design of future standard methods for the semiquantification of total naphthenic acids using mass spectrometry. The design considerations presented are a synthesis of discussions from an Environment and Climate Change Canada (ECCC) led taskforce of 10 laboratory experts from government, industry and academia during April 2016 and subsequent discussions between University of British Columbia and ECCC representatives. Matters considered are: extraction method, solvent, pH, and temperature; analysis instrumentation and resolution; choice of calibration standards; use of surrogate and internal standards; and use of online or offline separation prior to analysis. The design considerations are amenable to both time-of-flight and Orbitrap mass spectrometers.

Investigation of dissociation constants for individual and total naphthenic acids species using ultra performance liquid chromatography ion mobility time-of-flight mass spectrometry analysis

Ultra-performance liquid chromatography ion mobility time-of-flight mass spectrometry (UPLC-IM-TOFMS) was utilized for the analysis of naphthenic acids (NAs) in fractions of pH-dependent sequential liquid-liquid extractions from oil sands process-affected water. Ion-mobility separation technique allowed the differentiation of OyS−NAs (2 ≤ y ≤ 4) from Ox−NAs (2 ≤ x ≤ 5) via drift time versus retention time separations. The results indicated that the addition of S atom to the O2−NA molecule led to a lower increase in the dissociation constant (pKa) compared to that caused by the addition of O atom. Because additional O is present as OH while the S atom is present as the CSC structure, the latter does not involve into the deprotonation process directly. The pKa value decreased along with increasing carbon number and |Z| number for O2−, O3−, O4−, and O2S−NA species, except for O5−, O3S−, and O4S−NA species, each of which are comprised of chemical structures with distinct functional groups. A calculation model was developed to estimate pKa values for individual and total NA species via nonlinear regression curve fitting, utilizing the relative abundances of detected NA species. pKa values were calculated as 3.9 for total NAs, 3.3 for O2−NAs, 4.4 for O3−NAs, 7.3 for O4−NAs, and 4.1 for O2S−NAs. Knowledge of NAs pKa is crucially important for the comprehensive understanding of their potential transformation route and toxicity as well as for the development of water remediation applications. Both the ion-mobility separation technique and the new calculation model could be widely applied for the investigation of other complicated pollutants present in water and wastewater.

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.

Specificity of high resolution analysis of naphthenic acids in aqueous environmental matrices

The effect of environmental interferences and sample container pH adjustment on total naphthenic acids is reported during application of liquid chromatography with quadrupole time-of-flight mass spectrometry detection (LC/QToF).

Trace analysis of total naphthenic acids in aqueous environmental matrices by liquid chromatography/mass spectrometry-quadrupole time of flight mass spectrometry direct injection

A rapid and sensitive liquid chromatography quadrupole time of flight method has been established for the determination of total naphthenic acid concentrations in aqueous samples. This is the first methodology that has been adopted for routine, high resolution, high throughput analysis of total naphthenic acids at trace levels in unprocessed samples. A calibration range from 0.02 to 1.0μgmL−1 total Merichem naphthenic acids was validated and demonstrated excellent accuracy (97–111% recovery) and precision (1.9% RSD at 0.02μgmL−1). Quantitative validation was also demonstrated in a non-commercial oil sands process water (OSPW) acid extractable organics (AEOs) fraction containing a higher percentage of polycarboxylic acid isomers than the Merichem technical mix. The chromatographic method showed good calibration linearity of ≥0.999 RSQ to 0.005μgmL−1 total naphthenic acids with a precision <3.1% RSD and a calculated detection limit of 0.0004μgmL−1 employing Merichem technical mix reference material. The method is well suited to monitoring naturally occurring and industrially derived naphthenic acids (and other AEOs) present in surface and ground waters in the vicinity of mining developments. The advantage of the current method is its direct application to unprocessed environmental samples and to examine natural naphthenic acid isomer profiles. It is noted that where the isomer profile of samples differs from that of the reference material, results should be considered semi-quantitative due to the lack of matching isomer content. The fingerprint profile of naphthenic acids is known to be transitory during aging and the present method has the ability to adapt to monitoring of these changes in naphthenic acid content. The method's total ion scan approach allows for data previously collected to be examined retrospectively for specific analyte mass ions of interest. A list of potential naphthenic acid isomers that decrease in response with aging is proposed and a quantitative assay of an adamantane carboxylic acid is reported.

Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Characterization of Treated Athabasca Oil Sands Processed Waters

Ultrahigh-resolution negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize Athabasca oil sands processed water (OSPW) treated by (A) coagulation flocculent with lime and bentonite, (B) coagulation flocculent with lime and bentonite followed by activated carbon, and (C) combined ozonation and ultrasonication. Treatment A was ineffective in reducing the level of total naphthenic acid fraction components [NAFCs, defined as the acid-extractable fraction of OSPWs or crude oils (CnH2n + zOwSxNy), where the values n, w, x, and y indicate the number of carbon, oxygen, sulfur, and nitrogen atoms, respectively, and z represents the hydrogen atom deficiency because of the presence of double bonds and ring formation]. Likewise, for treatment A, little or no change was observed for the double bond equivalent (DBE) distributions of the compound classes. Treatments B and C resulted in the reduction of total NAFCs by 26 ± 1.4 and 89 ± 1.1%, r...

Naphthenic acids quantification in organic solvents using fluorescence spectroscopy

Quantification of naphthenic acids in water has been traditionally performed after extraction with organic solvents followed by analytic methods that are complex and costly for preliminary research or for continuous monitoring purposes. This study examines the application of fluorescence in organic solvents as an effective alternative, and the role of organic solvents on quantification results. Nine organic solvents were used: three polar protic alcohols (methanol, ethanol, and propanol), three polar aprotic (dichloromethane, acetone, and acetonitrile) and three non-polar (hexane, toluene, and diethyl ether). The calibration curves of the polar protic solvents performed the best; they had lower light scattering and higher method sensitivity than polar aprotic and non-polar. Methanol was selected for further experiments having a strong linearity for concentrations lower than 250 mg/L (R2 > 0.99), and a low relative standard deviation (< 10%). The method sensitivity was improved by 70% using a methanol-deionized water mixture (50:50) as a solvent. The synchronous fluorescence mode with a reduced offset value of Δλ = 10 nm demonstrated potential for fingerprinting. The fluorescence technique for quantifying total naphthenic acids directly in organic solvents is a cost-effective analytical method compatible with the solid phase extraction of the sample.

Chemical fingerprinting of naphthenic acids and oil sands process waters—A review of analytical methods for environmental samples

This article provides a review of the routine methods currently utilized for total naphthenic acid analyses. There is a growing need to develop chemical methods that can selectively distinguish compounds found within industrially derived oil sands process affected waters (OSPW) from those derived from the natural weathering of oil sands deposits. Attention is thus given to the characterization of other OSPW components such as oil sands polar organic compounds, PAHs, and heavy metals along with characterization of chemical additives such as polyacrylamide polymers and trace levels of boron species. Environmental samples discussed cover the following matrices: OSPW containments, on-lease interceptor well systems, on- and off-lease groundwater, and river and lake surface waters. There are diverse ranges of methods available for analyses of total naphthenic acids. However, there is a need for inter-laboratory studies to compare their accuracy and precision for routine analyses. Recent advances in high- and medium-resolution mass spectrometry, concomitant with comprehensive mass spectrometry techniques following multi-dimensional chromatography or ion-mobility separations, have allowed for the speciation of monocarboxylic naphthenic acids along with a wide range of other species including humics. The distributions of oil sands polar organic compounds, particularly the sulphur containing species (i.e., OxS and OxS2) may allow for distinguishing sources of OSPW. The ratios of oxygen- (i.e., Ox) and nitrogen-containing species (i.e., NOx, and N2Ox) are useful for differentiating organic components derived from OSPW from natural components found within receiving waters. Synchronous fluorescence spectroscopy also provides a powerful screening technique capable of quickly detecting the presence of aromatic organic acids contained within oil sands naphthenic acid mixtures. Synchronous fluorescence spectroscopy provides diagnostic profiles for OSPW and potentially impacted groundwater that can be compared against reference groundwater and surface water samples. Novel applications of X-ray absorption near edge spectroscopy (XANES) are emerging for speciation of sulphur-containing species (both organic and inorganic components) as well as industrially derived boron-containing species. There is strong potential for an environmental forensics application of XANES for chemical fingerprinting of weathered sulphur-containing species and industrial additives in OSPW.

Impact of Ozonation on Naphthenic Acids Speciation and Toxicity of Oil Sands Process-Affected Water to Vibrio fischeri and Mammalian Immune System

Oil sands process-affected water (OSPW) is the water contained in tailings impoundment structures in oil sands operations. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. In this study, ozonation followed by biodegradation was used to remediate OSPW. The impacts of the ozone process evolution on the naphthenic acids (NAs) speciation and acute toxicity were evaluated. Ion-mobility spectrometry (IMS) was used to preliminarily separate isomeric and homologous species. The results showed limited effects of the ozone reactor size on the treatment performance in terms of contaminant removal. In terms of NAs speciation, high reactivity of NAs with higher number of carbons and rings was only observed in a region of high reactivity (i.e., utilized ozone dose lower than 50 mg/L). It was also found that nearly 0.5 mg/L total NAs was oxidized per mg/L of utilized ozone dose, at utilized ozone doses lower than 50 mg/L. IMS showed that ozonation was able to degrade NAs, oxidized NAs, and sulfur/nitrogenated NAs. Complete removal of toxicity toward Vibrio fischeri was achieved after ozonation followed by 28-day biodegradation period. In vitro and in vivo assays indicated that ozonation reduced the OSPW toxicity to mice.

Immunological impacts of oil sands-affected waters on rainbow trout evaluated using an in situ exposure

Rainbow trout were exposed in situ to oil sands-affected waters for 21d, either with or without an immune stimulation using inactivated Aeromonas salmonicida. Three aquatic systems were utilized for the experiment: a pond containing oil sands tailings capped with approximately 3m of natural surface water, a second pond where unextracted oil sands materials were deposited in the watershed, and a reservoir receiving Athabasca River water as a reference caging location. The three systems showed a gradient of oil sands-related compounds, most notably, total naphthenic acids were highest in the system containing tailings (13mg/L), followed by the system influenced by unextracted oil sands (4mg/L), followed by the reference cage location (1mg/L). Biochemical and chemical measures of exposure in rainbow trout showed the same trend, with the tailings-influenced system having the highest hepatic EROD activity and elevated bile fluorescence measured at phenanthrene wavelengths. Trout caged in the tailings-influenced location had significantly fewer leukocytes and smaller spleens as compared to the reference fish, though liver size and condition factor were unaffected. Fish in the tailings-influenced waters also demonstrated increased fin erosion, indicative of opportunistic infection. The trout exposed to tailing-influenced waters also showed a significantly decreased ability to produce antibodies to the inactivated A. salmonicida. Given the complexity of the exposure conditions, exact causative agents could not be determined, however, naphthenic acids, polycyclic aromatic hydrocarbons and pH correlate with the immunotoxic effects while elevated salinity or metals seem unlikely causes.

Microwave treatment of naphthenic acids in water

Naphthenic acids (NAs) are natural constituents of bitumen and crude oil. These compounds are concentrated as part of the oil sands process water (OSPW) during petroleum refining and separation from oil sands. NAs are considered among the major water contaminants in OSPW due to their toxicity and environmental recalcitrance. A laboratory scale microwave system was developed and experiments were conducted to determine the efficiency of NA degradation during microwave treatment. The effects of water source and quality (deionized lab water and river water) and of TiO2 catalyst in the degradation process were also investigated. Degradation kinetic parameters for both total NAs and individual z-family were calculated. The microwave system degraded OSPW NAs and commercial Fluka NAs in river water in the presence of TiO2 rapidly, producing half-life values of 3.32 and 3.61 hours, respectively. Toxicity assessments of the NA samples pre-and post-treatment indicated that the microwave system reduced overall toxicity of water containing Fluka NAs from high (5 min. IC50 v/v = 15.85%) to moderate (5 min. IC50 v/v = 36.45%) toxicity levels. However, a slight increase in toxicity was noted post-treatment in OSPW NAs.

Naphthenic acids as indicators of crude oil biodegradation in soil, based on semi‐quantitative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Crude oil contaminated soil cores were collected from a basin that contained oily solids left from three decades of oil production. Hydrocarbon biomarker analyses revealed that the soil extracts were moderately biodegraded compared with the non-degraded source oil. The degree of biodegradation also decreased with core depth (7 cm to 1 m). These data were correlated to compositional changes observed in acidic NSO-compounds that were selectively ionized and mass resolved by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Among the NSO-compounds ionized, the increase in naphthenic acid concentration (e.g., acyclic and alicyclic carboxylic acids) best correlated with the increase in biodegradation (e.g., from non-degraded to moderately degraded) as determined by the hydrocarbon biomarker analyses. The most biodegraded surface extracts (7 cm) exhibited an 80% increase in the abundance of acids relative to the source oil. Use of an internal standard allowed the semi-quantitative determination of the total naphthenic acid concentration, which decreased significantly (P < 0.05) with soil depth. Furthermore, the shift to higher double bond equivalents (DBEs), from acyclic to alicyclic acids, indicated that the increase in acids in the soil extracts was predominantly due to biotic processes. This work demonstrates the potential of ESI FT-ICR MS as a semi-quantitative tool to monitor the production of naphthenic acids during crude oil biotransformation in the environment.

Characterization of naphthenic acids in oil sands wastewaters by gas chromatography-mass spectrometry

The water produced during the extraction of bitumen from oil sands is toxic to aquatic organisms due largely to a group of naturally occurring organic acids, naphthenic acids (NAs), that are solubilized from the bitumen during processing. NAs are a complex mixture of alkyl-substituted acyclic and cycloaliphatic carboxylic acids, with the general chemical formula C n H 2 n+ Z O 2, where n is the carbon number and Z specifies a homologous family. Gas chromatography-electron impact mass spectrometry was used to characterize NAs in nine water samples derived from oil sands extraction processes. For each sample, the analysis provided the relative abundances for up to 156 base peaks, with each representing at least one NA structure. Plotting the relative abundances of NAs as three-dimensional bar graphs showed differences among samples. The relative abundance of NAs with carbon numbers ⩽21 to those in the “C22+cluster” (sum of all NAs with carbon numbers ⩾22 in Z families 0 to −12) proved useful for comparing the water samples that had a range of toxicities. A decrease in toxicity of process-affected waters accompanied an increase in the proportion of NAs in the “C22+cluster”, likely caused by biodegradation of NAs with carbon numbers of ⩽21. In addition, an increase in the proportion of NAs in the “C22+cluster” accompanied a decrease in the total NAs in the process-affected waters, again suggesting the selective removal of NAs with carbon numbers of ⩽21. This is the first investigation in which changes in the fingerprint of the NA fraction of process-affected waters from the oil sands operations has corresponded with measured toxicity in these waters.