Characterization of naphthenic acids in oil sands wastewaters by gas chromatography-mass spectrometry (original) (raw)
Related papers
2018
Concerns over the toxicity associated with 'naphthenic' acids (NA) within oil produced waters and oil sands process waters (OSPW), whether justified or not, have increased the need for the structural elucidation of NA. Certainly, oil sands mining operations, such as those in Alberta, Canada, result in the production of large volumes of OSPW contaminated with NA. Monitoring NA, predicting the toxicities and accounting for the toxicity of residual NA after clean-up treatments, have all been hindered by the lack of NA identifications. Recently, a method involving the conversion of the esters of petroleum NA to the corresponding hydrocarbons before analysis by comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS), resulted in the most comprehensive study of bicyclic NA from petroleum to date. Here, we present results of the analysis by GC×GC-MS of NA extracted from OSPW after conversion of the acids or ester derivatives to the corresponding hydrocarbons. The identifications presented include novel alicyclic, aromatic and sulphur-containing hydrocarbons and thus, by inference, of the corresponding acids. This supports and significantly extends, previous identifications of OSPW NA as their methyl esters and can now be used to better inform environmental monitoring programs and toxicity studies.
Organic Geochemistry, 2017
Concerns over the toxicity associated with 'naphthenic' acids (NA) within oil produced waters and oil sands process waters (OSPW), whether justified or not, have increased the need for the structural elucidation of NA. Certainly, oil sands mining operations, such as those in Alberta, Canada, result in the production of large volumes of OSPW contaminated with NA. Monitoring NA, predicting the toxicities and accounting for the toxicity of residual NA after clean-up treatments, have all been hindered by the lack of NA identifications. Recently, a method involving the conversion of the esters of petroleum NA to the corresponding hydrocarbons before analysis by comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS), resulted in the most comprehensive study of bicyclic NA from petroleum to date. Here, we present results of the analysis by GC×GC-MS of NA extracted from OSPW after conversion of the acids or ester derivatives to the corresponding hydrocarbons. The identifications presented include novel alicyclic, aromatic and sulphur-containing hydrocarbons and thus, by inference, of the corresponding acids. This supports and significantly extends, previous identifications of OSPW NA as their methyl esters and can now be used to better inform environmental monitoring programs and toxicity studies.
Rapid Communications in Mass Spectrometry, 2011
The oils sands industry of Canada produces large volumes of process water (OSPW) which is stored in large lagoons. The OSPW contains complex mixtures of somewhat toxic, water-soluble, acid-extractable organic matter sometimes called 'naphthenic acids' (NA). Concerns have been raised over the possible environmental impacts of leakage of OSPW and a need has therefore arisen for better characterisation of the NA. Recently, we reported the first identification of numerous individual tricyclic NA in OSPW by comprehensive two-dimensional gas chromatography/ time-of-flight mass spectrometry (GCxGC/ToF-MS) of the methyl esters. The acids were diamondoid adamantane acids, resulting, it was proposed, from biotransformation of the corresponding alkyladamantane hydrocarbons, which is a known process. Biotransformation of higher alkylated diamondoid hydrocarbons was, until now, unknown but here we describe the identification of numerous pentacyclic NA as diamantane and alkyldiamantane acids, using the same methods. Further, we suggest tentative structures for some of the tetracyclic acids formed, we propose, by ringopening of alkyldiamantanes. We suggest that this is further evidence that some of the acid-extractable organic matter in the OSPW originates from extensive biodegradation of the oil, whether in-reservoir or environmental, although other oxidative routes (e.g. processing) may also be possible. The results may be important for helping to better focus reclamation and remediation strategies for NA and for facilitating the identification of the sources of NA in contaminated environmental samples. Figure 4 . Two-dimensional mass chromatograms (contour plots) illustrating GCxGC chromatographic resolution of selected diamantane carboxylic acids (a. m/z 186 +187 b. m/z 201 c. m/z 215 methyl esters) positively (I, II) or tentatively identified in oil sands produced waters, as examined by GCxGC/ToF-MS. Colours indicate the intensities of the responses (green>yellow>pink).
Environmental science & technology, 2017
With growth of the Canadian oil sands industry, concerns have been raised about possible seepage of toxic oil sands process-affected water (OSPW) into the Athabasca River (AR). A sampling campaign in fall 2015 was undertaken to monitor for anthropogenic seepage while also considering natural sources. Naphthenic acids (NAs) and thousands of bitumen-derived organics were characterized in surface water, groundwater, and OSPW using a highly sensitive online solid phase extraction-HPLC-Orbitrap method. Elevated NA concentrations and bitumen-derived organics were detected in McLean Creek (30.1 μg/L) and Beaver Creek (190 μg/L), two tributaries that are physically impacted by tailings structures. This was suggestive of OSPW seepage, but conclusive differentiation of anthropogenic and natural sources remained difficult. High NA concentrations and bitumen-derived organics were also observed in natural water located far north of the industry, including exceedingly high concentrations in AR gr...
Effects-Directed Analysis of Dissolved Organic Compounds in Oil Sands Process-Affected Water
Environmental science & technology, 2015
Acute toxicity of oil sands process-affected water (OSPW) is caused by its complex mixture of bitumen-derived organics, but the specific chemical classes that are most toxic have not been demonstrated. Here, effects-directed analysis was used to determine the most acutely toxic chemical classes in OSPW collected from the world's first oil sands end-pit lake. Three sequential rounds of fractionation, chemical analysis (ultrahigh resolution mass spectrometry), and acute toxicity testing (96 h fathead minnow embryo lethality and 15 min Microtox bioassay) were conducted. Following primary fractionation, toxicity was primarily attributable to the neutral extractable fraction (F1-NE), containing 27% of original organics mass. In secondary fractionation, F1-NE was subfractionated by alkaline water washing, and toxicity was primarily isolated to the ionizable fraction (F2-NE2), containing 18.5% of the original organic mass. In the final round, chromatographic subfractionation of F2-NE2 ...
Environmental Science & Technology
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.
Environmental Science & Technology, 2014
Oil sands process-affected water (OSPW) is a toxic and poorly biodegradable mixture of sand, silt, heavy metals, and organics. In this study, qualitative and quantitative comparisons of naphthenic acids (NAs) were done using ultraperformance liquid chromatography time-of-flight mass spectrometry (UPLC TOF-MS), Fourier transform ion cyclotron resonance (FT-ICR) MS, and ion mobility spectrometry (IMS). The unique combination of these analyses allowed for the determination and correlation of NAs, oxidized NAs, and heteroatom (sulfur or nitrogen) NAs. Despite its lower resolution, UPLC-TOF MS was shown to offer a comparable level of reliability and precision as the high resolution FT-ICR MS. Additionally, the impacts of ozonation (35 mg/L utilized ozone dose) and subsequent NAs degradation on OSPW toxicity were assessed via a collection of organisms and toxicity end points using Vibrio fischeri (nonspecific), specific fish macrophage antimicrobial responses, and fish olfactory responses. Fish macrophages exposed to ozonated OSPW for 1 week showed higher production of reactive oxygen and nitrogen intermediates; however, after 12 weeks the responses were reduced significantly. Fish olfactory tests suggested that OSPW interfered with their perception of odorants. Current results indicate that the quantification of NAs species, using novel analytical methods, can be combined with various toxicity methods to assess the efficiency of OSPW treatment processes.
Mass spectrometric and toxicological assays of Athabasca oil sands naphthenic acids
Water Research, 2006
This work concerns the analysis of model naphthenic acids and authentic naphthenic acids from the tailings ponds of the Athabasca tar sands. A first objective was to compare atmospheric pressure chemical ionization mass spectrometry (APCI-MS) with the previously studied electrospray mass spectrometry (ESI-MS) in this analysis. APCI-MS had a wider range of quantitation than ESI-MS, but its detection limit was poorer and model compounds showed greater variation in calibration sensitivity. A second objective was fractionation of naphthenic acids from tailings pond water and analysis by the Microtox s toxicity assay. Fractionation on the basis of solubility gave fractions that did not differ significantly either in their congener distribution by ESI-MS or in their response to the Microtox assay. When partial separation was achieved by anion exchange chromatography, fractions with a higher proportion of multi-ring structures exhibited lower toxic potency. This finding is consistent with field observations that indicate that the toxic potency of tailings ponds water declines as the samples age-multiring structures are more highly branched and therefore more resistant to microbial degradation.