Characterization of Naphthenic Acids and Other Dissolved Organics in

Jul 20, 2017 - (6, 7) In 2013, tailings ponds covering 220 km2 contained 975 million m3 of fine fluid tailings and OSPW.(8) Some of the oldest tailing...
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Characterization of Naphthenic Acids and Other Dissolved Organics in Natural Water from the Athabasca Oil Sands Region, Canada Chenxing Sun,† William Shotyk,‡ Chad W. Cuss,‡ Mark W. Donner,‡ Jon Fennell,§ Muhammad Javed,‡ Tommy Noernberg,‡ Mark Poesch,‡ Rick Pelletier,‡ Nilo Sinnatamby,‡ Tariq Siddique,‡ and Jonathan W. Martin*,† †

Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta Canada, T6G 2G3 Department of Renewable Resources, University of Alberta, Edmonton, Alberta Canada, T6G 2H1 § Integrated Sustainability Consultants Ltd., Calgary, AB Canada T2P 2Y5 ‡

S Supporting Information *

ABSTRACT: 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 groundwater (A5w-GW, 2000 μg/L) and elevated concentration in a tributary river (Pierre River, 34.7 μg/L). Despite these evidence for both natural and anthropogenic seepage, no evidence of any bitumen-derived organics was detected at any location in AR mainstem surface water. The chemical significance of any bitumen-derived seepage to the AR was therefore minimal, and focused monitoring in tributaries will be valuable in the future.

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or conversion to end-pit lakes,10 and OSPW in these structures may be connected to natural waters by surface or groundwater flow. Fresh OSPW is toxic to aquatic organisms4,11 due to a complex mixture of dissolved organics, including naphthenic acids (NAs) and other water-soluble organic compounds derived from natural bitumen.12 NAs are a supercomplex mixture of organic carboxylic acid isomers in crude oils with the general formula of CnH2n+ZO2, where n represents the carbon number, and Z specifies the degree of unsaturation or number of rings.13 NAs become concentrated in tailings ponds due to their persistence14 and continued OSPW recycling.15 A recent effects-directed analysis attributed the toxicity to a range of compound classes, including NAs and nonacidic polar neutral compounds containing oxygen (i.e., CxHyO2), sulfur (CxHySO), or nitrogen (CxHyNO).16 Follow up studies have recently demonstrated that these same compound classes are lipophilic,

INTRODUCTION The Athabasca oil sands region (AOSR) of northeastern Alberta is a vast area (142 000 km2) containing among the largest petroleum reserves in the world. This petroleum is in the form of bitumen, and the reserves are estimated to be equivalent to 170 billion barrels of crude oil.1 The ore may be termed oil sands or tar sands, depending on the viscosity of the material,2 but in this paper the term oil sands is used for simplicity. The Athabasca River (AR) and its tributaries are major surface features in the AOSR, with water flowing north to the Peace-Athabasca Delta, a UNESCO world heritage site.3 The AR and some of its tributaries flow adjacent to major oil sands surface mines, raising concerns about contamination of natural water.4,5 At oil sands surface mines, large volumes of hot water are used to extract viscous bitumen from the raw ore, resulting in acutely toxic oil sands process-affected water (OSPW) that is stored in large settling basins, known as tailings ponds.6,7 In 2013, tailings ponds covering 220 km2 contained 975 million m3 of fine fluid tailings and OSPW.8 Some of the oldest tailings ponds have now entered reclamation by dry-landscape capping9 © XXXX American Chemical Society

Received: April 21, 2017 Revised: June 21, 2017 Accepted: July 10, 2017

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DOI: 10.1021/acs.est.7b02082 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology and some can bioconcentrate in fish.17 In 2014 we reported the NA concentrations and fingerprints in surface water and groundwater samples from the AOSR,18 but comparably little is known about the occurrence of these other toxic and potentially bioaccumulative nonacidic compounds. The development of new analytical methods and their application to water monitoring for this broader range of bitumen-derived organics may assist in understanding current aquatic toxicological risks. Furthermore, these advancements of analytical methods will also help with the environmental forensic challenge of differentiating natural bitumen-derived impacts from anthropogenic ones. The AR cuts into distinct geological formations as it flows past surface mining activity, including the Cretaceous Clearwater, McMurray, and underlying Devonian formations.19 Natural outcropping of oil sands in the McMurray formation can be seen on the banks of the river between Fort McMurray and the Firebag River. While natural seepage of bitumenimpacted water is known to occur, the magnitude and significance of this natural contamination to the AR is not understood. Upwelling of saline groundwater into the AR has been characterized by electromagnetic surveys and by piezometer measurements,19 but the measured presence of salinity and major ions alone does not allow bitumen-impacted water (i.e., from the McMurray formation which contains bitumen) to be distinguished from saline non bitumenimpacted groundwater originating from the underlying Devonian. Characterization of the dissolved organic compounds in natural bitumen-impacted water has not been studied as extensively as in OSPW, and it is not yet clear how to distinguish natural and anthropogenic sources of bitumenderived organics in water samples. Advanced analytical techniques for analysis of bitumen-impacted water have shown promise,18,20−31 in particular comprehensive twodimensional gas chromatography (GC×GC/MS),30,31 ion mobility mass spectrometry32 and methods based on ultrahigh-resolution mass spectrometry (HRMS), such as Orbitrap MS24,25,29 and Fourier transform ion cyclotron resonance MS (FTICR-MS).20,26,33 For instance, Headley et al. used FTICRMS to profile OSPW and natural water and suggested that the relative abundance of sulfur-containing acid species could potentially be used for source discrimination.33 Gibson et al. combined FTICR-MS data with isotopic and geochemical tracers for fingerprinting OSPW and seep samples, but identification of sources still remained a challenge.34 Frank et al. suggested seepage of OSPW via groundwater into the AR using a tiered approach including HRMS and GC×GC-MS.22 Ross et al. measured NA fingerprints in the AR mainstem, tributaries, lakes, and in natural bitumen-impacted groundwater by HPLC/QTOF-MS.18 Although they reported similarities in NA fingerprints between OSPW and two tributaries, conclusive distinction of anthropogenic and natural sources could not be made. It also must be noted that most analytical measurements of dissolved organics in natural surface water and groundwater in the AOSR have only used negative ionization mode, and thus were limited to detection of organic acids. Only one study, by Barrow et al.,20 used both negative and positive mode together to characterize organic compounds in OSPW, tributary rivers, and groundwater. On the basis of this limited survey they nevertheless suggested that sulfur-containing species (with no oxygen), as well as hydrocarbons, both of which were only

observed in atmospheric pressure photo ionization positive mode have potential for screening oil sands impacted samples. In the present study, a sensitive and robust method was developed for natural waters using in-line solid phase extraction (SPE) coupled to HPLC-Orbitrap MS. Each water sample was analyzed in both positive and negative mode, with atmospheric pressure chemical ionization for profiling of organic acids and polar nonacids in a wide survey of surface water, groundwater, and OSPW from the AOSR. The objectives were to examine the range of NA concentrations while simultaneously profiling thousands of other organic species in an effort to maximize information for forensics and environmental risk assessment.

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MATERIALS AND METHODS Sample Collection. The focus of this work is on a total of 40 water samples collected in the fall of 2015. These included eight groundwaters, thirty-one surface waters from the AR or its tributaries, and one lake water. The smaller set of natural water samples were also collected in the fall of 2014. Six OSPW from different active tailings ponds were also included in this study to contrast with natural water samples. Detailed water sampling procedures and sample preparation are described in the Supporting Information (SI). Instrumental Analysis of Organic Compounds. Five milliliters of filtered water from each sample was directly injected to in-line SPE-HPLC/Orbitrap MS system. Detailed analysis procedures are described in the SI. Data Processing and Statistical Analysis. Data acquisition and analysis were performed with Thermo Xcalibur 2.2 software. Under each ionization mode for each sample, mass spectra between 7 and 24 min of the total ion chromatograms were averaged to generate lists of m/z with corresponding intensities. These lists were refined by blank subtraction using field blank data, and only peaks with signal/noise ratio ≥10 were used for further data analysis. Empirical formula assignments were based on the following elemental restrictions: C4−30, H6−100, N0−2, S0−2, O0−10. All species were binned into major heteroatomic classes under negative ionization mode, for example Ox−, NOx−, N2Ox−, S(1−2)−, SOx−, S2Ox−, NSOx−, and also under positive ionization mode, for example Ox+, NOx+, N2Ox+, S(1−2)+, SOx+, NSOx+. The relative contribution of each heteroatomic class in each sample was calculated as the sum intensity of all species in the class divided by total intensity of all species in the sample under negative and positive ionization, respectively. Principal component analysis (PCA) was first conducted on the organic profile under negative ionization using relative contributions of the heteroatomic classes that were further transformed using log10(x + 0.78) (log10 b + log10 (Xmaximum + b) = 0 to get b value). A separate PCA was conducted using relative contributions of the heteroatomic classes in positive ionization that were transformed using log10(x + 0.86). PCA was performed using XLSTAT (V2016.4, Addinsoft, Paris, France). NA Concentrations and Fingerprints. Identification of NA (CnH2n+ZO2) species was based on accurate mass measurement to within 3 ppm of the theoretical masses for NAs with n = 9−24 and Z= 0 to −20. In this study, Z = 0 species and two major Z = −2 species (n = 16 and 18) were eliminated from all data sets, because these species are dominated by biological fatty-acids that are detectable at high concentrations in all samples, including those upstream of oil sands activity.18 The relative contribution of each NA species in each sample was calculated as the intensity of each NA species B

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Figure 1. Map of study area showing surface water and groundwater sampling locations. The size of the circle at each location is proportional to the measured naphthenic acid (NA) concentration. Locations of tailings ponds containing OSPW are shown as Wet Tailings.

GW, NSS, FMSS, and Saline Spring) all grouped relatively close to OSPW in the Piper plot (Figure S1). Tritium measurements in groundwater were as follows: A18GW (6.1 TU), A17-GW (11.8 TU), A16-GW (6.5 TU), A15GW (7.1 TU), Saline Spring (1.4 TU), A5w-GW (0.9 TU), NSS ( O+ > O3+, which was similar to the SOx+ classes, whereby SO2+ > SO+ > SO3+. The enrichment of sulfurcontaining classes was also observed in the bitumen-impacted tributaries, such as Beaver Creek and McLean Creek, but not in AR surface water. As in negative ionization mode, the heteroatomic profiles of the AR mainstem were very similar upstream, downstream (Figure S4b) and in the vicinity of oil sands industry (A18w-River, Figure 3b). No trend or significant changes in the absolute abundance of these heteroatom classes were observed in the AR mainstem moving through the oil sands industrial zone. PCA of Organic Profile under Negative and Positive Ionization. PCA analysis was first conducted on the heteroatomic profiles detected under negative ionization (Figure 4a). The AR mainstem samples grouped separately with positive loading on PC1, driven to a great extent by the high relative abundance of the multioxygenated classes O(3−8)− as well as N2Ox− and NOx− (Figure 4c); as discussed, these are likely components of natural dissolved organic carbon of contemporary biological origin. In contrast, OSPW and natural bitumen-impacted groundwater (A5w-GW and NSS) plotted with strong negative loading on PC1 (Figure 4a), driven by the high relative abundance of NAs (O2−) and many sulfur containing acids (SO(2−4)−) (Figure 4c). Groundwater samples spread out the most on both PC1 and PC2 axes (Figure 4a), reflecting the high variability in the organics composition for this sample type. A17w-GW and A16w-GW clustered close to tributary water samples. A18w-GW also plotted closer to the tributary samples than to OSPW, even though it had a bitumenimpacted NA fingerprint. FMSS, A15-GW and Saline Spring plotted between natural surface water and OSPW, while A5wGW and NSS were well separated on PC1 from AR water and from most of the tributary waters. Similar PCA results were presented by Gibson et al.,34 in which one groundwater plotted very close to Shell Albian OSPW, despite that this groundwater was collected 50 km upstream from the tailings pond. Most tributary rivers overlapped with AR surface water, but were more variable, generally spreading out more on the PC2 axis (Figure 4a). McLean Creek and Beaver Creek were the exceptions, and the only tributary samples with negative loadings on PC1, plotting closer to OSPW and natural bitumen-impacted water. A separate PCA analysis was conducted on the heteroatomic profiles detected in positive ionization (Figure 4b). Similar to negative mode (Figure 4a), all AR mainstem samples still grouped together and were well separated from OSPW and natural bitumen-impacted groundwater (A5w-GW and NSS). This separation was mainly driven by the high relative abundance of the multioxygenated classes O(3−8)+ and NSO+ in AR mainstem, as well as sulfur containing compounds (SO(1−4)+,S(1−2)+) in bitumen-impacted samples (Figure 4d). G

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Zubot from Syncrude for providing oil sands water samples; Tracy Gartner for financial administration.

the AR watershed, not only for forensic purposes but also for the potential of natural sources to cause biological effects. Having said the above, the conclusion that comes from simultaneous monitoring of AR surface water adjacent to bitumen-impacted groundwater or tributaries was that in no location could we detect the characteristic signal of bitumenderived organics in the AR mainstem. This was true even with the highly sensitive analytical method used here, and even in the surface water zone (i.e., A5w-ARW) where A5w-GW was shown to have exceptionally high concentrations of acutely toxic NAs and SO+ compounds. This suggests that the flux of this naturally impacted groundwater into the river was low, relative to the high flow rate of the river, even during this sampling campaign in the fall when surface water flow rates are the lowest. It has been reported that average (over 76 months) saline groundwater flow into AR is between 0.05% and 0.19% of total river discharge.19 Even if the extreme case is assumed here that all the 0.19% of river discharge is from A5w-GW (NA 2000 μg/L), then the NA concentration in the river after mixing would be approximately 3 μg/L, which is only slightly above the LOD of our method (2 μg/L). Thus, the chemical significance of any bitumen-derived seepage to the AR is of low general concern today, irrespective of whether the sources are anthropogenic or natural. Future monitoring and environmental forensic work could focus on seepage into tributaries, with less emphasis on the AR mainstem where dilution is so high. Owing to elevated NA concentrations and compositional profiles similar to OSPW, Beaver Creek and McLean Creek continue to be areas of concern. Although their chemical impact on the AR was not measurable in this sampling campaign, best efforts at controlling any seepage here should be considered by companies and relevant authorities.

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(1) Canada’s Oil Sands-Opportunities and Challenges to 2015: An Update; National Energy Board: Calgary, AB, Canada, 2006. (2) Shotyk, W.; Appleby, P. G.; Bicalho, B.; Davies, L.; Froese, D.; Grant-Weaver, I.; Krachler, M.; Magnan, G.; Mullan-Boudreau, G.; Noernberg, T.; Pelletier, R.; Shannon, B.; van Bellen, S.; Zaccone, C. Peat bogs in northern Alberta, Canada reveal decades of declining atmospheric Pb contamination. Geophys. Res. Lett. 2016, 43 (18), 9964−9974. (3) Environmental Canada. Daily discharge data for Athabasca River. https://wateroffice.ec.gc.ca/report/historical_e.html?stn= 07DA001&mode=Table (Accessed January 19, 2017). (4) Kindzierski, W.; Jin, J.; Gamal El-Din, M. Review of Health Effects of Naphthenic Acids: Data Gaps and Implications for Understanding; Oil Sands Research and Information Network, University of Alberta, School of Energy and the Environment: Edmonton, Alberta, 2012, No. TR-20, 43. (5) Royal Society of Canada. Environmental and Health Impacts of Canada’S Oil Sands Industry; Royal Society of Canada Expert Panel: Ottawa, ON, Canada. 2010. (6) Schramm, L. L.; Stasiuk, E. N.; MacKinnon, M., Eds. Surfactants, Fundamentals and Applications in the Petroleum Industry; Cambridge University Press: Cambridge, UK, 2000. (7) Alberta’s Energy Reserves 2008 and Supply/Demand Outlook 2009−2018, ST98−2009; Energy Resources Conservation Board: Calgary, AB, Canada, 2009. (8) Government of Alberta. Environment and Sustainable Resource Development. Tailings ponds, oil sands tailings ponds locations. http://osip.alberta.ca/map/ (Accessed September 20, 2016). (9) Suncor. Pond 1 reclamation. http://sustainability.suncor.com/ 2010/en/responsible/3508.aspx (Accessed on October 14, 2016). (10) Syncrude. Water capping. http://www.syncrude.ca/ environment/tailings-management/tailings-reclamation/watercapping/ (Accessed October 11, 2016). (11) MacKinnon, M. D.; Boerger, H. Description of two treatment methods for detoxifying oil sands tailings pond water. Water Qual. Res.. J. Canada 1986, 21, 496−512. (12) Allen, E. W. Process water treatment in Canada’s oil sands industry: I. Target pollutants and treatment objectives. J. Environ. Eng. Sci. 2008, 7, 123−138. (13) Frank, R. A.; Kavanagh, R.; Kent Burnison, B.; Arsenault, G.; Headley, J. V.; Peru, K. M.; Van Der Kraak, G.; Solomon, K. R. Toxicity assessment of collected fractions from an extracted naphthenic acid mixture. Chemosphere 2008, 72 (9), 1309−1314. (14) Han, X.; MacKinnon, M. D.; Martin, J. W. Estimating the in situ biodegradation of naphthenic acids in oil sands process waters by HPLC/HRMS. Chemosphere 2009, 76, 63−70. (15) Brown, L. D.; Ulrich, A. C. Oil sands naphthenic acids: A review of properties, measurement and treatment. Chemosphere 2015, 127, 276−290. (16) Morandi, G. D.; Wiseman, S. B.; Pereira, A.; Mankidy, R.; Gault, I. G. M.; Martin, J. W.; Giesy, J. P. Effects-directed analysis of dissolved organic compounds in oil sands process-affected water. Environ. Sci. Technol. 2015, 49, 12395−12404. (17) Zhang, K.; Wiseman, S. B.; Giesy, J. P.; Martin, J. W. Bioconcentration of dissolved organic compounds from oil sands process-affected water by Medaka (Oryzias latipes): Importance of partitioning to phospholipids. Environ. Sci. Technol. 2016, 50, 6574− 6582. (18) Ross, M. S.; Pereira, A.d.S.; Fennell, J.; Davies, M.; Johnson, J.; Sliva, L.; Martin, J. W. Quantitative and qualitative analysis of naphthenic acids in natural waters surrounding the Canadian oil sands industry. Environ. Sci. Technol. 2012, 46, 12796−12805. (19) Gibson, J. J.; Fennell, J.; Birks, S. J.; Yi, Y.; Moncur, M. C.; Hansen, B.; Jasechko, S. Evidence of discharging saline formation

ASSOCIATED CONTENT

S Supporting Information *

. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.7b02082. Chemicals and materials, water sampling procedures, quality control and sample preparation, in-line SPEHPLC/Orbitrap analysis, NA concentrations, Table S1, Figures S1−S6 (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Phone: (780) 492-1190; e-mail: [email protected] (J.W.M.). ORCID

Chenxing Sun: 0000-0001-9331-4591 William Shotyk: 0000-0002-2584-8388 Chad W. Cuss: 0000-0002-4351-8702 Tariq Siddique: 0000-0003-2371-0200 Jonathan W. Martin: 0000-0001-6265-4294 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge Alberta Innovates (AI) and Canada’s Oil Sands Innovation Alliance (COSIA) funding for this project; Thank you to Brett Purdy (AI) and John Brogly (COSIA) for managerial support of this project and Warren H

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DOI: 10.1021/acs.est.7b02082 Environ. Sci. Technol. XXXX, XXX, XXX−XXX