Correspondence/Rebuttal pubs.acs.org/est
Response to Comment on “Profiling Oil Sands Mixtures from Industrial Developments and Natural Groundwaters for Source Identification”
W
e thank the authors of Yi et al.1 for their interest in our work. The Comment provided by Yi et al. cautions against the use of O2:O4 ratios in source apportionment efforts in the Athabasca oil sands region due to the wide ranges of these ratios reported in their own work and in the literature for oil sands process water (OSPW), surface water, and groundwater.1 The authors further contend that the small data set, and the relevance of one of the OSPW samples in Frank et al.,2 limits the conclusions made for the methodology to achieve source differentiation in the region. In consideration of Figure 1 from Yi et al.,1 we note that the O2:O4 ratio data in Frank et al.2 is entirely consistent with the peer-reviewed literature examples provided with respect to OSPW. In contrast, O2:O4 ratios for OSPW are ∼3 orders of magnitude lower for AIFT-led projects. As the authors note, their data was generated using a different extraction methodology, which, as explained below, may contribute to this discrepancy. In our view, this large difference for the OSPW O2:O4 ratios brings into question the validity of the comparisons. We are aware that the O2:O4 ratios themselves are highly dependent on a number of factors. Headley et al.3 documented effects on O2:O4 ratios derived from solvent effects (Figure 1). Barrow et al.4 also determined that O2:O4 ion class ratios are dependent on ionization mode. Another complicating factor is that O2:O4 ratios are dependent on fractionation of a given sample (whether online or off-line) prior to analysis.5−7
The combination of these instrument-derived factors (influencing not only O2:O4 ratios but also the distribution of all component classes), with the range of O2:O4 ratios encountered in sample types (summarized by Yi et al.1), in our view strengthens the rationale for the complementary use of Level-1 and Level-2 analyses employed and advocated by Frank et al.2 We further demonstrated the use of this complementary approach to disregard “supportive” O2:O4 ratio data from a near-field sample with negligible AEO content, “Finally, although the O2:O4 ratio for the Drive-point 6 sample of 0.92 is suggestive of the influence of OSPW, the low NA concentration (4.8 mg L−1), coupled with the lack of detectable Family A and B acids and a fresh water type strongly indicates this is not the case and illustrates the importance of utilizing the Level-1 and -2 techniques in complement.” Furthermore, we wish to convey that as part of testing the applicability of our methodology and approach beyond the two purported plume sites in Frank et al.,2 in 2012−2013 we have repeated the groundwater collections at these same sites (larger sample volumes, with spatial repetition), have expanded the sampling of the far-field background (∼20 additional sites), and extensively sampled a purported OSPW plume. The analyses for these studies are partially completed, and it is relevant to note that the results thus far strongly support the 2-Level approach and conclusions by Frank et al.,2 including the use of O2:O4
Figure 1. Selective solvent extraction and distribution of naphthenic acid fraction components of NAFC in OSPW observed using negative-ion electrospray ionization Orbitrap mass spectrometry for (a) dichloromethane, (b) ENV+, (c) hexane, (d) toluene, (e) ethyl acetate/dichloromethane, (f) chloroform, and (g) ethyl acetate (±20 r.s.d.). Reproduced with permission from Headley et al.3 Published: September 3, 2014 © 2014 American Chemical Society
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dx.doi.org/10.1021/es504008z | Environ. Sci. Technol. 2014, 48, 11015−11016
Environmental Science & Technology
Correspondence/Rebuttal
(6) Ortiz, X.; Jobst, K. J.; Reiner, E. J.; Backus, S. M.; Peru, K. M.; McMartin, D. W.; O’Sullivan, G.; Taguchi, V. Y.; Headley, J. V. Characterization of naphthenic acids by gas chromatography-fourier transform ion cyclotron resonance mass spectrometry. Anal. Chem. 2014, 86, 7666−7673. (7) Noestheden, M. R.; Headley, J. V.; Peru, K. M.; Barrow, M. P.; Burton, L. L.; Sakuma, T.; Winkler, P.; Campbell, J. Rapid characterization of naphthenic acids using differential mobility spectrometry and mass spectrometry. Environ. Sci. Technol. 2014, DOI: 10.1021/es501821h.
ratios in samples affected by bitumen. These data sets are forming the basis of forthcoming manuscripts. Furthermore, Environment Canada is leading a Canadian national interlaboratory study with more than 15 participating facilities to standardize methods for profiling acid extractable organics (AEOs) in oil sands environmental samples. A report on phase 2 of a second round robin is currently under internal review.
Richard A. Frank† James W. Roy† Greg Bickerton† Steve J. Rowland‡ John V. Headley§ Alan G. Scarlett‡ Charles E. West‡ Kerry M. Peru§ Joanne L. Parrott† F. Malcolm Conly∥ L. Mark Hewitt*,† †
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Water Science and Technology Directorate, Environment Canada, 867 Lakeshore Road, Burlington, Ontario Canada L7R 4A6 ‡ Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, 5 Plymouth PL4 8AA, U.K. § Water Science and Technology Directorate, Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan Canada, S7N 3H5 ∥ Fresh Water Quality Monitoring/Arctic Science and Technology Branch, Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan Canada, S7N 3H5
AUTHOR INFORMATION
Corresponding Author
*Phone: (905)319-6924; fax: (905)336-6430; e-mail: mark.
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Yi, Y.; Gibson, J.; Birks, J.; Han, J.; Borchers, C. H. Comment on “Profiling oil sands mixtures from industrial developments and natural groundwaters for source identification”. Environ. Sci. Technol. 2014, DOI: es10.1021/es503498p. (2) Frank, R. A.; Bickerton, G.; Roy, J. W.; Rowland, S. J.; Headley, J. V.; Scarlett, A. G.; West, C. E.; Peru, K. M.; Conly, M.; Hewitt, L. M. Profiling oil sands mixtures from industrial developments and natural groundwaters for source identification. Environ. Sci. Technol. 2014, 48 (5), 2660−2670. (3) Headley, J. V.; Peru, K. M.; Fahlman, B.; Colody, A. Selective solvent extraction and characterization of the acid extractable fraction of Athabasca oils sands process waters by Orbitrap mass spectrometry. Int. J. Mass Spectrom. 2013, 345−347, 104−108. (4) Barrow, M. P.; Witt, M.; Headley, J. V.; Peru, K. M. Athabasca oil sands process water: Characterization by atmospheric pressure photoionization and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Anal. Chem. 2010, 82, 3727− 3735. (5) Barrow, M. P.; Peru, K. M.; Headley, J. V. An added dimension: GC-APCI-FTICR MS and the Athabasca oil sands. Anal. Chem. 2014, DOI: 10.1021/ac501710y. 11016
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