Profiling of individual naphthenic acids at a composite tailings reclamation fen by comprehensive two-dimensional gas chromatography-mass spectrometry

David T Bowman; Lesley A Warren; Brian E McCarry; Gregory F Slater

doi:10.1016/j.scitotenv.2018.08.317

Profiling of individual naphthenic acids at a composite tailings reclamation fen by comprehensive two-dimensional gas chromatography-mass spectrometry

Sci Total Environ. 2019 Feb 1:649:1522-1531. doi: 10.1016/j.scitotenv.2018.08.317. Epub 2018 Aug 25.

Authors

David T Bowman¹, Lesley A Warren², Brian E McCarry¹, Gregory F Slater³

Affiliations

¹ Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St W., Hamilton L8S 4M1, ON, Canada.
² School of Geography and Earth Sciences, McMaster University, 1280 Main St W., Hamilton L8S 4K1, ON, Canada; Department of Civil Engineering, University of Toronto, 35 St. George St. Toronto, ON M5S 1A4, Canada.
³ Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St W., Hamilton L8S 4M1, ON, Canada; School of Geography and Earth Sciences, McMaster University, 1280 Main St W., Hamilton L8S 4K1, ON, Canada. Electronic address: gslater@mcmaster.ca.

PMID: 30308920
DOI: 10.1016/j.scitotenv.2018.08.317

Abstract

Naphthenic acids (NAs) are naturally occurring in the Athabasca oil sands region (AOSR) and accumulate in tailings as a result of water-based extraction processes. NAs exist as a complex mixture, so the development of an analytical technique to characterize them has been an on-going challenge. The aim of this study was to use comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry to monitor individual NAs within a wetland reclamation site in the AOSR. Samples were collected from four monitoring wells at the site and the extracts were found to contain numerous resolved isomers of classical (monocyclic-, bicyclic-, adamantane-, indane-, and tetralin-type carboxylic acids) and sulfur-containing NAs (thiamonocyclic- and thiophene-type carboxylic acids). The absolute abundances of the monitored NAs were compared between four monitoring wells and unique profiles were observed at each well. Few significant changes in absolute abundances were observed over the sampling period, with the exception of one well (Well 6A). In addition, isomeric percent compositions were calculated for each set of structural isomers, and one-way analysis of variance (ANOVA) and two-dimensional hierarchical cluster analysis revealed high spatial variation at the site. However, consistent distributions were observed at each of the monitoring wells for some sets of NA isomers (such as: adamantane NAs), which may be useful for forensic applications, such as identifying sources of contamination or demonstrating biodegradation. The methods and results presented in this study demonstrate the utility of monitoring individual NAs, since both changes in absolute abundances of individual NAs and the distribution of NA isomers have the ability to provide insight into their sources and the processes controlling their concentrations that are not only of relevance to the Alberta Oil Sands, but also to other petroleum deposits and environmental systems.

Keywords: Alberta oil sands; GC × GC; Naphthenic acids; Reclamation; Two dimensional gas chromatography; Unresolved complex mixture.