Diamonds in the Rough: Identification of Individual Naphthenic Acids in Oil Sands Process Water

Abstract

Expansion of the oil sands industry of Canada has seen a concomitant increase in the amount of process water produced and stored in large lagoons known as tailings ponds. Concerns have been raised, particularly about the toxic complex mixtures of water-soluble naphthenic acids (NA) in the process water. To date, no individual NA have been identified, despite numerous attempts, and while the toxicity of broad classes of acids is of interest, toxicity is often structure-specific, so identification of individual acids may also be very important. Here we describe the chromatographic resolution and mass spectral identification of some individual NA from oil sands process water. We conclude that the presence of tricyclic diamondoid acids, never before even considered as NA, suggests an unprecedented degree of biodegradation of some of the oil in the oil sands. The identifications reported should now be followed by quantitative studies, and these used to direct toxicity assays of relevant NA and the method used to identify further NA to establish which, or whether all NA, are toxic. The two-dimensional comprehensive gas chromatography-mass spectrometry method described may also be important for helping to better focus reclamation/remediation strategies for NA as well as in facilitating the identification of the sources of NA in contaminated surface waters.

Identification of individual tetra‐ and pentacyclic naphthenic acids in oil sands process water by comprehensive two‐dimensional gas chromatography/mass spectrometry

“…[3] However, our results suggest that the extent of the biodegradation of some of the organic matter from which the OSPW NA originate exceeds some conventional biodegradation scales [7] since, in addition to the tricyclic acids, [1] we were now able to identify pentacyclic diamondoid acids. Thus, we identified the methyl ester of diamantane-1-carboxylic acid (I) by interpretation of the mass spectrum ( Fig.…”

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

“…7A and B). These could represent bicyclic naphthenic acids (NAs), which are more resistant to biodegradation than most other saturated hydrocarbons (48,49), resulting in their enrichment in severely biodegraded hydrocarbon deposits like those found in the oil sands outcrops. O55_1 and O55_2 also had increases in the DBE2 and DBE3 groups of species of the O 3 class, likely representing hydroxy-carboxylic acids, and (18,40).…”

Next-Generation Sequencing of Microbial Communities in the Athabasca River and Its Tributaries in Relation to Oil Sands Mining Activities

“…It is very difficult to chemically distinguish the heavy hydrocarbons produced during mining and the extracted hydrocarbons produced through upgrading activities from those that are naturally occurring in the Athabasca River ecosystem, since they originate from the same source. Naphthenic acids are seen as the most promising chemical indicators of potential downstream effects after release (10), and recent work suggests that it may be possible to identify NAs specific to a source (35). Microorganisms, however, are sensitive to low pollutant concentrations, and it is conceivable that they could serve as more accurate indicators for oil sands mining impacts.…”

“…Environmental impacts, however, are difficult to evaluate, since natural bitumen erosion in the Athabasca River and its tributaries also leads to high levels of hydrocarbon-associated compounds in water and sediments. Although naphthenic acids (NAs) are seen as one of the most important chemical indicators of potential downstream anthropogenic effects (10,35), they are difficult to measure and can occur naturally. An alternative to chemical indicators would be the use of microorganisms as bioindicators to track this pollution.…”