Site-specific spatiotemporal occurrence and molecular congener distributions of naphthenic acids in Athabasca oil sands wetlands of Alberta, Canada.

The Athabasca oil sands region (AOSR) of Alberta, Canada is notable for its considerable unconventional petroleum extraction projects, where bitumen is extracted from naturally-occurring oil sands ore. The large scale of these heavy crude oil developments raises concerns because of their potential to distribute and/or otherwise influence the occurrence, behaviour, and fate of environmental contaminants. Naphthenic acids (NAs) are one such contaminant class of concern in the AOSR, so studies have examined the occurrence and molecular profiles of NAs in the region. We catalogued the spatiotemporal occurrence and characteristics of NAs in boreal wetlands in the AOSR over a 7-year period, using derivatized liquid chromatography-tandem mass spectrometry (LC-MS/MS). Comparing median concentrations of NAs across these wetlands revealed a pattern of NAs suggesting NAs in surface waters derived from oil sands deposits. Opportunistic wetlands that formed adjacent to reclaimed overburden and other reclamation activities had the highest concentrations of NAs and consistent patterns suggestive of bitumen-derived inputs. However, similar patterns in the occurrence of NAs were also observed in undeveloped natural wetlands located above the known surface-mineable oil sands deposit that underlies the region. Intra-annual sampling results along with inter-annual comparisons across wetlands demonstrated that differences in the spatial and temporal NA concentrations were dependent on local factors, particularly when naturally occurring oil sands ores were observed in the wetland or drainage catchment.

Extracts of Passive Samplers Deployed in Variably Contaminated Wetlands in the Athabasca Oil Sands Region Elicit Biochemical and Transcriptomic Effects in Avian Hepatocytes.

Recent contaminant monitoring in boreal wetlands situated in Alberta's Athabasca oil sands region revealed increased concentrations of polycyclic aromatic compounds (PACs) in passive sampling devices deployed in wetlands close to bitumen surface mining operations. In this study, graded concentrations of semipermeable membrane device (SPMD) extracts, collected from 4 wetlands with variable burdens of PACs, were administered to chicken and double-crested cormorant (DCCO) embryonic hepatocytes to determine effects on 7-ethoxyresorufin-O-deethylase (EROD) activity and mRNA expression. Concentrations and composition of PACs detected in SPMDs varied among sites, and the proportion of alkyl PACs was greater than parent compounds at all sites. ΣPACs was the highest in SPMDs deployed within 10 km of mining activity (near-site wetland [5930 ng SPMD-1]) compared to those ∼50 km south (far-site wetland [689 ng SPMD-1]). Measures of EROD activity and Cyp1a4 mRNA expression allowed the ranking of wetland sites based on aryl hydrocarbon receptor-mediated end points; EROD activity and Cyp1a4 mRNA induction were the highest at the near-site wetland. ToxChip PCR arrays (one chicken and one DCCO) provided a more exhaustive transcriptomic evaluation across multiple toxicological pathways following exposure to the SPMD extracts. Study sites with the greatest PAC concentrations had the most genes altered on the chicken ToxChip (12-15/43 genes). Exposure of avian hepatocytes to SPMD extracts from variably contaminated wetlands highlighted traditional PAC-related toxicity pathways as well as other novel mechanisms of action. A novel combination of passive sampling techniques and high-throughput toxicity evaluation techniques shows promise in terms of identifying hotspots of chemical concern in the natural environment.

Hepatic porphyria induced by the herbicide tralkoxydim in small mammals is species-specific.

Tralkoxydim is the active ingredient in a postemergent herbicide used in cereal crops. During preregistration trials, tralkoxydim was observed to cause hepatic porphyria and cholestasis in laboratory mice. Porphyria was not seen in similarly exposed rats or hamsters, but data were not collected regarding the susceptibility of any wild small mammal species to the tralkoxydim-induced porphyria. To address this data gap, we exposed small mammals to tralkoxydim, to 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; a known porphyrinogenic chemical), or to sunflower oil alone. We studied small mammal species that might be exposed following agricultural applications of the herbicide, including the white-footed mouse (Peromyscus leucopus), the deer mouse (P. maniculatus), and the meadow vole (Microtus pennsylvanicus). Because of their known susceptibility to both tralkoxydim- and DDC-induced porphyria, commercially supplied Mus musculus (CD-1 Swiss mice) were exposed as positive-control animals. We also exposed offspring of wild-caught M. musculus to compare their responses to those of the commercially supplied animals. Potential hepatotoxicity was determined by assessing the accumulation of liver protoporphyrin. Of the species tested, only M. musculus was susceptible to the porphyrinogenic action of tralkoxydim, and no significant accumulation of protoporphyrin was observed in any of the other species exposed to the herbicide.