Several recent studies have reported evidence that surface mining operations of bitumen in northern Alberta's oil sands (OS) region contribute significantly to the atmospheric deposition of metals and polycyclic aromatic compounds (PACs) within the vicinity of OS development. The present study examines the accumulation of PACs in boreal wetlands at varying distance from OS industrial activities with the use of semipermeable membrane devices (SPMDs) and wood frog (Lithobates sylvaticus) tadpoles. SPMDs were deployed in shallow lentic waterbodies adjacent to wood frog egg masses and were retrieved, along with tadpoles, approximately 35-45 days later. The highest concentrations of PACs were detected in SPMDs deployed within a 25 km radius of surface mining activity, consistent with snow deposition studies of PACs in the region. In wetlands located within the vicinity of surface mining activity, PAC profiles of SPMDs and wood frog tadpoles were dominated by C1-C4 alkylated PACs, including alkylated dibenzothiophenes, which are strongly indicative of petrogenic sources. Contrary to differences seen in the SPMD PAC concentrations, there were no obvious differences in the ∑PACs in wood frog tissue between wetland study sites, although alkylated fluorenes were found to be higher in tadpoles collected from a wetland located within 10 km of two bitumen upgrading facilities. The use of SPMDs in tandem with wood frog tadpoles can help assess the potential exposure of aquatic organisms to PACs in boreal wetlands.

Many polycyclic aromatic compounds (PACs) are toxic, carcinogenic, and mutagenic. As a result, their effects on aquatic biota and ecosystems are of great concern. Research on PACs in aquatic biota often overlooks the role of amphibians, alkylated PACs, and sediment as an uptake route. In order to study the accumulation and toxicokinetics of PACs following sediment and aqueous exposure, and to compare the bioaccumulation potentials of parent and alkyl PACs, two accumulation-elimination experiments using wood frog tadpoles (Lithobates sylvaticus) of Gosner stage 28-32 were conducted (one evaluating exposure to contaminated sediment and water, and the other to contaminated water alone). A complementary field study was then conducted near Fort McMurray, Alberta to assess PAC body burdens in field-collected amphibian larvae, and to determine whether PAC body burdens are related to exposure to sediment and/or water in the field. The results of our studies showed that PAC concentrations and uptake rates in wood frog tadpoles were highest when they were exposed to PAC-contaminated sediment. Consequently, we determined that the dominant route of exposure of wood frog tadpoles to PACs is sediment rather than water. This finding supports other studies that have shown dietary uptake to be an important route of PAC exposure in other aquatic organisms. In both the laboratory and field study, alkyl PAC concentrations exceeded those of parent PACs in wood frog tadpoles, which also demonstrated petrogenic PAC profiles. Interestingly, parent PACs seemed to have greater bioaccumulation potential than alkyl PACs in the laboratory-exposed wood frog tadpoles