Assessing Baseline Stream Metal Concentrations in the Cumulative Impact Monitoring Program for Hydrocarbon Extraction by Hydraulic Fracturing of the Canol Shale Play, Central Mackenzie Valley, NT, Canada

In ecologically sensitive and remote northern locations, environmental monitoring programs often face challenging logistical considerations to provide oversight on natural resource exploration and extraction, especially for regions that are already susceptible to terrain instability by permafrost erosion. However, effective monitoring for the cumulative impacts of these development activities is reliant upon comprehensive assessments of ecological conditions prior to disturbances from resource exploitation. In the Sahtu region, western Canada, accessing the hydrocarbon-rich deposits of the Canol Shale Play would require widespread application of hydraulic fracturing extraction techniques, potentially having unforeseen consequences such as further hydrological and landform alterations by permafrost degradation, compounded with concerns of increased contaminant burdens in aquatic ecosystems. To determine the natural variability in this region, we conducted a spatial survey of metal(loid) concentrations in sediment and benthic macroinvertebrates from streams of the Central Mackenzie Valley, south of Norman Wells, NT. Biota-sediment accumulation factors (BSAFs) were also calculated where both invertebrates and sediment were available. Here we focused on elements either included in the Canadian Council of Ministers of the Environment Sediment Quality Guidelines for the Protection of Aquatic Life (i.e. As, Cd, Cr, Cu, Pb and Zn), or reported enriched in other shale/hydrocarbon deposits (i.e. Mo, Ni, V). Concentrations were variable, but generally low, in sediment and biota, and often below guidelines (where existent). Isolated, distributed sites were noted above probable effect levels for As (> 17 μg g^-1), and Zn (> 315 μg g^-1), however BSAFs for As were < 1 suggesting limited bioavailability. Several elements (e.g. Cd, Cr, Cu, Mo, Ni, Zn) show elevated BSAFs, demonstrating the potential bioaccumulation if resource development were to contribute contaminants to the ecosystem. These findings emphasize the necessity of gathering data on baseline environmental conditions and natural system variability prior to resource extraction disturbances, thereby providing the framework for monitoring potential cumulative impacts as a result of hydrocarbon development in northern landscapes.