Northwest Territories Geological Survey

Concerns persist about elevated concentrations of arsenic and other metals in the Northwest Territories due to legacy pollution from Giant Mine. While roasting operations ceased in the late 1990s, the possibility remains that lakes, wetlands, and soils have served as repositories, trapping much of the arsenic released in the 1950s via atmospheric deposition. Paleolimnological studies from far-field locations have shown evidence of arsenic enrichment that coincides with peak mine emissions, but systematic studies are needed to determine the spatial extent of emissions from Giant Mine. As part of the Sub-Arctic Metal Mobility Study, temporal patterns of contaminant deposition and hydrological conditions will be reconstructed from sediment cores collected from eight lakes along an 80-km transect northwest of Yellowknife. Study lakes are located at 10-km increments following the prevailing wind direction. Lake sediment cores will be dated using radiometric methods (210Pb, 137Cs) and analyzed for metal concentrations and a suite of paleohydrological parameters. Objectives include to 1) define pre-industrial baselines of metal concentrations, 2) identify periods and extent of pollution from Giant Mine and other sources, and 3) discern if climate change affects metal transport to aquatic ecosystems.