Abundant reserves of metals and oil have spurred large-scale mining developments across northwestern Canada during the past 80 years. Historically, the associated emissions footprint of hazardous metal(loid)s has been difficult to identify, in part, because monitoring records are too short and sparse to have characterized their natural concentrations before mining began. Stratigraphic analysis of lake sediment cores has been employed where concerns of pollution exist to determine pre-disturbance metal(loid) concentrations and quantify the degree of enrichment since mining began. Here, we synthesize the current state of knowledge via systematic re-analysis of temporal variation in sediment metal(loid) concentrations from 51 lakes across four key regions spanning 670 km from bitumen mining in the Alberta Oil Sands Region (AOSR) to gold mining (Giant and Con mines) at Yellowknife in central Northwest Territories. Our compilation includes upland and floodplain lakes at varying distances from the mines to evaluate dispersal of pollution-indicator metal(loid)s from bitumen (vanadium and nickel) and gold mining (arsenic and antimony) via atmospheric and fluvial pathways. Results demonstrate ‘severe’ enrichment of vanadium and nickel at near-field sites (≤20 km) within the AOSR and ‘severe’ (near-field; ≤ 40 km) to ‘considerable’ (far-field; 40–80 km) enrichment of arsenic and antimony due to gold mining at Yellowknife via atmospheric pathways, but no evidence of enrichment of vanadium or nickel via atmospheric or fluvial pathways at the Peace-Athabasca Delta and Slave River Delta. Findings can be used by decision makers to evaluate risks associated with contaminant dispersal by the large-scale mining activities. In addition, we reflect upon methodological approaches to be considered when evaluating paleolimnological data for evidence of anthropogenic contributions to metal(loid) deposition and advocate for proactive inclusion of paleolimnology in the early design stage of environmental contaminant monitoring programs.

Gold mining operations near Yellowknife (Northwest Territories, Canada) released vast quantities of arsenic trioxide during the 1950s, which dispersed across the landscape. Contemporary measurements of arsenic concentrations in lake water and surficial sediment identify enrichment within a 30 km radius. However, paleolimnological studies have identified possible evidence of mining influence during the 1950s at a lake beyond this distance, suggesting a more expansive legacy footprint may exist. Here, we analyze spatiotemporal patterns of arsenic, antimony, and lead deposition from sediment cores at lakes located 10–40 km (near-field) and 50–80 km (far-field) from the mines along the prevailing northwesterly wind direction (NW) and 20–40 km to the northeast (NE) of the mines to improve characterization of the legacy footprint of emissions. We build upon previous findings to determine if: 1) there is evidence of mine-related pollutants beyond the well-established 30 km radius and 2) enrichment is greatest in the prevailing wind direction, as expected for aerial dispersion from a point source of emissions. Results demonstrate enrichment since the 1950s for arsenic and antimony at least as far as 80 km to the NW and 40 km to the NE, thus legacy deposition extended beyond the currently defined 30 km radius ‘zone of immediate influence’. Concentrations, enrichment factors, and total excess inventories of arsenic and antimony decline with distance from the mines and are greater along the prevailing (NW) than orthogonal (NE) wind direction. Peak concentrations in uppermost sediment strata at near-field lakes in the prevailing wind direction suggest supply of arsenic and antimony remains high from legacy stores in the catchment and lake sediment profiles >60 years after emissions were released. Such lasting influence of legacy emissions likely is not limited to mines in the Yellowknife region, and paleolimnological approaches can effectively delineate zones of past and ongoing pollution from legacy sources elsewhere. • We analyze metals in sediment cores to track dispersal of legacy mine emissions. • Enrichment of As and Sb evident beyond known 30-km radius pollution zone. • Distance from source and wind direction influenced contaminant dispersal. • Enriched surface sediments within 30 km suggest ongoing delivery of legacy metals.

The late John Glew contributed valuable equipment to the paleolimnology community for successful collection and processing of cores of sediment from aquatic ecosystems. Unfortunately, tubes that fit his hammer-gravity corer design are no longer conveniently available for purchase and, with his sudden passing, Glew gravity and coring equipment is difficult or impossible to access. In some field-sampling situations, other commercially available equipment present limitations. Here, we provide an updated design of the Glew gravity corer which accommodates a hammer-percussion instrument and overcomes limitations we have encountered when coring lakes in remote locations from floats of a helicopter or small, inflatable watercraft. Our approach integrates the ‘best of both worlds’ provided by the Glew and commercially available Uwitec designs, using readily available components. We updated the Glew corer tube collar to be compatible with standard, commercially available 90-mm external diameter (86-mm internal diameter) PVC tubing that fits Uwitec components (e.g., Uwitec rubber ‘piston’ and ‘stoppers’; using terminology of the Uwitec catalogue), and designed a spring-loaded gasket-style plunger that achieves greater suction than the standard Glew designs. We also updated the Glew vertical sectioner to be compatible with 90-mm-diameter core tubes typically ranging from 60–120 cm long. An outcome is consolidation of the Uwitec and Glew gravity coring systems, which has allowed for interchangeability and choice among use of original and hammer-driven Glew, Uwitec, and the new hybrid ‘Uwi-Glew-ee’ gravity corer and sectioner configurations, depending on logistical constraints of fieldwork and anticipated lake sediment composition. The parts and systems are available from University of Waterloo’s Science Technical Services (https://uwaterloo.ca/science-technical-services/).