Galloway, J.M., Palmer, M.J., Jamieson, H.E., Patterson, R.T., Nasser, N.A., Falck, H., Macumber, A.L., Goldsmith, S.A., Sanei, H., Roe, H.M., Neville, L.A., Lemay, D. Geochemistry of lakes across ecozones in the Northwest Territories and implications for the distribution of arsenic in the Yellowknife region. Part 1: Sediments. Geological Survey of Canada Open file XXX
We obtained near total element geochemistry on 211 near-surface sediment samples from lakes in the central Slave Geological Province, Northwest Territories, with a focus near the City of Yellowknife and Western Interior Platform to document regional concentrations of As and other elements in lake sediments. Concentrations of major and trace elements, including elements of potential human and ecological concern (As, Cd, Cr, Cu, Pb, Zn), were extracted from sediments using a modified aqua regia digestion. Concentrations of As exceed Canadian federal guidelines for the protection of aquatic life in most of the lakes sampled in the Slave Geological Province. Seventy one percent (n=149) of all sediment samples contain As concentrations higher than the Canadian Council of Ministers of the Environment (CCME) Interim Freshwater Sediment Quality Guideline of 5.9 mg/kg and 54% (n=114) of the samples contain As concentrations that exceed the CCME Probable Effect Level of 17 mg/kg. Sediments with the highest As concentrations are from lakes near the City of Yellowknife and likely reflect a combination of contamination associated with past industrial activity and geogenic input from mineralized bedrock and derived surficial materials. Other elements (Cr, Cu, Pb, Zn) are below sediment quality guidelines in the majority of lakes sampled. Literature review and comparison of sediment As concentrations in lakes in the Yellowknife area to regional data collected suggest that background As concentrations in lake sediments of the Yellowknife area are in the 20s of mg/kg, ranging between 10 and 105 (n=10) mg/kg ppm, consistent with As concentrations in lake sediments from elsewhere in the central Northwest Territories (Ingraham Trail median As concentration 10.6 mg/kg, range 1.9-101.6, n=27), Tibbitt to Contwoyto Winter Road (7.9 mg/kg, 0.3-101.4, n=52), and west of Yellowknife to Hay River in the Western Interior Platform (1.1 mg/kg, 0.1-7.1, n=37). This is in contrast to surficial lake sediments that are likely impacted by anthropogenic activities in the Yellowknife region that contain As concentrations 107.9 mg/kg (range 6.30->10,000+).
pdf coming soon