Poster
Environmental Monitoring and Research

Long-term Stability of Arsenic Minerals in Yellowknife Bay Sediments

Soapbox Wednesday, November 20, 2019 - 12:52pm to 12:59pm Theatre Lobby and Theatre 2
(Student abstract)

Author(s)

K. Paudyn (Presenting)
Queen's University
J. Chételat
Environment Canada
H.E. Jamieson
Queen's University

Yellowknife Bay, a northern extension of Great Slave Lake located in the Northwest Territories, Canada, is a waterbody valued by the surrounding communities of Dettah, Ndilo, and Yellowknife for its cultural, subsistence, and recreational uses. Located adjacent to the historical Giant and Con Mines, Yellowknife Bay has received inputs from multiple mine waste streams since the regional onset of gold mining in the late 1930s. A combination of stack emissions, tailings decant discharged via Baker Creek, and direct disposal of Giant Mine tailings has led to pervasive and geochemically complex arsenic contamination in the lacustrine environment. Previous research indicates that arsenic contained in Yellowknife Bay surface waters is elevated relative to Yellowknife River and the main body of Great Slave Lake, albeit within Canadian water quality guidelines for the protection of aquatic life and drinking water. Arsenic contained in sediments associated with peak mining activity is not being buried effectively over time and is mobile in the post-depositional environment, representing a potential sink or source to overlaying waters.  Investigating the solid-phase speciation of arsenic minerals in Yellowknife Bay sediments will assist in predicting their long-term stability under changing environmental conditions.

During three field seasons (August 2018, March 2019, and July 2019), nine sediment cores were collected proximal to Baker Creek, tailings beach, Ndilo, and Con Mine. Sediment cores were extruded in oxygen reduced conditions and divided for transport to Queen’s University in Kingston, ON, and Environment Canada in Ottawa, ON for mineralogical and geochemical analysis, respectively. Samples will have their modal mineralogy determined by scanning electron microscopy (SEM)-based automated mineralogy, and EMPA (Electron Microprobe Analysis) may be used to understand the long-term stability of arsenic solid phases.