AURORA COLLEGE
New Research highlights remobilization of legacy arsenic pollution from sediments in Yellowknife Bay

A recent study published in the Journal of Hazardous Materials has shed light on the impact of historical mining activities on Yellowknife Bay. The research, led by Dr. John Chételat (Environment and Climate Change Canada), Dr. Mike Palmer (Aurora College), Dr. Heather Jamieson (Queen's University), and conducted in collaboration with experts from l'Université de Montréal and Carleton University, reveals that contaminated lake sediments are a primary source of dissolved arsenic in the bay's water.

The study, funded by the GNWT-CIMP from 2018-2020, focused on evaluating the remobilization of legacy arsenic from sediments and its relative contribution to lake waters. Researchers compared sediment-derived arsenic to inputs from other sources, such as Baker Creek, the Yellowknife River, and the main basin of Great Slave Lake.

The investigation measured the movement of arsenic from contaminated lake sediments at 20 sites throughout Yellowknife Bay. Results indicated that arsenic fluxes correlated positively with sediment arsenic concentrations, meaning that areas with higher sediment arsenic concentrations experienced greater arsenic fluxes. Researchers found that sediment was a principal source of arsenic in the water column, with a magnitude comparable to that of Baker Creek, a small creek that passes through the mine site.

Another paper from the same project reveals that arsenic minerals in Yellowknife Bay primarily originate from mining activities and undergo geochemical transformations over time. The presence of roaster-generated arsenic (arsenic trioxide) in surface sediment implies that arsenic contamination is ongoing, likely due to the weathering of contaminated soils and shoreline outcrops.

It is important to note that, despite the release of arsenic from sediments, water concentrations in Yellowknife Bay consistently remain below Health Canada's Drinking Water guidelines for arsenic. This is likely due to dilution from the low arsenic water contributed by the Yellowknife River and the main basin of Great Slave Lake. While this study focuses on understanding the fate of legacy arsenic in Yellowknife Bay, it does not indicate any immediate public health concerns related to arsenic levels in the bay's water.

This research highlights the significance of considering lake sediments as a major source of arsenic in Yellowknife Bay and emphasizes the need to incorporate this information into future environmental management and monitoring strategies.

Key Points of the research are:

1. Contaminated lake sediments are a primary source of dissolved arsenic in Yellowknife Bay's water, resulting from historical mining activities.
2. Sediment-derived arsenic is a principal source of arsenic in the water column, comparable in magnitude to inputs from Baker Creek.
3. Despite arsenic release from sediments, water concentrations in Yellowknife Bay consistently remain below Health Canada's Drinking Water guidelines, indicating no immediate public health concerns related to arsenic levels.

The Journal of Hazardous Materials in an international forum that publishes articles in the area of Environmental Science and Engineering. Read the full study here.