Studying how arsenic and mercury affect ecosystems near Yellowknife gold mines
Our studies have revealed how and when lakes were affected by contaminants, which can lead to more sustainable mining practices.
Yellowknife is home to half the population of the Northwest Territories in Canada, and owes much of its economic expansion to gold mines. In particular, Giant Mine, located just 7 km from downtown Yellowknife, produced over 7 million ounces of gold during its operation that spanned from 1948 to 2004.
However the economic boom from this Klondike gold rush had an unfortunate consequence. Toxic arsenic trioxide dust was being released from the mine’s roaster stack, with the worst contamination occurring in the first decade of the mine’s operation. Over 20,000 tonnes of arsenic trioxide dust was released directly to the air from the stack between 1948 and 1958. In subsequent years, the mine’s operators collected and moved the toxic dust underground, leaving a legacy that must be maintained until a solution for this contamination can be found. Despite a $1 billion remediation effort, there is widespread public concern over this contamination.
Mija Azdajic and David Eickmeyer sampling near Yellowknife, NWT, Canada. Photo: Martin Pothier
Our lab has been engaged in a project to study the effects of that legacy arsenic in lakes near Yellowknife. As part of this research program, we initially drew attention to high arsenic in Yellowknife lakes in a 2016 study that showed high arsenic in lakes within a 15 km radius of the mine. Another study from our lab in the same year revealed that high arsenic releases to Pocket Lake near Giant Mine resulted in dramatic changes to the lake’s ecosystem. A novel aspect of our study was that we used dated lake sediment cores to show the timing and magnitude of these changes, enabling us to show that contamination from the mine was responsible for the changes observed on a lake ecosystem. In the process, we began developing the concept of Paleoecotoxicology, the use of natural archives like lake sediments to track historical ecological effects of past contamination events.
Media on this story:
CBC – Aug. 25, 2016:
CTV News – Aug. 25, 2016:
Eye on the Arctic Radio - Aug. 25, 2016:
Mining.com - Aug. 25, 2016
My Yellowknife Now - Aug. 25, 2016:
