A study published in Environmental Research Letters says a “significant” amount of arsenic was released into the air and water due to the 2023 wildfires near Yellowknife.
“Several decades of metal processing activities near Yellowknife, NT, Canada have resulted in widespread accumulation of arsenic in biomass, soils, and sediments, exceeding environmental and human health limits,” the study released in May 2024. “The landscape surrounding Yellowknife is frequently disturbed by wildfire, most recently in 2023, when 2500 km2 burned.”
While arsenic is a naturally occurring element, mining causes “one of the largest” sources of arsenic pollution to the environment.
“The arsenic that comes from the bedrock, which is naturally occurring arsenic in the soils, and then as you get closer into the city itself is when you start to see these elevated concentrations that came from the mine roaster stack and it being released into the air and it would settle down into the ground, into the soil,” said Owen Sutton, the lead researcher from the University of Waterloo.
“What we were seeing was predominantly is a release from the naturally occurring arsenic in the surrounding area with the most recent wildfires.”
According to the study, four fires near Yellowknife in 2023 released between 69 and 183 tonnes of arsenic into the air and water – about half the arsenic wildfires around the world emit per year.
“In 2023 alone, our estimated atmospheric release from just four wildfires was between 15%–59% of global annual arsenic wildfire emissions and likely represented between 2 and 9% of total global arsenic emissions from all natural sources,” the study said.
The work was led by researchers at the University of Waterloo and Nipissing University. They also issue a caution about the risks faced in many parts of the world where there’s both a legacy of mining and smelting operations and are threated by wildfires annually.
Arsenic is a potent toxin associated with diabetes, cardiovascular disease, various cancers and infant mortality.
Researchers said the findings should be treated as a “wake up call.”
“One of the things that we are aware is one of the limitations of the study is that we don’t have the kind of broad expertise that’s necessary to take this to the next stage, which is understanding the implications on human and environmental health,” said Sutten. “That would require a more diverse team of specialists, not just wildfire specialists, but also ecotoxicologists and biologists and geochemists.”
The researchers noted in the study that things aren’t likely going to improve.
“Given that climate change has and will continue to increase both annual area burned and soil burn severity, we emphasize that future increased wildfire activity closer to Yellowknife will place legacy soil arsenic stores at risk of an even larger catastrophic and unprecedented release, especially as wetlands become drier,” said the study.
The study also points to emerging awareness about wetlands being potential emitters of some arsenic as wet lands hold and store these contaminates quite well.
“For decades and centuries, they can accumulate some of these things to get deposited through the air, just like arsenic from the roaster stack and they’re held there quite safely, but wildfire can come through and release them,” Sutton said.
Wetlands are vulnerable from the kind of hot flaming combustion that you see rolling through a forest, and vulnerable to smoldering combustion, which can remain undetected for months and then flare up in new wildfires and can cause metal release.
