More than Soot: Alberta Fire’s Toxic Emissions
May 20, 2016
The Dark Snow project was originally formed to look into the effects of wildfire soot, especially from North America, on the Greenland Ice Sheet. A Darker ice sheet would absorb more sunlight, and melt faster.
The current Alberta wildfire is extremely unusual in size for this early in the season, and it’s having some significant impacts beyond just carbon and soot.
“All the ash and some of the contaminants that are coming off the landscape when we start to get those rains, is going to be washing those materials into the river, right above the city of Fort McMurray.”
Silins, who is among several water scientists working with the Alberta government on a recovery plan for Fort McMurray, says the contaminated water will be difficult to treat.
Though rain would provide long-awaited relief to firefighters on the front line, it would be a double-edged sword for water treatment officials.
Spring showers can wash wildfire contaminants into the Athabasca River, which feeds Fort McMurray’s water treatment plant. And each rainfall would wash a new wave of contaminants down the riverbanks.
Silins says roughly 30 km of the Athabasca River bank, and more than 100 km of the Clearwater River have been heavily contaminated so far.
“We have very limited experience with these kinds of large, severe wildfires, right on top of a community where you have a water treatment plant.”
As of Wednesday evening there is a 70 per cent chance of showers in Fort McMurray for Thursday.
The Fort McMurray fire, which merged with another smaller wildfire last week, has displaced residents and cleared nearly everything in its path, including swaths of the region’s dense boreal forests. The combined blaze has already released the equivalent of 5 percent of Canada’s annual carbon dioxide emissions and is expected to continue to burn for the next few months. The fires have also filled Fort McMurray’s air with dangerous contaminants, ozone, and nitrogen dioxide, pushing its air pollution to off-the-charts levels. Along with all that carbon, the fires are releasing mercury into the atmosphere.
When a huge fire rages through a boreal forest, it is probably going to hit some peatlands, 80 percent of which are located in high latitudes. Peat contains more mercury than other soils, accumulated in layers that can build up over thousands of years. Peatlands are largely stable sinks for mercury — until a wildfire comes along.
“All of a sudden, you have this big release in a fire,” said Christine Wiedinmyer, a scientist at the National Center for Atmospheric Research’s Atmospheric Chemistry Observations and Modeling Lab. “The mercury that before was staying in one place is now in the atmosphere, and can be transported downwind, adding more mercury in places where we don’t necessarily want it.”
And mercury may be able to travel far away from its source. By some estimates, mercury in the atmosphere can travel around the Earth for about a year before being deposited on land or water.
“The mercury level in rain is not only from us — the sources are also global, like when it gets released Europe and Asia and deposited down,” said Yanxu Zhang, a postdoctoral researcher at Harvard University who studies mercury and other pollutants. “It has the capability for long-range transport, which makes it harder to control and combat.”
Mercury exposure can cause insidious effects even at low levels, worsening health problems that already exist. It depends on the dose and the type of mercury, and there are three types: elemental, which can cause neurological damage; salts, industrial pollution causing kidney problems; and organic, the type that gets into the food chain and causes birth defects and is why pregnant women are advised against eating fish.
“In a lot of cases, mercury has a lasting impact — but the degree to which that resonates is something we don’t understand yet,” said Dave Krabbenhoft, a research hydrologist at the U.S. Geological Survey who’s been studying mercury contamination for 28 years.
The 2012 U.S. mercury and air toxics rule, meant to clean up the industrial kind of mercury pollution from power plants, is expected to prevent some 11,000 premature deaths, 4,700 heart attacks, and 130,000 asthma attacks every year, saving up to $70 billion in healthcare costs annually.
Boreal fires could roll back some of those numbers. Since these fires take place in less-populated areas, they are often left to burn longer, releasing more mercury. This problem will only be exacerbated by the increasing intensity and frequency of boreal fires due to climate change.
And how much carbon has this fire thrown up so far?
And so is another detail about this fire — the amount of carbon that it is apparently pouring into the atmosphere.
Taylor’s colleague, Werner Kurz, is a senior research scientist at the Canadian Forest Service and heads its carbon accounting team. He said he generally estimates that for every hectare of forest land consumed in a fire like this one, about 170 tons of carbon dioxide equivalent emissions — so dubbed because they actually include not only carbon dioxide, but also methane and nitrous oxide, two additional greenhouse gases — head into the atmosphere.
That, in turn, means that this single fire has contributed — for a rough estimate — some 85 million tons of carbon dioxide equivalent emissions.
The fire has also, at least temporarily, worsened the entire nation of Canada’s carbon dioxide emissions.
In 2014, the last year for which statistics are currently available, Canada emitted a net of 732 million tons of carbon dioxide equivalent into the atmosphere. This single wildfire thus may have given off enough carbon to account for over 10 percent of Canada’s total emissions.
“And this is not unusual,” said Kurz. “We had other fire years in Canada where the total emissions, over the entire fire season, certainly approached 20 percent or more of the total emissions. Forty percent even.”
A little over a week ago, when the fire had consumed a little over 200,000 hectares, Kurz estimated, in an interview with the Edmonton Journal, that it was already at 5 percent of Canada’s total emissions.
I also asked Guido van der Werf, a fire emissions researcher at Vrije Universiteit Amsterdam who charted the incredible pulses of carbon to the atmosphere due to Indonesian peat fires last year, how much he thought the emissions might be for the Fort McMurray fire. Assuming a million acres burned — a smaller number than the one above — van der Werf came up with 35 million tons of carbon dioxide equivalents, a similarly smaller figure but also one that’s roughly in the same ballpark.
“The difficulty in calculating emissions from these boreal forest fires is that a large fraction of the emissions are from burning the organic soil. And the deeper the organic layer, the more emissions,” said van der Werf by email.
Indeed, another expert, Mike Flannigan of the University of Alberta, thinks that the 85 million ton estimate might even be a little low — precisely because of the depth of the burn. “It was a deep burning fire due to the prolonged drought,” Flannigan said by email. He also noted that the fire is continuing to grow. Indeed, it just crossed the border into Saskatchewan.