Burning Concern: Drought-Driven Wildfires Generating Pollution

Denver’s skyline was frequently hazy this summer because of wildfires.
This summer, the foothills and mountain peaks that form Colorado’s Front Range have been nearly invisible at times because of thick haze from wildfires in the state and across the region. The view to the west from Boulder and the Denver area has been obscured for days in a row.

The emissions from the fires are doing more than messing with our view. Scientists at the National Center for Atmospheric Research have found that the emissions are pumping out tens of thousands of tons of particles, carbon dioxide, pollutants that form ground-level ozone and even mercury produced by power plants and absorbed by vegetation.

Atmospheric scientist Christine Wiedinmyer at NCAR in Boulder is among the researchers studying what the wildfires are doing to our air quality. It’s a crucial question for the Denver metro area and northern Colorado, which have struggled through the years to meet federal air-quality standards.

It’s a serious concern for the entire region, where wildfires, including Colorado’s most destructive on record, have burned all summer. And it’s a problem likely to get worse as record hot, dry weather, driven by climate change, intensifies the fire danger in the West.

Wiedinmyer has compared Colorado’s wildfire emissions in 2002—another bad year—to this summer. Carbon monoxide emissions from April through June 2002 totaled 47,000 metric tons, or the equivalent of 15 percent of all human-caused sources for that time period. During the same period this year, wildfires in Colorado produced 76,000 metric tons of carbon monoxide—equivalent to 24 percent of all human-caused carbon monoxide in those three months. Carbon monoxide is an air pollutant regulated by air quality standards and is also released from man-made sources such as cars and power plants.

Carbon dioxide, the primary greenhouse gas produced by human activities, was boosted by the wildfires this year. Wiedinmyer calculated that the fires generated 1.3 million metric tons of the gas through July. In 2009, the last year for which data were available, Colorado’s entire commercial sector emitted 4.6 million tons of carbon dioxide. The grand total for all sectors was 93.7 million metric tons.

“Overall, the fires are equivalent to a small fraction of that the man-made emissions of carbon dioxide,’’ Wiedinmyer said, “but when you start looking at individual sectors, at individual types of fuel, like coal or natural gas, it can be significant.’’

Smoke rises from a wildfire burning in Boulder’s foothills.
For example, the use of natural gas by utilities emitted 6.2 million metric tons of carbon dioxide in 2009 in Colorado.

The figure of 1.3 million tons from this year’s wildfires covers just the first seven months. The number doesn’t include emissions from out-of-state fires that drift into Colorado.

The research has caught the attention of Colorado state health officials, who are trying to figure out what larger, more frequent wildfires will mean for air quality – and the mandate to meet federal standards. State regulators have tightened regulations on the natural gas industry in eastern Colorado as the metro area has slipped out of compliance the past few years.

So, health officials want to know the volume and type of emissions coming from wildfires, said Gordon Pierce of the state air pollution control division. Pierce said much of the state’s concern centers on the fine particles and other pollutants that form ground-level ozone.

Other states are also looking at the research on pollution from wildfires.

“One of the reasons we’ve looked at that, and the carbon releases from the fires, was that states are looking at their carbon emissions and trying to understand their carbon budget for policy purposes,’’ Wiedinmyer said. “Particularly in the Western U.S., it’s really important to consider the fires and what’s happening to the ecosystems. You have large releases of carbon to the atmosphere when you have these large-scale fires and they are significant when you compare them to anthropogenic emissions.’’

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