Unexpected Wildfire Emission Impacts Air Quality Worldwide


CU Boulder co-led study completes first global detection of nitrous acid in wildfire plumes

In lab studies of wildfire, nitrous acid seems like a minor actor, often underrepresented in atmospheric models. But in the real-world atmosphere, during wildfires, the chemical plays a leading role—spiking to levels significantly higher than scientists expected, driving increased ozone pollution and harming air quality, according to a new study led by the University of Colorado Boulder and the Belgian Institute for Space Aeronomy.

“We found nitrous acid levels in wildfire plumes worldwide are two to four times higher than expected,” said Rainer Volkamer, CIRES Fellow, professor of chemistry at CU Boulder and co-lead author on the Nature Geoscience study. “The chemical can ultimately drive the formation of lung- and crop-damaging ozone pollution downwind of fires.”

Nitrous acid in wildfire smoke is accelerating the formation of an oxidant, the hydroxyl radical or OH. Unexpectedly, nitrous acid was responsible for around 60 percent of OH production in the smoke plumes worldwide, the team estimated—it is by far the main precursor of OH in fresh fire plumes. The hydroxyl radical, then, can degrade greenhouse gases, and it can also accelerate the chemical production of ozone pollution—by as much as 7 parts per billion in some places. That’s enough to push ozone levels over regulated levels (eg, 70 ppb in the United States).

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