Each year 84 billion-billion pounds of bacterium-sized particles burst into the air, released as a result of forest fires. That’s the equivalent weight of 38 billion cars—more cars than currently exist. These particles are called PM2.5, and once inhaled, they dig deep into your lungs and wreak havoc on your health. PM2.5 are responsible for an estimated 3.2 million pre-mature deaths every year.

On that note, tis the season to crawl under a couch blanket, fix up some hot chocolate, light a cozy fire and watch the smoke curl and crawl upwards. Soon, much larger fires will rage throughout the western U.S. in annual summer blazes. Fire smoke is emitted year-round, but even though it has a massive impact on our health, we know little about it.

So what is smoke? Is it all the same?  What happens when smoke interacts with city pollution? These questions are so complicated – and the answers so critical – that hundreds of scientists from NASA, NOAA, and several universities will convene this summer to observe the chemistry of smoke plumes from wildfires and crop burnings. All of these scientists are gathering for the FIREX-AQ (The Fire Influence on Regional to Global Environments and Air Quality) field campaign and they bring with them aircrafts, mobile laboratories, and satellites.

“This will be the most heavily instrumented campaign that I think we’ve ever done,” said Matt Coggon, a research scientist at the Cooperative Institute for Research in Environmental Sciences.

Trees get old, shed leaves, and collapse. Bushes wither with time. As this biomass crumbles, its crunchy leaves and branches pile up, building pure wildfire fuel that is transformed into gaseous smoke. In the past, natural wildfires were sequestered immediately, which built up this fuel. As a result, wildfires have grown in size and number every year for the last twenty years. Now, controlled burns reduce this fuel and dampen the severity of future wildfires. Even so, climate change is causing warmer temperatures and a drier climate, which is outweighing the efforts of wild-land managers. Last year 16.4 million acres burned within the U.S.


The fact is, wildfires will continue to grow. And their influence on communities, such as the destructive power of fire or the debilitating effects of smoke, will continue to grow as well.

To understand the impact fire smoke may have on communities, Coggon and other scientists began at the Missoula Fire Lab with controlled burns. They used instruments to suck smoke from above the flames, identify the molecular composition and determine how that composition changes. They were able to record a smoke “fingerprint” for more than a dozen different fire fuels, such as ponderosa pine, bear grass, Yak dung, and housing lumber (grim, but important). They also learned that the molecular composition of smoke varies with the fire stage, or temperature.

“Think about when you’re out camping and you throw on a log and get these huge flames, said Coggon. “The flames simmer out and all of a sudden you get a glowing smoldering type of emission. The fingerprint of wildfire emissions can change depending on the type of burn.”

Coggon and other scientists in the team used an instrument called a mass spectrometer to watch smoke molecules react, forming new molecules. The instrument measures the mass of hundreds of molecules every second and how these masses change with time gives clues to how the smoke evolves or oxidizes.

“We’ve started to be able to predict the formation of those molecules,” said Coggon. “And that’s useful because now we have a way of making predictions of how molecules are going to [react] in the real atmosphere.” This is important because many of these organic molecules will affect ozone formation and PM2.5, both toxic pollutants regulated by the EPA.

The results from this campaign are now a blueprint of what to expect this coming summer in the field.

Coggon will be flying on a NASA DC-8 aircraft to sample smoke molecules above wildfires across the western U.S. as well as agricultural fires. The DC-8 aircraft can hold 30,000 pounds of instrumentation and 45 people. The aircraft will be outfitted with instruments, including several mass spectrometers. Each will be focused on a unique set of molecule types and particles like PM2.5.


Two NOAA Twin Otter aircraft will also be flying. These are much smaller planes, but that small size affords the maneuverability needed to fly low through mountainous terrain and sample freshly emitted smoke. It also means the Twin Otter aircraft are un-pressurized. “The whole cabin will fill with smoke” said Coggon.

On the ground, mobile laboratories (vans) stuffed with instrumentation will get within yards of controlled fires to study how the smoke is reacting with urban pollution from local cities. And in space, satellites will locate fires, determine the burn size, and even measure their temperature.

All of these research platforms will be working together to produce a complete picture of the wildfire chemistry. While FIREX-AQ won’t be able to slow wildfire growth directly, it can help us understand how fires are affecting the climate. It will also help us understand how the deep red haze we see each summer affects the community and help us manage it. Wildfires are expected to worsen, but FIREX-AQ is a serious step forward to mitigating the impacts. So next time the sky over Boulder goes hazy with smoke, spare a thought for the dedicated team of scientists in the middle of it.

By Zach Decker

Posted by Science Buffs

A CU Boulder STEM Blog

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