HDRFS scientists piece together the puzzle of smoke

HDRFS scientists piece together the puzzle of smoke

Researchers are collecting valuable data on how smoke forms and what happens as it ages in order to fill pressing knowledge gaps.

By Amanda Heidt

March 2024

When smoke from Canadian wildfires cloaked New York City in 2023, atmospheric scientists warned residents to stay indoors. Even without knowing exactly what was in the smoke, it clearly wasn’t healthy, and the state reported an 82% increase in the number of ER visits due to asthma. Indeed, as fire seasons lengthen and fires become more frequent, there’s a renewed sense of urgency to understand not just what smoke is made of, but the potential risks it might pose to public and environmental health.

“For all that scientists have learned about smoke, there’s still so much that no one really knows, and those blind spots can leave us in a risky place,” says Andrey Khlystov, an atmospheric chemist at the Desert Research Institute (DRI), Reno.

To shed light on some of these unknowns, Khlystov and his colleagues in the fire emissions and their atmospheric aging (FEAA) component of the Harnessing the Data Revolution for Fire Science (HDRFS) project recently began a handful of studies to determine how smoke forms and ages, and what that means for our soils, climate, and health. They’re focusing on the sagebrush ecosystem—an understudied habitat that represents the largest contiguous ecotype in the continental United States—and approaching their work with the combined expertise of atmospheric science, ecology, hydrology, and engineering.

One of the main goals of the FEAA component is to better understand how smoke forms and what conditions influence its composition. While scientists know that smoke is made up of different types of particles and thousands of chemicals, the exact mix depends on the fuel source, the climate, and whether the fire is flaming or smoldering. And once smoke enters the air, it quickly begins to break down, meaning that “if you’re downwind of a fire, you’re going to breathe something very different than if you were right at the fire front,” says Hans Moosmüller, an atmospheric physicist at DRI. In many cases, these breakdown products are benign, but others become even more toxic.

The team is currently running controlled burns in small laboratory chambers, or in larger barrels outdoors. They collect soil and vegetation from sagebrush landscapes and set them ablaze, surrounded by instruments that can measure everything from the size and composition of the smoke particles, to their optical properties, to the temperature of the soil. They also expose the smoke to an instrument that accelerates the ambient aging process, allowing them to study the breakdown products that emerge. These burns, Khlystov says, are an exploratory sandbox that will help the researchers make sense of patterns in much larger, less predictable fires.

Making that jump to the field is critical, as it’s here that some of the most important data are lacking. One problem, Moosmüller says, is that the evolution of smoke is dictated in large part by what happens in the first half hour or so, close to the fire where the smoke forms. But collecting those samples, so near to the source, is risky. “Agencies like NASA have done these big, expensive emissions studies with large aircraft, but they can’t get that early smoke evolution—which is really key for the final smoke properties—because they can’t fly close enough,” he says. “That’s one thing that’s unique about our project: we’ll be using drones to fly right near a fire.”

Much like the drone apparatus being developed by the hydrology and cyberinfrastructure innovations branches of HDRFS to collect valuable post-fire data in the field, the FEAA drone will be used to safely access an unpredictable environment. The intent is to fly the drone right up to a fire to collect smoke as it forms to conduct measurements of the temperature, relative humidity, and levels of carbon monoxide and dioxide. The team is currently working with the US Forest Service to test the drone during future controlled burns.

In addition, HDRFS will soon be parsing a sagebrush field site near Reno into grids and burning half of them. In partnership with HDRFS researchers in the hydrology and ecology components, Vera Samburova, an organic analytical chemist at DRI, will be exploring questions such as how the makeup of the plant community—including the presence of invasive species—influences the burn and how the soil is impacted. Fires often change the structure and chemistry of underlying soils, for example, making them more water repellent. This creates a higher risk of flash floods and landslides, and it’s unclear how long it takes for soil to recover. The two main drivers seem to be temperature and the fuel, but beyond that, many open questions remain.

“The fundamental knowledge of what’s going on to create this soil repellency still has a huge gap,” Samburova says. “Our goal is to figure out how temperature and the nature of the soil organic matter contribute to repellency, as well as what’s going on from the chemistry point of view.”