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Scientists have a better understanding of how wildfire smoke affects air quality thanks to data gathered from a specially equipped jet that flew through and studied wildfire smoke for a month.
They found a way to predict the production of the pollutant ozone, which can cause poor breathing conditions and harm the environment. The team found that mixing wildfire smoke with urban pollution causes ozone to be created, which is a recipe for air quality problems.
It's well known that wildfires lower air quality. It's important to understand the chemical and physical mechanisms by which they do so that we can more effectively forecast how individual fires will impact the communities downstream.
A paper on the research was published by Science Advances on December 8.
The data was collected through the NASA/NOAA FIREX-AQ project, which flew missions out of Idaho during the summer of 2019. The project studied fires in the Midwest. Scientists flew through smoke and gathered information from instruments on a converted DC-8 as it flew through a flying laboratory. The Caltech instruments used by the graduate students and staff scientist John Crounse were included in the payload.
"It's hard to study smoke," says Xu. The chemistry and mixing evolve at scales much smaller than the resolution typically available by remote sensors. It is difficult to sample from an aircraft because of the lack of visibility and challenges with air traffic control. FireX-AQ was able to overcome most of the barriers with a very well-equipped aircraft with flight planning that was highly coordinated with the local air traffic control and the incident control officials fighting the fires.
The information collected by the FIREX-AQ project was unprecedented. Key observations explain the chemistry that causes ozone in fire. The findings from this analysis help researchers understand why ozone production is vigorous when the fire is in the air, but slower when the fire is out. The ozone formation is driven by two key ingredients: sunlight and nitrous acid, also known as HNO2, which is a chemical that is emitted into the atmosphere.
The amount of HONO emitted from the fire, the amount of VOCs, and the amount of NO were all predicted by the data pored over by the group. The chemistry slows to a standstill as the fire plume runs out of NO and HONO, but the fuel for ozone formation remains elevated. Ozone formation will occur when these fire plumes mix into the urban atmospheres rich in nitric oxide, which is produced by fossil fuel combustion.
During fire season, fires increase regional ozone. In the past few years, we in the western U.S. have experienced more severe impacts on areas in close proximity to wildfires.
The team plans to keep mining the data. There are still more discoveries to be found in the information gathered through this project.
The paper is titled "Ozone chemistry in western U.S. wildfire plumes." There are many co-authors from Caltech, NASA, the National Institute of Aerospace, the University of Colorado, Boulder, Florida State University, Georgia Institute of Technology, and the U.S. Naval Research Laboratory.
Science Advances has more information on Lu Xu and her colleagues. There is a DOI: 10.126/sciadv.abl3648.
Science Advances has journal information.
Scientists show how wildfire smoke increases ozone pollution.
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