Wildfire smoke significantly raises ozone pollution, even in remote regions

Forest fires release large amounts of pollutants visible in the atmosphere that darkens the sky and pushes people inside to avoid unhealthy air. But an almost invisible threat to public health associated with forest fires is ozone, the reactive oxygen o molecule o₃ which harms the lungs and other sensitive fabrics of the human body.

The new research by the University of Utah is documenting how smoke from the West forest fires considerably increases ozone concentrations, often above federal health standards, even in remote places with few sources of human emission of ozone precursors, such as nitrical oxides, or not_X.

“The question I wanted to ask was that if we have no urban shows, say that we zero all the programs, will we always have an ozone problem?” The main author Derek Mallia, assistant teacher of research of atmospheric sciences. “This study suggests that we could eliminate all regional emissions from anthropogenic sources of no_XBut fires can always produce a large amount of ozone. “”

Published last month in the journal Atmospheric environmentThis research highlights the double dose of air pollution in areas under the flames, with high levels of fine particles and ozone. It is estimated that exposure to smoke leads to 6,300 deaths per year in the United States.

Complicating this image is the fact that ozone is not released directly into the air; Rather, it is formed in the atmosphere when the oxygen atoms of other pollutants recombine in a photochemical process involving sunlight.

The main engines are not_X and volatile organic compounds or VOCs; The latter is a major component of forest fire smoke. NO_XOn the other hand, is more associated with anthropogenic sources of emission, such as vehicle exhaust pipes and industrial chimneys.

Ozone levels are very difficult to model because the pollutant is controlled by many factors, including the speed and the direction of the wind, the temperature, the cloud cover and the time of the day.

To better understand the complicated relationship between smoke and ozone, the Mallia team applied coupled computer models, known as WRF-Spire and WRF-Chem, to a record smoke event in 2020 which assigned a large part of the west of the United States. The period from August 15 to 26 was among the worst episodes of shooting from the West to the modern era. The August California complex has burned over a million acres in seven counties in the North, causing $ 12 billion in damage. Dozens of fires have raged elsewhere, such as fork fires east of 90,000 acres from Utah and Liesshead and Beachie Creek de l’Oeron fires that burned 400,000 combined acres.

Research has concluded that, on average, the presence of forest smoke increases ozone concentrations by 21 parts per billion (ppm). “Ozone was around 20 to 30% higher due to forest fire smoke,” said Mallia. “It’s pretty big.”

Since the background ozone levels in the West are already high, this additional charge potentially pushes the levels beyond the health standard of 70 PPB established by the US Environmental Protection Agency.

To further complicate things, research has revealed that shade of smoke itself modifies the weather and slows down ozone formation, reducing levels up to 10 ppb in the plume.

“You also have a lot of particles, which is also a polluting, but it can block sunlight and therefore it will reduce the amount of sun available for ozone photochemistry. It can be substantial in some cases,” said Mallia. “If you are right on the fire, there is generally enough shade of smoke where it limits the quantity of ozone. But if you move away far enough and that the plume becomes relatively diffuse, it is generally not thick enough to really limit ozone.”

The point to remember the key to the study is that existing models should be improved as forest fires become more frequent and severe as the climate warms up. Tools such as WRF-SPIRE and WRF-Chem models will be essential to predict air quality and public health protection during the forest fire season-but these tools require continuous refinement to manage the complex dynamics of smoke.