Forest fires have an impact on the climate and air quality

Researchers working in the Ilmari Laboratory at the University of Eastern Finland in Kuopio are currently conducting an extensive measurement campaign focusing on emissions from forest fires occurring on savannah and boreal coniferous forests.

“We are exploring particulate and gas emissions from savannah fires in Africa and forest fires in the boreal coniferous forest zone, how those emissions transform in the atmosphere, and how they affect the climate,” says Professor Olli Sippula of the Department of Environmental and Biological Sciences and the Department of Chemistry at the University of Eastern Finland.

“We have several ongoing studies that are part of the EU’S ATMO-ACCESS project and the ACTRIS infrastructure project,” says Professor Annele Virtanen of the Department of Applied Physics at the University of Eastern Finland.

“Our measurement campaigns are highly international: Emissions from forest fires are being measured in cooperation with the Finnish Meteorological Institute, the North-West University in South Africa, and the University of Rostock and Helmholtz Zentrum in Germany.”

The researchers are interested in forest fires due to their effects on both the climate and air quality. As biomass burns, huge amounts of particulate matter and volatile organic compounds, among other things, are released into the air.

“Compared to transport, for example, emissions from forest fires are very high, yet dependent on the location,” Virtanen says.

New compounds may be formed as smoke ages

In savannah fires, the same areas burn every few years, which is a normal part of nature’s cycle. However, the number of forest fires is increasing due to drought and heat.

“A savannah fire burns in the grass but doesn’t necessarily reach the trees. In boreal coniferous forests, however, both the undergrowth and the soil tend to catch fire,” says Researcher Ville Vakkari of the Finnish Meteorological Institute.

“In this measurement campaign, we are burning South African savannah grass and plants with woody stems as well as the surface layer of coniferous forests. The emissions are then directed into an ageing chamber,” Sippula explains.

“In the chamber, we simulate the photochemical transformations occurring in emissions in the atmosphere, where the sun’s ultraviolet radiation and oxidisers, such as hydroxyl radical and ozone, have an impact on them. The aim is to create chemical processes similar to those in the atmosphere.”

“In a project funded by the Academy of Finland, we are studying sunlight-absorbing particle components generated by forest fires in the boreal coniferous forest zone. Fires generate both black carbon particles, i.e., soot, and light-absorbing organic particulate matter known as brown carbon. These emissions can contribute to accelerating global warming.

“Fires also generate a lot of volatile organic compounds which, as emissions age, oxidise and form so-called secondary particles. Due to atmospheric processes, this leads to the generation of more organic aerosols as the smoke spreads,” Virtanen adds.

Forest fires have an impact on air quality and health. While the effects of fresh smoke can already be assessed relatively well, new compounds may be formed as the smoke ages, and their effects remain unknown.

“The results of the measurements are used to determine emission factors that can be used in climate modelling. One kilogram of savannah biomass immediately generates a few grams of particulate matter when set on fire, but the amount of aerosol mass generated by the ageing of emissions is not yet known,” Vakkari says.

“In the future, forest fires are expected to become increasingly common due to global warming,” the researchers say.

Read more about ILMARI, ATMO-ACCESS and ACTRIS