Wildfires have been increasing in frequency and severity over the past few decades. Wildfires, agricultural fires, land use burns, and other forms of biomass burning are sources of particulate matter and trace gases, including carbon monoxide, to the atmosphere. These gases are detrimental to air quality and the Earth’s climate, and can react to form tropospheric ozone. Many of these trace gases, like benzene, are also hazardous to human health. Here the trace gases from biomass burning in the United States are examined, and the effects on human health, air quality, and climate are reported.
Several large-scale field campaigns have been mounted to study the emissions of fires. These campaigns are usually focused on collecting data from very fresh and aged fire smoke with little influence from background emissions. Therefore, the interactions between fire smoke and urban air have not been well studied. Positive matrix factorization is used here to analyze mixed smoke and urban air masses to tease out the relative emissions contributions from each source.
The emission ratios of trace gas compounds to carbon monoxide are also studied to see if the types of fuels, environment, or burn conditions affect the relative emissions of particular trace gases between different fires. While most trace gases are emitted at relatively consistent rates between different fires and fuels, ethyne, methyl chloride, and methyl bromide exhibited significantly different emission ratios between western wildfires and smaller southeastern agricultural fires.
Finally, chemical box modeling is used to examine the effects of biomass burning emissions on the chemistry of urban air quality. Using inputs for trace gas emissions based on observed data a box model was run for three conditions: urban emissions only, smoke mixed with urban emissions, and heavy smoke mixed with urban emissions. The results indicate that smoke emissions can augment ozone production in urban areas. These results are compared to observations from Pasadena, CA during the 2020 Bobcat Fire.