Fire emissions in the US are approximately half from Northwestern wildfires and half from prescribed fires that burn mostly in the Southeast US. Wildfires burn slightly more fuel and therefore have overall larger emissions, but prescribed fires dominate the area burned and the number of fires. FIREX-AQ will investigate both wild and prescribed fires. Wildfires generally result in exposures with larger pollution concentrations over larger areas, and cause both local and regional air quality impacts. Their emissions are often transported thousands of miles and can impact large regions of the US at a time (Figure 3). Prescribed fires are usually smaller and less intense than most wildfires but occur more frequently and throughout the whole year. They are usually ignited during periods that minimize population expose and air quality impacts, but can cause regional backgrounds to increase, are generally in closer proximity to populations, and are responsible for a large fraction of the US PM2.5 emissions. To date agricultural fire outputs are still poorly represented in emission inventories. The overarching objective of FIREX-AQ is to provide measurements of trace gas and aerosol emissions for wildfires and prescribed fires in great detail, relate them to fuel and fire conditions at the point of emission, characterize the conditions relating to plume rise, follow plumes downwind to understand chemical transformation and air quality impacts, and assess the efficacy of satellite detections for estimating the emissions from sampled fires.
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