Wildland fires are a significant source of air pollutants. These pollutants present significant regulatory challenges associated with National Ambient Air Quality Standards, the Regional Haze Rule, and forthcoming greenhouse gas regulations. The production, transport, and transformation of these primary and secondary pollutants from fires must be better understood to minimize their effect on human health, economic activity, scenic integrity, and ecosystem resiliency.
Air-quality regulators and land managers employ smoke modeling systems to predict, evaluate, and manage the effect of fire emissions on air quality. Although much progress has been achieved recently in understanding the smoke chemistry of prescribed burning, significant knowledge gaps regarding the chemistry of wildfire smoke have hindered the development of reliable smoke modeling systems.
The Forest Service's Smoke Emission and Dispersion Research Team conducted a multiyear smoke chemistry research project to evaluate emissions from wildfires in the western United States. Researchers installed smoke chemistry measurement instruments on a Forest Service aircraft and measured fresh emissions and smoke dispersion from 25 wildfires in the western United States.
They found that wildfires in the Interior Mountain West burn with a much lower combustion efficiency than prescribed fires. This finding means that for a given mass of vegetation burned, wildfires emit more fine particulate matter (PM2.5) and more non-methane organic compounds (NMOC) that lead to ozone (O3) formation.
These results indicate previous estimates of wildfire emissions underestimated the production of these pollutants and the potential of wildfires to degrade local and regional air quality. This research improves wildfire emission inventories and air-quality models and enhances their ability to minimize and mitigate the effects of wildfire emissions on human health, economic activity, and scenic integrity.