Impact of prescribed fire emission on air quality over the southeastern US

Prescribed burning is a large aerosol source in the southeastern United States. Its air quality impact is investigated using EPA model-3 system. Fire emissions are calculated based on a recent developed emission inventory by the Visibility Improvement - State and Tribal Association of the Southeast (VISTAS) program. Two scenarios with and without prescribed fire emissions are investigated for the 10 southeastern states in the base year of 2002 of VISTAS. Large impact has been found with the inclusion of prescribed fire emissions. It significantly improved model performance in spring by reducing the mean biases of organic carbon (OC) and elemental carbon (EC). CO enhancements in the free troposphere in spring for some fire events can be confirmed by the Measurements Of Pollution In The Troposphere (MOPITT) satellite CO observations. Model results show that prescribed burning leads to ~30% enhancements of OC and EC in spring, respectively. We found a moderate correlation between local burning areas and the enhancement of EC and OC. Long-range transport leads to some episodes of PM2.5 increase at some sites in the low fire emission areas. In summer, model underestimated carbonaceous aerosols even after the consideration of prescribed fire emission. Scaled fire emitted EC to MODIS observed seasonality of fire counts in summer cannot account for the underestimation. Under-predicted EC in summer indicates missing or underestimated EC sources in the southeastern US.