Fire Radiative Power (FRP)-based Emission Factors of PM2.5, CO and NOX for Remote Sensing of Biomass Burning Emissions

Abstract:

Large-scale biomass burning such as forest fires represents an important and yet uncertain source of air pollutants and greenhouse gases on a global scale. Due to the highly accidental nature of forest fires, satellite remote sensing could be a promising method to develop regional and global fire emission inventories on a real-time basis. Reliable fire radiative power (FRP)-based fuel consumption and emission factors are critical in this approach. In an attempt to obtain the information, laboratory combustion experiments were conducted to simultaneously monitor FRP, fuel consumption, and emissions of fine particulate matter (PM_2.5), carbon monoxide (CO), and reactive nitrogen oxides (NO and NO₂). FRP were quantified using temperature-resolved values from a thermal imager instead of conventionally used average temperature, as the former provides more realistic estimates. For dry Ponderosa pine branches, a common fuel in the Sierra Nevada, a strong correlation (r² ~ 0.8) between FRP and the mass reduction rate (MRR) was found. This led to a radiative energy yield (REY) of 8.5 ± 1.2 MJ/kg, assuming blackbody radiation and a flame emissivity of 0.5. Mass-based emission factors were determined with the carbon balance approach. Considering the ratio of mass-based emission factors and the REY, FRP-based emission factors: PM_2.5: 11 g/MJ, CO: 8.0 g/MJ, NO: 0.33 g/MJ, and NO₂: 0.07 g/MJ were quantified. The application of this approach to other fuel types and uncertainties in the measurements will be discussed.