Wildfires and Combustion
Optical Properties of Wildfire Smoke from Controlled Combustion of Canadian Biomass Fuels
Mahsa Zarei
M. Zarei[1], A. Moallemi[2], T. J. Sipkens[2], O. Olfert[1], A. Hanashiro Moraes[3], S. Talebian[3], R. Afroz[3], M. Al-Jabiri[4], A. W. H. Chan[4,5], R. Chang[6], K. Chen[1], L. Drinovec[7,8], B. Isenor[4], A. Lee[9], J. Liggio[9], C. Liu-Kang[4], G. Marshall[10], G. Močnik[7,8], S. G. Moussa[9], M. Saleh[6], H. Shen[11], J. J. B. Wentzell[9], S. N. Wren[9], J. Yus-Díez[7], P. Hayes[12], J. P. D. Abbatt[4], R. Zhao[3], J. C. Corbin[2], J. Olfert[1]
Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada
Wildfires release substantial amounts of particulate matter (PM) into the atmosphere, significantly impacting air quality, human health, and climate. The optical properties of smoke particles determine how aerosols interact with solar radiation through light absorption and scattering, making them essential for accurate representation of wildfire emissions in atmospheric and climate models.
The optical properties of wildfire smoke vary significantly depending on fuel type and combustion phase. However, current climate models rely on global averages, which may not accurately capture the characteristics of fuels typical of boreal forests, where most Canadian wildfire activity occurs.
Building on the 2024 BBCan Fire Lab Campaign in Edmonton, this study measured the optical properties of smoke from controlled combustion of common boreal forest fuels under both flaming and smoldering phases. Fuels included grass, mulch, ponderosa pine, and peat, which exhibit distinct combustion behaviors affecting smoke properties. Measurements were performed at three wavelengths using a dual-spot aethalometer, Photoacoustic Extinctiometers (PAX), and Cavity Attenuated Phase Shift (CAPS) spectrometers.
The analysis focused on key parameters including the absorption coefficient, scattering coefficient, and single scattering albedo (SSA). Measurements indicate that flaming combustion generally produces higher light absorption associated with black carbon; while smoldering combustion tends to generate organic-rich aerosols that scatter light more efficiently. Additional comparisons between denuded and undenuded aerosol samples reveal the influence of particle coatings on measured optical properties.
This comprehensive dataset enables calculation of derived optical parameters, including the mass absorption coefficient (MAC), Angstrom exponent (AE), absorption cross-section, and scattering cross-section. Such data are critical for improving climate models, air quality predictions, and understanding the evolving impact of wildfire emissions on the atmosphere.