CAREER: Bridging the gap from biomass burning and wildfires to atmospheric pollutants

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Wildfire incidence and intensity have increased in some parts of the world in recent years and are poised to continue increasing in the future due to the warming climate. Wildfire emissions, which can have significant detrimental health impacts, will likewise increase. Additionally, some wildfire emissions absorb and scatter ultraviolet and visible light, which makes these emissions particularly important in the radiative balance of the earth. The ability to identify, quantify and model the formation of these emissions would have many benefits, such as aiding in management decisions regarding wildfires and informing studies of wildfire health effects. Yet, there is a significant lack of understanding of what chemical compounds are initially emitted from burning biomass, and how they evolve in the atmosphere to form the types of aged emissions that are measured near wildfires. Thus, it is challenging to predict the formation of these emissions and their impacts. This research will bridge the gap between laboratory measurements of freshly emitted emissions and field measurements of atmospherically aged emissions from biomass burning.This research will develop a predictive model of woody biomass burning emissions which are pertinent to radiative forcing using a hierarchical approach based upon the three major constituents of lignocellulosic biomass: hemicellulose, cellulose and lignin. Experiments will be utilized to develop this model for formation of primary and aged emissions from biomass and its constituents under conditions relevant to open burning. These conditions include significant heat and mass transport limitations due to large fuel sizes and low thermal conductivity of wood, and prolonged smoldering combustion as opposed to solely flaming combustion. Emissions from biomass pyrolysis and oxidation will be measured, with an emphasis on evaluating the rates of production of species that have been identified as highly absorbing and scattering, for the development of kinetic models. Changes in the composition and optical properties of those emissions will be studied during photochemical aging to generate a continuum in understanding of atmospherically measured compounds from precursor formation through photochemical transformation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.