This project will conduct controlled burns to analyze smoke production and its physicochemical properties under various burn conditions. The results will help the Department of Defense optimize prescribed fire management, minimizing smoke impacts while improving fire behavior predictions. Project objectives include: (1) performing combustion experiments using representative surface fuels and forest floors collected from DoD lands; (2) implementing an experimental matrix that dissects the effects of fuel moisture content, relative humidity, and the existence of duff on smoke production; (3) quantifying emission factors of key smoke components; (4) characterizing the smoke chemical composition, optical properties, and water uptake potential; (5) simulating atmospheric processing of the smoke; (6) deriving parameterizations that link smoke production and physicochemical properties to fire behavior; and (7) using the experimental results to refine and extend smoke production calculations in QUIC-Fire. 

Burn experiments will be performed using fuel beds reconstructed from forest floors and surface fuels collected from Fort Stewart and Eglin Air Force Base. Two intensive campaigns will be executed. The first campaign will focus on the effect of fuel moisture and relative humidity on smoke production. Burns of fuel beds with the same dry composition will be performed, but with varying moisture content and relative humidity within ranges typical for and at the margins of the prescription window. 

The second campaign will focus on the effect of duff on smoke production. Burns of fuel beds that include duff will be performed, with the duff conditioned to varying moisture contents to identify the threshold at which it becomes available for combustion. In both campaigns, the project team will perform measurements of the emission rates and physicochemical properties of gaseous and particulate smoke components, which are key for assessing the effect of smoke on health and visibility. 

Complementary online and offline mass spectrometry and chromatography techniques to characterize the chemical composition of the different smoke components, including organic and inorganic aerosol fractions, heavy metals, and various air toxics will be employed. The project team will also perform online measurements of aerosol microphysical properties, including size distributions, light absorption and extinction, and water uptake potential. An oxidation flow reactor will be used to simulate atmospheric processing of the smoke in order to quantify secondary organic aerosol (SOA) formation and characterize the evolution of the smoke physicochemical properties due to aging in the atmosphere. Experimental results (speciated emission factors, chemical composition, optical properties, water uptake, SOA formation) will be parametrized as a function of fuel properties and burn conditions, which will enable implementation in models. 

Finally, the speciated smoke emission factors will be implemented in QUIC-Fire. The source terms in QUIC-Fire will be refined by incorporating the effect of fuel moisture on smoke production and will be extended to include additional smoke components such as gaseous air toxics and particulate organic carbon, elemental carbon, and inorganics. 

With limited burn days and resources, prescribed fire managers require advanced models and tools to prioritize burning areas that maximize multiple resource benefits and meet landscape-level objectives. QUIC-Fire is a tool uniquely suited for this, as they account for fire-atmospheric feedbacks and complex ignition patterns typical of prescribed fires. This research will enhance this tool by linking fuel bed composition, moisture content, and relative humidity to fire behavior and smoke production, enabling land managers to better balance ignition strategies for desired fire outcomes while minimizing smoke impacts. The findings on smoke chemical composition and atmospheric processing will improve wildland-fire emission inventories, benefiting both fire management and the atmospheric chemistry community in understanding and mitigating fire-related air quality issues. (Anticipated Project Completion - 2028)