The Effect of Fuel Characteristics and Fire Dynamics on Emissions, Dispersion, and Air Quality Impacts
Dr. Brian Gullett | U.S. Environmental Protection Agency, Office of Research and Development
This project responds to the three objectives as listed in the Statement of Need: (1) understand physical fire processes at scales relevant to key processes like plume development and fire behavior by beginning with the laboratory experimental scale and graduating to operational scales to validate results and apply to modeling efforts; (2) couple fire dynamics to near-field emissions and subsequent regional impacts on air quality (ozone and particulate matter); and (3) advance understanding of fuel characteristics and structure on fire behavior. The overarching goal of this project is to link emissions production and dispersion in the near-plume environment to heterogeneity in fuels, firing methods, resultant fire dynamics/intensity, and convective structures. The specific objectives of the project are to: (1) progressively characterize fuel bed variation at fine (1 meter squared [m2] ) to coarse (>100 m2 ) scales, documenting how they influence emissions from wildland fires; (2) link spatial variation in fire dynamics from changes in ignition patterns with emission production and transport; and (3) at operational scales, model combined influences of ignition patterns/rates and fuel structure on fire dynamic-driven patterns of emissions production and regional air quality. Each of the above objectives is linked to tasks that are addressed through progressively heterogeneous and complex fuels from lab to field, isolated flow effects on emissions production by moving from lab to wind tunnel in natural fuel beds, and progressively linking elements driving emissions and dispersion as the scale moves to an operationally representative scale.
Through a series of progressively increasing scaled experiments and in cooperation with complementary Strategic Environmental Research and Development Program (SERDP)-funded projects already in progress, we will determine the relationships between fuel characteristics, fire dynamics, and emissions as source terms in FIRETEC, a computational fluid dynamics (CFD)-based coupled fire/atmosphere model. Laboratory and wind tunnel fire dynamics and emission data will be used to develop and refine emissions source terms in FIRETEC as functions of local fuel conditions and variation of ignition practices. Development of an air pollution model (“SOOT”) within FIRETEC will be verified at the operational scale for prediction of local smoke dispersion and coupled to an EPA regional air quality model (CMAQ) for prediction of ozone (O3) and fine particulate matter (PM2.5).
Understanding the linkages between fuel characteristics, fire dynamics, and air quality is necessary to develop and validate risk-reducing fire models, which in turn will directly benefit Department of Defense (DoD) fire managers by minimizing restrictions to training scenarios and managing wildfire risk. By implementing new wildfire emissions source terms in high fidelity coupled fire/atmosphere models, this research will explore trade-offs for combinations of wind, fuels, and ignitions in order to optimize prescribed fire results while minimizing emissions and air quality impacts.