Emily Lincoln

Emissions from the laboratory combustion of wildland fuels : Particle morphology and size

[1] The morphology of particles emitted by wildland fires contributes to their physical and chemical properties but is rarely determined. As part of a study at the USFS Fire Sciences Laboratory (FSL) investigating properties of particulate matter emitted by fires, we studied the size, morphology, and microstructure of particles emitted from the combustion of eight different wildland fuels (i.e., sagebrush, poplar wood, ponderosa pine wood, ponderosa pine needles, white pine needles, tundra cores, and two grasses) by scanning electron microscopy. Six of these fuels were dry, while two fuels, namely the tundra cores and one of the grasses, had high fuel moisture content. The particle images were analyzed for their density and textural fractal dimensions, their monomer and agglomerate number size distributions, and three different shape descriptors, namely aspect ratio, root form factor, and roundness. The particles were also probed with energy dispersive X-ray spectroscopy confirming their carbonaceous nature. The density fractal dimension of the agglomerates was determined using two different techniques, one taking into account the three-dimensional nature of the particles, yielding values between 1.67 and 1.83, the other taking into account only the two-dimensional orientation, yielding values between 1.68 and 1.74. The textural fractal dimension that describes the roughness of the boundary of the two-dimensional projection of the particle was between 1.10 and 1.19. The maximum length of agglomerates was proportional to a power a of their diameter and the proportionality constant and the three shape descriptors were parameterized as function of the exponent a.

Cesium emissions from laboratory fires

ABSTRACT If a radiological incident such as a nuclear power plant accident, a radiological dispersal device, or detonation of an improvised nuclear device occurs, significant areas may be contaminated. Initial cleanup priorities would likely focus on populated areas, leaving the forested areas to pass several seasons where the overhead canopy materials would fall to the forest floor. In the event of a wildfire in a radionuclide-contaminated forest, some radionuclides would be emitted in the air while the rest would remain in the ash. This paper reports on a laboratory simulation study that examines the partitioning of cesium-133 (a nonradioactive isotope of cesium) between airborne particulate matter and residual nonentrained ash when pine needles and peat are doped with cesium. Only 1–2.5% of the doped cesium in pine needles was emitted as particulate matter, and most of the cesium was concentrated in the particulate fraction greater than 10 µm in aerodynamic diameter. For peat fires, virtually all of the cesium remained in the ash. The results from this study will be used for modeling efforts to assess potential exposure risks to firefighters and the surrounding public. Implications: There is a potential for emissions of radionuclides such as cesium-137 from a wildfire over a radionuclide-contaminated forest. This paper reports on a laboratory simulation study of a wildfire with two types of biomass doped with nonradioactive cesium. This simulation suggests that only 1–2.5% of the cesium in the biomass will be emitted from the wildfire, while the rest will reside in the residual ash. In this study, pine needles were the only contributor to the air emissions of cesium; duff was not a source of cesium emissions. In this study, cesium emitted from the simulated wildfire was concentrated in the particle sizes larger than 10 µm.

Final Report for SERDP Project RC-1649: Advanced Chemical Measurements of Smoke from DoD-prescribed Burns

Abstract : Project RC-1649, Advanced Chemical Measurement of Smoke from DoD-prescribed Burns was undertaken to use advanced instrumental techniques to study in detail the particulate and vapor-phase chemical composition of the smoke that results from prescribed fires used as a land management tool on DoD bases, particularly bases in the southeastern U.S. The statement of need (SON) called for (1) improving characterization of fuel consumption and (2) improving characterization of air emissions under both flaming and smoldering conditions with respect to ... volatile organic compounds, heavy metals, and reactive gases. The measurements and fuels were from several bases throughout the southeast (Camp Lejeune, Ft. Benning, and Ft. Jackson) and were carried out in collaboration and conjunction with projects 1647 (models) and 1648 (particulates, SW bases).