| High explosives can be used to aerosolize and disperse a variety of hazardous materials. The rate at which those materials would settle out of the atmosphere, though, is dependent on their size distribution. Larger particles, therefore, would cause high level, but much more localized contamination, where with the aerosol-sized fraction, contamination would be more diffuse, but also much more widespread.;Two sets of experiments have been employed to study explosive aerosolization, and to characterize the thermochemical environment in the fireball to which particulates are exposed. Detonation calorimetry experiments involved detonating small explosive charges in a closed vessel, measuring the amount of heat that was released with different oxygen/nitrogen ratios in the vessel, and characterizing the resulting size distributions and the dispersion of a powdered La 2O3 target throughout different types of soil. Open air trials employed a custom-built, fiber optic probe to sample the light emissions from the interior of a fireball in order to characterize the evolution of its thermal environment over time.;The experimental work has identified that for particulates, likely because their mass and inertia allows them deviate from the streamlines of a circulating fluid, their combustion in the turbulent fireball plays a more important role than the combustion of gas species. Thermochemical evidence from the calorimetry experiments supports this, and has found that condensed phase detonation products (as well as entrained black earth, when present), actually react much faster than gaseous species.;There is actually a profound, two-way relationship between the fireball and the particles entrained within it, as it also provides the turbulent, high temperature environment that drives particle interactions, allowing them to agglomerate and deposit onto one another. These actually serve to increase overall particle size, so that less material remains aerosol-sized. In addition, the entrainment of soil provides additional sites with which the hazardous particulates interact, and thus enhances agglomeration. Significant secondary effects exist in the fireball, therefore, that influence the amount of material that can be released into the air as aerosols, and thus reduce the amount of hazardous material that can be suspended and transported in the atmosphere.;Keywords: explosive dispersal, fireball mechanics, combustion, thermochemistry, aerosols, agglomeration, soil entrainment, calorimetry, spectroscopy. |
