Evaluating the Effects of Atmospheric Stability on the Dispersion of PM10 from a Near-Source, Near-Surface, Point Source Aerosol Generator

An experiment was performed in which the dispersion of an aerosol, generated from a point source using aviation smoke oil, was measured under weakly unstable and neutral conditions at the mouth of Red Butte Canyon in Utah. The objectives of this experiment were to determine how atmospheric stability affects near-ground dispersion of passive scalars and to further understand the underlying physics contributing to atmospheric dispersion. Concentration values at discrete heights for the two cases described above were measured, and then a normalizing technique was applied because a limited number of DustTraks was available for the experiment. Dispersion and turbulence statistics are presented at a downstream distance of 450 cm from the source. The concentration fluxes for both cases indicate that atmospheric stability has a definitive influence on the dispersion of aerosols from near-surface sources. Instability increased the vertical transport of particles (i.e., larger flux measurements) which can be seen in the correlations between the vertical velocity and temperature fluctuations. Spectral analysis revealed that the largest contributions to vertical fluxes came from relatively low frequency eddies.