Dispersion Modeling of Atmospheric Compounds across a Valley in Southern Utah

Dispersion of atmospheric constituents from agricultural sources raises serious concerns about the impacts of agricultural practices on air quality. Measurement of agricultural-derived atmospheric compounds is difficult because of variations in the downwind behavior of these aerosol plumes. These variations arise from the spatial in-homogeneity of the underlying terrain, the spatial heterogeneity of source areas, and local meteorological conditions. In May 1998, meteorological data were collected from 10 m towers and radiosonde upper air profiles of the boundary layer at a swine production facility located in a shallow valley in southern Utah. These data were used as inputs to a high resolution wind model. Next, these simulated wind fields were used to drive the diffusion model. Results from the model simulations revealed the compound complexities in plume formation and dispersion as the result of the imposed meteorological conditions, the configuration of the underlying terrain, and interaction with morphological land features, such as trees and buildings. The emission plumes varied in lateral and downwind dimensions during the day and among days. Multiple plumes also can converge to extend higher concentrations further downwind. Results of this type of modeling will become increasingly important to aid in assessing transport and downwind distribution of atmospheric constituents which impact upon air quality.