Numerical simulations have been carried out for ambient air supermicrometric particulate concentrations in Maricopa County, Arizona during late fall and winter periods of atmospheric stability. Results of model studies are in approximate agreement with limited field observational data. On the basis of the model studies, observed high particulate concentrations in Maricopa County urban areas during late fall and winter periods of atmospheric stability are associated with local fugitive dust sources. Because of light drainage winds prevalent during these periods, advective transport of dust from countryside to the urban areas is not an important contribution to urban supermicrometric particulate concentrations. Surface roughness, dry deposition, and source strengths are among the most important determinants of ground level concentrations. Reduction in ground level concentrations could be effected through control of dust emissions, as well as by planting trees and other foliage to increase surface roughness and particle deposition. An adequate and practical predictive model, along the lines of the current model, could be developed for Maricopa County as well as for other urban areas in high desert regions.

Project Officer: Jack L. Durham. University of Texas "September 1979." "EPA-600/3-79-082."