Diffusion Rates

Abstract

The Gaussian diffusion model has achieved considerable popularity among people attempting to describe the role of atmospheric dispersion. The ease of application of this model for conservative pollutants outweighs its shortcomings as a complete mathematical description of the diffusion process. Most engineers employing the model have used the classical dispersion rates originally designated by Pasquill and Gifford. Turner’s Workbook has provided additional impetus tc use of this model, often by engineers not familiar with either the mathematics of the model or the experimental data used to determine the dispersion rates. The purpose of this paper is to provide a set of three families of dispersion curves, based on experimental data gathered since 1963, to yield dispersion rates appropriate to urban and suburban areas, as well as the rural areas appropriate to the Pasquill and Gifford curves. McElroy and Pooler’s curves for urban rates are extended to shorter distances and a set of curves appropriate to suburban areas of heterogeneous topography are proposed.