Estimating plume dispersion - A comparison of several sigma schemes

Abstract

The lateral and vertical Gaussian plume dispersion parameters are estimated and compared with field tracer data collected at 11 sites. The dispersion parameter schemes used in this analysis include Cramer's scheme, suggested for tall stack dispersion estimates, Draxler's scheme, suggested for elevated and surface releases, Pasquill's scheme, suggested for interim use in dispersion esimates, and the Pasquill-Gifford scheme using Turner's technique for assigning stability categories. Comparison of the dispersion parameter estimates with measurements suggest that Draxler's scheme results in the smallest mean fractional error in the estimated dispersion parameters and the smallest variance of the fractional error. Centerline values of surface concentration are estimated using the Gaussian plume model and compared with the concentration values determined during five field experiments - three for near-surface releases and two for elevated releases. Comparison of the concentration estimates with the measurements from the five field experiments suggests that Draxler's scheme for characterizing the dispersion results in the smallest mean fractional error in the concentration estimates and the smallest variance of the fractional errors.