A model for the critical hourly concentration, receptor distance and meteorological conditions from point sources with thermal plume rise

Abstract

A new point source pollutant dispersion model is developed, allowing fast evaluation of the critical one-hour-average ground concentrations, along with the corresponding receptor distance and meteorological conditions (wind speed and stability class) for urban or rural areas, under gradual or final plume rise and with or without buoyancy induced dispersion assumptions. Relatively unstable pollutants can be dealt-with, while site-specific meteorological data are not required, as the computed concentrations are maximized against all credible combinations of wind speed, stability class and mixing height, as well as against all receptor distances. The model combines, under a constrained numerical extremization algorithm, the minimum mixing height model of Benkley and Schulman, with the dispersion relations of Pasquill-Gifford and Briggs for rural and urban settings respectively, the buoyancy induced dispersion correlation of Pasquill, the power-law wind profile exponent values of Irwin and the buoyant plume rise relations of Briggs. The model is well suited for air pollution management studies, as it allows fast and accurate screening of selected point sources in study areas and evaluation of the ways to have thier impact reduced, as well as, for regulatory purposes, as it allows the setting of minimum stack size requirements as function of the exit gas volume and temperature, the pollutant emission rates, and the hourly pollutant concentration standards.