Modeling point source plumes at high altitudes using a modified Gaussian model

Emissions from elevated point sources travel at high altitudes and contribute to regional air pollution. Emission data are required to evaluate how urban and industrial plumes traveling at high altitudes impact background plumes. Two EPA dispersion models, SCREEN and Industrial Source Complex (ISC) were considered to evaluate the importance of individual point source plumes at high altitude. Running ISC in Excel, rather than FORTRAN, facilitated data manipulation. Using the modified ISC model, plumes (mostly for unstable cases) were examined from four power plants, located in eastern Texas. Air quality data collected by the Baylor aircraft from the Baylor Sampling Project were used for calibration and validation. Emissions of SO2 were considered since SO2 acts as a non-reactant species in the atmosphere when evaluated over flight times used by the aircraft. User defined meteorological parameters were used instead of the more common annual or probabilistic meteorological data. Results demonstrated that on a typical day, using the most occurring stability class, average wind speed and average mixing height, the modified ISC accurately predicted the peak concentrations about 80% of the time. The modified ISC also correctly projected plume width within 70% of the actual spread, at least 60% of the time. However, the model was not very useful for matching concentrations at plume extremes.