ABSTRACT
The goal of air quality dispersion modeling is to estimate a pollutant's concentration at a point downwind of one or more emission sources. Since the early 1970s, the US Environmental Protection Agency (EPA) has developed several computer models based on the Gaussian distribution function curve. The Gaussian-based model is effective for representing the plume diffusion for a range of atmospheric conditions. The wide application of Gaussian-based models is almost entirely due to the ease of application and the conservative estimates they provide, despite any of their shortcomings in precisely describing a plume's diffusion in the atmosphere. The chapter addresses Appendix A models. In addition to the Gaussian-based models in Appendix A, computer programs have also been created for modeling other specific cases or pollutants. EPA has developed a program called MOBILE5b to calculate emissions from mobile sources based on EPA tests of emissions from a variety of vehicle classes and types.
