Other Models

In addition to the Gaussian-based models in Appendix A, computer programs have also been created for modeling other specific cases or pollutants. These other models include photochemical reactions or Eulerian or LaGrangian equations. Some, such as the chemical mass balance (CMB7) or fugitive dust model (FDM), are available for addressing specific pollutants, while others are implemented on a case-by-case basis for unique source or topographic conditions. The environmental engineer is directed to the appropriate U.S. EPA Region office to consult on selection and approval of the appropriate model for these cases.

The urban airshed model (UAM) is an Appendix A model applicable to most regions of the United States (USEPA 1990). The reactive plume model (RPM-IV) (USEPA 1993) accounts for ozone and other photochem-ically reactive pollutants over a smaller area than the urban airshed model.

Toxic or hazardous gas releases can be simulated with several models incorporated into Appendix A. These models are the toxic modeling system short-term (TOXST) (U.S. EPA 1992b) and toxic modeling system long-term (TOXLT) (U.S. EPA 1992a) models which are based on the ISC3 algorithms as well as the dense gas dispersion model (DEGADIS2.1) (U.S. EPA 1989a).

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