Developing a New Air Pollution Dispersion Model with Chemical Reactions Based on Multiple Cell Approach

A two dimensional atmospheric dispersion model for computation of the ambient air concentration of reactive pollutants emitted from ground level sources is described. Atmospheric chemical reactions are the most complicated and stiff part of pollutants dispersion equations. Coupling them with other physical transport processes to assemble an integrated dispersion model is a time consuming and complicated matter. Mechanism of reactions can be present in form of ordinary differential equations (ODEs). Different pollutants, however, may present different variability characteristic due to their specific emission patterns, rates of diffusion, and transport and transformation behaviors like atmospheric reactions. In this article, reaction term was combined with other parts of dispersion model by using a mathematical technique. The program can simulate ground level emission sources and only needs meteorological data and emission source parameters. The outputs from the MATLAB^® program are presented in graphical form. The program was designed to be user friendly and computationally efficient through the use of variable pollution grids, factorized operations, and memory pre-allocation. Model estimation results show that, pollutant concentration is determined as a function of distance downwind and distant from the surface. Conservation of mass equations for an array of cells or nodes are solved simultaneously by an implicit finite difference method for different representative atmospheric conditions.