A simple dispersion model for the analysis of chemically reactive pollutants

Abstract

The simple ATDL dispersion model, in which the surface concentration is proportional to area source strength divided by wind speed, has been used successfully in the past to estimate concentrations of chemically inert pollutants. In the analysis of chemically reactive pollutants, the concentration predicted by the simple ATDL model can be used as a scaling parameter to put the governing equations into the dimensionless form. The resulting set of differential equations for the time rate of change of concentration in a region contains a few dimensionless governing parameters per equation. By analyzing the governing parameters, the relative importance of chemical and meteorological variables and source strengths can be assessed. As expected, the wind speed and source strength are seen to be the major factors determining the seriousness of the pollution problem in any region. Using a simple kinetic mechanism ( Friedlander and Seinfeld, 1969) for photochemical smog as an example of the application of the model, it is shown that the model is capable of simulating observed noon-time concentrations of NO, NO 2, and RH averaged over the Los Angeles basin on 29 September 1969. It is also shown that the predicted hourly concentrations of NO, NO 2, and RH averaged over the Los Angeles basin on 30 September 1969 are as well correlated with observed concentrations as the predictions of the more complex PICK model, developed by Sklarew et al. (1972).