8. Types of Atmospheric Dispersion Models

8.1 Gaussian Plume Models

These use an equation such as (24), (47) or (57) to predict the concentration of pollutant emitted by a short-lived or continuous point or line source. They are particularly useful for studying the effects of a single source. They are less well adapted to problems involving many sources (e.g. a whole city) or problems where chemical reactions of pollutants are important.

8.2 Single Box Models

These models define a box enclosing the region of interest and for that box consider

\left (\matrix{\hbox{Accumulation}\cr
\hfil\hbox{rate}\hfil}\right ).

This is particularly suitable for a model of a polluted city. It is well-adapted to the inclusion of chemical reactions and many different pollutants but it is of no use for predicting local concentrations of pollutants.

8.3 Multi-Box Models

These are similar to single box models except that the fluxes of pollutant into each box are derived from the fluxes out of the adjacent box (see Fig. 13).

Fig. 13. Two boxes of a multi-box pollutant transport model showing the matching of fluxes across inter-box boundaries. The flux $F_1$ of pollutant out of Box 1 is equal to the flux $F_2$ of pollutant into Box 2.

8.4 Numerical Solution of the Concentration Equation

This is the most general approach but is usually the most expensive (see §10 for more details).

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