Air Dispersion Modelling

Air dispersion modelling has become one of the main tools in the study of air quality whereby it is a key element in most environmental impact assessments. In general, two different models will be considered, namely the Gaussian Plume Model and the Stochastic Lagrangian Particle Model.

The first model assumes that the source emits a constant stream of pollution. Then it can be proven mathematically that the resulting plume will have a Gaussian concentration profile in the lateral and vertical directions. This Gaussian profile will fan out as the distance to the source increases.

The second model assumes that each source emits a large number of particles, and each particle follows a random path around the mean wind vector. This path is updated with every time step. Predictions of pollutant concentration are obtained by counting the number of particles in a given volume of air.

The goal of calculating dispersion is to predict or diagnose the pollutant concentration at some point distance from a source.