Airborne compounds can have an effect on human health, so it is important to know their concentration when they are emitted. The European Union System for the Evaluation of Substances (EUSES) can provide default calculations, but these results are based on conservative, non-adjustable parameters.
The "GPM tool" allows for the input of stack-specific parameters that influence the distribution of a compound in the air, providing more accurate predictions. The calculations are based on Gaussian Plume Models (GPMs), which are Lagrangian models that describe the dispersion in the immediate vicinity of a source. As these are local models, they do not include regional components.
Assuming turbulence is a random process, GPMs assume that the mean concentration of material emitted from a point source will have a two-dimensional Gaussian distribution perpendicular to the mean wind direction.
The tool is available in the form of an excel spreadsheet and calculates the concentration of a compound in the air at different distances from the stack where it is emitted. The input parameters required for the calculation of a compound at a specific location in the "GPM tool" models are: