Extract of VDI 3782 Part 1 published by
Dispersion of Pollutants in the Atmosphere
Gaussian Dispersion Model for Air Quality Management
This Guideline describes a procedure for calculating ambient air concentrations and vertical mass fluxes of anthropogenic emissions in the vicinity of single or multiple sources for a distance up to 100 km. This area must be flat and enable undisturbed dispersion, with a wind velocity higher than 1 m/s.
The computing procedure 1) which is described in this Guideline can be used for gases, suspended particles (aerosols), and depositing dusts. In a first approximation, it accounts for dry and wet deposition as well as for chemical transformations. By the introduction of mean mixing layer heights, limitations of the vertical exchange are taken into consideration. Sources may consist of point, line, area, or volume sources.
Up to twelve different emission states can be taken into account.
As a result of calculating the ambient air concentrations and the vertical mass flux, values of seasonal or yearly averages as well as percentiles of the distribution of half hour averages, related to one month, one season or one year, may be obtained. Data for shorter periods are not sufficiently valid from the statistic point of view.
Therefore, this guideline can be used especially for the analysis of ambient air concentrations in relation to emitting sources, but also for multiple source systems (air quality management).
The procedure described in this guideline, however, cannot replace calculating procedures which are also based on a Gaussian method, but which are integrated in a closed system of air quality management, which is characterized especially by a fixed temporal and spatial reference of the ambient air concentration (e.g., computing procedures according to TA Luft 86).
This Guideline also deals with the unregulated field of multiple source systems.
The requirements which are needed for the input data with regard to the sources and the decisive meteorological parameters are listed, followed by the description of the procedures for determining the dispersion category as well as the dispersion parameters.
The influence of buildings and different kinds of terrain is dealt with in the guidelines VDI 3781 Part 6  and VDI 3783 Part 6 .
The conditions for applying this Guideline are to be checked thoroughly by competent experts.