Odour dispersion modelling in Austria

Two classes of dispersion models are currently used for (regulatory) odour dispersion, namely Gauss and Lagrange models. These models generally predict time-averaged concentrations, often over one hour. Therefore, the models have to be adopted somehow to cope with short-term odour peaks which can be smelled by the human nose. Over the last years, the authors have developed an approach where the shortterm peaks are parameterized according to atmospheric stability (“peak-to-mean” factors). This approach is used with the Austrian Odour Dispersion Model AODM, based on the Austrian regulatory Gauss model, and described here in detail. With the German Lagrange model LASAT as well as with the AUSTAL 2000 model, a factor 4 is used independent of the distance from the source and the meteorological conditions to account for short-term peak concentrations. The models predict the separation distance between odour sources and the adjacent residential area to protect it from excessive odour nuisance. Besides the description of the approach in AODM, the meteorological input data to run the model are of importance. An example of separation distances for a fictitious livestock unit is added.