Dispersion models are an important tool in air quality management as they combine topographic data, emissions – and meteorological data. However, their quality heavily depends on the availability and reliability of the above mentioned input parameters. For sites where those input parameters are not precise enough, diffusive sampler allow assessing the spatial distribution of the air pollution in a convenient and cost effective manner. Due to their independency from power sources, their small size and light weight, their operation in all challenging weather conditions and their easy handling without the need of extensive training, passive sampler prove to be the ideal device for the calibration and quality improvement of complex dispersion models of all kinds.
The passive sampler devices are based on the diffusion of molecules onto an absorbent surface. The driving force is the concentration gradient between the surrounding air and the absorbing surface, where the concentration is kept to zero.
The example below shows the tuning of a point source model (Gaussian plume model IMMPROG) around a power station concerning sulfuric dioxide:
Left: illustration of the modelling results without any tuning.
Middle: the graph shows the correlation after the adaptation of the windfield to the actucal topography.
Right: the graph shows the coincidences after skipping the sites which where not included by the impact sphere of the plant.