An Analytical Air Pollution Model: Eddy Diffusivities Depending on the Source Distance

Conclusions

This paper describes the development and testing of an analytical model that simulates the dispersion of contaminants into a convective boundary layer. The model is based on the advection-diffusion equation which is solved by the Laplace transform technique. This model assumes vertical eddy diffusivities varying with the distance from the source and related with the turbulence properties (inhomogeneous turbulence). The inclusion of eddy diffusivities as function of downwind distance has been often cited as something to be included in analytical dispersion models in order to take into consideration the different physics aspects of near-source and far-source dispersion. To investigate the turbulence memory effect for low and tall stacks a numerical comparison, using the well-known Copenhagen and Prairie Grass datasets, is also performed with results derived from a simulation using a vertical eddy diffusivity valid for large diffusion time and that is only dependent on the turbulence properties. It is also important to emphasize that the concentrations simulated by the eddy diffusivities depending on the source distance are better than the ones simulated by the asymptotic eddy diffusivity valid only for the far field of a continuos point source.