Abstract
The ground-level concentration profiles, derived from the analytical solution of the atmospheric diffusion equation for a line source and for the wind speed and vertical dispersion coefficient expressed by Schmidt's conjugate power laws, can be exactly reproduced by the Gaussian plume model if, for an elevated source, both σz and u are functions of downwind distance, stability and source elevation, while for ground-level emission u is constant. On the basis of the above considerations, the applicability of the Gaussian model to the neutral case, in which the vertical dispersion coefficient is represented by an exponential law, is investigated. Since only numerical solutions to atmospheric diffusion equation can be derived in this case, σz and u are determined by minimizing the difference between the numerical ground-level profile and the one given by the Gaussian model. The reported results prove that Gaussian model can approximate very accurately the ground-level concentration profile solution to the atmospheric diffusion equation both for ground-level and elevated sources. In addition, for ground-level emission the estimated values of σz lie in the range of Pasquill-Gifford values given for stability classes C and D.
