Lagrangian Modelling of Dispersion in the Planetary Boundary Layer of Particulate Released by a Line Source

Abstract

Formulating and solving the diffusion-deposition-resuspension problem of particulate released in the planetary boundary layer is of primary importance in assessing their environmental impact. Solid particles are originated, as it is well-known, both by industrial processes (releases from industrial stacks) and by natural processes (e.g. formation of aerosols droplets by chemical reactions in the atmosphere). The physical mechanisms governing the evolution of particles in the atmosphere have been largely investigated in recent years both in laboratory studies and on the field. For instance, as far as the mechanism of dry deposition is concerned, a detailed review of available results has been compiled by Sehmel (Sehmel G.A., 1980). Modelling of dispersion of solid particles has been generally achieved by suitable modifications of the models available to treat dispersion of gaseous pollutants. Most of these models are therefore based on the Gaussian formulation and are the most used in real world applications. More complex modelling based on the eddy-diffusivity approximation has been recently developed to study the evolution of particles in the plumes of coal-fired power plants (see e.g. Hobbs et al., 1979). This complex model includes, besides the usual mechanisms of advection and diffusion, significant phenomena as particle coagulation, and gas-to-particle conversion both in homogeneous and in heterogeneous phase.