A.T. Celada and A. Salcido (Mexico)
Brownian coagulation, turbulent coagulation, turbulent dispersion, transport, assesment, polydisperse aerosol.
A simple model to analyze the effect of coupling of coagulation and atmospheric dispersion in polydisperse aerosols is proposed. For the coagulation process this model does not assume a monomer structure of the aerosol particles. Instead it uses a probabilistic estimate of the production rate of the aerosol particles which depends on their diameter ranges, and assumes that only binary collisions may occur, that collisions preserve mass and volume, and that the colliding particles always coagulate. The dispersion process of the aerosol is considered through a simple 3D Monte Carlo simulation model where the mass fluxes are estimated through the mean wind field and the distribution function of the wind velocity turbulent fluctuations. Both processes were coupled in formulating the mass balance equation of the model. We used the model to perform a numerical simulation of the aerosol steady state behavior around an emission source burning coal. The spatial distribution of the number densities as function of the downwind distance from the emission source is presented. Near the source (up to 80m), a very fast consumption of the smallest aerosol particles (with diameters smaller than 0.120 µm) is observed. At larger distances, particles with diameters between 0.120 and 0.960µm are accumulated. This accumulation persists up to very large distances. Qualitatively, at least, this behavior is in agreement with the experimental data [1,2].
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