Simulação tridimensional da dispersão de poluentes na atmosfera em condições de vento fraco

Abstract

The importance of dispersion modeling in low wind conditions lies in the fact that such conditions occur frequently and are crucial for air pollution episodes. In such conditions, the pollutants are not able to travel far and thus the near-source areas are affected the most.The classical approach based on conventional models, such as Gaussian puff/plume or the K-theory with suitable assumptions, are known to work reasonably well during most meteorological regimes, except for weak and variable wind conditions. The reasons for that are: the down-wind diffusion is neglected with respect to advection; the concentration is inversely proportional to wind speed; the average conditions are stationary and there is a lack of appropriate estimates of dispersion parameters in low wind conditions. The present study proposes a mathematical model for dispersion of contaminants in low winds that takes into account the along-wind diffusion. The solution of the advection-diffusion equation for these conditions is obtained applying the 3D-GILTT method (Three-Dimensional Generalized Integral Laplace Transform Technique). The study suggests that the inclusion of the longitudinal diffusion, important at short distance diffusion from a continuous point source in low wind conditions, can improve the description of the turbulent transport of atmospheric contaminants.