Numerical simulation of air pollutant transport and diffusion in a mountainous city

Abstract

The Monte-Carlo model is used to predict the ground-level concentration distribution (GLCD) of SO 2 in a mountainous city—Guiyang (107°E, 26° 43'N). The transformation of an instantaneous source and other problems of the model are improved. The wind fields are obtained from the objective analysis of three-dimensional wind observations and the turbulent parameters are determined by the parameterized formulae which were adjusted with the local experimental data. It shows the wind profile does not follow strictly the ordinary log-law and the extreme values of wind often occur in the layer of 50–500 m above ground level. The spectral peak of the velocity components u and v shifts to the lower frequencies and the horizontal diffusion increases remarkably. For the daily average values of GCLD in winter, the correlation coefficient between prediction and observation is 0.96. The GLCD simulation shows that the air-pollutant transport and diffusion in Guiyang is mainly dependent on the unstable weather conditions or the aeration effect of the extreme wind layer.