The Effect of Rain washout on Dispersion of Pollutant from a Point Source under Low and High Wind Conditions

Abstract

A comparative study has been made on the effect of rain washout under low and high wind conditions on the steady dispersion of air pollutant from a continuous point source located at the origin. We assume that there exists uniform distribution of rain droplets in a region near a point source. A mathematical model was formulated for both cases with a consideration that under high wind condition the wind component is considered to be only in x direction and neglecting diffusion in comparison to advection in the x direction where as under low wind condition we take into account the diffusion in all coordinate direction along with component of wind velocity in x and y directions. In addition, to this we also consider a removal parameter due to rain washout process in both cases. The concentration of absorbed pollutant in rain droplets was governed by a simplified partial differential equation which takes into account the falling of rain droplets but ignores diffusion.

An analytical solution was obtained using the Fourier transform by using appropriate boundary conditions. The result shows that the rain washout process helps in removing the pollutant in both cases but under high wind condition the concentration level of pollutant becomes low as compared in low wind condition.