A three dimensional analytical mathematical diffusion model of air pollutant in a mixing layer with chemical reaction and wet deposition of larger particles of pollutants due to a point source at is furnished to investigate the primary pollutant concentration in a protected sector and it is above the earth surface layer of the earth’s atmosphere. The pollutants are assumed to be emitted only from a ceaseless source in surface layer. The physical phenomenon of the above problem is reduced to advection diffusion partial differential equation and is solved by using the method of Fourier’s technique. The effect of rate of chemical reaction of pollutants and rate of wet deposition of pollutants on the concentration of dispersed pollutants is investigatedfor both stable and neutral atmospheric situations. Concentration contours are plotted and the results are analysed for air pollutants in stable and neutral atmospheric situations. In the upper part of the mixing layer pollutants concentration is less in stable atmospheric condition for smaller roughness length and moderate geostrophic wind speed.