Diffusion from a point source using combination between logarithmic and power laws of wind speed

In the present paper, a model for the diffusion of material from a point source in an urban atmosphere is incorporated. The plume is assumed to have a well-defined edge at which the concentration falls to zero. The vertical wind shear is estimated using combination between logarithmic and power laws under different stability conditions. Diffusion and advection of conservative material as it travels downwind is calculated. The concentrations estimated from this model were compared favourably with the field calculated of other investigators such as power and logarithmic law models. Also we calculate the concentration at the ground of the Iodine (I138) which agrees with the observed concentration value after adjusted its source strength.