Abstract
In order to predict air pollution concentration from a road more precisely, it is important to clarify how atmospheric diffusion is influenced by the direction of wind to the road. In the present paper we mathematically derive a formula applicable for predicting air pollution concentration from infinite line source when the wind blows in oblique. It is assumed that the line source consists of numerous point sources. The air pollution concentration is obtained as sum of the concentrations from these numerous point sources, and therefore thes um is first expressed as integral form.
Gaussian plume formula is used in the calculation of the concentration from the point source. The dispersion parameters, σY, σz, are assumed as σY=αXα, σz=bXβ, respectively, where a, b, α and β are constants. We find that mathematically exact solutions can be obtained in the cases where α, β and the direction of wind, θ, are specific values. For example, when α=1, β=1, the concentration can be expressed in relatively simple form. Especially, when the observation point is on the ground, the concentration, C, is given as follows:
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and D is the perpendicular distance from the observation point to the road, U is the wind velocity, q is the strength of emission per unit length, and He is the effective height of emission source. Explanations of the effects of He and θ on the concentration are given.
