This paper deals with a model of admixture dispersal in the atmospheric boundary layer. The model developed is to be used in IBM-compatible computers. The wind field is determined by analytically solving three-dimensional non-stationary linear system of the atmospheric boundary layer equations that allow for orographic and dynamic inhomogeneity of the underlying surface and for the quasi-stationary sublayer. Admixture concentration is found by numerically solving semiempirical turbulent diffusion equation. To set the diffusion coefficients they are assumed to be proportional to the corresponding components of the Reynolds stress tensor. The results obtained using this model have been compared with the observational data and with those obtained using other models.