In the presented work the Lagrangian stochastic dispersion model is applied to simulate the emission of pollutants (contaminant gas) from a point source above the ground. The obtained values of concentration in the region are presented graphically. Comparison with the analytical solution was carried out. Dispersion modeling in the convective boundary layer is performed, and sufficient grounds for using the model for the city of Tomsk are obtained. The considered Lagrangian stochastic dispersion model was applied to study the pollutants spread from high-altitude point sources in the city of Tomsk.