We present analysis of data on sulfur dioxide concentrations in Irkutsk surroundings in winter-spring 2005 obtained with a gas-analyzer and juxtapose these data with meteorological conditions for the same period. The numerical model of dispersal and transformation of admixtures used helps to reveal the areas with increased level of pollution by sulfur compounds in the Lake Baikal region. Calculated and measurement data on sulfur dioxide concentrations are in a good agreement. Types of meteorological conditions favoring to the atmospheric pollution have been determined. Areas of maximum concentrations of ozone have been calculated. It has been revealed that the speed and direction of winds and concentration of water vapor influence the dispersal and transformation of the admixtures.