Chemical composition of precipitation in regions of the Soviet Union

The relative importance of two mechanisms, the formation of droplets on condensation nuclei and the capture of contaminants by cloud and precipitation elements in various atmospheric layers, is evaluated. Calculations show that in the clean northern regions of the USSR the cloud contribution constitutes 55% of the total precipitation mineralization. In the southern regions, with heavy pollution of the atmospheric boundary layer, the washout of pollutants in the subcloud layer is the predominant process. Here the cloud contribution constitutes only 20–25%. Therefore, precipitation plays a significant role in the self-cleaning of the atmosphere from admixtures of natural and artificial origin.