Estimation of the background contamination of the atmosphere from the chemical composition of precipitation

The relationship of marine and continental constituents in precipitation is considered and the values of the background concentrations for different geographical regions are defined. On the basis of these relations, conclusions are drawn concerning the geographical variations of the background contamination of the atmosphere and of the local source contribution, which depends on natural conditions and man's activity. Over the continental areas of the USSR the background level averages 30–40 % of the total contamination, the local sources contribute 60–70 %, of which 20–30 % can be attributed to natural sources (soil dust, etc.), and the rest to contamination of anthropogenic origin, the latter even for the most remote clean regions being about 20–30 %.