On the relation between drop size and concentration of trace elements in rainwater

Rainfall has been separated according to drop-size spectrum with a drop-size discriminator of our own design. Chemical analysis of the different size fractions shows that small drops contain a higher concentration of impurities than large drops from the same rainfall. This result is valid for all components analyzed. The results can be explained on the basis of washout of trace substances and partial drop evaporation below the cloud base.