On the composition of precipitation water and its acidity

Abstract

The aim of this paper is to calculate the pH from the mean ionic composition of precipitation water published by several workers in the literature and to provide some characteristics of regional and source differences in rainwater. The calculated pH is compared to the “measured” mean pH based on precipitation-weighted hydrogen ion concentrations. Deviations are related to gaps in the anion-cation-balance. It has been found that in areas with high basic soil, particulate contribution to the atmosphere bicarbonate in rainwater plays an important rôle. In the vicinity of lignite-fired power plants, further basic contributors like oxides of Fe and Al seem to be of importance in the control of pH. Furthermore, some regional particularities in neutralizing capacity has been found. The percentage of basic species in European precipitation is twice as high as in North America, whereas no differences are found between eastern and western Europe. However, the nitrate share in eastern Europe in rainwater is less than in western Europe.