The distribution of acid deposition in Germany

Abstract

The distribution of acid deposition by atmospheric precipitation in the Federal Republic of Germany is discussed, based on investigations of the wet H+-deposition during the five years 1980–1984, using a network of 16 automated samplers of our own construction located in various categories of ecosystems. Analytical problems of sampling and the electrometric determination of pH in rainwater are briefly discussed. Results for the average amounts of precipitation, the average H+-concentrations and average H+-depositions in the 16 typical regions of the Federal Republic of Germany are compared and the influences of meteorological parameters are discussed. An increase of the H+-concentration and H+-deposition values has been observed from 1980 onwards with a maximum in 1981 and a slow decrease in the next two years. The comparison of the values found for rural regions with those for more significantly polluted regions shows that in the latter regions the removal of H+-ions by wash-out is more effective. Whereas in the Ruhr region the pH is shifted to more acid values, due to the wash-out of acid particles and aerosols, in regions with metallurgical industry the pH is shifted to more alkaline values due to the wash-out of alkaline particles. In general the free acid in rain and snow is rather uniformly distributed over the whole area as a result of mesoscalic transport of the acid precursors SO2 and NOx and the concomitant formation of acid in the cloud droplets leading to acid deposition by rain-out. The composition of rainwater and the possibility of determining the proportion of the acid anions in rain which are of anthropogenic origin is briefly discussed.