Trace elements in precipitation and cloud water in the area of Heidelberg, measured by instrumental neutron activation analysis

Abstract

The concentrations of 17 trace elements in rain water residues, collected in Heidelberg (April–June 1971) were determined by thermal neutron irradiation in a flux of 3 × 10 11 n cm −2 s −1 and γ-ray spectrometry using Ge(Li)-detectors. Cloud water was collected aboard an airplane at different heights from stratiform clouds and treated like rain for comparison of the trace element concentrations in rain and cloud water. Considering the concentration of an element, i, relative to the concentration of the element sodium, three groups of elements were found, the main sources of which were presumed to be the ocean (Cl, Br), the earth's surface (La, Fe, Sc, Mn, Cr, Sm) and anthropogenous production (Ag, Sb, Co). A comparison of cloud and rain water concentrations shows constant values inside the cloud between 3500 and 2500m, decreasing concentrations between 2500 and 2000 m, and constant or increasing values for all elements not originating in the ocean between the lowest cloud level and the earth's surface. The concentrations of elements which are specific for an aerosol production on the surface of the ocean increased with height, due to the special meteorological situation.