Deposition of Anions and Cations Via Precipitation

Abstract

In 1987, the average ion concentrations amounted to 6.1 µg/g for sulphate, 5.3 µg/g for nitrate, 1.05 µg/g for chloride, 0.03 µg/g for fluoride and 2.1 µg/g for ammonium. While the sulphate values decreased to 2.6 µg/g in 1991, no significant trends were observed for the other ions. The pronounced dependence of the amount of precipitation on the wind direction (cf. Fig. 7.5) suggests that the wet deposition is predominantly influenced by sources located between west and south-southwest. This is confirmed in Figs. 8.1 and 8.2 for the most important ions SO₄ ^2-, NO₃ ^-, Cl^- and NH₄ ⁺. As is to be expected on the basis of Fig. 7.2, sulphate shows a behaviour similar to that of sulphur as determined by trace element analysis of the rainwater (Fig. 7.6). The contribution of the particulate phase is negligible in the case of sulphur (see Table 7.1). The sources for SO₄ ^2- lie in the western parts of Germany with a certainly marked component due to the conurbation of Hamburg. The main emitters of SO₂ are the power and district heating stations. A similar transport situation is valid for NO₃ ^-. Here, the main source is the NO_x-emitting motor traffic.