Deposition von Luftschadstoffen in der Schweiz: Entwicklung, aktueller Stand und Bewertung

Abstract

In total, the emissions of nitrogen, sulfur and other anthropogenic air pollutants in Switzerland were reduced in the last decades. This is the result of effective measures of the air pollution abatement policies. Sulfur input in forests today is nearly negligible due to a reduction of emissions by more than 90 percent. Regarding nitrogen emissions the picture is less consistent: they are reduced in consequence of the abatement of nitrogen oxides emissions from combustion processes, but ammonia emissions from agriculture show a considerably less pronounced reduction, and since the year 2000 they remain on a high level. In 2007 the average inputs in forests amounted to 24 kg nitrogen per ha and 4.8 kg sulfur per ha. Natural nitrogen input is 1 to 3 kg per ha and year. On nearly all forest sites (>95%) the critical loads for nitrogen were exceeded. Nitrogen input consists of roughly two thirds of reduced ammonia nitrogen from agricultural activities and one third of oxidized nitrogen from combustion processes (traffic, households, industries, commerce). In 2007 the acidification potential of nitrogen and sulfur input in forests on many sites was considerably higher than the amount of available neutralizing cations (Ca, Mg, K) from the weathering of minerals and their input with dust. Further efforts are necessary to reduce the nitrogen load in forests to a tolerable amount.