TRENDS IN THE COMPOSITION OF WET DEPOSITION - EFFECTS OF THE ATMOSPHERIC REHABILITATION IN EAST-GERMANY

The chemical components in precipitation largely depend on type and qu antity of emissions on the course of the air masses at the sampling si te. Beginning in 1982, the concentrations of major ions in precipitati on at initially 3 sites are described in total as well as arrival sect ors. For regions with specific geographical or emission features, 5 to 7 sectors for every sampling site are established, e.g., Scandinavia, or the centres of brown coal combustion in the former GDR. Particular y from the sectors of the former GDR, the precipitation was over-avera ged contaminated anthropogenically in the years before the political c hange. Some components were significantly raised in comparison to othe r sectors. However, acidity remained on the level of the other sectors in the 80s. In the early 90s, anthropogenic emissions were systematic ally reduced partly by substitution of brown coal of inferior quality, better flue gas cleaning and partly by closing down industries. The e ffect of such steps on the wet deposition is being studied in a nation al German SANA research project (SANA: scientific program of rehabilit ation of the atmosphere). In this project, the sampling sites were ext ended to 7 while maintaining the sampling procedure and the recording of relevant meteorological input-data. As a result, there now exists a homogeneous long-term data base allowing us to study the effects of e missions on wet deposition by the rehabilitation of the atmosphere in the former GDR. The paper focusses on changes in sulphate, nitrate, ca lcium, acidity, chloride and potassium concentrations in precipitation at the 3 so-called long-term sites. There are conspicuous decreases o f some ions on one hand, but there is also an increase of nitrate and acidity, especially in recent years.