DESCRIBING SOIL SO42- DYNAMICS IN THE SOLLING ROOF PROJECT WITH 4 2 DIFFERENT MODELING APPROACHES

The release of previously stored soil SO42- is tightly connected with the reversibility of soil and water acidification. Thus soil SO42- dyn amics have to be included when predicting the reversibility acidificat ion. Our aim was to compare two modelling approaches: The model MAGIC (Cosby ct at, 1985) describes SO42- dynamics with the Langmuir sorptio n isotherme. In the SO-MODEL (Prenzel, 1991) a precipitation/dissoluti on of jurbanite is defined. Even though it was possible to calibrate b oth models to lysimeter data of the Selling D1 site in 1 m depth, the prognosis for SO42- concentrations in the soil solution differed signi ficantly. While MAGIC predicted the observed gradual decrease of SO42- concentration with decreasing deposition, the SO-MODEL calculated sta ble concentrations up to the year 2026 followed by a sudden drop. Beca use the prognosis established with the SO-MODEL is incompatible with o bserved field data, we concluded that the predicted SO42- dynamic of t he SO-MODEL was unrealistic.