New aspects of buffering processes in stony soils

Cation exchange capacity (CEC) of different rocks (Sandstone, Clay-schist, Diabase, Basalt) was determined using different kinds of extractions. Re-exchange experiments were carried out. In addition, mineralogical and physical properties of the rocks were determined. Based on the base saturation (Mb-cation capacity) of a sandstone layer two scenarios of future acidification due to acid deposition were predicted. 1. only fine material (<2 mm) and 2. both, fine material and bedrock buffer by cation exchange. In the first scenario, it was calculated that it takes 8 years to desorb the Mb-cations completely, in the latter approximately 200 years. The results show that rocks are of significance not only for silicate weathering, but also for the cation exchange.