The criterion “filter and buffer for pollutants” is used, among other things, to evaluate the sub-soil function “leveling medium for material impacts”. “Filter and buffer for pollutants” means the ability of the soil to separate dissolved or suspended substances from their means of transport. The ability can be derived from mechanical or physico-chemical filter properties. Soil absorbs substances through deposition from the air or directly through anthropogenic application, transfers them and stores them primarily in the soil pores. Depending on the soil properties, the storage or filter potential varies. The evaluation of the criterion "filter and buffer for pollutants" is carried out by assessing the potential cation exchange capacity and the air capacity of the soil down to the soil depth of the effective root zone. The key data for this are: Soil type of the fine soil, coarse soil proportions, rooting depth, air capacity, soil density and humus content of the soil. The horizon and layer data of the guide profiles of the FIS Soil are used for the derivation. Soils on high slopes receive valuation discounts. The terrain position and the climatic site conditions are not directly evaluated in the assessment, although these are relevant for the water storage capacity.
