Soil assessment — Total filter effect (GFW), uniform across the country

The overall filter effect is a characteristic for evaluating the soil as a filter for sorbable substances and is evaluated by the mechanical and physico-chemical filtration capacity. Sorbable substances in particular include groups of substances such as the cations of nutrients, heavy metals and organics, which are either dissolved in soil water or adhere to small particles or even present in particulate form. In dissolved form, the said substances are bound to the exchangers (soil material) and thus removed from the soil solution. In particle form, they are filtered in the ground if they can no longer be transported with the leachate due to mechanical obstacles, such as at the end of worm tubes. The overall filter effect can be estimated depending on cation exchange capacity and air capacity. The estimation result consists of a total of 11 stages, of which only 8 are relevant in Schleswig-Holstein. The higher the level, the higher the overall filter effect. It is the largest in fine-grained soil material with low air capacity, such as in the march and in the Eastern Hills, and in coarse grain soil material with high air capacity, such as in the foregeest. With the overall filter effect, a natural soil function is assessed in accordance with Section 2(2) of the BBodSchG, in accordance with point 1.c) as a degradation, balancing and superstructure medium for material effects due to the filter, buffer and substance conversion properties, in particular for the protection of groundwater. The criterion chosen for this purpose is the mechanical and physico-chemical filtering capacity of the soil with the characteristic value of total filter effect. The maps are available for the following scale levels: — 1: 1,000-10 000 for high-resolution or parcel-sharp planning, — 1: 10,001-35,000 for municipal planning, — 1: 35.001-100,000 for planning in larger regions, — 1: 100.001-350,000 for nationally differentiated planning, — 1: 350,001-1000,000 for nationwide to nationwide planning.