The National Soil Monitoring Network NABO historically focuses on the maintenance of soil fertility, as decided politically in the Ordinance on the Pollution of Soil (VBBo). Accordingly, the heavy metal contents in soil have been assessed since the mid-1980s. The time sequences of the results from these measurements show that some of the environmental measures implicated in recent years have been effective. In general, heavy metal emissions have declined, as illustrated by the measured contents in the soil.
Many heavy metals enter the soil primarily via external inputs such as atmospheric deposits, fertilisers or pesticides. Some occur naturally at elevated concentrations. Certain heavy metals, at low concentrations, are essential for humans, animals and plants, whereas others are toxic at very low concentrations.