Healthy soil is essential for life in and on the soil. Understanding the soil’s composition is a precondition for protecting it. The Geochemical Soil Atlas compiled by Agroscope and the Federal Office for the Environment marks the first nationwide overview of 20 chemical elements and their concentrations in Swiss soil (see below). It covers elements which are relevant for soil fertility as well as those which – at too high concentrations – are harmful, such as copper or zinc. The new atlas serves as a valuable tool for soil protection at both cantonal and national level.

Regional differences and hotspots

Although the measured element concentrations are comparable with those of European soils, there are clear regional differences, with high element concentrations frequently recorded in the Jura and the Eastern Central Alps compared with the rest of Switzerland. However, areas with comparatively high occurrences are mostly restricted to known hotspots where further investigations into possible pollution have already been carried out or are still ongoing. The measured concentrations at most of the sites investigated lie within a non-hazardous range. In contrast, topsoils in the Swiss Plateau tend to have medium to low element concentrations, especially in the case of sulphur, which is an essential element for crop production, e.g. oilseed rape. In future it may be necessary to apply more fertiliser to this crop in the Swiss Plateau, although further investigations are needed.

No plot-level information

The Geochemical Soil Atlas is based on soil analyses with a resolution of around one sampling site per 35 km2. As such, plot-level information cannot be derived from it. The regional distribution of element concentrations is visualised in maps which are available on the Swiss Federal Office of Topography swisstopo website and in the Swiss geographic catalogue geocat.ch. These maps provide the agencies with a basis for identifying areas where further investigations are required.

The Geochemical Soil Atlas is currently available in German in electronic form. It will be published in French, Italian and English and in printed form in March 2024.

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What is the purpose of the Geochemical Soil Atlas?

In Switzerland, the cantons are responsible for monitoring and assessing soil pollution, and it was their desire for a nationwide, harmonised database showing areas with potentially elevated background concentrations that prompted the creation of the Geochemical Soil Atlas. In addition, knowledge of typical concentrations of trace elements in Swiss topsoil is vital for updating threshold values in the Swiss Ordinance on Soil Pollution (VBBo). The Federal Office for the Environment together with one of the cantonal environmental protection agencies’ working groups commissioned a team of Agroscope researchers, ETH Zurich and the Swiss Federal Institute of Aquatic Science and Technology Eawag to compile the Geochemical Soil Atlas of Switzerland. The atlas covers the following elements: antimony, arsenic, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, mercury, molybdenum, nickel, sodium, sulphur, thallium, uranium, vanadium and zinc.

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Soil Atlas Depicts the Distribution of Chemical Elements in Swiss Soils