Groundwater quality

Groundwater does not naturally contain any persistent synthetic substances. Nitrate and residues of plant protection products have a long-lasting adverse impact on groundwater quality. Along watercourses, micropollutants from industry, commerce and households are also found in groundwater.


Nitrate exceeds the limit value of 25 mg/l in groundwater at almost 15 % of the monitoring sites across Switzerland. In areas where arable farming is predominant, concentrations are above the limit at more than 40% of the monitoring sites.

Plant protection products

Residues of plant protection products (PPPs), i.e. their active substances as well as their degradation products, occur at over half of the groundwater monitoring sites across Switzerland. In intensive arable farming areas, residues of PPPs are detected at over 90% of the monitoring sites.

Volatile organic compounds

Volatile halogenated hydrocarbons are the most frequently detected volatile organic compounds (VOC) in groundwater, exceeding the limit value at 3% of monitoring sites. In contrast, monocyclic aromatic hydrocarbons (MAH) and polycyclic aromatic hydrocarbons (PAH) are only rarely found.


Pharmaceuticals occur in groundwater at around 10% of the monitoring sites throughout Switzerland. Groundwater resources in unconsolidated aquifers next to rivers are the most affected. The pharmaceuticals enter rivers and streams via sewers and sewage treatment plants, and finally infiltrate into groundwater.

Perfluorinated chemicals

Residues of perfluorinated chemicals occur primarily at groundwater monitoring sites near rivers. The discharge of treated or untreated wastewater into surface waters and the subsequent infiltration of these waters into groundwater appear to be the major source of PFC in Swiss groundwaters.

Further information


Last modification 10.03.2021

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