Unternavigation

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

Nitrate exceeds the limit value of 25 mg/l in groundwater at 15% of monitoring sites across Switzerland. In areas where arable farming is predominant, concentrations are above the limit at nearly 50% of monitoring sites.

Pesticides

Pesticides exceed the limit value of 0.1 micrograms per litre at 1 to 2% of monitoring sites every year. In addition, pesticide degradation products (known as metabolites) occur in concentrations of more than 0.1 micrograms per litre at one in three groundwater monitoring sites across Switzerland. Metabolites significantly impair the quality of groundwater, particularly on the Swiss Plateau.

PFAS

Per- and polyfluoroalkyl substances (PFAS) are found in Swiss groundwater at almost half of the NAQUA monitoring sites. PFAS concentrations exceeding 0.1 micrograms per litre in groundwater are frequently due to the use of firefighting foams containing PFAS. These chemicals can also reach groundwater from landfill sites or via infiltration of river water.

TFA

Trifluoroacetic acid – TFA – is present everywhere in groundwater. However, concentrations differ clearly depending on the location: TFA pollution is significantly higher under arable land. TFA enters groundwater on a large scale due to the use of plant protection products. At lower concentrations, TFA is also transferred to groundwater by precipitation. TFA found in precipitation originates primarily from gas refrigerants and propellant gases. In particular cases, the discharge of treated industrial wastewater into watercourses can lead to considerable contamination of groundwater with TFA.

Volatile halogenated hydrocarbons

Volatile halogenated hydrocarbons (VHH) exceed the limit value at nearly 3% of monitoring sites. In contrast, monocyclic aromatic hydrocarbons (MAH) and polycyclic aromatic hydrocarbons (PAH) are only rarely found.

Pharmaceuticals

Pharmaceuticals occur in groundwater at around 15% 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.

Major constituents

Substances that occur in groundwater in concentrations of several milligrams per litre, such as chloride and sulfate, are known as major constituents. They generally enter groundwater naturally from soil and rock. In settlement areas and especially along roads, chloride can also originate from the use of de-icing salt, which consists of sodium or potassium chloride. Around 4% of monitoring sites in Switzerland exceed the chloride limit value of 40mg/l.