Volatile organic compounds (VOCs) occur in groundwater in concentrations above 1 µg/l at up to 4% of the monitoring sites sampled throughout Switzerland. In urban areas the VOC concentrations are above this level at 14% of the monitoring sites.
In 2013 concentrations of volatile organic compounds (VOCs) were above 1 µg/l at 4% of the NAQUA monitoring sites. VOCs were detected at 27% of the monitoring sites.
The most commonly detected VOCs were volatile halogenated hydrocarbons (VHHs). Particularly Tri- and tetrachloroethylene were identified frequently; the concentrations of tetrachloroethylene were also above the requirement in the Water Protection Ordinance (GSchV) of 1 µg/l for VHHs at a relatively large number of monitoring sites. Both chemicals are used among other things as solvents in textile cleaning and the metal processing industry. They do not decompose readily in groundwater.
Another substance frequently detected in groundwater is methyl tert-butyl ether (MTBE) which has been added to petrol as an antiknock agent since the mid-80s. MTBE is water soluble and relatively persistent in the subsoil because it does not bind easily to soil particles and is hardly broken down by microorganisms.
Monocyclic aromatic hydrocarbons (MAHs) were found much less often in the groundwater.
The highest impact of VOCs on groundwater occurred in settlement areas: In 2013, the concentration of VOCs was above 1 µg/l at around 14% of the monitoring sites located in settlement areas.
Last modification 29.08.2018