VOC in groundwater
Volatile organic compounds (VOC) are mainly used as solvents, coolants or raw materials in industry and commerce. Motor fuels also contain VOC. These substances can reach groundwater due to incorrect handling during production, transport or storage and during use and disposal. Volatile halogenated hydrocarbons (VHH), in particular from contaminated sites, can pollute the groundwater.
Groundwater is Switzerland’s main drinking water resource. Over 80% of Swiss drinking water is extracted from groundwater.
At around 5% of NAQUA monitoring sites across the country, the concentration of volatile organic compounds is above the numerical requirement of the Waters Protection Ordinance (WPO) of 1 µg/l applicable to volatile halogenated hydrocarbons and monocyclic aromatic hydrocarbons. The concentrations are generally highest in the developed areas, where the numerical requirement is exceeded at 15 to 20% of monitoring sites. The most serious problems are caused by volatile halogenated hydrocarbons. They are responsible for nearly all cases of the numerical requirement in the WPO being exceeded.
To reduce groundwater pollution specifically from volatile halogenated hydrocarbons, contaminated sites are being systematically recorded and rehabilitation measures undertaken on those which pose a risk to groundwater.
Due to different general conditions, a direct international comparison of statistical data is not possible.
The concentration of volatile organic compounds (VOC) in Swiss groundwater is recorded at national level under the NAQUA National Groundwater Monitoring. The NAQUA monitoring network covers 545 monitoring sites and is operated by the Federal Office for the Environment in close cooperation with the cantonal authorities. The NAQUA long term monitoring tests for 40 different VOC. The maximum value per NAQUA monitoring site per year is used for the statistical analyses.