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.

According to the Waters Protection Ordinance (WPO), groundwater should generally not contain any persistent synthetic substances. For groundwater that is used for drinking water or is intended for such use, there is also a limit value ('numerical requirement') of 1 microgram per litre (µg/l) for volatile halogenated hydrocarbons (VHH) and monocyclic aromatic hydrocarbons (MAH); and of 0,1 µg/l for polycyclic aromatic hydrocarbons (PAH).

FHKW_2019_Karte_EN
Volatile halogenated hydrocarbons in groundwater (2019) and CHC-contaminated operating sites. Maximum values at each NAQUA monitoring site.
© FOEN

Volatile halogenated hydrocarbons most frequently detected

At more than 20% of monitoring sites nationwide, volatile halogenated hydrocarbons were detected in the groundwater, the limit value being exceeded at 3% of the monitoring sites. In predominantly urban catchment areas, VHH concentrations are above the limit value at more than 10% of the monitoring sites. The limit value of 1 µg/l is most frequently exceeded by tetrachloroethene.

Volatile halogenated hydrocarbons mainly originate from contaminated sites, such as contaminated former industrial or commercial plants or old landfills. In the past, these substances were used in large quantities as solvents and cleaning agents in industry and commerce and became present in the environment, primarily in the second half of the 20th century, because of inappropriate handling. Once in the groundwater, VHH resist degradation and therefore still contaminate the groundwater to this day.

In 2019 monocyclic and polycyclic aromatic hydrocarbons did not exceed their respective limit values. MAH were detected at 3% of monitoring sites, while PAH were only present at one monitoring site.

The petrol additive MTBE, for which the WPO does not prescribe a limit value, was detected at just under 3% of the monitoring sites in concentrations of up to 1,0 µg/l. The maximum level in drinking water prescribed by the Drinking Water Ordinance (DWBSO) of 5 µg/l for the combined presence of MTBE and ETBE was not exceeded.

Volatile halogenated hydrocarbons slightly declining

Between 2007 and 2019, the number of monitoring sites at which volatile halogenated hydrocarbons were detected in concentrations of more than 1 µg/l fell from just under 5% to 3%.

The number of monitoring sites with concentrations of tetrachloroethene above 1 µg/l also decreased significantly.

Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2019: 2.89017341040462 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2018: 3.05927342256214 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2017: 2.8735632183908 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2016: 2.86806883365201 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2015: 3.42857142857143 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2014: 3.79506641366224 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2013: 3.38983050847458 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2012: 3.57815442561205 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2011: 4.70809792843691 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2010: 4.70809792843691 Percentage of the NAQUA monitoring sites at which the numerical requirement of the Waters Protection Ordinance is exceeded 2009: 4.72589792060491

Data for the graph: Excel
Source: National Groundwater Monitoring NAQUA

Further information

Contact
Last modification 26.11.2021

Top of page

https://www.bafu.admin.ch/content/bafu/en/home/topics/water/info-specialists/state-of-waterbodies/state-of-groundwater/groundwater-quality/volatile-organic-compounds.html