Environment Basel area groundwater is contaminated with numerous trace substances

The groundwater in the canton of Basel-Landschaft is contaminated with numerous trace substances from industry, agriculture and households. This is shown in an investigation report by the Office for Environmental Protection and Energy (AUE), which was published on Friday. The AUE sees a need for action to protect the groundwater.

It concludes that all groundwater sources in the canton are contaminated with various trace substances. "Practically every measuring point has also shown one or more exceedances of the required values in accordance with the Water Protection Ordinance in recent years," the report states. Especially in densely populated areas, the groundwater is at risk or already contaminated with numerous substances.

However, the concentrations of trace elements measured did not lead to a restriction of use in any aquifer. The groundwater quality is comparable to that of the whole of Switzerland. Furthermore, no drinking water had to be treated as a result of the findings. The groundwater in the canton is generally of "good quality", meaning that it only needs to be treated with simple treatment processes for drinking water use.

Challenge for drinking water treatment

However, the AUE also states that this could change if pollution continues: "If the increase in the input of trace substances continues and the pollution of the groundwater continues to increase, it can no longer be consumed without treatment to remove trace substances," the report states. The problematic substances can only be removed with great effort, which poses an additional challenge for drinking water treatment.

In some parts of the canton, pesticides are widespread and are just as common as in Switzerland as a whole. Depending on the groundwater area, between 40 and 50 substances of the 360 pesticides analyzed were detected. The small streams in the intensively farmed area are significantly contaminated with pesticides, as the AUE writes. The increased concentrations in the more urban areas of Muttenz and Pratteln are mainly due to the use of pesticides in the freight yard.

AUE calls for fewer pesticides

In order to reduce groundwater pollution in the long term, the AUE suggests reducing the use of pesticides. The planned expansion of wastewater treatment plants with a fourth purification stage could also help, as could the maintenance of sewer pipes and the remediation of contaminated sites.

The AUE analyzed almost 800 different substances at over 800 measuring points over a period of ten years. In contrast to the national "Naqua" measurement, the investigation not only looked at groundwater with drinking water collection, but also at entire groundwater areas in order to gain a more complete picture, according to the report. With the observations at other monitoring sites, significantly more pollution can be identified. Therefore, "further efforts" are needed in terms of operational water protection, urban drainage and agriculture