An analysis of a dataset with nationwide information on multiple pollutants in groundwater indicates that clean groundwater is becoming rare. A total of 236 different substances were detected, three-quarters of which at less than 10 locations. As in the case of litter, local factors and activities determine the overall picture. Commissioned by the Groundwater Quality Monitoring Network Managers’ Platform, KWR conducted the analysis and presented the key results for general substances, pesticides, pharmaceuticals and other polluting substances. The project’s report was recently published in the magazine H2O.
Coordinated groundwater-quality monitoring campaign
Groundwater quality in the Netherlands is under pressure. For this reason provinces have been working together since 2015 in an effort to produce a uniform picture of the quality of groundwater. This led to the collection of a comprehensive dataset. A coordinated groundwater-quality monitoring campaign was conducted in 2015/2016 and 2018/2019 by the provinces, united in the Groundwater Quality Monitoring Network Managers’ Platform. This involved sampling 1,874 screens for inorganic substances, 1,517 screens for pesticides, 659 for pharmaceuticals and 669 for other anthropogenic substances. The dataset thus provides a broad picture of the substances that are decisive in the determination of the quality of groundwater at depths of 10 m and 25 m.
236 different substances
The analysis reveals that in about two-thirds of the sampled screens to the depth of 10 m, one or more anthropogenic substances were present above the signalling value levels. A total of 236 different substances were detected. By presenting them bundled in substance groups, KWR has made clear the pervasive human impact on shallow groundwater quality.
Local factors and activities are decisive in the development of the overall groundwater quality. This is reflected in the fact that 75% of the detected substances were found only incidentally (in fewer than 10 screens). This result elicits comparisons with litter: a diversity of sources and types of waste together produce a diffuse degradation of environmental quality and, in specific cases, even create nuisances or problems.
This study confirms the notion that humans have a large-scale impact on the quality of the groundwater in the Netherlands. Although this primarily concerns pesticides, a variety of emerging substances have also to be taken into account. So far, the spread of pharmaceuticals is by and large limited to areas where surface water has an influence, but components from various consumer products show a broader diffusion. Because emissions impact the groundwater slowly, and new substances might be of relevance, it is important to keep track of the development of groundwater quality.
Reducing groundwater pollutants
This coordinated monitoring and reporting represents an important step towards creating a uniform picture of the overall groundwater quality. The dataset offers ample material for follow-up research into local factors and activities associated with specific pollutants. By aggregating the data according to pollutant type or impact, patterns might appear and impacts possibly exposed. This would assist in the development of an action framework for the reduction of groundwater pollutants. Because of the slow flow of groundwater, the improvement of groundwater quality remains a long-haul question.