A national inventory of deep and shallow groundwater, conducted by KWR on the basis of provincial measurement data, reveals the presence in three-quarters of the groundwater of pesticides, pharmaceuticals and other contaminants. Chemicals were found in practically all of the shallow groundwater. The study’s results are important for provinces, as managers of the groundwater, but also for water companies, waterboards and authorities that regulate chemical use.
On a commission from all of the Dutch provinces, KWR used data on the presence of chemicals in groundwater in 2015-2016 to produce a single national picture, including zones both within and outside of the groundwater protection areas used for drinking water production. ‘Never before has such an extensive picture been drawn up,’ stresses Prof. Annemarie van Wezel, Principal Scientist at KWR. ‘As the managers of the groundwater, the provinces can designate strategic groundwater supplies, and the national government delimits national groundwater reserves. The aim being to dispose in the future, if needed, of clean water sources separate from the current abstraction sites. In this context, a clear view of the groundwater quality is extremely important.’ The research involved the analysis of about 1,000 samples of deep and shallow groundwater for the presence of 280 pesticides, and about 500 samples of shallow groundwater samples for the presence of 210 ‘emerging contaminants’, including 100 pharmaceuticals.
Exceedance of European standards
Practically all of the analysed shallow groundwater contains chemicals; this is also the case for two-fifths of the deep groundwater samples. The European standard for individual pesticides under the Groundwater Directive is 0.1 micrograms per litre (0.1 µg/L). The research shows that 17% of Dutch groundwater does not meet this standard. The highest concentrations occur in bulb-growing areas and in the North-Brabant sandy grounds.
The most detected chemicals in groundwater are the pesticides bentazone and mecoprop, and the metabolites DMS and BAM. In groundwater protection areas, the standard is exceeded by three pesticides: bentazone, dimethomorf and dicamba. This indicates that the measures limiting the use of these approved agents are still falling short of having the desired effect.
Pharmaceuticals and other chemicals
For substances other than pesticides (‘other anthropogenic substances’), the Decree on Quality Objectives and Monitoring for Drinking Water Sources sets a signalling value of 0.1 µg/L. The study detected pharmaceuticals in a quarter of the groundwater samples; this involves primarily phenazone and carbamazepine. The signalling value for these substances was exceeded in 5% of the cases.
Other chemicals exceed the signalling value in half of all of the samples. Substances regularly detected are EDTA, bisphenol A and PFOA; of these, only PFOA is sometimes present in concentrations at which a health hazard cannot be excluded.
‘Many people perceive groundwater as being clean,’ says Annemarie van Wezel. ‘But this research shows this not to be the case. In itself, this isn’t so surprising, given the huge increase in the use of synthetic chemicals.’ Even though good drinking water is currently produced from groundwater – and there is therefore no question of a problem today – the extensive spread of chemicals in groundwater will make it increasingly difficult to continue producing clean drinking water into the future. The technology will have to respond accordingly. ‘But source protection is also of primordial importance, as it is for surface water.’