Occurrence and fate of pharmaceuticals in urban groundwater

Sustaining healthy living conditions in urban areas is a tremendous challenge in the European Union, and central to this mission is the supplying of freshwater resources. However, rapid urban growth and climate change will negatively impact water resources. Therefore, water shortage is encouraging research into potential alternative freshwater resources such as urban groundwater. Sometimes, urban groundwater is pumped to prevent damage to underground structures. This is the case of the underground parking lot of Sant Adrià del Besòs (Barcelona, NE Spain), where large amounts of urban groundwater are pumped to avoid seepage problems, which are directly poured to the sewage system.  This consideration ponders if this urban groundwater might be used as safe drinking-water because urban aquifers contain a vast array of pollutants such as pharmaceuticals.

This work investigated the occurrence and fate of more than 100 pharmaceuticals in the shallow aquifer of the Besòs Delta River, which main contamination source is a polluted river that receives discharges from wastewater treatment plants. To this end, river and groundwater samples were collected from February to May 2021 for the analysis of pharmaceuticals using a solid-phase extraction and high pressure liquid chromatography coupled to high resolution mass spectrometric methodology (HPLC-HRMS). Preliminary results showed that, in more than 70% of the samples, several pharmaceuticals such as anticonvulsants, antihypertensives, antibiotics, and antivirals were detected. More precisely, 38 substances were detected in all river samples and 15 were ubiquitous in groundwater samples.  The range of concentrations for all the compounds was between 2 ng/L and up to 880 ng/L. Moreover, the behavior of the compounds along the bank filtration until reach the pumping site, close to the parking lot, suggested that the natural attenuation of the pharmaceuticals likely to adsorption or oxidation-reduction processes occurred, as groundwater sampling points located close to the river presented the highest concentrations for the detected substances.  This observation allows inferring that the pumped urban groundwater could be used for different purposes including drinking water but further studies are required to quantify the coupled processes that control their fate in urban aquifers.