Occurrence of pharmaceuticals and personal care products in the urban aquifer of Zaragoza (Spain) and its relationship with intensive shallow geothermal energy exploitation

A steady increase in the consumption of pharmaceuticals and personal-care products worldwide is increasing their occurrence in the biosphere. The current study describes the abundance of 42 selected emerging organic contaminants (EOCs), including human and veterinary antibiotics, UV-filters and analgesics in the groundwater of the urban aquifer of Zaragoza (Spain), which is affected by intensive exploitation of shallow geothermal resources. The presence of groundwater heat pump systems in the aquifer studied offered the opportunity to study the occurrence of EOCs in relation to groundwater temperature and other physicochemical effects derived from this technology. Analysis of the data obtained allowed us to identify statistically significant relationships between the presence of EOCs and temperature, as well as other physicochemical and geochemical properties of groundwater. The results obtained suggest that temperature is a minor factor controlling the degradation of the organic compounds analysed compared to the oxygen input from groundwater heat pump systems which is possibly increasing the aerobic redox conditions, thus preventing the degradation of organic pollutants. Intensive use of shallow geothermal resources therefore seems to contribute in the prevalence of such compounds in the aquifer close to geothermal systems