Contaminants of emerging concern in urban aquifers: Do they limit the use of groundwater?

Water resources are affected by climate change, especially in the south of Europe, where droughts will be more frequent, intense and long. Hence, research into alternative sources of freshwater, such as urban groundwater (UGW) is essential.  Urban aquifers are a potential solution to obtain freshwater, but they are frequently polluted by contaminants of emerging concern (CECs). Therefore, there is a need to ascertain whether CECs are a water management challenge as they might limit the use of groundwater as safe drinking water. To answer this question, it is required to assess the human health-risk effects of CECs in the groundwater and to understand their subsurface behaviour at a field-scale. This research compiles data about the presence of CECs in the aquifers of the Barcelona city and its metropolitan area, evaluates health risk effects of measured CECs in the groundwater and presents approaches implemented to identify and quantify the coupled hydro-thermo-chemical processes that govern the fate of these substances in the subsurface. Based on detected concentration in urban groundwater, there are some CECs that might be harmful to humans such as 5-methyl-1H-benzotriazole and the pharmaceuticals azithromycin valsartan, valsartan acid, lamotrigine, venlafaxine and lidocaine, which show very high to intermediate health risk effects. The number of harmful CECs and the level of their hazard increase from the groups of adults and teens to those of 4 – 8 and 1 – 2 years old children. Thus, some CECs can limit the use of groundwater in Barcelona as potential drinking water source. Finally, knowledge gaps in understanding how to integrate these processes into urban water resources management plans are highlighted, which will help to define groundwater potential uses and to assure protection of the human health