Hydrochemistry and presence of emerging organic pollutants in groundwater of the urban Barcelona area

Groundwater is a vital resource for the development of urban areas where the problem focuses on the quantity as well on the quality, which constituted a challenge to be faced, an example of this is the case of Barcelona. Currently, Barcelona groundwater is used for irrigation of parks and gardens and street cleaning due to its poor quality as a source of drinking water, in addition, there are numerous pumping in the city to prevent flooding of underground structures (e.g. subway). Barcelona is a developed city with a high population density. Due to the socio economic, industrial activities and lifestyle of its inhabitants, as is common in urban areas, there has been a progressive deterioration on the quality of its water. Among the pollutants found in these waters, of special interest are the emerging organic contaminants (EOCs), which present a high risk to the aquatic environment and human health. The behavior, spatial distribution and processes that control them in the aquatic environment are still uncertain and most of them are unregulated.

In this work, the use of classical hydrogeochemical techniques, GIS, univariate, bivariate and multivariate statistical analysis and geostatistical techniques allow to assess, identify and locate the main physicochemical processes that control the composition of this waters considering the inorganic and organic (EOCs) parameters and the correlations between them.

isotopic analysis of the SO₄^2- molecule, , corroborated the significant contribution of wastewater in the composition of these waters. The analysis of the EOCs showed that the highest concentration of these compounds is located towards the Besòs River. This fact indicate that this would be the main source and of greater magnitude of input of EOCs into the aquifer, while towards the urban area of Barcelona the abundance of EOCs would originate from sewage filtrations, where the input is of a lesser magnitude, this was corroborated with the factorial analysis of the EOCs. The areas with reducing conditions in general showed a higher concentration of these compounds, indicating that most of them would degrade more easily in oxidizing environments.

The processes and/or contributions identified are: water-rock interaction, water mixing, redox processes, aquifer-river interaction, sewage seepage and infiltration of urban runoff. The high heterogeneity found in the physicochemical parameters and EOCs would denote the complex hydrogeological situation of the system. the abundance of EOCs found in these waters together with the isotopic analysis, would indicate that the main source of recharge for most of this samples should be anthropogenic, mostly wastewater (sewage seepage or aquifer-river interaction).