The Institute for Environmental Diagnosis and Water Studies (IDAEA-CSIC) and the Polytechnic University of Catalonia - BarcelonaTech (UPC) have carried out the most exhaustive analysis carried out to date of emerging contaminants in a coastal aquifer, in an experimental area located in the stream from Argentona, on the Maresme coast. The study, published in the Journal of Hazardous Materials, has identified 92 emerging contaminants in the aquifer, of which 44 reach the Mediterranean Sea, although in lower concentrations, showing the great degradation power that aquifers have over various toxic compounds. . The authors propose that some of these contaminants can serve as tracers to better understand the discharge process of the aquifer into the sea, which would help to better manage this water resource.
"Coastal aquifers are very difficult systems to study on a hydrogeological scale. In our case, the aquifer was very well characterized, which allowed us to apply high-resolution techniques to detect the presence and transport of emerging contaminants," says the researcher. IDAEA-CSIC Pablo Gago-Ferrero, lead author of the study.
The contaminants found are very varied, from plastic additives, industrial chemical compounds, biocides, medicines or personal hygiene products. Of all of them, the authors highlight six perfluoroalkyl substances commonly used in a multitude of products (coatings, varnishes, shoes, furniture...) and two drugs, since they are very persistent compounds. "The distribution of these substances throughout the aquifer allows us to better understand how groundwater discharges into the sea," explains Daniel Gutiérrez-Martín, IDAEA-CSIC researcher and first author of the paper.
The researchers indicate that these contaminants can reach the aquifer in various ways, for example, through the infiltration of water from the stream itself into the subsoil. "This water has a higher concentration of persistent compounds, since surface waters are more vulnerable to contamination than groundwater," explains Albert Folch, a UPC researcher and professor at the Higher Technical School of Road, Canal and Port Engineering. Barcelona, member of the Groundwater Hydrology Group (GHS) and coordinator of the experimental zone developed for the study of coastal aquifers. “On the other hand, the rain, as it passes through the city, carries toxic compounds that can leak into the subsoil. And, finally, it is also due to possible losses from the sewage system and the pipes that bring the treated water from the treatment plants, which ends up reaching the aquifer”, explains Folch.
"The most relevant aspect of aquifers, as corroborated by this study, is their ability to degrade contaminants naturally, since they are highly reactive systems," says Jesús Carrera, IDAEA-CSIC researcher, member of the Groundwater Hydrology Group and also coordinator from the experimental area.
The authors conclude that the ability of these analytical techniques to identify emerging chemical contaminants can be used to trace the origin of groundwater that reaches coastal aquifers, as well as the processes of contamination and degradation that they may undergo.
