Occurrence and fate of emerging contaminants (antibiotics) in an alluvial aquifer and their effect on multi-resistant bacteria (Baix Fluvia, Catalonia)

The release of Emerging Organic Contaminants (EOCs, and particulary, veterinary antibiotics) into the environment from the use of manure as fertilizers in agriculture is a major concern in water quality. EOCs can also pose a risk to human health due to the appearance of multidrug resistant bacteria. This study aims to improve the knowledge on the occurrence and migration of a selection of EOCs and their influence on multi-resistant bacteria in both surface and groundwater. The study site is located in the Fluvia alluvial aquifer in the Emporda basin (NE Catalonia, Spain). Samples were collected from 47 wells, 7 samples from surface water and 2 samples from waste water treatment plant effluents. All samples were analyzed for hydrochemical, isotopic, EOCs and antibiotic resistance genes. Up to 11 antibiotics were found in groundwater (concentrations in the order of ng/L) corresponding to 4 chemical groups: fluoroquinilones (ciprofloxacin, danofloxacin, enrofloxacin, norfloxacin, ofloxacin and orbifloxacin), macrolides (azithromycin), quinolones (flumequine, oxolinic acid, pipemidic acid) and sulfonamides (sulfamethoxazole). In surface water samples, 5 different antibiotics were quantified from 2 chemical groups: fluoroquinilones (ciprofloxacin, enrofloxacin, norfloxacin and orbifloxacin) and sulfonamides (sulfamethoxazole). Results also show positive resistance of the microbial communities to antibiotics in polluted sampling points. This field study points out the multifaceted aspects of antibiotic pollution that finally control the impact on groundwater quality.