Occurrence and risk assessment of antibiotic residues in Mediterranean olive grove soils with different management: an EU-wide pilot study.

Synthetic fertilizers used in agriculture are a major source of soil pollution. Sustainable soil management is crucial in maintaining long-term soil health and functionality. Implementing sustainable farming systems, such as organic farming, replaces synthetic chemicals with organic amendments of natural origin. Manure is one of the main fertilizers. However, it may contain antibiotic residues that may pose a risk to human and environmental health, such as the emergence of resistant bacteria or genes. In this study, a method based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was applied to determine the presence of nine antibiotic families in olive grove soils from five countries in the Mediterranean basin (Spain, Portugal, Italy, Greece, and Morocco) under different management systems, including traditional (TD), high density (HD), and organic (ORG). The results showed distinct patterns associated with the different soil management practices. ORG-managed soils exhibited the highest overall antibiotic concentration values; while TD and HD-managed soils showed lower median concentrations (0.23 - 5. 70 μg/kg). The study about antibiotic transportation through soil depth revealed that fluoroquinolones were retained more in the topsoil while sulfonamides stratified in some soil management systems. The toxicological risk assessment revealed that most of the detected antibiotics pose a low to negligible risk in olive grove soils.