Is the prediction of fluoroquinolones adsorption in soils still valid in presence of metal trace elements? - Towards a robust predictive approach

Given the simultaneous presence in the environment of fluoroquinolones and metal trace elements and their ability to form new species by complexation, it is crucial to accurately predict their retention and mobility in soils under realistic context of multi-contamination. This study compares the adsorption on ten soil samples of ciprofloxacin and enrofloxacin, in the absence and presence of nickel, copper, and zinc. The objective is to assess if the models established in their absence remain valid or require further modification taking into account their interaction by complexation. It was shown that prediction models neglecting metal complexation underestimate the soil retention of fluoroquinolones and thus overestimate their mobility, leading to inaccurate risk assessments. This effect is particularly pronounced in alkaline soils, with fluoroquinolone adsorption increasing in the order Zn < Ni < Cu. A significantly improved agreement between modeled and experimental adsorption data was achieved by incorporating the speciation of fluoroquinolones, including their complexation with metals, as inputs to the model. This study highlights the need to consider metal-antibiotic interactions in predictive models to enhance the reliability of environmental risk assessments for fluoroquinolone antibiotics, with implications for soil quality assessment, water treatment processes, and regulatory decision-making.