Relevance of sorption in bio-reduction of amoxicillin taking place in forest and crop soils

Abstract

The fate of antibiotics reaching soils is a matter of concern, given its potential repercussions on public health and the environment. In this work, the potential bio-reduction of the antibiotic amoxicillin (AMX), affected by sorption and desorption, is studied for 17 soils with clearly different characteristics. To carry out these studies, batch-type tests were performed, adding increasing concentrations of AMX (0, 2.5, 5, 10, 20, 30, 40, and 50 μmol L−1) to the soils. For the highest concentration added (50 μmol L−1), the adsorption values for forest soils ranged from 90.97 to 102.54 μmol kg−1 (74.21–82.41% of the amounts of antibiotic added), while the range was 69.96–94.87 μmol kg−1 (68.31–92.56%) for maize soils, and 52.72–85.40 μmol kg−1 (50.96–82.55%) for vineyard soils. When comparing the results for all soils, the highest adsorption corresponded to those more acidic and with high organic matter and non-crystalline minerals contents. The best adjustment to adsorption models corresponded to Freundlich's. AMX desorption was generally <10%; specifically, the maximum was 6.5% in forest soils, and 16.9% in agricultural soils. These results can be considered relevant since they cover agricultural and forest soils with a wide range of pH and organic matter contents, for an antibiotic that, reaching the environment as a contaminant, can pose a potential danger to human and environmental health.