The role of manure-derived dissolved organic matter in regulating soil antibiotic affinity

Animal manure application may introduce antibiotic residues to the soil along with abundant dissolved organic matter (DOM). In this research, how the pig manure-derived DOM (mDOM) affects antibiotic affinities to acidic upland soils of Lei bamboo plantations under three different management conditions were investigated using batch adsorption-desorption tests combined with fluorescence quenching assays. It was found that the hydrophobic fraction (rich in humic-like substances) of mDOM was preferentially adsorbed by the soils. Different mDOM components exhibited distinct binding preference for antibiotics. The addition of mDOM to the soils increased the adsorption of doxycycline in the two soils with lower OC contents while decreasing that of florfenicol and sulfamethazine in all three soils. These results underscore the necessity of incorporating mDOM effects into evaluations of antibiotic retention capacity in soils that receive manure (slurry) applications or irrigations with animal farm wastewater.