Interaction of Veterinary Antibiotics with Mineral Surfaces and Organo-Mineral Complexes.

Veterinary antibiotics constitute a diverse array of polar and ionogenic organic molecules. Unlike more thoroughly studied nonpolar organic contaminants, mechanisms in addition to hydrophobic partitioning to natural organic matter can contribute importantly to interaction with soil and sediment particles. These mechanisms include cation exchange, cation bridging, surface complexation and hydrogen bonding. The extent and mechanisms of sorption are strongly influenced by antibiotic structure, solution chemistry, and sorbent properties. The structures of some antibiotics allow them to be transformed by mineral phase oxidants (e.g., birnessite, goethite) and extracellular enzymes, and in some cases to become chemically incorporated into natural organic matter. Mechanisms of sorption to mineral surfaces and organo-mineral complexes and transformation by mineral oxidants will be discussed for representatives of several major classes of veterinary antibiotics.