Photodegradation of Veterinary Ionophore Antibiotics under UV and Solar Irradiation

• Published in: Environmental science & technology Vol. 48; no. 22; pp. 13188 - 13196
• Main Authors: Sun, Peizhe, Pavlostathis, Spyros G, Huang, Ching-Hua
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.11.2014
• Subjects: animal wastes; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - radiation effects; Antibiotics; Applied sciences; Bacillus subtilis; coccidiostats; Continental surface waters; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; growth promotion; hydroxyl radicals; Ionophores - chemistry; Ionophores - radiation effects; Kinetics; land application; Matrix; Molecules; monensin; Monensin - chemistry; Monensin - radiation effects; narasin; Natural water pollution; nitrates; Nitrates - analysis; nitrogen dioxide; organic matter; Photodegradation; photolysis; Photolysis - radiation effects; Pollution; Pollution, environment geology; Pyrans - chemistry; Pyrans - radiation effects; Quantum Theory; runoff; salinomycin; solar radiation; Spectrum Analysis; surface water; Tandem Mass Spectrometry; toxicity testing; Toxicity Tests; Ultraviolet radiation; Ultraviolet Rays; Veterinary Drugs - chemistry; Veterinary Drugs - radiation effects; Water; Water - chemistry; Water Pollutants, Chemical - analysis; Water treatment and pollution; Emerging contaminant; Toxicity; Ether polymer; Veterinary medicine; Sustainable development; Amendment; Selfpurification; Upgrading; Agricultural waste; Ionophore; Solar radiation; Organic compounds; Photochemical degradation; Drug; Pollutant behavior; Farmyard manure; Biological activity; Waste management; Kinetic model; Antibiotic; Ultraviolet radiation; Surface water; Waste reuse; Water pollution; Resource management; Animal waste
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/es5034525

The veterinary ionophore antibiotics (IPAs) are extensively used as coccidiostats and growth promoters and are released to the environment via land application of animal waste. Due to their propensity to be transported with runoff, IPAs likely end up in surface waters where they are subject to photodegradation. This study is among the first to investigate the photodegradation of three commonly used IPAs, monensin (MON), salinomycin (SAL) and narasin (NAR), under UV and solar irradiation. Results showed that MON was persistent in a deionized (DI) water matrix when exposed to UV and sunlight, whereas SAL and NAR could undergo direct photolysis with a high quantum yield. Water components including nitrate and dissolved organic matter had a great impact on the photodegradation of IPAs. A pseudosteady state kinetic model was successfully applied to predict IPAs’ photodegradation rates in real water matrices. Applying LC/MS/MS, multiple photolytic transformation products of IPAs were observed and their structures were proposed. The direct photolysis of SAL and NAR occurred via cleavage on the ketone moiety and self-sensitized photolysis. With the presence of nitrate, MON was primarily degraded by hydroxyl radicals, whereas SAL showed reactivity toward both hydroxyl and nitrogen-dioxide radicals. Additionally, toxicity tests showed that photodegradation of SAL eliminated its antibiotic properties against Bacillus subtilis.