Aerobic Biodegradation Studies of Nonylphenol Ethoxylates in River Water Using Liquid Chromatography−Electrospray Tandem Mass Spectrometry

• Published in: Environmental science & technology 2001-01, Vol.35 (2), p.335-340
• Main Authors: Jonkers, Niels, Knepper, Thomas P, de Voogt, Pim
• Format: Article
• Language: English
• Subjects: Applied sciences; Bacteria, Aerobic - metabolism; Biodegradation; Biodegradation, Environmental; Biological and physicochemical phenomena; Bioreactors; Chromatography; Chromatography, Liquid - methods; Continental surface waters; Decomposition; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Ethylene Glycols - metabolism; Exact sciences and technology; Fresh Water; Ions; Isotopes; Liquid chromatography; Mass spectrometry; Metabolites; Natural water pollution; nonylphenol ethoxylate; nonylphenol ethoxylates; Pollution; Pollution, environment geology; Reaction kinetics; Rivers; Scientific imaging; Spectrometry, Mass, Electrospray Ionization - methods; Water Pollutants, Chemical - metabolism; Water pollution; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es000127o

The aerobic biodegradation of nonylphenol ethoxylates (A9PEO) was kinetically investigated in a laboratory-scale bioreactor filled with river water, spiked at a concentration of 10 mg L-1 nonionic surfactants. Analyses of the samples applying liquid chromatography−electrospray mass spectrometry (LC−ES-MS) after solid-phase enrichment revealed a relatively fast primary degradation of A9PEO with >99% degradation observed after 4 days. Contrary to the generally proposed degradation pathway of EO chain shortening, it could be shown that the initiating step of the degradation is ω-carboxylation of the individual ethoxylate chains:  metabolites with long carboxylated EO chains are identified (A9PEC). Further degradation proceeds gradually into short-chain carboxylated EO with the most abundant species being A9PE2C. The oxidation of the nonyl chain proceeds concomitantly with this degradation, leading to metabolites having both a carboxylated ethoxylate and an alkyl chain of varying lengths (CAPEC). The identity of the CAPEC metabolites was confirmed by the fragmentation pattern obtained with LC−ES-MS/MS. Both A9PEC and CAPEC metabolites are still present in the bioreactor after 31 days. In the aerobic degradation pathway, A9PEO2 is formed only to a minor extent and is even further degraded in several days. The endocrine disruptor nonylphenol was not found as a metabolite in this study.