Nonylphenol ethoxylate (NPEOx) homologs present in commercial mixtures were rapidly adsorbed to and desorbed from native river sediment. Adsorption isotherms, established using high‐performance liquid chromatography analysis to monitor individual homologs NPEO3 to NPEO13 simultaneously, were linear for each component adsorbing to native sediment, organic‐free sediment, and kaolinite, usually with small positive intercepts on the isotherms indicating an additional low‐capacity, high‐affinity binding site. The adsorption partition coefficients (Kd) for the native sediment decreased progressively from 1,460 L/kg for NPEO3 to 450 L/kg for NPEO10, then increased again slightly for higher homologs. In contrast, Kd values for organic‐free sediment (range 230–590 L/kg) or kaolinite (190–490 L/kg) increased steadily from NPEO3 to NPEO13. Adsorptions to silica and alumina were very weak, but to sewage sludge all components adsorbed strongly (Kd values 12,000–33,000, with a maximum at NPEO7). The adsorption to sewage sludge was related to the low‐capacity, high‐affinity sites observed for native sediment. Dependence of Kd values on ethoxylate chain length was analyzed, in terms of both possible adsorption mechanisms, and the environmental fate and impact of NPEOxs as endocrine disruptors.

A strain of Pseudomonas putida isolated from activated sewage grew aerobically on the xenoestrogen precursor, nonylphenol polyethoxylate (NPEO x , where x is the number of ethoxylate units) as sole carbon source. Comparative growth yields on NPEOav6, NPEOav9, and NPEOav20 (mixtures with average ethoxylate numbers as indicated) were consistent with utilization of all but two ethoxylate units, and the final accumulating metabolite was identified by gas chromatography-mass spectroscopy as nonylphenol diethoxylate (NPEO2). There was no growth on nonylphenol or polyethylene glycols, and there was no evidence for production of carboxylic acid analogs of NPEO x . Biodegradation kinetics measured by high-pressure liquid chromatography (HPLC) for each component in NPEO x mixtures showed that biodegradation proceeded via successive exoscission of the ethoxylate chain and not by direct scission between the second and third ethoxylate residues. The NPEO x -degrading activity was inducible by substrate, and cell extracts of NPEOav9-induced cells were also active on the pure alcohol ethoxylate, dodecyl octaethoxylate (AEO8), producing sequentially, under either aerobic or anaerobic conditions, AEO7, AEO6, AEO5, etc., thus demonstrating that the pathway involved removal of single ethoxylate units. HPLC analysis of 2,4-dinitrophenylhydrazone derivatives revealed acetaldehyde (ethanal) as the sole aldehydic product from either NPEOav9 or AEO8 under either aerobic or anaerobic conditions. We propose a mechanism for biotransformation which involves an oxygen-independent hydroxyl shift from the terminal to the penultimate carbon of the terminal ethoxylate unit of NPEO x and dissociation of the resulting hemiacetal to release acetaldehyde and the next-lower homolog, NPEO x−1, which then undergoes further cycles of the same reaction until x = 2.

Abstract-Nonylphenol ethoxylate (NPEO x ) homologs present in commercial mixtures were rapidly adsorbed to and desorbed from native river sediment. Adsorption isotherms, established using high-performance liquid chromatography analysis to monitor individual homologs NPEO 3 to NPEO 13 simultaneously, were linear for each component adsorbing to native sediment, organic-free sediment, and kaolinite, usually with small positive intercepts on the isotherms indicating an additional low-capacity, high-affinity binding site. The adsorption partition coefficients (K d ) for the native sediment decreased progressively from 1,460 L/kg for NPEO 3 to 450 L/kg for NPEO 10 , then increased again slightly for higher homologs. In contrast, K d values for organic-free sediment (range 230-590 L/kg) or kaolinite (190-490 L/kg) increased steadily from NPEO 3 to NPEO 13 . Adsorptions to silica and alumina were very weak, but to sewage sludge all components adsorbed strongly (K d values 12,000-33,000, with a maximum at NPEO 7 ). The adsorption to sewage sludge was related to the low-capacity, high-affinity sites observed for native sediment. Dependence of K d values on ethoxylate chain length was analyzed, in terms of both possible adsorption mechanisms, and the environmental fate and impact of NPEO x s as endocrine disruptors.