Seasonal changes in ethylene oxide chain length of poly(oxyethylene)alkylphenyl ether nonionic surfactants in three main rivers in Tokyo

Although poly(oxyethylene)alkylphenyl ether (APE) nonionic surfactants with longer ethylene oxide (EO) chain than 2 can be the important pollutants in natural aquatic environments as the potential precursor of alkylphenol, an endocrine disrupting chemical, little attention has been paid to those. Water samples were seasonally collected at five sites of each of the three main rivers in Tokyo. APE with different alkyl chains were separated and fractionated using a reversed-phase adsorption enrichment technique with gradient elution in high performance liquid chromatography (HPLC). After the concentration of each fraction, EO chain length (polymerization degree of EO) in APE was determined by electrospray ionization mass spectrometry (ESI/MS). The results indicated that, in three ma in river waters in Tokyo, poly(oxyethylene)nonylphenyl ether (NPE) was the dominant pollutant among APE, total NPE concentrations with different EO chain lengths were 2-6 nM in summer and 10-35 nM in winter, and its peak in the abundance of NPE components with different EO chain lengths was at 5-8 EO units in winter and shifted to 2-5 units in Summer. Laboratory biodegradation experiments using filtered and NPE-spiked river water confirmed that seasonal changes in the abundance of NPE components with different EO chain lengths would be mainly caused by increased bacterial activity due to high water temperature, producing mainly the persistent nonylphenol diethoxylate.