Sources and fate of nonylphenol ethoxylates and their metabolites in the Dutch coastal zone of the North Sea

Results are presented of a field study in the Dutch coastal zone of the North Sea on the environmental fate of nonylphenol ethoxylates (A9PEO). The goal of this field study was to determine the sources of these nonionic surfactants to the Dutch coastal zone, and their subsequent fate. Surface waters, sediments and suspended particulate matter were analyzed on A9PEO, nonylphenol (NP) and the carboxylated metabolites (A9PEC), using Soxhlet extraction, Solid Phase Extraction and liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS). Unusually high dissolved concentrations of A9PEO were observed in a number of offshore samples. Maximum dissolved concentrations of 36, 1.7 and 0.63 μg L−1 were observed, respectively, for A9PEO, NP and A9PEC. Dissolved concentrations of A9PEO at the water surface were roughly one order of magnitude higher than several meters below the surface. More than 25% of the A9PEO present in marine water is sorbed to suspended particulate matter. In sediments, maximum concentrations of 277 and 86 ng g−1 for A9PEO and NP were observed, whereas A9PEC were only found sporadically. Relatively high concentrations of A9PEO and NP were observed in sediments near the shore, which decreased until below 50 ng g−1 d.w. at about 10 km off shore. In the sediments, mainly the short chain A9PEO1–3 are detected, indicating that extensive biodegradation has occurred. Both the oxidative and non-oxidative hydrolytic biodegradation mechanisms occur in the Dutch coastal zone, although the oxidative route is less important than in the adjacent Scheldt and Rhine estuaries. The main sources of A9PEO in sediments in the Dutch coastal zone were identified as the Rhine and Scheldt estuaries, dump sites for harbour dredge and in some cases production platforms. For the water phase, the most likely sources of A9PEO seem to be discharges from ships at open sea.