Occurrence of toxic metabolites from nonionic surfactants in the Krka River estuary.

The occurrence and behavior of nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), and nonylphenol diethoxylate (NP2EO) were studied in the Krka River estuary. Quantitative determinations using normal-phase high-performance liquid chromatography with spectrofluorimetric detection were performed in both municipal wastewaters and receiving estuarine waters. The concentrations of NP, NP1EO, and NP2EO in municipal wastewaters varied within the ranges of < 0.5-419, < 0.5-35, and < 0.5-54 micrograms/liter, respectively; thus, in general representing only a minor fraction of the total surfactant-derived nonylphenolic compounds. The concentration decrease after the wastewater discharge into the estuary was very sharp, which was assigned primarily to an efficient dilution of the wastewater plume. Consequently, the concentrations of NP, NP1EO, and NP2EO in the estuary were fairly low, the respective concentration ranges being < 20-1200, < 20-440, and < 20-1300 ng/liter. Rather complicated distribution patterns of NP, NP1EO, and NP2EO were obtained on the vertical profile of the estuarine water column with the concentration maxima at the estuarine phase boundaries, i.e., air-freshwater and freshwater-seawater. Moreover, the ratio between individual nonylphenolic compounds varied significantly, indicating that transformation reactions played a significant role in their distribution and fate in the estuary.