The influence of salinity and organic matter on the distribution coefficient (K_d) for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in a brackish water–clay system was studied. The distribution coefficients (K_d) for PFAs onto inorganic clay surfaces increased with salinity, providing evidence for electrostatic interaction for the sorption of PFAs, whereas the relationship between K_d and organic carbon content (f_oc) suggested that hydrophobic interaction is the primary driving force for the sorption of PFAs onto organic matter. The organic carbon normalized adsorption coefficient (K_oc) of PFAs can be slightly overestimated due to the electrostatic interaction within uncoated inorganic surfaces. In addition, the dissolved organic matter released from coated clay particles seemed to solvate PFA molecules in solution, which contributed to a decrease in K_d. A positive relationship between K_d and salinity was apparent, but an empirical relationship for the ‘salting-out’ effect was not evident. The K_d values of PFAs are relatively small compared with those reported for persistent organic pollutants. Thus, sorption may not be a significant route of mass transfer of PFAs from water columns in estuarine environments. However, enhancement of sorption of PFAs to particulate matter at high salinity values could evoke potential risks to benthic organisms in estuarine areas.

The overall ecotoxicological effect of pharmaceutically active compounds (PhACs) detected in the effluents of Korean wastewater treatment plants (WWTPs) to Daphnia magna was investigated using biological and chemical analyses. The bioassay results showed median lethal concentrations and no‐observed‐effect concentrations ranging from a few to tens of ppm levels for nine PhACs in 48‐h acute and 21‐d chronic tests. The mixture effects of pharmaceuticals also were examined by other acute and chronic tests, which showed no significant toxicity despite a slightly increased combined effect of approximately twofold. The residual concentrations of nine PhACs were analyzed at concentrations ranging from 10 ng/L to 89 μg/L in the influents and from 10 ng/L to 11 μg/L in the effluents from four metropolitan cities in South Korea between January and November of 2004. Through repeated investigations of the influents and the effluents from different WWTPs, relatively higher removal efficiencies (23.9–91.3%) compared with those of previous surveys performed in other countries were observed for most pharmaceuticals, with the exception of acetaminophen (8.7%). The present study showed no significant risk effects of the effluents from WWTPs containing pharmaceuticals (i.e., hazard quotient < 1), even at the 95th percentile contamination range, although a risk assessment factor of 1,000 was applied. Therefore, it can be concluded that the potential risk of pharmaceuticals should be monitored carefully with more bioassay data, because many uncertainties still exist in the determination and toxicity of metabolites in water environments. No significant risk was observed, however, from the selected PhACs in the effluents from WWTPs discharged into surface waters.