Occurrence and in-stream attenuation of wastewater-derived pharmaceuticals in Iberian rivers

摘要

Amultitude of pharmaceuticals enter surface waters via discharges of wastewater treatment plants (WWTPs), andmany raise environmental and health concerns. Chemical fate models predict their concentrations using estimatesof mass loading, dilution and in-stream attenuation. However, current comprehension of the attenuation rates remainsa limiting factor for predictive models.We assessed in-stream attenuation of 75 pharmaceuticals in 4 riversegments, aiming to characterize in-stream attenuation variability among different pharmaceutical compounds,as well as among river segments differing in environmental conditions. Our study revealed that in-streamattenuationwas highly variable among pharmaceuticals and river segments and that none of the considered pharmaceuticalphysicochemical and molecular properties proved to be relevant in determining the mean attenuation rates.Instead, the octanol–water partition coefficient (Kow) influenced the variability of rates among river segments, likelydue to its effect on sorption to sediments and suspended particles, and therefore influencing the balance betweenthe different attenuation mechanisms (biotransformation, photolysis, sorption, and volatilization). The magnitudeof themeasured attenuation rates urges scientists to consider themas important as dilutionwhen aiming to predictconcentrations in freshwater ecosystems