Occurrence and attenuation of pharmaceuticals and their transformation products in rivers impacted by sewage treatment plants

Pharmaceuticals and their transformation products (TPs) have been generally detected in the aquatic environment. They threaten human health and increase environmental risk, but knowledge on their fate and attenuation in environmental ecosystems is still lacking. In this study, 13 parent pharmaceuticals and 8 of their TPs in wastewater containing rivers were investigated. We detected all of the compounds except carboxyibuprofen and sulfacetamide in at least one site in all sampling points and found that sewage treatment plants were the principal source of these substances. The majority of parent pharmaceuticals were attenuated in Yangtze River and Qinhuai River, but only a small number were attenuated in the Yunliang River. All detected TPs except 4-chlorobenzoic acid were attenuated in the three rivers. Photodegradation, sorption to sediments, and biotransformation may be important attenuation processes for these substances. We found the largest extent of attenuation in the Yangtze River, where conditions for attenuation were most favorable. Extents of attenuation values for some substances obtained by active and passive sampling were roughly the same; thus, using a polar organic chemical integrative sampler may be an appropriate method for determining the extent of attenuation of organic micropollutants in rivers.