Temporal and spatial features of selected wastewater-marking pharmaceuticals and potential mechanisms of their removal from urban rivers.

The investigations on seasonal and spatial distribution of 12 selected wastewater-marking pharmaceuticals (WWMPs) belonging to different therapeutic classes were conducted in three major urban rivers of Yangpu District, Shanghai, East China. The potential mechanisms for the removal of WWMPs in the rivers were also experimentally investigated. The detection frequencies of most WWMPs were in the range of 56-100%, with the exception of clofibric acid, which was not detected during the storm events. The median concentrations ranged from not detected to 5821 ng/L (caffeine) and the maximum concentration was 8662 ng/L, found in caffeine. Part of WWMPs such as paracetamol and caffeine showed significant seasonal variation (P < 0.05), while most of pharmaceuticals displayed limited concentration fluctuation under different seasons for relative low levels. The spatial pattern of most WWMPs has not showed obvious difference in the three rivers (P > 0.05). WWMPs could come from different sources, such as wastewater treatment plants, hospitals, untreated domestic wastewater, or some unknown sources. Lab-scale tests showed that the biodegradation and adsorption were the main removal pathways for WWMPs with lesser contribution from photodegradation and hydrolysis.