Fate of pharmaceuticals in the Ebro River Delta region: The combined evaluation of water, sediment, plastic litter, and biomonitoring.

The increasing consumption of pharmaceuticals, alongside their limited removal in wastewater treatment plants (WWTPs), have led to their ubiquitous occurrence in receiving aquatic environments. This study addresses the occurrence of 68 pharmaceuticals (PhACs) in the Ebro River Delta region (NE Spain), as well as their distribution in different environmental compartments, including surface water, sediments, biota (river biofilm and fish tissues), and field-collected plastic litter. In addition, their concentrations in serving WWTPs, as possible sources of environmental contamination, were also determined. Our study confirmed the widespread occurrence of PhACs in riverine and, to a more limited extent, coastal environments. Most frequently detected PhACs belonged to analgesics/anti-inflammatories (e.g., ibuprofen) and psychiatric drugs (e.g., venlafaxine) therapeutic groups, followed by antihypertensives (e.g., valsartan) and antibiotics (e.g., azithromycin). Seasonal differences in cumulative levels of PhACs were reported for water and sediments (winter>summer). Despite spatial gradients were not clear along the river, a non-negligible contribution of upstream Ebro sites (reference area) was highlighted, which was unexpected based on the low anthropogenic pressure. Sediments represented a minor attenuation pathway for the selected PhACs, whereas they were more heavily accumulated in biota: fish liver (up to 166 ng/g dw), river biofilms (up to 108 ng/g dw), fish plasma (up to 63 ng/mL), and fish muscle (up to 31 ng/g dw). These findings highlight the importance of biomonitoring in the characterization of polluted areas and prioritization of hazardous substances (e.g., psychiatric drugs) in aquatic systems, and a particular interest of fish plasma as non-destructive biomonitoring matrix. PhACs were also detected on plastic litter, demonstrating their role as environmental sinks for certain PhACs (e.g., analgesics/anti-inflammatories, psychiatric drugs). Overall, the widespread detection of PhACs in a variety of biotic and abiotic matrices from the lower Ebro River and Delta warns about their possible environmental implications.