Occurrence of micropollutants in surface waters: Monitoring of Portuguese Lima and Douro River estuaries and interconnecting northwest coast

This study monitored the occurrence of 34 MPs in 2 Portuguese estuaries and adjacent coastal area using solid-phase extraction and liquid chromatography-tandem mass spectrometry, covering: (i) an extensive monitoring study area; (ii) a multi-class group of organic MPs, including some outlined in European Union guidelines for water protection; (iii) a year-long monitoring campaign including different seasons; (iv) samples collected at both flood and ebb tide; and (v) samples taken from the water surface and bottom at each sampling point. Results showed that a specific group of compounds prevailed in the monitored areas, with concentrations depending on season, tide, and location. In general, the MPs found more frequently were isoproturon and perfluorooctanesulfonic acid, along with pharmaceuticals trimethoprim, acetaminophen, tramadol, diclofenac, and ketoprofen, which were mostly detected at higher concentrations. Although most MPs have been detected at very low levels, their persistent and widespread presence highlights the need for mitigation measures and effective water treatment solutions able to address them.