Microplastics as sorption materials of herbicides, persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in a coastal bay

Environmental plastic pollution is a major issue due to widespread distribution and persistence across air, land, water. Marine plastic pollution primarily stems from land-based human activities via water runoff, rivers, wastewater discharge, though marine activities also contribute. Coastal and estuarine areas are pollution hotspots for plastic debris and a widespread range of anthropogenic contaminants. The present work assess contamination by organic pollutants in the microplastics collected in a coastal ecosystem, the Bay of Brest, France, in comparison with samples of surrounding surface seawater and sediments. Chemical analysis targeted 21 polycyclic aromatic hydrocarbons (PAHs) including the 16 prioritised by the US Environmental Protection Agency, 14 polychlorinated biphenyl congeners (PCBs) including the 7 monitored by the OSPAR Convention and 25 pesticides. Results showed that PAHs concentrations were highest in sediments near industrial and urban zones. PCBs and pesticides were undetectable in surface water while still present in sediments, indicating historical pollution. Floating microplastics carried only six PAHs, the PCB congener 101, and two pesticides. Namely, the herbicides alachlor, banned years ago, and S-metolachlor were quantified exclusively on floating microplastics, suggesting ongoing contamination from land-based sources due to agricultural soils erosion and runoff in the estuary. These findings raise concerns about the role of microplastics as vectors of pollutants reflecting human activities, in this case agricultural. It highlights the need to improve monitoring and mitigation strategies on plastic wastes and associated contaminants in aquatic and soil environments to reduce the risk for bioaccumulation and toxicity in marine ecosystem. • Sediment was the most contaminated matrix providing a record of current and legacy pollution • Floating microplastics contained 6 PAH, PCB congener 101, and 2 pesticides • Alachlor and S-metolachlor were quantified on floating microplastics and not on surrounding water • Data suggest land-based contamination due to soil erosion and runoff to the estuary