Microplastics and toxic elements in small freshwater lakes and ponds in coastal Norway

This study examined the occurrence of microplastics (MPs) and toxic elements in small freshwater lakes and ponds on islands in the Froan archipelago, Central Norway, evaluating marine plastic as a local contributor to environmental contamination. MP polymers and concentrations, along with toxic elements (As, Cd, Cu, Cr, Hg, Ni, Pb, Zn), were analyzed across freshwater, sediment, marine macroplastics, and adjacent soils across 12 waterbodies on seven islands, using Py-GC/MS (MPs) and ICP-MS (toxic elements). Polyethylene, polypropylene, and polystyrene were the predominant MP polymers, indicating secondary fragmentation. In freshwater, Cd and Zn reached Class V (very bad) status under Environmental Quality Standards, with concentrations up to 4.7 µg L⁻¹ and 260 µg L⁻¹, respectively. Marine macroplastics harbored extreme contaminant burdens from both legacy production additives and environmental adsorption, including Cd up to 415 µg g⁻¹ dw, Pb up to 800 µg g⁻¹ dw, Cr up to 186 µg g⁻¹ dw, and Zn up to 407 µg g⁻¹ dw. There were significant positive correlations for Zn concentrations in plastics, water, and sediments, alongside elevated element levels in shoreline soils (<0.3 m). This strongly indicates that plastic litter acts as a dynamic source and vector transferring toxic elements across compartments, accelerated by acidic conditions (pH < 7) triggering metal desorption. Notably, pollution levels differed greatly, even between ponds on the same island (e.g., a 270-fold difference in water Cd), highlighting the role of local topography on litter retention. These findings underline the role of marine plastic in amplifying contaminant burdens in coastal ecosystems.