Hydro-sedimentological factors impacting the distribution and abundance of microplastics in fluvial ecosystems
Résumé
Plastic waste management is one of the major challenges of the 21st century with around 80% of the annual worldwide production released into the environment. To date, despite equivalent contamination levels than in marine water bodies, microplastic contamination of freshwater ecosystems remains poorly studied with less than 15% of scientific publications devoted to these ecosystems. In such conditions, hydrological and sedimentary factors controlling microplastic dynamics in streams and rivers have been understudied. Here, we investigated how hydrological exchanges at the water-sediment interface determine the concentrations of microplastics found in riverbed sediment. The concentrations in microplastics were compared between zones with strong surface-groundwater exchanges (strong upwellings or downwellings), and sedimentation zones of the lower Ain River (France). Using a shovel and the Bou-Rouch pumping method, sediments from 15 stations (5 stations per hydro-sedimentary condition) at two different depths (i.e. surface and -20 cm) were sampled. Sediment samples were then sieved with two size meshes (500-5000 μm and 20-500 μm) to analyze large and small microplastic particles. This study showed that hydrological exchanges at the water-sediment determine zones of microplastic accumulation in streams

