From the river to the sea: Microplastics in water and sediments of the Elbe and Thames rivers and the North Sea

Microplastics have been investigated for over 45 years especially in the marine environment, but only in the past years research has started to focus on freshwater environments. In the frame of the H2020 LABPLAS project, different compartments in the Elbe and Thames river basins and the North Sea were studied in order to better understand the sources, transport, distribution and impacts of plastic pollution and to detect the amount of plastics transport via the rivers into the sea. In the frame of the project, a winter and a summer campaign were conducted 2022 and samples taken from 6 sites within each river basin and from 4 sites from the North Sea between the Elbe and Thames estuaries. Samples collected were floating macroplastics, surface microlayer samples (Garrett screen), water samples (10-1000 µm with a pump and stainless-steel filters; >335 µm using a manta net) and sediments (with a Van-Veen-grabber). Density separation and organic digestion took place and analysis was done with a hyperspectral camera, FTIR and LDIR. The preliminary show that microplastics are present in all samples. The number of particles varies significantly between the compartments, sampling sites and the seasons showing the complexity of plastic sampling and analysis. In the sediments (>10 µm), considerably more microplastics were counted than in the water. Higher values were observed close to cities and the Elbe estuary, in the North Sea close to the Thames estuary. In general, more microplastics are present in manta nets (>335 µm) of the tidal part of the rivers than in the freshwater part. The contrary occurs for small microplastics (10-1000 µm). Only few macroplastics were found. Most common polymers were PP, Acrylates/PU/Varnish, PS and PE as well as PTFE and rubber.