Thousands of tonnes of litter are pouring into the North Sea via the Rhine each year, poisoning waters with heavy metals, microplastics and other chemicals, research has found. A study led by the University of Bonn, with help from citizen scientists, revealed that the river carries up to 4,700 tonnes of 'macrolitter' – pieces larger than 25mm – annually.
The litter, which includes tyres containing zinc and other heavy metals, can be detrimental to both the environment and human health. 'Even natural, less persistent materials, such as worked wood, paper, cardboard and food waste may contain toxic or harmful additives,' said Dr Leandra Hamann, a zoologist at the University of Bonn and lead author of the study.
Rivers play a significant role in transporting litter into aquatic and marine environments. Researchers noted that the composition of litter in the Rhine closely resembles that found in other European rivers, including the Thames. The large quantities of litter also risk damaging infrastructure such as drainage systems, increasing flood risks.
Between November 2022 and November 2023, citizen scientists and researchers analysed litter collected from the Rhine using a floating litter trap anchored in Cologne. Out of almost 2,000kg captured, 15% was plastic and 28% was food or drink related. Hamann praised the 'really great work' of citizen scientists, who collected, transported and recorded the litter using a custom app.
The study, published in Communications Sustainability, underscores the need for further research. Hamann noted that while the Rhine is a major contributor of macrolitter to the sea, many other rivers remain uninvestigated.
