Research has shown that thousands of tonnes of rubbish spill into the North Sea via the Rhine every year, polluting the waters with heavy metals, microplastics and other chemicals.
This waste can be harmful to the environment and human health: for example, tires contain zinc and other heavy metals, which in high concentrations can be toxic to ecosystems.
“Even natural, less durable materials such as processed wood, paper, cardboard and food waste can contain toxic or harmful additives,” said Dr Leandra Hamann, a zoologist at the University of Bonn and lead author of the study.
Rivers play an important role in transporting waste to other aquatic and marine environments. Researchers said the composition of the debris found in the Rhine was very similar to debris found in other European rivers, including the Thames. These large quantities of debris can also damage vital infrastructure such as drainage systems, increasing the risk of flooding.
Citizen scientists and researchers from the University of Bonn analyzed trash collected on the Rhine between November 2022 and November 2023. They found that the river carries up to 4,700 tons of “macrotrash”—pieces larger than 25mm—every year. They said more research is needed to understand the full scale of the problem.
Hamann said the Rhine was one of Europe's main sources of macro-trash at sea, but added that many other rivers had not yet been explored.
A floating garbage trap was installed in Cologne to control the amount of garbage passing through the Rhine. Of the nearly 2,000kg caught by the trap, 15% were made of plastic and 28% were food or drink.
Hamann highlighted the “really great work” done by the project's citizen scientists, who were responsible for collecting the debris from the trap, transporting it to the monitoring site and recording individual pieces of debris in a specially designed app.
The study was published in Communications Earth & Environment.
