Microplastics result from fragmentation of plastic debris or are released to the environment as pre-production pellets or components of consumer and industrial products. Fragments < 5 mm are ingested by many organisms and are a threat to the aquatic fauna. Microplastics also contain many chemical additives such as antioxidants, processing chemicals, colorants, and pigments and adsorb hydrophobic contaminants from the surroundings. Although as much as 80 % of marine debris originates from land, worldwide, no river has so far been studied for the surface microplastics load over its length.
The North Sea is highly polluted with microplastics, and large rivers such as Thames and Rhine contribute to this pollution. The Rhine, one of the largest European rivers, enters the North Sea through the Rhine-Meuse Delta near Rotterdam, The Netherlands.
Patricia Holm, University of Basel, Switzerland, and colleagues provide a first investigation of floating microplastics particles along the Rhine with respect to the quantity along the 820 km stretch between Basel and Rotterdam and their distribution along and across the river.
Microplastics were found in all samples, with 892,777 particles km−2 on average. In the Rhine-Ruhr metropolitan area, a peak concentration of 3.9 million particles km−2 was measured.
Most frequently, the researchers found mikroplastic in the form of small balls, as well as fragments and fibers. The latter are released, for example, from fleece fabrics. Among the types of plastic, polyethylene, polypropylene, and polystyrene are most strongly represented.