A method to extract microplastics from river sediments (bed, bank and floodplain)

Identifying and quantifying microplastics in the environment is fundamental to develop effective mitigation strategies. So far, microplastic research has focused on marine environments and large streams. However, smaller rivers, often adjacent to waste sources as agricultural areas and waste water treatment plants, might play an important role in the entry of microplastics into marine habitats. To precisely assess microplastic pollution and to identify sources, it is the aim of our ongoing research to map the Hessian river Lahn, a confluent to the Rhine, in high-resolution. As river sediments can contain more biologic components (like roots) than marine sediments, a somewhat different methodology is required. Here, we present a methodological protocol to detect microplastics in the river bed, river bank and wetlands. The protocol comprises a density separation via MPSS, sieving and filtration steps, detection of microplastics via the fluorescent dye Nile Red and a polymer identification by means of ATR-FTIR spectroscopy. First results of microplastic pollution indicate a function of this confluent river as (possibly temporary) sink for microplastics of terrestrial origin.