Transport processes of microplastic particles in the fluvial environment : erosion, transport and deposition [thesis]

Kryss Lisanne Waldschläger, Holger Schüttrumpf, Henner Hollert
2020
Microplastic enters the environment in different ways and accumulates there due to the persistence of the material. For a long time, microplastic was exclusively considered and studied in the marine environment: From the first environmental studies, to ecotoxicological studies with marine organisms, to hydro-numeric models that were intended to describe the distribution of microplastic in the seas and oceans. However, studies have gradually concluded that most of the microplastic is discharged
more » ... stic is discharged into the oceans by land and therefore by rivers, and the focus has widened to include the fluvial environment. Initially, rivers were considered to be only transport pathways for microplastic from the land-based sources to the open sea. However, it soon became clear that microplastic can also be retained and deposited in rivers and that the concentrations in the fluvial environment are as high asin some hot spots in the marine environment. Due to the limited knowledge about the transport behavior of microplastic in the aquatic environment, the basics of classical sediment transport were simply adapted to the properties of microplastic. However, whether this transfer is appropriate was not examined. The differences between microplastic and classic sediment are undeniable: While sediment has an average density of 2.65 kg/cm³, microplastic can be both lighter and heavier than water, but it is always significantly lighter than natural sediment. Moreover, microplastic has very variable shapes, so it can appear either as pellets or microbeads, but also as fragments, fibers or films. Sediment, on the other hand, consists mainly of granular grains. Finally, the different trends of mean grain diameters along the course of the river are also to be mentioned. While classical sediment is ground smaller and smaller along the course of the river, microplastic is introduced via numerous sources along the course, so that no trend in grain sizes can be formed. Based on these fundamentals, a transferability of the theoretical principles from [...]
doi:10.18154/rwth-2020-12172 fatcat:mpxjlwjuebcf7awhlzwwd34eza