Microplastic in fluvial environments - an example of the Elbe river near Dessau-Roßlau, Germany

Accumulation of microplastics (MPs) in aquatic environments is an issue of emerging concern. After research initially focused on marine systems, more and more studies have been published investigating the abundance of MPs in freshwater environments in recent years.The objective of our research is to examine, whether the Mulde river represents an input pathway for MP particles to the Elbe discharge system. Our hypothesis is that the chemical industries located in the catchment area of the Mulde act as a discharge source of primary MPs which are subsequently transported downstream towards the Elbe. Accordingly, there should be more (primary) MPs just downstream of the river mouth, compared to upstream. Therefore, 2 sediment samples and 18 water samples from the Elbe river upstream and downstream the Mulde confluence were taken and analysed on their MP contents.To extract MPs, sample preparation requires various steps including drying, size-fractionation, reduction of organic matter and density separation. The gained fractions are then filtered through glass microfibres paper using a vacuum pump. The dried filters are photographed and examined for MPs under a digital microscope. Representative particles are picked and measured. Finally, we determine their polymer type by pyrolysis or µFTIR.A key result is that both, sediment and water samples, show a substantial increase in primary MPs (especially spheres) just downstream the mouth of the Mulde. Regarding the sampling technique of water samples, we observe differences in the amount and shape of MP particles between filter cascades and filter nets.