Plastic waste as a persistent contaminant of our environment is a matter of increasing concern due to the largely unknown long-term effects on biota. Although freshwater systems are known to be the transport paths of plastic debris to the ocean, most research has been focused on marine environments. In recent years, freshwater studies have advanced rapidly, but they rarely address the spatial distribution of plastic debris in the water column. A methodology for measuring microplastic transport at various depths that is applicable to medium and large rivers is needed. We present a new methodology offering the possibility of measuring microplastic transport at different depths of verticals that are distributed within a profile. The net-based device is robust and can be applied at high flow velocities and discharges. Nets with different sizes (41 µm, 250 µm, and 500 µm) are exposed in three different depths of the water column. The methodology was tested in the Austrian Danube River, showing a high heterogeneity of microplastic concentrations within one cross section. Due to turbulent mixing, the different densities of the polymers, aggregation, and the growth of biofilms, plastic transport cannot be limited to the surface layer of a river, and must be examined within the whole water column as for suspended sediments. These results imply that multipoint measurements are required for obtaining the spatial distribution of plastic concentration and are therefore a prerequisite for calculating the passing transport. The analysis of filtration efficiency and side-by-side measurements with different mesh sizes showed that 500 µm nets led to optimal results.
The Vjosa River in Albania represents one of Europe's last free-flowing wild rivers, comprising a mosaic of various habitats and forming a highly dynamic natural ecosystem for flora and fauna, that has largely disappeared from other European rivers outside of Russia. However, due to economic interests, this sensitive and heterogeneous river system is under pressure from potential future use in hydropower, threatening the good hydromorphological and ecological status of the river with reservoir flushing, hydropeaking, colmation, loss of habitats and loss of connectivity. Beside the ecological impacts, this study aims to point out the boundaries for technical and economic issues related to hydropower. Hence, for the first time, sediment transport in the Vjosa River was measured. The results indicate possible consequences of a disturbed sediment regime and loss of capacity caused by the sedimentation of reservoirs. Moreover, subsequent consequences, such as river bed incision downstream of dams as well as progressive coastal erosion, are discussed. By combining data from direct bedload and suspended sediment measurements with long-term hydrological data, an attempt is made to describe the sediment characteristics of the Vjosa catchment and evaluate potential hydropower plants and resulting reservoir sedimentation using limited data. Based on the presented study, it is aimed to define sediment monitoring standards for requested environmental impact assessments and to highlight possible negative impacts of hydropower projects across the entire Balkan region.
lichten die Vulnerabilität der Gesellschaft gegenüber derartigen Ereignissen. Die Gewässergeometrie reagiert bei starken Hochwässern mit massiven morphologischen Umlagerungen. Häuser und Infrastruktureinrichtungen in den betroffenen Gebieten sind somit in Gefahr. Daher ist ein verbessertes Verständnis der Sedimenttransportprozesse zentral für die Analyse der Morphodynamik und damit für das Hochwasserrisikomanagement. Sedimentmonitoring soll ein verbessertes Prozessverständnis bringen, doch beziehen sich bisherige Analysen primär auf die Flussabschnitte, an denen die jeweiligen Daten erhoben wurden. Das Projekt RAISE zielt nun auf die Kombination von Langzeit-mit Kurzzeit-Sedimentforschung (z. B. Extremhochwässer) ab, um diese Daten erstmals in Beziehung zu setzen und integrativ zu diskutieren. Erste Analysen brachten ein verbessertes Prozessverständnis variabler Transportverhältnisse durch die Definition von Geschiebetransport-Prozesstypen. Diese Klassifizierung hilft in der
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