Microplastic pollution in surface water and sediments in the urban section of the Vistula River (Poland)

The main hypothesis of this study was that the microplastic (MP) concentration would be higher in the city centre. The MP (<5 mm) abundance and distribution in the urbanized section of the Vistula River were examined. Samples were collected from three different sites: 1) the less urbanized part of the city, 2) the area close to the tributary outlet and wastewater treatment plant (WWTP), and 3) the city centre. The abundance of MPs in water ranged from 1.6 to 2.55 items L-1, whereas in the sediments, it varied from 190 to 580 items kg(-1). The highest MP concentration was observed in the water collected in the city centre. However, in the case of sediments, the most polluted sample was collected from a sampling point located near the WWTP and tributary outlet. The diversity of the MPs abundance along the river was associated with the hydrological and sedimentological conditions, which was confirmed by the grain size analysis of sediments. The dominant type of MPs in both the water and sediment samples was fibre. The MPs were characterized by Raman spectroscopy as polystyrene (PS), polypropylene (PP), and a variety of other materials with different levels of deterioration. The images obtained by scanning electron microscopy (SEM) showed different disintegration features. Moreover, the SEM analyses revealed the occurrence of adhered particles and diatoms on the surface of MPs. The adsorption of various elements onto the MPs surface and the adhered particles was confirmed by energy-dispersive X-ray spectroscopy. The conducted studies emphasized the significance of the impact of large urban agglomerations, such as the Warsaw metropolitan area, on the concentration of MPs in rivers. Further studies are needed to better assess, for instance, the precise mode through which MPs in urban regions are transported by rivers to the seas. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study found that the concentration of microplastics in the urbanized section of the Vistula River was highest in the city center and near the wastewater treatment plant, with different levels of abundance in water and sediment samples. The dominant type of microplastics in both water and sediment samples was fibers, which were characterized as polystyrene, polypropylene, and other materials. Further research is needed to understand the transportation of microplastics in urban regions to the seas.