Occurrence, Temporal Variability, and Loads of Poly(vinyl chloride) in the Rhine and Moselle

There is an urgent need to improve the knowledge about occurrence and behavior of microplastics in the aquatic environment. The aim of this study was to determine the temporal variability and spatial distribution of poly(vinyl chloride) (PVC) in the larger German rivers Rhine and Moselle. Monitoring campaigns using a continuous flow centrifuge (sampling of suspended matter in a particle size range of 1 mm-1 μm) revealed a strong dependence of PVC concentrations of up to 3.3 μg/L on the discharge. It could be shown that PVC microplastic concentrations have strong correlations with suspended matter (correlation coefficients >0.94 with p-values <0.05). PVC microplastics and suspended matter were thus evidenced to show an identical temporal behavior in the Rhine River and Moselle. Furthermore, our results indicate that the pollution with PVC microplastic is mainly originated from diffuse rather than point sources. Elevated PVC loads were mainly observed during floods. Our study confirmed that approximately 80% of the PVC loads can be exclusively attributed to these high discharge events. Calculated annual PVC loads (2019-2022) ranged from 2-17 t/a (Moselle) to 10-38 t/a (Rhine). In addition, long-term trend analysis of loads (2006-2022; particle size range: <2 mm) at the Rhine for Weil, Iffezheim, Koblenz, and Bimmen showed significant decreasing trends (ranging from 0.41 to 1.72 t/a) for all these sites with an overall decrease ranging between 38 and 58%.