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

TL;DR

This study examines the presence and behavior of PVC microplastics in the Rhine and Moselle rivers, showing how their levels vary with water flow and pollution sources.

Contribution

The study reveals that PVC microplastic levels are strongly linked to suspended matter and are mainly from diffuse sources, especially during floods.

Findings

PVC microplastic concentrations strongly correlate with suspended matter (correlation >0.94).

PVC pollution is mainly from diffuse sources, with 80% of loads linked to high discharge events like floods.

Annual PVC loads in the Rhine and Moselle ranged from 2–38 t/a, with decreasing trends observed from 2006–2022.

Abstract

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%.

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