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A Streamlined Protocol for Comprehensive Anthropogenic Particles and Microplastic Characterization in Canal Sediments: From Concentrations to Environmental Drivers
Summary
Researchers applied a rapid FTIR-based protocol to 61 sediment sites along an 8 km stretch of the Scheldt River in France, finding plastic contamination at nearly all sites with polyethylene films dominating and an estimated 0.1 tonnes of plastic deposited in the riverbed. Efficient, standardized sediment monitoring protocols are essential for building global microplastic budgets and identifying river systems — which transport plastic from land to ocean — that require urgent remediation.
Plastic waste and its fragments, including microplastics (MPs <5 mm), represent a worldwide, long-lasting, and omnipresent hazard to ecosystems. Establishing global budgets for this pollution remains challenging, particularly in river sediments. One significant obstacle is the time-consuming effort required for MP analysis. To address this gap, we tested a simple, robust and rapid protocol on 61 sediments samples, each representing a unique sampling site along a 8 km stretch of the Scheldt River in northern France, focussing on the largest plastic debris fraction (>1 mm). Sediments were sieved at 1 mm to collect large MPs (LMPs; 1-5 mm), mesoplastics (MePs; 5-25 mm), and macroplastics (MaPs; >25 mm), as well as other anthropogenic particles (APs; e.g. glass and metal). Suspected plastics were analyzed using Fourier Transform InfraRed (FTIR) spectrometers. The sediments of the study site are widely contaminated, with plastic concentrations ranging from undetected to 430 items/kg, although the concentrations were relatively homogeneous. APs were largely dominated by LMPs Polyethylene (PE) films (51%). More than 0.1 tons of plastic could be deposited throughout the 8 km of river bed sediments of the sampling site (average width: 60 m; depth: 10 cm; median concentration: 6 mg/kg). The present work reports a slight correlation (Pearson test: R=0.44; p<0.01) between plastics and particulate organic matter (POM) and shows that high plastics concentrations may also be associated with high concentration of polycyclic aromatic hydrocarbons (PAHs) in the sediments of this aquatic system. In conclusion, this study provides a practical protocol for the rapid measurement of large microplastics (>1 mm), which may serve as a useful tool for environmental monitoring and the estimation of preliminary plastic budgets in river systems. While this method offers insights into plastic dynamics within fluvial environments, additional studies are required to determine whether this approach fully represents or at least is linked to the total plastic pollution stock.