Tire wear particles concentrations in gully pot sediments

Abstract

While tire wear and tear is known to be a major source of microplastics in the environment, its monitoring is still hampered by the lack of analytical methods able to provide concentrations in environmental matrices. Tire wear particles (TWP) present in road runoff enter the drainage system through gully pots, built to prevent sediment deposition in the drainage system, and eventually protect downstream receiving waters. The aim of this study was to detect and quantify TWP in gully pot sediments, by using a novel method combining Simultaneous Thermal Analysis (STA), Fourier Transform Infrared (FTIR) spectroscopy and Parallel Factor Analysis (PARAFAC). The method was applied to samples from five sites in Southern Norway, characterized by different traffic densities and patterns. The method involved no sample pretreatment, the whole sediment sample was submitted to thermal decomposition in STA, and gases generated during pyrolysis were continuously transferred to FTIR. The FTIR data were arranged in a trilinear multi-way dataset (samples × IR spectra wavenumber × pyrolysis temperature) and then analyzed by PARAFAC. The results showed that TWP concentrations in gully pots varied greatly across sites, ranging from below 1 mg TWP/g sediment in streets with the lowest traffic densities, to 150 mg TWP/g sediment at the most trafficked study site. The results also indicated that other traffic conditions, such as driving patterns influence TWP concentrations. Finally, by enabling quantification of TWP in gully pot sediments, the approach presented here supports environmental monitoring of TWP and safe disposal of gully pot sediments, which is critical for environmental pollution management.

Keywords: FTIR; PARAFAC; Road runoff; Thermogravimetry; Tire wear particles.