Concentrations of tire wear microplastics and other traffic-derived non-exhaust particles in the road environment

Ida Järlskog; David Jaramillo-Vogel; Juanita Rausch; Mats Gustafsson; Ann-Margret Strömvall; Yvonne Andersson-Sköld

doi:10.1016/j.envint.2022.107618

Concentrations of tire wear microplastics and other traffic-derived non-exhaust particles in the road environment

Environ Int. 2022 Dec:170:107618. doi: 10.1016/j.envint.2022.107618. Epub 2022 Nov 3.

Authors

Ida Järlskog¹, David Jaramillo-Vogel², Juanita Rausch², Mats Gustafsson³, Ann-Margret Strömvall⁴, Yvonne Andersson-Sköld⁵

Affiliations

¹ Swedish National Road and Transport Research Institute (VTI), SE-581 95 Linköping, Sweden; Geology and Geotechnics, Department of Architecture and Civil Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. Electronic address: ida.jarlskog@vti.se.
² Particle Vision GmbH, Passage du Cardinal 13b, 1700 Fribourg, Switzerland.
³ Swedish National Road and Transport Research Institute (VTI), SE-581 95 Linköping, Sweden.
⁴ Water Environment Technology, Department of Architecture and Civil Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
⁵ Swedish National Road and Transport Research Institute (VTI), SE-581 95 Linköping, Sweden; Geology and Geotechnics, Department of Architecture and Civil Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.

PMID: 36356554
DOI: 10.1016/j.envint.2022.107618

Abstract

Tire wear particles (TWP) are assumed to be one of the major sources of microplastic pollution to the environment. However, many of the previously published studies are based on theoretical estimations rather than field measurements. To increase the knowledge regarding actual environmental concentrations, samples were collected and analyzed from different matrices in a rural highway environment to characterize and quantify TWP and other traffic-derived non-exhaust particles. The sampled matrices included road dust (from kerb and in-between wheeltracks), runoff (water and sediment), and air. In addition, airborne deposition was determined in a transect with increasing distance from the road. Two sieved size fractions (2-20 µm and 20-125 µm) were analyzed by automated Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX) single particle analysis and classified with a machine learning algorithm into the following subclasses: TWP, bitumen wear particles (BiWP), road markings, reflecting glass beads, metals, minerals, and biogenic/organic particles. The relative particle number concentrations (%) showed that the runoff contained the highest proportion of TWP (up to 38 %). The share of TWP in kerb samples tended to be higher than BiWP. However, a seasonal increase of BiWP was observed in coarse (20-125 µm) kerb samples during winter, most likely reflecting studded tire use. The concentration of the particle subclasses within airborne PM_80-1 decreases with increasing distance from the road, evidencing road traffic as the main emission source. The results confirm that road dust and the surrounding environment contain traffic-derived microplastics in both size fractions. The finer fraction (2-20 µm) dominated (by mass, volume, and number) in all sample matrices. These particles have a high potential to be transported in water and air far away from the source and can contribute to the inhalable particle fraction (PM₁₀) in air. This highlights the importance of including also finer particle fractions in future investigations.

Keywords: Bitumen particles; Machine learning; Metal particles; Microplastics; Road markings; SEM/EDX; TRWP.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Microplastics*
Plastics*
Social Environment

Substances

Microplastics
Plastics