Road de-icing salt: Assessment of a potential new source and pathway of microplastics particles from roads
Roads are estimated to be the largest source of microplastic particles in the environment, through release of particles from tires, road markings and polymer-modified bitumen. These are all released through the wear and tear of tires and the road surface. During the winter in cold climates, the road...
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| Published in: | The Science of the total environment 2020-10, Vol.738, p.139352-139352, Article 139352 |
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| Main Authors: | , , , , , , , |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Roads are estimated to be the largest source of microplastic particles in the environment, through release of particles from tires, road markings and polymer-modified bitumen. These are all released through the wear and tear of tires and the road surface. During the winter in cold climates, the road surface may freeze and cause icing on the roads. To improve traffic safety during winter, road salt is used for de-icing. Knowledge of microplastic (MP) contamination in road salt has, until now, been lacking. This is contrary to the increasing number of studies of microplastics in food-grade salt. The objective of this study was to investigate if road salt could be an additional source of microplastics to the environment. Fourier-Transform Infrared spectroscopy (FT-IR) and Pyrolysis gas chromatography mass spectrometry (GC–MS) were employed to identify and quantify the polymer content in four types of road salts, three sea salts and one rock salt. The particle number of MP in sea salts (range 4–240 MP/kg, mean ± s.d. = 35 ± 60 MP/kg) and rock salt (range 4–192 MP/kg, 424 ± 61 MP/kg, respectively) were similar, whereas, MP mass concentrations were higher in sea salts (range 0.1–7650 μg/kg, 442 ± 1466 μg/kg) than in rock salts (1–1100 μg/kg, 322 ± 481 μg/kg). Black rubber-like particles constituted 96% of the total concentration of microplastics and 86% of all particles in terms of number of particles/kg. Black rubber-like particles appeared to be attributable to wear of conveyer belts used in the salt production. Road salt contribution to MP on state and county roads in Norway was estimated to 0.15 t/year (0.003% of total road MP release), 0.07 t/year in Sweden (0.008%) and 0.03 t/year in Denmark (0.0004–0.0008%) Thus, microplastics in road salt are a negligible source of microplastics from roads compared to other sources.
Illustration of road salt with microplastic particles released onto the roads. Illustrations created using Adobe Illustrator and free vectors from Freepik. [Display omitted]
•Road de-icing salt is potentially a source of microplastic (MP) to the environment•Rubber-like particles constituted 96% of the total concentration of MPs in road salt•Eleven different polymers were confirmed present in road salt•MP release was calculated based on road salt emissions in Norway, Sweden and Denmark•Compared to other sources of MP from roads, contribution from road salt is negligible |
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| ISSN: | 0048-9697 1879-1026 |