Characterization, toxicity and leaching properties of tyre wear particles

, Rozman Ula, Marinšek Marjan, Kalčíková Gabriela.

Tyre wear particles (TWP) are complex material, composed of natural and synthetic polymers, and various additives, like fillers, softeners, vulcanization agents, etc. While driving, shear and friction forces causes abrasion of tyres, and TWP are released into the environment. Smaller TWP are released in the atmosphere, however, most of the particles remain on the roads and due to runoff end up in the soils or freshwaters near the roadside. TWP, used in this study, were obtained from a local car repair service and originated from an old tyre. They were sieved to obtain particles smaller than 300 µm. TWP were characterized using a laser diffraction analyser, optical microscope and field-emission electron microscope. A laser diffraction analyser was used for particle size distribution and the mean value of number particle size distribution was 47.4 ± 22.2 µm. Morphology characterization reviled irregularly shaped particles, with heterogenous surface. The toxicity of TWP and its leachate towards duckweed Lemna minor was determined with the standardized OECD test. The concentration of TWP was 100 mg/L in all tests. Leachate was obtained after 7 days incubation of TWP in duckweed's growth medium. After incubation, TWP were filtered and 10 fronds were added to leachate – the same as with particle testing. The toxicity test lasted 7 days and afterward the specific growth rate of duckweed, root length and chlorophyll content were determined. In comparison with control TWP did not have negative impact on a specific growth rate and chlorophyll content. However, root length was significantly reduced when duckweed was exposed to particles (37 ± 6% compared to control), but not when duckweed was exposed to leachate. Results suggested that TWP have a negative impact on duckweed due to its physical properties (irregular particles with sharp edges) and not due to chemical leaching.

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