Types and concentrations of tire wear particles (TWPs) in road dust generated in slow lanes

Drivers commonly navigate their vehicles at moderate speeds in proximity to traffic lights. In this study, road dust samples were collected in the vicinity of traffic lights, as well as at a taxi stand (TS) situated between traffic lights, with considerations given to both forward direction (FD) and backward direction (BD). The characterization of tire wear particles (TWPs) in the road dust was meticulously conducted based on particle size. Notably, tire-road wear particles (TRWPs) were conspicuously absent in samples surpassing 500 μm. Furthermore, TRWPs comprised less than 1% of identified particles in the road dust samples of 212–500 μm, with their origin traceable to heavy vehicles rather than passenger cars. The abundance of TRWPs from heavy vehicles exhibited marked variations, with heightened prevalence in the TS and BD samples as opposed to the FD sample. For the samples smaller than 212 μm, the composition of natural rubber (NR) in TWPs demonstrated a diminishing trend with escalating particle size. Conversely, the composition of styrene-butadiene rubber (SBR) exhibited an upward trajectory independent of the sampling site. The NR composition ratio in TWPs followed the order: TS (17–55%) > FD (17–47%) > BD (13–36%), while the SBR composition ratio exhibited the sequence: BD (62–86%) > FD (48–79%) > TS (24–70%). The TWP concentrations in road dust obtained from the TS (0.35–0.82%) were discernibly lower than those in the FD (0.54–1.77%) and BD (0.61–1.29%) samples. Specifically, the average TWP concentrations in road dust samples, falling within the size range of 20–212 μm, were 0.45%, 1.06%, and 0.91% for the TS, FD, and BD samples, respectively. These concentrations were lower than the corresponding values observed in samples collected from a bus stop.