The identification and quantification of tire and road wear particles in Osaka Bay, Japan, by two analytical methods

Tire and road wear particles (TRWP) are generated at the frictional interface between tires and the road surface. This mixture of tire tread and road pavement materials can migrate from roads into nearby water bodies during precipitation events. The absence of mass-based measurements in marine environments introduces uncertainty in environmental risk assessments and fate and transport models. Surface water and sediment samples were collected from nine Osaka Bay (Japan) locations for TRWP mass determination in June 2023. Additionally, sediment traps were deployed for approximately nine weeks at three locations near the mouth of the Yodo River. Large volumes of surface water (approximately 10,000 L/sample) were sequentially filtered (100, 10, 0.5 μm) to capture retained solids between 0.5 μm and 5 mm. Sediment and retained solids were analyzed for TRWP using Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) and the particulate zinc (Zn) method. TRWP concentrations in surface water retained solids and sediment showed spatial variation, with median concentrations of 231 μg/g dw and 312 μg/g (grab samples) and 460 μg/g (trap samples), respectively, with higher concentrations near the mouth of the Yodo River, indicating greater influence from urban areas. The study's findings improve understanding of the Py-GC/MS method, highlighting the necessary adjustments to reduce biases and enhance accuracy, as well as the relationship between Py-GC/MS and the particulate Zn method. These results can inform future environmental risk assessments, fate and transport models, and strategies for mitigating TRWP in marine environments.