Airborne particulate matter from tire-road friction is a significant atmospheric pollutant with potential environmental impact. Tire wear particles (TWP) are composed of rubber, black carbon, plasticizers, antioxidants, vulcanizing agents, and road dust, ranging in size from nanometers to hundreds of micrometers. Estimated TWP mass fluxes from road traffic vary widely (30 - 117 mg TWP km−1 for passenger cars1) since direct chemical determination of TWP in environmental samples is currently not possible. This raises questions about their environmental fate, including atmospheric transport, transformation, aging, and deposition, which remain inadequately understood.
Targeting organic chemical markers offers a promising approach for identifying and quantifying TWP in environmental matrices indirectly. In our studies, we selected organic components in tires and tested their suitability as analytical markers for TWP detection. We chose markers from four classifications: (1) 1,3-diphenylguanidine (DPG), crucial for tire vulcanization; (2) para-substituted phenylenediamines (PPDs) as antioxidants and antiozonants; (3) PPD-quinones (PPD-qs), derivatives of PPDs; and (4) polycyclic aromatic hydrocarbons (PAHs), which have been previously detected in tire wear. However, their ubiquitous presence in the environment challenges their use as TWP markers.
Herein, we introduce a novel indirect TWP analysis in environmental samples based on standard high-performance liquid chromatography-mass spectrometry (HPLC-MS) and HPLC-fluorescence detection (HPLC-FLD). These techniques allow simultaneous detection and quantification of the specified markers and were employed to: (1) TWP reference materials, to assess the effectiveness of the developed analytical methods and (2) various atmospheric environmental samples.
This project is financed by the Bavarian Ministry of the Environment and Consumer Protection and the DFG– project no. 391977956 – SFB1357.
1Mennekes and Nowack, 2022