Evaluation of emission factors for resuspended tire-wear particles in urban road dust using empirical model-based methods

Abstract

Tire and road wear particles, major contributors to non-exhaust particulate matter emissions, are frequently resuspended into the atmosphere from road dust, posing significant environmental and health challenges. Conventional approaches to estimating emission factors (EFs) often rely on variables such as road dust loading, vehicle types, and road classifications; however, these methods typically neglect the critical influence of wind speed on resuspension dynamics. This study introduces a methodology that incorporates wind speed as a fundamental parameter to improve the accuracy of EF estimations for resuspended tire-wear particles (TWPs). Our approach utilizes particle size analysis, pyrolysis–gas chromatography–mass spectrometry for quantifying TWP content, and a wind-speed depended weighting factor (WF_TWP) that accounts for the resuspension potential of particles. The average TWP content in road dust was determined to be 23,495 mg/kg (2.4 wt%), aligning with findings from previous urban studies. At a near-ground wind speed of 1.5 m/s, resuspended TWPs accounted for 2.6 % of the total resuspended dust mass, closely reflecting the original TWP proportion in road dust. Using modified EPA and Amato methods, calculated EF values ranged from 2.02 to 7.22 mg/vkm, with the Amato method's EF value (3.35 ± 2.21 mg/vkm) comparable to the EPA-derived EF for passenger cars (2.02 ± 0.55 mg/vkm) but showing significant variation for buses (7.22 ± 1.97 mg/vkm). Furthermore, the study found that as wind speed increased, the WF_TWP also increased proportionally, directly impacting EF values. The results indicate the importance of incorporating wind dynamics into EF calculations to more accurately represent real-world resuspension behaviors. This methodology provides a practical tool for estimating the resuspension of TWPs under varying wind conditions and aids in refining emission inventories.