An Integrated Field Study of Turbulence and Dispersion Variations in Road Microenvironments.

Abstract

Traffic-related air pollutants (TRAPs) emitted from vehicle tailpipes disperse into nearby microenvironments, posing potential exposure risks. Thus, accurately identifying the emission hotspots of TRAPs is essential for assessing potential exposure risks. We investigated the relationship between turbulent kinetic energy (TKE) and pollutant dispersion (D) through an integrated field measurement. A five-year near-road sampling campaign (5 min based) near a light-duty vehicle-restricted roadway and an on-road sampling campaign (5 s based) on isolated proving grounds were conducted. The D was first calculated based on vehicle emission and pollutant concentrations and then paired with TKE measurements. Here, 198 near-road and 377 on-road measurement pairs were collected. In the near-road measurements, TKE and D showed a positive relationship (R2 ≥ 0.69) with the vehicle flow rate, while they showed similar decay patterns and sensitivity to vehicle types in the on-road measurements. A relationship between TKE and D (TKE-D) was developed through these measurements, demonstrating a robust correlation (R2 ≥ 0.61) and consistent slope values (1.1-1.3). These findings provide field evidence for the positive association between TKE and D, irrespective of the measurement techniques or locations. The TKE-D relationship enables vehicle emission estimation with TKE as the sole input, facilitating the identification of emission hotspots with high spatiotemporal resolution.