Pollutant dispersion and personal exposure characteristics in tree-lined street canyons with noise barriers

Tree-lined street canyons with noise barriers represent a typical composite street canyon scenario in modern cities. The mutual coupling of four factors, namely, urban wind field, buildings, tree canopies, and noise barrier structures, results in highly stochastic characteristics in the dispersion paths and spatiotemporal distributions of vehicle emissions. This study employs Large Eddy Simulation and a dynamic overset grid method to construct a computational fluid dynamics model that incorporates tree canopies, noise barriers, moving traffic, and street canyon. The model is used to analyze pollutant dispersion mechanisms and resident exposure characteristics within the street canyon. The main findings include: (1) pollutants present higher concentrations on windward building surface than on leeward building. (2) Trees triggers a vortex at windward corner, bringing high-concentration pollutants to windward building surface. (3) The noise barrier restricts the horizontal diffusion of pollutants and decreases the pollutant concentration at the breath zone and near the windward building surface. (4) Trees increase the average personal intake fraction (P_IF) at the breathing zone by 8.69% and increase the value on different floors by 14.38%. The combined effect of trees and the noise barrier reduces the average P_IF at the breathing zone by 30.43% and reduces the value on different floors by 29.41%. This research holds theoretical value and practical relevance for promoting the transformation of modern urban construction toward greener and healthier directions. © 2026 Elsevier Ltd