Field measurement on teermal environment and turbulent diffusion of air pollutants in urban street canyons to investigate the influences of roadside trees and automobiles

This study aims to investigate and clarify the effects of roadside trees and automobiles on airflow distribution, turbulent diffusion of air pollutants and thermal environment within street canyons by means of the field measurements. The detailed field measurements were carried out at two streets with different densities of roadside trees and traffic volume in the central part of Sendai city, Japan. The microcimates and NOx concentrations as well as traffic volume were measured. The effects of roadside trees were investigated by comparing the results measured at the two streets. The results clearly showed that thermal environment has been improved but NOx concentration also increased simultaneously by the roadside trees. The more the number of moving automobiles were, the higher the NOx concentration was at the downstream of the circulating flow within street canyons due to the gas emission from automobiles.