FIELD STUDY OF THE INFLUENCES OF ROADSIDE TREES AND MOVING AUTOMOBILES ON TURBULENT DIFFUSION OF AIR POLLUTANTS AND THERMAL ENVIRONMENT IN URBAN STREET CANYONS

This study aims to investigate and clarify the effects of roadside trees and moving automobiles on outdoor airflow distribution, turbulent diffusion of air pollutants and thermal environment within street canyons by means of the results obtained from field measurements in the central part of Sendai city, Japan. The detailed field measurements were carried out in the summer of 2006, at two streets with different densities of roadside trees and traffic volume. The microclimate and NOX concentrations as well as traffic volume were measured. The effects of the density of roadside trees and the complex interactions of roadside trees were investigated by comparing the results measured at the said two streets. The results clearly showed that thermal environment has been improved but NOX concentration also increased simultaneously.