Simulation and assessment of traffic pollutant dispersion at an urban signalized intersection using multiple platforms

Abstract

Evaluating the performance of air quality models for roadside traffic exhaust dispersion is critical to sustainable environmental development and urban pollution management. This study introduces three models, namely CAL3QHC, ENVI-met and ANSYS Fluent, to model the pollutant dispersion at an isolated busy urban signalized intersection, by taking fine particulate matter (PM2.5) as the subject matter. A dynamic emission factor model was established based on Cell Transmission Model (CTM) and Portable Emission Measurement System (PEMS) experiment, which was further implemented with the User Defined Function (UDF) of ANSYS Fluent. Results from an empirical study based on the Jianchuan and Humin Road intersection, in suburb Shanghai, demonstrate that ANSYS Fluent performs better for PM2.5 concentration prediction with carefully calibrated parameter settings. Simulation results from both CAL3QHC and ANSYS Fluent are within an acceptable scale, while ENVI-met performs better in assessing the correlation relationships between PM concentrations and the intersectional and meteorological factors. The concentration of PM2.5 was found to increase significantly during the idle phase, which tends to be accumulated in front of the intersection buildings simultaneously. With the increasing of the altitude, the overall average PM2.5 concentration of the intersection decreases gradually. Street canyons with high buildings were found with comparable lower wind speeds, hindering the pollutant diffusion. Finds of this study may assist urban intersection design from a variety of perspectives, e.g., lane channelization, signal timing, and even architecture styles of the surrounding buildings.