Air pollution near arterial roads: An experimental and modelling study

Abstract. Aiming to advance in the understanding of pollutant dispersion near arterial roads, we measured, simultaneously, meteorological parameters, emission mass rates and TSP, PM10 and PM2.5 concentrations at several locations downwind two roads, located on a flat region without any other source of pollutants. We also implemented on a state of the art commercial CFD software, an air quality model to simulate the dispersion of solid and gas-phase pollutants emitted from arterial roads. Numerical results of long-term averages and daily measurements of particle concentration showed high correlation with experimental measurements (R2 > 0.76).

We found that the plots of pollutants concentration vs distance to the road edge describe a unique curve when expressed in terms of non-dimensional numbers and that this curve is well described by a beta function. Profiles of vertical concentration sketch an exponential function at the road edge, an S shape downwind and a flat shape far from the road. Particles exhibit a Rosin Rambler size distribution with average diameter of ~ 7 μm. This distribution remains unaltered downwind from the road, which implies that at any location, PM10 and PM2.5 concentrations are a constant fraction of TPS concentration. Experimental data confirmed this observation.

Previous results can be used to determine the size of the area impacted by roads, identify mitigating and adaptive countermeasures, and to improve the accuracy of vehicular emission factors.