Effects of vehicle emissions on the PM2.5 dispersion and intake fraction in urban street canyons

Abstract

Vehicle emissions are the primary source of particulate matter 2.5 (PM2.5) emissions, and exposure to traffic-related air pollution can harm human health. The significance of source–exposure relationship study in a street canyon scale is emphasized in this paper. This study predicts and compares the distribution of PM2.5 and its intake fraction (IF) for individual pedestrians, cyclists, and passengers under different traffic volumes and in different road lanes in one street. PM2.5 concentrations decrease with increasing building height. For the same lane and street, the average PM2.5 concentration during the on-peak period for the number of motor vehicles is approximately 2.2–2.5 and 69.5–77.1 times higher than those during the flat peak and low ebb periods, respectively. Moreover, the average PM2.5 concentration at a wind velocity of 1 m/s is approximately 1.6–2.0 and 6.2–9.8 times higher than those at wind velocities of 3 and 6 m/s, respectively, for the same lane and street. Over a 24-h period in Weijin Road–South Gate Avenue, the maximal individual IF of PM2.5 is (6.79 ± 6.96) × 10−10 for adults on the sidewalk during the on-peak period of traffic volume and (4.11 ± 4.25) × 10−10 for children on the sidewalk during the low ebb period of traffic volume. The IFs of PM2.5 for adults are approximately 1.6 times higher than those for children for the same lane and traffic volume. For each ton of PM2.5 emissions from vehicles on the peak, 0.11, 0.33, and 0.68 mg of PM2.5 are inhaled by adults on the motorway, non-motorway, and sidewalk, respectively, in Weijin Road–South Gate Avenue. The corresponding values for children are 0.07, 0.22, and 0.40 mg of PM2.5, respectively. Our application focus on intake fraction a small street scale, which can be of fundamental interest for further research.