Comparison of PM spatiotemporal variations and exposure at adjacent signalized intersection and roundabout

Abstract

As urban traffic nodes, signalized intersections and roundabouts gather a large number of vehicles, forming traffic particulate matter (PM) hotspots. However, related studies have focused only on signalized intersections, and knowledge of PM characteristics on roundabouts are still scarce. For this reason, we carried out mobile and fixed-site monitoring of PM mass and number concentrations and comparative analysis, at an adjacent roundabout and intersection. The attenuation curves of PM2.5 concentrations down the departure roads from the roundabout and intersection centers showed an exponential decay, but their distribution profiles were obviously different. Particle number concentration (PNC) first increased and then decreased at the roundabout, while it was similar to PM2.5 with exponential decay at the intersection. The temporal variation of PNC in different particle sizes differed between the roundabout and intersection. A Generalized Additive Model (GAM) quantified the contribution of background concentration, Meteorological conditions, and traffic volume to PM2.5 at the roundabout and the intersection, respectively, identifying their different influential levels. Lastly, using field data of this case study, the average respiratory deposition dose (RDD) rates were estimated for adults and children. The study can help formulate effective urban traffic pollution control strategies.