Pedestrian exposure to traffic PM on different types of urban roads: A case study of Xi'an, China

To investigate the pedestrian exposure to fine particulate on various typical urban roadways, mass concentration of PM10, PM2.5, PM1 and particle number concentrations in the given size distribution were obtained at four types of urban roads in Xi'an City: urban expressway, arterial road, collector road, and local road. The principal component analysis (PCA) was used. Measurement and analysis results showed that the mean particle number concentration for the size range of 0.25-32 mu m on the urban expressway was 9%, 29% and 32% higher than those on the arterial road, the collector road and the local road, respectively. However, the mass concentration of particles, especially for PM2.5 and PM1, varied little. Traffic volumes on the urban expressway, the collector road and the local road all had important influences on PM particle-number concentration, but at different size ranges. Additionally, the results discussion indicated that PM10, PM2.5 and PM1 were generated from the same emission source(i.e. vehicles) on the urban expressway, yet on the other types of roads PM (especially PM10 and PM1) emissions were generated from different sources (i. e. vehicles, pedestrians, or road dust).