How the morphology of urban street canyons affects suspended particulate matter concentration at the pedestrian level: An in-situ investigation

Exposure to near-ground air pollution in urban street canyons poses a serious threat to pedestrian health. To develop design guidelines for air quality improvement, correlations among PM1, PM2.5, PM4, PM10, TSP, street canyons morphology and climatic conditions were investigated by field experimental studies. The results showed that street canyons morphology and air humidity were two of the most important factors affecting suspended particulate matter concentration in urban street canyons. The concentrations of PM1 (9.18 ± 0.17 μg/m3), PM2.5 (18.12 ± 0.43 μg/m3), PM4 (31.66 ± 0.82 μg/m3), PM10 (77.57 ± 2.04 μg/m3) and TSP (104.06 ± 2.85 μg/m3) in deep canyons were significantly lower than those in medium and wide canyons. The pollutants distributed in E-W or N-S street directions were at a lower concentration compared with those in NE-SW or NW-SE street directions. Moreover, the pollutants showed significantly lower concentration in high-rise building areas than in multilayer building areas. This study provides a reference for future urban planning to reduce suspended particulate matter concentration in street environments.