Spatial-temporal distribution and pedestrian exposure assessment of size-fractionated particles on crosswalk of urban intersection.

Vehicles tend to produce more pollutants especially particles at an urban intersection than other segments. Meanwhile, pedestrians at an intersection are inevitably exposed to high particle level and suffered from the health problem. Especially, some particles can deposit in different thoracic areas of the respiratory system and cause serious health problems. Hence, in this paper, the particles from 0.3 to 10 μm in 16 channels were measured to compare the spatio-temporal characteristics of them on the crosswalk and the roadside. Based on the roadside of fixed measurements, submicron particles (< 1 μm) are discovered to have a high relation with traffic signal and exhibit a bimodal distribution pattern in the green phase. On the crosswalk of mobile measurements, submicron particles present decreasing trend along the crosswalk while crossing. Additionally, mobile measurements were conducted across six time intervals that correspond to different pedestrian's journey when passing the crosswalk. The results showed that all size particles in the first three journeys present high concentrations than that in other journeys. Furthermore, pedestrian exposure to all 16 channel particles was assessed. The total and regional deposition fractions of these particles in different sizes and age groups are determined. What ought to be paid attention to is that these real-world measurement results contribute to advancing the understanding of pedestrian exposure to size-fractionated particles on crosswalk and assisting the pedestrian to make better informed choice so as to limit particle exposure in these pollution hotspots.