Spatial distribution of the size-fractional PNC and Pedestrian exposure to PM at an urban signalized intersection

Abstract

To evaluate the respiratory health risk of pedestrians at signalized intersections, it is crucial to accurately investigate their spatial distribution of particulate matter (PM) in the air and the respiratory exposure dose to the public. The particle number concentrations (PNCs) of different sizes (10–2500 nm) along the horizontal and vertical vibrations of the intersection were measured in Xi'an, China, and the respiratory deposition dose (RDD) rate of pedestrians was calculated to estimate the pedestrian exposure level. The mean PNC at the intersection's entrance (1.59 × 104 # cm−3) was larger than at its exit (1.34 × 104 # cm−3) irrespective of the particle mode. At the exit, moreover, the PNC values decreased exponentially with increasing distance from the parking baseline of the intersection, while no such damping characterized the entrance to it. Concerning the vertical vibration of the intersection, both nucleation and Aitken modes of PNC peaked at a 0.4-m height and the maximum PNC in the accumulation mode and coarse mode appeared at a height of 3.4–4.5 m. Average RDD rate at the signalized intersection's entrance and exit was respectively 8.103 μg h−1 and 7.523 μg h−1. For this same intersection, the highest PM exposure dose was 8.444 μg h−1 for the elderly, followed by 8.061 μg h−1 for adults, and 3.221 μg h−1 for children.