High exposure of ultrafine particles at Guangzhou bus stops and the impact of urban layout

Abstract

Urban bus stops have been identified as hotspots for particulate matter due to intense vehicle activities, including acceleration from standstill, this poses a risk of short-term exposure to high levels of pollution for residents who wait for buses during their daily commute. In order to provide constructive and scientific recommendations for the placement of bus stops from the perspective of regional architectural layout, we conducted a comparative observational experiment in Guangzhou to investigate the exposure to ultrafine particle (UFP) at bus stations with different building layouts. Our study found that there was a significant interaction between the urban layout and vehicle activities of bus stations with 99% confidence level. The average level of UFP pollution at the street canyon bus stations was 48.2 103ptccm−1 in the afternoon. Pedestrians waiting at the bus stations built in the street canyon could be exposed to excessive UFP levels (higher than 30.0103ptccm−1) during 82.2% of the waiting time. Compared to the park, the UFP concentration at the bus station in the canyon was found to be more responsive to changes in traffic volume, and the diffusion of UFP was more dependent on meteorological conditions, according to the results of grey relational analysis. However, near the park, there was no significant difference in UFP levels with and without the bus station. Based on our findings, we recommend that the department of urban planning and design consider creating a more open diffusion environment when setting up bus stops to reduce the risk of exposure to high level of UFP pollution.