Relationships between 3D urban form and ground-level fine particulate matter at street block level: Evidence from fifteen metropolises in China

Substantial efforts have been devoted to exploring the effects of urban form on fine particulate matter (PM2.5), but the complexity has been far away from being fully understood. The current remarkable inconsistencies with regards to measurements, ascertainment, and findings make the evidence across continents, regions, or cities be necessary to verify the robustness and generalizability of urban form effects. Besides, existing measurements of urban form are often unsystematic and limit analyses in both horizontal and vertical dimensions. In this paper, fifteen metropolises in China were selected to examine the relationships between three-dimensional (3D) urban form and PM2.5 concentrations at the street block level, using 3D spatial metrics and multivariate linear regression. Satellite-derived surface PM2.5 estimates of fine spatial resolution, building footprint, and multiple geographic open datasets were used. Our results demonstrated that urban form effects hold for the metropolises in China, and street accessibility, length of road segments, topography, urban vegetation, surrounding open and green spaces, and transportation facilities were found to be the influential factors of the concentrations of PM2.5. We also revealed the complicated and place-varying effects of urban form indicators, represented by the largely different or opposite effects of many urban form indicators in different cities. For example, building density, building height, and land use mixture have relatively limited and inconsistent effects in most cities. Results of this work suggest critical reflections on some of the current ideas that have been accepted to be vital for improving PM2.5.

Automated summary

This study investigated the relationships between urban form and PM2.5 concentrations in fifteen metropolises in China, revealing that factors such as street accessibility, road length, topography, urban vegetation, surrounding green spaces, and transportation facilities influence the concentrations of PM2.5.