Exploring the relationships between urban forms and fine particulate (PM2.5) concentration in China: A multi-perspective study

The rapid urbanization of China related to fine particulate (PM2.5) emissions has attracted global attention, and exploring how urban forms affect PM2.5 concentration has become a hot topic for sustainable development of cites. Here, we combined multisource data and econometric models to quantify the relationships between urban forms and PM2.5 concentration in 250 Chinese cities, with explicit consideration of urban area size, population size, economic structure, and geographical location. The results showed that urban expansion had significant positive impacts on PM2.5 concentration in medium-sized (50–150 km2) and very large-sized cities (>250 km2). Urban form compactness tended to be beneficial for the reduction in PM2.5 concentration in large cities (5 million < population < 10 million). The urban form-PM2.5 concentration relationships were also dominated by economic structure change. That is, urban form irregularity/compactness played an important role in PM2.5 concentration within second cities (the proportion of second industry > 50%) and other cities compared to third cities (the proportion of third industry > 50%). Moreover, a compact and connected urban form was found to be more beneficial for reducing PM2.5 emissions in the northern region than in other regions. This study illustrates that the urban form-PM2.5 concentration relationships are sensitive to the differences in urban types and suggests that flexible urban planning strategies can actually help to reduce PM2.5 concentration in Chinese cities.