CAS Scientists Identify Spatial Distribution and Drivers of Air Pollutants in Urban Street Canyons

Release Time:2023-01-12 Big Small

Urbanization may lead to a series of ecological and environmental problems, such as urban heat island effect, air and water pollution, and water shortage. Studying temporal and spatial diffusion of atmospheric pollutants is an important content of urban ecology and urban planning research, which is of great significance to air pollution preventive and control and thus the health of urban residents.

Dr. Miao Chunping, special research assistant from the Urban Forest Research Group of the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS), Researcher He Xingyuan and Researcher Chen Wei recently conducted a series of studies on atmospheric pollution.

The research team studied the impact of street trees on the concentration of atmospheric particulate matter and found that street trees reduced the concentration of PM10 and total suspended particulates (TSP) near the ground, but only in the tree growing seasons.

The researchers found a strong positive correlation between the concentration of atmospheric particulate matter and the Street Sky Openness. The concentration of particulate matter near the ground surface was the lowest when the angle between a street canyon and the main wind direction was 45°.

The researchers also found that the thermal comfort index (PET) of the middle layer of street canyons was significantly higher than that of the top layer and bottom layer, mainly because of the vertical differences in relative humidity and wind speed. The correlation between PET and air quality was also examined by the researchers. 

In addition, the researchers found that different types of air pollutants in urban street canyons had different vertical distributions patterns. For instance, the concentrations of atmospheric particulate matter and NO2 were higher at the height of 69m than at 1.5m and 27m, while higher concentration of SO2 was observed at 1.5m in height.

The above research results have been published in the papers as shown in the table below.





Seasonal effects of street trees on particulate matter concentration in an urban street canyon


Sustainable Cities and Society


How the morphology of urban street canyons affects suspended particulate matter concentration at the pedestrian level: an in-situ investigation


Sustainable Cities and Society


Does street canyon morphology shape particulate matter reduction capacity by street trees in real urban environments?


Urban Forestry & Urban Greening


Assessing outdoor air quality vertically in an urban street canyon and its response to microclimatic factors


Journal of Environmental Sciences


Vertical evaluation of air quality improvement by urban forest using unmanned aerial vehicles


Frontiers in Ecology and Evolution


Assessing ozone distribution vertically and horizontally in urban street canyons based on field investigation and ENVI-met modelling




Assessing the vertical synergies between outdoor thermal comfort and air quality in an urban street canyon based on field measurements


Building and Environment


Coupling outdoor air quality with thermal comfort in the presence of street trees: a pilot investigation in Shenyang, Northeast China


Journal of Forestry Research




YUE Qian

Institute of Applied Ecology, Chinese Academy of Sciences 

Tel: 86-24-83970317