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Applied Research Impact Case 12

Green Infrastructure and Air Quality for Developing a Smart City

Dr Sissi Chen, Faculty of Design and Environment



Parks are small urban areas in Hong Kong that are important in landscape design. They are also a form of green infrastructure in Hong Kong that can help reduce air and noise pollution and modify the temperature in surrounding environments. By examining how the land within parks are used, researchers can show how green infrastructure is implemented in the city. The ultimate goal for Hong Kong is to become a “Smart City” – a city that provides a core infrastructure to give a greater quality of life to its citizens.


Dr Sissi Chen of the Faculty of Design and Environment investigated the relationship between green infrastructure and air quality by examining the efficiency of different tree species on air quality in Hong Kong’s urban parks, as some species are more effective in improving air quality through gas exchanges than others. Plant surveys were conducted in 15 parks to identify the different species of trees and shrubs within the parks. Field data were also collected at various points within the parks on factors affecting air quality such as temperature, humidity, wind speed, and different levels of particulate matter (PM) i.e. the small particles found in the air. PM level is an important component in identifying the level of air pollution.


A Geographic Information System (GIS) software was used to generate digital layouts of the parks, which illustrated in detail and colour the different tree and shrub species identified within the parks in the form of a digital map. Figure 1 below shows the digital map of Chai Wan Park.


Anna 1

Figure 1. Digital map of Chai Wan Park showing all the tree species


The findings showed that the concentration of PM varied throughout the day. The concentration was lower in the afternoon (see Figure 2), meaning air quality was better. Moreover, parks with more trees showed better air quality than parks dominated by shrubs. This indicated that trees are more efficient than shrubs in improving air quality. The study also showed that certain species of trees or shrubs were more efficient in modifying the park’s temperature and PM concentration, which suggests that certain species should be planted in parks.


Fig 2aFig 2b

Figure 2. Maps showing the average morning and afternoon PM levels in Chai Wan Park


Building a biodiversity database of trees and shrubs in the parks of Hong Kong can benefit multiple stakeholders. The database can inform green infrastructure design to improve the design of parks, guide the selection of plants for parks, and monitor the biodiversity in Hong Kong. More importantly, it can assist in establishing guidelines for policymakers and urban planners for urban renewal. For the public, digital maps can help educate park users about the plants in local parks.


(Acknowledgement: This project was supported by the THEi Seed Grant Scheme, Project No.: SG1819109.)