Urban Green Space Network—Capturing Air Particulate Matter

Honor Award

Analysis and Planning

Wuhan, China
Wenrui Zhao, Student ASLA; Yincai Yu; Yue Qiu; Xiaoyue Shang; Ming Chen
Faculty Advisor: Fei Dai
Huazhong University of Science and Technology

"This robust, well-documented research project makes a compelling case that urban green space can be an essential component in addressing the global crisis of air pollution, particularly in developing countries. Based on year-long monitoring in rapidly growing Wuhan, China, and subsequent computer modeling, this project lays out in detail and with graphic clarity how a network of green space within cities, including trails, parks, and greenways, can absorb and block the spread of harmful particulate matter. This research deftly highlights the healing power of landscape in communities confronting the deadly effects of environmental degradation."

- 2019 Awards Jury

Project Statement

In May 2019, UNEP published an article entitled 'Air pollution hurts the poorest most', which shows that every year about 7 million people worldwide die from air pollution and most of them come from developing countries, particularly in Asia, Africa and Latin America. Air pollution is a universal problem in many developing countries while airborne particulate matter is the most direct and harmful air pollutant to humans. Through a year-long environmental experiment and computer simulation, we found that the urban green space has the effect of reducing the concentration of airborne particles. Therefore, we try to plan the urban green space network to connect the broken green space of the city, to absorb the air particles and block the diffusion of particles to reduce its concentration, which also has a beneficial effect on urban ecological stability. The method and significance of this plan are not limited to a specific city, but also have reference to countries and cities in Asia, Africa and Latin America that are deeply polluted by airborne particulate matter.

Project Narrative

Urban Green space network—Capturing Air particulate matter

The UN Environment Agency published a survey report in May 2019, which showed that about 7 million people died of air pollution every year, and most of these unfortunate people or areas with serious air pollution are from Asia, Africa, and Latin America. China, but developed countries have also suffered from air pollution during the development process., such as the 1950 London smog incident and the 1943 Los Angeles photochemical smog incident. Air pollution has become a global environmental problem, and the most harmful and direct air pollutant to the human body is the air inhalable particulate matter., referred to as PM10 and PM2.5. It is the invisible killer of the city and is gradually encroaching our healthy life. We try to use the landscape garden approach to cope with the deteriorating air environment, and hope to reduce the airborne particulate concentration in cities through a scientific, implementable urban green space network planning method that can be promoted to the world. This is the vision of our team and the strong desire of countries and cities that are polluted by airborne particulate matter. Fortunately, this seems to be achievable. We chose Wuhan, a city in China as a research and planning site, because it has developed extremely rapidly in the past 30 years. The population of the city has reached 11 million people and the nature of land use and the number of cars have changed drastically, which has caused airborne particulate pollution to be extremely serious.

Experimental research stage:

For decision makers around the world, urban green space can reduce airborne particulate concentrations is unacceptable. And in developed countries and regions that have not experienced air particulate pollution, this is more difficult to be accepted.Therefore, we conducted a year-long environmental monitoring experiment and computer simulation urban scene in Wuhan, analyzed the research results and used powerful conclusions to dispel people's doubts and proved that urban green space has the effect on reducing the concentration of airborne particles.

1. We choose ten circular urban blocks with a diameter of 1000 meters and a significant difference in green coverage. The concentration of airborne particles at the center of the circle is monitored throughout the year. The Correlation software was used to screen and analyze the monitoring data collected in the year. The results confirmed our hypothesis that the green space has the effect on reducing the concentration of airborne particles, For every 10% increase in urban green coverage, the concentration of urban airborne particulate matter can be significantly reduced..

2. Plants also have a barrier effect on the spread of air particles. We analyzed the airborne particulate pollution sources in Wuhan and found that the main source of pollution was automobile exhaust from the streets. Therefore, CFD and ENVI-met software were used to simulate the urban street environment, and found that the trees in the street have the effect on weakening the urban wind and indirectly blocking the diffusion of air particles. There is a positive correlation between the number of trees in the street and its barrier to particulate matter. Therefore, the concentration of airborne particulate matter in urban residential areas is particularly close to the green space of the street.

Planning stage:

It seems impossible to reduce the airborne particulate matter only by large-scale increase in urban green space, because the development status of the city has brought many constraints, such as vacant land shortage, high-density construction environment, and high residents' relocation costs.

Therefore, combined with the status of urban land use, the pattern of green space fragmentation, the portability of the street, and the advantages of networked systems, it is found that connecting the city green space through the green trail is an ideal way to grow the urban green space.

The construction of urban green space network is divided into three levels.

The 1st level——green space network planning in region level

Based on the natural ecological factors such as mountain, forest, water and field in Wuhan and the land acquisition price, the GIS superposition analysis is used to construct the minimum cost path migration of biological migration, and the green corridor connects a large area of urban green space to form a green space network.

The 2nd level——green space network planning in city level

Based on road traffic conditions, greening status, surrounding humanities and attractions, and through GIS overlay analysis, the three elements of green source, green trail and green patch are determined and a green multi-functional network is constructed. In the design of the Green trail, follow the simulation conclusions of ENVI-met and CFD.

The last level——green space network planning in central park of block level

Based on the results of ecological sensitivity analysis based on GIS technology, we have carried out green and blue space network planning for East Lake, and more emphasis is placed on the development of leisure activities for citizens.

Application promotion stage:

Green space network planning is a complex and technical planning project. It reasonably increases the urban green space area in cities with high building density and large population, and actively plays a role in reducing the concentration of urban airborne particles. At the same time, the green space network also has significant gains in maintaining urban ecological stability, increasing ecological diversity, and beautifying the urban human settlement environment. The urban problems faced by developing countries around the world are highly similar, such as urban land scarcity, population concentration, air pollution, etc. The methods and technologies of green space network planning are based on urban common problems, which are generally applicable to other cities. We hope to improve the poor air environment of developing countries and cities through green space network planning, so that air pollution will no longer harm the poor.