Tuesday, December 15, 2015

How Does Urbanization Affect Urban Air Quality in China?

English: Population density in the People's Re...
English: Population density in the People's Republic of China (Photo credit: Wikipedia)
Estimating the Impact of Urbanization on Air Quality in China Using Spatial Regression Models (23 page pdf, Chuanglin Fang, Haimeng Liu, Guangdong Li , Dongqi Sun and Zhuang Miao, Sustainability, Nov. 20, 2015)

Today we review research into the main characteristics of close to 300 Chinese cities that affect the degree of urban air pollution. Results indicate a close relationship between population density and private cars per unit of developed urban land and that this and the proportion of secondary industry has the greatest effect on the pollution of most cities, especially in the North (in Beijing, Tianjin, Hebei, Henan, and Shandong). The authors recommend that China strictly control the scale of their mega cities and actively develop small and medium sized cities to offset these trends.

Key Quotes:

“Contributing to 1.2 million premature deaths in 2010 and 1.6 million premature deaths in 2014, ambient particulate matter pollution has become the fourth greatest risk factor in all deaths in China, behind only dietary risks, high blood pressure, and smoking…between 2000 and 2010, the economic cost of air quality degradation in China amounted to approximately 6.5% of Chinese GDP annually”

“The permanent urban population in China increased from 17.9% to a staggering 54.77% between 1978 to 2014; ten million people a year migrated from rural areas to China’s large cities during this period,”

“there were, on average, 73 days characterized by “unhealthy” or worse air quality (i.e., AQI > 150) in 70 major cities in 2014, and the dominant pollutants present were PM2.5, PM10, and O3.”

 “we collected air quality index (AQI) records and urbanization indexes for 289 Chinese cities, posing the following research questions…:
  1. What is the spatial pattern of China’s air pollution at the city level?
  2. How can we evaluate the comprehensive influence of urbanization and identify the impact of significant variables on air quality, quantitatively?
  3. To what extent does the spatial contribution made by various urbanization factors account for variations in AQI values? “
“The proportion of urban population thus played a more important role in the North China Plain.” “The spatial pattern of PPC coefficients was similar to those of UR[Demographic urbanization – population %] and the traffic factor was found to have the most important effect on air quality in the Bohai Bay Rim area. Further, both UR and PPC[Private cars per unit of urban development land] had a negative effect on AQI in some southwestern Chinese cities, and this might be related to their limited social and economic development, which is related to the retention of a natural environment that has not been affected by urbanization trends. “
“the population size of cities in the north of China had a greater impact on their AQI values than in the cities of the south. What is interesting is that the spatial distribution of PD[Population density (people/sq km)] coefficients displayed a pattern of longitudinal zonality. The impact of population density on air quality in eastern coastal China was thus found to be lower than that in western cities, although the population density of the eastern cities was in fact higher. "
  “Seriously polluted cities were found to be gathered closely together in Beijing, Tianjin, Hebei, Henan, and Shandong, which presented as hot spots on the visualizations.”

“Among the variables, the population, urbanization rate, automobile density, and the proportion of secondary industry were all found to have had a significant influence over air quality. “

"China must strictly control the scale of megacities and actively develop small and medium-sized cities.”

“Automobile density and the proportion of secondary industry has significant impacts in relation to AQI values: thus, on the one hand, China must promote intelligent traffic management, increase the proportion of green public transport and reasonably controlling the vehicle population in order to reduce emissions from transport; “

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