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Spatiotemporal variations of air pollution index in China’s megacities.

REN Wan-xia1, XUE Bing1**, ZHANG Lin2, MA Zhi-xiao1,3, GENG Yong1   

  1. (1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; 2College of Geography & Environmental Science, Northwest Normal University, Lanzhou 730070, China; 3 University of Chinese Academy of Sciences, Beijing 100049, China)
  • Online:2013-10-10 Published:2013-10-10

Abstract: Urban air pollution has been one of the key environmental problems restricting China’s sustainable development. It is of significance to approach the spatiotemporal patterns of air pollution in megacities for the establishment of regional environmental management policies in China. Taking Beijing, Shanghai, Tianjin, and Chongqing as the study cases, and based on the database of air pollution index (API) from July 2000 to June 2012, a total of 4382 days, this paper analyzed the spatiotemporal variation characteristics and regional differentiation patterns of air quality in China’s megacities. During 2000-2012, the air quality in  Beijing, Shanghai, Tianjin, and Chongqing had been improved gradually, in which, the total days with the air quality over National grades I and II in 2011/12 increased by 60%, 9%, 112%, and 80%, respectively, as compared to those in 2000/01. However, in definite periods of time, there existed the rebound of air pollution, with a higher frequency of serious pollution. The daily average API in the four megacities had a distinct seasonal variation, with the pollution accumulation type of “V”. The PM10 had replaced SO2 into the primary air pollutant, indicating that the air pollution sources in the megacities were more and more complicated. Due to the synchronization trend in the seasonal variation of API among the megacities, urban air pollution had become a regional environmental problem. In the four megacities, the primary period of the daily API variation was around 300 days, and the secondary period was around 150 days. Except that in Chongqing, the API in Beijing, Shanghai, and Tianjin presented the ‘weekend effect’. It was suggested the urban API was dually affected by the natural and human elements.

Key words: compound specific stable isotope., stable isotope, marine ecosystem, baseline