[Evolution of the Distribution of PM Concentration in the Yangtze River Economic Belt and Its Influencing Factors].

Intensive social and economic activity has led to serious pollution in the Yangtze River economic belt since 2000. It is urgent to study the evolution of the distribution of PM concentration and its influencing factors in this area, to adopt new ways of development into practice and promote comprehensive regional air pollution prevention and control. Based on PM concentration estimated by remote sensing retrieval, this paper studied the evolution of the distribution of PM concentration in the Yangtze River economic belt from 2000 to 2016, and analyzed spatial non-stationarity of the influence of natural and socio-economic factors on this evolution via a geographically weighted regression model. The results showed that:①The general law of PM concentration presented as higher in the east and lower in the west, with a significant trait of the pollution agglomerations corresponding to urban agglomerations. ②Taking the year 2007 as a divide, annual concentration of PM went through a pattern of annually increasing from 2000 to 2007. and then wavelike decreasing from 2007 to 2016. The annual average concentration increased to 44.1 μg·m in 2007 from the record of 27.2 μg·m in 2000, and then decreased to 33.6 μg·m in 2016. In terms of regions polluted, before 2007, it covered areas including the Yangtze River Delta urban agglomerations, the Yangtze River Middle Reaches urban agglomerations, and the Chengdu-Chongqing urban agglomerations, before quickly stretching to their neighboring areas; after 2007, the extent of areas covered shrank. ③Based on spatial auto-correlation analysis, PM concentration had a significant spatial auto-correlation with hot spots spread over Shanghai, Jiangsu, north-central Anhui, northern Zhejiang, and the central part of Hubei, while cool spots were located in Yunnan, the western and southern parts of Sichuan, and the western part of Guizhou. ④There is a space-time discrepancy by socio-economic and natural factors in the distribution of PM concentration. The socio-economic factors mainly have a positive influence on the concentration, whereas precipitation, one of the natural factors, has a negative influence. The remaining natural factors not only varied in their degree of influence, but also triggered the influence either in a positive or negative manner from time to time and space to space.