Spatiotemporal Pattern Of Air Quality And Its Influencing Factors In China

Air pollution has become the major stumbling block for building a beautiful China and realizing the harmonious development of man and nature.Based on air quality data of major cities in China from 2005 to 2016,this paper analyses the temporal and spatial characteristics of air pollution by using the methods of spatial correlation,kernel density,hierarchical clustering method,spatial interpolation and migration of gravity center.Then the effects of temperature,pressure,precipitation,relative humidity and wind speed on air pollution has been discussed.In addition,a spatial econometric model is used to explore the social and economic driving forces of air quality change at both the national level and regional level.The main results are as follows:?1?Air pollution has a remarkable time change rule.In terms of the annual change,air pollution in China has improved obviously in the past 12 years,which mainly manifested in the improvement of heavily polluted cities.But air pollution of clean cities is increasing.From the seasonal change,the country and all regions are dominated by fine and mild pollution weather.The air quality is the best in summer but the poor in winter.SO₂ is the main culprit of air pollution in winter,while O₃ pollution is the dominant factor in summer.Besides,the air quality shows U-type trend on the month level.?2?Air pollution has significant spatial concentration.The spatial clustering analysis results indicate that the national air quality is divided into two major areas in the north and the south by Qinling Mountain-Huaihe River Line,and further subdivided into 11 regions.Among them,three areas of Beijing Tianjin Hebei,Shandong Peninsula and the middle reaches of the Yellow River belong to the long-term high pollution hotspot agglomeration area,while the Yunnan Guizhou Plateau,the west coast of the Straits and southern China belong to the cold spots cluster area with good air quality throughout the year.At the same time,the four haze zones of north China,the Yangtze River Delta,the Pearl River Delta and Sichuan and Chongqing gradually appear.The above studies show that regional air pollution in the country is becoming more and more significant,and it is urgent for all regions to work together to prevent air pollution.?3?Air pollution has significant spatial diversity.The air pollution in the north is heavier than the south,and the air quality in the west presents better than that in the east.Although the air quality of the whole country has been improved in the last 12 years,pollution in Xinjiang and other parts of the nation is aggravated.During the period,the pollution scope has been concentrated from the Middle East to the Beijing Tianjin Hebei region,and the pollution pattern has also changed from centralized distribution to fragmentary distribution.?4?The movement of the center of gravity analysis shows that the gravity center of air quality,PM₁₀ concentration,SO₂ concentration and NO₂ concentration has mainly migrated to the northeast,northeast and northwest respectively over the past 12 years.Which indicate the speed and degree of the pollution of PM₁₀ and SO₂ in the eastern and northern and NO₂ pollution in the west and the north is much higher than other regions of the country.?5?The variation with better air quality appeared in summer while the worse occured in winter is closely related to the seasonal change of temperature.In winter,a large amount of pollutants by heating,less rainfall and inversion weather contribute to the deterioration of air quality.However,the high precipitation and temperature and exuberant convection over the city during the summer help to improve the air quality.The effect of atmospheric pressure on air quality has the double sided.On the one hand,high pressure aggravates air pollution easily.On the other hand,low pressure helps to improve the air quality in the city.There are two critical points in the influence of precipitation and relative humidity on air quality.When rainfall and relative humidity fail to reach the first critical point,the water droplets adsorbed massive air pollutants will aggravate the air pollution.Between the first and the second critical point,the increase of rainfall and relative humidity has a significant effect on the improvement of air pollution.By the time rainfall and relative humidity are over second critical point,their ability to improve air pollution gradually tends to be stable.The influence of wind on air pollution is significant.Although wind is conducive to the transportation and dilution of air pollutants in eastern China,it is also easy to cause sand and dust phenomena in northwest China and promote air pollution.?6?For the whole country,population aggregation,economic and industrial development,energy consumption and vehicle growth have contributed to the deterioration of air quality,while scientific and technological progress and improvement of urban greening have contributed to improving urban air quality.For the region,the effects of social and economic factors on air quality in different stages of development are different.The greening has different effects on air pollution in 11 regions.The increase of population density,energy consumption,the proportion of the second industry and civilian car ownership and the deterioration of atmospheric environment in each region shows a synergistic growth effect.The impact of science and technology expenditure and per capita GDP on the air quality in each region is bi-directional.The progress of science and technology has significantly promoted the air pollution in developed areas.And the order of deteriorating degree of air quality is:the Yangtze River Delta?0.732?>Beijing Tianjin Hebei?0.114?>the upper reaches of Yangtze River?0.066?>the middle reaches of the Yellow River?0.039?>southern China?0.3?>the middle reaches of Yangtze River?0.021?.But in the underdeveloped areas,the progress of science and technology helps to improve air quality.The greater the per capita GDP becomes,the more obvious the improvement of air pollution proves.And the sorting of ameliorative degree of air pollution is:the Yangtze River Delta?0.486?>Beijing Tianjin Hebei?0.399?>Shandong Peninsula?0.117?>southern China?0.101?>the West Bank of the Straits?0.011?.The results of this study provide a scientific basis for revealing the causes of air pollution in China,seeking for pollution control measures,determining key direction of remediation,and making protective policies.