| Rapid urbanization,associated with intensified human activities has resulted in many serious ecological and environmental problems,one of which is urban air pollution,particularly in Chinese cities.Fine particulate matter(PM2.5)and ozone(O3)are two major air pollutants in the urban atmosphere with different pollution characteristics.Both of the two air pollutants have significantly negative social,economic and ecological impacts,adversely affect human comfort and health,threatening the resilient and sustainable urban development.To identify and understand the risking regions,driving factors and control effects on typical urban air pollutants are of great importance to the alleviation of air pollution.However,how the concentration of different types of air pollutants changed?How socio-ecological integration affect urban air pollution?And what are the control effects for different types of pollutants are still unclear.In this study,we addressed the questions above using data from air quality monitoring,statistical yearbook,meteorological observation,remote sensing and social media.Focusing on PM2.5 and O3,we took Chinese cities as the study areas.First,regional and seasonal specificities of typical pollution,pollution changes and their synergistic changes with each other in the whole China mainland were revealed and characterized.Second,the driving characteristics and relative contributions of human activities and meteorological conditions and their interaction to PM2.5 and O3 were clarified respectively.And finally,the prevention and control policies for air pollution,and their control effects were assessed taking Shenzhen as case study.The main results and conclusions are as follows:1)The concentration and type of urban air pollutants in Chinese cities had large regional and seasonal variations.Specifically,after the implementation of "Air Pollution Prevention and Control Action Plan" from the year of 2015 to 2017,the pollutio1 of PM2.5 in most cities had been alleviated with 6±9?g/m3 decrease in concentration,and the hotspots were mostly located in the northern China where heavier polluted;while the pollution of O3 were deteriorating,with 8±9?g/m3 increase in concentration,and the hotspots areas were still aggregated in heavily polluted regions.PM2.5 pollution was most severe in winter,while the concentration of O3 was highest in summer at national scale.The synergy of PM2.5 and its precursors(i.e.SO2 and NO2)pollution changes was stong,while the relationship between the change of O3 and its precursors(i.e.NO2)was more complex.2)The driving characteristics of human activities and meteorological conditions on typical pollutants were varied by region and season:2.1)For PM2.5 pollution:the changes of urban spatial structure,socio-economic and meteorological conditions and their interaction all contributed to the variation of PM2.5 pollution;in northern cities,the interaction of socio-economic and meteorological conditions contributed the most to the variation of PM2.5 pollution;while in southern cities,the unique effect of meteorological conditions contributed the most to the variation of PM2.5 pollution.2.2)For O3 pollution:in spring,summer and autumn,there were no significant relationship between O3 pollution and its precursors in most cities,but there were significant negative correlation between O3 concentration and its precursors in most cities in winter;in spring,summer and autumn,O3 pollution in most cities had significant positive correlations to air temperature,but no significant relationships with wind speed;in winter,the relationship between O3 pollution and air temperature became insignificant,but significantly positively correlated to wind speed in most cities;O3 pollution was negatively correlated to relative humidity in most cities in all seasons;meteorological conditions contributed more to the variation of O3 pollution comparing that to its precursors;the unique effect of precursors on O3 pollution were positive in most cities,but became negative when combining to meteorological conditions.3)There are three main directions need to be paid attention for urban typical air pollution control:the reduction of the precursors,the driving characteristics of meteorological conditions and the subjective attitudes of residents.In addition,the implemention of prevention and control policies had varied effects on different types of air pollutants.Specifically,the focus on the rapid upgrading of industrial structure and energy structure,and the implemention of sustained,accurate,timely and specifically control policies,all had played a very significant role in air quality improvement from the persepective of PM,SO2 and NO2 pollution.For the prevention and control of O3 pollution in Shenzhen:on the one hand,different precursors should be regulated according to the relationship between O3 and its precursors in different seasons:in summer and autumn,it may be effectively to reduce the NOx concentration;in spring and winter,attention may need to be paid on the the regulation of VOCs;on the other hand,it is of great importantance to control O3 pollution by mitigating the urban heat in Shenzhen when the precursor concentration was controlled.In addition,in order to better alleviate urban air pollution,the subjective attitude of residents need to be considered through public opinion monitoring. |
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