Analysis On The Spatial And Temporal Pattern Of PM_2.5 And Its Influencing Factors In The Main Urban Area Of Chongqing

Since the Chinese reform and opening up,the economy has risen rapidly,and the mode of economic growth has been dominated by extensive models at the expense of the environment,causing the deterioration of the quality of the atmospheric environment.On March 17,2018,the first meeting of the 13th National People's Congress held a press conference on the theme of“Doing a good job in tackling pollution prevention and control”in the multi-purpose hall of the Media Center.The Minister of National Environmental Protection Li Ganjie introduced the current country.The status quo of ecological environmental protection work,and mentioned the new three-year plan for air pollution prevention and control,which pointed out that reducing PM_2.5 concentration is one of the important goals.As a kind of air fine particle pollution problem,PM_2.5 has an important impact on human health,atmospheric environment and ecosystem,and it has been more and more widely concerned and studied by society.This paper takes the typical mountain city of southwest China—the main urban area of Chongqing as the research area,and uses multiple regression models,grey correlation models,GIS technology and statistics methods,based on the measured data of the air environment monitoring site issued by Chongqing Environmental Protection Bureau,while considering nature.Factors and socio-economic factors,the time variation characteristics,spatial distribution simulation and influencing factors of PM_2.5mass concentration in the main urban area of Chongqing were studied in detail.The main conclusions obtained are as follows:?1?The PM_2.5 mass concentration in the main urban area of Chongqing has obvious characteristics of time variation.The main performance is that,interannual change:compared with 2016,the average annual PM_2.5 concentration in the main urban area of Chongqing decreased significantly in 2017,with the average concentration of each site decreasing by 13.23%.Seasonal variation:compared with 2016,the average PM_2.5concentration in the main urban areas of Chongqing decreased significantly in the four seasons of 2017.On the seasonal scale,there is a significant seasonal effect,that is,the PM_2.5 pollution is the most serious in winter,the average concentration value is far more than other seasons,the average summer concentration is the lowest,the average concentration in spring and autumn is middle and the average concentration in the two seasons is roughly equal.Monthly change:compared with 2016,except January,November and December,the average PM_2.5 mass concentration in the main urban areas of Chongqing in 2017 decreased significantly.In 2017,the months with low average PM_2.5 concentration are mainly from July to October,and the concentration is about20³0?g/m³.Weekly changes:Longitudinal comparison,the average weekly PM_2.5concentration in 2017 decreased compared with 2016,and the average decline rate in the whole week reached 13.23%.From the horizontal comparison,the PM_2.5 mass concentration change in a week can be roughly divided into four stages:the first stage is a rising trend from Monday to Tuesday.There is no obvious change rule on Wednesday to Thursday in the second stage.The third stage is a downward trend from Wednesday to Thursday.The forth stage is a trend of rising from Thursday to Sunday.In terms of intra-day variation,the average PM_2.5 mass concentration per hour in the main urban area of Chongqing in 2017 decreased by 12.74%compared with that in 2016.Showing the same pattern of change in a day,the daily variation of PM_2.5 concentration in the main urban area of Chongqing from 2016 to 2017 shows the characteristics of double peaks and double valleys,and the corresponding time in double peaks and double valleys is basically the same.?2?Considering the natural and socio-economic factors,the multivariate regression model was used to simulate the spatial distribution of the annual average,seasonal average,monthly average,intra-week average and intra-day average PM_2.5 mass concentration in the main urban area of Chongqing,and found that they have similar spatial distribution characteristics.The main performance is that the concentration of PM_2.5 in the central and western regions with higher economic development level is higher,the concentration of PM_2.5 in the southeastern region with relatively lower economic development level is lower,and the concentration of PM_2.5 in the valley region is higher,and the concentration of PM_2.5 in the"Four Mountains"region is lower.?3?In the analysis of influencing factors,the indicators with medium correlation with PM_2.5 concentration are O₃,highway mileage,crop planting area,population density,the index factors that are highly correlated with PM_2.5 mass concentration are PM₁₀,NO₂,CO,and urbanization rate.The municipal districts with large correlations between atmospheric particulate matter and precursor index layer and PM_2.5 mass concentration are Yuzhong District,Jiangbei District,Yubei District and Dadukou District.The municipal districts with a relatively high comprehensive correlation between pollution source index layer and PM_2.5 mass concentration are Jiangbei District,Shapingba District,Beibei District and Yubei District.The municipal districts with large correlations between urbanization and industrial structure index layers and PM_2.5 mass concentration are Yuzhong District,Beibei District,Shapingba District and Jiulongpo District.