Analysis Of Air Quality Changes In Wuhan Before And After The "closed City"

Air pollution,as one of the most concerned topics,not only profoundly affects the human life,health and safety,which makes people inevitable,but also seriously restricts the rapid development of economy and the continuous improvement of modernization level in China.The public is also highly worried about the hidden dangers to life safety caused by air pollution.The air quality situation has attracted the attention of the whole society.However,how to control air pollution cannot rely on subjective judgments.Only by quantitatively analyzing the air quality and accurately grasping and understanding the changing trend can prescribe the right medicine.The air quality index and pollutant concentration indicators are very important for the quantitative analysis of air quality.This article collects relevant data to analyze the air quality and its changing trends.In 2020,the new crown epidemic occurred.How to help Wuhan which has been hit hard by the epidemic quickly recover has become the top priority for policy makers.Studying various indicators will provide quantitative analysis and theo-retical basis for policy formulation.The air quality data of Wuhan in recent five years were collected by taking Wuhan as the research object and air quality as the research content.The main fields include AQI（Air Quality Index）and the concen-trations of six pollutants such as PM2.5（Fine Particulate Matter）,PM10（Inhalable Particulate Matter）,SO₂（Sulfur Dioxide）,NO₂（Nitrogen Dioxide）,CO（Carbon Monoxide）,O₃（Ozone）.The main empirical methods include visual analysis,cor-relation analysis,multiple regression modeling,and regression discontinuity design.The conclusions are as follows:First,in the visual analysis,except O₃,the concentration of AQI and the re-maining five major pollutants showed a trend of rising in winter and falling in sum-mer.The concentration change of O₃is just the opposite,which shows a trend of high in summer and low in winter.Secondly,through correlation analysis and multiple regression modeling,we discovered that AQI is linear with the concentration of other five pollutants except O₃,and there is no obvious linear relationship with O₃in the modeling process.This paper obtains the different contribution rates of different pollutants to AQI,among which PM2.5 contributes the most to AQI,the regression coefficient is 0.876.Thirdly,through regression discontinuity design,this paper finds that after the closure of Wuhan,the concentrations of AQI and five major pollutants except SO₂have significant changes:AQI,PM2.5,PM10,NO₂,and CO have significantly decreased after the closure.The absolute amount of the decreased concentration is 45.2912,35.5271,59.7121,13.8156,0.2521.The concentration of O₃increased significantly after city closure,and the treatment effect was 11.0197.However,the effect of city closure on SO₂was not significant enough.The above conclusions provide a theoretical basis for Wuhan to adopt corre-sponding policies to control air pollution.Generally speaking,corresponding policies should be formulated according to the monthly and seasonal variation characteris-tics of different pollutants and their different contribution rates to AQI.The control in the post-COVID-19 era should take the change of air quality in Wuhan after the closure of the city as a reference.