A Study On The Spatial And Temporal Distribution Of Air Pollution And Source Emissions And Atmospheric Environmental Capacity In Urban Agglomerations Of Sichuan Province

The Sichuan Basin contains most of the urban agglomerations in Sichuan Province.And after Beijing-Tianjin-Hebei,Yangtze River Delta,and Pearl River Delta regions,Sichuan Basin has become the fourth largest polluted area in China.Air pollution prevention and control tasks about Sichuan Province are arduous.Therefore,since the National Air Pollution Prevention Action Plan was released in September 2013,Sichuan Province has strictly implemented it,and air pollutant emissions have been effectively controlled and air quality has been significantly improved.Therefore,this paper adopts the data of various pollutant emission sources from various cities in Sichuan Province from 2013 to 2017,and the mass concentration data of air pollutants from 2015 to 2018,study from two perspectives of air pollutant emission reduction effectiveness and atmospheric environmental capacity.Firstly,a comprehensive analysis of the province's overall air pollution situation and pollutant emission reduction was carried out,focusing on the impact of its air pollutant emission reduction on the corresponding concentration of pollutants in relevant areas,and the change of Chengdu's atmospheric environmental capacity The situation is to provide the necessary scientific and technological support for the future prevention and control of air pollution in Sichuan Province.The main conclusions are as follows:(1)The AQI data of Sichuan Province from 2015 to 2018 shows that the overall air quality in the province has improved significantly.From the perspective of the number of days that the air quality meets the standards,Meishan's compliance rate has increased by 13%,with the largest change in air quality improvement,followed by Neijiang and Chengdu.Judging from the air quality standards in the four areas,they are ranked from poor to good:Chengdu Plain,South Sichuan Economic Zone,Northeast Sichuan,West Sichuan,and Panxi;according to the average AQI index distribution,the AQI distribution in the four study areas is:South Sichuan Economic Zone,Chengdu Plain,Northeast Sichuan,West Sichuan and Panxi.(2)During the study period,there are 71%of Sichuan Province's 21 cities did not meet the standar of the annual average PM_2.5mass concentration valuesds;there are62%of 21 cities did not meet the standards of the annual PM₁₀mass concentration values;only Chengdu did not meet the national standard of annual O₃mass concentrations,Other cities have met the standards;within the province,SO₂,CO and NO₂did not exceed the standards.From a spatial point of view,except for O₃,which has gradually increased in recent years,the mass concentrations of other air pollutants have all significantly decreased;the distribution of PM_2.5,PM₁₀and NO₂is"heavy in the east and light in the west";SO₂and CO are characterized by"heavy in the south and light in the north";the heavily polluted area of O₃tends to shift from the east to the west.From the perspective of seasonal distribution,the seasonal distribution of PM_2.5,PM₁₀,CO,and NO₂during the year from low to high is:summer,autumn,spring,winter;SO₂is autumn,summer,winter,and spring;O₃shows It is"high in summer and low in winter".From the monthly average of the year,the average mass concentration of PM_2.5,PM₁₀,SO₂,NO₂,and CO reached its highest value in December and January,and the high value of CO was in July.(3)The regional ambient air quality comprehensive index in Sichuan Province has changed slightly from 2015 to 2018.The pollution situation in 2016 has been worse than that in 2015,and the air quality comprehensive index has improved significantly from 2016 to 2018.During the study period,PM_2.5,PM₁₀and O₃played a major role in pollution load.Among them,before 2017 PM_2.5was the primary air pollutant;in 2018,the O₃load coefficient was the largest and was the primary air pollutant;the pollution load of PM_2.5,PM₁₀,SO₂and CO decreased year by year,and the NO₂and O₃pollution load increased year by year.(4)The statistical analysis of the emissions of six types of air pollutants from 2013to 2017 shows:the Chengdu Plain has the highest contribution rate of air pollutant emissions,followed by the Northeast Plain,and the least in Panxi and West Sichuan.By comparing the total emissions of air pollutants,we can know that residential sources are the largest source of CO,mobile sources are the largest source of NO_x,solvent use has the largest contribution to VOC_Semissions,industrial sources are the largest source of SO₂,dust sources and agricultural sources contribute to particulate matter Contaminants have a big impact.During the emission reduction period,the ultra-low emission transformation of coal-fired power plants has the largest contribution to CO emission reduction,and it is also the largest contributor to NO_xemission reduction;the special rectification of VOC_Shas the greatest impact on VOC_Semission reduction;coal-fired boiler rectification has the most significant impact on SO₂emission reduction,accounting for 57%;the main contribution rate of particulate emission reduction comes from other key industry upgrades.(5)The correlation analysis of the reduction of the six kinds of atmospheric pollutants and the reduction of the corresponding mass concentration shows that:the correlation coefficient between PM₁₀emission reductions and air pollutant mass concentration differences is the largest,indicating that the environmental improvement generated by its emission reduction is sensitive,and it has the highest sensitivity;through correlation studies on the reduction of emissions in different months of the year and the reduction of the mass concentration of air pollutants,we can know that January is the emission reduction month with the highest sensitivity to environmental improvement of NO_x,PM_2.5and PM₁₀,then April and May respectively express it is the emission reduction month with the highest sensitivity to VOC_Sand CO environment improvement,and September is the emission reduction month with the highest sensitivity to SO₂environment improvement.(6)According to the research on the characteristics of the interannual and seasonal changes of the atmospheric environmental capacity of SO₂,NO₂,PM_2.5,and PM₁₀in Chengdu,the capital city of Sichuan Province,2015-2018,and their composition changes,we can know that from 2015 to 2017 the annual atmospheric environmental capacity did not change significantly,but in 2018 the annual atmospheric environmental capacity is increase obviously;in terms of seasonal changes,there are obvious"step-like"characteristics:the average values in spring and summer are higher,and the autumn and winter are lower;the atmospheric environmental capacity of the four types of air pollutants reached their maximum in May,and December and January were the lowest monthly averages during the year;in terms of its composition,wet deposition is the main method of removing various air pollutants,followed by the basic atmospheric environmental capacity term,and the dry deposition amount term and chemical conversion term account for a small proportion in the atmospheric environmental capacity.By studying the correlation between the atmospheric environmental capacity and the corresponding mass concentration of atmospheric pollutants,there is a significant negative correlation between the two.Among them,the negative correlation between the atmospheric environmental capacity of SO₂and the mass concentration is significant;but the negative correlation of NO₂,PM_2.5and PM₁₀are very significant.Therefore,it is feasible to use the atmospheric environmental capacity as an indicator of atmospheric pollution.Among the four atmospheric environmental capacity removal items,the wet removal item has the best correlation with the corresponding air pollutant mass concentration,indicating that precipitation has the most significant removal effect on atmospheric pollutants,this also reflects the environmental purification effect of"Bashan Night Rain".