Spatial-temporal Characteristics Of PM2.5 Concentration In Chengdu-chongqing Economy Zone Based On Optical Thickness Are Typicl

The Chengdu-Chongqing Economic Zone is the largest dual-nuclear urban agglomeration in western China.Its social and economic development is rapid and its industry is well developed.In addition,the Sichuan Basin is in poor spreading conditions for atmospheric pollutants.Atmospheric problems with PM2.5 as the primary pollution problem have become increasingly prominent.In this paper,the Chengdu-Chongqing Economic Zone is used as the research area.Based on the 2018 MODIS AOD data and PM2.5 surface air quality monitoring time point data,an AOD-PM2.5 concentration regression fitting model is established.The optimal coefficient is selected by determining the coefficient.AOD-PM2.5fitting model is used to estimate the spatial distribution of ground PM2.5 concentration.The spatial and temporal distribution characteristics of AOD and PM2.5 concentrations were comprehensively analyzed using Arcgis spatial analysis and wavelet analysis to screen out typical PM2.5 pollution processes and monitoring points.Combined with meteorological observations and GSAS data from NCEP,analysis methods.Using backward trajectory pattern clustering and potential source analysis to analyze the pollution and meteorological characteristics of typical atmospheric pollution processes,and explore the potential source areas of PM2.5 pollutants.The main research conclusions are as follows:(1)The spatial distribution of AOD in the study area is affected by terrain and season.On the terrain,the AOD in the high altitude area is much lower than that in the belly of the basin,and the AOD value in the low altitude area.During the season,spring and summer,the high AOD concentration of Chengdu-Deyang is obvious,and the high value areas in autumn and winter shift and disperse.In Zigong,Neijiang and other regions,there are high-value areas;the AOD value has a downward trend in time.From the analysis of the 17 and 18 seasons,the AOD value changes in the spring and summer seasons are not obvious;the autumn and winter seasons appear.More obvious reduction.(2)Spatiotemporal distribution characteristics of PM2.5: the occurrence of acircle-like distribution in space.Chengdu-Deyang is the core circle,Ziyang,Neijiang,and Chongqing urban areas are the second circle,and Ya'an,Luzhou,and Southeast Chongqing are the third circle.In different seasons,the spatial distribution of PM2.5 concentration also varies greatly.In terms of time,the changes in PM2.5 concentrations in the prefecture-level cities,districts and counties(municipalities)have a fairly high consistency.The daily average PM2.5 concentration in Chengdu is significantly higher than that in Chongqing.Among them,January and February The PM2.5 concentration is high in December,especially in January.The pollution days are concentrated and continuous.The peak pollution days in Chengdu and Chongqing are close to each other,and some peak days differ by 1-3 days.(3)Combining the degree of pollutant concentration exceeding the standard and the duration of the pollution,two pollution processes from January 11 to 22 and December 15 to21,2018 were selected as typical examples of the characteristics of air pollution in Chengdu-Chongqing Economic Zone.Analysis of the PM2.5 concentration changes during the typical pollution process and the characteristics of the surface meteorological changes found that: the pollution process has obvious peaks,the cumulative time of the peak of the two pollution processes is 4,5 days,the pollution diffusion time is related to the meteorological conditions;the pollution accumulation period The inversion phenomenon is more obvious;in January and December,the movement trajectory of the air mass mainly studies the internal air mass and the external air mass.The external air mass in January mainly comes from Tibet and Qinghai,and the external air mass in December mainly comes from Tibet,Yunnan,and Guizhou.(4)Analysis of potential sources of PM2.5 using methods such as PSCF and CWT:In the pollution process in January,the potential sources of pollution in Chengdu and Chongqing were mainly distributed in the southwest,and pollution from sources outside Chongqing accounted for a relatively high proportion.Qinghai and Yunnan Provinces The local source is mainly the southwestern region of Chongqing,and the main source of Chengdu is western Chongqing,Tongan,Dazu,Sichuan,Chengdu,Deyang,Suining and other places;the pollution process in December,the main source of potential pollution sources in Chengdu and Chongqing in the southeast direction,local source pollution Contributions are high,Chongqing PM2.5 pollution sources are mainly Jiangjin,Neijiang and other places,Chengdu PM2.5 pollution sources are mainly Chengdu,Ziyang.