| With the rapid development of social economy and the increase of energy consumption,the problem of air pollution has become increasingly prominent.People's health has been seriously affected by heavy pollution weather.Comprehensive analysis on the characteristics of air pollutants and typical pollution process in Chengdu in 2016 has been studied in the paper,it is expected that more targeted decision-making basis for the control of atmospheric environment in Chengdu will be provided.Sequential cluster method and wavelet analysis method were used to select four typical pollution processes of air pollutant concentration sequence in Chengdu in 2016 through mutability and periodic analysis,based on the AQI and mass concentration data of PM2.5,PM10,O3,CO,NO2 and SO2 in Chengdu City.All monitoring stations have been classifed based on system clustering method,and the representative receiving points has been selected for research.Combined with meteorological observation,ECWMF reanalysis grid point data set and the GDAS data of NCEP,weather analysis,backward trajectory clustering,potential source contribution founction(PSCF),concentration weight trajectory(CWT)and other methods were used to analyze the pollution and meteorological characteristics of the typical atmospheric pollution process,and to explore the potential source area of the pollutants.The main results are as follows:(1)The time serials of AQI and PM2.5,PM10,O3,CO,NO2 and SO2 mass concentrations in Chengdu in 2016 have been analyzed throuth sequential cluster method and wavelet analysis method,the results showed: From January to April and November to December,concentrations of PM2.5,PM10,CO,NO2 and SO2 were all at a high level,while O3 concentration was low;from May to October,O3 concentration was high,while other pollutants were low.In the 3 research ranges,the hourly variation characteristics of pollutant concentration were different,especially the variation difference between 0:00~7:00 at night and 12:00~18:00 in the afternoon.(2)Combined with the sequence change characteristics of pollution severity and concentration,four pollution processes of December 26 th 2015 to January 6th 2016,4th to 14 th December in 2016,February 28 th to March 6th in 2016,and 1st to 4th April in 2016 were selected as typical examples for research on the characteristics of atmospheric environmental pollution.(3)Through the analysis on the circulation situation during the typical pollution process,the results showed that: From January to April and November to December,when the 700 h Pa southwest air flow on the southeast side of plateau was enhanced(wind speed reached at least 12 m/s),it was not conducive to the increase of nighttime pollutant concentration;there was a closed high pressure system in the ground range of 100~130°E,and the concentration of pollutants in the Sichuan basin was controlled by the east or the north air flow,which was beneficial to the decrease of the concentration of pollutants during the daytime.From March to April,the increasing precipitation weather was good for pollutant removal.The closed high pressure system was conducive to the diffusion of pollutants in the absence of precipitation weather,but at this time,it was easy to form a radiation inversion layer at night,causing pollutants accumulation and concentration increase day by day.(4)The trajectory characteristics during the pollution process were analyzed by backward trajectory clustering method,the results showed: from January to April and November to December,the backward trajectory of the air mass was mainly in the west and northeast,when the trajectories of northeast or Chengdu were affected,the pollutants concentration of receiving point was relatively low,while the trajectories of west was affected,the pollutants concentration of receiving point was relatively high;In March and April,the south or southeastern trajectories increased,but the west and northeast trajectories were still account for more than 50%.When there was no precipitation,the concentration of pollutants was relatively low under the influence of the northeast trajectory,and when there was precipitation,the concentration of pollutants was relatively low under the influence of the southeast trajectory.(5)The analysis of the potential source area of pollutants during the pollution period by PSCF and CWT methods showed that the heavy pollution process during January to April and November to December period,the potential source area of the pollutants was zonal distribution from the northeast to the southwest based on receiving points,and among them,Chengdu,Mianyang,Deyang and Meishan were the main potential source areas.In March and April,the potential source area of pollutants was a crescent shaped or blocky distribution centered on receiving points,and among them,Chengdu,Mianyang,Deyang and Meishan were the main potential source areas. |
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