Pollution Characteristics Of PM_2.5 And PM₁₀ In Atmosphere And Source Apportionment Of PM_2.5 In Changchun

In order to explore the characteristics of PM_2.5 and PM₁₀ pollution in the atmosphere of Changchun City,this paper studied the temporal and spatial variation characteristics of PM_2.5 and PM₁₀ by using the hourly PM_2.5 and PM₁₀ concentration data of 10 automatic monitoring stations in Changchun City in 2017,and used the correlation analysis method to study the impact of meteorological elements on PM_2.5and PM₁₀ concentration.The backward trajectory and cluster analysis were used to analyze the regional transmission characteristics of particulate matter in Changchun.Meanwhile,PM_2.5 samples from Changchun were collected to analyze the concentrations of inorganic elements,water-soluble ions,organic carbon and elemental carbon.PMF model,enrichment factor method and correlation analysis were used to carry out the source apportionment of PM_2.5 pollution in Changchun.The main conclusions of this paper were as follows:?1?The average annual mass concentration of PM10 and PM2.5 in Changchun basically showed a downward trend.In 2017,the average annual concentration of PM₁₀ was 78?g/m³,and the average annual concentration of PM_2.5 was 46?g/m³.The annual average concentration of PM₁₀ decreased by 39.53%compared with2013,and the annual average concentration of PM_2.5.5 decreased by 36.99%.?2?The time distribution characteristics of PM_2.5 and PM₁₀0 concentration:the seasonal average PM₁₀ concentration was winter>spring>autumn>summer,and the seasonal average PM_2.5 concentration was winter>autumn>spring>summer,which showed the highest concentration in winter and the lowest concentration in summer.Monthly changes of PM_2.5 and PM₁₀ concentrations showed that the maximum value appeared in January,the minimum value appeared in August,and PM_2.5 and PM₁₀concentrations had a peak in October.The diurnal variation of PM2.5 showed a double-peak and double-valley distribution.The maximum occurred at 22:00-23:00,and the minimum occurred at 16:00.The daily change trend of PM10 concentration also showed a double-peak and double-valley pattern.The first peak appeared at06:00-10:00,the second peak appeared at 21:00-23:00,and the minimum appeared at13:00-16:00.?3?The spatial distribution characteristics of PM_2.5 and PM₁₀0 concentration:PM_2.5and PM10 concentrations gradually increased from south to North and increased from east to west.There was a clear boundary of particulate matter between the city?mainly located in the Fourth Ring Road?and the suburbs.The areas with high concentrations were mainly located in the central and western urban areas with dense population and traffic.The average annual concentrations of PM_2.5.5 and PM₁₀ in Institute of Posts and Telecommunications are the highest,54.03?g/m³ and 97.77?g/m³,respectively.The average annual concentrations of PM_2.5 and PM₁₀ in Jingyuetan were the lowest,35.63?g/m³ and 56.42?g/m³,respectively.?4?The concentrations of PM_2.5 and PM₁₀ were negatively correlated with temperature and humidity.PM_2.5 concentration was negatively correlated with wind speed,while PM10 concentration was positively correlated with wind speed.In spring,the concentration of PM₁₀0 was higher in the wind direction of W and WSW.In summer,the concentrations of PM_2.5 and PM₁₀ were higher in SW direction.In autumn,the concentrations of PM_2.5.5 and PM₁₀ were higher in SSE direction.In winter,the concentrations of PM2.5 and PM10 were higher in NNE,NE,ENE and SSE.?5?The backward trajectory clustered results showed that the polluted airflow of PM₁₀ in spring,autumn and winter was the northwest airflow and the polluted airflow in summer was the southwest airflow.The polluted airflow of PM_2.5 in spring and summer was the southwest airflow and the polluted airflow in autumn and winter was the northwest airflow.?6?The total mass of inorganic elements in PM_2.5 in Changchun was 8.13?g/m³,accounting for 14.2%of the mass of PM2.5,and the heavy metals Cu,Pb,Zn and As were highly polluted.The total mass of water-soluble ions was 9.24?g/m³,accounting for 15.1%of the mass of PM_2.5,and the content of SO₄^2-,NO₃^-and NH₄⁺accounted for 69.53%of the total amount of water-soluble ions.The concentration of organic carbon was 14.80?g/m³,and the concentration of elemental carbon was 2.31?g/m³.?7?The results of PM_2.5 source apportionment based on PMF model showed that the contribution rate of coal-fired and industrial sources was the largest,with the contribution rate of 24.7%.Followed by secondary aerosol,soil dust and motor vehicle exhaust,coal and biomass combustion,industrial sources and construction dust,motor vehicle exhaust and metal smelting.Its contribution rates were 18.6%,16.1%,15.8%,10.7%,10.5%and 3.6%.