| In this study,we collected a wide range of atmospheric particulate pollution sources and ambient PM2.5samples from the urban area of Yan’an,and analysed the chemical composition of water-soluble ions,inorganic elements and carbon components in the samples by chemical analysis and statistical methods.The CMB model was used to analyse the source of PM2.5in Yan’an City.Based on the analysis of atmospheric particulate pollution characteristics,the potential source areas of PM2.5were identified using backward trajectory analysis software（Traj Stat）and the potential source contribution factor（PSCF）method,and the local sources and potential source areas of pollutants in Yan’an were obtained.The main research results are as follows:（1）The order of the mean PM2.5concentrations at each sampling point is:Zao Yuan（30.29～52.10μg/m3,the average value is 42.58μg/m3）<Yan’an University Hospital（47.69～81.09μg/m3,the average value is 59.09μg/m3）<Monitoring station（49.58～76.74μg/m3,the average value is 64.99μg/m3）<Baimi avenue（42.91～96.41μg/m3,the average value is 67.07μg/m3）,the daily average value of PM2.5concentration of samples from three sampling points are higher than the secondary concentration limit（75μg/m3daily average）of the Ambient Air Quality Standard（GB3095-2012）.（2）The pollution characteristics of local PM2.5chemical components were studied.The results show that the concentration of water-soluble ions ranges from 10.12 to45.86μg/m3,with a mean concentration of 25.14μg/m3.The total concentration of water-soluble inorganic ions accounts for 40.81%of PM2.5in Yan’an,with similar results compared to the concentration of water-soluble ions in fine particulate matter in other cities in China.The mean value of the total mass concentration of three secondary inorganic ions,SO42-、NO3-and NH4+,which is the most dominant component of the inorganic ions.The amount of water-soluble ions in fine particulate matter also varies between points:monitoring station（47.55%）>Yandai Medical Hospital（33.65%）>Baimi Avenue（38.21%）>Zao Yuan（27.23%）.（3）Seventeen inorganic elements were detected,and their concentrations were in the order of Ca>Na>Fe>K>Al>Mg>Zn>Mn>Ti>Pb>Cr>Cu>Ni>As>V>Cd>Hg.The mass concentrations of various elements at the Zaoyuan site were lower than those at the other three sites,indicating that this site is a less polluted area for inorganic elements in the Yan’an urban area.The results of enrichment factors show that Mn,Mg,Al,K,V and Ti in PM2.5in Yan’an urban area are influenced by natural sources,Ni,Fe,Na,Ca,As and Cu are influenced by both natural and anthropogenic sources,and Hg,Pb,Zn and Cd are significantly polluted by anthropogenic sources;the results of factor analysis and cluster analysis show that K,Mg,Ca,Al,Ti in PM2.5The results of factor analysis and cluster analysis show that K,Mg,Ca,Al and Ti in PM2.5mainly originate from soil sources and construction dust sources;Hg and As mainly originate from coal combustion emissions;Pb,Cd,V,Cr,Cu,Fe and Co mainly originate from traffic source emissions.（4）Using SPSS software,Pearson correlation coefficients（R=0.650**）were obtained for OC and EC in PM2.5,indicating that the sources of OC and EC are relatively homogeneous,while the sources of OC and EC pollution in PM2.5at the four sampling sites differed.The value of OC/EC>2 in this study is a good homology,and the same high OC/EC results are shown among some primary sources（motor vehicles,combustion,biomass）,which also indicates that combustion sources have a significant impact on PM2.5pollution in Yan’an urban area.（5）PM2.5concentrations in the urban areas of Yan’an are influenced by both local source emissions and regional transmission from non-local sources.Of these,urban dust（20.2%）,secondary sulphate（15.9%）,secondary nitrate（13.6%）and motor vehicle tailpipe dust（15.0%）are the main sources of PM2.5in the Yan’an area.Yan’an urban area in winter 2020 December is mainly affected by the northwest direction and southwest direction air mass transmission.Northwest air masses in the medium and long distance transmission influence the most;northwest direction long distance,northwest direction medium and long distance air masses,southwest direction short distance air masses influence the proportion of 17.4%,26.08%,18.28%respectively.The airflow trajectory from the direction of Xinjiang is longer than other directions,and its movement are faster,bringing less pollutants;northern Shaanxi and other areas are potential source areas of PM2.5pollution in Yan’an urban area. |
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