Study On Atmospheric PM_2.5Pollution Characteristics Of The Typical "Group" City In Autumn And Winter

In this study,the temporal and spatial differences of PM2 5 pollution characteristics inautumn and winter in Zibo were analyzed.The sources and transport tracks of PM2.5 wereanalyzed by chemical mass balance model,combined with the coefficient of divergence andbackward trajectory method.The results were as follows:(1)The PM2.5 concentration in the heating season(abbreviated as HS)of Zibo wassignificantly higher than that in the non-heating season(abbreviated as NHS).There werespatial differences in the concentration of 5 sites between NHS and HS,which were mainlyrelated to the industrial layout,coal-fired boilers and population distribution density.(2)The foremost water-soluble ion components in PM2.5 were NO3-,SO42-and NH4+,andthere were little differences between the ions at 5 sampling points.The concentrations of mostwater-soluble ions in HS were higher than that of the NHS.In the NHS,the ambient airparticulate matter was nearly neutral,while in the HS,it was weakly alkaline.The degree ofsecondary transformation of NOx and SO2 in NHS at 5 sampling points was slightly higher thanthat in HS.In addition,the concentrations of OC and EC in PM2.5 of 5 sampling sites in HS weresignificantly higher than those in NHS.The foremost elements in PM2 5 in NHS and HS were K,Al,Si,Ca,Fe,Mg and Na,indicating that dust was one of the major sources of PM2.5.(3)The OC/EC ratio analysis indicated that SOC was generated during the sampling time,but POC was the main contribution.The elements of Cu,Zn,As,Cd,Pb,Sn,Sb,T1 and Bi inPM2.5 were mainly influenced by human factors.By using the coefficient of divergence,it could be seen that there were differences in chemical components between 5 sampling points in NHS,while the differences in HS were small.Through CMB analysis,the major sources of PM2.5 inNHS were secondary nitrate,motor vehicle and dust source,while in HS PM2.5 mainly comefrom secondary nitrate,motor vehicle exhaust and secondary sulfate,and there were slightdifferences in the sources of 5 sites.The backward trajectory calculation of Zibo pointed that thepollution sources were mainly local pollution(especially in NHS),but the transmissioninfluences of the Beijing-Tianjin-Hebei region could not be ignored(especially in HS).