Pollution Characteristics And Source Apportionment Of PM_2.5 In Nanjing And Its Surrounding Areas

Nowadays,PM2.5 has become a significant index to evaluate air quality,which can affect the climate change directly,harm human health and reduce the visibility.Atmospheric PM2 5 has complex source and different chemical composition.In order to assess the impacts of PM2.5,it's important to evaluate the characteristics and contribution to air quality.The results of this study are expected to play a significant role in data control and support for pollution control measurements.In this study,the samples are collected from Nanjing city and surrounding areas,to understand the difference among those regions and investigate the chemical components of PM2.5.Meanwhile,the samples are pre-treated and then ICP-MS,ion chromatography(ICS-2000,ICS-3000)and OC/EC analyzer are introduced to analysis heavy metals,water soluble ions and carbon fractions of the pollution,and also apply the method of factor analysis(FA)for the PM2.5 source apportionment.According to national index level two in China,PM2.5 concentrations were 50.62?g/m3 in Zhenjiang,the result exceed the standard rate by 16.13%;In Yangzhou,PM2.5 concentrations were 100.44 ?g/m3,over the standard rate by 72.41%and the standard average ratio by 0.34;On Siping Road in Nanjing,PM2.5 concentration average is 85.30?g/m3,which is higher the standard rate by 59.26%and average ratio by 0.14;At chemical industry zone in Nanjing,PM2.5 concentrations were 112.62?g/m3,exceed the standard rate by 90.32%,standard average ratio by 0.50.There was a negative correlation between the average daily mass concentration of PM2.5,as well as visibility and wind speed.And there was a certain correlation between air temperature,humidity and air pressure.The high content of heavy metal elements in the four sampling points are Zn?Pb?Mn,which play as the main part of heavy metals in atmospheric.However,the elements of Ni?Cr?Cd come from industrial pollution and had no significant change due different sampling points.The concentration of As and Cd,which mainly originated from coal combustion,is low and keep consistent characteristics to less coal combustion in northern.NO3?SO42-and NH4+are the main water-soluble ionic components,and the average mass concentration of total concentration of water-soluble ions are,86.17%,81.91%,and 86.23%,respectively.The correlation coefficient of Mg2+ and Ca2+is the largest,followed by group of NH4+and NO3-and group of NH4+and SO42-.Combined with the value of NO3-/SO42-local source pollution is larger than other in Zhenjiang.Meanwhile,the values of mobile source are higher than local source pollution source in other three sampling points.Sea salt has little effect on the content of water soluble ions in atmospheric PM2.5.In addition,the particulate matter in Zhenjiang and Yangzhou is acidic,while the particles on Siping Road and chemical industrial park in Nanjing are alkaline.Fossil fuel burning and biomass combustion are the main emission sources of OC and EC in PM2.5.SOC in the proportion of OC has little difference between winter and summer.The correlation between OC and EC was not obvious.Through factor analysis to four different sampling points,it suggested that the main chemical component comes from secondary aerosols,fossil fuel burning,vehicle emissions,soil dust and industrial emissions and fossil fuel burning,vehicle emissions and industrial emissions are the mainly come from anthropogenic.