Chemical Characteristics And Source Apportionment Of PM_2.5in Xiamen,China

According to the report from Ministry of Environmental Protection of China(www.zhb.gov.cn),PM2.5 is the primary pollutant in most Chinese cities,many researchers pay attention to it.In order to probe the temporal and spatial characteristics as well as source apportionment of PM2.5 at different sites in Xiamen,ambient PM2.5 samples from selected sites,SM(Siming campus of Xiamen University)and XA(Xiang'an campus of Xiamen University)in Xiamen from 2015.11 to 2017.10 were chemically analyzed.Source apportionment analysis was conducted on this dataset using the factor analysis(FA)method and PMF(Positive Matrix Factorization)model to compare the differences at SM and XA.The conclusions are following:1.The annual average of PM2.5 in Siming campus of Xiamen university ocean building(SM)and Xiang'an campus of Xiamen university student activity center(XA)is 39.40 ?g/m3,38.41 ?g/m3,respectively,exceeding 35 mg/m3,the limit ceiling of average annual concentration of PM2.5 regulated in the Chinese National Ambient Air Quality Standards(GB3095-2012).The mass concentration of PM2.5 in Xiamen is mainly affected by local sources.The seasonal variation trend of SM and XA show that winter and spring are significantly higher than summer and autumn,which is mainly related to the meteorological conditions and emission intensity of local sources.2.Water-soluble ions are the main components of PM2.5 in Xiamen,and the characteristics of multi-source pollution in winter and spring season is more serious.Different concentration of water soluble ions between SM and XA are mainly affected by the precipitation.3.The V of PM2.5 at SM and XA comes from different sources,and XA is more vulnerable to dust pollution.The increase of human activitise and the throughput of the port in the summer lead to the high level of Ni and V at SM.In addition,the influence of the exhaust emissions from ship fuel on the atmosphere of Xiamen is increasing year by year.Cd,Mg,Ca and V in the atmosphere are mainly affected by human beings,and the influence of industrial emissions in Xiamen is greater at SM than XA.The seasonal characteristics of organic carbon(OC)and elemental carbon(EC)concentrations are related to the typical subtropical monsoon climate.Increase in demand for power supply in summer in Xiamen urban area resulting in a significant increase in the ratio of EC/PM2.5 at SM.OC and EC at XA come from the same source,and the sources of OC and EC are more complex at SM.At present,secondary pollution formation is still one of the main sources of air pollution in Xiamen.4.Chr,Pyr,BghiP and IP are the main PAHs(Polycyclic Aromatic Hydrocarbons)in Xiamen.At SM,PAHs are greatly influenced by the coal combustion and gasoline vehicle exhaust.At XA,PAHs are greatly influenced by cooking,diesel exhaust and gas combustion.Primary source,regional input and photochemical reaction of high temperature season are important sources of organic acids in Xiamen.Organic acids at SM are mainly caused by the direct emission of vehicle exhaust and the photochemical reaction of a large number of precursors under strong light conditions.Organic acids at XA come from plants,food cooking and photochemical reaction.5.Organic matter is the largest category of PM2.5 in Xiamen,and mineral elements fluctuate greatly in different seasons.The results of factor analysis are consistent with the results of PMF model.PMF model found out six sources:secondary particle source,motor vehicle exhaust,coal burning,heavy oil burning,fugitive dust and biomass burning.At SM,PM2.5 is dominated by secondary particulate sources and motor vehicle exhaust,and PM2.5 at XA is dominated by fugitive dust and secondary particulate sources.