| PM2.5 is proved to be linked to human health,atmospheric visibility and global climate change,with features of physiological toxicity,light extinction and transport at several scales.With the rapid development of urbanization,fine particles(PM2.5)is the most important air pollutants in China in recent years.Therefore,it's important and meaningful to determine the chemical compositions and main source of PM2.5 and the contribution rate of various sources for policy-making.A total of 64 PM2.5 samples were collected from April 2015 to January 2016 in Zhengzhou.Water-soluble inorganic ions and elements in PM2.5 were analyzed by ion chromatography and inductively coupled plasma mass spectrometry.?1?The annual average concentrations of PM2.5 was significantly higher than the Chinese national ambient air quality standard?35 ?g/m3?.The seasonal average of PM2.5 concentration varied with the lowest concentrations of PM2.5 in summer and highest in winter.?2?NH4+,SO42-and NO3-were the major ions,contributing 12%,19% and 16% to the total PM2.5 mass.The highest concentrations of NH4+,SO42-and NO3-ions were observed in winter.SO42-,NO3-and NH4+ ions occurred as?NH4?2SO4 and NH4NO3.?3?The crustal elements?Mg,Al,Ti and Fe?dominated the 24 detected elements in PM2.5,with the highest concentrations in spring in Zhengzhou,which might be due to frequent sandstorm fromnorth carrying abundant soil dusts in spring in C hina.Al was used as a reference element to determine the enrichment factor?EF?.High EF values of Cd,Mo,Pb,Ag,Zn and Cu in PM2.5 indicate the extent of air pollution,which is generally caused by emissions of vehicles and industries.Risks posed by heavy metals on human health were assessed.The hazard index was higher than 1 in Zhengzhou,indicating that V,Cr,As,Mn,Cd,Co,and Ni may cause accumulative noncarcinogenic health effects on humans.Cr in PM2.5 is a potential carcinogenic risk?3.0×10-4?when inhaled by child.?4?The chemical composition of atmospheric particulates changed when the heavy pollution process occurred: mass percentage of secondary inorgnic ions increased to above 50%.The percentage of crustal elements decreased to 1.3%,while the mass fraction of carbonaceous component did not fluctuate greatly,indicating that crustal elements had little effect on the formation of heavy polluted weather.Meteorological factors were chosen and their individual relationships with concentrations of PM2.5 were investigated using partial correlation and pearson correlation analyses.It was demonstrated that the concentrations of PM2.5 were positively correlated with temperature and relative humidity,respectively.?5?The positive matrix factorization and chemical mass balance were applied to identify the source contribution of PM2.5 concentrations in the study area.Source categories were determined based on the chemical component abundances in the source profiles.The results indicated that seven factors were obtained.The factors are identified as follows: secondary aerosol?28.9%?,motor vehicle exhaust?14.2%?,coal burning?20.5%?,industrial emission?12.2%?,biomass burning?11.9%?,soil dust?9.0%?,and construction dusts?4.1%?.Overall,the results indicate that PM2.5 pollution must be considered seriously in Zhengzhou,and the local government must take necessary measures to prevent and control air pollution,as well as protect human health and ecosystems. |
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