| In order to understand the chemical composition of PM2.5 in Yuncheng,Wuhan Tianhong atmospheric particulate sampling instrument TH-150C were used to collect the PM2.5 of Yuncheng city in July 2014?April 2015,18 kinds of elements,carbonaceous component(including organic carbon and element carbon)and 5 kinds of water soluble ion in PM2.5 were measured to obtain the chemical characteristics of PM2.5 in Yuncheng City in order to provide scientific basis for pollution control in Yuncheng.The result showed that Na,Si,Ca,Al,Fe were the most content of elements in PM2.5 in Yuncheng city,the sum of these five elements was 16.6013%,Na,Si,Ca,Al,Fe were typical crustal material,indicating that the soil dust is an important source of PM2.5 in Yuncheng City.The results of enrichment factor showed that the enrichment factors of Zn,Cr,Cu,Pb,Ni,As,V,Na is greater than 10,indicating that the human source is the main source of these elements.The enrichment factor of Na reached nearly 30,high degree of enrichment may be affected by the Salt Lake dust in Yuncheng.Potential ecological risk assessment of heavy metals showed that the potential ecological risk of Pb and As in PM2.5 is very strong,the potential ecological risk of Cu is strong,the potential ecological risk of Ni is slightly strong,the potential ecological risk of Mn?Zn?Cr and Co is slight;the potential ecological risk of heavy metals in the winter is higher than the other three seasons.The mass concentration of carbonaceous components in winter was significantly higher than that in other seasons.There was no significant difference between the three seasons of spring,summer and autumn.Correlation analysis of OC and EC showed that in winter(January)has the best correlation between OC and EC(R2=0.9195),showed that the sources of OC and EC in winter in Yuncheng in PM2.5 is similar to that derived from coal combustion and vehicle emissions;while OC and EC in spring and summer in PM2.5 in Yuncheng city showed poor correlation(R2=0.5884 and 0.2588,respectively).The concentration of water-soluble ions was highest in winter(186.7 ?g/m3),followed by autumn(66.5 ?g/m3),summer(38.3 ?g/m3)and spring(29.2?g/m3).SO42-and NO3-occupyed a high proportion of PM2.5,the annual mass fraction was 19.0115%,10.0676%,were important parts of PM2.5 in Yuncheng.The average value of NO3/SO42-was 0.5296,less than 1,indicating that compared to mobile sources(motor vehicle exhaust),PM2.5 in Yuncheng is influenced more by coal dust.The average SOR was 0.7695 during the observation,the average of NOR was 0.5466,were both greater than 0.1,indicating that sulfate and nitrate in PM2.5 in Yuncheng city mainly come from the secondary transformation.R2 of SO42-and SO2 in spring,summer,winter were 0.1321,0.0033,0.1273,respectively,indicating that SO42-and it's gaseous precursors SO2 did not show a good linear relationship.R2 of NO3-and NO2 in April,July,January,were 0.1677,0.1836,0.0305,respectively,showing that the correlation between NO3-and NO2 is not strong,the conversion to NO3-is also affected by other factors.The composition of PM2.5 during the whole sampling period was:28%crustal material,19%SO42-,15%organic matter,11%elemental carbon,10%NO3-,1%heavy metal.Spring:32%crustal material,14%SO42-,13%organic matter,9%elemental carbon,4%NO3-,2%heavy metal;Summer:36%crustal material,25%SO42-,13%organic matter,11%elemental carbon,4%NO3-,2%heavy metal;Autumn:30%crustal material,17%SO42-,13%organic matter,10%elemental carbon,15%NO3-,1%heavy metal;Winter:15%crustal material,20%SO42-,organic matter 20%,14%elemental carbon,17%NO3-,1%heavy metal?... |
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