| In recent years PM2.5 pollution becomes serious in China,especially in the northern cities the haze phenomena occured frequently during the heating period,fine particulate matter pollution has become a prominent atmospheric environmental problems.With the improvement of Yungang Grottoes' well-knownness,number of visitors increases,the environmental air quality at the scenic spot has attracted more and more attention.This study determined the chemical composition of PM2.5 collected at Yungang Grottoes scenic spot by bulk and single-particle analysis technology,analyzed concentration change of various constituents and possible sources of PM2.5,understood characteristics of atmospheric pollution at Yungang Grottoes scenic spot,which will provide scientific basis for improvement of scenic environment air quality.Firstly,we collected the atmospheric fine particle samples during December,2012,July,2013,October,2014 and April,2014 four sampling periods by using the TH-150 mid volume atmospheric PM2.5 sampler at two sampling points?20#Grottoe sampling point and Yungang Grottoes Research Institute sampling point?,sampling time was 9:00 a.m.-17:00 p.m..Besides,single particle samples were collected by the MAY cascade impactor sampler at 20#Grottoe sampling point every afternoon.Then we measured the content of anion and cation,heavy metals,OC and EC using ion chromatograph,ICP-AES,carbon analyzer respectively,as well as analysed the single particle through quantitative EPMA technique.The results showed that:?1?The scenic atmospheric PM2.5 daily average concentration exceeded the limit of one national standard concentration in most of the time,December was most serious,which may be connected with coal combustion in winter for heating.?2?Content of secondary ion SO42-,NO3-,NH4+ was higher in atmospheric PM2.5;the average concentration ratio of NO3-and SO42-was less than 1,which represented the source of water-soluble ions was mainly the stationary source?coal?;correlation analysis indicated that combination ways were mainly?NH4?2SO4,NH4HSO4,NH4NO3;anion and cation balance analysis indicated that atmospheric PM2.5 was acid,which may corrode and and damage the surface of grottoes.?3?Concentration of OC was greater than that of EC;concentration of OC and EC had good linear correlation,indicating OC and EC had common source;average of OC/EC was 6.42 which was more than 2,secondary organic carbon?SOC?accounted for a high percentage of OC.?4?Concentration of heavy metal elements was higher in April and December,lower in October and July;Zn,Pb,Cr appeared higher levels,contents of Cu,Ni,Cd were lower.?5?The contents of primary mineral dust,reacted mineral dust,OC,EC and secondary particles were higher,the contents of reacted NaCl particles,rich K particles,rich Fe particles and fly ash were lower.?6?The primary mineral particles whose content was most and it was associated with sand in the spring and winter;sulfuric acid type reacted mineral dust was more than nitric acid type;EC particle mainly contained coal dust and soot,which were related to coal and incense buring.The above experimental results showed that secondary ion,carbon composition and mineral dust particles is the main composition of PM2.5 at Yungang Grottoes scenic area,atmospheric PM2.5 mainly sources from coal combustion,the sand dust and motor vehicle exhaust.It is suggested that relevant departments should control corresponding pollution sources according to pollution characteristics at different times to reduce the effects of atmospheric PM2.5 on tourists' health and grottoes. |
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