Pollution Characteristics And Sources Analysis Of Volatile Organic Compounds In Jincheng

Volatile organic compounds(VOCs)are important precursors of ozone(O3)and secondary organic aerosols(SOA),which can be generated by photochemical reactions from VOCs.Furthermore,VOCs also can affect the ecological environment and climate change directly,even endanger human health.In this study,VOCs were collected by Summa canister in winter and summer,2017 in Jincheng,and analyzed by gas chromatography/mass Spectrometer detector(GC/MSD/FID).The concentrations and variation of VOCs in each season were calculated.The potential contribution of VOCs to O3 and SO A was evaluated.The sources of VOCs in different season were also studied.The main findings are as follows:1.The average concentrations of total volatile organic compounds(TVOCs)in winter and summer in Jincheng were 93.35μg·m-3and 47.50μg· m-3respectively.The proportions of the total top ten VOCs species,mainly including benzene,toluene and C2～Ca alkanes,were 61.39%and 70.78%in winter and summer,respectively.The major VOCs groups were alkanes and aromatic hydrocarbons in both seasons.The average diurnal variation of VOCs concentration showed that the concentration peak occurred at 8:00-10:00 AM both in winter and summer,with the peak concentration of 112.10μg·m-3 and 71.48μg ·m-3 respectively.2.The OH consumption rates of VOCs were 7.13 s-1 and 4.31 s-1 in winter and summer,respectively.Although the photochemical reaction rates of VOCs is lower in winter than in summer,but the chemical reactivity of VOCs was higher in winter than in summer due to the higher level of VOCs in winter,The most reactive species was propylene,followed by trans-2-butene and 1-butene in winter,while isoprene,followed by cis-2-butene,1-butene in summer.The most reactive VOCs were alkene compounds both in winter and summer.3.Ozone Formation Potential(OFP)in winter is 2.06 times that of summer.Aromatic hydrocarbon and alkene were the largest contributor VOCs groups to OFP in winter and summer,accounting for 36.63%and 45.36%of total OFP,respectively.The SOA formation potential in winter is 2.57 times that of summer.Aromatic hydrocarbons species is the largest contributor to SOA both in winter and summer,with the contribution of 96.99%and 93.27%to the total SOA,respectively.The contribution of aromatic hydrocarbons to SOA is higher in winter than in summer.Therefore,controlling the emission of aromatic hydrocarbons can not only reduce O3 pollution in summer,but also reduce the generation of SOA effectively in winter.4.The results of source apportionment by Positive Matrix Factorization(PMF)shows that,the sources of industrial and other source,combustion,vehicle emission,solvent usage,plant contributed 30%,25%,23%,20%,2%to VOCs in winter,while 33%,18%,23%,12%,14%in summer,respectively..By calculating the contribution of each source to OFP,we can see that the source of industrial and other source,combustion,vehicle emission,solvent usage have greater contribution to OFP in both seasons..which resulted that controlling VOCs emission from these sources will reduce the ozone pollution effectively in summer.Furthermore,industrial source and solvent sources are the largest contributor to SOA both in winter and summer.Controlling VOCs from these sources can effectively prevent the occurrence of composite pollution weather,like haze,in Jincheng.