A Preliminary Study On Characteristics And Source Of Volatile Organic Compounds In The Urban Area Of Shuozhou

A wide range of volatile organic compounds(VOCs), especiallynon-methane hydrocarbons(NMHCs) that contains the complex chemicalcomponents, is an important precursors of photochemical oxidants. VOCstogether with NOx plays key role in the formation of photochemical smog,generated by the photochemical reaction of secondary pollutants, such asozone(O3), peroxyacetyl nitrates(PAN) and secondary organic aerosols(SOR),which have affect to the environment, weather,climate and human health.Therefore, the study of VOCs distribution and composition, sources of VOCs inambient air is important for the prevention of atmospheric pollution.To investigate VOCs in ambient air of Shuozhou, the samples werecollected by Summa canister at two points (SH, PS) in the urban area, and theconcentrations of56kinds of VOCs species were analyzed by usingGC/MSD/FID/ECD, the characteristics including concentration levels of VOCs,spatial distribution and photochemical propertis were investigated, the healthrisk assessment and the main sources of VOCs were discussed. The mainconclusions obtained are as follows:(1) The VOCs in ambient air of Shuozhou included29kinds of alkanes,11kinds of alkenes, and16kinds of aromatic hydrocarbons. The averageconcentration of total volatile organic compounds (TVOCs) was76.40μg/m3,the range of variation was36.32~141.42μg/m3. The main components of VOCsin SH and PS point were alkanes and aromatic. The concentration of aromatichydrocarbons was36.12μg/m3in SH point, significantly higher than PS point. (2)1-butene made the major contribution to the LOHin SH point, followedby1,2,4-trimethyl benzene.1-butene also made the major contribution to theLOHin PS points, followed by propylene. The major contribution of alkanes,alkenes, aromatics to the LOHof TVOC in SH point was17%,33%,45%and17%,54%,22%in PS point.In terms of OFP, the top10species consisted of ethylene, butane, ethane,propane, iso-pentane, iso-butane, n-pentane, propylene, toluene, and xylene.These species consisted of six of alkanes, two olefins, two aromatichydrocarbons, accounted for96.29%of the OFP in the region, although theycontributed low percentage to the total VOCs.(3) The results of HRA indicated that the range of each species ofnon-carcinogenic risk value was1.32×10-3~8.12×10-1. The sum ofnon-carcinogenic risks (HI) was less than1in two points. The cancer risk is lessthan the suggested value of USEPA. It indicated that the exposure could notcause potential harm to human health.(4) The main source of VOCs in ambient air of Shuozhou were divided intothree categories including vehicle exhaust, combustion emissions and solventevaporation based on principal component analysis. The interpretation of vehicleexhaust to the data variable of VOCs were48.737%,64.707%in SH point andPS point.