Observational Study Of Volatile Organic Compounds Pollution Characteristics In Nanjing Industrial Zone

VOCs is ubiquitous in the atmosphere with a crucial role in the atmospheric photochemistry and secondary organic aerosol(SOA)formation,in other words,it is the critical precursor of O3,PAN and SOA in the troposphere.Moreover,it can have an indirect impact on the human health,environments and climate.In this study,a custom-built proton transfer reaction ion-drift chemical ionization mass spectrometer(PTR-ID-CIMS)was deployed near an industrial zone in the Yangtze-River-Delta(YRD)region of China to investigate industry-related emissions of volatile organic compounds(VOCs)from April 15 to April 30,2015.15 VOCs were detected(HCHO,Acetaldehyde,Acetone,MVK+MACR,C4-carbonyls,C5-carbonyls,MTBE,Propylene,Isoprene,Terpenes,Benzene,Toluene,C8-aromatics,C9-aromatics and Acetonitrile)and CIMS measurements of HCHO were inter-compared with off-line measurements using 2,4-dinitrophenylhydrazone(DNPH)cartridges and the results showed fairly good agreement(slope = 0.81,R2 = 0.80).We analyzed the level,diurnal variation,correlation of these kinds of VOCs,estimated the relative contribution from VOCs in the O3 formation by the MIR constant and KOH,finding that the concentration of VOCs varied from 2.92 to 128.1 ppbv with a mean of 27.6±19.1 ppbv,the frequency of pollution periods up to 43.8%;Meanwhile,the concentration level of 4 kinds of VOCs was OVOC>Aromatics>Alkenes>Acetonitrile with 65.4%,20.5%,12.6%,1.50%,respectively.The diurnal variation of VOCs had two clear peaks indicating the potential impact of transportation and industry;However in this observation,Toluene/Benzene was far away from 2 that a signal of vehicle emission,indicating an impact of industry;Moreover there had a good correlation among OVOC,Alkenes and Aromatics,which was a strong signal of industry-related emissions inspite of the second formation and transportation.The contribution to O3 formation calculated by MIR was followed as:Aromatics>Alkenes>OVOC.Using a multiple linear regression fit model,on average the observed HCHO can be respectively attributed to secondary formation(13.8%),background level(27.0%),and industry-related emissions,i.e.,combustion sources(43.2%)and chemical productions(16.0%).Moreover,within the plumes the industry-related emissions can account for up to 69.2%of the observed HCHO;Meanwhile,the PMF results also agreed with the conclusion that industrial emissions were the main influence factors of HCHO and the contribution to HCHO was up to 60.2%.This work has provided direct evidence of strong primary emissions of HCHO from industry-related activities,especially in the pollution period.