Study On The Pollution Characteristics Of VOCs And Comparative Analysis For The Provincial Capital Of Zhengzhou And Heavy Industry City Of Jiyuan

Comprehensive city of Zhengzhou and heavy industry city of Jiyuan are the hazepolluted cities in Henan.Volatile organic compounds(VOCs)are the precursors of secondary organic aerosol(SOA)and O3 formation.PM2.5,O3,VOCs and trace gases were simultaneously monitored by using online instruments at Zhengzhou and Jiyuan from 1st to 31st December,2019 and 1st Jun to 31st August,2020.The characteristics,sources,ozone formation potential(OFP),secondary organic aerosol formation potential(SOAP)and health risks assessment of VOCs were analyzed.Meanwhile,the characteristics of different pollution periods in two cities were also compared and analyzed.In winter,the mean concentrations of total detected VOCs(TVOC)were 48.8 ±23.0 ppbv in Zhengzhou.Alkanes,halocarbons and aromatics were the predominant VOCs.Based on the positive matrix factorization model,five major sources of VOCs were identified as vehicular exhaust,industrial processes,combustion,fuel evaporation,and solvent use.The carcinogenic and non-carcinogenic risk values of species were calculated.The total non-carcinogenic risks exceeded the acceptable ranges.Most VOCs posed no non-carcinogenic risk during three haze events.However,the mean concentrations of TVOC were 54.3±27.5 ppbv in Jiyuan.Alkanes,halocarbons and alkyne were the predominant VOCs.Eight major sources of VOCs were identified,which are LPG/NG,coking industry,PVC industry,solvent usage,fuel evaporation,combustion,and vehicular exhaust.The health assessment shows that the HQ of most VOCs were lower than a safe level except acrolein.Based on SOAP method,it is estimated that aromatics is the largest contributor to the SOAP.In summer,the mean concentrations of TVOC were 35±15.1 ppbv in Zhengzhou.Alkanes,halocarbons and OVOCs were the predominant VOCs.Five major sources of VOCs were identified,which are vehicle exhaust,industrial sources,solvent usage,combustion,fuel evaporation and biogenic sources.The ozone formation potential(OFP)of species were calculated.Aromatics contributed the most to O3 formation,followed by alkanes and alkenes.OVOCs,halocarbons and sulfide contributed the least to O3 formation.However,the mean concentrations of TVOC were 24.9 ± 10.8 ppbv in Jiyuan.Alkanes comprised the highest proportion,followed by halocarbons,alkenes,alkyne,OVOCs and aromatics.Seven major sources of VOCs were identified,which are vehicular exhaust,industry,fuel evaporation,solvent usage,PVC industry,LPG/NG,and biogenic sources.Based on OFP method,it is estimated that alkenes,aromatics and alkanes were the predominant contributors to the OFP.From the comparison,we know that the mean concentration of TVOC and all components(except OVOCs)of Zhengzhou in winter were higher than those in summer;vehicle emission source contributed the most in winter and summer,followed by industrial source;the contribution of combustion and solvent source in winter was higher than that in summer,but plant source was did not find in winter.The average concentration of TVOC in Jiyuan in winter was more than twice that in summer;the concentration of each component was higher than that in summer;in winter,there were more coking industrial source and LPG/NG source than in summer,but plant source was did not find.Besides,in winter,the mean concentration of TVOC in Zhengzhou is lower than that in Jiyuan,especially halocarbons,aromatics and OVOCs;the largest contributor to ambient VOCs was vehicular exhaust in the two cities;more VOCs in Zhengzhou posed carcinogenic risk to public health.In summer,the mean concentration of TVOC in Zhengzhou was higher than that in Jiyuan,especially alkanes,halocarbons and aromatics;vehicular exhaust and industry were the main sources of VOCs in the two cities;aromatics,alkenes and alkanes had the most contribution to ozone production in the two cities.