Source Analysis And Emission Assessment Of Atmospheric Volatile Organic Compounds In Harbin-Changchun Urban Agglomerations

With the development of the economy and urbanization in China,the population is increasing rapidly and air pollution is becoming a more serious concern.Since 2013,the concentration of particulate matter（PM）in the atmospheric environment has been decreasing yearly,but ozone（O₃）pollution has remained at a high level.Continuous monitoring data of ozone in key cities indicates that the concentration of ground-level ozone in China is showing an increasing trend each year.Ozone pollution is getting severe and has become the primary pollutant in some cities that do not meet air quality standards.Volatile organic compounds（VOCs）are significant precursors to the formation of tropospheric ozone.Due to the complex chemical mechanisms involved in VOCs and the nonlinear response relationship between VOCs and O₃,controlling ozone pollution poses an important challenge.Therefore,identifying VOCs’composition,emission characteristics,and sources is crucial for controlling urban ozone pollution.However,current studies on VOCs mainly focus on fast-growing cities or urban agglomerations,with relatively few studies in Northeast China.The Harbin-Changchun urban agglomerations（HCA）are the northernmost regional urban agglomerations in China,with a relatively complex industrial structure and prominent VOCs pollution issues.Therefore,obtaining the composition,emission characteristics,and sources of VOCs in the atmospheric environments of various cities will provide a scientific basis for investigating the effects of regional ozone pollution and developing corresponding control measures.In this study,the central cities of HCA were selected as the study region.Firstly,an O₃control area was identified by modeling.Secondly,mobile and stationary monitoring data were used to establish industrial VOCs profiles and urban VOCs profiles in the VOCs control area of Northeast China.Next,the maximum incremental reactivity（MIR）was used to estimate ozone formation potential（OFP）,and the fractional aerosol coefficients（FAC）were used to estimate secondary organic aerosol formation potential（SOAP）.This helped to identify key active compounds and major sources for urban ozone and secondary organic aerosol.Finally,a specialization emission inventory of VOCs for the central cities（i.e.,Harbin,Daqing,Suihua,Changchun,Jilin,Siping,and Liaoyuan）was calculated using the industrial profiles developed in this study.The results suggested that the central cities were all in the VOCs control area,and during the monitoring period,Jilin City had the highest concentration of environmental atmospheric VOCs emissions,while Liaoyuan and Siping had the lowest concentration.The results of various industrial source profiles show that the petrochemical and chemical industries have the greatest impact on urban VOCs pollution,aromatics and halocarbons emitted by these industries contribute the most to VOCs pollution.Among them,BTEX（benzene,toluene,ethylbenzene,and xylene）were the compounds with the highest concentration ratio.The urban source profile results showed that alkenes,halocarbons,and aromatics are the main species of VOCs pollution in the central cities.Combining the results of OFP and SOAP,this study found that alkenes and aromatics in the atmosphere have a significant impact on urban ozone and secondary organic aerosol,which cannot be ignored.Consistent with the results of industrial source profiles,BTEX are the compounds that contribute the most to OFP and SOAP.Speciation emission inventories of VOCs were calculated based on source profile,including industrial processes and solvent uses.The emissions for Jilin,Changchun,Harbin,Liaoyuan,Daqing,Siping,and Suihua were estimated to be29002.8 t,12441.3 t,9376.3 t,4522.6 t,3855.8 t,2776.6 t and 2314.0 t,respectively.Xylene and ethylbenzene were the top emitting VOCs.Based on the monitoring and emission assessment results,it is suggested to prioritize reducing the concentration of BTEX in raw materials of petrochemical and chemical industries or strengthening end-of-pipe control to reduce VOCs emissions.The accurate identification of VOCs emission characteristics,sources and contributions to ozone and secondary organic aerosol provides a scientific basis for precise control and numerical simulation of VOCs in the Northeast area.