Emission Inventory Of Volatile Organic Compounds And Its Ozone Formation Potential In Huai’an City

In recent years,with the implementation of a series of air pollution control measures,the concentration of pollutants such as sulfur dioxide and nitrogen oxides has continued to decline,but the concentration of ozone has continued to rise.Volatile organic compounds（VOCs）,as important precursors of urban photochemical smog and haze,play a key role in the generation of ozone and secondary organic aerosols.Accurate analysis of VOCs emission characteristics and their impact on ozone generation can help to provide a scientific basis for reducing ozone pollution and VOCs emissions.This study took Huai’an City as the research area.Firstly,a three-level source classification system covering 113 types of emission sources was established,and the emission factor method was used to establish the anthropogenic VOCs emission inventory of Huai’an City in 2017.Detailed activity level data was mainly obtained from the Second National Census on Pollution Sources,and the emission factors were from Handbook of Accounting Factors for Production and Discharge of the Second National Census on Pollution Sources,related emission inventory guidebook and literature.Secondly,on the basis of collating the domestic VOC source profiles research results,the total VOCs emissions were decomposed to obtain speciated VOC emissions.Thirdly,based on the maximum incremental reactivity,the ozone formation potential（OFP）of anthropogenic VOCs in Huai’an City was estimated.Finally,with the help of Arc GIS platform,using various information of latitude and longitude,road distribution,population density distribution and land use,the spatialization of VOCs emission inventory and OFP with a spatial resolution of1km×1km have been realized.This study has made improvements in source classification,activity data,emission factors,etc.,thereby improving the accuracy of VOCs emission accounting.The results show that the total anthropogenic VOCs emissions of Huai’an City in2017 were estimated to be 36 kt,contributed mainly by industrial process（41%）,solvent use（32%）and transportation（13%）.In the secondary classification,petroleum refining,off-road transportation,on-road transportation,pesticide use,steel industry and asphalt paving were the major contributors.Of the city’s emissions in2017,60%were emitted from industrial enterprises,and industrial VOCs emissions were concentrated in a few large industrial enterprises.At the district level,Qingjiangpu District and Xuyi County have the largest emissions.High VOCs emission densities were found in and around Qingjiangpu District,the center of Xuyi County and the western part of Jinhu County,where industrial clusters locate.The components of anthropogenic VOCs emitted in Huai’an City are mainly alkanes and aromatics,accounting for 33%and 27%,respectively.Species such as toluene,styrene,ethanol,n-hexane,ethane,m/p-xylene,benzene,propane,ethylbenzene and ethylene have the largest emissions.In 2017,the OFP of anthropogenic VOCs in Huai’an City was 107 kt of O₃.Aromatics and alkenes contribute significantly to OFP,followed by oxygenated VOCs and alkanes.The major VOC species that contribute to OFP are m/p-xylene,propylene,ethylene,toluene,formaldehyde,acetaldehyde,o-xylene,1,2,4-trimethylbenzene,ethylbenzene and styrene.Solvent use and industrial process sources contribute the most to OFP.In the secondary classification,non-road transportation,petroleum refining,on-road transportation,household biomass combustion,steel industry,machinery equipment manufacturing and industrial energy consumption contribute the most to OFP.Areas with high OFP intensity are mainly located in Qingjiangpu District,and scattered areas in Hongze District,Xuyi County and Jinhu County,where industrial enterprises locate.Monte Carlo simulation was used to assess the uncertainty of the emission inventory,and the results showed that the overall uncertainty of the VOCs emission inventory was（-11%,+20%）.Based on the results of this research,this study suggests that when determining the emission reduction priorities for local VOCs emission reduction plans,not only the VOCs emissions should be concerned,but also the OFP of various VOCs should be considered.Combining high spatial resolution VOCs emission inventory with OFP assessment will help to propose more effective VOCs and ozone control strategies.At the same time,attention should be paid to emission sources such as non-road transportation,petroleum refining,on-road transportation,household biomass combustion,steel industry,machinery equipment manufacturing and industrial energy consumption,as well as several areas with high OFP intensity in Qingjiangpu District,Hongze District,Xuyi County and Jinhu County.