| In this study,measurements of volatile organic compounds?VOCs?were gathered for a long-term from March 23,2018 to January 9,2019,using TH-300B in urban Suqian to measure56 kinds of VOCs.The PMF model was used to analyze the emission sources of VOCs and investigate the characteristics of the sources,and the potential source area of VOCs source was analyzed by combining PSCF and CWT.The information entropy method was used to calculate the list of priority control target species of VOCs based on four screening indexes:VOCs mass concentration,ozone formation potential?OFP?,secondary organic aerosol formation potential?SOAFP?and toxicity.During the observation period,the volume fraction of total volatile organic compounds?TVOCs?was 17.38±12.05×10-9,and the highest volume fraction of alkanes was 60.74%,alkenes was 17.06%,aromatics was 12.66%,and acetylene was 9.54%.VOCs pollution showed obvious seasonal distribution and diurnal variation characteristics.The volume fraction of TVOCs was low value in summer and high value in winter.The diurnal variation of alkanes,alkenes,acetylene and aromatics showed a bimodal structure.The highest value appeared between 7:00 and 9:00,and the lowest value of the whole day appeared at around 14:00?16:00,and the second peak appeared at 20:00 in the evening.The effect of meteorological elements on VOCs was obvious.The volume fraction of VOCs decreased with the increase of temperature at 1?40?,and there was a positive correlation between humidity and VOCs volume fraction in the range of 11?80%relative humidity.The influence of wind speed and direction on VOCs was obvious in different seasons.Five sources with local characteristics were identified by PMF,the industry contributed most to the VOCs?34.7%?,followed by vehicle exhaust?23.6%?,fuel evaporation?21.5%?,solvent use?15.6%?,plant source?4.6%?.In the high temperature environment,the proportion of plant source increased obviously,the proportion of solvent use and industrial source increased at first and then decreased with the increase of temperature,and the proportion of vehicle exhaust decreased with the increase of temperature.The proportion of plant sources decreased with the increase of humidity,the percentage changes of industrial source,vehicle exhaust source and fuel evaporation source were not very sensitive to the change of humidity,and the proportion of solvent use increased slightly.VOCs was mainly affected by air mass transport from southeast and northeast regions,and the potential sources affecting Suqian VOCs were mainly distributed in Southern Shandong Province,Lianyungang,Suzhou-Wuxi-Changzhou area,Huai'an,Yangzhou,Southwest Xuzhou and Suzhou?City in Anhui Province?.The contribution of ozone formation of VOCs was alkenes?45.77%?,aromatics?32.66%?,alkanes?20.5%?,acetylene?1.07%?,both the contribution of OFP and SOAFP showed the characteristics of high value in winter and low value in summer.Aromatics were the components that contributed a lot to O3 and SOA generation.The contribution of OFP from industrial source was 28.2%and that of SOAFP from solvent use source was 49.4%.The key sources of VOCs to control the generation of OFP and SOAFP were industry,vehicle exhaust and solvent use sources.In the list of VOCs priority control target species,there were 22 species in the first class,the second class included 24 species while the other belonged to the third class.In general,the optimal control target species of VOCs in Suqian mainly considered aromatics. |
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