运城市四季VOCs特征、来源及臭氧形成敏感物种

Characteristics,Sources,and Ozone-sensitive Species of VOCs in Four Seasons in Yuncheng

基于2021年运城市城区站点全年VOCs观测数据,对运城市四季VOCs体积分数、组分特征、来源及臭氧形成敏感物种进行分析.结果表明,运城市城区φ(VOCs)年均值为(32.1±24.2)×10^(-9),处于全国中等水平,四季φ(VOCs)均值从高到低依次为:冬季(46.3×10^(-9))>秋季(35.5×10^(-9))>春季(25.6×10^(-9))>夏季(21.2×10^(-9)),烷烃和OVOCs占比最高,二者贡献了运城市69.0%~80.4%的TVOCs,春夏季OVOCs占比更高(41%~43%)而秋冬季烷烃占比更高(42%~43%),主要受到源排放变化的影响.机动车源、LPG/NG源、工业源和燃烧源是运城市城区VOCs的主要来源,四季贡献率最高的分别为机动车源(春季,28.5%)、二次源+燃烧源(夏季,29.0%)、LPG/NG源(秋季,30.4%)和燃煤源(冬季,27.3%).运城市夏季臭氧形成处于过渡区,其他季节处于VOC控制区,臭氧生成对烯烃(异戊二烯、乙烯和丙烯)、OVOCs(乙醛、丙醛、丙烯醛、正丁醛)和芳烃(二甲苯、甲苯、苯)最敏感,其中冬季对乙烯最敏感,其他季节对异戊二烯最敏感,应对这些敏感物种相关的一次排放源进行减排以实现臭氧浓度改善的目标.

Based on the one-year observational data of volatile organic compounds(VOCs)in an urban area of Yuncheng in 2021,the concentration,composition,sources,and ozone-sensitive species of VOCs in four seasons were analyzed.The results showed that the average annual concentration of VOCs was(32.1±24.2)×10^(-9),i.e.,at the national middle level.The seasonal concentrations of VOCs were in the order of:winter(46.3×10^(-9))>autumn(35.5×10^(-9))>spring(25.6×10^(-9))>summer(21.2×10^(-9)).Alkanes and OVOCs were the most dominant VOCs compounds,accounting for 69.0%-80.4% of TVOCs in Yuncheng.Affected by changes in source emissions,the proportion of OVOCs was higher in spring and summer(41%-43%),whereas the proportion of alkanes was higher in autumn and winter(42%-43%).Vehicle exhaust,LPG/NG,industrial production,and combustion sources were identified as the main sources of VOCs in Yuncheng.The largest contributors in the four seasons were vehicle exhaust(28.5% in spring),secondary+combustion sources(29.0% in summer),LPG/NG sources(30.4% in autumn),and coal combustion(27.3% in winter).The ozone formation was located in the transitional regime in summer and in the VOC-limited regime in other seasons.Ozone production was more sensitive to alkenes(isoprene,ethylene,and propene),OVOCs(acetaldehyde and propanal),and aromatics(xylene,toluene,and benzene).Winter was more sensitive to ethylene,and the other seasons were more sensitive to isoprene.The primary emission sources related to these sensitive species should be reduced to achieve the goal of air quality improvement.