典型中部地区南阳市VOCs污染特征及对O_(3)生成影响

VOCs Pollution Characterization and Its Influence on O3 Pollution in a Typical Central China City Nanyang

为研究我国中部地区臭氧(O_(3))污染成因和挥发性有机物(VOCs)污染特征及来源,于2022年对河南省南阳市的VOCs进行了为期一年的在线观测,并探究了其对O_(3)生成的影响.南阳市占地面积大、人口多,是我国中部地区典型代表城市,本研究将2022年南阳市环境空气中O_(3)月均浓度较高的月份(5-9月)定义为O_(3)污染频发月,其余月份定义为非O_(3)污染频发月,研究了南阳市O_(3)污染成因及VOCs污染特征和来源.结果表明:(1)南阳市非O_(3)污染频发月TVOCs(总挥发性有机物)体积分数为32.1×10^(-9)±13.2×10^(-9),比O_(3)污染频发月(19.4×10^(-9)±5.9×10^(-9))高65.5%.但O_(3)污染频发月的OVOCs(含氧挥发性有机物)的体积分数比非O_(3)污染频发月增加了5.3%,表明二次生成可能是南阳市O_(3)污染频发月中OVOCs一个重要来源.(2)臭氧生成潜势(OFP)计算结果表明,在2个研究阶段中,OVOCs的OFP贡献率超过50%,甲醛(35%)、乙醛(10%)、乙烯(9%)、间/对-二甲苯(5%)、甲苯(3%)是南阳市2个研究阶段中共有的影响O_(3)生成的关键VOCs物种.(3)经验动力学模型(EKMA)及相对增量反应活性(RIR)结果表明,在O_(3)污染频发月,南阳市O_(3)生成处于协同控制区,O_(3)生成对人为源VOCs(特别是烯烃和芳香烃)和NO_x更敏感.(4)南阳市O_(3)污染频发月VOCs的正定矩阵因子分解模型(PMF)结果显示,汽油车排放源(占29%)、溶剂使用源(占23%)、工业过程排放源(占21%)、居民生活排放源(占11%)、柴油车排放源(占10%)与植物源(占6%)是大气中VOCs的主要来源.研究显示,南阳市在O_(3)污染频发月期间二次生成是OVOCs的重要来源,且汽油车排放源是南阳市空气中VOCs的重要来源.

In order to study the ozone(O_(3))pollution and the characteristics and sources of volatile organic pollutants(VOCs)pollution in central China,this study conducted online observations of VOCs in 2022 and investigated their impact on the formation of O_(3) in Nanyang City,Henan Province.In order to guide more effective ozone and VOCs control in central China,this study conducted a one-year online VOCs monitoring in Nanyang City,a typical city in Central China,in 2022.The period from May to September was defined as the ozone pollution period,and the other months as non-ozone pollution period.The results showed that:(1)The average TVOCs concentration in non-ozone pollution months(32.1×10^(−9)±13.2×10^(−9))was 65.5%higher than that in ozone pollution months(19.4×10^(−9)±5.9×10^(−9)).However,the concentration of OVOCs in ozone pollution months was 5.3%higher than that in the non-ozone pollution months,indicating that secondary formation may be a significant source of OVOCs in ozone pollution months in Nanyang City.(2)During both observation periods,the OFP of OVOCs accounts for more than 50%,among which formaldehyde(35%),acetaldehyde(10%)and ethylene(9%),m-p-xylene(5%)and toluene(3%)were the most important OFP contributing species.(3)Empirical kinetic model approach(EKMA)and relative incremental reactivity(RIR)calculation revealed that the O_(3) formation sensitivity was in transitional regime during the ozone pollution months,and O_(3) production was sensitive to both anthropogenic VOCs(particularly alkene and aromatic hydrocarbons)and NO_(x).(4)Positive matrix factorization(PMF)analysis identified six sources during the ozone pollution months:gasoline vehicles(29%),solvent use(23%),industrial process emissions(21%),residential emissions(11%),diesel vehicle emissions(10%)and plant emissions(6%).The research shows that during the ozone pollution months,secondary generation was a significant source of OVOCs,while gasoline vehicle emissions were an important contributor to atmospheric VOCs in Nanyang City.