基于隧道测试的机动车VOCs排放特征及源解析

Characteristics and Source Apportionment of Vehicular VOCs Emissions in a Tunnel Study

为探究以乙醇汽油(E10)为主要燃料的机动车尾气源和蒸发源挥发性有机物(VOCs)排放特征,于2019年12月在郑州市北三环隧道内展开了连续两周的VOCs采样,并对隧道内车流特征和环境参数等进行在线监测.首先,利用气相色谱/质谱(GC/MS)法定量出106种VOCs组分,然后采用正交矩阵因子分析(PMF5.0)-化学质量平衡(CMB8.2)复合模型对机动车尾气源和蒸发源VOCs排放的贡献率进行定量解析,最后采用最大增量反应活性(MIR)和气溶胶生成系数(FAC)分别测算了尾气源和蒸发源的臭氧生成潜势(OFP)和二次有机气溶胶生成潜势(SOAFP).结果表明,采样期间隧道环境空气中ρ(VOCs)为(2794.5±147.4)μg·m^(-3),其中卤代烃类的质量分数最高[(32.4±2.0)%],其次为芳烃类[(27.5±0.6)%]和烷烃类[(23.3±0.8)%];基于PMF5.0-CMB8.2复合模型的机动车源VOCs解析结果为:尾气排放(62.5%)>蒸发排放(37.5%);机动车源VOCs排放的OFP贡献率为:尾气排放(71.9%)>蒸发排放(28.1%),SOAFP贡献率为:尾气排放(75.8%)>蒸发排放(24.2%);蒸发源OFP的优势组分有间/对-二乙苯、异戊二烯和反-2-戊烯等,蒸发源SOAFP的优势组分有间/对-二乙苯、间/对-二甲苯和1,2,3-三甲基苯等,尾气源OFP的优势组分有间/对-二甲苯、1,2,4-三甲基苯和1,3,5-三甲基苯等,尾气源SOAFP的优势组分有间/对-二甲苯、间/对-二乙苯和1,3,5-三甲基苯等.建议E10使用区域,在加强机动车尾气排放控制的同时,也应重视蒸发VOCs排放,尤其是其中芳烃类和烯烃类等高活性组分.

To explore the emission characteristics of volatile organic compounds(VOCs)from vehicular exhaust sources and evaporative sources with ethanol gasoline(E10)as the main fuel,VOCs sampling campaigns were carried out in the north third ring tunnel of Zhengzhou city for two consecutive weeks in December 2019.In addition,the characteristics of traffic flow and environmental information were also monitored in the tunnel.Firstly,106 VOCs were quantified using gas chromatography/mass spectrometry(GC/MS),and then source apportionment of VOCs in the tunnel was carried out using a positive matrix factorization(PMF5.0)-chemical mass balance(CMB8.2)composite model.Finally,the ozone formation potential(OFP)and secondary organic aerosol formation potential(SOAFP)of vehicle exhaust sources and evaporative sources were analyzed using the maximum incremental reactivity(MIR)and fractional aerosol coefficient(FAC).The results showed thatρ(VOCs)in the tunnel was(2794.5±147.4)μg·m^(-3) during the experiment,among which halogenated hydrocarbons[(32.4±2.0)%]accounted for the highest proportion,followed by aromatic hydrocarbons[(27.5±0.6)%]and alkanes[(23.3±0.8)%].Source apportionment of vehicular VOCs showed that exhaust emissions(62.5%)>evaporative emissions(37.5%),whereas the contribution of OFP was that exhaust emissions(71.9%)>evaporative emissions(28.1%),and the contribution of SOAFP was that exhaust emissions(75.8%)>evaporative emissions(24.2%).The dominant components of OFP in evaporative sources were m,p-diethylbenzene,isoprene,and trans-2-pentene,whereas m,p-diethylbenzene,m,p-xylene,and 1,2,3-trimethylbenzene were the dominant components of SOAFP.The major components of OFP in exhaust sources were m,p-xylene,1,2,4-trimethylbenzene,and 1,3,5-trimethylbenzene,whereas m,p-xylene,m,p-diethylbenzene,and 1,3,5-trimethylbenzene were the dominant components of SOAFP.In regions where ethanol gasoline is used,special attention should be paid not only to the exhaust emissions control but also to strengthening the emissions reduction of VOCs from vehicle evaporative sources,especially the high active components such as aromatic hydrocarbons and alkenes.