2019进博会期间上海大气挥发性有机物污染特征和来源解析

Characteristics and Source Analysis of Atmospheric Volatile Organic Compounds in Shanghai During the 2019 CIIE

大气挥发性有机化合物(VOCs)是臭氧和二次有机气溶胶的前体物。本文采用5800-GM型挥发性有机物气相色谱质谱联用在线监测系统分析了2019年第二届中国国际进口博览会期间上海大气VOCs浓度和分布。在非管控期VOCs污染水平从高到低依次为烷烃(31.1%)>卤代烃(25.9%)>含氧VOCs(21.9%)>芳烃(11.4%)>烯烃(9.7%),管控期VOCs浓度序列为烷烃、卤代烃(各32.4%)>含氧VOCs(18.7%)>烯烃(8.5%)>芳烃(8.0%),表明针对芳烃污染源的管控最有成效。烯烃和芳烃是臭氧的关键前体物,对臭氧生成潜势的贡献超过50%。PMF源解析认定了5个主要污染源,即:机动车尾气、溶剂使用、植物排放、油气挥发和工业过程。进博会管控前,机动车尾气和工业源对上海大气VOCs的贡献分别为33.6%和32.8%。与工业过程排放明显降低不同,管控期机动车尾气的相对贡献不降反升。以上结果表明,消减机动车和工业源排放是未来VOCs污染治理的重点。

Atmospheric volatile organic compounds(VOCs) are precursors of ozone and secondary organic aerosols. In this study, the 5800-GM gas chromatography-mass spectrometry system for online monitoring VOCs was used to analyze the concentration and distribution of atmospheric VOCs in Shanghai during the 2019 China International Import Expo(CIIE). During the non-control period, the VOCs pollution levels were alkanes(31.1%)>halogenated VOCs(25.9%)>oxygenated VOCs(21.9%)>aromatics(11.4%)>alkenes(9.7%). The sequence of VOCs during the control period was alkanes=halogenated VOCs(32.4%)>oxygenated VOCs(18.7%)>alkenes(8.5%)>aromatics(8.0%), indicating that the control of aromatic emissions was the most effective way. Alkenes and aromatics were key precursors of ozone, contributing more than 50% to the ozone formation potentials. Five major pollution sources were identified by PMF model, namely: vehicle exhaust, solvent use, plant emissions, fuel evaporation and industrial process. Before the control of the CIIE, the contributions of vehicle exhaust and industrial process to the urban VOCs were 33.6% and 32.8%, respectively. In contrast to the obvious reduction in industrial emissions, the relative contribution of vehicle exhaust increased during the control period. Our results indicate that the reduction of vehicle exhaust and industrial emissions is the key to mitigating VOCs pollution in future.