基于质子转移反应飞行时间质谱走航分析的鲁南某城市初夏大气VOCs污染特征及对二次污染生成的贡献分析

Characteristics of Atmospheric Volatile Organic Compounds and Its Contribution to Secondary Pollution in Early Summer in a City in Southern Shandong Province Based on a Cruise Monitoring Campaign with PTR-ToF-MS

为探究鲁南地区大气中VOCs污染情况及二次生成转化特征,采用PTR-ToF-MS(质子转移反应飞行时间质谱仪)对鲁南某城市下辖6个行政区初夏(2021年5月19—27日)大气中挥发性有机物(VOCs)进行走航观测,研究该城市不同区域的VOCs浓度水平、组成特征以及对臭氧和SOA的生成贡献.结果表明:①该市大气VOCs平均浓度为190.96μg/m^(3),主要由含氧化合物、烃类、卤代烃、苯系物和含硫化合物组成,其中对VOCs组成贡献最大的物种包括乙酸乙烯酯、丙醛、环己酮、戊烯等.②含氧化合物和烃类是该城市(除A区外)最主要的臭氧前体有机物,对OFP的贡献率分别达50%和40%.③除甲苯是C区SOAFP(二次有机气溶胶生成潜势)贡献最大的VOCs物种外,二甲苯是其他各区SOAFP贡献最大的VOCs物种,贡献率在30%以上.④因存在较多大型化工企业,A区与其他区大气VOCs组成差异较大,乙酸乙烯酯和二甲苯是其VOCs主要组分,苯系物、含氧有机物、卤代烃和烃类等四类物种OFP贡献相当,均约占25%;A区大气中VOCs的SOAFP较高,约是其他区的1.5~2.0倍.⑤通过特征物种比值及走航观测分析发现,A区大气VOCs主要来源于溶剂挥发及燃烧过程,C区VOCs主要源于交通,其他区VOCs主要源于燃烧及工业生产过程;同时,食物加工过程(如油烟)排放也是该市大气VOCs的重要来源.研究显示,降低大气中含氧有机物、烃类、苯系物浓度是控制该市大气臭氧、二次有机气溶胶生成的有效途径.

In order to explore the pollution of VOCs and the characteristics of secondary generation and transformation in the atmosphere of southern Shandong Province,a Proton Transfer Reaction Time-of-Flight Mass Spectrometer(PTR-ToF-MS)was used to monitor the volatile organic compounds(VOCs)in the early summer atmosphere of six districts in a southern city of Shandong Province during May 19th-27th,2021.The mass concentration,chemical composition,and contribution to the formation potential of ozone and secondary organic aerosols were investigated.The results showed that:(1)The average mass concentration of atmospheric VOCs in this city is 190.96μg/m^(3),which are mainly composed of oxygen-containing compounds,hydrocarbons,halogenated hydrocarbons,benzene series and sulfur-containing compounds.The species with higher mass percentages are vinyl acetate,propionaldehyde,cyclohexanone,and pentene.(2)Oxygen-containing compounds and hydrocarbons are the most important ozone precursor gases here(except District A),and their contribution to ozone formation potential(OFP)is 50%and 40%,respectively.(3)Except toluene contributes the most to the formation potential of secondary organic aerosols in District C,xylene contributes the greatest potential to secondary organic aerosol formation(SOAFP)in other districts,and contributes more than 30%of the total SOAFP in each district.(4)Because there are many large chemical companies,the VOCs compositions in District A are quite different from those in other districts.Vinyl acetate and xylene are the main VOCs components,benzene series,oxygenated organics,halogenated hydrocarbons and hydrocarbons contribute equally to OFP of 25%separately.VOCs in District A have a higher SOAFP,which is about 1.5-2.0 times of those in other districts.(5)Through the specific species ratio,cruise monitoring and analysis,the VOCs in District A mainly come from solvent evaporation and combustion processes,the VOCs in District C mainly come from traffic,and the VOCs in other districts mainly come from combustion and industrial production processes;Food processing(such as oil fume)is also an important source.This study shows that reducing the concentration of oxygen-containing organics,hydrocarbons,and benzene series in the atmosphere is an effective way to control the generation of atmospheric ozone and secondary organic aerosols in cities.