北京市城区春季大气挥发性有机物污染特征

Pollution Characterizations of Atmospheric Volatile Organic Compounds in Spring of Beijing Urban Area

"2+26"城市联防联控措施的实施及北京市产业结构的调整,使得北京市大气中VOCs(volatile organic compounds,挥发性有机物)质量浓度、组成特征及来源发生了变化.运用AirmoVOC(GC-866)在线自动监测仪对2017年3-5月北京市城区大气中的VOCs进行观测.结果表明:①北京市城区春季大气中ρ(TVOCs)(TVOCs为总挥发性有机物)为34.36μg/m^3,ρ(烷烃)、ρ(芳香烃)、ρ(烯烃)、ρ(炔烃)分别占ρ(TVOCs)的57.13%、33.18%、7.54%、2.15%.质量浓度最高的前3位VOCs物种分别为苯、丙烷和乙烷,其质量浓度分别为5.97、3.51、2.63μg/m^3.②ρ(TVOCs)的日变化有3个较明显的峰值,分别出现在05:00、11:00和23:00,ρ(TVOCs)最低值出现在18:00,并且夜间ρ(TVOCs)高于白天.VOCs日变化特征表明,北京市VOCs污染受凌晨时段柴油车尾气排放和早晚交通高峰期汽油车尾气排放的影响较为明显.③春季VOCs的OFP(ozone formation potential,臭氧生成潜势)分析表明,芳香烃对OFP的贡献率(44.22%)最大,其次是烯烃(31.06%),最后是烷烃(23.86%);北京市VOCs污染的关键活性组分是丙烯、正丁烷、环戊烷、苯、甲苯、二甲苯.④PMF(正矩阵因子分析法)分析表明,溶剂使用源是北京市春季大气中VOCs最主要的排放源,对TVOCs的贡献率为39.06%,其次是移动源(33.79%)和油气挥发源(17.85%),燃烧源的贡献率(9.30%)最低.研究显示,控制移动源、溶剂使用源和燃烧源的排放是控制北京市环境空气中VOCs污染的关键.

The mass concentration,composition and sources of volatile organic compounds(VOCs)in the atmosphere of Beijing have been changed in recent years due to the implementation of the'2+26'urban joint prevention and control measures and adjustment of Beijing's industrial structure.Therefore,hourly observations of atmospheric VOCs were performed by the Airmo VOC(GC-866)on-line automatic monitor system from March to May 2017 in the Beijing area.The results showed thatρ(TVOCs)was 34.36μg/m^3 in spring in Beijing.ρ(alkanes),ρ(aromatics),ρ(alkenes)andρ(alkyne)accounted for 57.13%,33.18%,7.54%and 2.15%of the TVOCs mass concentrations,respectively.The top three VOCs species with the highest mass concentration were benzene,propane and ethane,with mass concentrations of 5.97,3.51 and 2.63μg/m^3,respectively.The diurnal variation of total VOCs had three relatively obvious peaks,which appeared at 05:00,11:00 and 23:00,respectively.And the lowest value ofρ(TVOCs)appeared at 18:00.Theρ(TVOCs)was higher at night than during the day.The diurnal variation characteristics of VOCs indicated that the VOCs pollution was significantly affected by diesel vehicle emissions in the early morning and gasoline vehicle emissions in the morning and evening rush hours.The analysis of the OFP(ozone formation potential)of VOCs in spring showed that the relative contribution rate of aromatics was the largest(44.22%),followed by alkenes(31.06%)and alkanes(23.86%);and the key active components were propene,xylenes,toluene,benzene,cyclopentane,and n-butane.Sources analysis by PMF(positive matrix factorization)model showed that the solvent usage sources was the most important emission source of VOCs in Beijing in spring,contributing 39.06%to the TVOCs,followed by mobile sources(33.79%)and gasoline evaporation sources(17.85%).And combustion sources(9.30%)contributed the least.The research shows that the key to control VOCs pollution in Beijing is to control the emission of mobile sources,solvent usage sources and combustion sources.