成都双流夏秋季环境空气中VOCs污染特征

为了解成都市大气污染重点防治区域——双流地区的环境大气中挥发性有机物(VOCs)的污染特征和来源,2016年8月30日~2016年10月7日,VOCs外场观测在成都市双流区展开.结果表明,在线观测期间,采样站点总的大气挥发性有机物(TVOCs)的平均体积分数为(45. 15±43. 74)×10-9,其中烷烃的贡献最大(29%),其次是芳香烃(22%)、卤代烃(17%)、含氧挥发性有机物(OVOCs,15%)、烯烃(9%)、乙炔(7%)、乙腈(1%);优势物种为丙酮、二氯甲烷、乙炔、乙烯、苯、甲苯、间/对-二甲苯、丙烷、1,2-二氯乙烷以及丁酮.通过比较VOCs的化学反应消耗速率发现,反应活性最大的为芳香烃,其次是烯烃;反应活性最强的物种为苯乙烯、间/对-二甲苯、异戊二烯、乙烯等.整个观测期间,有两次明显的生物质燃烧活动.国庆假日期间,TVOCs浓度相比之前明显上升,平均体积分数达57. 65×10-9,其中,短链烯烃、卤代烃以及OVOCs浓度上升最为显著.分析某些关键的非甲烷总烃(NMHCs)和OVOCs的日变化特征发现,其变化规律反映了双流地区不同源排放特点.双流区环境空气中VOCs受本地工业源排放影响较大.

Characteristics of Ambient VOCs at the Shuangliu Site in Chengdu, China, During Summer and Autumn

To better understand the characteristics and sources of ambient volatile organic compounds (VOCs) in a polluted area in Chengdu, which requires air pollution control, samples were collected hourly at the Shuangliu site from August 2016 to December 2016. Online gas chromatography/mass spectrometry and a flame ionization detector (GC/MS-FID) were used to analyze the mixing ratios and compositions of the VOCs. During the sampling period, the average mixing ratios of the VOCs were (45.15±43.74)×10^-9. Alkanes contribute the most to the total volatile organic compounds (TVOCs), followed by aromatics (22%), halocarbon (17%), oxygenated volatile organic compounds (OVOCs; 15%), alkenes (9%), acetylene (7%), and acetonitrile (1%). Acetone, dichloromethane, acetylenes, ethylene, toluene, m/p-xylenes, propane, 1,2-dichloroethane, and methyl ethyl ketone are the dominant species. By calculating the OH loss rate, the chemical reactivity of the VOCs was estimated. Aromatics contribute the most to the total VOC reactivity, followed by alkenes. The most reactive species are styrene, m/p-xylenes, isoprene, and ethylene. Two biomass burning events were detected during the sampling period. The average mixing ratio of TVOCs is 57.65×10^-9, which significantly increased during the national holiday. The mixing ratios of several C2-C5 alkenes, halocarbons, and OVOCs increased the most during the national holiday. The diurnal patterns of critical non-methane hydrocarbons (NMHCs) and OVOCs are consistent with the emission sources in this area. The VOC characteristics at the sampling site are mainly influenced by local industrial sources.