2015年北京大气VOCs时空分布及反应活性特征

2015年在北京市城区东四、东南边界点永乐店、以及背景点定陵进行了全年连续VOCs监测，其中市区的大气VOCs年均摩尔分数为（48.93±31.03）×10^-9，东南边界的年均摩尔分数为（54.55±39.64）×10^-9，背景点定陵年均摩尔分数为（28.25±21.26）×10^-9.组分中烷烃占比最高，之后依次是含氧VOCs，烯烃、芳香烃、卤代烃和乙炔等物质.VOCs浓度整体呈现冬天高，夏天低，夜间高，白天低的特点.城区乙炔在春、夏、秋季浓度较高，冬季东南边界点乙炔浓度较高.在人为源干扰较小的背景点，含氧VOCs每天的中午以及每年的夏天阳光充足时浓度较高.VOCs中年均摩尔分数较高的物种主要是乙烷、乙炔、乙烯、乙醛、丙烷、丙酮、正丁烷、二氯甲烷等低碳物质.高碳物质中苯和甲苯年均摩尔分数相对较高.从甲苯/苯比值发现北京VOCs除交通源外受到其他多种源的共同影响.而乙烷/乙炔比值发现北京受到气团老化影响较严重，尤其东南边界受到周边老化气团传输的影响较大.从异戊烷占总VOCs比例变化上发现夏季高温使汽油挥发情况比其他季节严重.从活性上分析，东南边界的臭氧生成潜势最高，市区其次，定陵较低.对臭氧生成潜势贡献较大的物种是乙烯、丙烯、乙醛、间/对-二甲苯和甲苯，而摩尔分数较高的烷烃对臭氧生成潜势贡献不大.

Temporal Variation, Spatial Distribution, and Reactivity Characteristics of Air VOCs in Beijing 2015

In 2015, continuous volatile organic compound (VOC) monitoring was conducted for Dongsi (urban site), the southeast boundary site Yongledian, and Dingling (background site). The average annual mole fraction of atmospheric VOCs in urban areas was(48.93±31.03)×10^-9, the average annual mole fraction of the southeast boundary was (54.55±39.64)×10^-9, and the average annual mole fraction for the background site was(28.25±21.26)×10^-9. Considering VOC components, alkanes occupy the highest proportion, followed by oxygen-containing VOCs, olefins, aromatic hydrocarbons, halogenated hydrocarbons, and acetylene. VOC concentration was higher in winter, lower in summer, higher at night and lower in the daytime. The concentration of acetylene in urban areas was higher in spring, summer and autumn, but higher in winter at the southeast boundary site. However, in the background, a small amount of direct anthropogenic interference was detectable, with the concentration of oxygen VOCs higher at noon and in summer. The species with high mole fractions in the VOCs were identified as mainly ethane, acetylene, ethylene, acetaldehyde, propane, acetone, n-butane, dichloromethane, and other low-carbon substances. The concentrations of benzene and toluene in the high-carbon group was relatively high. From the toluene/benzene ratio, it was found that Beijing VOCs were influenced by many sources other than transportation. However, the ratio of ethane/acetylene has been found to be significantly dependent on the aging of air mass in Beijing, with the southeast boundary particularly affected by movement of the aging air mass. Changes in the ratio of isopentane/TVOC showed that high summer temperature enhanced gasoline volatilization. The southeastern boundary point of OFP was the highest, followed by the urban area, with Dingling lower. The species with greater contribution to OFP were ethylene, propylene, acetaldehyde, paraxylene and toluene, with the higher mole fraction of alkanes making little contribution to OFP.