大气挥发性有机物的日变化特征及在臭氧生成中的作用--以广州夏季为例

The diurnal variation of ambient VOCs and their role in ozone formation:case study in summer in Guangzhou

为了得到实时的大气挥发性有机物(VOCs)浓度组成和日变化特征,2006年夏季在广州市区内高约55m的楼顶采用在线的气相色谱仪进行了为期一个月的观测.结果表明,影响城市VOC含量的物种以及对臭氧生成有重要贡献的典型物种的日变化存在不同的特征.烷烃类和烯烃类物种出现早晚高峰值,估计主要与机动车排放有关,芳香烃除了与交通排放有关,还受到溶剂挥发的影响,早晨的峰值晚于交通高峰时间.异戊二烯在正午时间出现一天的单峰值,主要来自于天然源排放.乙苯和间对二甲苯的比值被用来表征采样点上气团光化学反应的进程,通常情况下,广州市区点气团经历的光化学进程越久,臭氧浓度越高.

In order to obtain the chemical speciation and diurnal pattern of ambient volatile organic compounds （VOCs）, a continuous half hour measurement was performed on top of a 55 meter tall building in Guangzhou in July, 2006, using a set of automated gas chromatography instruments. The various VOC species showed different diurnal variations. Alkanes and alkenes had two peaks in the morning and evening, corresponding to the local traffic rush hours, indicating these species were mainly due to vehicular emissions. The morning peaks of aromatics appeared later than traffic rush hour, suggesting that the concentrations of aromatics was affected by both traffic emissions and solvent evaporation. The peak of isoprene appeared around noon, showing that the major sources of isoprene were biogenic emissions. In this work, the ratios of ethylbenzene to m,p-xylene were used as an indicator for photochemical processing. And the measured results showed that the ratios of ethylbenzene to m,p-xylene had close correlation with the ground-level ozone concentrations.