深圳大气VOCs浓度的变化特征与化学反应活性

Variation characteristics and chemical reactivity of ambient VOCs in Shenzhen

对深圳2010年4个季节大气中VOCs进行了监测,研究了VOCs组分、季节变化和日变化特征.结果表明,烷烃是大气中含量最丰富的VOCs物种,占总VOCs的50%以上,其他依次是芳香烃和烯烃.总VOCs浓度季节变化表现为冬季最高和夏季最低,日变化特征则表现为夜晚浓度高、白天浓度低,峰值出现在早晨7:00左右,最低值则出现在下午14:00.通过VOCs物种间的比值特征分析了部分物种的来源,结果显示,反式-2-丁烯和顺式-2-丁烯主要来源于机动车尾气,甲苯和正己烷则受到了溶剂挥发的影响.利用最大增量反应活性(MIR)计算了各类VOCs的臭氧生成潜势(OFP),大气各类VOCs的OFP芳香烃最高、其次为烯烃,烷烃最低,甲苯、间,对-二甲苯和乙烯对臭氧生成的贡献在VOCs物种中排名前3.

The concentrations of ambient volatile organic compounds were monitored during the four seasons in 2010 in Shenzhen.The chemical speciation,seasonal variation and diurnal pattern were obtained.Alkanes were the most abundant compound class,accounting for more than 50% of the total VOCs,followed by aromatics and alkenes.The seasonal variation of total VOCs indicated that maximum values occurred in winter while the minimum values occurred in summer.The diurnal pattern showed higher concentrations at night while lower concentrations in the daytime,with the peak value appearing at bout 7：00 in the moring and the minimum value appearing at about 14：00 in the afternoon.The responsible sources of VOCs were analyzed by using the characteristic ratio of some VOCs species.The results showed trans-2-butene and cis-2-butene mainly came from vehicle exhaust,while toluene and n-hexane were influenced strongly by solvent evaporation.The method of maximum incremental reaction（MIR） was used to calculate ozone formation potential（OFP） of various VOCs.It showed that the OFP of aromatics were the largest among all kinds of VOCs,followed by alkenes and alkanes.Toluene,m/p-xylene and ethane ranked the three largest species in the terms of the contribution to ozone formation.