长沙大气中VOCs研究

应用大气采样罐采样技术和色谱-质谱联用（GC-MS）技术,对2008年长沙市大气中76种挥发性有机物（VOCs）的组分及其质量浓度水平进行测试,比较了各组分对臭氧产生的影响潜势,同时对其主要来源进行简单分析.结果表明,长沙大气总VOCs在上午和下午的浓度分别是38.4×10-9（体积分数）和22.7×10-9（体积分数）,下午大气中VOCs浓度显著低于上午;季节变化呈现VOCs冬季浓度远高于夏季VOCs浓度,组分中以卤代烃最高,烷烃、芳烃次之,烯烃最低,OH消耗速率最高的物质是间、对二甲苯（10.71×10-9 C,碳单位体积比,下同）;其次为1,2,4-三甲苯（6.04×10-9 C）和1,3,5-三甲苯（2.23×10-9 C）.芳烃对大气O3生成贡献最大（66%）,其次是烯烃（26%）,烷烃最低（8%）.高浓度的异戊烷和丙烷说明了机动车排放和液化石油气是VOCs来源之一,苯/甲苯的特征比值接近0.8,远高于机动车尾气排放特征比值0.5;说明溶剂和涂料挥发是其主要来源之一.

Observation and Study on Atmospheric VOCs in Changsha City

Volatile organic compounds (VOCs) are one of the key precursors of atmospheric ozone(O₃),which also contribute to the production of SOA. During 2008, VOCs were measured near Changsha City. Weekly integrated canister samples were collected and analyzed in the morning and afternoon of each Tuesday. Simultaneously, concentration, potential ozone production and sources of VOCs in the atmosphere of Changsha were studied. The results indicated that the total VOCs species had higher concentrations in the morning (38.4×10^-9),and lower in the afternoon (22.7×10^-9),where the concentration of halo carbon was the highest, and alkanes, aromatics and alkenes came next. The m/p-xylene had the highest OH reactivity concentration (10.71×10^-9 C), 1,2,4-trimethylbenzene(6.04×10^-9 C) and 1,3,5-trimethylbenzene (2.23×10^-9 C) came next. Aromatics (66%) had the most significant contribution to the production of O₃ in the atmospheric VOCs of Changsha, and alkenes (26%) and alkanes (8%) came next. The highest concentrations of propane and isopentane indicated vehicular exhaust and liquefied petroleum gas (LPG) appear to be the main source of VOCs in Changsha City. Benzene/toluene ratio was higher than 0.5 which was close to 0.8, showing solvent volatilization was also a main source of VOCs.