Abstract: Isotopic composition of nonmethane hydrocarbons, sampled by Tenax TA adsorption tube and detected by thermal desorption-gas chromatography-isotope ratio mass chromatography was analyzed in the main functional area, Lanzhou. The results show that the average δ¹³C values of transportation related sources is - 28. 7‰, significantly below the value of coal-combustion exhaust( - 24. 1‰) . In summer the average δ¹³C values of atmospheric NMHCs are close to each other( from - 29. 5‰ to - 27.4‰), while in winter the average δC values in Xigu industrial estate(-25.5‰) is larger than that in Panxuanlu(-28.8‰) and Erdianchang(- 31.2‰). The results of source analysis indicate that the atmospheric NMHCs in Panxuanlu are mainly emitted by transportation related sources both in summer and winter; the atmospheric NMHCs in Xigu industrial estate in winter are mainly influenced by coal-combustion exhaust, while in summer n-alkanes and benzene are mainly from transportation related sources; in winter atmosphere in Erdianchang pentane, hexane and benzene are from transportation related sources; in summer atmosphere in residential area the NMHCs are mainly influenced by transportation related sources and some unknown sources; benzene is mainly emitted by transportation related sources and was detected in every sampling site both in winter and summer. To reduce the pollution of NMHCs, it is important to control transportation related sources.

Key words: non-methane hydrocarbons( NMHCs), stable carbon isotope, atmosphere, Lanzhou

摘要： 利用Tenax TA吸附管采集了兰州市污染源和主要功能区冬季及夏季大气样品, 利用热解析-气相色谱-同位素质谱联用仪分析了样品中非甲烷烃的稳定碳同位素组成。结果表明: 不同源排放的 NMHCs 的稳定碳同位素组成不同, 交通相关源中NMHCs的δC平均值为 - 28. 7‰, 显著低于燃煤烟气(-24.1‰); 夏季各功能区NMHCs 的δ¹³C值相差不大, 平均值在 - 29. 5‰ ～- 27. 4‰之间, 冬季西固工业区的 δ¹³C平均值(-25. 5‰)大于盘旋路(-28. 8‰) 和二电厂(-31. 2‰)。同位素来源分析结果显示: 盘旋路冬夏两季 NMHCs主要来源于交通相关源; 西固工业区冬季 NMHCs 主要来源于燃煤烟气, 夏季正烷烃和苯主要来源于交通相关源;二电厂冬季正戊烷、正己烷和苯等主要来源于交通相关源; 居民区夏季 NMHCs 则受到交通相关源排放的影响较大, 其他未知源也有贡献。冬夏两季大气中均检测出苯的存在, 且主要来源于交通相关源, 因此控制交通相关源的排放是降低致癌物质苯污染的关键。

关键词: 非甲烷烃, 稳定碳同位素, 大气, 兰州市