高等植物、燃煤和机动车排放正构烷烃特征分析

Characteristics of n-alkanes emissions from higher plants,coal ashes and vehicles

采集高等植物、煤烟尘和机动车尾气尘样品,利用GC-MS测定正构烷烃,分析了其源成分谱组成和排放特征.结果表明,高等植物、煤烟尘和机动车尾气尘正构烷烃总含量分别为47.78—305.56μg·g-1、0.35—20.94μg·g-1和3.87—351.06μg·m-3.煤烟尘以低碳数(≤n-C20)为主,高等植物以高碳数(≥n-C25)为主,而机动车尾气尘则介于上述二者之间(n-C20—n-C25);主峰碳对总烷烃浓度贡献率平均为42.99%、14.99%和20.69%,高等植物排放总烷烃中主峰碳贡献率明显高于化石燃料燃烧排放.植物蜡质烷烃组分随环境压力的增大总含量增加;同一纬度地区植物类型是影响平均碳链长度(ACL)的重要因素.家用燃煤排放正构烷烃高于工业排放,但各燃煤灰中烷烃分布特征相似,呈前峰型分布.柴油车尾气尘中总正构烷烃含量是汽油车的90.71倍,天然气尾气尘烷烃排放水平介于二者之间;柴油车尾气以n-C22为主峰碳,呈正态分布,而汽油和天然气车呈后峰型;天然气和柴油车尾气中未分解复杂混合物(UCM)丰度明显高于汽油车.各类源正构烷烃成分谱的建立,可为准确解析环境空气中正构烷烃来源提供基础依据.

Samples of n-alkanes collected from higher plants, coal ashes and vehicle exhausts were determined with GC-MS, and the source composition and distribution characteristics of n-alkanes were analyzed. The sum concentration of n-alkanes was 47. 78-305. 56 μg · g-1 , 0. 35-20.94 μg·g-1 and 3. 87-351. 06 μg·m-3 for higher plants, coal ashes and vehicle exhausts, respectively, with remarkable differences in source composition. For these sources, the predominant n-alkanes were low carbon numbers （≤n-C20 ） , high carbon numbers （≥n-C25 ） and the middle ones （ n-C20-n-C25 ） respectively, showing that the contribution of Cmax from higher plants was significantly higher than the burning of fossil fuels. N-alkanes production rate elevated with the increase in environmental pressures, and vegetation type was a vital factor which affects ACL of plants. Although alkanes level different among the types of conditions of coal combustion, the distribution features were similar. The sequence of alkanes concentration among several fuel type vehicles was as follows：diesel vehicle＆gt; gasoline＆gt; natural gas. A normal distribution of alkanes was detected in diesel waste gas with Cmax at n-C22, while back peak type was found in that of two other types of fuels because of the existence of unfiltered combustion air. The abundance of UCM in samples from natural gas and diesel wastes was higher than that from gasoline. The establishment of＆amp;nbsp;n-alkanes source spectrum and emission characteristics may offer scientific basis for source apportionment and contribution of alkanes in particulate matters.