兰州市大气降尘中正构烷烃的分布特征及源解析

采集了2005年春季兰州市不同功能区大气降尘样品,采用气相色谱/质谱法测定样品中的正构烷烃。结果表明,降尘中正构烷烃主要有2种类型,一种是后峰型,以C29为主峰碳,大于C25正构烷烃具有明显的奇偶优势,碳优势指数(CPI)为1.25~1.40;另一种是双峰型,分别以C29,C20,C19,C15为主峰碳,在C25或C27后有明显的奇碳数优势,CPI为1.26~2.35。研究区内不同区域降尘中正构烷烃分布有明显的变化,相对清洁区正构烷烃分布为后峰型,主要来源于燃煤、高等植物的不完全燃烧。工业区、商业区、商业居民混合区正构烷烃分布属于双峰型,既有高等植物蜡的输入,也有汽车尾气、石油化工的输入,且人为源的贡献较大。

Distribution Characteristicsand Source Apportionmentof n -Alkanesin DustfallatLanzhou

Organic analyses of alkane in dustfall samples of spring after the heating period in Lanzhou were carried out by GC/MS.The results showed that n-alkanes homologs（mainly C12～C33） were identified in all compounds.Various parameters such as distribution of carbon number,carbon number with peak value of content,and carbon predominance index（CPI） were calculated.Alkane spectrum indicated that there were two types of n-alkanes： one had single dominant peak of C29 with the CPI values ranging from 1.25 to 1.40;the other has two peaks with the CPI values ranging from 1.26 to 2.35.It was concluded that the vehicle exhaust and combustion of fossil fuel mainly contributed to the pollution in Lanzhou by using different molecular geochemical parameters.