低对流层中不同高度大气尘埃类脂质的特征

Characterization of Lipids from Airborne Dusts at Different Heights in Lower Troposphere

低对流层中不同高度大气尘埃的类脂质往往有不同的来源。本文共研究了采自北京325m高气象塔和广州等地在不同垂直高度上的8个大气尘埃样品。用有机溶剂对尘埃样品进行超声抽提,抽提物经硅胶薄层色谱分离和色谱-质谱法分析。结果表明。这些尘埃样品的类脂质主要由正烷烃、正脂肪酸、三萜烷、甾烷和多环芳烃等化合物组成。这些类脂质一般都来自天然生物成因、人为成因和地质成因源,采样高度不同将影响各种输入源有机质的掺和比例。随着采样高度增加,类脂质产率、总烃和脂肪酸产率均下降,尖埃样品中化石燃料残余物和微生物组分减少。有迹象表明在高层大气中输入了长距离搬运的有机质。

The sovent-extractable organic matter (lipids) of eight airborne dust samples at different heights, which were collected at the meteorological tower of Beijing, in the city of Shuicheng and on the outskirts of Guangzhou, using a standard volume air sample, were investigated to determine the distributions of homologous com pounds and molecular markers. All of collected sample filters were ultrasonically extracted in organic solvents. The extracts were esterified and then separated by TLC. Compound molecular structure of the fractions were characterized by GC- MS. These preliminary results show that all samples contain n-alkanes. n-fatty acids, steranes, triterpanes, PAH and so on, derived from both biogenic sources (vascular plant wax and microbial lipids input) and fossil fuel contamination (coal, crude oil, etc.) Some apparent fractionatinon phenomena of lipids in dusts were observed in samlpes from different heights above ground. The upper is the height of dusts, the less is the lipid yield of particles. PAH compounds are mainly present in fine mode particles. The concentrations of PAH , triterpane and sterane will decrease as the sampling height inceasing. Dusts in the upper atmosphere has significantly lower concentrations of anthropogenic and microbial components. The analytical results also indicate that upper airborne dust transport over longer distances.