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为认识低纬度亚热带地区湖泊沉积物中正构烷烃氢同位素组成特征及其与母源输入和生态环境的关系,本文利用气相色谱-高温热转变-同位素比值质谱议(GC-TC-IRMS),对系统采集的抚仙湖沉积物样品中正构烷烃氢同位素进行了测定。抚仙湖沉积正构烷烃δD值分布在-219.3‰~-142.5‰之间,样品中平均值为-208.1‰~-154.5‰,并且奇碳数正构烷烃δD值明显地将样品划分为两种类型。类型Ⅰ样品中正构烷烃平均δD值明显地高于类型Ⅱ样品,反映了它们生物源存在明显差别。沉积物与水生植物和陆生植物中正构烷烃氢同位素组成对比结果指示了沉积C_(17)、C_(21)~C_(25)奇碳数正构烷烃来自水生植物,C_(27)和C_(29)奇碳数正构烷烃主要来自木本植物,C31和C33正构烷烃来自水生和陆生草本植物的混合。对比研究结果表明,湖泊地区生态环境是控制湖泊沉积正构烷烃氢同位素组成的重要因素之一,在利用沉积正构烷烃氢同位素研究古水文学特征时,还要考虑研究区古生态环境对沉积正构烷烃氢同位素的影响,并且结合沉积正构烷烃ACL值和Qw值,才能对沉积有机质中正构烷烃氢同位素组成及变化作出合理的解释。
In order to understand the characteristics of hydrogen isotope composition of n-alkanes and their relationship with maternal input and ecological environment in the sediments of low latitudes and subtropical regions, GC-TC-IRMS (gas chromatography-high temperature thermal transition-isotope ratio mass spectrometry) The n-alkanes hydrogen isotopes in the sediment samples collected from the Fuxian Lake were measured. The δD values of n-alkanes in the sediments of Fuxian Lake ranged from -219.3 ‰ to -142.5 ‰, and the average values in the samples ranged from -208.1 ‰ to -154.5 ‰, and the δD values of odd-numbered n-alkanes markedly divided the samples into two Kind of type The average δD values of n-alkanes in Type Ⅰ samples were significantly higher than those in Type Ⅱ samples, reflecting the significant differences in their biological origins. The comparison of the composition of n-alkanes hydrogen isotopes between sediments and aquatic plants and terrestrial plants indicates that the C_ (17), C_ (21) ~ C_ (25) odd carbons of n-alkanes come from aquatic plants, C_ (27) and C_ (29) The odd-numbered n-alkanes are mainly from woody plants, and the C31 and C33 n-alkanes come from a mixture of aquatic and terrestrial herbs. The comparative study shows that the ecological environment in lakes is one of the important factors controlling the composition of hydrogen isotopes of n-paraffin in lake sediments. When studying the hydrologic characteristics of n-alkanes by sedimentary n-alkanes, N-alkanes hydrogen isotopes, and combined deposition of n-alkanes ACL value and Qw value in the deposition of organic matter normal paraffin hydrogen isotope composition and changes in a reasonable explanation.