基于Py-GC/MS的沙漠湖泊直链脂肪族化合物分析及古气候应用初探

尚文郁; 孙静轶; 谢曼曼; 岑况; 蔡泽; 战楠; 凌媛; 孙青

doi:10.15898/j.cnki.11-2131/td.202201120009

基于Py-GC/MS的沙漠湖泊直链脂肪族化合物分析及古气候应用初探

Py-GC/MS Analysis Method for Aliphatic Biomarker in Desert Lake Sediment and Its Application in Paleoclimatic Study

摘要

摘要: 湖泊沉积物中直链脂肪族化合物(MCCs)对气候变化响应敏感，环境条件的变化可促使MCCs在游离态和结合态间发生转化，是古气候重建的重要生物标志物。以往研究中对样品前处理通常采用混合溶剂提取法得到MCCs游离态组分，而以化学键合、物理吸附等形式赋存的结合态组分无法通过溶剂提取，不能获取结合态组分特征对气候环境变化的指示信息。本文将热裂解这一有机质高效分解技术与气相色谱-质谱(GC-MS)联用，实现了对内蒙古伊和沙日乌苏湖泊沉积物有机质组成的精细刻画，并识别、分析了共计3类、71项结合态MCCs化合物。结果表明：热解温度是影响热裂解-气相色谱-质谱(Py-GC/MS)分析沉积物样品中结合态MCCs分布特征的主要因素，450℃以下热解能量较低导致结合态MCCs解析不充分，550℃和650℃下各类结合态MCCs(含正构烷烃、正构烯烃及α-正构脂肪酮)充分解析，可经GC-MS实现在线分离、识别；随着热解温度升高，裂解产物中MCCs平均链长趋于降低，过高的裂解能量影响了产物中MCCs化合物链长特征对气候变化指示的敏感性。经研究各类MCCs分布特征发现，550℃下正构烷烃平均链长特征与传统气候替代指标游离态正构烷烃单体碳同位素δ¹³C_27~33具有较好的相关性(R=0.83)。结合态正构烷烃ACL_25~31指标响应了区域有效降水变化特征，识别了区域内5.6ka、3.9ka前后的干旱期，反映了东亚夏季风强度变化，对应了北半球中纬度有效降水变化。

Abstract:
BACKGROUND Methylene chain backbone compounds (MCCs) in lake sediments are sensitive to climate change, and changes in environmental conditions could promote the transformation of MCCs lipids between free and bound states, hence providing a series of biomarkers for paleoclimate reconstruction. In previous studies, free MCCs lipids were typically extracted by mixed solvents, bound MCCs lipids with chemical bonding or physical adsorption could not be obtained by organic solvent extraction, and the indicator information of the characteristics of bound components on paleoclimate change was missing.
OBJECTIVES To study the suitable analytical conditions for bound MCCs lipids, and establish proxy based on bound MCCs lipids to provide an effective tool for paleoclimate reconstruction of terrestrial ecosystems.
METHODS Optimized analytical method of pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) was established and used to evaluate the bound MCCs in typical Desert Lake sediment.
RESULTS Total of 71 bound MCCs compounds were identified and analyzed based on fine characterization of organic matter composition in the sediments of the Yiheshariwusu Lake in Inner Mongolia. Pyrolysis temperature was the main factor affecting the distribution characteristics of bound MCCs in sediment. Low pyrolysis energy under 450℃ led to insufficient resolution of bound MCCs. At 550℃ and 650℃, total bound n-alkanes, n-alkenes, and n-alkan-2-ones were on-line separated, identified and analyzed. The average chain length characteristics of bound n-alkanes at 550℃ and the carbon isotope of free n-alkanes as a traditional climate substitute index δ¹³C_27-33 had the best correlation (R=0.83, n=11, p < 0.01).
CONCLUSIONS Proxy ACL₂₅_-₃₁ of bound n-alkanes respond to the change characteristics of regional effective precipitation, identify the drought periods around 5.6ka and 3.9ka in the region, reflect the intensity change of East Asian summer monsoon, and correspond to the change of effective precipitation in the mid-latitude of the northern hemisphere.

HTML全文

参考文献(68)

施引文献

资源附件(0)