东北镜泊湖近2000以年来正构烷烃单体氢同位素记录与古气候重建

In recent years, hydrogen isotopic compositions (δD) of sedimentary n-alkane are increasingly used as a tool to reconstruction paleoclimate and paleohydrological over various geological timescales, because they record the isotope signal of the source water. However, at mid-latitudes, greater variability in moisture sources and transport pathways often lead to a more complex forcing of δD of sedimentary n-alkane. The primary aim of this study is focuses on the present process of the modern lake catchment system study, to understanding the potential value of δD of sedimentary n-alkane as a hydrological and climatic proxy at the Jingpo Lake, Northeastern China. We want to identify the biological origin for sedimentary n-alkanes as well as the source water used for biosynthesis and highlight the influencing factors on the δD values of sedimentary n-alkanes. Then, reconstruct high-resolution records of paleoclimate change of the past 2000 years by δD of n-alkanes, understanding the history of variations in climate and investigated the influence factors and underlying dynamics mechanisms from decade to century scale, and provide insights into future variability of climate and its impact on water resources and agriculture in NE China.

湖泊沉积正构烷烃单体氢同位素能够记录环境水同位素特征，近年来逐渐被应用于不同时间尺度的古气候和古水文研究中。但是中纬度地区由于水汽来源复杂和传输路径多样，导致正构烷烃单体氢同位素的影响因素较为复杂。本项目的主要研究目的是通过系统的现代过程研究，探讨我国东北镜泊湖影响正构烷烃氢同位素作为古气候代用指标的影响因素，了解湖泊沉积物正构烷烃的生物来源，认识用于生物合成的源水氢同位素影响因素及其对湖泊沉积中正构烷烃氢同位素的影响，继而重建过去2000年研究区高分辨率古气候演化序列，理解研究区的古气候和古水文在十年到百年尺度上的影响因素和动力学机制，为预测未来东亚季风变化趋势及其对我国东北地区水资源和农业的影响提供科学依据。

我国东北地区降水收到东亚季风的影响，但是百年尺度的古季风记录较少。湖泊沉积正构烷烃单体氢同位素具有定量重建古气候的应用前景，但是其成因特征和影响因素是迫切需要解决的关键科学问题。本项目提供对东北镜泊湖及其流域各类生物样品和沉积物样品中正构烷烃生物标志化合物单体氢同位素进行了分析，研究了中高纬度气候带地区淡水湖泊沉积环境中生物和湖泊沉积物的正构烷烃单体氢同位素组成特征，研究其有机质来源，讨论水源氢同位素组成、环境因子、沉积环境、生物合成过程等生物地球化学作用对正构烷烃单体氢同位素组成的影响，通过长链正构烷烃单体氢同位素值建立了镜泊湖地区过去近2000年的古降水演化历史，进一步比较表明，中国东北地区的降水量可能与赤道太平洋的西向东热梯度有关。此外，水汽源区的温度对中国季风降水的同位素组成也有重要影响。本研究为利用湖泊沉积正构烷烃单体氢同位素的应用研究提供了科学数据和依据。