沉积正构烷烃单体氢同位素定量古降水研究—以海南岛为例

古降水的定量重建是古气候研究的难点。近年来，沉积物中的正构烷烃单体氢同位素广泛应用于古水文环境定性分析，但其与降水量之间的定量关系却鲜有研究。本项工作拟通过海南岛现代河流沉积物和现代水样的系统采集，分析现代海南岛河流沉积物正构烷烃分子氢同位素与降水的定量关系。在综合考虑地形、植被、温度等多种因素的前提下，建立烷烃氢同位素-古降水定量模型。通过在海南晚更新世古河流三角洲沉积物中的应用，以及与附近其他古降水记录的对比，验证该模型在地质历史时期的适用性，并探讨海南岛晚更新世降水量演化特征和可能的驱动机制。本研究的意义在于以现代过程研究为基础，充分挖掘沉积正构烷烃的古降水指示意义，为古降水定量重建提供新的思路。

The quantitative reconstruction of paleo-precipitation is one of the difficulties in paleoclimate investigation. Recently, the sedimentary n-alkane compound-specific hydrogen isotope has been widely used in paleo-hydrological environment studies. But the exact correlation between precipitation amount and n-alkane δ2H is still lacking. This program intends to collect the modern sediments and river water samples on Hainan Island（HI）and investigate the correlation between n-alkane compound-specific isotopes and the precipitation amount. With the consideration of topography, vegetation, and temperature, a quantitative “n-alkane δ2H—precipitation” model would be established. Then the model will be applied to late-Pleistocene Hainan paleo-delta for paleo-precipitation reconstruction. The reconstructed precipitation results will be tested by comparing them to other paleo-precipitation records nearby. Furthermore, the characteristics of HI precipitation and the forcing mechanism during the late Pleistocene are also discussed. This program tries to extract precipitation information from sedimentary n-alkanes as much as possible based on the detailed investigation of modern processes, which would be helpful for quantitatively paleo-precipitation reconstruction.