风成沉积物叶蜡氢同位素在揭示东亚季风区干湿变化中的原理及应用

沉积物叶蜡正构烷烃氢同位素是指示气候和环境变化的一种新的生物地球化学指标,由于其存在广泛、成因机制清晰、易于保存等特点,被认为是具有很大潜力的重建古环境的替代指标。分析了正构烷烃的形成过程与其氢同位素的分馏机制,讨论了叶蜡正构烷烃氢同位素在不同气候区指示湿度变化的能力,总结了在东亚季风区半干旱区的一些应用案例。相比于风成黄土中其他气候代用指标,沉积物正构烷烃氢同位素更直接地指示了区域干湿变化,对区域气候和环境变化响应敏感,在长时间尺度上记录了水汽变化过程,并存在显著的太阳辐射岁差周期。正构烷烃氢同位素是一种理想的东亚季风区干旱半干旱地区湿度重建的代用指标,未来需要进一步研究大气降水同位素和本地分馏过程对其变化的控制规律,加强其在古气候定量重建中的研究应用。

The Application of Leaf Wax n-alkanes δD in Aeolian Sediments as a Proxy for Reconstructing Quaternary Humidity Variations in the Monsoonal East Asia

Leaf wax n-alkanes are widely distributed in sediments;they have a clear formation process,and they are resistance to environment change.δD composition of leaf wax n-alkanes is a newly developed biogeochemistry proxy with great potential in paleoenvironment reconstruction.In this paper,we reviewed the formation process of leaf wax n-alkanes and their hydrogen isotopic fraction,evaluated the relationship between leaf wax n-alkanes δD and regional humidity,and summarized recent applications of them to paleoclimate reconstruction.Based on the studies of n-alkanes δD of surface sediments,we find n-alkanes δD is a good proxy indicator of humidity in semiarid and arid climate region in monsoonal East Asia.Compared with other proxies from loess-paleosol sequences,the n-alkanes δD is a direct indicator of humidity variations;it shows direct response to environment change,and it reveals precession signal of solar insolation variations in orbital timescales paleoclimate record.In this case,the n-alkanes δD is a good proxy for humidity variations in sedimentary records in East Asia monsoon region,and,further research on the influence of the variations of precipitation isotope and local isotope fraction process to the n-alkanes δD is compulsively needed.