叶蜡单体氢同位素古高程计研究进展

Research Progress of Leaf-wax Hydrogen Isotope Paleoaltimetry

高等植物类脂物广泛分布于土壤、河流和湖泊沉积物中,正构烷烃是植物类脂物的重要组成部分。高等陆生植物叶蜡正构烷烃具有较长的链长(nC_(27)-nC_(33))以及明显的奇偶优势(CPI>5),其氢同位素组成在一定程度上反映了大气降水的同位素特征,对古高程重建具有重要的指示意义。不同地区的现代土壤正构烷烃氢同位素随高程的递减率有所不同,说明地区性的校正是必要的。蒸散富集作用和生物合成作用过程也会影响正构烷烃氢同位素值。在利用长链正构烷烃重建古高程时,需结合古气候、古纬度、古植被等多方面资料综合分析。

Leaf waxes/lipids which are derived from terrestrial higher plants are ubiquitous m fluvial, lake, and marine sediments. N-alkanes are an important component of leaf waxes. Modern leaf wax n-alkanes from terres- trial higher plants are characterized with long chains with 27 to 33 carbon atoms （ nC27-nC31 ） and high carbon pref- erence index （CPI） values （〉5）. The hydrogen isotopes in n-alkanes are determined by meteoric water composi- tions, which makes them a potential proxy in paleoaltimetry studies. The lapse rates at which n-alkane hydrogen i- sotopes in modem soils change with altitude vary in different areas, implying that local calibration has to be conduc- ted. The enrichment due to evapotranspiration and difference in fractionation during biosynthesis also influence n- alkane hydrogen isotopes values. When using long-chain n-alkanes to reconstruct paleoahitude, many factors such as paleoclimate, paleolatitude and paleobotauy should be considered.