青藏高原湖泊表层沉积物中陆源正构烷烃氢同位素比值的气候意义  

Climatic implication of hydrogen isotope ratios of terrigenous n-alkanes in lacustrine surface sediment of the Tibetan Plateau

作　　者：夏忠欢[1,2] 徐柏青[1] Mugler I. 邬光剑[1] Gleixner G. Sachse D. 朱立平[1] 

机构地区：[1]中国科学院青藏高原研究所青藏高原地表环境与过程实验室,北京100085 [2]中国科学院研究生院,北京100049 [3]Max-Planck-lnstitut fur Biogeochemistry, Postfach 100164, D-07701 Jena, Germany

出　　处：《湖泊科学》2008年第6期695-704,共10页Journal of Lake Sciences

基　　金：国家重点基础研究发展规划项目(973计划)(2005CB422004);国家自然科学基金创新群体项目(40121101)联合资助

摘　　要：选取青藏高原南北断面气候环境条件差异明显的大枪勇错、空姆错、纳木错、克鲁克湖和小柴达木湖的表层沉积物进行了陆源正构烷烃(C25-C31)的提取分析.通过将这些生物标志物δD值与源区生长季节大气降水δD值进行比较,发现两者有很好的相关性,说明陆源沉积正构烷烃记录了生长季节降水同位素信号.正构烷烃n-C25、n-C27与大气降水间氢同位素分馏在-45‰至-70‰之间,而n-C29、n-C31与大气降水间氢同位素分馏在-70‰至-95‰之间,沿青藏高原南北断面分馏恒定,分馏平均值分别是-57‰和-82‰.通过对比欧洲断面的-130‰分馏值,可以看出青藏高原南北断面陆源沉积正构烷烃与大气降水间表观同位素分馏小很多.δD values of terrigenous n-alkanes （n-C25, n-C27, n-C29 and n-C31） extracted from recent lake surface sediments of Lake Qiangyong Glacier, Lake Kougmu Co, Lake Nam Co, Lake Keluke and Lake Xiao Qaidam along the S-N transect of Tibetan Plateau are compared to those of precipitation spanning a wide range from -167‰ to -51‰ and clearly correlate with δD values of meteoric water during the growth, indicating that terrigenous n-alkanes record the precipitation signal during the growth. The isotopic fractionation between precipitation and alkanes of n-C25 and n-C27 cover a range from -45‰ to -70‰ whilst that between precipitation and alkanes of n-C29 and n-C31 vary from -70‰ to -95‰, both being fairly constant along the S-N Tibetan transect with the mean at -57‰ and -82‰, respectively. By comparison with the apparent isotope fractionation of -130‰ along the S-N European transect, it implies that the apparent hydrogen isotopic fractionation between meteoric water and terrestrial n-alkanes along the Tibetan transect is much smaller.

关 键 词：正构烷烃 湖泊沉积 氢同位素比值 降水 气候 青藏高原 

分 类 号：P532[天文地球—古生物学与地层学]