不同纬度地区植物中正构烷烃及其同位素组成  

Compositions of n-Alkanes and Their Isotopes in Plants from the Different Latitude Regions in China

作　　者：段毅[1] 吴保祥[1] 徐丽[1] 张晓莉[1] 何金先[1] 

机构地区：[1]中国科学院地质与地球物理研究所油气资源研究重点实验室,兰州730000

出　　处：《地质学报》2011年第2期262-271,共10页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40772069和40872092);国家"973"项目(编号2005CB422105)资助成果

摘　　要：本文应用GC-MS和GC-TC-IRMS同位素分析技术,对我国北部柴达木盆地花土沟至南部广西南宁5个地区草、芦苇和树叶3类植物中正构烷烃及其碳氢同位素进行了分析。结果显示了不同纬度地区植物中正构烷烃碳数分布在C15～C35之间,呈单峰型分布,主峰碳数为C27、C29和C31;CPI值分布在3.49～17.25之间,平均值是草<芦苇<树叶;ACL值为26.24～30.26,平均值是草>芦苇>树叶。研究发现,随着植物生长地区纬度的增高和年平均气温的降低,植物中正构烷烃主峰碳数、CPI值、ACL值都降低,并且纬度每增加1°,草、芦苇和树叶中ACL值分别减少0.08、0.22和0.36;气温每增加1℃,草、芦苇和树叶中ACL值分别增加0.04、0.24和0.20。研究样品中C27和C29正构烷烃的δ13C值分布在-25.3‰～-35.5‰之间,草具有相对轻的碳同位素组成;C27和C29正构烷烃碳同位素组成与环境因子(如纬度和温度)之间的相关性,在这次研究中没有观察到。样品中C27和C29正构烷烃δD值分布在-132.1‰～-192.6‰之间,草具有相对轻的氢同位素组成。随着纬度增加和气温降低,草和树叶中C27和C29正构烷烃富集轻同位素。因此,可以应用草、芦苇和树叶中正构烷烃主峰碳数、CPI值和ACL值以及草、树叶中C27、C29正构烷烃δD值指示环境特征。n-Alkanes and their carbon and hydrogen stable isotopes were analyzed in grasses,reeds and tree leaves from five regions with latitudes of 22° to 39° in China using GC-MS and GC-TC-IRMS techniques.The distribution of n-alkanes in the samples ranges from C15 to C35 with a high odd over even predominance and carbon-number maxima at C27,C29 or C31.The CPI values are from 3.49 to 17.25,and the mean values show a characteristic of tree leafmreedmgrass.The ACL values are between 26.24 and 30.26 and the mean values exhibit a trend of grassmreedmtree leaf.It is observed that Cmax,CPI and ACL values of n-alkanes in the studied plants from low latitude area are higher than those from high latitude area.In this study,it is found that a change of ACL units for crossing 1 latitude and increasing 1 C is 0.08 for grass,0.22 for reed and 0.36 for tree leaf and 0.04 for grass,0.24 for reed and 0.20 for tree leaf,respectively.The δ^13C values of C27 and C29 n-alkanes in the studied plants ranges from-25.3‰ to-35.5‰ and the grass has a lighter mean carbon isotopic composition than the reed and tree leaf.The δD values of C27 and C29 n-alkanes in the plants are between-132.1‰ and-192.6‰ and the mean hydrogen isotopic compositions of C27 and C29 n-alkanes in the grass are lighter than those in the reed and tree leaves.C27 and C29 n-alkanes in the grass and tree leaf samples from high latitude and elevation area have relatively light hydrogen isotopic composition.Therefore,Cmax,CPI and ACL values of n-alkanes in grasses,reeds and tree leaves and δD values of C27 and C29 n-alkanes in grasses and tree leaves can be used to indicate palaeoenvironmental characteristics.

关 键 词：植物 正构烷烃分布 同位素组成 环境因子 

分 类 号：P593[天文地球—地球化学]