【作者】 刘卫国； 杨洪； 黄永松； 李立武；

【Author】 LIU Weiguo YANG Hong HUANG Yongsong LI Liwu State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi’an , Shaanxi, 710075 Department of Science and Technology, Bryant University, Smithfield, RI 02917, USA Department of Geological Sciences, Brown University, Providence, RI02912, USA Lanzhou Institute of Geology, CAS, Lanzhou, Gansu, 730000

【机构】 中国科学院地球环境研究所黄土与第四纪地质国家重点实验室； Department of Science and Technology Bryant University,Smithfield,RI 02917,USA； Department of Geological Sciences Brown University,Providence,RI 02906,U.S.A； 中国科学院兰州地质研究所气体地球化学重点实验室；

【摘要】 近年来,随着高温裂解一色谱-同位素质谱技术的发展,使有机分子化合物氢同位素的生物地球化学研究成为可能,并已被应用到湖泊沉积物、泥炭等地质记录的古环境研究中。然而,由于目前对陆地植物有机分子化合物氢同位素组成变化与气候变化之间关系很好的认识,造成了地质纪录中有机分子化合物氢同位素组成变化解释的不确定性。笔者利用GC/TE/ IRMS方法初步测定了中国西北地区干旱-半干旱地区现代植物和黄土/古土壤序列中正构烷烃组分(主要来自植物叶蜡)的氢同位素组成。更多还原

【Abstract】 Development of compound-specific hydrogen isotope analysis (CSHIA) using gas chromatography/thermal conversion/isotope ratio mass spectrometry (GC/TC/IRMS) in recent years has spurred an upsurge of interests in obtaining paleoclimatic and paleoenvironmental information from D/H ratios ofindividual organic compounds. Here, the δD values of n-alkanes extracted from 34 modern terrestrial plants, including 21 C3 grasses and 13 C4 grasses in northwestern China, have been determined. The δD values range from-103‰ to-200‰ for C27, from-115‰ to-2052 for C29, and from-113‰ to-226‰ for C31. The authors have found that the stable hydrogen isotope of plant leaf wax is responding to the terrestrial plant type, such as wood (tree and shrub) and grass. Although complex factors such as temperature, precipitation δD values and plant photosynthesis path can affect hydrogen isotopic composition of plants, the source water δD values may be a dominated factor. The δD values of the n-alkanes from Xifeng loess profile spanning the last 130 kyr show large variations for the past 130 kyr, ranging from-140‰ to-190‰. Peaks of high δD values coincide with dry phases (loess sections, δ18O stages 2 and 4), whereas those of low δD values coincide with wet phases (paleosol sections, δ18O stages 1, 3 and 5). The results obtained demonstrate that the combined D/H ratios of individual long chain n-alkanes and C31/C29 n-alkane ratios can be used as additional proxies for paleoenvironmental reconstructions in the Loess Plateau of China.更多还原