① 兰州大学西部环境与气候变化研究院西部环境教育部重点实验室, 兰州 730000;
② 中国科学院广州地球化学研究所边缘海地质重点实验室, 广州 510640

为了查明单一生态系统下表土中高等植物来源长链正构烷烃单体氢同位素 (δD_n-alkanes)的变化特征, 从华北张家口市万全县大麻坪玄武岩风化壳随机采集了12 个表层土壤样品, 用来分析其长链正构烷烃分子组成特征及其单体碳(δ¹³C_n-alkanes)、氢同位素, 同时分析了其总有机质碳同位素(TOC, δ¹³CTOC)变化. 结果表明δ¹³CTOC 和来源于陆生高等植物的4 个代表性的占优势地位的长链正构烷烃(n-C₂₇, n-C₂₉, n-C₃₁, n-C₃₃)的δ¹³C_n-alkanes 在这12 个样品中都非常稳定, 仅有很小的变化幅度, 这两类碳同位素数据均表明其上覆植被的光合作用类型构成非常均一, 可以视为由纯C₃ 草本植物构成. 相应的这4 个主要长链正构烷烃的δD_n-alkanes 变化幅度比较大, 整体而言, 相对丰度越高的同族体分子, 其δD_n-alkanes 更为偏负, 且其变化幅度更小. 然而, 这4 个主要长链正构烷烃加权平均δD_n-alkanes值约30‰的变化幅度小于先前研究当中报道的同一地点不同现代陆生C₃ 草本植物之间长链正构烷烃 δD_n-alkanes 值的变化幅度, 甚至小于同一植物种长链正构烷烃δD_n-alkanes 值的季节变化幅度. 由于表土和沉积物中长链正构烷烃来源上的相似性, 即它们都来源于多种植物的混合, 因此, 我们的结果对于沉积物, 尤其是其有机质为原地植物来源的陆相沉积物的长链正构烷烃单体氢同位素组成的古气候、古环境、古水文信息的精确解译, 具有一定的参考价值.

国家自然科学基金(批准号: 40901055, 40872111)、教育部科学技术研究重点项目(批准号: 109151)、国家重点基础研究发展计划(编号: 2010CB950202)和国家自然科学基金创新群体项目(批准号: 41021091)资助

1 Huang Y S, Clemens S C, Liu W G, et al. Large-scale hydrological change drove the late Miocene C₄ plant expansion in the Himalayan foreland and Arabian Peninsula. Geology, 2007, 35: 531–534  
2 Pagani M, Pedentchouk N, Huber M, et al. Arctic hydrology during global warming at the Palaeocene/Eocene thermal maximum. Nature, 2006, 442: 671–675  
3 Schefuss E, Schouten S, Schneider R R. Climatic controls on central African hydrology during the past 20000 years. Nature, 2005, 437: 1003–1006  
4 Jahren A H, Byrne M C, Graham H V, et al. The environmental water of the middle Eocene Arctic: Evidence from δD, δ¹⁸O and δ¹³C within specific compounds. Palaeogeogr Palaeoclimatol Palaeoecol, 2009, 271: 96–103
5 Liu W G, Huang Y S. Compound specific D/H ratios and molecular distributions of higher plant leaf waxes as novel paleoenvironmental indicators in the Chinese Loess Plateau. Org Geochem, 2005, 36: 851–860  
6 Seki O, Meyers P A, Kawamura K, et al. Hydrogen isotopic ratios of plant wax n-alkanes in a peat bog deposited in northeast China during the last 16 kyr. Org Geochem, 2009, 40: 671–677  
7 Xie S, Nott C J, Avsejs L A, et al. Palaeoclimate records in compound-specific δD values of a lipid biomarker in ombrotrophic peat. Org Geochem, 2000, 31: 1053–1057  
8 Xie S C, Nott C J, Avsejs L A, et al. Molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction. Geochim Cosmochim Acta, 2004, 68: 2849–2862  
9 Bi X H, Sheng G Y, Liu X H, et al. Molecular and carbon and hydrogen isotopic composition of n-alkanes in plant leaf waxes. Org Geochem, 2005, 36: 1405–1417  
10 Chikaraishi Y, Naraoka H. Compound-specific δD-δ¹³C analyses of n-alkanes extracted from terrestrial and aquatic plants. Phytochemistry, 2003, 63: 361–371  
11 Chikaraishi Y, Naraoka H. Carbon and hydrogen isotope variation of plant biomarkers in a plant-soil system. Chem Geol, 2006, 231: 190–202  
12 Hou J Z, D’Andrea W J, MacDonald D, et al. Hydrogen isotopic variability in leaf waxes among terrestrial and aquatic plants around Blood Pond, Massachusetts (USA). Org Geochem, 2007, 38: 977–984  
13 Krull E, Sachse D, Mugler I, et al. Compound-specific δ¹³C and δ²H analyses of plant and soil organic matter: A preliminary assessment of the effects of vegetation change on ecosystem hydrology. Soil Biol Biochem, 2006, 38: 3211–3221  
14 Liu W G, Yang H, Li L W. Hydrogen isotopic compositions of n-alkanes from terrestrial plants correlate with their ecological life forms. Oecologia, 2006, 150: 330–338  
15 Mügler I, Sachse D, Werner M, et al. Effect of lake evaporation on δD values of lacustrine n-alkanes: A comparison of Nam Co (Tibetan Plateau) and Holzmaar (Germany). Org Geochem, 2008, 39: 711–729  
16 Sachse D, Radke J, Gleixner G. δD values of individual n-alkanes from terrestrial plants along a climatic gradient——Implications for the sedimentary biomarker record. Org Geochem, 2006, 37: 469–483  
17 Sachse D, Kahmen A, Gleixner G. Significant seasonal variation in the hydrogen isotopic composition of leaf-wax lipids for two deciduous tree ecosystems (Fagus sylvativa and Acer pseudoplatanus). Org Geochem, 2009, 40: 732–742  
18 Sessions A L. Seasonal changes in D/H fractionation accompanying lipid biosynthesis in Spartina alternflora. Geochim Cosmochim Acta, 2006, 70: 2153–2162  
19 Smith F A, Freeman K H. Influence of physiology and climate on δD of leaf wax n-alkanes from C₃ and C₄ grasses. Geochim Cosmochim Acta, 2006, 70: 1172–1187  
20 Yang H, Leng Q. Molecular hydrogen isotope analysis of living and fossil plants——Metasequoia as an example. Prog Nat Sci, 2009, 19: 901–912  
21 段毅, 吴保祥. 中国大陆主要植物中单体正构烷烃氢同位素组成及其与环境关系研究. 科学通报, 2008, 53: 2776–2781
22 Hou J Z, D’Andrea W J, Huang Y S. Can sedimentary leaf waxes record D/H ratios of continental precipitation? Field, model, and experimental assessments. Geochim Cosmochim Acta, 2008, 72: 3503–3517  
23 Huang Y S, Shuman B, Wang Y, et al. Hydrogen isotope ratios of individual lipids in lake sediments as novel tracers of climatic and environmental change: A surface sediment test. J Paleolimn, 2004, 31: 363–375  
24 Sachse D, Radke J, Gleixner G. Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability. Geochim Cosmochim Acta, 2004, 68: 4877–4889  
25 Sauer P E, Eglinton T I, Hayes J M, et al. Compound-specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions. Geochim Cosmochim Acta, 2001, 65: 213–222  
26 Seki O, Nakatsuka T, Shibata H, et al. A compound-specific n-alkane δ¹³C and δD approach for assessing source and delivery processes of terrestrial organic matter within a forested watershed in northern Japan. Geochim Cosmochim Acta, 2010, 74: 599–613  
27 Xia Z H, Xu B Q, Mügler I, et al. Hydrogen isotope ratios of terrigenous n-alkanes in lacustrine surface sediment of the Tibetan Plateau record the precipitation signal. Geochem J, 2008, 42: 331–338  
28 Rao Z G, Zhu Z Y, Jia G D, et al. Compound specific δD values of long chain n-alkanes derived from terrestrial higher plants are indicative of the δD of meteoric waters: Evidence from surface soils in eastern China. Org Geochem, 2009, 40: 922–930  
29 Jia G D, Wei K, Chen F J, et al. Soil n-alkane δD vs. altitude gradients along Mount Gongga, China. Geochim Cosmochim Acta, 2008, 72: 5165–5174  
30 Hou J, D’Andrea W J, MacDonald D, et al. Evidence for water use efficiency as an important factor in determining the δD values of tree leaf waxes. Org Geochem, 2007, 38: 1251–1255  
31 饶志国, 贾国东, 朱照宇, 等. 中国东部表土总有机质碳同位素和长链正构烷烃碳同位素对比研究及其意义. 科学通报, 2008, 53: 2077–2084
32 Cranwell P A. Lipid geochemistry of sediments from Upton Broad, a small productive lake. Org Geochem, 1984, 7: 25–37  
33 Ratnayake N P, Suzuki N, Okada M, et al. The variations of stable carbon isotope ratio of land plant-derived n-alkanes in deep-sea sediments from the Bering Sea and the North Pacific Ocean during the last 250,000 years. Chem Geol, 2006, 228: 197–208
34 Cranwell P A, Eglinton G, Robinson N. Lipids of aquatic organisms as potential contributors to lacustrine sediments——II. Org Geochem, 1987, 11: 513–527  
35 Rieley G, Collier R J, Jones D M, et al. Sources of sedimentary lipids deduced from stable carbon isotope analyses of individual compounds. Nature, 1991, 352: 425–427  
36 Rielley G, Collier R J, Jones D M, et al. The biogeochemistry of Ellesmere Lake, U.K.——I: Source correlation of leaf wax inputs to the sedimentary lipid record. Org Geochem, 1991, 17: 901–912  
37 Eglinton G, Hamilton R J. Leaf epicuticular waxes. Science, 1967, 156: 1322–1334  
38 O’Leary M H. Carbon isotope in photosynthesis. Bioscience, 1988, 38: 328–336  
39 Farquhar G D, Ehleringer J R, Hubick K T. Carbon isotope discrimination and photosynthesis. Annu Rev Plant Physiol Mol Biol, 1989, 40: 503–537  
40 Stewart G R, Turnbull M H, Schmidt S, et al. ¹³C natural abundance in plant communities along a rainfall gradient: A biological integrator of water availability. Aust J Plant Physiol, 1995, 22: 51–55  
41 王国安, 韩家懋, 刘东生. 中国北方黄土区C₃ 草本植物碳同位素组成研究. 中国科学D 辑: 地球科学, 2003, 33: 550–556
42 王国安, 韩家懋, 周力平, 等. 中国北方黄土区C₄ 植物稳定碳同位素组成的研究. 中国科学D 辑: 地球科学, 2005, 35: 1174–1179
43 Melillo J M. Carbon and nitrogen dynamics along the decay continuum: Plant litter to soil organic matter. Plant Soil, 1989, 115: 189–198  
44 Connin S L. Isotopic discrimination during long-term decomposition in an arid land ecosystem. Soil Biol Biochem, 2001, 33: 41–51  
45 Tieszen L L, Reed B C, Bliss L B, et al. NDVI, C₃ and C₄ production and distributions in Great Plains grassland land cover classes. Ecol Appl, 1997, 7: 59–78
46 Bird M I, Pousai P. Variations of Delta ¹³C in the surface soil organic carbon pool. Glob Biogeochem Cycle, 1997, 11: 313–322  
47 顾兆炎, 刘强, 许冰, 等. 气候变化对黄土高原末次盛冰期以来的C₃/C₄ 植物相对丰度的控制. 科学通报, 2003, 48: 1458–1464
48 饶志国, 陈发虎, 曹洁, 等. 黄土高原西部地区末次冰期和全新世有机碳同位素变化与C₃/C₄ 植被类型转换研究. 第四纪研究, 2005, 25: 107–114
49 Collister J W, Rieley G, Stern B, et al. Compound-specific δ¹³C analysis of leaf lipids from plants with differing carbon dioxide metabolism. Org Geochem, 1994, 21: 619–627  
50 Rieley G, Collister J W, Stern B, et al. Gas chromatography-isotope ratio mass spectrometry of leaf waxes n-alkanes from plants of differing carbon dioxide metabolisms. Rapid Commun Mass Spectrom, 1993, 7: 488–491  
51 Brincat D, Yamada K, Ishiwatayi R, et al. Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments. Org Geochem, 2000, 31: 287–294