湖泊沉积有机碳同位素与环境变化的研究进展

湖泊沉积有机质稳定碳同位素（δ^13Corg)在区域气候与环境变化方面的应用近年来发展迅速，成果令人瞩目，保存在各类湖泊岩芯中的δ^13Corg记录揭示了晚更新世以来大气CO2浓度的变化、湖泊水位波动、湖区生态与植被的变迁以及气温变化等重要环境信息，由于造成δ^13Corg值变化的影响因素较多，确定个湖与环境变化有关的主导因素时常有赖于其它证据的帮助，诸如地球化学、古湖沼学、孢粉学、分子同位素地层学等等，前人通过研究来自不同类型湖泊、具不同曲线形态特征的δ^13Corg记录，提出了多种环境解释模型，本文对此作了归纳和评述。鉴别和澄清湖泊沉积有机质的源物质以及有机物源随环境变化而发生过的变化，是研究δ^13Corg记录环境意义至关重要的基础性工作，由于有机质含量、碳氮比值、氢指数、生物残留物鉴别等常能提供有关有关湖泊有机质来源、产率、成岩作用等方面的有用信息，这方面的研究结果应该尽可能一并提供，以利于恰当地应用现有的环境解释模型，或者建立个湖新模型，单体生物标志化合物鉴别通常也能为区分湖积有机质中陆生、水生、细菌生等不同碳的来源提供有用信息，特定化合物同位素分析技术近年来成功地应用于建立单体生物标志化合物碳同位素地层学，为湖积有机碳同位素在生态环境演变研究方面的应用提供了思路，我国许多湖泊的湖底沉积岩芯尚未钻取，那些对过去全球变化研究有价值的δ^13Corg记录有待我们去获取和研究。

Paleoenvironmental Interpretations on Organic Carbon Isotopic Records from Lake Sediments:A Critique

Organic carbon isotopic records from lake sediments are valuable proxies used to indicate glacial-interglacial change in atmospheric pCO2, major changes in catchment vegetation, lake level fluctuations, and variations in regional temperature. While factors affecting variations in organic carbon isotope (δ13Corg) are numerous, predominant control(s) on the shift of δ13Corgvalue were often found out with the aid of evidence from other investigations on the lake sediments such as paleolimnological, geochemical, sedimentological and palynological studies, as well as molecularisotopic stratigraphy. Environmental explanation models (EEMs), proposed by investigators in the previous researches for those long-term isotopic records showing different curve patterns, are reviewed.Recognition and clarification of source materials of organic matter (OM) buried in lake sediments and of possible changes in organic source materials in the past are fundamental aspects and important for the environmental interpretations of tδ13Corg records. OM contents, organic carbon to nitrogen (C/N) ratios, hydrogen index (HI), petrographic examination of organic remains in lake sediments often provide useful information on organic productivity, origin, maturation, and diagenesis. Hence, they should be presented, if available, alongside with δ13Corg record. In this way, EEMs can then be properly applied, otherwise new EEMs may well be provided. In addition, identification of individual biomarkers often provides indication of specific terrestriall, aquatic, and bacterial sources of organic matter in lake sediments. New carbon isotopic signals reflecting Glacial/interglacial environmental change may well be indicated by molecular-isotopic stratigraphy. Long-term δ13Corg records from many interested lakes in China await us to investigate, depending largely on bottom sediment cores from those lake centers become available. These records have great potential for the researches of the past global changes.