元素碳碳同位素在古环境研究中的应用

The Application of Carbon Isotope of Element Carbon in the Research of Paleoenvironment

元素碳几乎完全来源于植被的燃烧,长期广泛地分布于大气、土壤、沉积物、岩石、水体和冰体等自然界载体中,记录了大量的古环境信息。利用元素碳碳同位素(δ13CEC)指标来反映古气候、古植被信息是将元素碳应用到古环境研究的一个重要方面,本文通过总结国内外学者利用δ13CEC指标进行古环境研究的现状,总结出对于"直接利用δ13CEC指标进行古环境恢复"这一关键问题还存在不同认识。燃烧前后物质的碳同位素是否发生变化是利用δ13CEC进行古环境研究时需要考虑的一个重要问题,国内外学者近20年来对C3、C4植物开展了大量燃烧实验,主要结论是C3植物燃烧前后物质的碳同位素变化(Δδ13C)较小,在±1‰以内,而C4植物变化范围较大,在0‰～-9‰之间;此外,文中还讨论了元素碳外源输入等可能影响δ13CEC指标的因素。建议在利用δ13CEC指标进行古环境重建之前,有必要对δ13CEC进行详细的基础研究工作,进一步研究表土δ13CEC与地表植被相关性以及元素碳外源输入等问题。

The element carbons are almost completely from the burning of plants, they exist in many natural reservoirs, such as atmospheres, soils, sediments, rocks, waters and ices, with long -term stability and wide distribution, and they record abound of paleoenvironment informations. The carbon isotope of element carbon （δ^13C_EC） provides important evidence for the reconstruction of paleoenvironment. In this article we analyzed a great deal of scholars＇ researches about using theδ^13C_EC proxy to study the paleoenvironment, and concluded that there were still some different views on the problem of whether this proxy can be used in recovering paleovegetation directly. Whether the carbon isotope changes during burning process is a very important problem to consider when we use δ^13C_EC to research the paleoenvironment. The scholars at home and abroad have done many researches on the burning experiments during the past twenty years, and their major conclusion was that the carbon isotope different between ＂before burning＂ and ＂after burning＂ （△δ^13C） for C3 plants was small, in ± 1‰; but △δ^13C rang for Ca plant was large, from 0‰to -9‰. In addition, we discussed other possible factors that may impact δ^13C_EC, like exogenous input. We suggested that before using δ^13C_EC proxy to study the paleoenvironment, it＇s necessary to do detail basic researches to study the relevance between the surface soil δ^13C_EC and the surface plants, and the exogenous input problem.