黄土碳酸盐稳定同位素研究进展及其气候环境意义

Advances in climate and environmental significance of stable isotopes of carbonates in loess

关键词:  黄土碳酸盐  碳氧同位素  锶同位素  锂同位素  硼同位素  镁同位素

Key words:  carbonates in loess  carbon and oxygen isotopes  strontium isotope  lithium isotope  boron isotope  magnesium isotope

摘要:

黄土碳酸盐中的稳定同位素是重建古气候与古环境极为重要且成熟的方法，然而部分同位素指标的具体气候意义及其可靠性仍需进一步探讨。文章系统回顾了黄土碳酸盐中传统稳定同位素（C、O、Sr）与非传统稳定同位素（B、Li、Mg）的研究进展，综述了它们对气候与环境重建的指示意义。传统稳定同位素（δ¹³C、δ¹⁸O、⁸⁷Sr/⁸⁶Sr）作为重建植物分布及发育状况、大气CO₂环境、温度变化、降水状况及化学风化强度的指标已较为成熟，团簇同位素 （Δ₄₇） 为定量古温度测定提供了新方法。部分非传统稳定同位素 （δ²⁶Mg、δ⁷ Li、δ¹¹B）在示踪东亚季风演化与指示黄土化学风化过程方面的潜力也已得到初步验证。虽然黄土碳酸盐稳定同位素指示全球气候变化已较为成熟，但未来研究仍应深化对同位素分馏机制的理解及各指标影响机制的分析，共同推动黄土同位素研究发展。

Abstract:

Background, aim, and scope Stable isotopes in loess carbonates serve as highly important and wellestablished proxies for reconstructing paleoclimate and paleoenvironments. However, the specific climatic significance and reliability of some isotopic indicators require further investigation. This paper systematically reviews the research advances in both traditional stable isotopes and non-traditional stable isotopes in loess carbonates to provide methodological insights and theoretical support. Materials and methods In this paper, the studies of stable isotopes (δ¹³C, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr) and non-traditional stable isotopes (δ²⁶Mg, δ⁷ Li and δ ¹¹B) in loess carbonates are reviewed, and their significance in climate change is summarized. The literature search for this review was conducted primarily using the Web of Science and Elsevier ScienceDirect. Keywords such as loess carbonate, isotopes, climate, monsoon, and environment were employed to retrieve relevant publications.Results Related studies have reported the paleoclimatic and paleoenvironmental significance of traditional and non-traditional stable isotopes in loess carbonates. Discussion Traditional stable isotopes ( ¹³C, ¹⁸O and ⁸⁷Sr/⁸⁶Sr) have matured as proxies for reconstructing paleovegetation types, paleoatmospheric CO₂ levels, paleotemperature/ precipitation, and chemical weathering intensity, while the clumped isotopes (Δ₄₇) provide an independent method for quantitative paleothermometry. Moreover, the potential of some nontraditional stable isotopes ( ²⁶Mg, ⁷ Li and ¹¹B) for tracing the evolution of the East Asian monsoon and chemical weathering processes has received preliminary validation. However, the reliability of carbon isotopes in reconstructing C₃/C₄ plant relative abundance remains under debate, and the indicative significance of some non-traditional stable isotopes on climate is not clear. Conclusions In the past few decades, researchers have expanded the scope of stable isotopes in loess carbonates to explore new indicators for climate change. The research on the stable isotope of carbonate in loess has obtained mature and perfect research methods and theoretical basis. The C, O, Sr, Mg, Li and B isotopes in loess carbonate are reliable proxies for studying climate change. They are valuable in tracing the chemical weathering process of loess, the evolution of East Asian monsoon, and abrupt climatic events. However, there are still some shortcomings in stable isotope studies of carbonate in loess. Recommendations and perspectives Future research should deepen understanding isotopic fractionation mechanisms and analyzing affecting factors of traditional proxies, and expand the research potential of non-traditional stable isotopes in loess carbonates. Efforts should be directed toward promoting the loess isotopes in paleoclimatic and paleoenvironmental reconstructions across multiple temporal and spatial scales, as well as advancing quantitative reconstruction methods.