氧化还原敏感性元素在沉积环境判别中的应用研究进展

Application and influence factors of redox-sensitive elements in a sedimentary environment

部分元素对氧化还原环境非常敏感,氧化还原条件往往决定着这些元素的迁移或富集,这些元素被称为氧化还原敏感性元素(redox sensitive elements,RSE)。除Fe、Mn外大部分RSE在氧化环境条件下以溶解态离子形式存在于海洋水体而发生迁移,在还原环境条件下则容易从海洋水体中析出向沉积物中迁移并发生富集。RSE的这种特性常被用来判断现代或地质历史中的沉积环境。本文在总结RSE与沉积氧化还原环境判别的基础上,分析了影响RSE地球化学行为的因素,进而探讨了RSE应用中存在的主要问题及今后研究方向。RSE及相关指标在沉积环境判别中的应用主要包括:氧化还原状态的识别、指示海洋水体生产力变化、指示海洋水体的局限程度、指示沉积物物源等。影响或控制RSE迁移、转化、沉积和富集的主要因素有:成岩作用、陆源物质加入、粒控效应、Fe-Mn氧化物/氢氧化物的吸附、有机质含量、水体局限、人类活动等。迄今对部分RSE的迁移富集机制还不十分清楚,元素指标的应用较粗略。近期在RSE的应用中应重视样品的选取与保存、测量分析技术的提升以及多指标的互相印证,通过综合分析判断,才能得出更接近实际的结果。

Some elements are very sensitive to the redox environment,and the migration or enrichment of these elements is often determined by the redox conditions.These elements are called redox-sensitive elements(RSE).Except for Fe and Mn,most RSE in marine waters are in the form of dissolved ions in an oxidation environment,while they are easy to precipitate out from marine waters and migrate and accumulate to the sediment in a reduction environment.This characteristic of RSE is often used to judge the sedimentary environment in modern or geological history.On the basis of summarizing the application results of RSE in sedimentary environment discrimination,this paper analyzes the factors affecting the geochemical behavior of RSE and then discusses the main problems existing in the application of RSE and the research direction in the future.The application of RSE and related indicators in the identification of sedimentary environment includes the identification and detection of the redox state of marine waters,indicating the changes of productivity of marine waters,indicating the limitation degree of marine waters,and indicating the source of elements in the sediment.The main factors that affect or control the migration,trans-formation,deposition,and enrichment of RSE include diagenesis,the addition of terrestrial sources,particle size control effect,adsorption of Fe-Mn oxide/hydroxide,organic matter content,water limitation,and human activities.At present,the enrichment mechanism of part of RSE is not thoroughly studied,and the application of element in-dicators is relatively rough.The future research will focus on the sealed preservation of samples,the improvement of measurement technology and equipment,and the use of RSE to judge the sedimentary environment,which should be mutually verified by multiple indicators and a comprehensive judgment to obtain a practical result.