摘要
沉积物所记录的微量金属含量与形态的变化是指示人类活动影响下水体环境变化的有效指标,主要用于指示沉积物重金属污染、水体初级生产力变化和氧化还原条件等方面的水体环境状况。总体而言,沉积物中微量金属含量在近一个世纪以来显著上升,反映了采矿、冶金、污水排放、化肥使用、煤炭和石油燃烧等各种人类活动造成水体和沉积物重金属污染的记录作为浮游植物微量营养元素,Cu、Zn、Ni、Ba、Cd等在沉积物中的记录可以指示水体初级生产力水平。U、Mo、V、Cu、Cd、Mn等氧化还原敏感元素在沉积物中的富集或贫化,及其比值(如Re/Mo、Cd/U、Th/U和V/Sc)的变化,是指示水体和沉积物氧化还原环境的有效指标。但需要指出的是,在受人类活动影响的水体中,这些生产力和氧化还原指标很少能指示水体生产力或氧化还原状况,可能主要与人类活动同时造成这些金属元素大量污染输入而掩盖了其自生来源和内在变化的沉积记录有关。所以,对沉积物中微量金属元素来源的判别(陆源碎屑输入、人为输入和水体自生来源)是重建水体环境变化的重要前提。本文总结了多种化学和统计学方法(包括同位素示踪法、化学提取法、富集因子法和主成分分析法等)在沉积物金属来源判别中的应用另外,成岩作用等多种因素会干扰沉积物金属记录对环境变化的指示作用。
Trace metals and their species in sediments are powerful proxies to indicate the human-induced environmental changes of waters including heavy metal contamination, primary productivity and redox conditions of depositional environment. Concentrations of heavy metals in sediments from many waters have substantially increased over the past century. This revealed the elevated loading of heavy metals caused by various human activities, such as mining, smehing, sewage discharge, application of fertilizer and the combustion of coal and oil, etc. Cu, Zn, Ni, Ba and Cd are micro-nutrients for phytoplankton, whose concentrations in sediments couldindicate the changes in primary productivity in water. Redox-sensitive elements including U, Mo, V, Cu, Cd and Mn and their ratios, such as Re/Mo, Cd/U, Th/U and V/Sc, were useful tracers for redox state of the depositional environment. It is worth noticing that these productivity and redox proxies could hardly reflect the productivity and redox conditions in waters which were strongly affected by human activities. This probably results from the anthropogenic input of these elements which might mask their authigenic and diagenetic records in sediment. Therefore, identification of the sources of trace metals is crucial in indicating past environmental changes. Several chemical and statistical methods for discriminating the sources of trace metals have been summarized, including isotopic tracer, chemical extraction, enrichment factor and principal factor analysis. Furthermore, digenesis might disturb the sediment records of trace metals and thus affect the reconstruction of environment changes of water＂ by these metals. The application of multiple metal proxies is a promising way to properly read the sediment records and reconstruct the historv of aquatic environmental changes.
出处
《地质论评》
CAS
CSCD
北大核心
2012年第5期911-922,共12页
Geological Review
基金
国家自然科学基金创新群体项目(编号41121064)
国家重点基础研究发展计划973项目课题(编号2011CB403602)的成果
