长江流域河水和悬浮物的锂同位素地球化学研究  

Lithium Isotopic Composition of the Dissolved and Suspended Loads of the Yangtze River,China

作　　者：汪齐连[1] 刘丛强[1] 赵志琦[1] B. Chetelat 丁虎[1] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室

出　　处：《地球科学进展》2008年第9期952-958,共7页Advances in Earth Science

基　　金：国家自然科学基金重点项目“乌江水能开发对流域水环境影响的因素辨识及其表征体系研究”(编号:90610037);国家自然科学基金面上项目“流域侵蚀过程的锂同位素分馏”(编号:40773006)资助

摘　　要：深入理解流域侵蚀过程中的锂同位素分馏对于运用锂同位素来示踪化学循环和气候变化是十分必要的。研究集中在长江干流和主要支流的水体和悬浮物的锂及锂同位素组成。长江流域水体的锂及锂同位素组成(δ7Li)分别为150~4570 nmol/L和+7.6‰^+28.1‰,两者沿上游至下游的变化趋势相反。悬浮物锂同位素组成(δ7Li)变化比较稳定,分别为41~92μg/g和-4.7‰^+0.7‰,而且总是低于相应水体的锂同位素组成。悬浮物和流体之间的锂同位素分馏系数在0.977和0.992之间,与悬浮物的量及组成存在明显相关性,反映了粘土矿物的吸附和化学风化的程度。锂含量与锂同位素组成之间良好的负相关性表明流域水体的锂来自2个端元混合:其一可能是蒸发盐岩,并伴有深部热泉水;其二可能是硅酸岩。A comprehensive understanding of lithium-isotope fractionation during terrestrial weathering is necessary in order to use lithium isotopes to trace chemical cycle and climatic changes. This study investigates lithium and lithium isotopic composition in the main tributaries and the main Yangtze river channel. The concentrations and isotopic compositions （δ^7Li） of dissolved Li in the Yangtze river are in the range of 150n mol/L- 4570n mol/L and in the range of ＋ 7.6‰- ＋ 28.1‰ respectively. Lithium isotopic compositions （ δ^7 Li） of the suspended matter are relatively stable （ -4.7‰～ ＋0.7‰） , and lighter than those of dissolved Li in the Yangtze river. Isotopic fractionation factors of between dissolved and suspended loads range from 0.977 to 0. 992, and are corrected with the concentration and chemical composition of suspended matter in the Yangtze river main channel. This should refleet the adsorption of clay mineral and the degree of chemical weathering. The positive relationship between δ^7Li and 1/Li for the dissolved load shows that the dissolved lithium probably has two main sources. One may be evaporites with some thermal spring, and another one may be silicates.

关 键 词：锂同位素 同位素分馏 粘土矿物 化学风化 来源 

分 类 号：P618.71[天文地球—矿床学] P512.12[天文地球—地质学]