Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation
Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation
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黄河中游锂同位素：季节变化、来源和分馏
DOI：
10.1016/j.gca.2019.01.007
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发表时间：
2019-03-01
影响因子：
5
通讯作者：
Galy, Albert
中科院分区：
文献类型：
--
作者：
Gou, Long-Fei;Jin, Zhangdong;Galy, Albert
为了评估气候和水文在大陆尺度硅酸盐风化中的作用，我们将Li同位素应用于黄河，系统地研究了季节Li通量、Li同位素组成和潜在来源。我们在2013年整个水文年度每周从黄河中游采集样本。结果表明，黄河流域溶解锂主要来源于硅酸盐和碳酸盐。黄河中游黄土的硅酸盐风化作用是影响土壤Li通量的主要因素，溶解Li通量与物理侵蚀速率呈正相关。在黄河中游，蒸发岩对河流Li的贡献相对稳定，但在暴雨事件后略有增加，平均比例接近25%，这可能代表了蒸发岩对全球海洋的贡献比例。河流Li同位素组成的季节变化主要受温度控制，全年分馏梯度为-0.182 ‰/℃，偏差可能由悬浮颗粒物的再溶解、极端水文事件和地下水贡献驱动。输入海洋的河水的温度依赖性三角洲Li-7值变化表明，新生代气候变冷本身可能能够解释新生代海水三角洲Li-7值上升的千分之九中的千分之二（Misra和Froelich，2012年）。河流Li同位素的季节性变化表明，黄土的侵蚀和风化可能为长期化学风化和海水三角洲Li-7的变化提供了有价值的线索。(C)2019爱思唯尔有限公司版权所有。
To evaluate the roles of climate and hydrology in continental-scale silicate weathering, we applied Li isotopes to the Yellow River and systematically investigated seasonal Li flux, Li isotopic compositions and potential sources. We collected samples from the middle reaches of the Yellow River weekly over the full hydrological year of 2013. We find that the dissolved Li is mainly derived from silicates and evaporites in the arid to semi-arid Yellow River basin. Silicate weathering of loess during the monsoonal season dominates the Li flux in the middle reaches of the Yellow River, with a positive relationship between dissolved Li flux and physical erosion rate. Evaporite contribution for riverine Li was relatively constant in the middle reaches of the Yellow River but slightly increased after the storm event, with an average proportion of similar to 25%, which might represent the proportion of evaporite contribution to global oceans. Seasonal variations in the riverine Li isotopic compositions are dominantly controlled by temperature with a fractionation gradient as -0.182 parts per thousand per degrees C over the full year with deviations likely driven by re-dissolution of suspended particulate matter, extreme hydrological events, and groundwater contribution. Temperature dependent delta Li-7 value variation of river water inputted into oceans indicates that Cenozoic climate cooling itself may be able to explain similar to 2 parts per thousand of the 9 parts per thousand rise of Cenozoic seawater delta Li-7 value (Misra and Froelich, 2012). The seasonal variation in riverine Li isotopes highlights that erosion and weathering of loess may provide valuable clues on secular chemical weathering and seawater delta Li-7 variation spanning a range of time scales. (C) 2019 Elsevier Ltd. All rights reserved.