Contribution of deep groundwater to the weathering budget in a rapidly eroding mountain belt, Taiwan
Contribution of deep groundwater to the weathering budget in a rapidly eroding mountain belt, Taiwan
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DOI：
10.1016/j.epsl.2010.12.032
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发表时间：
2011-02-15
影响因子：
5.3
通讯作者：
Chapman, Hazel
中科院分区：
文献类型：
--
作者：
Calmels, Damien;Galy, Albert;Chapman, Hazel
我们分析了一个为期6年的时间序列的立雾河，台湾，以及现场样本的支流和地下水的水化学。在这个受台风事件影响的陡峭且排水良好的集水区，河流携带高溶解负荷（平均320 mg/L），主要是Ca（2+）和Mg（2+）（阳离子电荷的73 Eq %和21 Eq %）以及SO（4）（2-）和HCO（3）（-）（阴离子电荷的48 Eq %和51 Eq %）。滞后的Ca/Na放电数据和匹配的Ca/Sr放电数据的滞后的情况下被解释为反映了三个组件的混合。虽然河流化学在低流量到中等流量揭示了一个二元混合之间的快速地表径流的化学特征的一阶支流和一个组成部分可能有一个深层地下水化学，在高流量收集的样本显示的贡献第三水源不立即移动的，因此被称为缓慢的地表径流。这些端元的相对贡献已通过水文分离估计，然后通过模拟台风期间观测到的河流（87）Sr/（86）Sr变化（0.0013）进行验证。37年的平均值估计，16 +/-3%的河流流量来自深层地下水库，而缓慢和快速的地表径流分别提供21 +/-5%和63 +/-5%。缓慢的地表径流是最不好的端元特征，但模拟的水化学演变沿着其流动路径表明，阳离子在地表径流缓慢的水源区，通过生物吸收、细菌还原成土作用（粘土和碳酸盐沉淀）过程，可能部分由蒸发蒸腾作用驱动，蒸发蒸腾作用去除了该水库中75%的水。李屋的硅酸盐阳离子剥蚀速率为18 t km（-2）yr（-1），是目前世界上长英质岩石中硅酸盐阳离子剥蚀速率最高的地区之一。这一高值必须由以下事实来调节：1）硅酸盐的深层化学风化占该通量的1/3以上，以及2）硫酸风化在该集水区很重要。在台湾，化学物质的输入河流通量从深水库很可能是促进快速隆起的断裂岩石，但负责这种显着的地下水贡献的基本过程（化学反应在多孔介质）也存在于冲积和沉积盆地。(C)2010 Elsevier B.V.保留所有权利。
We analysed the water chemistry of a 6-yr time series of the Liwu River, Taiwan, as well as spot samples of tributaries and groundwater. In this steep and well-drained catchment impacted by typhoon events, the river carries a high dissolved load (average of 320 mg/L) dominated by Ca(2+) and Mg(2+) (73 Eq% and 21 Eq% of the cationic charge), and SO(4)(2-) and HCO(3)(-) (48 Eq% and 51 Eq% of the anionic charge). Hysteresis in Ca/Na-discharge data and absence of hysteresis in matching Ca/Sr-discharge data are interpreted as reflecting a mixing of three components. While river chemistry at low- to medium-flow reveals a binary mixing between a rapid surface runoff characterised by the chemistry of first-order tributaries and a component likely to have a deep groundwater chemistry, samples collected at high-flow show the contribution of a third water source not immediately mobile and therefore called slow surface runoff. The relative contribution of these end-members has been estimated through hydrograph separations, and then validated by modelling of the observed riverine (87)Sr/(86)Sr variations (0.0013) during a typhoon. The 37-yr average estimates that 16 +/- 3% of the river discharge comes from the deep groundwater reservoir while slow and rapid surface runoff provide 21 +/- 5% and 63 +/- 5%, respectively. The slow surface runoff is the least well characterised of the end-members but the modelled evolution of water chemistry along its flow-path suggests that cations (except Na) and sulphate are removed from the water in the slow surface runoff source region by the combination of biological uptake, bacterial reduction and pedogenesis (clays and carbonate precipitation) processes that might be partly driven by the evapo-transpiration that removes 75% of the water within this reservoir. The silicate cation denudation rate for the Liwu is 18 t km(-2) yr(-1), which is one of highest measured so far in the world for felsic lithologies. This high value has to be modulated by the facts that 1) deep chemical weathering of silicate accounts for more than 1/3 of this flux, and 2) sulphuric-acid weathering is significant in this catchment. In Taiwan, the input of chemicals in river flux from deep reservoirs is likely to be promoted by rapid uplift of fractured rocks, but the underlying processes (chemical reaction in a porous media) responsible for such significant groundwater contribution are also present in alluvial and sedimentary basins. (C) 2010 Elsevier B.V. All rights reserved.