Subsurface weathering signatures in stream chemistry during an intense storm
Subsurface weathering signatures in stream chemistry during an intense storm
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DOI：
10.1016/j.epsl.2022.117773
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发表时间：
2022-08-26
影响因子：
5.3
通讯作者：
Druhan, Jennifer L.
中科院分区：
文献类型：
--
作者：
Golla, Jon K.;Bouchez, Julien;Druhan, Jennifer L.
河流化学和排放之间的长期关系受到流域地下结构和生物地球化学功能的调节。这些机制在风暴事件期间河流的地球化学响应中表达和探索的程度仍然是一个悬而未决的问题。在这里，我们监测了一场强烈的风暴，因为它渗透到高地山坡，流入一条小陡峭的峡谷溪流，其特征是岩石衍生溶质中的化学浓度-排放关系。我们的方法将溪流中稳定锂同位素比 (87Li) 的高频记录与山坡内岩石水分的新颖采样结合起来。在峰值放电时，流中的锂钠比(Li/Na)从0.58μM/mM增加到0.82μM/mM，并且87Li从+28.9+/-0.1%0减少到+26.4+/-0.4%0。山坡水文监测显示，雨水渗入地下，但本次风暴严重衰弱的8D信号突破衰减（低至±86%0）仅到达包气带上部3-4米。这些 8D 数据显示，雨水与先前储存的岩石水分混合，并将储存的液体转移到更深的深度，导致地下水位明显上升。地下水 87Sr/86Sr 和 87Li 表现出在暴风雨之前和期间发生在地下水位以下的流体-岩石相互作用的一致性。总而言之，这些观察结果表明，在风暴期间，通过山坡内部的流体转移和溶质的生成产生了溪流内Li/Na和87Li的变化，并支持应用先前建立的一维反应输运模型框架，该模型框架是为山坡内锂的演变而开发的，以适应这种极端的水文事件。根据该模型，Li/Na 和 87Li 与流量的关系都反映了流体通过山坡内部的整体传输时间较短。这些模型结果与我们的水文观测结果一致，并表明来自进一步上坡（渗流区变得更厚）的锂有助于风暴高峰时的流溶质化学。我们得出的结论是，在该系统中，即使在强烈的风暴事件期间，流锂同位素特征也记录了山坡内水的流动和溶质的生成。 (c) 2022 作者。由 Elsevier B.V 出版。这是一篇遵循 CC BY-NC-ND 许可证 (http://creativecommons.org/licenses/by-nc-nd/4.0/) 的开放获取文章。上标/下标可用
Long-term relationships between stream chemistry and discharge are regulated by watershed subsurface structure and biogeochemical functioning. The extent to which these mechanisms are expressed and may be explored in the geochemical response of streams during storm events remains an open question. Here, we monitor an intense storm as it infiltrated an upland hillslope draining into a small steep canyon stream that is typified by chemostatic concentration-discharge relationships in rock-derived solutes. Our approach couples a high-frequency record of stable lithium isotope ratios (87Li) in the stream with novel sampling of rock moisture within the hillslope. At peak discharge, lithium-sodium ratios (Li/Na) increased from 0.58 mu M/mM to 0.82 mu M/mM and 87Li decreased from +28.9 +/- 0.1%0 to +26.4 +/- 0.4%0 in the stream. Hillslope hydrologic monitoring reveals that the rainwater infiltrated the subsurface, yet attenuated breakthrough of the heavily depleted 8D signal of this storm (as low as & minus;86%0) only reached the upper 3-4 meters of the vadose zone. These 8D data show that the storm water mixed with previously stored rock moisture and displaced stored fluid to deeper depths, causing an observable rise in the water table. Groundwater 87Sr/86Sr and 87Li demonstrate consistency in the fluid-rock interactions that occur below the water table prior to and during the storm. In total, these observations indicate that the transfer of fluid and generation of solutes through the interior of the hillslope produce the variability of Li/Na and 87Li within the stream during the storm, and support application of a previously established 1-D reactive transport model framework developed for the evolution of lithium within the hillslope to this extreme hydrologic event. Based on the model, both Li/Na and 87Li versus discharge relationships reflect an overall shorter transit time of fluid through the interior of the hillslope. These model results are consistent with our hydrologic observations and indicate that Li from further upslope (where the vadose zone becomes thicker) contributes to stream solute chemistry at the height of the storm. We conclude that in this system, stream lithium isotope signatures record the routing of water and generation of solutes within the hillslope even during intense storm events. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Superscript/Subscript Available