Underlying riparian lithology controls redox dynamics during stage-driven mixing
Underlying riparian lithology controls redox dynamics during stage-driven mixing
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DOI：
10.1016/j.jhydrol.2021.126035
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发表时间：
2021-02
影响因子：
6.4
通讯作者：
C. Wallace;M. Soltanian
中科院分区：
文献类型：
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作者：
C. Wallace;M. Soltanian
地表水-地下水（潜流）交换和沉积物岩性之间的相互作用影响河流-含水层界面附近的氧化还原（氧化还原）条件。氧化还原动力学对地下营养盐转化有影响，但难以使用传统的地球化学观测进行时空评估。本研究应用连续三维监测氧化还原电位在浅河岸含水层，以评估沉积物岩性和水文地质变量的地球化学响应。我们绘制了一系列的横截面氧化还原等高线图从整个含水层的风暴事件，捕获阶段驱动的混合过程中的氧化还原条件的动态。结果表明，氧化还原电位增加了超过400毫伏，在一些地方的河水渗透在风暴期间，而持久的高电位区忍受沿着优惠，高电导率的流动路径。高电导率（>1 cm/s）沉积物中的条件在风暴后需要更长的时间（长达30天）才能恢复，而在更细的低电导率（6.9 × 10− 5 cm/s）沉积物中（数天至数小时），然而，这归因于较少的有机物质驱动营养物质的转化。动态地表水-地下水相互作用间歇性扰动氧化还原条件，但底层沉积物岩性最终决定含水层氧化还原条件的时空动态。这些新的观察提供了基本的见解，广泛适用于水文地质学和地球化学的潜流交换和河岸地球化学动力学。
The interactions between surface water-groundwater (hyporheic) exchange and sediment lithology influence oxidation–reduction (redox) conditions near river-aquifer interfaces. Redox dynamics have implications for subsurface nutrient transformations, but are difficult to assess spatially and temporally using traditional geochemical observations. This study applied continuous, three-dimensional monitoring of redox potential in a shallow riparian aquifer to assess the geochemical response to sediment lithology and hydrogeologic variables. We mapped a series of cross-sectional redox contour plots from throughout the aquifer over a storm event, which captured the dynamics of redox conditions during stage-driven mixing. Results show that redox potential increased by over 400 mV at some locations following river water infiltration during the storm, while persistent zones of high potential endured along preferential, high-conductivity flow paths. Conditions within high-conductivity (>1 cm/s) sediments took longer to recover (up to 30 days) following storms than those within finer, low-conductivity (6.9 × 10−5cm/s) sediments (days to hours), however, attributed to less organic matter driving nutrient transformations. Dynamic surface water-groundwater interactions intermittently perturb redox conditions, but the underlying sediment lithology ultimately governs the spatial and temporal dynamics of aquifer redox conditions. These novel observations provide fundamental insights into hyporheic exchange and riparian geochemical dynamics broadly applicable to hydrogeology and biogeochemistry.