Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface
Spectral analysis of continuous redox data reveals geochemical dynamics near the stream–aquifer interface
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DOI：
10.1002/hyp.13335
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发表时间：
2018-12
影响因子：
3.2
通讯作者：
C. Wallace;A. Sawyer;R. Barnes
中科院分区：
文献类型：
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作者：
C. Wallace;A. Sawyer;R. Barnes
径流和地下水位高程的变化影响河流-含水层界面附近的氧化还原（氧化还原）条件，溶质通量和地球化学反应速率的潜在重要后果。虽然地下水化学的连续测量可能是艰巨的，但原位传感器可以在很宽的时间尺度上揭示化学动态。我们监测氧化还原电位在含水层相邻的潮汐河流，并使用光谱和小波分析连接氧化还原反应的床和银行内的水文扰动。风暴会在几天到几周的时间内扰乱河床和河岸的氧化还原电位。潮汐驱动半日振荡的河床内的氧化还原电位是在银行缺席。小波分析表明，潮汐氧化还原振荡在床是最大的夏末（小波幅度为5.62 mV）时，河流水位波动的顺序为70厘米和微生物活动相对较高。潮汐氧化还原振荡减少在冬季（小波幅度为2.73 mV）时，河流水位波动较小（在50厘米的顺序）和微生物活性大概是低的。虽然传统的地球化学观测通常仅限于夏季基流条件，但原位氧化还原传感提供了地下连续的高分辨率化学表征，揭示了含水层中跨空间和时间尺度的运输和反应过程。
Changes in streamflow and water table elevation influence oxidation–reduction (redox) conditions near river–aquifer interfaces, with potentially important consequences for solute fluxes and biogeochemical reaction rates. Although continuous measurements of groundwater chemistry can be arduous, in situ sensors reveal chemistry dynamics across a wide range of timescales. We monitored redox potential in an aquifer adjacent to a tidal river and used spectral and wavelet analyses to link redox responses to hydrologic perturbations within the bed and banks. Storms perturb redox potential within both the bed and banks over timescales of days to weeks. Tides drive semidiurnal oscillations in redox potential within the streambed that are absent in the banks. Wavelet analysis shows that tidal redox oscillations in the bed are greatest during late summer (wavelet magnitude of 5.62 mV) when river stage fluctuations are on the order of 70 cm and microbial activity is relatively high. Tidal redox oscillations diminish during the winter (wavelet magnitude of 2.73 mV) when river stage fluctuations are smaller (on the order of 50 cm) and microbial activity is presumably low. Although traditional geochemical observations are often limited to summer baseflow conditions, in situ redox sensing provides continuous, high‐resolution chemical characterization of the subsurface, revealing transport and reaction processes across spatial and temporal scales in aquifers.