Comparing chloride and water isotopes as hydrological tracers in two Scottish catchments
Comparing chloride and water isotopes as hydrological tracers in two Scottish catchments
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DOI：
10.1002/hyp.7676
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发表时间：
2010-06-15
影响因子：
3.2
通讯作者：
Soulsby, Chris
中科院分区：
文献类型：
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作者：
Kirchner, James W.;Tetzlaff, Doerthe;Soulsby, Chris
氯离子浓度和氧-18同位素比值的时间序列被广泛用于跟踪流域存储和混合过程，并推断流域旅行时间分布。然而，无论是氯化物还是氧-18都不是理想的水文示踪剂：河水中的氯化物浓度可以受到干沉积、蒸发浓缩和地球化学循环的影响，水同位素可以通过蒸发而分馏。测试这些示踪剂的可靠性的一种方法是确定是否，尽管文物，如这些，两个示踪剂导致类似的推论时，在同一流域测量。在这里，我们比较氯和氧-18在苏格兰的格诺克和Allt' a Mharcaidh集水区的时间序列。两种示踪剂的半变异函数和功率谱表现出相似的波动阻尼模式，这意味着两种示踪剂的走时分布具有相似的形状。这两种示踪剂的波动强烈衰减径流相比，降水，这意味着这些集水区集成了许多不同的风暴事件的示踪剂签名。两种示踪剂的径流波动更强烈的阻尼在Allt' a Mharcaidh集水区，这意味着更长的存储和更大的混合不同年龄的沃茨，相比，Girnock集水区。在这两个网站，流量波动的氧-18更强烈的阻尼，相对于降水，比氯化物，导致估计的平均旅行时间是更长的，由2-3倍，氧-18比氯化物。与氧-18相比，氯化物的变异性更大，这可能是由于空间和时间上变化的隐匿性沉积和蒸发浓缩。尽管如此，两种示踪剂的行为的相似性意味着，在许多集水研究中观察到的强示踪剂阻尼和长旅行时间不是人工制品，而是反映了长时间尺度上沃茨的储存和混合。版权所有（C）2010约翰威利父子有限公司
Time series of chloride concentrations and oxygen-18 isotopic ratios are widely used for tracing catchment storage and mixing processes and for inferring catchment travel-time distributions. However, neither chloride nor oxygen-18 is an ideal hydrologic tracer: chloride concentrations in streamwater can be affected by dry deposition, evapoconcentration and biogeochemical cycling, and water isotopes can be fractionated by evaporation. One way to test the reliability of these tracers is to determine whether, despite artifacts such as these, both tracers lead to similar inferences when measured in the same catchment. Here, we compare chloride and oxygen-18 time series in the Girnock and Allt' a Mharcaidh catchments in Scotland. Semivariograms and power spectra for both tracers exhibit similar patterns of fluctuation damping, implying that the travel-time distributions of the two tracers have similar shapes. Fluctuations of both tracers are strongly damped in streamflow compared to precipitation, implying that these catchments integrate tracer signatures over many different storm events. Streamflow fluctuations of both tracers are more strongly damped at the Allt' a Mharcaidh catchment, implying longer storage and greater mixing of waters of different ages, compared to the Girnock catchment. At both sites, streamflow fluctuations of oxygen-18 are more strongly damped, relative to precipitation, than those of chloride, leading to estimates of mean travel times that are longer, by a factor of 2-3, for oxygen-18 than for chloride. The greater variability of chloride compared to oxygen-18 may arise from spatially and temporally varying occult deposition and evapoconcentration. Nonetheless, the similarities in the behaviour of the two tracers imply that the strong tracer damping and long travel times that have been observed in many catchment studies are not artifacts, but instead reflect storage and mixing of waters over long time scales. Copyright (C) 2010 John Wiley & Sons, Ltd.