14 The concentrations of weathering-derived solutes in rivers and their co-variance with 15 discharge are thought to reflect reactive-transport processes in hillslopes and to reveal 16 the sensitivity of solute fluxes to climatic change. It is expected that discharge-driven 17 changes in water transit times play some role in setting concentration-discharge (C-Q) 18 relationships, but knowledge gaps remain. To explore the specific role of changes in the 19 shape of the transit time distribution with discharge, we combine models to simulate C20 Q relationships for major cations and Si as example solutes with contrasting affinities 21 to partition into secondary phases. The model results are compared with an analysis of 22 C-Q relationships using the Global River Chemistry Database. 23 We find that changes in the shape of the transit time distribution with discharge 24 can produce a range of cation-Q and Si-Q relationships that encompasses most of the 25 range observed in real catchments, including positive Si-Q relationships and variable cation 26 to Si ratios. We find that C-Q relationships (characterized by power law exponents) can 27 remain approximately constant, even as the Damköhler Number (ratio of transport timescale 28 to reaction timescale) is varied over three orders of magnitude. So, in our model anal29 ysis, C-Q relationships are as sensitive to hydrologic variability as they are to reaction 30 rates. Additionally we find that, depending on the storage-discharge relationship, changes 31 in rainfall patterns can influence C-Q relationships. Altogether, our results suggest ways 32 in which C-Q relationships may be non-stationary in response to climatic change and/or 33 vary in space and time due to catchment hydrologic properties. 34

中文翻译：

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通过水传输时间分布形状的变化对河流浓度-流量关系的调制

14 河流中风化衍生溶质的浓度及其与 15 排放的协方差被认为反映了山坡中的反应性运输过程，并揭示了 16 溶质通量对气候变化的敏感性。预计排放驱动的 17 水传输时间变化在设置浓度-排放 (CQ) 18 关系方面发挥了一些作用，但知识差距仍然存在。为了探索随放电的传输时间分布的 19 形状变化的具体作用，我们结合模型来模拟主要阳离子的 C20 Q 关系和 Si 作为示例溶质，具有对比亲和力 21 以划分为第二相。模型结果与使用全球河流化学数据库对 22 个 CQ 关系的分析进行了比较。23 我们发现随流量 24 的传输时间分布形状的变化可以产生一系列阳离子-Q 和 Si-Q 关系，包括在实际流域中观察到的大部分 25 个范围，包括正 Si-Q 关系和可变阳离子26 与 Si 的比率。我们发现 CQ 关系（以幂律指数为特征）可以 27 保持近似恒定，即使 Damköhler 数（传输时间尺度 28 与反应时间尺度的比率）在三个数量级上变化。因此，在我们的模型分析 29 ysis 中，CQ 关系对水文变率的敏感度与对反应 30 速率的敏感度一样。此外，我们发现，根据储存-排放关系，降雨模式的变化 31 会影响 CQ 关系。共，我们的结果表明，CQ 关系可能因气候变化而不稳定和/或 33 因集水区水文特性而在空间和时间上发生变化的方式 32。34