Solutes in rivers often come from multiple sources, notably precipitation (above) and generation from the subsurface (below). The question of which source is more influential in shaping the dynamics of solute concentration cannot be easily addressed due to the general lack of input data. An analysis of solute concentrations and their dependence on discharge across 585 catchments in nine countries leads us to hypothesize that both the timing and the vertical distribution of the solute generation are important drivers of solute export dynamics at the catchment scale. We test this hypothesis running synthetic experiments with a tracer‐aided distributed hydrological model. The results reveal that the depth of solute generation is the most important control of the concentration‐discharge (C‐Q) relation for a number of solutes. Such relation shows that C‐Q patterns of solute export vary from dilution (Ca²⁺, Mg²⁺, K⁺, Na⁺, and Cl⁻) to weakly enriching (dissolved organic carbon). The timing of the input imposes a signature on temporal dynamics, most evident for nutrients, and adds uncertainty in the exponent of the C‐Q relation.

中文翻译：

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溶质生成深度是浓度-排放关系的主要控制因素

河流中的溶质通常来自多种来源，特别是降水（上方）和地下产生（下方）。由于普遍缺乏输入数据，因此很难轻易地解决哪个源对塑造溶质浓度动力学的影响更大。对9个国家585个流域中溶质浓度及其对排放的依赖性进行分析后，我们得出一个假设，即溶质生成的时间和垂直分布都是集水规模上溶质出口动态的重要驱动力。我们使用示踪剂辅助的分布式水文模型，通过综合实验来检验该假设。结果表明，溶质的产生深度是许多溶质的浓度-放电（C-Q）关系的最重要控制。²⁺，镁²⁺，K ⁺，钠⁺和Cl ^- ）至弱富集（溶解的有机碳）。输入的时间在时间​​动态上加了一个签名，对营养最明显，并增加了C-Q关系的指数的不确定性。