The interactions between surface water and groundwater in river corridors lead to temporal fluctuations in subsurface water fluxes which have a critical role on solute transport dynamics. In this work, we develop a framework to analyze the relative impacts of different temporal frequencies of the flow field in a spatially heterogeneous aquifer on solute transport. Our analysis indicates that the advection-dispersion equation behaves as a low-pass filter by wiping out the effect of high-frequency velocity fluctuations on the first two spatial moments of the solute plume, namely its center of mass and spreading. The concepts discussed in the theoretical analysis are then applied to understand solute transport dynamics at the 300 Area of the Hanford site (USA) adjacent to the Columbia River. We examine the temporal behavior of the solute plume's spatial moments for different temporal frequencies utilizing geostatistical parameters estimated in the 300 Area. Due to the proximity to the Columbia river, groundwater fluxes at the Hanford site are highly dynamic resulting in a large range of characteristic temporal frequencies. Nonetheless, similar to the theoretical analysis, our results show that the effect of high-frequency fluctuations is filtered, with most of the solute transport dynamics being controlled by fluctuations characterized by a large characteristic period.

河道中地表水与地下水之间的相互作用导致地下水通量的时间波动，这对溶质运移动力学起着至关重要的作用。在这项工作中，我们开发了一个框架来分析空间非均质含水层中流场不同时间频率对溶质运移的相对影响。我们的分析表明，对流弥散方程通过消除高频速度波动对溶质羽流的前两个空间矩（即质心和扩散中心）的影响而充当低通滤波器。然后，将理论分析中讨论的概念应用于了解与哥伦比亚河相邻的汉福德工地（美国）300区域的溶质运移动力学。我们研究溶质羽流的时间行为 利用在300个区域中估算的地统计参数，获得不同时间频率的空间动量矩。由于靠近哥伦比亚河，Hanford站点的地下水通量是高度动态的，从而导致很大范围的特征时间频率。但是，类似于理论分析，我们的结果表明，高频波动的影响已被滤除，大多数溶质输运动力学受具有较大特征周期的波动控制。