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首页> 外文学位 >Stochastic methods for modeling the transport of kinetically sorbing solutes in heterogeneous groundwater aquifers.
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Stochastic methods for modeling the transport of kinetically sorbing solutes in heterogeneous groundwater aquifers.

机译：用于模拟非均质地下水含水层中动态吸附溶质运移的随机方法。

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Heterogeneity is prevalent in aquifers and has an enormous impact on contaminant transport in groundwater. In addition to affecting the contaminant velocity, heterogeneity contributes to immobile water regions into which contaminants slowly diffuse. This diffusion effect can be modeled with the equations that describe rate-limited sorption, which is another important process in aquifers.; Moments of contaminant travel times can measure the effects of heterogeneity. The travel time variance measures both the spread of the contamination due to heterogeneity and the uncertainty in the arrival time due to the fact that a complete description of the subsurface is not available. Equations are derived for the temporal moments of contaminants experiencing rate-limited sorption or diffusion based on the temporal moments of conservative tracers. Conditioning on transmissivity measurements is incorporated, and the general equations are specified to the rate-limited sorption models found to be applicable in the literature.; Numerical simulations are an effective way to deal with heterogeneity directly by assigning different hydraulic property values to each numerical grid block. Because hydraulic properties vary on many scales, but they cannot be sampled exhaustively and the number of numerical grid blocks is limited by computational considerations, dispersion tensors are required to model the dispersive effects of unmodeled heterogeneity. Ensemble average block-scale macrodispersion tensors account for all of the pertinent length scales and do not include the effects of heterogeneity modeled on the numerical grid. Numerical simulation results are presented showing that the tensors can be used to accurately model the spread of contaminants when limited measurements are available and hydraulic conductivity is modeled on a numerical grid with large blocks, resulting in less computational demand than typical numerical simulations. The tensors are derived for reactive contaminants with spatially variable retardation factors and for contaminants experiencing spatially uniform rate-limited sorption or diffusion. The applicability of the concept depends on the ratio of the transverse size of the contaminant plume to the size of the regions modeled with uniform hydraulic properties and on the portion of the plume asymmetry caused by small-scale variability. Results show that the concept is widely applicable.
机译：非均质性普遍存在于含水层中，并且对地下水中的污染物迁移具有巨大影响。除了影响污染物的速度以外，异质性还导致污染物在其中缓慢扩散的固定水区域。可以用描述速率限制吸附的方程来模拟这种扩散效应，这是含水层中的另一个重要过程。污染物传播时间的瞬间可以衡量异质性的影响。行程时间的变化既可以测量由于异质性引起的污染扩散，也可以测量到达时间的不确定性，这是由于无法获得地下的完整描述。基于保守示踪剂的瞬时矩，导出了污染物经历速率限制吸附或扩散的瞬时矩的方程。结合了透射率测量的条件，并为速率限制的吸附模型指定了通用方程式，发现该模型适用于文献。通过为每个数值网格块分配不同的水力特性值，数值模拟是直接处理非均质性的有效方法。由于水力特性在许多尺度上会发生变化，但是不能穷尽地对它们进行采样，并且数值网格块的数量受到计算考虑的限制，因此需要色散张量来模拟未建模异质性的色散效应。整体平均块尺度宏散度张量说明了所有相关的长度尺度，并且不包括在数值网格上建模的异质性影响。数值模拟结果表明，当可获得有限的测量值并且在具有大块的数值网格上对水力传导率进行建模时，张量可用于准确地建模污染物的扩散，从而导致比典型的数值模拟更少的计算需求。张量是针对具有空间可变延迟因子的反应性污染物和经历空间均一速率限制吸附或扩散的污染物而得出的。该概念的适用性取决于污染物羽流的横向尺寸与以均一的水力特性建模的区域的尺寸之比，以及取决于小规模变异性导致的羽流不对称部分。结果表明该概念是广泛适用的。

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