Earth and Environmental Sciences Division, Los Alamos National Laboratory, EES-16, T003, Los Alamos, NM 87545, United States.
Chemosphere. 2013 Apr;91(3):248-57. doi: 10.1016/j.chemosphere.2012.10.105. Epub 2012 Dec 20.
Aquifer heterogeneity controls spatial and temporal variability of reactive transport parameters and has significant impacts on subsurface modeling of flow, transport, and remediation. Upscaling (or homogenization) is a process to replace a heterogeneous domain with a homogeneous one such that both reproduce the same response. To make reliable and accurate predictions of reactive transport for contaminant in chemically and physically heterogeneous porous media, subsurface reactive transport modeling needs upscaled parameters such as effective retardation factor to perform field-scale simulations. This paper develops a conceptual model of multimodal reactive mineral facies for upscaling reactive transport parameters of hierarchical heterogeneous porous media. Based on the conceptual model, covariance of hydraulic conductivity, sorption coefficient, flow velocity, retardation factor, and cross-covariance between flow velocity and retardation factor are derived from geostatistical characterizations of a three-dimensional unbounded aquifer system. Subsequently, using a Lagrangian approach the scale-dependent analytical expressions are derived to describe the scaling effect of effective retardation factors in temporal and spatial domains. When time and space scales become sufficiently large, the effective retardation factors approximate their composite arithmetic mean. Correlation between the hydraulic conductivity and the sorption coefficient can significantly affect the values of the effective retardation factor in temporal and spatial domains. When the temporal and spatial scales are relatively small, scaling effect of the effective retardation factors is relatively large. This study provides a practical methodology to develop effective transport parameters for field-scale modeling at which remediation and risk assessment is actually conducted. It does not only bridge the gap between bench-scale measurements to field-scale modeling, but also provide new insights into the influence of hierarchical mineral distribution on effective retardation factor.
含水层非均质性控制着反应性迁移参数的时空变异性，对地下水流、迁移和修复的模拟有重要影响。上推（或均匀化）是一种用均匀域替代非均匀域的过程，使得两者再现相同的响应。为了对化学和物理非均质地多孔介质中污染物的反应性迁移进行可靠和准确的预测，地下反应性迁移建模需要上推参数，如有效阻滞因子，以进行现场尺度的模拟。本文为层次非均质地多孔介质的反应性迁移参数的上推开发了一种多模式反应性矿物相的概念模型。基于该概念模型，从三维无界含水层系统的地质统计学特征推导出了导水率、吸附系数、流速、阻滞因子的协方差以及流速和阻滞因子之间的交叉协方差。随后，使用拉格朗日方法，推导出了描述时空域中有效阻滞因子的尺度效应的尺度相关解析表达式。当时间和空间尺度变得足够大时，有效阻滞因子近似为其复合算术平均值。导水率和吸附系数之间的相关性会显著影响时空域中有效阻滞因子的值。当时间和空间尺度相对较小时，有效阻滞因子的尺度效应相对较大。本研究为实际进行修复和风险评估的现场尺度建模提供了一种实用的方法来开发有效输运参数。它不仅弥合了从台架测量到现场建模的差距，而且还深入了解了分层矿物分布对有效阻滞因子的影响。
