Heterogeneity is a common feature of aquifers and plays an important role in the efficiency of remediation of groundwater contamination. Pore-scale heterogeneity is an important control on governing mass transport and chemical/biological reactions in reactive transport processes, but quantitative characterization and systematic assessment of this property has been limited. In this study, a pore-scale-heterogeneity-synthetic index was developed to quantitatively characterize pore-scale heterogeneity of unconsolidated porous media. It was an attempt to systematically assess pore-scale heterogeneity based on statistical analysis of pore-structure characterization parameters. Pore network extraction was conducted to assist in quantifying the pore structure based on X-ray μ-CT imaging data. The quantitative characterization of pore structure provided input data for a comprehensive evaluation model. Two alternative weighting approaches—principle component analysis and the entropy method—were utilized to calculate the weight of each evaluation indicator. Based on the comprehensive evaluation results, a guideline for classification of pore-scale heterogeneity was proposed by cluster analysis. Further analysis indicated that particle size, shape, and distribution had a potential influence on pore-scale heterogeneity. The bigger, more irregular particles, as well as a wider particle-size distribution, were conducive to forming high heterogeneity at pore scale. The obtained results will provide useful information and theoretical support for pore-scale heterogeneity characterization and understanding of the pore-scale mechanisms of reactive transport processes.

非均质性是含水层的共同特征，并且在修复地下水污染的效率中起着重要作用。孔尺度异质性是控制反应性输运过程中的质量输运和化学/生物反应的重要控制，但是对该特性的定量表征和系统评估受到限制。在这项研究中，开发了孔隙尺度非均质性综合指数，以定量表征未固结多孔介质的孔隙尺度非均质性。这是基于对孔结构表征参数的统计分析，系统地评估孔尺度异质性的尝试。进行孔网提取以帮助基于X射线μ-CT成像数据量化孔结构。孔结构的定量表征为综合评估模型提供了输入数据。两种替代加权方法（原理成分分析和熵方法）用于计算每个评估指标的权重。在综合评价结果的基础上，提出了通过聚类分析对孔隙尺度异质性进行分类的指南。进一步的分析表明，粒径，形状和分布对孔尺度的异质性具有潜在的影响。更大，更不规则的颗粒以及更宽的粒径分布，有利于在孔尺度上形成高度的异质性。