Abstract This paper presents analytical solutions for predicting one-dimensional contaminant diffusion in a four-layer sediment-cap system, which is typically encountered in subaqueous in-situ capping of contaminated sediments. The sediment-cap system is comprised of, from top to bottom, a layer of capping material (e.g., clean sand), a layer of reactive core mat (RCM), a layer of contaminated sediment and a layer of uncontaminated sediment. Two different bottom boundary conditions are considered, i.e., zero-concentration-gradient bottom boundary condition and zero-concentration bottom boundary condition, for which the method of separation of variables is used to obtain the analytical solutions. The extensively verified CST3 (Consolidation and Solute Transport 3) model is used to verify the proposed analytical solutions. Using the verified analytical solutions, parametric studies are conducted to investigate the effect of several important parameters on contaminant transport in the four-layer sediment-cap system. The results indicate that the cap thickness, the contaminated sediment thickness, the uncontaminated sediment thickness, the effect of RCM, and the RCM distribution coefficient have significant impact on contaminant diffusion in the four-layer sediment-cap system. The analytical solutions presented herein can be used to assist the design of subaqueous in-situ capping of contaminated sediments and to verify other numerical models.

中文翻译：

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水下原位封盖四层沉积盖系统污染物扩散解析解

摘要 本文提出了预测四层沉积物盖系统中一维污染物扩散的解析解，这通常在污染沉积物的水下原位盖层中遇到。沉积物盖系统从上到下由一层覆盖材料（例如，干净的沙子）、一层反应性芯垫（RCM）、一层受污染的沉积物和一层未受污染的沉积物组成。考虑了两种不同的底部边界条件，即零浓度梯度底部边界条件和零浓度底部边界条件，分别采用变量分离法求得解析解。广泛验证的 CST3（固结和溶质输运 3）模型用于验证建议的解析解。使用经过验证的解析解，进行参数研究，以研究几个重要参数对四层沉积盖系统中污染物迁移的影响。结果表明，盖层厚度、污染沉积物厚度、未污染沉积物厚度、RCM效应和RCM分布系数对四层沉积物盖系统污染物扩散有显着影响。本文提出的解析解可用于协助设计受污染沉积物的水下原位封盖并验证其他数值模型。污染沉积物厚度、未污染沉积物厚度、RCM效应和RCM分布系数对四层沉积盖系统污染物扩散有显着影响。本文提出的解析解可用于协助设计受污染沉积物的水下原位封盖并验证其他数值模型。污染沉积物厚度、未污染沉积物厚度、RCM效应和RCM分布系数对四层沉积盖系统污染物扩散有显着影响。本文提出的解析解可用于协助设计受污染沉积物的水下原位封盖并验证其他数值模型。