State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, Ministry of Ecology and Environment, 388 Lumo Road, Wuhan, 430074, China.
Hubei Key Laboratory of Yangtze River Basin Environmental Aquatic Science, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, 430074, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Sep;29(45):67953-67968. doi: 10.1007/s11356-022-20495-5. Epub 2022 May 7.
Analytical models of solute transport have been widely used to aid the understanding of the physical and chemical processes undergone by substances introduced in a layered aquifer system. However, in previous studies, the advection component of transport was assumed to be one dimensional, while also ignoring the mixing processes that occur in the inlet and the outlet reservoirs. In this study, new sets of models describing those mixing processes are presented. Beyond that, these models were integrated into already existing models and the result is a novel analytical model of solute transport in aquifer-aquitard systems. The novel analytical solution was derived by the Laplace transform method and the finite-cosine Fourier transform method under the mobile-immobile (MIM) framework. The calculations take into account: the longitudinal and vertical dispersion, the molecular diffusion and the horizonal and vertical advection components of solute transport, as well as first-order chemical reaction, in both the aquifer and the aquitard. A finite-difference solution of the model is tested against experimental data in order to critique its reliability. Results indicate that the numerical and analytical solutions of the new model match well with experimental data. This new model outperforms the previous models in terms of interpreting experimental data. The mixing old and new water in the reservoirs during solute transport in aquifer-aquitard systems is important. Global sensitivity analysis demonstrates that the output concentration of solute in the aquifer-aquitard system is most sensitive to the volume of water in the inlet reservoir. The contribution of the molecular diffusion effect to the total mass flux of the tracer cross the aquifer-aquitard interface is much smaller than the contribution of the dispersive and advective effects.
溶质运移的分析模型已被广泛应用于辅助理解物质在层状含水层系统中经历的物理和化学过程。然而，在以往的研究中，运移的平流分量被假设为一维的，同时忽略了在入口和出口储层中发生的混合过程。在本研究中，提出了新的模型来描述这些混合过程。除此之外，这些模型被集成到现有的模型中，结果是一个新的含水层-隔水层系统中溶质运移的分析模型。新的分析解是通过拉普拉斯变换法和有限余弦傅里叶变换法在可动-不可动（MIM）框架下推导出来的。该计算考虑了：纵向和垂直弥散、分子扩散以及溶质运移的水平和垂直平流分量，以及含水层和隔水层中的一级化学反应。模型的有限差分解与实验数据进行了对比，以评估其可靠性。结果表明，新模型的数值解和解析解与实验数据吻合良好。与以往的模型相比，该新模型在解释实验数据方面表现更好。在含水层-隔水层系统中溶质运移过程中，储层中新旧水的混合非常重要。全局敏感性分析表明，含水层-隔水层系统中溶质的输出浓度对入口储层中水的体积最为敏感。分子扩散效应对示踪剂穿过含水层-隔水层界面的总质量通量的贡献远小于弥散和平流效应的贡献。
