Time Behavior of Anomalous Solute Transport in Three‐Dimensional Cemented Porous Media

Abstract

We quantitatively explore and explain the different time behavior of anomalous solute transport in three‐dimensional (3D) porous media with different cementation degrees. We find that the temporal evolution of the breakthrough curves (BTCs), spatial moments and propagators representing the time behavior of the transport varies significantly in each case with rising cementation degree. For example, the early breakthrough and long tail in the BTCs are enhanced simultaneously when the cementation degree increases, implying that the solute transport is anomalous. Correspondingly, instead of both the first and second central moments growing linearly with time as described by the traditional advection‐dispersion equation (ADE), the relationship between the second central moment M2 and time gradually transitions from an approximate linear relationship into a nonlinear relationship. This indicates that the scale effect is enhanced in the porous media with larger cementation degree. In addition, the propagator is characterized by a more remarkable and more persistent stagnant concentration peak when the cementation degree rises. Our simulations also demonstrate that the CTRW model can capture the simulated BTCs and quantitatively predict the temporal evolution of the first two moments of the solute plume. Finally, we explain the mechanism of the different time behavior of solute transport via the characteristics of the flow field.Core Ideas Time behavior of solute transport varies radically with rising cementation degree. CTRW model can characterize the different time behavior of solute transport. The changing characteristics of flow field cause the different time behavior.