Influence of Grain Size Transition on Flow and Solute Transport through 3D Layered Porous Media

Abstract Soils and other geologic porous media often have contrasting grain size layers associated with a transition zone between layers. However, this is generally simplified to plane of zero thickness for modeling assumption, its influence has always been neglected in previous studies. In study, an approach combining deposition process random packing was developed generate 3D without consideration the zone. The direct numerical models solving flow concentration fields were implemented investigate on solute transport. Our results showed that although occupied 13.6% entire layered medium, it had little distribution velocity at scale medium. significant local field, which increased spatial variability varied velocity. This field could increase residence time delay breakthrough Although using both advection-dispersion equation (ADE) mobile immobile (MIM) fit curves (BTCs) transport through resulted trivial errors, ADE model failed capture induced by especially contrast, MIM shown be able It found mass transfer rate α, parameter model, significantly improved presence zone, while decreased as fraction increased. study emphasized can vary pore scale, hydraulic properties (e.g., conductivity) macroscale field.