Transport of heavy metals such as Cd is affected by several rate-limiting processes including adsorption and
desorption by exchange reactions in soils. In this study, column transport and batch kinetic experiments were
performed to assess Cd mobility in a double-layered soil with a reclaimed saline and sodic soil (SSS) as top
soil and macroporous granule (MPG) as a bottom layer. For individual soil layer having different physical and
chemical properties, Cd was considered to be nonlinear reactivity with the soil matrix in layered soils. The
dispersive equation for reactive solutes was solved with three types of boundary conditions for the interface
between soil layers. The adsorption of Cd with respect to the saline-sodic sandy loam and the MPG indicated
that the nature of the sites or the mechanisms involved in the sorption process of Cd was different and the
amounts of Cd for both of samples increases with increasing amounts of equilibrium concentration whereas
the amount of Cd adsorbed in saline-sodic sandy loam soil was higher than that in MPG. The results of
breakthrough curve indicating relative Cd retardation accompanied by layer material and sequence during
leaching showed that the number of pore volumes to reach the maximum relative concentration of 1 increased
in the order of MPG, SSS, and double layer of SSS-MPG. Breakthrough curves (BTCs) from column
experiments were well predicted with our double-layered model where independently derived solute physical
and retention parameters were implemented.