Hydrodispersive characterization of two soils of São Francisco River Valley

Abstract

The hydrodispersive characterization of two soils: an Yellow Ultisol and a Vertisol, both from the region of São Francisco Valley, was performed through displacement experiments in soil column in the laboratory. The experiment consisted of displacement of a pulse of 1 pore volume of a 0.1 M KBr solution in saturated soil column under steady-state flow conditions. The hydrodispersive parameters (D, R) ware obtained by fitting the analytical solution of the convection-dispersion equation (CDE) and the two-region transport model - MIM (D, R, ? and ?) for the points of the experimental breakthrough curve. The soil dispersivity was found to be higher in the Vertisol than in the Yellow Ultisol, because of the higher aggregation of this soil. The retardation factor (R) represented the tracer interactions with the soils: anionic exclusion in the Vertisol and bromide retention in the Yellow Ultisol, due to the presence of iron-oxydes (Goethite). The CDE model presented a better performance than the MIM model, for fitting the bromide breakthrough curves in both soil columns, suggesting the absence of immobile water in the Yellow Ultisol and the Vertisol.