Transport Mechanisms of Sodium in Sandy Soil from Column Leaching Test

Wastewater from treatment of domestic sewage is being increasingly used in agricultural irrigation, and can generate many problems related to high sodium concentration. Thus, it is necessary to know the behavior of Na+ to perform more sustainable wastewater reuse in agricultural irrigation. In this sense, this research aimed to study the transport mechanisms of Na+ as well as the differences between various methods of determination of transport parameters i.e. hydrodynamic dispersion coefficient (Dh) and retardation factor (Rd). Column leaching tests were performed in undisturbed residual soils of the sandstones from Adamantina Formation. The results suggested retention of sodium as well as advective movement. Furthermore, values of Rd and Dh were very different between the various used methods. Probably, these differences relate to the characteristics of dual and macroporosity of the soil, affecting the water average linear velocity. Finally, the results showed that the use of transport parameters in modeling of contaminant transport should be done with caution, observing soil characteristics, the conceptual models and the limitations of the methods used.