TRANSPORT OF EXCHANGEABLE CATIONS IN AN AGGREGATED CLAY SOIL

The objective of this study was to assess the applicability of the classical and mobile-immobile transport models for describing cation transport in soils. The transport of exchangeable cations for binary and ternary systems in an aggregated clay soil using miscible displacement methods was examined. Packed columns of aggregates of Sharkey soil (Vertic Haplaquept) were saturated with Ca. Pulses of Mg or Mg plus Na were applied to these columns, then eluted with Ca. Chloride was the accompanying anion. These leaching experiments were conducted at constant and variable total solution concentrations. Experimental leaching data were compared with predicted breakthrough curves obtained using the classical (or one-region) and mobile/immobile water (or two-region) transport models. The two-region model offered no improvement over predictions obtained using the one-region model.