Solute Transportin Sand Columns as Affected by Effluent Surface Tension

Transport of nonreactive solutes in soils is principally controlled by soil properties, such as particle-size distribution and pore geometry. Surface tension of soil water yields capillary forces that bind the water in the soil pores. Changes in soil water surface tension by contaminants may affect flow of soil water due to decreased capillary forces, caused by lowered soil water surface tension. This study aimed at assessing solute transport in sand columns as affected by effluent surface tension. Miscible displacement （MD） tests were conducted on sand columns repacked with sands sieved from 2.0, 1.0, 0.5 and 0.25 mm screens. The MD tests were conducted with 0.05 M bromide solutions prepared using water with surface tension adjusted to 72.8, 64, 53.5 and 42 dyne/cm2. Obtained breakthrough curves were modeled with the convection-dispersion equation （CDE） model. Coefficient of hydrodynamic dispersion and pore-water velocity responded inconsistently across decreased particle-sizes and water surface tensions and this was attributed to non-uniform effect of lowered effluent surface tension on solute transport in different pore-size distribution.