Determination of Diffusion-Dispersion Coefficient and Retardation Factor in Saline Soils(Thai)

Abstract

The determination of diffusion-dispersion coefficient (D) and retardation factor (R) in saline soils of Ban Napear, Muang Pear subdistrict, Banphai district, Khon Kaen province can be simulated by mass transport through unsaturated zone modeling. This experiment simulated the solute transport by capillary force through
soil pores in a PVC column with diameter 0.05 meter and three lengths i.e. 1.0, 1.5 and 2.0 meters. The dry
soil filled tubes were immersed in salt solution (NaCl) of 150 mS cm-1 in bucket containers. Both water content (
θ (xi,t)) and salt concentration (C(xi,t)) of the soil was measured after 1, 7, 14, 21 and 30 days. The determination of diffusion-dispersion coefficient (D) and retardation factor (R) were fitted by the solute transport equation of Danckwert. The best fitting graph after comparism with experimental results should be selected. The diffusion-dispersion coefficient (D) of sandy loam soil in footslope (St1) was 0.0067 m2 day -1 and the retardation factor

(R) was 0.2970. In sandy loam soil in shoulder (St2) was 0.0094 m2 day-1 and the retardation factor (R) was 0.2860. Sandy clay loam soil in toeslope (St3) had diffusion-dispersion coefficient (D) of 0.0012 m2 day-1 and the retardation factor (R) was 0.1140. Hence, the diffusion-dispersion coefficient (D) and retardation factor (R) were lower in fine textured soil.