Transport of chloride through water-saturated soil columns

Displacement experiments at constant temperature were carried out from loam and sandy loam soil columns of three different lengths i.e. 10, 20 and 30 cm with anions chloride and bromide. Incomplete mixing was clearly demonstr ated for both anions for slower pore water velocities. This limited mixing also revealed the lack of interconnections between major pore sequences. Th e breakthrough curves (BTCs) shifted towards right of one relative displace ment volume axis with increasing pore water velocity indicating more comple te mixing between conducting and slowly conducting zones. These experiments demonstrated the dominance of hydrodynamic dispersion for low pore waxer v elocities and convective transport for higher pore water velocities. Theref ore experiments showed that increasing pore water velocity decreases the ho ld back or immobile water in the column. The progressive attenuation of the initial concentration was demonstrated when the same amount of tracer was sent through the soil columns of different lengths. The experiments showed that solute arrival in effluent solution is ahead when soil texture was fin er. The present study revealed that during miscible displacement the degree of asymmetry in BTCs was a function of soil texture, pore water velocity, apparent diffusion coefficient and length of displacement.