Die Bodenkultur - Journal for Land Management, Food and Environment
M. K. Shukla, F. J. Kastanek and D. R Nielsen:
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 demonstrated for both anions for slower pore water velocities. This limited mixing also revealed the lack of interconnections between major pore sequences. The breakthrough curves (BTCs) shifted towards right of one relative displacement volume axis with increasing pore water velocity indicating more complete mixing between conducting and slowly conducting zones. These experiments demonstrated the dominance of hydrodynamic dispersion for low pore water velocities and convective transport for higher pore water velocities. Therefore experiments showed that increasing pore water velocity decreases the hold 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 finer. The present study revealed that during miscible displacement the degree of asymmetry in BTCs was a function of soil texture, pore water velociry, apparent diffusion coefficient and length of displacement.
Key words: Breakthrough curves, Dispersion, Convective transport, Exclusion, Attenuation, Hold back, Apparent diffusion coefficient.