Distribution Patterns of Native Sulfate Displaced by Respective Pore Volumes of Oxalic Acid in Cecil Bt Soil

In this investigation we tried to investigate the effect of oxalic acid on the fate of native sulfate in Bt soil that contained a high kaolinitic clay by observing the distribution of two anions using soil column under the given competitive adsorption between displaced and displacing anions. To do this, the soil columns uniformly packed to a bulk density of 1.25 $g/cm^3$ with Cecil Bt soil were disected and analyzed the amounts of sulfate and oxalic acid both in solution and solid phases after flowing the designated pore volumes of oxalic acid The results showed that two sets of curves-nonlinear (> $10^3M$) and linear (> $10^3M$) curves where the solution of oxalic acid was not adiustet while the approaches to the plateau were slow when pH of oxalic acid was adjusted to 5. The cumulative amount of sulfate desorbed by successive addition of oxalic acid was nonlinearly approached to the plateau at the concentration of $10^3M$ or greater, indicating that the number of addition of oxalic acid increased with decreasing order of oxalic acid. However, the plateau did not obtain where the concentration of oxalic acid were less than $10^4M$, showing a linear increase. Therefore, we may conclude that the rate-limited desorption was involved as the concentration of oxalic acid decreased.