Radionuclide transport under changing soil salinity conditions

This paper presents experimental measurements and computer simulations of strontium-85 movement through laboratory soil columns. There are two primary objectives of the work. The first is to examine the enhanced leachability of strontium-85 when the soil salinity is raised. The second is to compare the ability of two solute transport models to describe this phenomena. The experiment consisted of injecting a pulse of what will be termed a low salt solution spiked with strontium-85 to a soil column. The column was then leached with over eighteen pore volumes of the low salt solution resulting in no leaching of the strontium-85 from the column. The column was then leached with a high salt solution causing the rapid release of the strontium-85 within five to six pore volumes. The results demonstrate that strontium-85 is subject to greater mobility when the soil salinity is increased. This confirms the necessity of evaluating the soil salinity very carefully in modeling efforts. The results also indicate that batch Kd values, combined with column Kd values and parameters obtained by curve fitting procedures do a fairly good job in describing the snowplow effect. The comparison of the two models reveal insignificant differences when describing the movement of tritium and strontium-85 under high salinity conditions. There was a significant improvement, however, when the mobile-immobile water equations were used to describe the combined low salt-high salt experiment