Remobilization of ~(60)Co, ~(85)Sr, ~(137)Cs, ~(152)Eu, and ~(241)Am from a Contaminated Soil Column by Groundwater and Organic Ligands

摘要

The desorption rate of ~(60)Co, ~(85)Sr, ~(137)Cs, ~(152)Eu, and ~(241) Am from soil collected from Inshas disposal site in Egypt was investigated to understand the desorption and mobility of these radionuclides in the environment. Effect of a synthetic groundwater (GW) and the GW amended to 2 × 10~(-5) M of ethylenediaminetetraacetic acid (EDTA) or ethylenediaminediacetic acid (EDDA), GW+ETDA and GW+EDDA, respectively, was studied in flow-through experiments. These experiments were designed to compare the influence of EDTA relative to one of its degradation products that can exist in natural water, EDDA. First-order desorption and two-site first-order desorption equations were used to describe the time-dependent desorption data. The desorption rate for ~(85)Sr and ~(137)Cs was high in the first 50 h followed by a slow release suggesting that two different mechanisms involved. The trace metal removal was not completely reversible for all radionuclides tracers except for ~(85)Sr. The quantity of ~(85)Sr, ~(137)Cs, ~(152)Eu, and ~(241)Am desorbed from soil follows the order GW+EDTA > GW+EDDA > GW, while ~(60)Co gives unexpected trends where the effect of EDDA is twice as high as that of EDTA. This behavior was discussed based on the aqueous species distribution of ~(60)Co in both aqueous solutions.