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

Abstract

The desorption rate of 60Co, 85Sr, 137Cs, 152Eu, and 241Am 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 × 10−5M 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 85Sr and 137Cs 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 85Sr. The quantity of 85Sr, 137Cs, 152Eu, and 241Am desorbed from soil follows the order GW+EDTA > GW+EDDA > GW, while 60Co 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 60Co in both aqueous solutions.