Soil radiochromatography using 22Na, 85Sr, and 58Co

A laboratory study of radionuclide movement and adsorption in soil has been performed. A commercial, high-performance, liquid chromatography system, employing an ultraviolet adsorption detector, was supplemented with a real-time radiation monitor of the column effluent. Columns packed with various soils and their size separates were injected with 22Na, 85Sr, and 58Co using various CaCl2 solutions for eluting solvents to simulate groundwater. The near identical behavior of 85Sr and Ca allowed the elution volumes of the Sr peaks to be used for the calculation of the cation retention capacities of the soils which agreed with their measured cation exchange capacities. Treatment with NaOH increased the cation exchange capacity of one column by 50%. Acetone or sodium benzoate proved useful for measuring column void volumes using the ultraviolet detector because they eluted at exactly the calculated void volumes for all soil columns. Methods to measure a soil's retardation factor (R/sub d/) and distribution coefficient (K/sub d/) for each isotope from the experimental elution patterns were developed. Excellent simulations of the elution peaks were attained using the Lapidus-Amundson equation, which required inputs of flow rate, K/sub d/, bulk density, porosity, the dispersion coefficient, and column length. The factors determining the elution volume of either 22Na or 85Sr were the cation exchange capacity of the column and the concentration of Ca in the eluting solution. Elution of these isotopes was not affected by the presence of complexing organic acids, EDTA, or acidic and basic soil organic matter extracts. On the other hand, 58Co exhibited enhanced mobility when complexed with EDTA but not with other organic acids or soil extracts. A significant amount of 58Co was strongly adsorbed by the soils and could be removed only by washing with strong mineral acid