Fractionation and Soil-Plant Transfer of 241Am in Different Soil Types

Abstract

Monitoring the behavior of radioactive contaminants associated with military applications, nuclear power facilities, and interim storage of radioactive waste materials is of significant concern in radiological analysis. Four sequential extraction schemes (SES) for fractionation of 241Am were compared using five different types of soils, Vertisol, Cambisol, Chromic Luvisol, Eutric Fluvisol, and mixed urban soil, collected from different parts of Bulgaria. The results for the exchangeable 241Am were in a wide range and depended on the SES used. Soil 241Am varied from 0.5% to 6% in the exchangeable phase, from 0.5% to 35% in the carbonate phase, from 0.4% to 36% in the reducible phase (easily reducible and moderately reducible), from 3% to 17% in the oxidizable phase, and from 10% to 50% in the residual phase. After 100 d of contamination, around 50% of soil 241Am was permanently fixed in the residual phase. There was strong evidence that the preferable soil phase for 241Am was the carbonate phase. The transfer factor of 241Am in the soil-plant system depended on 241Am in the easily oxidizable phase (fulvic acid (FA)+humic acid (HA) phase). These confirmed the applicability of the National Institute of Standards and Technology (NIST) sequential extraction scheme for fractionation of soil 241Am since it includes extraction of FA+HA phase and then the carbonate phase.