Study of trace metal partitioning between soil–EDTA extracts and Chelex-100 resin

The partitioning of Cu, Cd and Pb in EDTA leachates from a variety of soils, to Chelex-100 resin was investigated. A series of experiments was conducted to optimise method for the trace element sorption on Chelex-100 in 13 unpolluted soils from Burgundy, France. The extraction efficiency of Chelex-100 varied depending on soil carbonate contents. The largest percentage of trace metals was transferred to the resin in non-calcareous samples, while the resin was used in its Ca form. This technique was able to trap up to 98% of Cu, 72% of Cd and 28% of Pb in non-calcareous soil leachates. The fraction of metal transferred to the Chelex-100 in calcareous soil extracts was 40% less than those in non-calcareous ones. Besides, a kinetic procedure was developed to study the kinetic of cation exchange from soil–EDTA leachates onto solid-phase resin. The soil calcium content was found to be a controlling factor in the Cu sorption on the Ca–Chelex. Two different kinetic behaviours were observed in calcareous and non-calcareous soils. The dissociation rate of Cu in non-calcareous soil extracts was 10 times higher than that in calcareous ones. Application of kinetic model indicated the presence of two components associated to Cu in non-calcareous samples. This was discussed in terms of metal sorption mechanism from soil solution onto chelating resin.