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Kinetic studies of metal speciation using chelex cation exchange resin: application to cadmium, copper, and lead speciation in river water and snow.

Kinetic studies of the rate of uptake of the metal ions Cd, Cu, and Pb by the Chelex batch technique have been made on model solutions containing the metal ions and the complexants EDTA, NTA, and fulvic acid. The metal ions were quantitated by inductively coupled plasma mass spectrometry, and the rates of uptake of the metal ions were analyzed by the iterative deconvolution method. In the presence of an excess of EDTA or NTA, all the metal ion was complexed with the chelating agent, forming a slowly dissociating complex. In the presence of fulvic acid, these metals formed strongly bound complexes with a range of slow dissociation rates. The results reveal the importance of [fulvic acid]/[metal ion] ratio and, hence, the extent of occupation of binding sites in fulvic acid (a polyfunctional complexes