Influence of soluble organic matter on cadmium mobility in model compounds and in soils

Abstract

The role of soluble organic matter on the mobility of cadmium in model compounds and soils is discussed. For model compounds, a simple predictive model is proposed to describe the competition between metal adsorption and the formation of complexes in the solution, using conditional constants to predict the adsorption behaviour of metallic cations in the presence of an organic ligand. Experimental results are presented using a clay mineral and ethylenediaminetetraacetic acid as organic ligand to assess this model for cadmium. Soil experiments are also presented to illustrate the influence of soluble complexing organic matter on the mobility of cadmium. In this instance, mobility is shown to depend on three interactive parameters: pH, oxidation–reduction reactions and formation of complexes.