CD-113-NMR OF MODEL COMPOUNDS FOR THE STUDY OF METAL-HUMUS INTERACTION

NMR spectra were measured in solution for a series of compounds modell ing the interaction of cadmiuun(II) with the humic substances of the s oil. From the results it appears that the metal binding site is predom inantly the carboxylate group. Nevertheless the downfield shift of cad mium (II) fulvate suggests that functional groups (e.g. neutral N and S donor groups) other than carboxylates may be involved in cadmium coo rdination. The Cd-113 chemical shift is a sensitive probe of the compl exing ability of the various ligands and can be used as an analytical tool in the study of the interaction of this metal with the soil organ ic matter.