Complexing of Metals by Soil Organic Matter

Soil organic matter forms complexes with metals by ionexchange, surface adsorption, chelation, and complex coagulation and peptization reactions. Little is known concerning the nature of the ligands in polymeric components of soil organic matter which chelate metals, but carboxyl, hydroxy, and amide groups are probably involved. A number of low molecular weight compounds capable of chelating metals have been isolated from soils. Metallo‐organic matter complexes must be identified and characterized before unequivocal evidence for their formation in soils can be obtained.