| Abstract: | Formation and properties of amorphous clay constituents in soils of the temperate-humid climate region A review of literature and of some own work was given on formation and properties of amorphous clay constituents which occur along with crystalline clay minerals in soils. By that the importance of soil amorphous material with respect to pedologic-agricultural and social-environmental problems was tried to emphasize. At the beginning some clarification of the different terms used for inorganic amorphous clay constituents and a sort of difinition of the different kinds of amorphous materials seemed to be evident. Then, the occurence and the formation of amorphous material in soils of the temperate-humid climate region was commentated. As a result of this it was stated that amorphous clay constituents occur mainly as coatings on negatively charged surfaces of crystalline layer silicates. From the grouping of amorphous substances around negatively charged cores (layer silicates or AlIV-cores in allophanic soils, respectively) it was deduced that the organisation of amorphous clay constituents and allophanes as well as synthetic aluminosilicates might be due to an unique structural principle, which was tried to explain more detailed. The methods used for determination of amorphous materials, especially allophanes, were discussed. Since the determination of amorphous clay constituents by chemical dissolution techniques is ambiguous with respect to soils containing different weathering stages of crystalline layer silicates as well, some suggestions were made for characterizing amorphous substances in soils by cation exchange and anion adsorption properties. Finally the importance of exchange-reactions caused by specific adsorption of ions and molecules (e.g. nutrients and pesticides) was indicated. Furthermore, the possibility was mentioned that harmful environmental substances might be bound (neutralized) and waste nutrients might be recycled by specific adsorption on amorphous soil constituents. |
