The late emeritus professor Toshio Sudo of Tokyo University of Education had frequently mentioned the importance of research in clay mineralogy in ocean and sea. Sudo suggested that the study of glauconite by Takahashi and Yagi initiated marine clay mineralogy in Japan. After the world war second, study on clay mineralogy in marine sediments has been started by the disciples of the Sudo school. Oinuma and Kobayashi have greatly developed the study of clay minerals in marine sediments under the guidance of Sudo. In this review, the author describesa brief history of the progress in marine clay mineralogy in Japan.

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Some future trends in the areas of chemistry of clay minerals are discussed on the basis of recent developments. Research trends on basic research will include syntheses of clay minerals based on atomic and molecular scale design. Basic problems related to characterization as well as clay physics will be major concerns for future clay science. Chemical and physical interactions of clays with water and many other chemical species and their dynamics will be developed further. Biological implications related to clays will also be investigated more extensively. Novel materials based on nanotechnology, biochemical and medical applications, environmental aspects should also be emphasized. The society should lead new areas covering interdisciplinary and crossdisciplinary fields.

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Molecular dynamics (MD) simulations have been performed to investigate the elasticproperties of a single layer of beidellite. NVT or NPT ensemble is selected at 300 K in which N (number of atoms in a basic cell), T (temperature) and V (volume of the basic cell) or P (pressure) are kept constant, respectively. The total freedom of atomic motions was allowed by applying the atom-atom pair interaction model. The size of a single clay layer was reduced gradually along either the aor b-axis to the final contraction of 0-45% in the MD simulations. It has been observed that a single clay layer takes a curved form under such external force. The effect of water molecules existing around a clay layer was investigated under the same conditions.

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Adsorbed cadmium (Cd) in a smectitic paddy soil was extracted with dilute nitric acid solutions and the factors controlling the extractability of Cd was evaluated with the aid of a simple numerical model to which cation exchange and surface complexation reactions were incorporated.
Cd was extracted from a paddy soil containing 6.8mg kg^-1 of total adsorbed Cd with 0 to 100 mmol L^-1 nitric acid solutions at a solution: soil ratio of 50m L: 10g. The extraction percentage increased as nitric acid concentration increased, i.e., from 5% at 5 mmol L^-1 to 95% at 100 mmol L^-1, whereas extracting time didnot significantly affect the extraction percentage. The model predicted the trend of the extraction percentage qualitatively and suggested that the cation exchange sites on layer silicate minerals are the major Cd retention sites particularly when the extracting acid concentration was high. However, the model prediction was far less than the experimental values, indicating possible role of aluminum ions dissolved from soil minerals in Cd-exchange on layer silicate minerals.

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