Roles of clay fraction in controlling behavior of pollutants, the chosen pollutants being mostly inorganic substances, in real sediment and soil systems have been reviewed. Since the knowledge of the claypollutant interaction in the real environment presently rather limited, we have attempted to collect the information from the roles of wider range of sediment/ soil constituents, which are considered to be relevant to those of clays and clay minerals. Emphasis has been laid on showing the importance of surface processes, as well as of chemical form of pollutants or their binding modes to the soil and sediment constituents.

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Tobermorite has been successfully synthesized from incineration fly ash prewashed repeatedly and preheated at 800°C by hydrothermal treatment in the presence of NaOH solution. The crystallization field of tobermorite was examined as a function of reaction temperature, time and NaOH concentration. It was found that tobermorites were reproducibly formed in all of the fly ash treated with NaOH at 180°C, and sodalite and cancrinite generated as minor phases, with increasing NaOH concentration and extending reaction time. The products including tobermorite exhibited the removal characteristics for Cs⁺ and NH₄⁺ ions.

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Four appropriate bottom structual codes for waste landfills in Japan were decided in 1998 by the Ministry of Public Welfare. In this code, “clay” is described as a soil material having lower degree of permiability. Such the caly material is practically thought to be soil materials mixed with bentonite.
Recently both compacted clay liners and geosynthetic clay liners have become to be used for constraction of waste landfills. By outlooking of various water insulation structures and methods, in this report it is mentioned why clay materials are used and how they are used. Leachates and dioxins closely related to the environmental problems are also described in connection with clay science.

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Characteristics of clay-humus complexes obtained by modified Tyulin's method in volcanic ash soils of Changbaishan and Wudalianchi, Northeast China, and influence of tropospheric eolian dust on composition of the clay-humus complexes were studied. Results were as follows:
1) In surface of volcanic ash soils of both the two places, clay-humus complexes were dominated by G₂. Ratios of G₀/G₂, G₁/G₂, G₀/(G₁+G₂) were low. The amount of G₁ complexes and the ratio G₁/G₂ increased with increasing influence of eolian dust. The influence of eolian dust decreased with depth of the soil pedon.
2) Both the two places, in surface of volcanic ash soils the highest amount of carbon was found in G₂ complexes. 64.0-96.2% of total carbon in Changbaishan soils and 42.7-76.9% in Wudalianchi soils were distributed in G₂ complexes. The carbon content of each kinds of complexes decreased with depth of soil pedon. Influence of eolian dust resulted in decrease of carbon content in G₂ and increase of carbon content in G₁ complexes for each horizons of a soil pedon.
3) All of fine-clay, middle-clay, coarse-clay and total clay content in complexes of the surface horizons of volcanic ash soils in both the two places showed a tendency of G₂>G₁>G₀. All the 3 kinds of complexes contained significantly higher amount of total clay in Wudalianchi soils than in Changbaishan soils. And for each horizons of a soil pedon, the clay content in G₁ complexes was determined by the clay content in soil, i. e., the clay content in G₁ complexes became high while the influence of eolian dust was strong.
4) Clay mineral composition of each complexes was as same that of soil. But the amount of 1.42 nm clay minerals and kaolinite in complexes of surface soil from Changbaishan C2 on which the influence of eolian dust was weak showed a tendency of G₂>G₁>G₀, the amount bf muscovite and/or illite, and feldspar in complexes showed a tendency of G₁>G₂>G₀. However, such tendencies became weaker with the depth of the pedon. Similar phenomenon was found up to the BC horizon of the pedon W3 which was strongly influenced by eolian dust.

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Bentonite, existing ubiquitously in soils and sediments, is widely used in the various fields. Interaction between bentonite and microbes has been investigated at floc (aggregates of clays and microbes) and ore collected from the Kasaoka Bentonite Mine, Okayama, Japan.
The floc consists of bentonite, algae, diatoms and bacteria. TEM observation of the algae after ultrasonic treatment for 30 min. shows that the algal cell walls are still covered with bentonite. The FT-IR spectrum of the sonicated algae supports that a cross-linking structure composed of Si-C and Si-O-C bonds are formed between bentonite and algal cell wall, which implies that bentonite-microbe interaction may have an organicinorganic complex compound.
The present studies have revealed that bentonite has a role of protection for microbial cells, with surrounding on the surface of the cells. Consequently, it is suggested that bentonite shields life from spill of the toxic materials, and that the bentonite-microbe interaction is necessary to be considered in buffer for waste disposal in terms of protection of ecosystem in the strata.

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