About 20 years ago the emphasis in soil chemistry research switched from studies of problems related to scarcities of plant nutrients to those arising from soil pollutants. The new problems have come about because of the excessive uses of fertilizers, the inputs from farm and industrial wastes, the widespread applications of anthropogenie xenobiotic chemicals, and the deterioration of soil structure resulting from certain modern agriculture practises. The International Society of Soil Science (ISSS) recognized these problems and challenges. A provisional Working Group was set up in 1978 to focus attention on soil colloids with a view to understanding better the interactions wh ich take place at their surfaces. It was recognized that these interactions are fundamental to problems of soil fertility, as weIl as to those of soil pollution. After the group had received the official support of ISSS at its 12th International Congress in New Delhi in 1982 it set as its priority the assembling and evaluation of information, relevant to the soil and environmental sciences, concerning the composition and structure of soil colloids. Prior to that aseries of Position Papers were published in the Bulletin of the International Society of Soil Science (Vol. 61, 1981) outlining the state of knowledge about the composition and properties of soil colloids.

Within the field of soil science, soil chemistry encompasses the different chemical processes that take place, including mineral weathering, humification of organic plant residues, and ionic reactions involving natural and foreign metal ions that play significant roles in soil. Chemical reactions occur both in the soil solution and at the soil part

S. Henin Versailles, France It was a pleasure for me to take part in the NATO Advanced Study Workshop for studies of 'Soil Colloids and their Associations in Soil Aggregates'. The meeting provided me with a welcome opportunity to renew acquaintances with respected colleagues in the various fields of Soil Science, to listen to their presentations, and be involved in discussions which were at the frontiers of the science which deals with the structures and the associations of the soil colloidal constituents. In my view the rapid advances in Soil Science, and the great benefits to agriculture from these, have their origins in the emerging understanding of the structures and the associations of the different soil colloids. It is clear that much research is still needed before the molecular details of the most important of the structures and of the interactions are fully understood. The associations between the soil colloids, and the manner in which they bind to or hold the other constituents of soils in aggregates is fundamental to soil fertility. and the Modem intensive agriculture leads to the degradation of soil structure subsequent loss through erosion of a resource that is vital for the production of food. This degradation is considered to result primarily from the biological oxidation of the indigenous soil organic matter, and from the failure to return to the soil sufficient organic residues to compensate for such losses.

This companion volume to Velde's Origin and Mineralogy of Clays deals with the role of clays in specific environmental issues, and is unique in its subject matter. Individual chapters are written by recognized international experts in their field, and cover such subjects as radioactive waste disposal, trace metals, soil quality and productivity, pesticides, landfill, fibrous minerals and health. The approach combines reviews with current research, making it an invaluable resource for students, researchers and practitioners alike.

"Provides comprehensive coverage of the structures, properties, and interactions of organo-clay complexes as well as their role in the origin of life. Presents current techniques in nuclear magnetic resonance, differential thermal analysis and thermogravimetry, visible spectroscopy, and infrared and thermal-infrared spectroscopy for the analysis of

The Role of Colloidal Systems in Environmental Protection describes the importance of colloids in many applications that contribute to environmental protection, including drinking water and wastewater treatment, heavy metal remediation, treatment of radioactive materials, corrosion, and energy conversion. Knowledge of the physical and chemical composition of colloids is important to understand and accurately model the relevant processes. The book familiarizes the reader with the technological features of the application of colloids in environmental protection, and provides chemical engineers, researchers, and scientists in academic and corporate communities with the latest developments in this field. Each chapter covers the whole spectrum of the relevant science, from the fundamentals to applications. - Provides the applied technological features of colloids in environmental protection - Gives insight into the use of bio-solid colloids as contaminant carriers - Covers the natural occurrence of biosurfactants in the environment and their applications - Provides information on the use of nanoparticles for environmental applications - Chapters written by recognized and respected experts in the field from all over the world

The soil is the medium through which pollutants originating from human activities, both in agriculture and industry, move from the land surfaces to groundwater. Polluting substances are subject to complex physical, chemical and biological transformations during their movement through the soil. Their displacement depends on the transport properties of the water-air-soil system and on the molecular properties of the pollutants. Prediction of soil pollution and restoration of polluted soils requires an under standing of the processes controlling the fate of pollutants in the soil medium and of the dynamics of the contaminants in the un saturated zone. Our book was conceived· as a basic overview of the processes governing the behavior of pollutants as affected by soil constituents and environmental factors. It was written for the use of specialists working on soil and unsaturated zone pollution and restoration, as well as for graduate students starting research in this field. Since many specialists working on soil restoration lack a back ground in soil science or a knowledge of the properties of soil pollutants, we have included this information which forms the first part of the book. In the second part, we discuss the partitioning of pollutants between the aqueous, solid and gaseous phase of the soil medium. The retention, transformation and transport of pollutants in the soils form the third section.