Environmental Chemistry is a relatively young science. Interest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet ab out the exact content and limits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives of Environmental Chemistry must be the study of the environment and of natural chemical processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment and chemical reactions occurring in the environment. The industrial activities of man have given a new dimension to Environmental Chemistry. We have now synthesized and described over five million chemical compounds and chemical industry produces about hundred and fifty million tons of synthetic chemicals annually. We ship billions of tons of oil per year and through mining operations and other geophysical modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas of up to 15 million inhabitants produce large quantities of waste in relatively small and confined areas. Much of the chemical products and was te products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cyc1es and reactions and frequently lead to interference and disturbance of natural systems.

Environmental Chemistry is a relatively young science. Interest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and limits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives of Environmental Chemistry must be the study of the environment and of natural chemical processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment and chemical reactions occurring in the environment. The industrial activities of man have given a new dimension to Environmental Chemistry. We have now synthesized and described over five million chemical compounds and chemical industry produces about hundred and fifty million tons of synthetic chemicals annually. We ship billions of tons of oil per year and through mining operations and other geophysical modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas of up to 15 million inhabitants produce large quantities of waste in relatively small and confined areas. Much of the chemical products and waste products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cycles and reactions and frequently lead to interference and disturbance of natural systems.

Development of environmentally friendly products gains an increasing - portance in science and in industry. While product development was strongly dedicated to achieve quality, cost and time targets, environmental issues indirectly had always been under consideration by engineers, see Fig. 1. Furthermore a methodology for the development of environm- tally sound products was missing. Despite of significant progress in using computer aided tools for product development and design, environmental aspects were attended. Computer aided tools typically do not include methods for considering environmental issues enabling the designer to - sess a product's environmental effects. Fig. 1. Vision of Environment as a key target for product development v vi Preface Product related environmental issues are getting more and more political and public awareness. Development of environmentally friendly products has become an action item for both, politics and industry (UNFCCC 1997). Energy consumption is on the agenda and covers pollution and resource saving. Typical topics of directives of the European Union are waste, noise, air pollution, water, nature and biodiversity, soil protection, civil protection and climate change. After the translation into national law the development of environmentally friendly products is a basic approach to contribute to the fulfilment of the topics mentioned above. In the European Community a "Communication from the Commission to the Council and the European Parliament" on "Integrated Product Policy" was adopted on th 18 June 2003 (EC 2003).

This monograph consists of manuscripts submitted by invited speakers who participated in the symposium "Industrial Environmental Chemistry: Waste Minimization in Industrial Processes and Remediation of Hazardous Waste," held March 24-26, 1992, at Texas A&M University. This meeting was the tenth annual international symposium sponsored by the Texas A&M Industry-University Cooperative Chemistry Program (IUCCP). The program was developed by an academic-industrial steering committee consisting of the co-chairmen, Professors Donald T. Sawyer and Arthur E. Martell of the Texas A&M University Chemistry Department, and members appointed by the sponsoring companies: Bernie A. Allen, Jr., Dow Chemical USA; Kirk W. Brown, Texas A&M University; Abraham Clearfield, Texas A&M University; Greg Leyes, Monsanto Company; Jay Warner, Hoechst-Celanese Corporation; Paul M. Zakriski, BF Goodrich Company; and Emile A. Schweikert, Texas A&M University (IUCCP Coordinator). The subject of this conference reflects the interest that has developed in academic institutions and industry for technological solutions to environmental contamination by industrial wastes. Progress is most likely with strategies that minimize waste production from industrial processes. Clearly the key to the protection and preservation of the environment will be through R&D that optimizes chemical processes to minimize or eliminate waste streams. Eleven of the papers are directed to waste minimization. An additional ten papers discuss chemical and biological remediation strategies for hazardous wastes that contaminate soils, sludges, and water.

Environmental Chemistry is a relatively young science. Interest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and limits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives of Environ mental Chemistry must be the study of the environment and of natural chemical processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment and chemical reactions occurring in the environment. The industrial activities of man have given a new dimension to Environ mental Chemistry. We have now synthesized and described over five million chemical compounds and chemical industry produces about hundred and fifty million tons of synthetic chemicals annually. We ship billions of tons of oil per year and through mining operations and other geophysical modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas of up to 15 million inhabitants produce large quantities of waste in relatively small and confined areas. Much of the chemical products and waste products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cycles and reactions and frequently lead to interference and disturbance of natural systems."

1. 5 REFERENCES 127 7 DIGITAL TERRAIN 129 1. 1 INTRODUCTION 129 1. 2 DRAINAGE NETWORK 130 1. 3 DEFINITION OF CHANNEL NETWORKS 135 1. 4 RESOLUTION DEPENDENT EFFECTS 138 1. 5 CONSTRAINING DRAINAGE DIRECTION 141 1. 6 SUMMARY 145 1. 7 REFERENCES 146 8 PRECIPITATION MEASUREMENT 149 1. 1 INTRODUCTION 149 1. 2 RAIN GAUGE ESTIMATION OF RAINFALL 151 ADAR STIMATION OF RECIPITATION 1. 3 R E P 155 1. 4 WSR-88D RADAR CHARACTERISTICS 167 1. 5 INPUT FOR HYDROLOGIC MODELING 172 1. 6 SUMMARY 174 1. 7 REFERENCES 175 9 FINITE ELEMENT MODELING 177 1. 1 INTRODUCTION 177 1. 2 MATHEMATICAL FORMULATION 182 1. 3 SUMMARY 194 1. 4 REFERENCES 195 10 DISTRIBUTED MODEL CALIBRATION 197 1. 1 INTRODUCTION 197 1. 2 CALIBRATION APPROACH 199 1. 3 DISTRIBUTED MODEL CALIBRATION 201 1. 4 AUTOMATIC CALIBRATION 208 1. 5 SUMMARY 214 1. 6 REFERENCES 214 11 DISTRIBUTED HYDROLOGIC MODELING 217 1. 1 INTRODUCTION 218 1. 2 CASE STUDIES 218 1. 3 SUMMARY 236 1. 4 REFERENCES 237 12 HYDROLOGIC ANALYSIS AND PREDICTION 239 1. 1 INTRODUCTION 239 x Distributed Hydrologic Modeling Using GIS 1. 2 VFLO (TM) EDITIONS 241 1. 3 VFLO (TM) FEATURES AND MODULES 242 1. 4 MODEL FEATURE SUMMARY 245 1. 5 VFLO (TM) REAL-TIME 256 1. 6 DATA REQUIREMENTS 258 1. 7 RELATIONSHIP TO OTHER MODELS 259 1. 8 SUMMARY 260 1.

The term "hazardous wastes" covers a wide range of disused products and production wastes generated not only in industrial sectors, but also in all areas of everyday life. Hazardous wastes are to a large extent shipped by sea to third countries for recycling or disposal. While the procedural requirements for such movements are laid out in the 1989 Basel Convention, explicit rules of responsibility and liability for resulting damages are neither provided by the Basel Convention nor by other international conventions. The Liability Protocol to the Basel Convention of 1999 has not yet entered into force. This book examines the existing rules of responsibility and liability applying to States and private persons and outlines the conditions under which liability may be incurred. Subsequently, the advantages and shortcomings of the 1999 Liability Protocol are analyzed. Although this Protocol faces substantial political headwind, from a legal perspective it includes principally useful and reasonable approaches and should therefore be ratified.

Solid waste management is currently a major issue worldwide with numerous areas reaching critical levels. Many developing countries and countries in transition still miss basic waste management infrastructure and awareness. It is here that many of the solid waste management problems and challenges are currently being faced. As such, waste-to-energy (WTE) consists of a proven and continuously developing spectrum and range of technologies in a number of (mostly) developed countries. However, it's integration in developing countries and systems in transition is often faced with scepticism and a complex set of barriers which are quite unique and differ greatly from those where WTE has been validated and applied over the years. Waste-to-Energy: Opportunities and Challenges for Developing and Transition Economies will address this issue both theoretically and using concrete examples, including: * contributions from numerous scholars and practitioners in the field, * useful lessons and rules of thumb, * both successful and failed cases, and * real-life examples and developments. Waste-to-Energy approaches this dynamic aspect of environmental engineering and management in a methodical and detailed manner making it an important resource for SWM planners and facility operators as well as undergraduate and post graduate students and researchers.

Water reuse management is one of the challenges all water scarce countries have to deal with in the coming decades. The present book highlights non-conventional solutions within the field of wastewater treatment and reuse predominantly for professionals and decision makers. It focuses on technologies which are reliable, sustainable, low cost and suitable for rural and sub urban areas. In addition, particularly innovative on-site concepts are presented.

Water - and its governance - is becoming a global concern partly because it is turning into a goods in short supply, with devastating effects on literally billions of people, but also because it is the "carrier" ofglobal warming; whether through irregular weather patterns or through flooding, water is how global warming will be 'felt'. The lion's share of the globally available fresh water resources is to be found in transboundary systems. In spite of its significance, the generated knowledge on how to deal with transboundary waters is weak and leaves policy makers with seemingly unavoidable, trade-off dilemmas and prioritizations, often with detrimental effects. In order to disentangle this predicament this volume works with one case: the Lower Mekong Basin and covers state-of-the-art academic and practitioners' knowledge and hence appeals to a wide audience. The topic this volume addresses is situated in the nexus ofan IR- (International Relations) approach focussing on transboundary politics and its inclination to remain within the sphere of state sovereignty and national interest on the one hand, and Development studies, with its imperatives on participation, planning, and intervention, on the other.The dilemma, we argue, of better understanding transboundary water management lies in how to understand how these two rationalities can be simultaneously nurtured.
"Audience: "This book will be relevant to scholars, as it provides cutting-edge research, and students, since it covers the primary debates in the field, interested in resource management, regional politics, and development issues in the area. It also addresses the global debate on transboundary water management and presents an in-depth case of one of the globally most sophisticated attempts at pursuing sustainable river basin management. Finally, practitioners and policymakers would benefit greatly because all contributions have explicit policy relevance, launching suggestion on improvements in water management."

This book is based on an international meeting organized by the University of Tokyo and the University of Rochester, and is published as one belonging to the series of Rochester International Conferences in Environmental Toxicity. The meeting on "Advances in Mercury Toxicology" was held at the University of Tokyo on August 1 to 3, 1990. The invited papers are published in this book along with an "Overview" chapter that was written by the editors at a meeting held at the University of Rochester on August 1 to 2, 1991. The purpose of the meeting was to assemble leading scientists to discuss their most recent findings on the toxicology of mercury. The time was opportune. Considerable progress has been made on the environmental fate and toxicology of mercury. Recent findings have given new insight into the global model for mercury. Transport in the atmosphere extends great distances resulting in pollution of lakes and rivers far distant from the source of mercury release. The process of methylation leads to accumulation of methylmercury in fish and thus in the human diet. New evidence indicates that acid rain and the impoundment of water for hydroelectric purposes affects the methylation and bioaccumulation processes resulting in higher levels of methylmercury in fish.

There is an extremely voluminous literature on radioactive waste and its disposal, much in the form of government-sponsored research reports. To wade through this mountain of literature is indeed a tedious task, and it is safe to speculate that very few, if any, individuals have the time to examine each report that has been issued during the preceding ten years. This book attempts to summarize much of this literature. Further, many workers in the geosciences have not received training in the nuclear sciences, and many nuclear scientists could be better versed in geology. In this book an attempt is made to cover some background material on radioactive wastes and geotoxicity that may not be an integral part of a geologist's training, and background material on geology and geochemistry for the nuclear scientist. The geochemical material is designed for both the geoscientist and the nuclear scientist. There is no specific level for this book. Certainly, it should be useful to advanced undergraduates and graduates studying geology and nuclear science. It does not pretend to cover a tremendous amount of detail in all subjects, yet the references cited provide the necessary source materials for follow-up study. It is my intention that the reader of this book will have a better, broader understanding of the geochemical aspects of radioactive waste disposal than is otherwise available in anyone source.

Biological markers (biomarkers) are useful tools for understanding the nature and extent of human exposure and risk from environmental toxicants. Biomarkers are classified into three basic categories: exposure, effect, or susceptibility. A marker of exposure is the product of the interaction between a target cell or molecule and a foreign substance (NAS, 1989). These markers can be used to determine the biologically effective dose necessary to elicit a particular physiological change in an organism. A marker of effect is a biochemical or physiological change in an organism that can predict the onset of adverse health effects resulting from a given exposure. Lastly, markers of susceptibility act as indicators of an inherent or acquired tendency of an organism to experience an adverse health effect (NAS, 1989). These markers are already used to detect a variety of diseases and show great promise for developing a better understanding of the mechanicisms of disease. Additionally, biomarkers can be used to establish a more rational basis for quantitative risk extrapolation between species, as weIl as to obtain more precise estimates of the time of critical exposure. These markers can also prove helpful in identifying potentially damaging exposures before the onset of adverse health effects. Biomarkers serve as a valuable exposure assessment tool because they take into account exposure from all routes and integrate exposure from all sources. They have the potential to yield better risk estimates than current monitoring and modeling protocols. In lune 1992, Dr. Travis and Dr.

This volume is intended for the professional who is a newcomer to the area of environmental radon. It marks the first time that chapters on these subjects have been brought together in a single volume, and it is arranged so that anyone with some basic university-level chemistry and physics can develop a clear understanding of the different aspects involved. The volume is intended to serve as a supplementary textbook in public health, environmental, and health physics courses. It also can be used by the professional to get "up to speed" in this rapidly evolving field. The chapters are not necessarily a discussion of the latest research in this fast-moving field, but are intended to bring the reader to a level at which he can easily understand the current literature. At the back of this volume the reader will find the references for the individual chapters, a general list of reading materials, a glossary, an appendix describing the equations for radioactive decay for a series of progeny, a table of often used conversion factors, and the addresses and brief biographies of the authors and editors. Both historical and SI (International System) units are used throughout the book to provide information for the widest range of readers. Thanks go to Tom Hess for the idea for this volume and to Jessica Barron for help in editing.

Reviews of Environmental Contamination and Toxicology attempts to provide concise, critical reviews of timely advances, philosophy and significant areas of accomplished or needed endeavor in the total field of xenobiotics, in any segment of the environment, as well as toxicological implications.

Reviews of Environmental Contamination and Toxicology provides detailed review articles concerned with aspects of chemical contaminants, including pesticides, in the total environment with toxicological considerations and consequences. L.S. ANDREWS, M. AHMEDNA, R.M. GRODNER, J.A. LIUZZO, P.S. MURANO, E.A. MURANO, R.M. RAI, S. SHANE, AND P.W. WILSON: Food Preservation Using Ionizing Radiation CARMEN CABRERA, EDUARDO ORTEGA, MARIA-LUISA LORENZO, AND MARIA-DEL- CARMEN LOPEZ: Cadmium Contamination of Vegetable Crops, Farmlands and Irrigation Waters N.M. VAN STRAALEN AND J.P. VAN RIJN: Ecotoxicological Risk Assessment of Soil Fauna Recovery from Pesticide Application

Environmental Chemistry is a relatively young science. Interestin this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and Iimits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives ofEnvironmental Chemistry must be the study ofthe environment and of natural chemical processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environ ment and chemical reactions occurring in the environment. The industrial activities of man have given a new dimension to Environ mental Chemistry. Wehave now synthesized and described over five million chemical compounds and chemical industry produces about hundred and fifty million tons of synthetic chemieals annually. We ship billions of tons of oil per year and through mining operations and other geophysical modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas ofup to 15 million inhabitants produce large quantities ofwaste in relatively small and confined areas. Much of the chemical products and waste products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cycles and reactions and frequently Iead to interference and disturbance of natural systems."

The environment of our planet is degrading at an alarming rate because of non-sustainable urbanization, industrialization and agriculture. Unsustainable trends in relation to climate change and energy use, threats to public health, poverty and social exclusion, demographic pressure and ageing, management of natural resources, biodiversity loss, land use and transport still persist and new challenges are arising. Since these negative trends bring about a sense of urgency, short term action is required, whilst maintaining a longer term perspective. The main challenge is to gradually change our current unsustainable consumption and production patterns and the nonintegrated approach to policy-making. This book covers the broad area including potential of rhizospheric microorganisms in the sustainable plant development in anthropogenic polluted soils, bioremediation of pesticides from soil and waste water, toxic metals from soil, biological treatment of pulp and paper industry wastewater, sustainable solutions for agro processing waste management, solid waste management on climate change and human health, environmental impact of dyes and its remediation. Various methods for genotoxicity testing of environmental pollutants are also discussed and chapters on molecular detection of resistance and transfer genes in the environmental samples, biofilm formation by the environmental bacteria, biochemical attributes to assess soil ecosystem sustainability, application of rhizobacteria in biotechnology, role of peroxidases as a tool for the decolorization and removal of dyes and potential of biopesticides in sustainable agriculture. It offers a unique treatment of the subject, linking various protection strategies for sustainable development, describing the inter-relationships between the laboratory and field eco-toxicologist, the biotechnology consultant, environmental engineers and different international environmental regulatory and protection agencies.

Environmental Chemistry is a relatively young science. loteTest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and limits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topies which are based on chemistry embodied in this subject. One of the first objectives of Environmental Chemistry must be the study of the environment and of natural chemieal processes which occur in the environment. A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment and chemical reactions occurring in the environment. The industrial activities of man have given a new dimension to Environmental Chemistry. We have now synthesized and described over five million chemical compounds and chemical industry produces about hundred and fifty million tons of synthetic chemicals annually. We ship billions of tons of oil per year and through mining operations and other geophysieal modifications, large quantities of inorganic and organic materials are released from their natural deposits. Cities and metropolitan areas of up to 15 million inhabitants produce targe quantities of waste in relatively small and confined areas. Much of the chemical products and waste products of modern society are released into the environment either during production, storage, transport, use or ultimate disposal. These released materials participate in natural cycles and reactions and frequently lead to interference and disturbance of natural systems.

The EEC's heavy dependence on imported raw materials, combined with insufficient priority given to recuperative technologies, provided twin incentives to convene the European Conference on Waste Management. The conference was also held in answer to a call for a serious interna tional forum to enable high calibre spokesmen to express their views on a diversity of vital interests. The ambitious objective was that such a melting pot would smooth the road to cohesive policies and purposeful action, especially in the field of waste recycling. Among the speakers there were several specialists ready to outline the state of the art of a variety of technical subjects. This range included aspects of packaging, hazardous waste, the utilisation of waste in agri culture, energy from waste, and waste paper. aper was to play a particularly serious role, because pulp and paper is the largest external commodity need by the EEC countries after oil. Speakers were to be drawn from all parts of the EEC, in the expectation that country-to-country comparisons would stimulate progress in specific areas. This hope was frequently realised. Well represented was the Environment and Consumer Protection Department of the Commission itself. It is this department that has been quietly setting the beginnings of a coherent policy for waste management for throughout the 250 million population Community for the past seven years."

In 1949, when the North Atlantic Treaty was ratified, one of its articles explicitly noted '1hat member countries should contribute towards the further development of peaceful and friendly international relations." Specific problems related to the human environment were addressed by the Committee of Challenges of Modern Society (CCMS) of NATO, established in 1969. This provided a framework within which a series of International Technical Meetings (ITMs) on Air Pollution Modelling has been held. This volume documents the proceedings of the 18th meeting in this series. Science, like the arts and sports, provides an ideal vehicle for "developing peaceful and friendly international relations". National boundaries have never been barriers to the movement of air pollution, and fortunately this has also proved true of scientists studying the transport of air pollution. It is thus satisfying to record that since the mid-seventies it has been commonplace to find Eastern European scientists among attendees at the ITMs which have (in a very modest way) participated in a precursor to the process which has led to historical changes in Europe and which will undoubtedly lead to a tremendous increase in personal and intellectual exchange on a worldwide basis.

There is not an extensive literature on street sweeping. Much of the research that has been completed exists in the "gray" area of technical reports and government documents. Furthermore, a great deal of this research is locally based, and has not been widely published. Indeed, our review of the scientific literature, revealed that, while storm water quality has received a lot of attention, few academicians have been involved in street sweeping research per se. Thus, throughout our research into street we sweeper effectiveness, sweeping protocols, and sweeping practices, wished that there had been a book summarizing some of the important issues associated with street sweeping. As our frustration grew, we realized that we were uniquely poised to write such a book as our research had encompassed a variety of different projects including sweeper testing, waste management, and related storm water quality. Also, early on in this exercise, we recognized that there was a growing demand for information about street sweeping policies and management, especially for studies focusing on the effectiveness of different sweeping schedules, on waste management operations, and on non-point, pollution reduction practices associated with storm water runoff. It was abundantly clear that there was a profound lack of research on street sweeping that could assist with developing local, regional, or national policies. There was, in effect, little guidance for city managers on these issues.

In this timely volume, scientists examine examine the physical, structural, and analytical chemistry of fuel combustion. Their contributions also address the issue of combustion efficiency and how air quality can be protected or improved. Supported by numerous illustrations, this volume be appreciated by researchers and students working in various areas of chemistry.

In 1969 the North Atlantic Treaty Organization (NATO) established the Committee on Chal- lenges of Modern Society (CCMS). The subject of air pollution was from t,lw start one of the priority problems under study within the framework of various pilot. studi('s undertaken by this committee. The organization of a periodic conference dealing with air pollution modelling and its application has become one of the main activities within the pilot ~tudy relatillg to air pollution. The first five international conferences were organized by the United Statcs as the pilot country; the second five by the Federal Republic of Germany: thc third five by sselgium; the next four by The Netherlands; ami the two most recent by Delllllark. This volume contains the papers presented at the 21st NATOjCCMS International Technical Meeting (ITM) on Air Pollution Modelling and Its Application, held in ssaltimorc. Maryland, during November 6-10, 1995. This ITM was jointly organized by the Riso National Laboratory of Denmark (Pilot Country); by the EPA National Exposurp Research Labora- tory, United States (Host Country); and by thc American MNeorologiea.! Soci('t.: *. Cnited States (Host Organization). The ITM was attended by 137 participants representing 29 countri('~ from North and South America, Europe, Asia and Australia. The members of t.hc NATO/CCMS Scientific Committee for the 21st ITM were R.M. van Aalst (The Nethcrlallds), D. Allfossi (Haly), C. Borrego (Portugal), N. Chaumerliac (Francc), H. van Dop (Thc :\Tethcrla.nds). S.-E. Gryning.

Chemical pretreatment of nuclear wastes refers to the sequence of separations processes used to partition such wastes into a small volume of high-level waste for deep geologic disposal and a larger volume of low-level waste for disposal in a near-surface facility. Pretreatment of nuclear wastes now stored at several U. S. Department of Energy sites ranges from simple solid-liquid separations to more complex chemical steps, such as dissolution of sludges and removal of selected radionuclides, e. g. , 90Sr, 99Tc, 137CS, and TRU (transuranium) elements. The driving force for development of chemical pretreatment processes for nuclear wastes is the economic advantage of waste minimization as reflected in lower costs for near-surface disposal compared to the high cost of disposing of wastes in a deep geologic repository. This latter theme is expertly and authoritatively discussed in the introductory paper by J. and L. Bell. Seven papers in this volume describe several separations processes developed or being developed to pretreat the large volume of nuclear wastes stored at the US DOE Hanford and Savannah River sites. These papers include descriptions of the type and amount of important nuclear wastes stored at the Hanford and Savannah River sites as well as presently envisioned strategies for their treatment and final disposal. A paper by Strachan et al. discusses chemical and radiolytic mechanisms for the formation and release of potentially explosive hydrogen gas in Tank 241-SY-101 at the Hanford site.