ALBERT

Description / Table of Contents: PREFACE Turbidity currents have been comprehensively studied in the past although much remains unknown about both their flow characteristics and resultant sedimentary deposits. Much of this uncertainty arises from the catastrophic nature of their formation which makes them difficult to study in the environment, and has resulted in the majority of studies being experimental or theoretical. Experiments have shown that reversals in the flow of density currents can be associated with the generation of internal solitary waves. This is in contrast to the belief held by many workers that the reversal of a turbidity current simply generates an identical flow travelling in the opposite direction. This book arose from the need for a detailed experimental study to examine the effects and to consider the consequences of density current reversals from a variety of obstructions to their flow. The first part of this book comprises a detailed review of literature covering the fluid dynamics and sedimentology relevant to the experimental study (chapter one). Chapter two presents the results from the comprehensive experimental programme which are discussed and compared with appropiate theoretical hypotheses. This permits the synthesis of a model for the general features of flows that result from the incidence of density currents upon obstructions to the flow. The application of this model to both modern and ancient turbidite systems is then discussed in chapter three. This book is suitable for earth scientists with an interest in the dynamics of turbidity currents. In addition, workers from other fields such as applied maths, meteorology and engineering who have an interest in density currents and bores in practical situations may find it useful...

Description / Table of Contents: PREFACE Some of the major ecological and social problems of the present and future are the production, treatment, and disposal of anthropogenic wastes. Iaais is equally true for sparsely and densely populated industrial areas, including large countries in which sites for waste disposal would seem to be readily available. Especially nonradioactive hazardous wastes with their long-term toxicity need to be isolated from the biosphere just as effectively as radioactive substances. The long-term safety required of waste disposal sites can only be assured under specific geological and mineralogical conditions in certain parts of the lithosphere (underground repositories). The subjects related to the production, avoidance, treatment, and disposal of anthropogenic wastes cover a range of knowledge encompassing the natural sciences, engineering, medicine, and law. This work presents some fundamental situations and problems conceming the disposal of toxic hazardous wastes which have been dealt with in several research projects. The individual chapters are related scientifically. Long-term, effective solutions to our waste problems can only be found when interrelationships and possible future developments are considered. Only the current status of this rapidly developing field can be discussed here. The individual chapters contain scientifically founded data and observations. Other aspects for which there are still controversial opinions and arguments are also discussed, which should stimulate further thought. Further developments and scientific advances can only be achieved by constantly challenging previous theories, and not through static observation and narrow-mindedness. The most extensive quantification possible of the problems related to disposal of hazardous wastes is an essential aim of our work. This not only involves calculating the volume of waste and available repository space, but also compiling data on the long-term effects and the safe, long-term isolation of anthropogenic wastes from the biosphere. A simple description of conditions and processes without using concrete data, which is still widespread, is rejected since it frequently leads to pure speculation. The scientific fundamentals and results presented in this work are of general validity for many questions concerning waste disposal. One example is the amount of waste produced annually in Germany, in which toxic, hazardous wastes play a major role. FoIlowing this train of thought, available data are used to show how limited the possibilities are for the long-term safe underground deposition of hazardous wastes with respect to the current quantities of waste. Of utmost importance is information on the 10ng-term effects of toxic wastes, as well as criteria which have to be considered with respect to the long-term safe deposition of hazardous waste. The natural chemical cycles and material transport in the various zones of the earth are the focus of interest here. They are the scientific basis for assessing every repository for anthropogenic wastes in geological systems. Therefore the significance of material transport and geochemical cycles is emphasized regarding all questions concerning the long-term safety of repositories on the earth's surface and in the lithosphere. Thus, our concept for the scientific evaluation of the long-term safety of underground repositories in geological systems differs from all other models presently under discussion in Germany. In this work, marine evaporites are discussed with respect to the underground deposition of hazardous wastes and the long-term safety of underground repositories in salt rocks. The isolation of hazardous materials from the biosphere can above all be influenced by fluid phases. Fluid phases can mobilize and transport hazardous materials through rocks in the biosphere. This is true, without exception, for all magmatic, sedimentary, and metamorphic rocks, and for marine evaporites, too! In Germany evaporites have commonly been considered to be completely impermeable with respect to fluid phases (solutions and gases). This erroneous view stems from a complete lack of knowledge or misestimation of the dynamic evolution of the composition of evaporite bodies. Unfortunately, this is still true today for parts of some state agencies which deal with repositories. However, all observations of evaporite bodies made over the last more than 100 years have clearly shown that under certain conditions fluid and gaseous components are mobile in evaporites as well. Solutions in marine evaporites have been the object of personal interest and scientific research of A.G. Herrmann for 40 years. The occurrence and formation of salt solutions in the various salt mining districts of Germany are presently being restudied and reevaluated on an extended scientific basis (e.g., v. BORSTEL 1992). A presentation of the current knowledge on salt solutions is beyond the scope of this publication. However, in the interest of continuing research a research project proposed by A.G. Herrmann (1987b) will be introduced here. The direct quantitative analysis of the chemical composition (quatemary and quinary systems) of small fluid inclusions in rocks of the salt deposits of Hessen and Niedersachsen are the primary focus of this project. Information important to fundamental research on the formation and alteration of salt rocks and on the long-term safety of underground repositories should be gained from these studies (e.g., HERRMANN & v. BORSTEL 1991). In addition to salt solutions, gases are also fluid components which occur in practically all marine evaporite deposits. Hence, both salt solutions and gases must be carefully considered when planning underground repositories in an evaporite body and evaluating their long-term safety. This publication contains an up-to-date overview of the gas occurrences in the marine evaporites of Central Europe. Despite previous studies, there is still a considerable deficit in scientific information regarding the distribution and formation of gases in the evaporites occurring in Germany. A detailed research program on the geochemical relationships involving the formation of evaporites and gases will draw attention to this situation. One aspect must be emphasized in the planning and construction of repositories for anthropogenic wastes: their long-term safety. This publication deals precisely with this subject, and in Part III of this work we will present the concept that we have developed. This concept is based on the fact that evaporite bodies are subject to a dynamic evolution and that the chemical and mineralogical composition provides important information on the effect of fluid phases on salt rocks. Previous works contain the testing of methods and presented initial results using the Gorleben salt dome as an example. However, we are just at the beginning of our research project on the long-term safety of underground repositories (e.g., HERRMANN & KNIPPING 1989, HERRMANN 1992). The information contained in this publication is based on years of experience in evaporite research and underground repositories for anthropogenic wastes. Examples are presented which can be applied to similar situations and problems in other countries. Waste disposal is not just a national problem, it has long become an international one for all types of anthropogenic wastes...