Environmental Mineralogy: Microbial Interactions, Anthropogenic Influences, Contaminated Land and Waste Management

The past 10 years or so have seen the emergence of a discipline known as ‘Environmental Mineralogy’. This should be regarded not as a new discipline per se, but as a new application of traditional mineralogy. Mineralogists have always sought to understand the chemical and physical environment under which a particular mineral forms and to determine the arrangement of atoms within that mineral. The field of Environmental Mineralogy asks the same questions in a different context. For example, can minerals assist in the remediation of contaminated soils and waters? Which minerals can potentially be deleterious to, inter alia, buildings, ecology and human health? Which minerals are suitable as containment for waste? How does the biota interact with minerals? Environmental Mineralogy is emerging as a field that seeks to define the roles of minerals in all environmental systems, and to work towards the preservation and restoration of such systems. Environmental Mineralogy is achieving prominence because of increasing concern regarding the environments in which we live. Mineralogists have perceived a gap in our understanding of how minerals behave in the surface environment and a need for innovative,‘green’ solutions to the problems of contamination and waste. However, the emergence of Environmental Mineralogy also owes much to modern analytical technology. Many minerals in the surface environment fall within the clay-grade range and therefore, demand high-resolution systems for analysis. Similarly, trace elements are now detectable at exceptionally low concentrations in a wide variety of matrices. Further, many mineral-environment interactions need to be examined at the atomic scale for a greater understanding of the interactive processes involved. This requires the application of the latest technologies such as X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and atomic force microscopy to name but a few. The aim of this monograph is to provide an up-to-date account of the state of this diverse subject area. With chapters containing a strong review element, it is hoped that this volume will appeal to both researchers and students alike. The volume is arranged in four sections: (1) mineral-microbe interactions; (2) anthropogenic influences on mineral interactions; (3) minerals in contaminated environments; and (4) minerals and waste management. These four sections by no means give exhaustive coverage of the subject area, but communicate some of the most important developments taking place at the present time.
Gas entry into unconfined clay pastes at water contents between the liquid and plastic limits
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Published:January 01, 2000
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CiteCitation
A. T. Donohew, S. T. Horseman, J. F. Harrington, 2000. "Gas entry into unconfined clay pastes at water contents between the liquid and plastic limits", Environmental Mineralogy: Microbial Interactions, Anthropogenic Influences, Contaminated Land and Waste Management, J. D. Cotter-Howells, L. S. Campbell, E. Valsami-Jones, M. Batchelder
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Abstract
A programme of 143 simple gas injection experiments was performed on unconfined and initially water-saturated clay pastes at water contents between the plastic and liquid limits. The aim was to investigate the relationships between gas entry pressure, water content and plasticity for a range of clay types, to define the principal mechanisms of gas entry and flow by simple visual observations and to determine the effects of previous gas injection and residual gas content on entry pressure. Gas movement was found to be entirely through pressure-induced pathways, including highly-dilated tension fractures, flattened ellipsoidal cavities and bubbles. By examining entry mechanisms across the range of water contents, it was possible to delineate three zones of behaviour. Gas entry pressures in the region of the plastic limit were surprisingly large, particularly for clay types with high total specific surface and plasticity index. The highest individual entry pressure recorded in the study was 1810 kPa for Wyoming bentonite. There was no evidence in any test that gas actually penetrated, or flowed through, the intergranular porosity of the clay matrix. In all cases, gas made its own volume by pushing back the paste and lifting the free surface of the sample. After gas injection, remnant gas-filled voids and cracks remained within the clay. These were re-opened during repeated injections at pressures which were only a fraction of the entry pressures of the gas-free pastes. Gas entry at high pressures was audible and occasionally violent. The significance of these findings to gas migration modelling and the quantitative prediction of gas fluxes in clay formations is briefly examined.