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.
Uranium behaviour in natural environments
Published:January 01, 2000
K. V. Ragnarsdottir, L. Charlet, 2000. "Uranium behaviour in natural environments", 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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In crustal fluids uranium transport and deposition is dominated by redox conditions. The concentrations of dissolved U(IV) species never exceed μg l;1 levels, whereas the concentration of U(VI) species reaches tens of μg l;1 depending on pH and ligand concentration(s). As a result, uranium is transported in aqueous fluids of high Eh but deposited when Eh decreases, e.g. in sedimentary environments and engineered barriers that contain sulphide, organic matter, and/or Fe(II)-bearing minerals; bacteria and mineral surfaces are known to catalyse these reduction reactions. Mining activities result in remobilization of uranium as U(VI). In the presence of oxy(hydr)oxides or clay minerals, aqueous uranyl ions are sorbed at intermediate pH. In rivers, uranium transport is dominated by surface-sorbed uranium on colloids and particles. Upon entering the oceans. uranium is deposited in estuarine sediments due to flocculation, or desorbed due to the presence of carbonate ligands in seawater. Uranyl-carbonate complexes can be transported over long distances and thus the uranium residence time in the oceans is greater than that of water. In the presence of appropriate ligands uranium precipitates to form stable minerals and the transport path can be traced by U isotopic ratios of alteration products. The mobility of uranium and its enrichment in the Earth’s crust is magnified by subduction zone processes.