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.
Heterotrophic solubilization of metal-bearing minerals by fungi
Published:January 01, 2000
G. M. Gadd, 2000. "Heterotrophic solubilization of metal-bearing minerals by fungi", 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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The production of organic acids by fungi has profound implications for metal speciation and biogeochemical cycles. Metal-complexing properties of organic acids, e.g. citric and oxalic acid, assists essential metal and anionic (e.g. phosphate) nutrition of fungi, other microorganisms and plants, and affects metal speciation and mobility in the environment, including transfer between terrestrial and aquatic habitats, biocorrosion and weathering. Metal solubilization processes also have potential for metal recovery from contaminated solid wastes, soils and low-grade ores. Such ‘heterotrophic leaching’ can occur by several mechanisms but organic acids occupy a central position in the overall process supplying both protons and metal-complexing organic acid anions, e.g. citrate. Most simple metal oxalates (except those of alkali metals, Fe(III) and Al) are sparingly soluble and precipitate as crystalline or amorphous solids. Calcium oxalate is the most important oxalate in the environment and is ubiquitously associated with free-living, symbiotic and pathogenic fungi. The main forms are the monohydrate (whewellite) and the dihydrate (weddelite) and their formation affects nutritional heterogeneity in soil, especially that of Ca, P, K and Al, while in semi-arid environments, calcium oxalate formation is important in the development of terrestrial subsurface limestones. The formation of insoluble toxic metal oxalates, e.g. Cu, may ensure fungal survival in the presence of elevated metal concentrations.