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.
Weathering of rocks by lichens: fragmentation, dissolution and precipitation of minerals in a microbial microcosm
Published:January 01, 2000
M. R. Lee, 2000. "Weathering of rocks by lichens: fragmentation, dissolution and precipitation of minerals in a microbial microcosm", 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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Despite the abundant evidence that rock-encrusting lichens can weather their substrates, it is currently unclear whether rates of lichen-mediated weathering are faster or slower than rates of abiotic weathering of otherwise identical rock surfaces (i.e. are lichens biodestructive or bioprotective?). This question is of considerable academic and commercial importance. Lichens weather rocks by a combination of biophysical and biochemical mechanisms. Fungal hyphae can penetrate into rocks at ≤~0.1 mm y;1 and sandstones and limestones are especially vulnerable. Biophysical weathering leads to the fragmentation of minerals, exposing grain interiors. These fresh surfaces may be attacked by a variety of compounds including extracellular polysaccharides, lichen acids and oxalic acid. Evidence for the effectiveness of these biochemical agents includes etched and leached mineral grains and reaction products such as oxalate salts, clay minerals and Fe-hydroxides. Few studies have quantified rates of lichen-mediated weathering and fewer still have compared these data with the weathering rate of unencrusted rock surfaces. The conclusion of this work is that lichens enhance the weathering rate of rock surfaces relative to identical but abiotic substrates. As weathered mineral grains and weathering products are bound within the lichen, these materials will not be eroded until the lichen dies after ~101—103 y. Thus, despite being active agents of weathering, lichens should stabilize and protect rock surfaces over the short term. Studies of dated surfaces of a variety of rock types colonized by diverse lichen populations are essential before the impact of lichen colonization on rates of rock weathering can be accurately quantified and predicted.