Mineral tunnelling

This chapter reviews the distribution, mechanism and impact of mineral tunnelling by soil ectomycorrhizal fungi (EMF). Most trees in boreal forests live in close relation with EMF (Smith Read, 1997). These EMF mediate nutrient uptake they form an extension of the tree roots. In turn they obtain carbohydrates from the tree. Over the years ectomycorrhizal (EM) research has a strong focus on nutrient acquisition by EMF from organic sources (Read, 1991). In boreal forest systems, however, minerals could also be an important nutrient source, especially for calcium, potassium and phosphorus (Likens et al, 1994, 1998 Blum et al, 2002). Recent developments in EM research suppose a role for EMF in mobilizing nutrients from minerals (see Wallander, Chapter 14, this volume). 

Smits, M., Hoffland, E. van Breemen, N. (2005). Contribution of mineral tunneling to total feldspar weathering. Geoderma, 125, 59-69. 

Compound or mineral Approximative formula Symmetry Space group Lattice constants Reference Tunnel size... 

The wide variety of natural minerals with [2 x 2] tunnels already indicates that a huge number of different compounds of the a-Mn02 type can be obtained by a laboratory synthesis. Most chemical syn-... 

For a long time the structural classification of the mineral todorokite was uncertain, until Turner and Buseck [4] could demonstrate by HRTEM investigations that the crystal structure of that mineral consists of triple chains of edge-sharing octahedra, which form [3 x 3] tunnels by further corner-sharing. These tunnels are partially filled by Mg2+, Ca2+, Na+, K+, and water (according to the chemical analysis of natural todorokites). In 1988 Post and Bish could perform a Rietveld structure determination from XRD data taken for a sample of natural todorokite [25], This diffraction study confirmed the results of Turner and Buseck. The cations... 

Apart from structures that are built of slabs, modular structures that can be constructed of columns in a jigsawlike assembly are well known. In the complex chemistry of the cuprate superconductors and related inorganic oxides, series of structures that are described as tubular, stairlike, and so on have been characterized. Alloy structures that are built of columns of intersecting structures are also well known. Structures built of linked columns, tunnels, and intersecting slabs are also found in minerals. Only one of these more complex structure types will be described, the niobium oxide block structures, chosen as they played a significant role in the history of nonstoichiometry. 

One particular type of source that should be studied carefully Is entrained soil. As shown above, this Is often the greatest contributor of TSP In urban areas. As there Is so much of It present, we need to know concentrations of all measured elements quite well to make an accurate determination of the residual amounts left to be accounted for by other sources. The composition of selved soil Is often used for the soil component, but there may be considerable fractionation Imposed by entrainment, e.g., preferential selection of very fine clay mineral particles. Such fractionation has been demonstrated In the very limited studies of entrainment of particles from soil of known composition (e.g.. Refs. 21, 49). These studies can probably best be done In controlled environments such as wind tunnels. One cannot simply collect ambient particles In the countryside and consider it to be soil, as there are anthropogenic contributions even at great distances from cities ( ). There Is further confusion betwen clean, "continental" dust and "urban" dust. The latter, which Is usually collected near city streets (21, 50), typically has a composition of soil contaminated by anthropogenic emissions, especially from motor vehicles. 

In a short but remarkable discourse on Hebrew mining, Job states that Iron is taken out of the earth (Job 28, 2). This passage describes the deep shaft, the dark galleries and tunnels through the rock, the underground streams, the beautiful, precious minerals, and the rugged, hazardous life of the miners. The iron stylus mentioned in Job 19, 24 was one of the most ancient of writing instruments. Iron fishhooks and spears must also have been in use when this book was written Canst thou draw out leviathan with an hook . . . Canst thou fill his skin with barbed irons or his head with fish spears (Job 41,1, 7). 

Mineral-liquid or mineral-gas interfaces under reactive conditions cannot be studied easily using standard UHV surface science methods. To overcome the pressure gap between ex situ UHV measurements and the in situ reactivity of surfaces under atmospheric pressure or in contact with a liquid, new approaches are required, some of which have only been introduced in the last 20 years, including scanning tunneling microscopy [28,29], atomic force microscopy [30,31], non-linear optical methods [32,33], synchrotron-based surface scattering [34—38], synchrotron-based X-ray absorption fine structure spectroscopy [39,40], X-ray standing wave... 

Wet mixes are usually dried before calcination. Calcination is performed continuously in rotary or tunnel kilns, or batchwise in directly fired drum or box furnaces. The temperature at which the mixed metal oxide pigments are formed can be reduced by adding mineralizing agents [3.75]. In the case of chromium rutile pigments, addition of magnesium compounds [3.81] or lithium compounds [3.80] before calcination improves thermal stability in plastics. 

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