Dissolution of minerals

The increased solute-loading in terrestrial waters is due to dissolution of minerals in rock, soil and overburden materials as rainwater infiltrates them. Groundwater experiences the largest degree of water-rock interaction and consequently has the highest average... 

Adsorption influences the reactivity of surfaces. It has been shown that the rates of processes such as precipitation (heterogeneous nucleation and surface precipitation), dissolution of minerals (of importance in the weathering of rocks, in the formation of soils and sediments, and in the corrosion of structures and metals), and in the catalysis and photocatalysis of redox processes, are critically dependent on the properties of the surfaces (surface species and their strucutral identity). 

We exemplify the reductive dissolution of minerals by illustrating the reductive dissolution of hydrous ferric oxide. With this oxide (Sulzberger et al. 1989, Suter et al.,... 

Hering, J., and W. Stumm (1990), "Oxidative and Reductive Dissolution of Minerals," in M. F. Hochella Jr. and A. F. White, Eds., Reviews in Mineralogy 23 Mineral-Water Interface Geochemistry, pp. 427-465, Mineralogical Society of America. 

Stumm, W., F. Furrer, and B. Kunz (1983), "The Role of Surface Coordination in Precipitation (Heterogeneous Nucleation) and Dissolution of Mineral Phases", Croat. Chem. Acta 56, 593-611. 

The geochemical fate of most reactive substances (trace metals, pollutants) is controlled by the reaction of solutes with solid surfaces. Simple chemical models for the residence time of reactive elements in oceans, lakes, sediment, and soil systems are based on the partitioning of chemical species between the aqueous solution and the particle surface. The rates of processes involved in precipitation (heterogeneous nucleation, crystal growth) and dissolution of mineral phases, of importance in the weathering of rocks, in the formation of soils, and sediment diagenesis, are critically dependent on surface species and their structural identity. 

Dissolution of minerals, such as may occur during dissimilatory Fe(lll) reduction, or precipitation of new biominerals during reductive or oxidative processing of Fe, represent important steps in which Fe isotope fractionation may occur. We briefly review several experiments that have investigated the isotopic effects during mineral dissolution, as well as calculated and measured isotopic fractionations among aqueous Fe species and in fluid-mineral systems. In some studies, the speciation of aqueous Fe is unknown, and we will simply denote such cases as Fe(lll)jq or Fe(ll)aq. 

The limitation of water leaching is that some minerals which are not soluble within the coal sample may dissociate on leaching. For the acid leaching, a major problem arises from the dissolution of minerals. This means that both cations exchanged onto the surface are removed as well as ions from the minerals and it is not possible to determine the amount of ions related to the two different environments. 

Crystal dissolution/melting/growth may be controlled by interface reaction rate (Figure 1-lla), meaning that mass/heat transfer rate is very high and interface reaction rate is low. Examples include dissolution of minerals with low... 

Now consider the dissolution of mineral Cao.85 Mgo.15 CO3 in pure water with one atmosphere CO2. If this mineral acted like a solid solution phase, it would dissolve congruently along reaction path AA until it reached at A saturation with a calcium-rich magnesian calcite less soluble than itself. We will see later in this... 

Reductive dissolution of minerals also can occur as a photochemical reaction in the presence of organic ligands.32 An example of this light-mediated process is described briefly for hematite in the presence of oxalic acid in Eq. 1.9 and... 

Complexation has a significant influence on dissolution and precipitation of minerals as already described in chapter 1.1.4.1.3. In contrast to the dissolution of minerals, complexation is a homogeneous reaction. It can be described by the mass-action law. The complexation constant, K, gives information about the complex stability. Large complex constants indicate a strong tendency for complexation, or high complex stability. 

Solubility. Dissolution of minerals during chemical weathering releases species into solution but aqueous phase concentrations are limited by the solubility of solid phases, such as amorphous silica,... 

In the present chapter, I will discuss the potential of EMF to influence weathering rates of soil minerals, and review experiments where the effects of EMF on dissolution of minerals have been investigated in axenic cultures, pot cultures and field experiments. I will then discuss the influence of the nutrient status of the trees on weathering induced by EMF and, finally, to what extent this process may influence the overall cycling of elements in forest ecosystems. 

Ectomycorrhizal plants and non-mycorrhizal control plants have been grown in pots and microcosms by many researchers to investigate the role of EM colonization on dissolution of minerals. In such experiments it is usually not possible to separate effects of the fungus itself and effects of other microorganisms in the soil that might be influenced by the presence of the EM fungus. 

Although EMF appear important in increasing dissolution of minerals, EM biomass on roots is usually a poor predictor of mineral dissolution since many EM species may not be active in weathering processes (Wallander et al., 2004). 

It is difficult to directly study the influence of EMF on dissolution of minerals in the field. Several studies on EM fungal mat communities in... 

Ravey, M., Farberman, B., Hendel, I., Epstein, S., Shemer, R. A vessel for low-pressure acid dissolution of mineral and inorganic samples. Anal. Chem. 67, 2296-2298 (1995)... 

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