Mineralogy of salt efflorescences in paddy field soils of Kollo, southern Niger

Ducloux, J.; Guero, Yadji; Fallavier, Paul; Valet, Serge

doi:10.1016/0016-7061(94)90089-2

Cited by 15 publications

(5 citation statements)

References 25 publications

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“…Hexahydrite has also been described for surface horizons of soils containing epsomite at greater depths (e.g. Doucloux et al, 1994). In the Aral Sea basin, epsomite is known to occur (Boomer et al, 2000;Singer et al, 2001;Benduhn and Renard, 2004), and synsedimentary hexahydrite formation is predicted based on present lake water composition (Létolle et al, 2005).…”

Section: Lake Bed Crustmentioning

confidence: 97%

Surface crusts on soils/sediments of the southern Aral Sea basin, Uzbekistan

Mees

Singer

2006

Geoderma

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Section: Lake Bed Crustmentioning

confidence: 97%

Surface crusts on soils/sediments of the southern Aral Sea basin, Uzbekistan

Mees

Singer

2006

Geoderma

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“…This allows for the simulation of numerous applied hydro-geochemical environmental engineering problems where mineral reactions have an important influence on the physical properties of partially saturated soils. Possible applications include vadose zone biodegradation processes [31,32], water management practices and irrigation techniques in arid and semiarid areas [33][34][35], salinity management [36][37][38][39] and the assessment of the longterm performance of reactive barriers [40][41][42][43][44][45][46]. Below, we present the theoretical model derivation followed by applications of the model to the case of kinetic halite dissolution in different moisture conditions and calcite precipitation due to cation exchange.…”

Section: Fig 1 Near Herementioning

confidence: 99%

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Wissmeier

Barry

2009

Advances in Water Resources

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT AbsThe selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards' equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC's comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil's hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter . Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even r tract increase du ing precipitation due to changes in the pore-size distribution.

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“…In addition, other magnesium sulfate hydrates (sanderite-2H 2 O, starkeyite-4H 2 O, pentahydrite-5H 2 O) have been identified in evaporites or as efflorescent salts at a few localities, particularity in mines where sulfides alter under humid conditions. Generally, these deposits contain several Mg-sulfate hydrates along with other sulfates such as gypsum, thenardite, konyaite, mirabilite, and bloedite (e.g., Whittig et al, 1982;Last, 1984;Keller et al, 1986;Ducloux et al, 1994;Singer et al, 1999).…”

Section: Introductionmentioning

confidence: 98%