Salt Neoformations in the Soils of the Aral Sea Dried Bottom

Salt Neoformations in the Soils of the Aral Sea Dried Bottom

— Salt neoformations of seaside solonchaks (different in their granulometric composition) of the dried bottom in the southwestern part of the Aral Sea were studied by X-ray fluorescence, electron microscopy, the sedimentation method, and laser diffractometry. The surface layers of soils of sandy and...

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Bibliographic Details
Published in:Moscow University soil science bulletin Vol. 77; no. 3; pp. 142 - 152
Main Authors: Kharitonova, G. V., Stulina, G. V., Shein, E. V., Dembovetskii, A. V., Krutikova, V. O.
Format: Journal Article
Language:English
Published: Moscow Pleiades Publishing 2022
Springer Nature B.V
Subjects:
Calcite
Calcium carbonate
Chemical precipitation
Clay
Clay soils
Composition
Crystal growth
Crystallization
Drying
Earth and Environmental Science
Earth Sciences
Electron microscopy
Fluorescence
Gypsum
Historical Geology
Loam
Loam soils
Molecular clusters
Paleontology
Salinization
Salt
Salts
Sandy soils
Silt loam
Sodium sulfate
Soil layers
Soil stability
Solid phases
Surface layers
X-ray fluorescence
Aral Sea
solonchaks
electron microscopy
granulometric composition
salt composition
carbonates
evaporites
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Summary:— Salt neoformations of seaside solonchaks (different in their granulometric composition) of the dried bottom in the southwestern part of the Aral Sea were studied by X-ray fluorescence, electron microscopy, the sedimentation method, and laser diffractometry. The surface layers of soils of sandy and silty clay composition were considerably saline and enriched with CaCO 3 . The distribution of CaCO 3 over the area was quite uniform, indicating relatively similar conditions for its formation during drying. Salt content varied from 3.1 to 5.8% in silty loam soils and 0.4 to 1.2% in sandy soils. Silty loam soils were characterized by the highest salinity level. In addition to gypsum and halite, easily soluble salts were formed in them: eugsterite (2Na 2 SO 4 ·CaSO 4 ·2H 2 O), astrakhanite (Na 2 SO 4 ·MgSO 4 ·4H 2 O), and mirabilite (Na 2 SO 4 ·10H 2 O). The template mechanism of CaCO 3 accumulation in soils was revealed. The result of the interaction of CaCO 3 with the solid phase of deposits depended on their granulometric composition, which determined the predominant particle size and, accordingly, the number of crystallization centers. Under the conditions of a small number of crystallization centers in sandy soils, the formation of CaCO 3 cutans characterized by varying levels of stability and coverage of the sand grain surface occurred. In silty-clay soils with a large number of crystallization centers under constrained conditions for crystal growth, CaCO 3 precipitation led to the formation of molecular clusters that bound clay and silty particles into CaCO 3 microaggregates. The cause of the increased activity of salt neoformations in the processes of aeolian transport was established. This transport and, therefore, salinization of adjacent territories was facilitated by the blocking of adsorption centers by calcite in clays, which prevented the binding of soluble salts in clay–salt microaggregates.
ISSN:0147-6874
1934-7928
DOI:10.3103/S0147687422030061