Evgenii Viktorovich Shein
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Salt neoformations in the soils of the Aral Sea dried bottomMoscow University Bulletin. Series 17. Soil science. 2022. 3. p.36-47Galina V. Kharitonova Evgenii V. Shein Valeria O. Krutikova Galina V. Stulina Alexander V. Dembovetskyread more473
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Salt neoformations in sandy and silty loam soils of the Aral Sea dried bottom in the south-western part were studied by X-ray fluorescence, electron microscopic, sedimentation methods of analysis and laser diffractometry. The surface layers of soils are significantly saline and enriched with CaCO3. The distribution of CaCO3 over the area is quite uniform, which indicates relatively close conditions of its formation during desiccation. The salt content varies from 0.4 to 1.2% in sands and from 3.1 to 5.8% in silty loam. The latter are characterized by the highest salinity, when, in addition to gypsum and halite, readily soluble salts are formed: eugsterite (2Na2SO4.CaSO4.2H2O), astrakhanite (Na2SO4.MgSO4.4H2O), and mirabilite (Na2SO4.10H2O). Precipitation of calcite upon drying leads to the formation of CaCO3-ooids in sands and CaCO3- microaggregates from clay and silty particle in silty loam. The reason for the increased activity of easily soluble salts in the processes of aeolian transport has been established. This transport and, correspondingly, the salinization of adjacent territories are facilitated by the blocking of adsorption centers in clays by calcite, which prevents the binding of easily soluble salts in clay-salt microaggregates.
Keywords: soil texture; salt compositions; carbonates; evaporites; electron microscopy
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Granulometric composition of soils: history, development of methods, current state and prospectsMoscow University Bulletin. Series 17. Soil science. 2024. 4. p.7-13read more88
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The problems of determination and classification of soils by granulometric composition from the point of view of domestic and international soil science are considered. The development of methods and devices for granulometric analysis of soils was largely promoted by the works of the Department of Soil Physics and Reclamation, on the basis of which the necessity of two stages of granulometric analysis was shown, the all-Russian method of sedimentation analysis of particles by pipette method was founded, with the development of the classification of N.A. Kachinsky and names of soils by granulometry, which are fundamentally different from those generally accepted in the world practice. At present, at the first stage the method of pretreatment with 4% sodium pyrophosphate is widespread, at the second stage — measurement of granulometric composition two approaches are used — sedimentation method and laser diffractometry, which have different physical bases. The difference of final results on granulometric composition of soils is usually associated with different shape and density of solid phase of organic and mineral particles. This paper presents the studies of granulometric composition of agrodernovo-podzolic sandy loam soil (Tver region, VNIIMZ experimental site) with low content of organic matter in comparison of three methods of granulometric composition determination: laser diffractometer, sedimentometric methods of suspension pressure estimation on Pario - ISP+ (Integral Suspension Pressure) device and classical pipette method. Th e laser diffractometer for fine fractions showed systematically underestimated data with the same pretreatment procedure compared to ISP and pipette method. The ISP+ method compared to the classical pipette method gives similar results.Keywords: classification of soils by granulometric composition; methods of granulometric analysis; pretreatment and granulometric analysis
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