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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 82 (1978), S. 1723-1727 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 83 (1979), S. 3003-3007 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 55 (2004), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The aim of this study was to validate the use of laser granulometry in studies concerning fractions 〈 2 µm in soils. The study was carried out on the clay fraction of a loamy soil from northeast Thailand. Granulometry by light scattering requires the determination of the refractive indexes of the solid phases. Once these values have been established, laser granulometry can provide a detailed description of the particle-size distribution within the clay fractions. Laser granulometry showed a multimodal distribution in the clay fraction of this soil.The analysis of images obtained by transmission electron microscopy provided numerical distributions of soil particles, from which representations by surface area and by volume obtained by laser granulometry and by transmission electron microscopy could be compared. The representation of particle-size distribution by surface area, assuming that particles are similar to circles, is adequate and, in this range of particle size, minimizes the effect of larger diameters. The representation of the particle-size distribution assuming that particles are similar to platy discs is better than the current representation that assumes particles are similar to spheres. We used transmission electron microscopy to validate laser granulometry in the fractions 〈 2 µm.Elemental microanalysis was used to identify the mineralogy of the clay particles: illite, illite-smectite and kaolinite at a magnification of 31 000, corresponding to the clay fraction 〈 0.8 µm of the particle-size distribution. Quartz and illite were identified at a magnification of 3300, corresponding to the fraction between 0.8 and 2 µm. The mineral constituents of the soil are correlated with the modes of the particle-size distribution.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We have investigated the water retention properties of clayey subsoil horizons according to the variation of clay characteristics. The horizons studied developed on a large range of age and facies of calcareous or calcium-saturated clayey sediments. The water retention properties were studied from −10 hPa to −15 000 hPa water potential using small clods collected in winter when swelling is at a maximum and water content close to field capacity. The specific water content and volume of the clods at field conditions, their specific volume at −15 000 hPa water potential, the clay content, the organic carbon content, the cation exchange capacity, the N2-BET surface area and calcareous content were measured. The clay fabric, which is the spatial distribution of the elementary clay particles, was quantified when the soil was close to field capacity and we could attribute the whole pore volume to the porosity of the clay fabric. Our results show that the water retention properties of the clay vary greatly from one soil to another with respect to the clay fabric. The variation of the latter depends on the cation exchange capacity, the size of elementary particles and hydric stress history of the clay. We show that the water retention properties of the studied clayey soils vary according to the clay content and fabric, the latter being related either to parent material fabric or to both the hydric history of the soil and size of the elementary clay particles.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 51 (2000), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Although the swelling of clays has been thoroughly studied, the mechanism by which this occurs in clay soils is not so fully understood. We have developed a technique to study the swelling and three-dimensional deformation of a soil sample during wetting by adapting a triaxial apparatus. This equipment applies a controlled, confined and isotropic pressure to the periphery of the samples. A constant flow of solution is injected into the base of the sample while the lateral and axial deformations are simultaneously controlled. The development of the interstitial pressure, positive or negative, is measured. When the soil is thoroughly wetted, the equipment measures the saturated hydraulic conductivity.The swelling of the soil is not necessarily isotropic, and practically all the possibilities of lateral, isotropic and vertical swelling can be encountered. Furthermore, the swelling can be preceded by significant lateral shrinkage, caused by fissures. The results show the importance of confinement pressure when measuring the swelling of the samples.The adaptation of a triaxial apparatus to the study of the permeability and swelling of soils appears to be promising as it also allows the geometric development of the samples to be traced as well as the changes in the chemical composition of the percolating solutions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    European journal of soil science 55 (2004), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: According to the literature, soil physical properties are linked mainly with organic constituents that are often considered as the first indicator of soil fertility. But the use of fertilizers and amendments can change soil properties independently of the organic matter content. In a long-term experiment at Versailles, fertilizers and amendments have been applied each year to uncultivated plots. After 70 years, the plots had the same low organic matter content except those which were treated with manure. However, the physico-chemical environment had become strongly differentiated. Physical properties, especially soil water relations, were also greatly affected. The use of ammoniacal fertilizers strongly decreased soil pH and cation exchange capacity (CECsoil). Plots treated in this way were more sensitive to the degradation of their hydraulic properties and became unstable in spite of the preservation of their porosity. Basic amendments (i.e. bases added as CO32–, OH–, O2– or silicate anions) increased soil pH, CECsoil and its saturation by exchangeable calcium. The increase in CECsoil improved soil structural cohesion and water flow properties. After basic treatment, there is greater structural stability, and water moves faster through the soil. In potassic and sodic plots, K+ and Na+ affected water movement and increased the soil's sensitivity to degradation. Manure treatment increased water retention and soil stability. The cation exchange capacity, measured at soil pH, can be used as a good indicator of soil stability, in combination with the organic matter content and the kinds of exchangeable cation (especially K+ and Na+).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The long-term effects of intermittent flooding on soil properties were studied in field experiments on a Vertisol cropped with rice in Senegal. The dominant clay minerals were smectite and kaolinite. When the soil was reduced after flooding, its cation exchange capacity (CEC) increased to twice that of its oxidized, unflooded state. Mössbauer spectroscopy showed an increase in smectite structural FeII upon reduction, which explained a part of the increase in CEC. The rest of the increase was attributed to the removal of iron oxyhydroxide coatings by reductive dissolution. The reduction and dissolution of oxides under the field conditions were substantiated by analysis of the surfaces of vermiculites buried in the Ap horizons of the cropped and the non-cropped soils. The redox-induced CEC changes were found to be reversible after 22 cycles of rice cropping. Nevertheless, the structural Fe and free Fe contents of the rice field Ap horizon were less than those of soil in uncropped neighbouring land, suggesting that inundation induced weathering and eluviation of the minerals. The observed changes in CEC and related redox reactions may substantially modify proton, anion and cation balances in intermittently flooded soils.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Electroanalytical Chemistry 146 (1983), S. 37-45 
    ISSN: 0368-1874
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Electroanalytical Chemistry 61 (1975), S. 251-263 
    ISSN: 0368-1874
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Electroanalytical Chemistry 103 (1979), S. 321-333 
    ISSN: 0368-1874
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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