Stability Of Clay Minerals Research Articles

Effects of Soil Acidification on Chemical and Mineralogical Properties of a Limed Soil

AbstractTwo soil acidulents were compared for their effects on soil chemical and mineralogical properties. Aluminum sulfate [Al2(SO4)3 · 18 H2O] powder was applied at rates of 0.13, 0.26, 0.52, and 1.05 kg m−3 (7.5, 15.0, 30.0, and 60.0 g per pot, respectively). Elemental S powder was added at rates of 0.03, 0.06, 0.13, and 0.26 kg m−3 (1.9, 3.8, 7.5, and 15.0 g per pot, respectively). Sawdust was incorporated into the soil at rates of 0, 20, 40, and 60 m3 m−3 (% by volume). The soil used in this experiment was a previously limed sandy loam surface from a Typic Hapludult with an initial pH of 6.2. On a mass basis, approximately eight times as much Al2(SO4)3·18 H2O as elemental S was needed to cause a two‐unit decrease in soil pH. The acidity produced by S maintained low pH longer than Al2(SO4)3·18 H2O. Extractable levels of Ca and Mg in the highest acidulent treatments were approximately double that of the controls at the conclusion of the experiment. This is a probable response to lime particles from a previous liming being dissolved by acids. Extractable K, because of destruction of illitic clay minerals, was significantly higher in the S treatments than in the Al2(SO4)3 treatments or controls. Extractable Al levels were greater than the controls only at higher rates of both acidulents. Extractable Al levels at a given pH were higher in the Al2(SO4)3‐treated soils than in those treated with S. Destruction of clay minerals, including gibbsite, kaolinite, and hydroxy interlayered vermiculite were evident in the highest S treatment, even though both the Ca/Mg and K/NH4 cation exchange capacity values increased when compared to the controls. Aluminum sulfate had little effect on clay mineral stability when compared to the controls, and may have increased the heat stability of K saturated hydroxy interlayered vermiculite.

The Polymer Model of Thermochemical Clay Mineral Stability

The Nriagu polymer model of 2:1 layer type clay minerals develops from the premise that clay minerals are condensation copolymers of solid hydroxides. In the Mattigod-Sposito formulation of the model, standard state chemical potentials (standard Gibbs energies of formation from the elements) of 2:1 clay minerals are predicted quantitatively with a linear correlation equation relating the standard Gibbs energy of the polymerization reaction (ΔGor) to the half-cell layer charge of the clay mineral and to the valence and ionic radius of the exchangeable cation. It is now shown that this correlation equation can be derived from two basic assumptions: (1) that the standard Gibbs energy change for the transfer of a cation in a pure hydroxide solid to a hydroxide component in the tetrahedral or octahedral sheet of a 2:1 clay mineral is independent of the nature of the cation and (2) that the difference between ΔGor for the polymerization reaction to form a 2:1 clay mineral and ΔGor for the same reaction to form the zero layer-charge analog of the clay mineral is proportional to the number of interlayer exchangeable cations per unit cell of the clay mineral and to the radius of its exchangeable cation. Both of these assumptions can be tested experimentally, independent of the polymer model.

Ionic Composition of Soil Solutions Separated from Forest Soils and Stability of Clay Minerals in Terms of Chemical Equilibrium : Comparative Studies on the Chemical Composition of Soil Solution in Land Used for Various Purposes (Part 5)

Ionic Composition of Soil Solutions Separated from Forest Soils and Stability of Clay Minerals in Terms of Chemical Equilibrium : Comparative Studies on the Chemical Composition of Soil Solution in Land Used for Various Purposes (Part 5)

A contribution to the study of the stability of clay minerals from the soil solution composition at different pF values

AbstractThe composition of the soil solution of various horizons of Galician soils was studied to gain insight into the direction of the processes of weathering and neoformation by means of stability diagrams of the clay minerals. The soil solution was extracted by compression at various pF values.The most significant results are as follows. In all the cases studied the mineral in equilibrium with the soil solution is a 1:1 philosilicate. As the pF at which the soil solution is extracted increases, corresponding to smaller pore size, pH increases and silica concentration falls. The stable mineral does not vary significantly between different horizons of the same profile. Each parent material gives rise to a different zonation in the stability diagrams. The predictions of the stability diagrams are in general agreement with the mineralogical data of the clays of the horizons in question.Finally, weathering processes in Galicia are briefly commented on.

Clay Mineral Stability as Related to Activities of Aluminium, Silicon, and Magnesium in Matrix Solution of Montmorillonite-Containing Soils

AbstractThe influence of geomorphological site characteristics on soil clay mineral stability of montmorillonite-containing horizons of a southern Wisconsin soil catena was interpreted in terms of the solute activity function values of pSi(OH)4, pH-1/2pMg2+ and pH-1/3pAl3+ in suspensions of the separated clay fractions. Montmorillonite stability and/or formation vs that of kaolinite for the soil clays was evaluated by a plot of the solute activity functions on a three dimensional diagram derived for montmorillonite, kaolinite, and gibbsite at constant temperature (25°C) and constant pressure (one atm.). Although all the soil clays contained both montmorillonite and kaolinite, the position of the soil clay solute activity functions in the stability diagram clearly reflected the influence of the geomorphological—geochemical site conditions in which each soil horizon was developed, with corresponding differences in the SiO2/Al2O3 molar ratio of the reactive fraction. Montmorillonite stability positions of the solute activity functions were induced by soils (clays with reactive fractions with SiO2/Al2O3 molar ratios = 3–4) from calcareous or poorly drained horizons, while kaolinite stability positions of the functions were induced by soils (clays with reactive fractions of SiO2/Al2O3 molar ratios = 2) from acid, freely drained horizons.

The Relationship Between Rainfall Frequency and Amount to the Formation and Profile Distribution of Clay Particles

AbstractFor Typic Argiudolls in Illinois the amount of pedogenic clay particles formed, over that inherited from the calcareous Peoria loess, seems to be controlled by rainfall frequency. The amount of solution leaching through the soil, as inferred from the amount of rainfall, was not related to the amount of pedogenic clay particles formed. This finding may help explain why the clay minerals found in the argillic horizon of some soils are not in the clay mineral stability field predicted by dilute solution chemistry.The distribution of clay within the soil profile is related to the amount and distribution of rainfall (leachable water), depth of leaching, and natural drainage class.

Magnesium and Silicon Activities in Matrix Solutions of Montmorillonite‐Containing Soils in Relation to Clay Mineral Stability

AbstractSoils of varying geomorphological site characteristics were sampled in the southern Wisconsin catena for the preparation of soil matrix solutions used for solute activity determinations. The catena clays contained from 27 to 45% of montmorillonite and from 11 to 3% of kaolinite in the < 0.2µm fraction. The SiO2/Al2O3 molar ratios of the reactive fraction of these < 0.2µm clay fractions ranged from 2.1 to 2.4 for the more acid horizons, indicating kaolinite or aluminous chlorite weathering products. Those of the reactive fraction from the calcareous and poorly‐drained horizons ranged from 3.1 to 3.9, indicating montmorillonite or beidellite (dioctahedral smectite) stability. The solute activity functions, pH ‐½pMg2+ and pSi(OH)4, for the field‐fresh soil matrix solutions fell distinctly into areas indicative of either montmorillonite stability (poorly drained or calcareous horizons) or of kaolinite stability (moderately well‐ to well‐drained, acid horizons) in a phase stability diagram developed to include a Mg‐saturated montmorillonite phase. The solute activity functions of the matrix solutions from Mg‐saturated soils or clays approached the montmorillonite‐kaolinite phase join more closely, with less impress from the geomorphic and weathering environments of the sites.The solute activity functions for montmorillonite‐free soils from northern Indiana, for montmorillonites of bentonites, and for kaolinites and chlorite (controls) fell in the appropriate areas of the diagram. The pH ‐½pMg2+ solute values of the kaolinite‐forming soils ranged from 2.3 to 4.6; the pSi(OH)4 values, from 3.2 to 3.9. The montmorillonite‐forming soils had pH ‐½pMg2+ solute values ranging from 4.7 to 6.2 and pSi(OH)4 from 3.0 to 4.0. Montmorillonite stability was indicated by higher values of the pH ‐½pMg2+ function and/or Si(OH)4 activities.

Magnesium and Silicon Activities in Matrix Solutions of Montmorillonite‐Containing Soils in Relation to Clay Mineral Stability

Soil Science Society of America JournalVolume 35, Issue 5 p. NP-NP ErratumFree Access Magnesium and Silicon Activities in Matrix Solutions of Montmorillonite-Containing Soils in Relation to Clay Mineral Stability This article corrects the following: Magnesium and Silicon Activities in Matrix Solutions of Montmorillonite-Containing Soils in Relation to Clay Mineral Stability R. M. Weaver, M. L. Jackson, J. K. Syers, Volume 35Issue 5Soil Science Society of America Journal pages: 823-830 First Published online: September 1, 1971 R. M. Weaver, R. M. WeaverSearch for more papers by this authorM. L. Jackson, M. L. JacksonSearch for more papers by this authorJ. K. Syers, J. K. SyersSearch for more papers by this author R. M. Weaver, R. M. WeaverSearch for more papers by this authorM. L. Jackson, M. L. JacksonSearch for more papers by this authorJ. K. Syers, J. K. SyersSearch for more papers by this author First published: 01 September 1971 https://doi.org/10.2136/sssaj1971.03615995003500050061xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume35, Issue5September-October 1971Pages NP-NP RelatedInformation

Soil Solution Composition and Stability of Clay Minerals

AbstractCommon soil minerals, such as the silicates, usually have very low solubilities and slow rates of dissolution and precipitation in the soil solution. This has tended to obscure the fact that their equilibrium reactions with the soil solution can actually be described by elementary thermodynamics. Ion analyses for soil solution‐mineral equilibria involve the same procedures and problems as do most other chemical analyses of the soil solution. The same is true for calculation of ionic strength, ion activities, equilibrium constants, and ΔG values. However, in determining mineral stabilities by the solubility method, special precautions are necessary to ensure that the activity of the desired ion species can be obtained from the measurements made and that these measurements represent true equilibrium conditions. The process involved in determining mineral stabilities is illustrated using Belle Fourche montmorillonite as the example.The usefulness of ΔG values for common soil minerals is greatly enhanced when suitable stability equations are derived from them. These stability equations can be graphed to reveal the control of weathering relationships by the composition of the soil solution. The graphed stability equations are not merely an exercise in algebra, but are shown to represent precipitation and dissolution phenomena of real minerals. This is illustrated for the mineral group consisting of amorphous silica, montmorillonite, kaolinite, and gibbsite. The graphs help clarify field relationships that are incompletely understood and help uncover relationships previously unsuspected. The stability equations can also be used to construct equilibrium composition models for elements in the soil solution. This is a necessary first step to work on the kinetics of approach to composition limits by the soil solution.

Investigation of the clay mineral protection theory for non‐hydrolysable nitrogen in soil

AbstractThe stability of clay minerals and synthetic clay mineral‐nitrogen complexes in boiling 6 N hydrochloric acid was studied to determine whether clay minerals in soil could protect nitrogen compounds or ions from solution.The crystal structure of uncomplexed clay minerals, such as montmorillonite, appeared to be destroyed by boiling acid. Interlamellar ammonium did not reduce the solubility of these clay minerals in boiling acid, nor was the ammonium ion protected from solution. However, a number of organic nitrogen compounds (in particular quaternary ammonium salts) markedly reduced the solubility of montmorillonite. In addition the clay mineral reduced the solubility of organic nitrogen compounds in boiling acid. This reduction in solubility did not appear to be due to humin formation or to adsorption of nitrogen compounds on the amorphous residue produced from acid treatment of montmorillonite. The results suggest that a clay mineral protection theory for non‐hydrolysable nitrogen is tenable.

Clay Mineral Stability and Formation During Weathering

AbstractClay minerals undergo significant changes when exposed to weathering agents. Some of these changes were revealed by studying a sequence of samples collected from weathering profiles developed on shales. Illite and chlorite are modified by the development of expandable layers within the illite and chlorite structures. The suggested mechanism of alteration of chlorite is the oxidation and removal of octahedral iron. Chemical analyses indicate that interlayer potassium is removed from illites. Removal of potassium may be accomplished by an exchange reaction between potassium ions and hydronium ions in the environment.The origin of underclays is controversial. In an attempt to shed some light on this subject, three shale-underelay profiles were studied. The changes in clay minerals from shales to underelays are very similar to those in weathered shale profiles. This similarity lends support to the theory that some underelays are products of weathering.