The Clay Mineral Composition of Representative Soils from Five Geological Regions of Texas
01 Feb 1954-Clays and Clay Minerals (Springer Science and Business Media LLC)-Vol. 3, Iss: 1, pp 373-383
TL;DR: In this paper, mineralogical studies for the <2 μ fractions are presented for seventeen soil profiles and two surface horizon samples, which represent eight soil types and five geological regions in the state.
Abstract: Mineralogical studies for the <2 μ fractions are presented for seventeen soil profiles and two surface horizon samples, which represent eight soil types and five geological regions in the state. There was no evidence of clay mineral formation in the upper 6 feet or more of soil. X-ray diffraction data from the Lufkin, Ruston and Katy soils suggested some decomposition of montmorillonite and kaolinite in the upper horizon. However, the overall picture is one of little change in clay mineral composition between the soils and parent sediments.
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11 Sep 2018
253 citations
TL;DR: The 2: 2 lattice building phenomenon in expansible 2: 1 layer silicates relates to layer charge density and crystal size and frequently tends to inhibit the formation of free gibbsite in soil chemical weathering so long as there are expansible layer silicate present to become intercalated with aluminum hydroxide, a weathering phenomenon that may be called an antigibbsite effect as discussed by the authors.
Abstract: Interlayering of 2: 1 layer silicates varies as a function of chemical weathering from the simple, homogeneous K or Na interlayers of micas to the heterogeneous systems of mica intercalated with expanded 2: 1 layer silicates. “Frayed edge” type of weathering at dislocation planes of mica is collated with K release and preferential cation-exchange uptake of K relative to Ca by such expansible layer silicate systems; mica islands maintain alignment of the silica sheet cavities, which facilitates recapture of lattice K. Intercalation of the expanded 2: 1 layer silicates with alumina interlayers appears to be a characteristic function of chemical weathering in soils, with the formation of 2: 1–2: 2 intergrades not only of 14 A spacing but also of swelling 18 A types that give small 12, 14, 18 A and higher spacing peaks (along with the 10 A peak) at 550°C. Interlayer precipitates appear to be characteristic of soil clays, contrasting with “pure” minerals of deposits developed in less “open” environments than those of soils. The “2: 2 lattice building” phenomenon in expansible 2: 1 layer silicates relates to layer charge density and crystal size, and frequently tends to inhibit the formation of free gibbsite in soil chemical weathering so long as there are expansible layer silicates present to become intercalated with aluminum hydroxide—a weathering phenomenon that may be called an “antigibbsite effect”. Accumulation of alumina (possibly with some iron, magnesium, and allophane) as interlayers in 2: 1 minerals of soils is seen as a genetic stage in the 2: 2 → 1: 1 weathering sequence through which kaolinite and halloysite develop in soils.
224 citations
TL;DR: The results indicate that C60 released to the environment will not be highly bioavailable but will likely persist in soil for extended periods, suggesting high resistance of C60 to mineralization in soil.
Abstract: Assessments of potential exposure to fullerenes and their derivatives in the environment are important, given their increasing production and use. Our study focused on fate processes that determine the movement and bioavailability of fullerenes in soil. We evaluated the sorption, biodegradation, and plant uptake of C60 fullerene using (14)C-labeled C60 solutions in water produced by either solvent exchange with tetrahydrofuran or sonication/extended mixing in water. Organic carbon appeared to have an important influence on C60 soil sorption. The log Koc values for (14)C60 were equivalent for sandy loam and silt loam (3.55 log[mL/g]) but higher for loam (4.00 log[mL/g]), suggesting that other factors, such as pH, clay content and mineralogy, and cation exchange capacity, also influence C60 soil sorption. There was little (14)CO2 production in the silt loam or the sandy loam soil after 754 and 328 days, respectively, suggesting high resistance of C60 to mineralization in soil. Plant uptake was generally low (∼7%), with most of the uptaken (14)C accumulating in the roots (40-47%) and smaller amounts of accumulation in the tuber (22-23%), stem (12-16%), and leaves (18-22%). Our results indicate that C60 released to the environment will not be highly bioavailable but will likely persist in soil for extended periods.
90 citations
TL;DR: In this article, it was shown that the detrital basic lattice is not altered to a measurable extent in Recent marine sediments. But, it remains to be proved whether this is caused by chemical modification of the basic lattices with burial, or if the Detrital clay lattice has the inherent ability to contract, without chemical rearrangement, when buried to a sufficient depth.
Abstract: Studies of the Recent indicate that, at the most, somewhat less than half the clay minerals are altered to any extent in a marine environment. Probably most of this alteration is in the form of cation adsorption or reconstitution of slightly weathered illites and chlorites to their original form. There appears to be little if any evidence that the detrital basic lattice is being altered to a measurable extent in Recent marine sediments. In the near-shore environments there is usually a coincidence of clay mineral suites and environments. A major change in the clay mineral composition of sedimentary rock occurs within the Mississippian. Illite is the dominant clay mineral of the pre-Upper Mississippian sediments. Post-Lower Mississippian clay suites are more variable in composition; illite becomes less abundant and montmorillonite and kaolinite more abundant. This change is best related to a change in regional tectonics. The clay minerals seem to have no preferred lithologie associations, although owing to epigenetie alterations porous sandstones commonly have different clay mineral suites from those of adjacent shales and carbonate rocks. In many instances clay mineral facies coincide with environmental facies. As the clay mineral criteria for distinguishing any given type environment are extremely variable, it is thought that segregation of clay mineral suites by sorting is usually more effective than by diagenesis. Expanded clay minerals appear to be partially contracted by the time they have been buried to 10,000–15,000 ft. It remains to be proved whether this is caused by chemical modification of the basic lattice with burial or if the detrital clay lattice has the inherent ability to contract, without chemical rearrangement, when buried to a sufficient depth.
85 citations
01 Jan 1965
TL;DR: In this paper, the authors present a plan of study for the analysis of mineralogy in terms of exchange capacity and sample treatment, and propose a method of analysis for this purpose.
Abstract: _-------______--_______ Introduction. _____________________ Purpose and significance of study Plan of study_____ _ _________ Previous work _ __ _ __________ Acknowledgments __ --------_Methods of analysis __ -_-------_-__ Sample treatment __ _ __________ Exchange capacity. . ____________ Mineralogy ____________________
62 citations
References
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TL;DR: In this article, a procedure is presented which employs sodium dithionite (Na2S2O4, hyposulfite, or "hydrosulfite") as the reductor, and 0.3 molar citrate with or without Fe-3 specific Versene as the chelating reagent.
Abstract: Iron oxide coatings or crystals must be removed from soils in which they are found in many mineralogical techniques for identification of colloidal layer silicates as well as the identification of silt and sand grains with the polarizing microscope. A procedure is presented which employs sodium dithionite (Na2S2O4, hyposulfite, or "hydrosulfite") as the reductor, and 0.3 molar citrate with or without Fe-3 specific Versene as the chelating reagent. It is a neutral system the pH of which is kept at 7.3. The reaction is fast, as much as 20% of iron oxides (hematite, geothite, or limonite but not magnetite or ilmenite) being removed from a soil in 15 minutes, and does not precipitate either elemental sulfur or iron sulfides. Like other procedures, it causes some decrease of exchange capacity of layer silicates which contain iron, and at the same time may increase the exchange capacity of kaolinic soils. View complete article To view this complete article, insert Disc 2 then click button8
274 citations