Is the geological concept of clay minerals appropriate for soil science? A literature-based and philosophical analysis
TL;DR: In this paper, data from Australia, New Zealand and Iran were examined and compared with those for reference clay minerals of the same types to determine the extent to which the nature and properties of secondary clay-size minerals in soils could be explained by those of clay minerals with the same name from non-soil, geology environments.
Abstract: Data in the literature for soils that are dominated by each of the main types of clay minerals were examined and compared with those for reference clay minerals of the same types to determine the extent to which the nature and properties of clay-size minerals in soils could be explained by those of clay minerals with the same name from non-soil, ‘geological’ environments. Published information on soils from Australia, New Zealand and Iran was sourced for this study. The clay fractions of each of the soils are dominated by either one of the common phyllosilicates: kaolinite, halloysite, illite/mica, vermiculite, smectite, and palygorskite, or by the nanocrystalline mineral, allophane. Data for samples of kaolinite that had been extracted from soils from several countries (Australia, Thailand, Indonesia and Brazil) and purified before characterization have also been examined. In soils, each dominant clay mineral is generally associated with other materials, including iron oxides, other phyllosilicates and/or nanocrystalline minerals and organic matter. As the most studied example of an extracted phyllosilicate, kaolinite shows a wide range of properties in different soils, but a narrower range of properties within a particular locality. However, almost all of the soil kaolinites studied have larger specific surface areas and higher cation exchange capacities than reference kaolinites. The literature also reveals that, among phyllosilicates in soils, illites have a wide range of potassium contents, expandable minerals (vermiculites and smectites) may be interlayered by hydroxy-Al species particularly, and smectitic layers often occur interstratified with other layers, including those of illite, kaolinite and halloysite. The variability of soil phyllosilicates and their common association with other, often poorly crystallized but highly reactive minerals and compounds can be explained by their formation in the highly heterogeneous and dynamic soil environment. Phyllosilicates from non-soil or geological sources are poor models for the representation of secondary clay-size minerals in soils. In philosophical terms, the reduction of soil mineralogy to mineralogy as it is practiced within geology is misleading because of the differences between the minerals formed in soil and geological environments. In other words, clay minerals as they are defined as mineralogical entities for geology are of a different ‘kind’ to clay minerals in soils and cannot serve as ‘types’ or ‘stereotypes’ to enable explanation of the contribution of secondary clay-size minerals to soil properties or behavior. It is more useful to view clay minerals in soils as secondary inorganic compounds of clay-size than to follow their definition for non-soil purposes as plastic phyllosilicate minerals.
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TL;DR: In this paper, a harmonized concept for aggregates in soils is proposed that explicitly considers the structure and build-up of microaggregates and the role of organo-mineral associations.
Abstract: All soils harbor microaggregates, i.e., compound soil structures smaller than 250 µm. These microaggregates are composed of diverse mineral, organic and biotic materials that are bound together during pedogenesis by various physical, chemical and biological processes. Consequently, microaggregates can withstand strong mechanical and physicochemical stresses and survive slaking in water, allowing them to persist in soils for several decades. Together with the physiochemical heterogeneity of their surfaces, the three-dimensional structure of microaggregates provides a large variety of ecological niches that contribute to the vast biological diversity found in soils. As reported for larger aggregate units, microaggregates are composed of smaller building units that become more complex with increasing size. In this context, organo-mineral associations can be considered structural units of soil aggregates and as nanoparticulate fractions of the microaggregates themselves. The mineral phases considered to be the most important as microaggregate forming materials are the clay minerals and Fe- and Al-(hydr)oxides. Within microaggregates, minerals are bound together primarily by physicochemical and chemical interactions involving cementing and gluing agents. The former comprise, among others, carbonates and the short-range ordered phases of Fe, Mn, and Al. The latter comprise organic materials of diverse origin and probably involve macromolecules and macromolecular mixtures. Work on microaggregate structure and development has largely focused on organic matter stability and turnover. However, little is known concerning the role microaggregates play in the fate of elements like Si, Fe, Al, P, and S. More recently, the role of microaggregates in the formation of microhabitats and the biogeography and diversity of microbial communities has been investigated. Little is known regarding how microaggregates and their properties change in time, which strongly limits our understanding of micro-scale soil structure dynamics. Similarly, only limited information is available on the mechanical stability of microaggregates, while essentially nothing is known about the flow and transport of fluids and solutes within the micro- and nanoporous microaggregate systems. Any quantitative approaches being developed for the modeling of formation, structure and properties of microaggregates are, therefore, in their infancy. We respond to the growing awareness of the importance of microaggregates for the structure, properties and functions of soils by reviewing what is currently known about the formation, composition and turnover of microaggregates. We aim to provide a better understanding of their role in soil function, and to present the major unknowns in current microaggregate research. We propose a harmonized concept for aggregates in soils that explicitly considers the structure and build-up of microaggregates and the role of organo-mineral associations. We call for experiments, studies and modeling endeavors that will link information on aggregate forming materials with their functional properties across a range of scales in order to better understand microaggregate formation and turnover. Finally, we hope to inspire a novel cohort of soil scientists that they might focus their research on improving our understanding of the role of microaggregates within the system of aggregates and so help to develop a unified and quantitative concept of aggregation processes in soils.
515 citations
Cites background from "Is the geological concept of clay m..."
...Their common association with other, often poorly crystallized but highly reactive minerals can be explained by their formation in the highly heterogeneous and dynamic soil environment (Churchman, 2010b)....
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...…primary minerals leads to the formation of highly reactive secondary clay-sized minerals in soils that contain a variety of phyllosilicates associated with short-range ordered phases, including metal oxides and hydroxides as well as aluminosilicates (Churchman, 2010b; Basile-Doelsch et al., 2015)....
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...As such, aggregation is one of the specific and distinct features of soils (Churchman, 2010a)....
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TL;DR: Arsenic was found to be the primary contributor to total risk, accounting of 57.4% of HI in all three- person groupings, and the presence of V, a less-expected element, among those of major risk contribution, reveals the necessity of monitoring areas at large scale.
284 citations
TL;DR: In this paper, the ability of different phyllosilicates to protect soil organic carbon (SOC) from microbial decomposition has been investigated and compared in a limited number of soils.
138 citations
TL;DR: In this article, a review of VNIR spectral features of soil minerals with particular attention to those <2'μm fractions is presented. But the focus of this review is not on the spectral properties of soil, but rather on the application of the spectral features in the context of soil mineralogy.
Abstract: Clay minerals are the most reactive and important inorganic components in soils, but soil mineralogy classifies as a minor topic in soil sciences. Revisiting soil mineralogy has been gradually required. Clay minerals in soils are more complex and less well crystallized than those in sedimentary rocks, and thus, they display more complicated X-ray diffraction (XRD) patterns. Traditional characterization methods such as XRD are usually expensive and time-consuming, and they are therefore inappropriate for large datasets, whereas visible and near-infrared reflectance spectroscopy (VNIR) is a quick, cost-efficient, and nondestructive technique for analyzing soil mineralogic properties of large datasets. The main objectives of this review are to bring readers up to date with information and understanding of VNIR as it relates to soil mineralogy and attracts more attention from a wide variety of readers to revisit soil mineralogy. We begin our review with a description of fundamentals of VNIR. We then review common methods to process soil VNIR spectra and summary spectral features of soil minerals with particular attention to those <2 μm fractions. We further critically review applications of chemometric methods and related model building in spectroscopic soil mineral studies. We then compare spectral measurement with multivariate calibration methods, and we suggest that they both produce excellent results depending on the situation. Finally, we suggest a few avenues of future research, including the development of theoretical calibrations of VNIR more suitable for various soil samples worldwide, better elucidation of clay mineral-soil organic carbon (SOC) interactions, and building the concept of integrated soil mapping through combined information (e.g., mineral composition, soil organic matter-SOM, SOC, pH, and moisture).
99 citations
TL;DR: In this article, a set of batch adsorption-desorption experiments were conducted using pedogenic clays extracted from soils dominated by kaolinite-illite (Kaol-Ill), smectite (Smec), and allophane (Allo).
73 citations
References
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Book•
01 Jan 1996
TL;DR: The Australian Soil Classification as mentioned in this paper provides a framework for organizing knowledge about Australian soils by allocating soils to classes via a key, and has been widely adopted and formally endorsed as the official national system.
Abstract: The Australian Soil Classification provides a framework for organising knowledge about Australian soils by allocating soils to classes via a key. Since its publication in 1996, this book has been widely adopted and formally endorsed as the official national system. It has provided a means of communication among scientists and land managers and has proven to be of particular value in land resource survey and research programs, environmental studies and education.
Classification is a basic requirement of all science and needs to be periodically revised as knowledge increases. This third edition of The Australian Soil Classification includes updates from a working group of the National Committee on Soil and Terrain (NCST). The main change in this edition accommodates new knowledge and understanding of the significance, nature, distribution and refined testing for soils comprising deep sands, leading to the inclusion of a new Order, the Arenosols. The introduction of the Arenosols Order led to a review and changes to Calcarosols, Tenosols and Rudosols.
The Australian Soil Classification is Volume 4 in the Australian Soil and Land Survey Handbook Series.
2,940 citations
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01 Jan 1989
TL;DR: Minerals in soil environments as mentioned in this paper, a.k.a. Minerals in the soil environment, is a type of soil environment that is suitable for mining in soil.
Abstract: Minerals in soil environments , Minerals in soil environments , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
2,217 citations
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01 Jan 1975
TL;DR: In this article, the authors present a review of the concept of a person, the meaning of meaning, and the nature of mental states in the mind of a human being and the mental life of some machines.
Abstract: Introduction 1. Language and philosophy 2. The analytic and synthetic 3. Do true assertions correspond to reality? 4. Some issues in the theory of grammar 5. The 'innateness hypothesis' and explanatory models in linguistics 6. How not to talk about meaning 7. Review of The concept of a person 8. Is semantics possible? 9. The refutation of conventionalism 10. Reply to Gerald Massey 11. Explanation and reference 12. The meaning of 'meaning' 13. Language and reality 14. Philosophy and our mental life 15. Dreaming and 'depth grammar' 16. Brains and behaviour 17. Other minds 18. Minds and machines 19. Robots: machines or artificially created life? 20. The mental life of some machines 21. The nature of mental states 22. Logical positivism and the philosophy of mind Bibliography Index.
1,086 citations
"Is the geological concept of clay m..." refers background in this paper
...According to one view, attributable to Fodor (1974) and Putnam (1975), the assortment or grouping of clay minerals in soils by a pre-determined set of capabilities analogous to functional groups for soil organic matter would represent their characterization as ‘tokens of types’ (Fodor, 1974), or as particular examples of ‘stereoypes’ (Putnam, 1975), albeit that the types and stereotypes representing the soil mineralogical ‘kinds’ in this case...
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...‘stereotypes’, in that of Putnam (Putnam, 1975)....
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Book•
01 Jan 2000
TL;DR: Soil Physics, AW Warrick Physical Properties of Primary Particles Dynamic Properties of Soils Soil Water Content and Water Potential Relationships Soil water movement Energy and Water Balances at Soil-Plant-Atmosphere Interfaces Solute Transport Soil Structure Soil Gas Movement in Unsaturated Systems Soil Spatial Variability Soil Chemistry, PM Huang The Chemical Composition of Soiles Soil Organic Matter The Soil Solution Kinetics and Mechanisms of Soil Chemical Reactions Redox Phenomena Soil Colloidal Behavior Ion Exchange Pehn
Abstract: Soil Physics, AW Warrick Physical Properties of Primary Particles Dynamic Properties of Soils Soil Water Content and Water Potential Relationships Soil Water Movement Energy and Water Balances at Soil-Plant-Atmosphere Interfaces Solute Transport Soil Structure Soil Gas Movement in Unsaturated Systems Soil Spatial Variability Soil Chemistry, PM Huang The Chemical Composition of Soils Soil Organic Matter The Soil Solution Kinetics and Mechanisms of Soil Chemical Reactions Redox Phenomena Soil Colloidal Behavior Ion Exchange Pehnomena Chemisorption and Precipitation Reactions Abiotic Catalysis Soil pH and pH Buffering Soil Biology and Biochemistry, EA Paul Microbiota Soil Fauna Microbially Mediated Processes Nitrogen Transformations Soil Fertility and Plant Nutrition, EJ Kamprath Bioavailability of Major Essential Nutrients Bioavailability of Micronutrients Nutrient Interactions in Soil and Plant Nutrition Soil Fertility Evaluation Fundamentals of Fertilizer Application Nutrient and Water Use Efficiency Pedology, LP Wilding Geomorphology of Soil Landscapes Pedogenic Processes Pedological Modeling Soil Taxonomy Other Systems of Soil Classification Classification of Soils Land Evaluation for Landscape Units Soil Mineralogy, JW Stucki The Alteration and Formation of Soil Minerals by Weathering Phyllosilicates Oxide Minerals Poorly Crystalline Aluminosilicate Clays Interdiscipinary Aspects of Soil Science, I Shainberg Salinity Sodicity Hardsetting Soils Biogeochemistry of Wetlands Acid Sulfate Soils Soils and Environmental Quality Water Erosion Wind Erosion Land Application of Wastes Conservation Tillage Soil Quality Soil Databases, M F Baumgardner From the Soil Map of the World to the Digital Global Soil and Terrain Database: 1960-2002 SOTER: The World Soils and Terrain Database Development of a 05 Degrees by 05 Degrees Resolution Global Database The Canadian Soil Database United States Soil Survey Database The Use of Soil Databases in Resource Assessments
1,028 citations