Reaction of forest floor organic matter at goethite, birnessite and smectite surfaces
TL;DR: In this article, the authors compared the affinity and reactivity of three different minerals for natural organic matter (NOM) in forest floor leachate (FFL) from hardwood and pine forests.
About: This article is published in Geochimica et Cosmochimica Acta.The article was published on 2001-01-01. It has received 334 citations till now. The article focuses on the topics: Goethite & Montmorillonite.
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TL;DR: An overview of the current knowledge on mineral-organic associations can be found in this article, where the authors identify key questions and future research needs, as well as a survey of the existing research work.
Abstract: Minerals and organic matter (OM) may form intricate associations via myriad interactions. In soils, the associations of OM with mineral surfaces are mainly investigated because of their role in determining the long-term retention of OM. OM “must decay in order to release the energy and nutrients that drive live processes all over the planet” ( Janzen, 2006 ). Thus, the processes and mechanisms that retain OM in soil are a central concern to very different branches of environmental research. An agronomist may want to synchronize periods of high nutrient and energy release with the growth stages of a crop. An environmental chemist may wish to either immobilize an organic soil contaminant or enhance its decomposition into less harmful metabolites, while climate scientists need to understand the processes that mediate the production of potent greenhouse gases from decomposing OM. Associations of OM with pedogenic minerals (henceforth termed mineral–organic associations (MOAs)) are known to be key controls in these and many other processes. Here we strive to present an overview of the current knowledge on MOAs and identify key questions and future research needs.
818 citations
TL;DR: In this article, it was shown that oxalic acid (a common exudate) releases organic compounds from protective mineral associations, which can lead to loss of soil carbon.
Abstract: Climate change enhances root exudation of organic compounds into soils and can lead to loss of soil carbon. Research now shows that oxalic acid (a common exudate) releases organic compounds from protective mineral associations.
636 citations
TL;DR: If traditional approaches based on the DLVO-theory can be useful in specific cases, quantitative aggregation models taking into account DOM dynamics, bridging, and disaggregation are needed for a comprehensive modeling of colloids stability in natural media.
Abstract: This contribution critically reviews the state of knowledge on interactions of natural colloids and engineered nanoparticles with natural dissolved organic materials (DOM). These interactions determine the behavior and impact of colloids in natural system. Humic substances, polysaccharides, and proteins present in natural waters adsorb onto the surface of most colloids. We outline major adsorption mechanisms and structures of adsorption layers reported in the literature and discuss their generality on the basis of particle type, DOM type, and media composition. Advanced characterization methods of both DOM and colloids are needed to address insufficiently understood aspects as DOM fractionation upon adsorption, adsorption reversibility, and effect of capping agent. Precise knowledge on adsorption layer helps in predicting the colloidal stability of the sorbent. While humic substances tend to decrease aggregation and deposition through electrostatic and steric effects, bridging-flocculation can occur in th...
562 citations
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 "Reaction of forest floor organic ma..."
...Variable-charge minerals tend to have a higher affinity for carboxyl-rich aromatic substances than for polysaccharide- or protein-type OM (e.g., Kaiser et al., 1996; Chorover and Amistadi, 2001; Kaiser, 2003)....
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TL;DR: Goethite-EPS spectra show emergent vibrations consistent with P-O-Fe bonding, which suggests a role of phosphodiester groups in the adsorption reaction, and ATR-FTIR spectroscopy shows complexation and dissociation of protons on acidic functional groups that result in alpha-helical protein conformation at pH < 2.6 and random coil (unordered) conformation on higher pH (>6.
408 citations
References
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TL;DR: In this paper, a sequence of procedures for identifying an unknown organic liquid using mass, NMR, IR, and UV spectroscopy is presented, along with specific examples of unknowns and their spectra.
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TL;DR: In this article, an introduction to modern soil chemistry describes chemical processes in soils in terms of established principles of inorganic, organic, and physical chemistry, providing an understanding of the structure of the solid mineral and organic materials from which soils are formed.
Abstract: This introduction to modern soil chemistry describes chemical processes in soils in terms of established principles of inorganic, organic, and physical chemistry. The text provides an understanding of the structure of the solid mineral and organic materials from which soils are formed, and explains such important processes as cation exchange, chemisorption and physical absorption of organic and inorganic ions and molecules, soil acidification and weathering, oxidation-reduction reactions, and development of soil alkalinity and swelling properties. Environmental rather than agricultural topics are emphasized, with individual chapters on such pollutants as heavy metals, trace elements, and inorganic chemicals.
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TL;DR: Theoretical analysis of molecular vibrational and rotational spectra has been studied in this paper, with a focus on the Vibrational Origin of Group Frequencies (VIB).
Abstract: Vibrational and Rotational Spectra. IR Experimental Considerations. Molecular Symmetry. The Vibrational Origin of Group Frequencies. Methyl and Methylene Groups. Triple Bonds and Cumulated Double Bonds. Olefin Groups. Aromatic and Heteroaromatic Rings. Carbonyl Compounds. Ethers, Alcohols, and Phenols. Amines, C=N, and N=O Compounds. Compounds Conking Boron, Silicon, Phosphorus, Sulfur, or Halogen. Major Spectra-Structure Correlations by Spectral Regions. The Theoretical Analysis of Molecular Vibrations.
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TL;DR: In this article, a spectrometric identification of organic compounds can help to solve the problem of where to get the ideas for a novel, and it can be one of the right sources to develop a writing skill.
2,205 citations