The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Philippe Van Cappellen - One of the best experts on this subject based on the ideXlab platform.
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degradation of natural Organic Matter a thermodynamic analysis
Geochimica et Cosmochimica Acta, 2011Co-Authors: Douglas E Larowe, Philippe Van CappellenAbstract:Abstract The oxidative degradation of Organic Matter is a key process in the biogeochemical functioning of the earth system. Quantitative models of Organic Matter degradation are therefore essential for understanding the chemical state and evolution of the Earth’s near-surface environment, and to forecast the biogeochemical consequences of ongoing regional and global change. The complex nature of biologically produced Organic Matter represents a major obstacle to the development of such models, however. Here, we compare the energetics of the oxidative degradation of a large number of naturally occurring Organic compounds. By relating the Gibbs energies of half reactions describing the complete mineralization of the compounds to their average nominal carbon oxidation state, it becomes possible to estimate the energetic potential of the compounds based on major element (C, H, N, O, P, S) ratios. The new energetic description of Organic Matter can be combined with bioenergetic theory to rationalize observed patterns in the decomposition of natural Organic Matter. For example, the persistence of cell membrane derived compounds and complex Organics in anoxic settings is consistent with their limited catabolic potential under these environmental conditions. The proposed approach opens the way to include the thermodynamic properties of Organic compounds in kinetic models of Organic Matter degradation.
Douglas E Larowe - One of the best experts on this subject based on the ideXlab platform.
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degradation of natural Organic Matter a thermodynamic analysis
Geochimica et Cosmochimica Acta, 2011Co-Authors: Douglas E Larowe, Philippe Van CappellenAbstract:Abstract The oxidative degradation of Organic Matter is a key process in the biogeochemical functioning of the earth system. Quantitative models of Organic Matter degradation are therefore essential for understanding the chemical state and evolution of the Earth’s near-surface environment, and to forecast the biogeochemical consequences of ongoing regional and global change. The complex nature of biologically produced Organic Matter represents a major obstacle to the development of such models, however. Here, we compare the energetics of the oxidative degradation of a large number of naturally occurring Organic compounds. By relating the Gibbs energies of half reactions describing the complete mineralization of the compounds to their average nominal carbon oxidation state, it becomes possible to estimate the energetic potential of the compounds based on major element (C, H, N, O, P, S) ratios. The new energetic description of Organic Matter can be combined with bioenergetic theory to rationalize observed patterns in the decomposition of natural Organic Matter. For example, the persistence of cell membrane derived compounds and complex Organics in anoxic settings is consistent with their limited catabolic potential under these environmental conditions. The proposed approach opens the way to include the thermodynamic properties of Organic compounds in kinetic models of Organic Matter degradation.
Philip A. Meyers - One of the best experts on this subject based on the ideXlab platform.
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Sediment Organic Matter
Tracking Environmental Change Using Lake Sediments, 2020Co-Authors: Philip A. Meyers, Jane L. TeranesAbstract:The Organic Matter content of lake sediments provides a variety of indicators, or proxies, that can be used to reconstruct paleoenvironments of lakes and their watersheds and to infer histories of regional climate changes. Organic Matter constitutes a minor but important fraction of lake sediments. It originates from the complex mixture of lipids, carbohydrates, proteins, and other Organic Matter components produced by organisms that have lived in and around the lake (e.g., Meyers, 1997; Rullkotter, 2000). As an accumulation of “geochemical fossils”, the Organic Matter content of lake sediments provides information that is important to interpretations of both natural and human-induced changes in local and regional ecosystems.
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preservation of elemental and isotopic source identification of sedimentary Organic Matter
Chemical Geology, 1994Co-Authors: Philip A. MeyersAbstract:The amount and type of Organic Matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records. Only a small fraction of the initial aquatic Organic Matter survives destruction and alteration during sinking and sedimentation. Selective degradation modifies the character of the surviving small fraction of Organic Matter which becomes incorporated in bottom sediments. Organic Matter alterations can continue to sub-bottom depths of hundreds of meters, corresponding to millions of years. Source and paleoenvironmental information nonetheless remains preserved in the molecular, elemental and isotopic compositions of Organic Matter. C/N- and δ13C-values of total Organic Matter, in particular, appear to retain paleoenvironmental information for multi-Myr time periods.
Markus Kleber - One of the best experts on this subject based on the ideXlab platform.
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The contentious nature of soil Organic Matter
Nature, 2015Co-Authors: Johannes Lehmann, Markus KleberAbstract:The exchange of nutrients, energy and carbon between soil Organic Matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil Organic Matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil Organic Matter is a continuum of progressively decomposing Organic compounds. We discuss implications of this view of the nature of soil Organic Matter for aquatic health, soil carbon-climate interactions and land management.
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the contentious nature of soil Organic Matter
Nature, 2015Co-Authors: Johannes Lehmann, Markus KleberAbstract:Instead of containing stable and chemically unique ‘humic substances’, as has been widely accepted, soil Organic Matter is a mixture of progressively decomposing Organic compounds; this has broad implications for soil science and its applications. The exchange of nutrients, energy and carbon between soil Organic Matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil Organic Matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil Organic Matter is a continuum of progressively decomposing Organic compounds. We discuss implications of this view of the nature of soil Organic Matter for aquatic health, soil carbon–climate interactions and land management. Soil Organic Matter contains a large portion of the world's carbon and plays an important role in maintaining productive soils and water quality. Nevertheless, a consensus on the nature of soil Organic Matter is lacking. Johannes Lehmann and Markus Kleber argue that soil Organic Matter should no longer be seen as large and persistent, chemically unique substances, but as a continuum of progressively decomposing Organic compounds.
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What is recalcitrant soil Organic Matter?
Environmental Chemistry, 2010Co-Authors: Markus KleberAbstract:Environmental context.On a global scale, soils store more carbon than plants or the atmosphere. The cycling of this vast reservoir of reduced carbon is closely tied to variations in environmental conditions, but robust predictions of climate–carbon cycle feedbacks are hampered by a lack of mechanistic knowledge regarding the sensitivity of Organic Matter decomposition to rising temperatures. This text provides a critical discussion of the practice to conceptualise parts of soil Organic Matter as intrinsically resistant to decomposition or ‘recalcitrant’. Abstract.The understanding that some natural Organic molecules can resist microbial decomposition because of certain molecular properties forms the basis of the biogeochemical paradigm of ‘intrinsic recalcitrance’. In this concept paper I argue that recalcitrance is an indeterminate abstraction whose semantic vagueness encumbers research on terrestrial carbon cycling. Consequently, it appears to be advantageous to view the perceived ‘inherent resistance’ to decomposition of some forms of Organic Matter not as a material property, but as a logistical problem constrained by (i) microbial ecology; (ii) enzyme kinetics; (iii) environmental drivers; and (iv) matrix protection. A consequence of this view would be that the frequently observed temperature sensitivity of the decomposition of Organic Matter must result from factors other than intrinsic molecular recalcitrance.
Han Linlin - One of the best experts on this subject based on the ideXlab platform.
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A novel type of oil-generating Organic Matter: crystal-enclosed Organic Matter
Chinese Journal of Geochemistry, 1992Co-Authors: Zhou Zhongyi, Pei Cunmin, Zhu Yangming, Fan Shanfa, Han LinlinAbstract:The comparative study of Organic Matter in carbonate rocks and argillaceous rocks from the same horizon indicates that the Organic thermal maturities of carbonate rocks are much lower than those of argillaceous rocks. And extensive analysis of extracted and inclused Organic Matter from the same sample shows that inclused Organic Matter is different from extracted Organic Matter, and the thermal maturity of the former is usually lower than that of the latter in terms of biomarker structural parameters. It seems that carbonate minerals could preserve Organic Matter and retard Organic maturation. The inclused Organic Matter, abundant in most carbonate rocks, will be released from minerals and transformed into oil and gas during the high thermal maturity stage.
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A novel type of oil-generating Organic Matter — Crystal-enclosed Organic Matter
Chinese Journal of Geochemistry, 1992Co-Authors: Zhou Zhongyi, Pei Cunmin, Zhu Yangming, Fan Shanfa, Han LinlinAbstract:The comparative study of Organic Matter in carbonate rocks and argillaceous rocks from the same horizon indicates that the Organic thermal maturities of carbonate rocks are much lower than those of argillaceous rocks. And extensive analysis of extracted and inclused Organic Matter from the same sample shows that inclused Organic Matter is different from extracted Organic Matter, and the thermal maturity of the former is usually lower than that of the latter in terms of biomarker structural parameters. It seems that carbonate minerals could preserve Organic Matter and retard Organic maturation. The inclused Organic Matter, abundant in most carbonate rocks, will be released from minerals and transformed into oil and gas during the high thermal maturity stage.