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Book Chapter

Humic Fractions and the Nature of Organic Materials in Intimate Association with Soil Clays

By
Michael H.B. Hayes
Michael H.B. Hayes
Chemicaland Environmental Sciences, University of Limerick, Ireland E-mail: michael.h.hayes@ul.ie
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Guixue Song
Guixue Song
Chemicaland Environmental Sciences, University of Limerick, Ireland E-mail: michael.h.hayes@ul.ie
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Andre J. Simpson
Andre J. Simpson
Department of Chemistry, University of Toronto at Scarborough, Canada
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Published:
January 01, 2009

Abstract

For any consideration of the organic matter in intimate association with the surface of soil clays it is appropriate to consider first the totality of the organic matter in the soil. The term “soil organic matter” (SOM), according to Stevenson (1994), refers to “the whole of the organic matter in soils, including the litter, the light fraction, the microbial biomass, the water-soluble organics, and the stabilized organic matter (humus)”. Nowadays, the term natural organic matter (NOM) is widely used for the natural organic components in soils, sediments, and waters.

On the basis of earlier definitions by Kononova (1966), Hayes and Swift (1978) considered the complete soil organic fraction to be made up of live organisms and plants within the soil, and their undecomposed, partly decomposed, and completely transformed remains. However, they regarded SOM to be a more specific term for the non-living components that may be described as “a heterogeneous mixture composed largely of products resulting from microbial and chemical transformation of organic debris.” The transformation, or the humification process, gives rise to the final product, humus, a mixture of substances with some resistance to further degradation. This definition is similar to that of Stevenson who considered humus to be the total of organic compounds in soil exclusive of undecayed plant and animal tissues, their partial ‘decomposition’ products, and the soil biomass. Stevenson partitioned SOM into the “active” (or labile) and the “stable” pools. The “active fraction” contains the macro-organic (or particulate) matter and the

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Contents

Clay Minerals Society Workshop Lectures 16

Carbon Stabilization by Clays in the Environment: Process and Characterization Methods

David A. Laird
David A. Laird
USDA, ARS, National Soil Tilth Laboratory 2110 University Blvd Ames IA 50011-3120 USA
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Javiera Cervini Silva
Javiera Cervini Silva
Instituto de Geografia Universidad Nacional Autónoma de México Ciudad Universitaria, Mexico City
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Yona Chen
Yona Chen
The Hebrew University of Jerusalem, Israel
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Claire Chenu
Claire Chenu
CNRS-UPMC-INRA-AgroParisTech-ENS-ENPC, Grignon, France
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Françoise Elsass
Françoise Elsass
Centre de Géochimie de la Surface, Strasbourg, France
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Javier M. Gonzalez
Javier M. Gonzalez
USDA, ARS, NAA, AFSRC, Beaver, WV, USA
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Michael H.B. Hayes
Michael H.B. Hayes
University of Limerick, Ireland
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David A. Laird
David A. Laird
USDA, ARS, NSTL, Ames, IA, USA
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Alain Plante
Alain Plante
University of Pennsylvania, Philadelphia, PA, USA
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Andre J. Simpson
Andre J. Simpson
University of Toronto at Scarborough, Canada
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Guixue Song
Guixue Song
University of Limerick, Ireland
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Jorge Tarcjotzly
Jorge Tarcjotzly
The Hebrew University of Jerusalem
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Michael L. Thompson
Michael L. Thompson
Iowa State University, Ames IA, USA
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I. Virto
I. Virto
CNRS-UPMC-INRA-AgroParisTech-ENS-ENPC, Grignon, France
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Robert L. Wershaw
Robert L. Wershaw
U.S. Geological Survey, Denver, CO, USA
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Clay Minerals Society
ISBN electronic:
9781881208365
Publication date:
January 01, 2009

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