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Title: Molecular structure in soil humic substances: The new view

A critical examination of published data obtained primarily from recent nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopy, electrospray ionization-mass spectrometry, and pyrolysis studies reveals an evolving new view of the molecular structure of soil humic substances. According to the new view, humic substances are collections of diverse, relatively low molecular mass components forming dynamic associations stabilized by hydrophobic interactions and hydrogen bonds. These associations are capable of organizing into micellar structures in suitable aqueous environments. Humic components display contrasting molecular motional behavior and may be spatially segregated on a scale of nanometers. Within this new structural context, these components comprise any molecules intimately associated with a humic substance, such that they cannot be separated effectively by chemical or physical methods. Thus biomolecules strongly bound within humic fractions are by definition humic components, a conclusion that necessarily calls into question key biogeochemical pathways traditionally thought to be required for the formation of humic substances. Further research is needed to elucidate the intermolecular interactions that link humic components into supramolecular associations and to establish the pathways by which these associations emerge from the degradation of organic litter.
Authors:
;
Publication Date:
OSTI Identifier:
925419
Report Number(s):
LBNL-59827
Journal ID: ISSN 0013-936X; ESTHAG; TRN: US200807%%344
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 39; Journal Issue: 23; Related Information: Journal Publication Date: 2005
Research Org:
COLLABORATION - UCBerkeley
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ABSORPTION; HYDROGEN; MOLECULAR STRUCTURE; NUCLEAR MAGNETIC RESONANCE; ORGANIZING; PYROLYSIS; SOILS; SPECTROSCOPY