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Title: Molecular Siganture and Sources of Biochemical Recalcitrance of Organic C in Amozonian Dark Earths

Abstract

Amazonian Dark Earths (ADE) are a unique type of soils developed through intense anthropogenic activities that transformed the original soils into Anthrosols throughout the Brazilian Amazon Basin. We conducted a comparative molecular-level investigation of soil organic C (SOC) speciation in ADE (ages between 600 and 8700 years B.P.) and adjacent soils using ultraviolet photo-oxidation coupled with {sup 13}C cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR), synchrotron-based Fourier transform infrared-attenuated total reflectance (Sr-FTIR-ATR) and C (1s) near edge X-ray absorption fine structure (NEXAFS) spectroscopy to obtain deeper insights into the structural chemistry and sources of refractory organic C compounds in ADE. Our results show that the functional group chemistry of SOC in ADE was considerably different from adjacent soils. The SOC in ADE was enriched with: (i) aromatic-C structures mostly from H- and C-substituted aryl-C, (ii) O-rich organic C forms from carboxylic-C, aldehyde-C, ketonic-C and quinine-C, and (iii) diverse group of refractory aliphatic-C moieties. The SOC in adjacent soils was predominantly composed of O-alkyl-C and methoxyl-C/N-alkyl-C structures and elements of labile aliphatic-C functionalities. Our study suggests that the inherent molecular structures of organic C due to selective accumulation of highly refractory aryl-C structures seems to be the key factormore » for the biochemical recalcitrance and stability of SOC in ADE. Anthropogenic enrichment with charred carbonaceous residues from biomass-derived black C (BC) is presumed to be the precursor of these recalcitrant polyaromatic structures. Our results also highlight the complementary role that might be played by organic C compounds composed of O-containing organic C moieties and aliphatic-C structures that persisted for millennia in these anthropic soils as additional or secondary sources of chemical recalcitrance of SOC in ADE. These organic C compounds could be the products of: (i) primary recalcitrant biomolecules from non-BC sources or (ii) secondary processes involving microbial mediated oxidative or extracellular neoformation reactions of SOC from BC and non-BC sources; and stabilized through physical inaccessibility to decomposers due to sorption onto the surface or into porous structures of BC particles, selective preservation or through intermolecular interactions involving clay and BC particles.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929866
Report Number(s):
BNL-80438-2008-JA
Journal ID: ISSN 0016-7037; GCACAK; TRN: US200822%%1056
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; Journal Volume: 71
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ABSORPTION; BUILDUP; CHEMISTRY; CLAYS; ELEMENTS; FINE STRUCTURE; INTERACTIONS; MOLECULAR STRUCTURE; NUCLEAR MAGNETIC RESONANCE; PARTICLES; PRECURSOR; PRESERVATION; RESIDUES; SOILS; SORPTION; SPECTROSCOPY; STABILITY; SURFACES; national synchrotron light source

Citation Formats

Solomon,D., Lehmann, J., Thies, J., Schafer, T., Liang, B., Kinyangi, J., Neves, E., Peterson, J., Liuzao, F., and Skjemstad, J. Molecular Siganture and Sources of Biochemical Recalcitrance of Organic C in Amozonian Dark Earths. United States: N. p., 2007. Web. doi:10.1016/j.gca.2007.02.014.
Solomon,D., Lehmann, J., Thies, J., Schafer, T., Liang, B., Kinyangi, J., Neves, E., Peterson, J., Liuzao, F., & Skjemstad, J. Molecular Siganture and Sources of Biochemical Recalcitrance of Organic C in Amozonian Dark Earths. United States. doi:10.1016/j.gca.2007.02.014.
Solomon,D., Lehmann, J., Thies, J., Schafer, T., Liang, B., Kinyangi, J., Neves, E., Peterson, J., Liuzao, F., and Skjemstad, J. Mon . "Molecular Siganture and Sources of Biochemical Recalcitrance of Organic C in Amozonian Dark Earths". United States. doi:10.1016/j.gca.2007.02.014.
@article{osti_929866,
title = {Molecular Siganture and Sources of Biochemical Recalcitrance of Organic C in Amozonian Dark Earths},
author = {Solomon,D. and Lehmann, J. and Thies, J. and Schafer, T. and Liang, B. and Kinyangi, J. and Neves, E. and Peterson, J. and Liuzao, F. and Skjemstad, J.},
abstractNote = {Amazonian Dark Earths (ADE) are a unique type of soils developed through intense anthropogenic activities that transformed the original soils into Anthrosols throughout the Brazilian Amazon Basin. We conducted a comparative molecular-level investigation of soil organic C (SOC) speciation in ADE (ages between 600 and 8700 years B.P.) and adjacent soils using ultraviolet photo-oxidation coupled with {sup 13}C cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR), synchrotron-based Fourier transform infrared-attenuated total reflectance (Sr-FTIR-ATR) and C (1s) near edge X-ray absorption fine structure (NEXAFS) spectroscopy to obtain deeper insights into the structural chemistry and sources of refractory organic C compounds in ADE. Our results show that the functional group chemistry of SOC in ADE was considerably different from adjacent soils. The SOC in ADE was enriched with: (i) aromatic-C structures mostly from H- and C-substituted aryl-C, (ii) O-rich organic C forms from carboxylic-C, aldehyde-C, ketonic-C and quinine-C, and (iii) diverse group of refractory aliphatic-C moieties. The SOC in adjacent soils was predominantly composed of O-alkyl-C and methoxyl-C/N-alkyl-C structures and elements of labile aliphatic-C functionalities. Our study suggests that the inherent molecular structures of organic C due to selective accumulation of highly refractory aryl-C structures seems to be the key factor for the biochemical recalcitrance and stability of SOC in ADE. Anthropogenic enrichment with charred carbonaceous residues from biomass-derived black C (BC) is presumed to be the precursor of these recalcitrant polyaromatic structures. Our results also highlight the complementary role that might be played by organic C compounds composed of O-containing organic C moieties and aliphatic-C structures that persisted for millennia in these anthropic soils as additional or secondary sources of chemical recalcitrance of SOC in ADE. These organic C compounds could be the products of: (i) primary recalcitrant biomolecules from non-BC sources or (ii) secondary processes involving microbial mediated oxidative or extracellular neoformation reactions of SOC from BC and non-BC sources; and stabilized through physical inaccessibility to decomposers due to sorption onto the surface or into porous structures of BC particles, selective preservation or through intermolecular interactions involving clay and BC particles.},
doi = {10.1016/j.gca.2007.02.014},
journal = {Geochimica et Cosmochimica Acta},
number = ,
volume = 71,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}