TY - JOUR
T1 - Micro- and nano-environments of C sequestration in soil
T2 - A multi-elemental STXM-NEXAFS assessment of black C and organomineral associations
AU - Solomon, Dawit
AU - Lehmann, Johannes
AU - Wang, Jian
AU - Kinyangi, James
AU - Heymann, Karen
AU - Lu, Yingshen
AU - Wirick, Sue
AU - Jacobsen, Chris
N1 - Funding Information:
This study was supported by grants from the Agriculture and Food Research Initiative Competitive Grant of the National Institute of Food and Agriculture (NIFA) ( 2008-35107-04511 ) and the Geobiology and Low-Temperature Geochemistry Program of the National Science Foundation (NSF) ( EAR-0819689 ). The opinions and findings expressed in this material are those of the authors and do not reflect the views of NIFA or NSF. The C K-edge NEXAFS was recorded at X1A1 beamline of the National Synchrotron Light Source (NSLS). The N, Al, Si K-edge, and Ca and Fe L-edge NEXAFS were performed at SM 10ID-1 beamline of the Canadian Light Source (CLS).
PY - 2012/11/1
Y1 - 2012/11/1
N2 - Black C is an essential component of the terrestrial C pool and its formation is often credited as a CO2 sink by transferring the fast-cycling C from the atmosphere-biosphere system into slower cycling C in the geosphere. This study is the first multi-element K- (C, N, Ca, Fe, Al and Si) soft-X-ray STXM-NEXAFS investigation conducted at a submicron-scale spatial resolution specifically targeting black C and its interaction with the mineral and non-black C organic matter in the organomineral assemblage. The STXM-NEXAFS micrographs and spectra demonstrated that pyrogenic C was dominated by quinoide, aromatic, phenol, ketone, alcohol, carboxylic and hydroxylated- and ether-linked C species. There was also evidence for the presence of pyridinic, pyridonic, pyrrolic, amine and nitril N functionalities. The non-black C organic matter contained amino acids, amino sugars, nucleic acids and polysaccharides known to exhibit negatively charged carboxylic, phenolic, enolic, thiolate and phosphate functionalities highly reactive towards metal ions and black C. The metal-rich mineral matrix was composed of phyllosilicate clay minerals, Fe and Al hydroxypolycations, oxides, hydroxides and oxyhydroxide that can attract and bind organic biopolymers. STXM-NEXAFS provided evidence for interactive association between pyrogenic C, non-black C organic matter and the mineral oxide and oxyhydroxide communities in the organomineral interface. These intimate associations occurred through a "two-way" direct linkage between black C and the mineral or non-black C organic matter or via a "three-way" indirect association where non-black C organic matter could serve as a molecular cross-linking agent binding black C with the mineral matrix or vice versa where inorganic oxides, hydroxides and polycations could act as a bridge to bind black C with non-black C organic matter. The binding and sequestration of black C in the investigated micro- and nano-C repository environments seem to be the combined action of physical entrapment in seemingly terminal biotic exclusion zone through the action of metal oxides and organic matter induced microaggregation and through molecular-level association ranging from ligand exchange, polyvalent cation bridging to weak hydrophobic interactions including van der Waals and H-bonding.
AB - Black C is an essential component of the terrestrial C pool and its formation is often credited as a CO2 sink by transferring the fast-cycling C from the atmosphere-biosphere system into slower cycling C in the geosphere. This study is the first multi-element K- (C, N, Ca, Fe, Al and Si) soft-X-ray STXM-NEXAFS investigation conducted at a submicron-scale spatial resolution specifically targeting black C and its interaction with the mineral and non-black C organic matter in the organomineral assemblage. The STXM-NEXAFS micrographs and spectra demonstrated that pyrogenic C was dominated by quinoide, aromatic, phenol, ketone, alcohol, carboxylic and hydroxylated- and ether-linked C species. There was also evidence for the presence of pyridinic, pyridonic, pyrrolic, amine and nitril N functionalities. The non-black C organic matter contained amino acids, amino sugars, nucleic acids and polysaccharides known to exhibit negatively charged carboxylic, phenolic, enolic, thiolate and phosphate functionalities highly reactive towards metal ions and black C. The metal-rich mineral matrix was composed of phyllosilicate clay minerals, Fe and Al hydroxypolycations, oxides, hydroxides and oxyhydroxide that can attract and bind organic biopolymers. STXM-NEXAFS provided evidence for interactive association between pyrogenic C, non-black C organic matter and the mineral oxide and oxyhydroxide communities in the organomineral interface. These intimate associations occurred through a "two-way" direct linkage between black C and the mineral or non-black C organic matter or via a "three-way" indirect association where non-black C organic matter could serve as a molecular cross-linking agent binding black C with the mineral matrix or vice versa where inorganic oxides, hydroxides and polycations could act as a bridge to bind black C with non-black C organic matter. The binding and sequestration of black C in the investigated micro- and nano-C repository environments seem to be the combined action of physical entrapment in seemingly terminal biotic exclusion zone through the action of metal oxides and organic matter induced microaggregation and through molecular-level association ranging from ligand exchange, polyvalent cation bridging to weak hydrophobic interactions including van der Waals and H-bonding.
KW - Biotic exclusion zone
KW - C sequestration
KW - Global C cycling
KW - Organomineral interactions
KW - Soft X-ray spectromicroscopy
KW - Spatial inaccessibility
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U2 - 10.1016/j.scitotenv.2012.08.071
DO - 10.1016/j.scitotenv.2012.08.071
M3 - Article
C2 - 23022722
AN - SCOPUS:84866705419
VL - 438
SP - 372
EP - 388
JO - Science of the Total Environment
JF - Science of the Total Environment
SN - 0048-9697
ER -