skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil: Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy

Abstract

Methodological constraints limit the extent to which existing soil aggregation models explain carbon (C) stabilization in soil. We hypothesize that the physical infrastructure of microaggregates plays a major role in determining the chemistry of the occluded C and intimate associations between particulate C, chemically stabilized C and the soil mineral matrix. We employed synchrotron-based scanning transmission X-ray microscopy (STXM) coupled with near-edge X-ray absorption fine structure (C 1s-NEXAFS) spectroscopy to investigate the nanoscale physical assemblage and C chemistry of 150-{micro}m microaggregates from a Kenyan Oxisol. Ultra-thin sections were obtained after embedding microaggregates in a sulfur block and sectioning on a cryo-microtome at -55 degrees C. Principal component and cluster analyses revealed four spatially distinct features: pore surfaces, mineral matter, organic matter, and their mixtures. The occurrence of these features did not vary between exterior and interior locations; however, the degree of oxidation decreased while the complexity and occurrence of aliphatic C forms increased from exterior to interior regions of the microaggregate. At both locations, compositional mapping rendered a nanoscale distribution of oxidized C clogging pores and coating pore cavities on mineral surface. Hydrophobic organic matter of aromatic and aliphatic nature, representing particulate C forms appeared physically occluded in 2- tomore » 5-{micro}m pore spaces. Our findings demonstrate that organic matter in microaggregates may be found as either oxidized C associated with mineral surfaces or aromatic and aliphatic C in particulate form. Using STXM and C 1s-NEXAFS we are for the first time able to resolve the nanoscale biogeocomplexity of unaltered soil microaggregates.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
913987
Report Number(s):
BNL-78555-2007-JA
Journal ID: ISSN 0361-5995; SSSJD4; TRN: US0801454
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Soil Sci. Soc. Am. J.; Journal Volume: 70; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; FINE STRUCTURE; MICROSCOPY; ORGANIC MATTER; SOILS; SPECTROSCOPY; NSLS; national synchrotron light source

Citation Formats

Kinyangi,J., Solomon, D., Liang, B., Lerotic, M., Wirick, S., and Lehmann, J. Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil: Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy. United States: N. p., 2006. Web. doi:10.2136/sssaj2005.0351.
Kinyangi,J., Solomon, D., Liang, B., Lerotic, M., Wirick, S., & Lehmann, J. Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil: Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy. United States. doi:10.2136/sssaj2005.0351.
Kinyangi,J., Solomon, D., Liang, B., Lerotic, M., Wirick, S., and Lehmann, J. Sun . "Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil: Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy". United States. doi:10.2136/sssaj2005.0351.
@article{osti_913987,
title = {Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil: Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy},
author = {Kinyangi,J. and Solomon, D. and Liang, B. and Lerotic, M. and Wirick, S. and Lehmann, J.},
abstractNote = {Methodological constraints limit the extent to which existing soil aggregation models explain carbon (C) stabilization in soil. We hypothesize that the physical infrastructure of microaggregates plays a major role in determining the chemistry of the occluded C and intimate associations between particulate C, chemically stabilized C and the soil mineral matrix. We employed synchrotron-based scanning transmission X-ray microscopy (STXM) coupled with near-edge X-ray absorption fine structure (C 1s-NEXAFS) spectroscopy to investigate the nanoscale physical assemblage and C chemistry of 150-{micro}m microaggregates from a Kenyan Oxisol. Ultra-thin sections were obtained after embedding microaggregates in a sulfur block and sectioning on a cryo-microtome at -55 degrees C. Principal component and cluster analyses revealed four spatially distinct features: pore surfaces, mineral matter, organic matter, and their mixtures. The occurrence of these features did not vary between exterior and interior locations; however, the degree of oxidation decreased while the complexity and occurrence of aliphatic C forms increased from exterior to interior regions of the microaggregate. At both locations, compositional mapping rendered a nanoscale distribution of oxidized C clogging pores and coating pore cavities on mineral surface. Hydrophobic organic matter of aromatic and aliphatic nature, representing particulate C forms appeared physically occluded in 2- to 5-{micro}m pore spaces. Our findings demonstrate that organic matter in microaggregates may be found as either oxidized C associated with mineral surfaces or aromatic and aliphatic C in particulate form. Using STXM and C 1s-NEXAFS we are for the first time able to resolve the nanoscale biogeocomplexity of unaltered soil microaggregates.},
doi = {10.2136/sssaj2005.0351},
journal = {Soil Sci. Soc. Am. J.},
number = 5,
volume = 70,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}