Multidecadal persistence of organic matter in soils: multiscale investigations down to the submicron scale

Abstract. Minerals, particularly clay-sized minerals, protect soil organic matter (SOM) from decomposition by microorganisms. Here we report the characterization of SOM and the associated minerals over decades of biodegradation, in a French long-term bare fallow (LTBF) experiment started in 1928. The amounts of carbon (C) and nitrogen (N) in the study area declined over time for six fractions (sand, coarse silt, fine silt, coarse clays, intermediate clays, and fine clays). The C:N ratios of SOM associated with silt fractions remained constant, whereas the ratios significantly decreased in clays, reaching very low values in intermediate and fine clays (C:N < 5) after 8 decades of LTBF conditions. X-ray absorption spectroscopy revealed the following: (i) bulk-scale SOM chemical speciation remained almost constant; (ii) submicron particulate OM was present in coarse clays, even after 79 years of LTBF conditions; and (iii) illite particles became progressively SOM-free with time, whereas mixed-layer illite/smectite and smectites were always associated with OM throughout the bare fallow treatment. In summary, these results suggest that clay-sized minerals preferentially protect N-rich SOM and that smectites and mixed-layer illite/smectite seem to protect associated OM more effectively than pure illites.

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Multidecadal persistence of organic matter in soils: investigations at the submicrometer scale

10.5194/bg-2018-343 ◽

2018 ◽

Cited By ~ 1

Author(s):

Suzanne Lutfalla ◽

Pierre Barré ◽

Sylvain Bernard ◽

Corentin Le Guillou ◽

Julien Alléon ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Coarse Silt ◽

Fine Silt ◽

Mineral Matrix ◽

Bare Fallow

Abstract. The mineral matrix, particularly clay-sized minerals, protects soil organic matter (SOM) from decomposition by microorganisms. Here we report the characterization of SOM and associated minerals over decades of biodegradation, in a French long-term bare fallow (LTBF) experiment started in 1928. The amounts of carbon (C) and nitrogen (N) declined with time for six fractions (sand, coarse silt, fine silt, coarse clays, intermediate clays and fine clays). The C : N ratios of SOM associated to silt fractions remained constant whereas they significantly decreased in clays, reaching very low values in intermediate and fine clays (C : N

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Electrochemical and physical characterization of Ni-Cu-Fe alloy for chlor-alkali hydrogen cathodes

Eclética Química ◽

10.1590/s0100-46702003000200003 ◽

2003 ◽

Vol 28 (2) ◽

pp. 21-28 ◽

Cited By ~ 13

Author(s):

M. J. Giz ◽

M. C. Marengo ◽

E. A. Ticianelli ◽

E. R. Gonzalez

Keyword(s):

Low Ph ◽

Physical Characterization ◽

Energy Dispersive Analysis ◽

Positive Aspect ◽

X Ray ◽

Term Operation ◽

Different Temperatures ◽

X Ray Absorption

This work describes the development of an alternative acetate bath for the electrochemical codeposition of Ni-Cu-Fe electrodes at low pH that is stable for several weeks and produces electrodes with good performance for chlor-alkali electrolysis. Physical characterization of the electrode surface was made using X ray absorption spectroscopy (XAS), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). The evaluation of the material as electrocatalyst for the hydrogen evolution reaction (her) was carried out in brine solution (160 g L-1 NaCl + 150 g L-1 NaOH) at different temperatures through steady-state polarization curves. The Ni-Cu-Fe electrodes obtained with this bath have shown low overpotentials for the her, around 0.150 V at 353 K, and good stability under continuous long-term operation for 260 hours. One positive aspect of this cathode is that the polarization behavior of the material shows only one Tafel slope over the temperature range of 298 - 353 K.

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Raman studies of technetium in borosilicate waste glass

Radiochimica Acta ◽

10.1524/ract.2007.95.5.275 ◽

2007 ◽

Vol 95 (5) ◽

Cited By ~ 12

Author(s):

David A. McKeown ◽

Andrew C. Buechele ◽

Wayne W. Lukens ◽

D. K. Shuh ◽

Ian L. Pegg

Keyword(s):

Raman Spectroscopy ◽

Waste Glass ◽

Borosilicate Glasses ◽

Coordination Environment ◽

X Ray ◽

Waste Vitrification ◽

X Ray Absorption ◽

Raman Spectral

The characterization of technetium (Tc) environments in borosilicate glasses is important with regard to the long-term isolation of Tc in nuclear wastes from the environment by waste vitrification. In this study, Raman spectroscopy was used to detect Tc in various borosilicate waste glass formulations in which Tc valence and average coordination environment were previously characterized by X-ray absorption spectroscopy. Raman spectral comparisons between chemically equivalent Tc-containing and Tc-free borosilicate glass pairs indicate Tc-dependent features near 320 and 910 cm

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EXELFS Studies of Carbon Fibers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133953 ◽

1990 ◽

Vol 48 (2) ◽

pp. 72-73

Author(s):

V. Serin ◽

K. Hssein ◽

G. Zanchi ◽

J. Sévely

Keyword(s):

Carbon Fibers ◽

Energy Analysis ◽

Electron Excitation ◽

Complex Structures ◽

High Modulus ◽

Promising Technique ◽

X Ray ◽

Fine Structures ◽

X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

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Database of ab initio L-edge X-ray absorption near edge structure

Scientific Data ◽

10.1038/s41597-021-00936-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Yiming Chen ◽

Chi Chen ◽

Chen Zheng ◽

Shyam Dwaraknath ◽

Matthew K. Horton ◽

...

Keyword(s):

High Throughput ◽

Scattering Theory ◽

Research Community ◽

Metal Compounds ◽

Edge Structure ◽

X Ray ◽

Initial Release ◽

Computational Workflow ◽

X Ray Absorption

AbstractThe L-edge X-ray Absorption Near Edge Structure (XANES) is widely used in the characterization of transition metal compounds. Here, we report the development of a database of computed L-edge XANES using the multiple scattering theory-based FEFF9 code. The initial release of the database contains more than 140,000 L-edge spectra for more than 22,000 structures generated using a high-throughput computational workflow. The data is disseminated through the Materials Project and addresses a critical need for L-edge XANES spectra among the research community.

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Characterization of Silver Binding in Cryptomelane by X-ray Absorption Spectroscopy

MRS Proceedings ◽

10.1557/proc-524-353 ◽

1998 ◽

Vol 524 ◽

Cited By ~ 4

Author(s):

R. Ravikumar ◽

D. W. Fuerstenau ◽

G. A. Waychunas

Keyword(s):

Manganese Oxide ◽

Silver Ions ◽

Oxide Phase ◽

Synthetic Sample ◽

Temperature Spectrum ◽

X Ray ◽

Room Temperature Sample ◽

X Ray Absorption ◽

Temperature Sample

ABSTRACTUsing silver K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, two different samples of silver-containing manganese oxide were analyzed in the fluorescence mode. For the first sample, silver ions from solution were sorbed onto one synthetic manganese oxide phase, namely cryptomelane (KxMn8O16, where l<x<2). The second sample was a silvermanganese oxide from Colorado. From the EXAFS analysis, silver was found to occupy two different sites in the synthetic sample. The natural samples from Colorado also exhibited a very similar coordination distances as the synthetic samples. In the low temperature spectrum of the synthetic sample at 10 K, the Ag-O peak was found to be missing and the amplitude of the Ag- Ag peak was approximately three times larger than the corresponding room temperature sample.

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