scholarly journals Transformations in occluded light fraction organic matter in a clayey oxisol: evidence from 13C-CPMAS-NMR and delta13C Signature

2004 ◽  
Vol 28 (5) ◽  
pp. 811-818 ◽  
Author(s):  
R. Roscoe ◽  
P. Buurman ◽  
B. van Lagen ◽  
E. Velthorst
Keyword(s):  
Organic Matter ◽  
Isotopic Ratio ◽  
Magic Angle Spinning ◽  
Light Fraction ◽  
Magic Angle ◽  
13C Cpmas Nmr ◽  
Cerrado Vegetation ◽  
Stable Organic Matter ◽  
Light Fraction Organic Matter ◽  
Angle Spinning

We hypothesised that, during occlusion inside granular aggregates of oxide-rich soils, the light fraction organic matter would undergo a strong process of decomposition, either due to the slow process of aggregate formation and stabilisation or due to digestion in the macro- and meso-fauna guts. This process would favour the accumulation of recalcitrant materials inside aggregates. The aim of this study was to compare the dynamics and the chemical composition of free and occluded light fraction organic matter in a natural cerrado vegetation (woodland savannah) and a nearby pasture (Brachiaria spp.) to elucidate the transformations during occlusion of light fraction in aggregates of a clayey Oxisol. Nuclear Magnetic Resonance of the 13C, with Cross Polarisation and Magic Angle Spinning (13C-CPMAS-NMR), and 13C/12C isotopic ratio were combined to study organic matter composition and changes in carbon dynamics, respectively. The occluded light fraction had a slower turnover than the free light fraction and the heavy fraction. Organic matter in the occluded fraction also showed a higher degree of decomposition. The results confirm that processes of soil organic matter occlusion in the typical "very fine strong granular" structure of the studied oxide-rich soil led to an intense transformation, selectively preserving stable organic matter. The small amount of organic material stored as occluded light faction, as well as its stability, suggests that this is not an important or manageable sink for sequestration of atmospheric CO2.

In Situ13C and23Na Magic Angle Spinning NMR Investigation of Supercritical CO2Incorporation in Smectite–Natural Organic Matter Composites

2014 ◽  
Vol 118 (7) ◽  
pp. 3564-3573 ◽  
Author(s):  
Geoffrey M. Bowers ◽  
David W. Hoyt ◽  
Sarah D. Burton ◽  
Brennan O. Ferguson ◽  
Tamas Varga ◽  
...  
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Angle Spinning

scholarly journals CHARACTERIZATION OF BULK SOIL HUMIN AND ITS ALKALINE-SOLUBLE AND ALKALINE-INSOLUBLE FRACTIONS

2015 ◽  
Vol 39 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Cuilan Li ◽  
Shuqing Gao ◽  
Qiang Gao ◽  
Lichun Wang ◽  
Jinjing Zhang
Keyword(s):  
Ph Value ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
13C Cpmas Nmr ◽  
Traditional Treatment ◽  
Chemical Structures ◽  
Exhaustive Extraction ◽  
Angle Spinning ◽  
Soil Colloids

Humic substances are the major components of soil organic matter. Among the three humic substance components (humic acid, fulvic acid, and humin), humin is the most insoluble in aqueous solution at any pH value and, in turn, the least understood. Humin has poor solubility mainly because it is tightly bonded to inorganic soil colloids. By breaking the linkage between humin and inorganic soil colloids using inorganic or organic solvents, bulk humin can be partially soluble in alkali, enabling a better understanding of the structure and properties of humin. However, the structural relationship between bulk humin and its alkaline-soluble (AS) and alkaline-insoluble (AIS) fractions is still unknown. In this study, we isolated bulk humin from two soils of Northeast China by exhaustive extraction (25 to 28 times) with 0.1 mol L-1 NaOH + 0.1 mol L-1 Na4P2O7, followed by the traditional treatment with 10 % HF-HCl. The isolated bulk humin was then fractionated into AS-humin and AIS-humin by exhaustive extraction (12 to 15 times) with 0.1 mol L-1 NaOH. Elemental analysis and solid-state 13C cross-polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy were used to characterize and compare the chemical structures of bulk humin and its corresponding fractions. The results showed that, regardless of soil types, bulk humin was the most aliphatic and most hydrophobic, AS-humin was the least aliphatic, and AIS-humin was the least alkylated among the three humic components. The results showed that bulk humin and its corresponding AS-humin and AIS-humin fractions are structurally differed from one another, implying that the functions of these humic components in the soil environment differed.

scholarly journals Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula

2003 ◽  
Vol 68 (8-9) ◽  
pp. 599-606 ◽  
Author(s):  
Andreas Georgakopoulos
Keyword(s):  
Bituminous Coal ◽  
Balkan Peninsula ◽  
Magic Angle Spinning ◽  
Paramagnetic Species ◽  
Magic Angle ◽  
Northern Greece ◽  
13C Cpmas Nmr ◽  
Nmr Spectrum ◽  
Serbia And Montenegro ◽  
Angle Spinning

The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal) from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative due to a number of interferences, such as spinning side bands (SSB) in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin Northern Greece, is relatively unaltered and largely unlettered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonance's for methoxyl phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.

Cross-polarization 13C-NMR spectroscopy with ‘magic angle’ spinning characterizes organic matter in whole soils

Nature ◽  
1981 ◽  
Vol 294 (5842) ◽  
pp. 648-650 ◽  
Author(s):  
Michael A. Wilson ◽  
Ronald J. Pugmire ◽  
Kurt W. Zilm ◽  
Kuan M. Goh ◽  
Sammy Heng ◽  
...  
Keyword(s):  
Organic Matter ◽  
Nmr Spectroscopy ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
Angle Spinning

Pulse Shaped Dynamic Nuclear Polarization Under Magic Angle Spinning

2019 ◽  
Author(s):  
ASIF EQUBAL ◽  
Kan Tagami ◽  
Songi Han
Keyword(s):  
Electron Spin ◽  
Lattice Relaxation ◽  
Magic Angle Spinning ◽  
Spin Lattice Relaxation ◽  
Magic Angle ◽  
Total Electron ◽  
Spin Lattice ◽  
Maximum Benefit ◽  
Selective Saturation ◽  
Angle Spinning

In this paper, we report on an entirely novel way of improving the MAS-DNP efficiency by shaped μw pulse train irradiation for fast and broad-banded (FAB) saturation of the electron spin resonance. FAB-DNP achieved with Arbitrary Wave Generated shaped μw pulse trains facilitates effective and selective saturation of a defined fraction of the total electron spins, and provides superior control over the DNP efficiency under MAS. Experimental and quantum-mechanics based numerically simulated results together demonstrate that FAB-DNP significantly outperforms CW-DNP when the EPR-line of PAs is broadened by conformational distribution and exchange coupling. We demonstrate that the maximum benefit of FAB DNP is achieved when the electron spin-lattice relaxation is fast relative to the MAS frequency, i.e. at higher temperatures and/or when employing metals as PAs. Calculations predict that under short T<sub>1e </sub>conditions AWG-DNP can achieve as much as ~4-fold greater enhancement compared to CW-DNP.

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