scholarly journals Molecular characteristics of permanganate- and dichromate-oxidation-resistant soil organic matter from a black-C-rich colluvial soil

Soil Research ◽  
2014 ◽  
Vol 52 (2) ◽  
pp. 164 ◽  
Author(s):  
Manuel Suárez-Abelenda ◽  
Joeri Kaal ◽  
Marta Camps-Arbestain ◽  
Heike Knicker ◽  
Felipe Macías
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
13C Nmr ◽  
Magic Angle Spinning ◽  
Molecular Characteristics ◽  
Magic Angle ◽  
Residual Soil ◽  
Pyrolysis Gas ◽  
North West ◽  
Colluvial Soil

Samples from a colluvial soil rich in pyrogenic material (black C, BC) in north-west Spain were subjected to K2Cr2O7 and KMnO4 oxidation and the residual soil organic matter (SOM) was NaOH-extracted and analysed using analytical pyrolysis–gas chromatography–mass spectroscopy (Py-GC/MS) and solid-state 13C cross-polarisation magic angle spinning–nuclear magnetic resonance (13C CP MAS-NMR) in order to study the susceptibility of different SOM fractions (fresh, degraded/microbial, BC and aliphatic) towards these oxidising agents. Untreated samples that were NaOH-extracted were also analysed. The Py-GC/MS and 13C NMR indicated that KMnO4 promotes the oxidation of carbohydrate products, mostly from degraded/microbial SOM and lignocellulose, causing a relative enrichment of aliphatic and aromatic structures. Residual SOM after K2Cr2O7 oxidation contained BC, N-containing BC and aliphatic structures. This was corroborated by a relatively intense resonance of aromatic C and some signal of alkyl C in 13C NMR spectra. These results confirm that dichromate oxidation residues contain a non-pyrogenic fraction mainly consisting of aliphatic structures.

scholarly journals Effects of long-term mowing on the fractions and chemical composition of soil organic matter in a semiarid grassland

2017 ◽  
Vol 14 (10) ◽  
pp. 2685-2696 ◽  
Author(s):  
Jiangye Li ◽  
Qichun Zhang ◽  
Yong Li ◽  
Yimeng Liu ◽  
Jianming Xu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Functional Groups ◽  
13C Nmr ◽  
Magic Angle ◽  
Grassland Ecosystem ◽  
Semiarid Grassland ◽  
The Stability

Abstract. The grassland ecosystem is a significantly important terrestrial carbon pool. Intensive mowing is common to meet the need of increased livestock. However, little information on the quality and quantity of soil organic matter (SOM) under different mowing managements has been documented. In this work, in order to evaluate the impacts of different mowing managements on the quality and quantity of SOM, the fractions and chemical composition of SOM under different mowing managements were determined using traditional fractionation methods and spectroscopy technologies, including advanced nuclear magnetic resonance (NMR) (e.g. cross-polarization magic angle spinning 13C-NMR, CPMAS 13C-NMR) and Fourier-transform infrared (FTIR) based on a 13-year field mowing trial with four treatments: unmown (M0), mowing once every second year (M1/2), mowing once a year (M1) and mowing twice a year (M2). The results showed that compared with M0, M1/2 and M1 significantly enhanced the SOM accumulation and increased the stability of SOM by enhancing humification, while M2 limited SOM accumulation and microbial biomass. Substituted alkyl carbon (C) was the major organic C type in the grassland ecosystem, and it made up over 40 % of the total C. M1/2 and M1 significantly increased stable C functional groups (alkyl C and aromatic C) by degrading labile C functional groups (O-alkyl and carbonyl C) and forming recalcitrant humus, while M2 had opposite effects. The consistent increase in the values of NMR indices reflecting the degradation degree, hydrophobicity and aromaticity of SOM in M1 reflected the fact that M1 had the largest contribution to increasing the stability of SOM, while these values in M2 were similar to those in M0. Significant correlations between different SOM fractions and nitrogen (N) mineralization, and between the contents of different C functional groups and net soil organic nitrogen mineralization or microbial biomass C, indicated that the shifts in SOM fractions and chemical composition were closely related to soil microbial biomass and activity. Therefore, in view of the quality and quantity of SOM and the sustainable development of grassland ecosystems, M1 was the optimal mowing management, while M2 should be avoided in the semiarid grassland.

Incorporation of uniformly labeled 13C glucose carbon into the organic fraction of a soil - carbon balance and CP MAS 13C NMR Measurements

Soil Research ◽  
1989 ◽  
Vol 27 (4) ◽  
pp. 725 ◽  
Author(s):  
JA Baldock ◽  
JM Oades ◽  
AM Vassallo ◽  
MA Wilson
Keyword(s):  
Organic Matter ◽  
Solid State ◽  
Soil Organic Matter ◽  
13C Nmr ◽  
Carbon Balance ◽  
Chemical Structure ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
13C Nuclear Magnetic Resonance ◽  
Cp Mas 13C Nmr

The incorporation of uniformly labelled 13C-giucose into soil organic matter was followed using mass spectrometry to make carbon balance measurements, and using solid state CP/MAS 13C NMR (cross polarization/magic angle spinning 13C nuclear magnetic resonance) spectroscopy to determine changes in the chemical structure of the added 13C with time. A fine sandy loam soil was incubated in the presence and absence of the labelled 13C-glucose for up to 34 days at 22�C and a soil water matric potential of -33 kPa. Carbon balance measurements indicated that no priming effect of glucose addition on decomposition of the native organic carbon occurred, and that 65% of the glucose 13C was mineralized during the incubation period. The ability of solid-state CP/MAS 13C NMR to quantitatively detect all of the substrate 13C present in the samples was assessed by comparing the residual substrate 13C contents of the samples analysed with the corresponding CP/MAS 13C NMR signal intensities. Incorporation of the glucose 13C into the soil organic matter resulted in the synthesis of alkyl (26%), O-alkyl (66%), and carboxyl (8%) carbon, but little if any aromatic carbon. The influence of decomposition processes on the chemical characteristics of the soil organic matter is discussed, and the chemical structure of the materials synthesized by the microbial biomass is compared with that of the native soil organic matter.

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

Fire effects on soil organic matter content, composition, and nutrients in boreal interior Alaska

2005 ◽  
Vol 35 (9) ◽  
pp. 2178-2187 ◽  
Author(s):  
J C Neff ◽  
J W Harden ◽  
G Gleixner
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Matter Content ◽  
Fire Effects ◽  
Matter Content ◽  
Soil Horizon ◽  
Surface Soils ◽  
Pyrolysis Gas ◽  
Gas Chromatography Mass Spectroscopy ◽  
Potassium Magnesium

Boreal ecosystems contain a substantial fraction of the earth's soil carbon stores and are prone to frequent and severe wildfires. In this study, we examine changes in element and organic matter stocks due to a 1999 wildfire in Alaska. One year after the wildfire, burned soils contained between 1071 and 1420 g/m2 less carbon than unburned soils. Burned soils had lower nitrogen than unburned soils, higher calcium, and nearly unchanged potassium, magnesium, and phosphorus stocks. Burned surface soils tended to have higher concentrations of noncombustible elements such as calcium, potassium, magnesium, and phosphorus compared with unburned soils. Combustion losses of carbon were mostly limited to surface dead moss and fibric horizons, with no change in the underlying mineral horizons. Burning caused significant changes in soil organic matter structure, with a 12% higher ratio of carbon to combustible organic matter in surface burned horizons compared with unburned horizons. Pyrolysis gas chromatography – mass spectroscopy also shows preferential volatilization of polysaccharide-derived organic matter and enrichment of lignin- and lipid-derived compounds in surface soils. The chemistry of deeper soil layers in burned and unburned sites was similar, suggesting that immediate fire impacts were restricted to the surface soil horizon.

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