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.

scholarly journals Phenoloxidase activity and organic carbon dynamics in historic Anthrosols in Scotland, UK

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0259205
Author(s):  
Benneth O. I. Esiana ◽  
Christopher J. Coates ◽  
W. Paul Adderley ◽  
Anne E. Berns ◽  
Roland Bol
Keyword(s):  
Organic Matter ◽  
Solid State ◽  
Phenolic Compounds ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Phenoloxidase Activity ◽  
The Impact

Phenolic compounds are chemical precursor building blocks of soil organic matter. Their occurrence can be inhibitory to certain enzymes present in soil, thereby influencing the rate of decomposition of soil organic matter. Microbe-derived phenoloxidases (laccases) are extracellular enzymes capable of degrading recalcitrant polyphenolic compounds. In this study, our aim was to investigate the relationships between phenoloxidase enzyme activity, organic carbon content and microbial abundance in the context of long-term anthropogenically amended soils. To achieve this, we used a series of complementary biochemical analytical methods including gas chromatography, enzyme assays and solid-state Carbon-13 Cross Polarisation Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy (13C CPMAS NMR). Using several anthrosols found in St Andrews (Scotland, UK) that had been subjected to intense anthropogenic modification since the medieval period (11th century AD) to present-day, we were able to scope the impact of past waste disposal on soils. The long-term anthropogenic impact led to organic matter-rich soils. Overall, phenoloxidase activity increased by up to 2-fold with soil depth (up to 100 cm) and was inversely correlated with microbial biomass. Solid-state 13C NMR characterisation of carbon species revealed that the observed decline in soil organic matter with depth corresponded to decreases in the labile organic carbon fractions as evidenced by changes in the O/N-alkyl C region of the spectra. The increase in phenoloxidase activity with depth would appear to be a compensatory mechanism for the reduced quantities of organic carbon and lower overall nutrient environment in subsoils. By enzymatically targeting phenolic compounds, microbes can better utilise recalcitrant carbon when other labile soil carbon sources become limited, thereby maintaining metabolic processes.

Virtual fractionation of charcoal from soil organic matter using solid state 13C NMR spectral editing

Soil Research ◽  
2000 ◽  
Vol 38 (3) ◽  
pp. 665 ◽  
Author(s):  
R. J. Smernik ◽  
J. O. Skjemstad ◽  
J. M. Oades
Keyword(s):  
Organic Matter ◽  
Solid State ◽  
Soil Organic Matter ◽  
13C Nmr ◽  
High Energy ◽  
Proton Spin ◽  
Inversion Recovery ◽  
Spectral Editing ◽  
Photo Oxidation ◽  
Solid State 13C Nmr

The solid state 13C NMR spectral editing technique proton spin relaxation editing (PSRE), which generates subspectra of components that have different proton relaxation rates and are spatially separated by at least 30–100 nm, was applied to hydrofluoric acid treated <53 m soil fractions from 8 Australian surface soils. Most of the aromatic signal was partitioned into the rapidly relaxing subspectrum, especially for the soils known to have high charcoal contents. However, the presence of other rapidly relaxing soil organic matter (SOM) components prevented a clean separation of charcoal from non-charcoal components. PSRE analysis was repeated after the samples had been treated with high energy ultraviolet photo-oxidation, which brings about the mineralisation of most SOM other than char. Excellent separation of the charcoal fraction by PSRE was achieved after photo-oxidation for 5 of the samples with the highest charcoal content. The rapidly relaxing subspectra for these samples also suggested that the charcoal present in soil contains significant carbonyl functionality, possibly as a result of in situ weathering. A new PSRE methodology is described, designed to best suit SOM samples. Data from inversion-recovery experiments were fitted to a model consisting of 2 components with different T1H relaxation rate constants, thus providing an objective best fit to the inversion-recovery data and avoiding the subjective judgements required in other PSRE methodologies.

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