Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Smernik, Ronald J.; Baldock, J. A.; Oades, JM; Whittaker, Andrew K.

doi:10.1006/snmr.2002.0064

Cited by 72 publications

(72 citation statements)

References 68 publications

(98 reference statements)

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“…3b). They differed from the PyC spectra associated with fire severity classes 0 and 1 by an increase in the contribution of the alkyl carbons (peaks at '30 ppm) and the emergence of two peaks characteristic of aromatic carbons: one at 130 ppm assigned to polyaromatic hydrocarbons (Baldock and Smernik 2002), and one at 150 ppm ascribable to O-substituted aromatic carbons (furans). In the spectra of PyC associated with class 4-fire severity, the relative contribution of the two peaks in the aromatic region, as well as the peak in the alkyl region, continued to increase (Fig.…”

Section: Pyc Molecular Compositionmentioning

confidence: 62%

“…We divided the 13 C NMR spectra into the following four carbon regions: carbonyl (215-165 ppm); aromatic and phenolic (165-110 ppm); O-alkyl and di-O-alkyl (110-45 ppm); alkyl (45-0 ppm). We corrected for the spinning side-bands using the regions with large (Smernik et al 2002). To verify that spectra acquired with CP were representative, we used the more quantitative DP technique (Preston and Schmidt 2006) on a subset of samples.…”

Section: Characterization Of Pyc Chemical Propertiesmentioning

confidence: 99%

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Early‐season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance

Soucémarianadin

Quideau

Wasylishen

et al. 2015

Ecology

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Early-season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance.Ecology, 96 (6) Abstract. Pyrogenic carbon (PyC), a major by-product of wildfires in boreal forests, plays several critical roles in soil biogeochemical processes. However, PyC properties, including its potential recalcitrance, may vary depending on its formation conditions. Our study aimed to characterize the chemical and physical properties of PyC formed under variable fire severity in Eastern Canada boreal forests; these latter represent an important fraction of fire-affected circumboreal ecosystems. A total of 267 PyC samples, produced by early-season wildfires in 2005-2007, were collected 5 years after fire from the forest floors of 14 black spruce sites distributed across Quebec, to cover the range of fire severity encountered in these forests. Early-season fires occur frequently in Eastern Canada, and are predicted to increase in regional and global scenarios of future fire regimes associated with climate change. Selected PyC samples were analyzed using elemental analysis, solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy, and surface area analysis. The NMR spectra of the PyC collected on low-fire-severity sites were dominated by peaks indicative of cellulose, while those for PyC from higher-severity sites were dominated by a broad peak assigned to aromatic carbons. Atomic H/C and O/C ratios decreased with increasing fire severity. By comparing field samples to samples produced in the laboratory under controlled formation conditions, we were able to infer that the temperature of formation in the field was low (758-2508C). In addition, for all PyC samples, the aromatic carbon : total carbon ratio was small, suggesting that PyC produced by early-season fires in these boreal forests may be susceptible to relatively rapid degradation. Taken together, our data suggest that boreal PyC may not be as recalcitrant as previously assumed, and that its influence on soil biogeochemical processes may be short lived.

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Section: Pyc Molecular Compositionmentioning

confidence: 62%

Section: Characterization Of Pyc Chemical Propertiesmentioning

confidence: 99%

Early‐season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance

Soucémarianadin

Quideau

Wasylishen

et al. 2015

Ecology

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“…By comparing the spectra of the wood-lignin before (11) and after pT (9), it can be seen that the heat treatment resulted in an increased presence of peaks in the aliphatic region (30 to 40 ppm). This emergence of aliphatic peaks (9) compared to (11) was likely due to a change in NMR relaxation parameters for this lignin component, indicative of greater molecular rigidity due to an intimate connection between the modified lignin added and wood fiber (Smernik and Oades 2000;Smernik et al 2002). In contrast, sample 11 (added modified lignin powder) exhibited a lower NMR response of the aliphatic peaks and may be due to this sample being in untreated form, being a simple mixture, with the added lignin component remaining physically separated from the wood fibre component.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

Chemical Characterization of Wood-Leather Panels by Means of 13C NMR Spectroscopy

et al. 2013

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a Intelligent resource usage is one of the most challenging tasks for the wood-based panels industry. With respect to this issue, leather shavings, derived during leather preparation, are a promising new raw material, as they offer not only high availability, but also potentially enhance material properties such as panel fire retardancy. In order to improve the performance of these emerging panel binder materials, an understanding of chemical interactions between the different constituents is crucial. This paper investigates the chemical changes that occur during hot-pressing of wood and leather in combination with lignin by means of solid state 13 C NMR spectroscopy. These constituents, their binary mixtures, and the influences of panel pressing temperature and pressure commonly used in panel production were investigated. The study showed characteristic chemistry and features of these constituents, quantifying the impacts of both heat and pressure on their interactions. Primarily, analysis revealed that lignin readily connects with both the wood and leather components. Lignin induces chemical change within the protein structure of leather, resembling tanning reactions, or protein complexation. By analogy, it was deduced that this interaction also takes place between leather and the lignin-rich wood fibre surface. This effect may be beneficial in industrial-scale production through improving resin binding properties during panel consolidation.

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“…[9][10][11][12] Moreover, a number of CPMAS 13 C NMR experiments were also performed to assess molecular dynamics in the solid state with the aim of gaining knowledge of the environmental behavior of NOM. 7,[12][13][14][15][16] The model generally used to describe the CP phenomenon and to obtain both quantitative information and information on the dynamics of NOM is a thermodynamic model based on the idea that nuclear spins are in thermal equilibrium. The perturbation of the thermal equilibrium produces the 13 C NMR magnetization which evolves first under the effect of the dipolar coupling between carbons and protons, then under the influence of the relaxation of the protons.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Cross Polarization in Solid State Nuclear Magnetic Resonance Experiments of Amorphous and Heterogeneous Natural Organic Substances

Conte

Berns

2008

ANAL. SCI.

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Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Cited by 72 publications

References 68 publications

Early‐season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance

Early‐season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance

Chemical Characterization of Wood-Leather Panels by Means of 13C NMR Spectroscopy

Dynamics of Cross Polarization in Solid State Nuclear Magnetic Resonance Experiments of Amorphous and Heterogeneous Natural Organic Substances

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