Determination of the aromaticity and the degree of aromatic condensation of a thermosequence of wood charcoal using NMR

McBeath, Anna V.; Smernik, Ronald J.; Schneider, Marcel; Schmidt, Michael W. I.; Plant, Emma Louise

doi:10.1016/j.orggeochem.2011.08.008

Cited by 190 publications

(176 citation statements)

References 44 publications

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“…Therefore, the BKF biochar shifts to a structure very similar to that of the BC biochar. In contrast to the kaolinite, the bentonite clay does not undergo a structural collapse at 550 °C as suggested by 29 Si and 27 Al NMR, and continues to exert its influence through the high interfacial contact with the biochar.…”

Section: Infiltrationmentioning

confidence: 93%

“…The typical measurement time for each 13 C DPMAS experiment was 11 hours. Details for the mineral analysis 27 Al and 29 Si solid state NMR are provided in the Supplementary material. NMR Cryoporometry.…”

Section: Solid State Nmrmentioning

confidence: 99%

“…This implies that the BBF and BKF series of biochar have a greater degree of aromatic condensation that is correlated to greater stability of the biochar within the soil. [27][28] Additionally, the BBF and BKF series also have a higher concentration of phenolic species, particularly at 450 °C and 550 °C The overall effect of the pyrolysis temperature and the presence of clay on the biochar is better visualized by plotting the O:C vs. H:C atomic ratios along the x and y axes respectively, for each pyrolysis temperature, as shown in Figure 3. The ratios are extracted directly from the data in Figure S1, which gives the ratios of the different C-H, C-O and quaternary C species in the biochar.…”

Section: Infiltrationmentioning

confidence: 99%

“…Evidence for this comes from examination of the thermally treated clay-iron mixtures by solid state 29 Si and 27 Al NMR of neat mixtures of clay and iron sulfate (supplementary information Figure S3). While the Fe/bentonite is stable to temperatures above 550 °C, the Fe/kaolinite undergoes a degradation-transformation into metakaolin at 550 °C.…”

Section: Infiltrationmentioning

confidence: 99%

“…The degree of carbon condensation is directly relevant to the stability of the biochar and its environmental implications relating to carbon sequestration. [27][28] The concentrations of different functional groups, such as carboxylic acids, and the porosity of the biochar are pertinent to the agricultural applications of biochar, while the ability to control the degradation pathway will be crucial for efficient production of the desired engineered biochar structure. Pyrolysis was carried out by heating the samples in an air starved environment at 3 °C/minute until the final pyrolysis temperature was attained.…”

Section: Introductionmentioning

confidence: 99%

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Mineral–Biochar Composites: Molecular Structure and Porosity

Rawal¹,

Joseph²,

Hook³

et al. 2016

Environ. Sci. Technol.

161

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Dramatic changes in molecular structure, degradation pathway, and porosity of biochar are observed at pyrolysis temperatures ranging from 250 to 550 °C when bamboo biomass is pretreated by iron-sulfate-clay slurries (iron-clay biochar), as compared to untreated bamboo biochar. Electron microscopy analysis of the biochar reveals the infusion of mineral species into the pores of the biochar and the formation of mineral nanostructures. Quantitative 13C nuclear magnetic resonance (NMR) spectroscopy shows that the presence of the iron clay prevents degradation of the cellulosic fraction at pyrolysis temperatures of 250 °C, whereas at higher temperatures (350-550 °C), the clay promotes biomass degradation, resulting in an increase in both the concentrations of condensed aromatic, acidic, and phenolic carbon species. The porosity of the biochar, as measured by NMR cryoporosimetry, is altered by the iron-clay pretreatment. In the presence of the clay, at lower pyrolysis temperatures, the biochar develops a higher pore volume, while at higher temperature, the presence of clay causes a reduction in the biochar pore volume. The most dramatic reduction in pore volume is observed in the kaolinite-infiltrated biochar at 550 °C, which is attributed to the blocking of the mesopores (2-50 nm pore) by the nonporous metakaolinite formed from kaolinite. Disciplines Engineering | Physical Sciences and Mathematics

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Section: Infiltrationmentioning

confidence: 93%

Section: Solid State Nmrmentioning

confidence: 99%

Section: Infiltrationmentioning

confidence: 99%

Section: Infiltrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Mineral–Biochar Composites: Molecular Structure and Porosity

Rawal¹,

Joseph²,

Hook³

et al. 2016

Environ. Sci. Technol.

161

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Decoupled sedimentary records of combustion: Causes and implications

Hanke

Eglinton

Braun

et al. 2016

Geophysical Research Letters

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Pyrogenic carbon (PyC) is a collective term for carbon‐rich residues comprised of a continuum of products arising from biomass burning and fossil‐fuel combustion. PyC is ubiquitous in the environment where it can be transported by wind and water before being deposited in aquatic sediments. We compare results from four different methods used to trace PyC that were applied to a high‐temporal resolution sedimentary record in order to constrain changes in PyC concentrations and fluxes over the past ~250 years. We find markedly discordant records for different PyC tracers, particularly during the preindustrial age, implying different origins and modes of supply of sedimentary PyC. In addition to providing new insights into the composition of sedimentary combustion products, this study reveals that elucidation of past combustion processes and development of accurate budgets of PyC production and deposition on local to regional scales requires careful consideration of both source characteristics and transport processes.

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Fire severity alters the distribution of pyrogenic carbon stocks across ecosystem pools in a Californian mixed‐conifer forest

et al. 2017

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Pyrogenic carbon (PyC) is hypothesized to play an important role in the carbon (C) cycle due to its resistance to decomposition; however, much uncertainty still exists regarding the stocks of PyC that persist on‐site after the initial erosion in postfire forests. Therefore, understanding how fire characteristics influence PyC stocks is vital, particularly in the context of California forests for which an increase of high‐severity fires is predicted over the next decades. We measured forest C and persistent PyC stocks in areas burned by low‐to‐moderate and high‐severity fire, as well as in adjacent unburned areas in a California mixed‐conifer forest, 2 to 3 years after wildfire. We measured C and PyC stocks in the following compartments: standing trees, downed wood, forest floor, and mineral soil (0–5 cm), and we identified PyC using the weak nitric acid digestion method. We found that the total stock of PyC did not differ among fire severity classes (overall mean 248 ± 30 g C m−2); however, fire severity influenced the distribution of PyC in the individual compartments. Areas burned by high‐severity fire had 2.5 times more PyC stocked in the coarse woody debris (p < 0.05), 3.3 times more PyC stocked in standing trees (p < 0.05), and a lower PyC stock in the forest floor (−22%, p < 0.05) compared to low‐to‐moderate fire severity areas. These results have important implications for the permanence time of PyC, which is putatively higher in standing trees and coarse woody debris compared to the forest floor, where it is susceptible to rapid losses through erosion.

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Determination of the aromaticity and the degree of aromatic condensation of a thermosequence of wood charcoal using NMR

Cited by 190 publications

References 44 publications

Mineral–Biochar Composites: Molecular Structure and Porosity

Mineral–Biochar Composites: Molecular Structure and Porosity

Decoupled sedimentary records of combustion: Causes and implications

Fire severity alters the distribution of pyrogenic carbon stocks across ecosystem pools in a Californian mixed‐conifer forest

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