Ecological Archives E096-140-A3
Laure N. Soucémarianadin, Sylvie A. Quideau, Roderick E. Wasylishen, and Alison D. Munson. 2015. Early-season fires in boreal black spruce forests produce pyrogenic carbon with low intrinsic recalcitrance. Ecology 96:1575–1585. http://dx.doi.org/10.1890/14-1196.1
Appendix C. Comparison of 13C NMR spectra for the field pyrogenic carbon.
Table C1. Results from the 13C NMR direct polarization (DP) and cross polarization (CP) experiments for a subset of pyrogenic carbon (PyC; classes 0, 2, and 5) produced by wildfire.
This includes the relative intensities (% total spectral area) of carbonyl C, aromatic and phenolic C, O-alkyl C, and alkyl C; and the spin counting results (DP experiments only). For the latter, glycine (Fisher Scientific, reagent grade) was used as an external reference material. We determined the carbon observability, Cobs, which corresponds to the fraction of the expected NMR intensity that is actually observed; intensities of the NMR resonances quantitatively reflect the distribution of 13C environments present in the sample if Cobs = 100% (Smernik and Oades 2000).
NMR experiment |
CP |
DP |
CP |
DP |
CP |
DP |
Fire severity class |
0 |
2 |
5 |
|||
Spectral region |
Proportion of total signal intensity (%) |
|||||
Carbonyl |
7.2 |
9.1 |
8.2 |
9.4 |
11.3 |
9.5 |
Aromatic & Phenolic |
17.4 |
24.5 |
22.4 |
27.7 |
47.7 |
56.6 |
O-alkyl C |
61.8 |
55.8 |
45.9 |
37.6 |
21.6 |
14.9 |
Alkyl C |
13.6 |
10.6 |
23.5 |
25.4 |
19.5 |
19.0 |
Spin counting |
Cobs (%) |
|||||
|
|
90.8 |
|
82.4 |
|
65.8 |
There was no significant difference in the distribution of the total signal intensity between the 13C CP and DP NMR experiments. To test for differences, we used a Wilcoxon signed-rank test as data were not distributed normally. Significance was considered at α of 0.05.
Table C2. Peak assignments on the 13C NMR spectra for the six classes of pyrogenic carbon produced by wildfire (Fig. 3).
Spectral region |
Chemical shift (ppm)a |
Carbon function |
Macromolecule |
O-alkyl & di-O-alkyl (110–45 ppm) |
65 |
C6 β-(1→4)-D-glucopyranose + C5 β-(1→4)-D-xylopyranose |
Cellulose / Hemicellulose (xylan) |
74 |
C2, C3, C5 β-(1→4)-D-glucopyranose + C2, C3, C4 β-(1→4)-D-xylopyranose |
Cellulose / Hemicellulose (xylan) |
|
84 |
C4 β-(1→4)-D-glucopyranose |
Cellulose (amorphous) |
|
89 |
C4 β-(1→4)-D-glucopyranose |
Cellulose (crystalline) |
|
105 |
C1 β-(1→4)-D-glucopyranose |
Cellulose |
|
Alkyl (45–0 ppm) |
21 |
Methyl |
Hemicellulose (xylan) |
O-alkyl & di-O-alkyl (110–45 ppm) |
102 |
C1 β-(1→4)-D-xylopyranose |
Hemicellulose (xylan) |
Carbonyl (215–165 ppm) |
173 |
Carboxyl group / Acetate |
Hemicellulose (xylan) |
O-alkyl & di-O-alkyl (110–45 ppm) |
56 |
Methoxyl group |
Lignin |
Aromatic & phenolic (165–110 ppm) |
115 |
Guaiacyl unit (C5) + p-Hydroxyphenyl (C3, C5) |
Lignin |
132 |
C5 and C5' in etherified 5-5' guaiacyl+ p-Hydroxyphenyl (C2, C6) |
Lignin |
|
145 |
Guaiacyl (C3, C4) |
Lignin |
|
158 |
p-Hydroxyphenol (C4) |
Lignin |
|
Alkyl (45–0 ppm) |
25 |
Methyl and methylene |
Char |
Aromatic & phenolic (165–110 ppm) |
130 |
Aromatic non-oxygenated carbons |
Char |
145–150 |
Aromatic C linked to O (e.g., phenols and derivatives) |
Char |
a data from literature: Almendros et al., 1992; Freitas et al., 1999; Wikberg and Maunu, 2004; Inari et al., 2007; Melkior et al., 2012
Literature cited
Almendros, G., A. T. Martinez, A. E. Gonzalez, F. Gonzalez-Vila, R. Fruend, and H. D. Luedemann. 1992. CPMAS carbon-13 NMR study of lignin preparations from wheat strawtransformed by five lignocellulose-degrading fungi. Journal of Agricultural and Food Chemistry 40:1297-1302.
Freitas, J. C. C., T. J. Bonagamba, and F. G. Emmerich. 1999. 13C high-resolution solid-state NMR study of peat carbonization. Energy Fuels 13:53-59.
Inari, G. N., S. Mounguengui, S. Dumarçay, M. Pétrissans, and P. Gérardin. 2007. Evidence of char formation during wood heat treatment by mild pyrolysis. Polymer Degradation and Stability 92:997-1002.
Melkior, T., S. Jacob, G. Gerbaud, S. Hediger, L. Le Pape, L. Bonnefois, and M. Bardet. 2012. NMR analysis of the transformation of wood constituents by torrefaction. Fuel 92:271-280.
Smernik, R. J., J. M. Oades. 2000. The use of spin counting for determining quantitation in solid state 13C NMR spectra of natural organic matter: 2. HF-treated soil fractions. Geoderma 96:159-171.
Wikberg, H., S. L. Maunu. 2004. Characterisation of thermally modified hard- and softwoods by 13C CPMAS NMR. Carbohydrate Polymers 58:461-466.