Rearrangement of carbon and nitrogen forms in peat after progressive thermal oxidation as determined by solid-state 13C and 15N-NMR spectroscopy
Rearrangement of carbon and nitrogen forms in peat after progressive thermal oxidation as determined by solid-state 13C and 15N-NMR spectroscopy
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DOI：
10.1016/s0146-6380(03)00152-9
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发表时间：
2003-01-01
影响因子：
3
通讯作者：
González-Vila, FJ
中科院分区：
文献类型：
--
作者：
Almendros, G;Knicker, H;González-Vila, FJ
利用固体C-13- nmr和N-15-NMR对热氧化泥炭样品进行了研究，以获得自然火灾或规定火灾影响土壤过程中有机质热变化的信息。c -13核磁共振光谱显示，加热（350℃下加热180 s）使原始泥炭的芳香性提高到典型的黑碳材料的值，但这些烧焦的残留物（至少在重量损失约25%之后）仍然含有耐热的烷基碳。原始泥炭的N-15-NMR谱以-258 ppm的信号为主，表明是肽样物质。在加热后的样品中，低场处出现的共振线表明吡咯型和吲哚型化合物的逐渐形成。根据13C-和n -15核磁共振谱的失重、元素组成和相对强度分布计算表明，随着逐渐加热，芳香c型和杂环n型的浓度增加不仅是由于相对富集伴随不稳定结构（主要是o -烷基和酰胺）的选择性热降解引起的，而且与脂肪族物质形成的新合成结构相对应。(C) 2003 Elsevier Ltd.版权所有。
Peat samples subjected to thermal oxidation were studied by solid-state C-13- and N-15-NMR spectroscopy, so as to gain information on the thermal alteration of organic matter during processes such as natural fires or prescribed fires affecting soils. The C-13-NMR spectra show that heating (up to 180 s at 350 degreesC) increases the aromaticity of the original peat to values typical for black-carbon material, but these charred residues (at least after weight losses of ca. 25%) still contained heat-resistant alkyl carbon. The N-15-NMR spectrum of the original peat is dominated by a signal at -258 ppm, suggesting peptide-like material. In the heated samples a resonance line appearing at lower field indicates progressive formation of pyrrole- and indole-type compounds. Calculations based on weight loss, elemental composition and relative intensity distribution of the 13C- and N-15-NMR spectra demonstrate that the increasing concentrations of aromatic C-types and heterocyclic N-forms with progressive heating are not only caused by a relative enrichment concomitant with the selective thermal degradation of labile structures (mainly O-alkyl and amides) but correspond to newly-synthesised structures that were formed from aliphatic material. (C) 2003 Elsevier Ltd. All rights reserved.