Structural Modification of Lignin in Peat during Peat Formation at Tropical Swamp
Structural Modification of Lignin in Peat during Peat Formation at Tropical Swamp
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DOI：
10.6090/jarq.43.71
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发表时间：
2009-01-01
影响因子：
0.4
通讯作者：
Iiyama, Kenji
中科院分区：
文献类型：
--
作者：
Jin, Zhenfu;Shao, Shunliu;Iiyama, Kenji
从典型的热带泥炭沼泽周围那拉提瓦省，泰国南部，泥炭样品收集从不同深度的泥炭剖面（从表面到2 - 10厘米深），其中的日期建立使用加速器质谱从0到2600年BP。对样品进行了分析，以讨论泥炭形成过程中泥炭样品中木质素结构特征的变化。基于pH调节将样品分级成稀碱可溶性（AL（sol））和不可溶性（AL（insol））级分。在AL（insol）组分中仅检测到葡萄糖基和木糖基残基，而在AL（sol）组分中未检测到单糖。泥炭样品中AL（insol）组分的木质素含量为73.0 ~ 83.3%。木质素在泥炭形成过程中发生了显著的变化。通过硝基苯碱性氧化、官能团分析和分析臭氧化反应，证实了微生物活性对缩合反应、羧基的引入和甲氧基的部分丧失、芳基甘油-β-芳醚键的断裂的影响。本文首次尝试用光谱法对泥炭样品中的木质素进行分离，详细讨论了其结构特征。在H-1-NMR中，6.6和6.9ppm附近的信号与来自新鲜木材的木质素的信号相比相当弱，表明高度缩合。在FTIR光谱中也检测到了来自新鲜木材木质素的大部分峰。电离差（Δ E-i）光谱清楚地表明存在非共轭和共轭酚羟基。微生物对泥炭中木质素的改性作用显著。预计进一步改性的木质素片段将溶于水并通过河流流出到海洋中。
Peat samples from typical tropical peat swamp around Narathiwat Province, southern Thailand, were collected from various depths of peat profile (from surface to 2 10 cm depth), of which dates were established using an accelerator mass spectrometry from 0 to 2600 years BP. The samples were analysed to discuss changes in structural characteristics of lignin in peat samples during peat formation. The samples were fractionated based on pH adjustment into dilute alkali soluble (AL(sol)) and insoluble (AL(insol)) fractions. Only glucosyl and xylosyl residues were detected in AL(insol) fraction, but no monosaccharide in AL(sol) fraction. Lignin contents of AL(insol) fraction of the peat samples ranged from 73.0 to 83.3%. Lignin was significantly modified during peat formation. The progress of condensation reactions, introduction of carboxyl groups and partially loss of methoxyl groups, cleavage of arylglycerol-beta-aryl ether linkage, were confirmed by alkaline nitrobenzene oxidation, functional group analysis and analytical ozonation, respectively, due to the microbial activities. Lignin of the peat samples was isolated by Bjorkman's procedure to discuss structural feature in detail using spectrometrical procedures as the first trial in the field of geochemistry. The signals around 6.6 and 6.9 ppm in H-1-NMR were considerably weak compare with those of lignin from fresh wood, suggesting high condensation. The most peaks originating from lignin of fresh wood were also detected in the FTIR spectrum. The ionization difference (Delta E-i) spectrum clearly showed the presence of unconjugated and conjugated phenolic hydroxyl groups. Thus, lignin in peat was modified significantly by microbial activities. It is expected that further modified fragments of lignin would be soluble in water and flow-out to ocean through rivers.