Deterioration of the cell wall in waterlogged wooden archeological artifacts, 2400 years old
Deterioration of the cell wall in waterlogged wooden archeological artifacts, 2400 years old
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2400年前浸水木制考古文物中细胞壁的退化
DOI：
10.1163/22941932-40190241
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发表时间：
2019-11-01
期刊：
影响因子：
1.9
通讯作者：
Yin, Yafang
中科院分区：
文献类型：
--
作者：
Guo, Juan;Xiao, Lin;Yin, Yafang
浸水木质文物细胞壁的超微结构与细胞壁结合水和孔隙游离水的关系是发展固化干燥技术的基础。本文选取了一件公元前世纪的漆木器和一件船棺作为研究对象。木材解剖结果表明，它们属于山桐子属和润楠属，分别SEM观察显示，它们具有典型的海绵状结构，并且它们的含水量显著增加。固体NMR、Py-GC/MS、FTIR显微成像和2D-XRD分析结果表明，木质素的降解是由于半纤维素中的多糖骨架和纤维素氢键网络部分断裂、乙酰基侧链几乎完全消失、β-O-4链节部分缺失以及木质素氧化和脱甲基/脱甲氧基作用的结果。这些进一步导致结晶纤维素的无序排列，以及纤维素微晶尺寸和结晶度的降低。结果，中孔和大孔形成，并且水分吸附位点的数量和它们的可接近性增加。此外，由孔隙结构变化推断的自由水和由GAB模型得到的最大单分子层持水量结果表明，浸水后的文物中的水主要是中孔隙中的自由水。
The relationship between the cell wall ultrastructure of waterlogged wooden archeological artifacts and the state of water bound to cell walls and free in voids is fundamental to develop consolidating and drying technologies. Herein, a lacquer-wooden ware and a boat-coffin dating 4th century BC were selected as representative artifacts to study. Wood anatomy results indicated that they belonged to Idesia sp. and Machilus sp., respectively. They exhibited a typical spongy texture, as revealed by SEM observations, and their water contents had increased significantly. Solid state NMR, Py-GC/MS, imaging FTIR microscopy and 2D-XRD results demonstrated that the deterioration resulted from the partial cleavages of both polysaccharide backbones and cellulose hydrogen-bonding networks, almost complete elimination of acetyl side chains of hemicellulose, the partial depletion of beta-O-4 interlinks, as well as oxidation and demethylation/demethoxylation of lignin. These further caused the disoriented arrangement of crystalline cellulose, and the decrease in cellulose crystallite dimensions and crystallinity. In consequence, mesopores and macropores formed, and the number of moisture-adsorbed sites and their accessibility increased. Moreover, results on free water deduced by the changes of pore structure and the maximum monolayer water capacity achieved by the GAB model indicated that water in waterlogged archeological wooden artifacts was mainly free water in mesopores.