Impact of biodeterioration on structure and composition of waterlogged foundation piles from Riga Cathedral (1211 CE), Latvia

Deterioration of Microstructures and Properties in Ancient Architectural Wood from Yingxian Wooden Pagoda (1056 AD) during Natural Aging

“…All FTIR absorbance spectra were normalized at the highest absorbance intensity in the 1800-800 cm −1 region. The peak with the highest absorbance intensity of recent larch woods and ancient architectural woods was observed at 1060 cm −1 , corresponding to the stretching vibrations of C-O in polysaccharides [19]. The results showed that the intensities of the absorbance peaks at 1736 cm −1 (stretching vibrations of unconjugated C=O of the carbonyl, carboxyl, and acetyl groups in xylan, a component of hemicellulose), 1372 cm −1 (bending vibrations of C-H in polysaccharides), and 1159 cm −1 (asymmetric stretching vibrations of C-O-C in polysaccharides) were reduced in ancient architectural woods compared to recent larch woods, indicating partial depletion of polysaccharides, particularly hemicellulose, in ancient architectural woods [1,13,14,19,20,[30][31][32][33][34].…”

“…The results showed that the intensities of the absorbance peaks at 1736 cm −1 (stretching vibrations of unconjugated C=O of the carbonyl, carboxyl, and acetyl groups in xylan, a component of hemicellulose), 1372 cm −1 (bending vibrations of C-H in polysaccharides), and 1159 cm −1 (asymmetric stretching vibrations of C-O-C in polysaccharides) were reduced in ancient architectural woods compared to recent larch woods, indicating partial depletion of polysaccharides, particularly hemicellulose, in ancient architectural woods [1,13,14,19,20,[30][31][32][33][34]. On the other hand, the intensities of the absorbance peaks at 1608 cm −1 (stretching vibrations of the aromatic skeleton combined with the stretching vibrations of C=O in lignin), 1510 cm −1 (stretching vibrations of the aromatic skeleton in lignin), 1458 cm −1 (asymmetric bending vibrations of C-H of -CH 3 and -CH 2 groups in lignin), and 1425 cm −1 (stretching vibrations of the aromatic skeleton combined with in-plane bending vibrations of C-H in lignin) were either similar or slightly increased in ancient architectural woods, indicating well preservation of lignin during longterm natural aging [1,13,14,19,20,[31][32][33]35]. However, the peak at 1651 cm −1 for oxidized lignin units with carbonyl groups at C α was absent in the spectra of ancient architectural woods, indicating degradation of the side chains in lignin [33].…”

“…The natural aging of wood refers to the normal degradation process that occurs after the wood has been cut down in the absence of other accelerating effects [18]. Although ancient architectural woods in ancient timber constructions appear well-preserved, the morphological structures [19], chemical components [19], cellulose crystalline structures [20], and mechanical properties [21] of wood cell walls inevitably deteriorate significantly over time due to the single or combined action of UV irradiation, oxygen, humidity, temperature, and atmospheric pollutants [18]. A study of archaeological elm wood from Chenghuang Temple, China, approximately 350 years old, showed a significant decrease in polysaccharide and lignin content, deterioration of microstructures, and changes in the micromechanical properties of cell walls at the outer part of the wood during natural aging [5].…”