Deterioration mechanisms of archaeological wood inside the bronze parts of excavated chariots from the Western Han dynasty.

• Copper cations of bronze corrosion products were concentrated into the middle lamella (ML) of cell walls, and intensively fixed on the surface of cell lumen. • Cellulose was well-preserved in archaeological wood contaminated by copper corrosion, but lignin was severely degraded. • Iron underwent an intense Fenton reaction and produced hydroxyl radicals, resulting in wood polymer degradation accelerating. The deterioration mechanism of wooden archaeological artifacts inside the bronze of excavated chariots is not understood because it is unknown how bronze corrosion products affect the degradation of archaeological wood. In this paper, several microtopography and chemical analysis methods were used to characterize changes in the hierarchical structures and analyze the deterioration mechanisms of archaeological wood inside the bronze parts of chariots. The results indicated that some important components of chariots in ancient China mainly were made of Ulmus spp. and Pteroceltis tatarinowii woods due to their higher strength and good wear resistance in ancient traditional timber tree species. Furthermore, cellulose was well-preserved in archaeological wood contaminated by copper corrosion, especially crystalline cellulose, but lignin and hemicelluloses were severely degraded. The crystallite thickness and crystallinity of cellulose were also higher than those of more recent wood, but the arrangement of cellulose was disoriented. Copper cations of bronze corrosion products were concentrated into the middle lamella (ML) of cell walls and fixed on the inner surface of cell lumen. The micro-distributions of copper and lignin were correlated. However, iron components embedded in bronze underwent an intense Fenton reaction and produced hydroxyl radicals that penetrated the wood and accelerated wood polymer degradation. With an understanding of this deterioration mechanism, it is possible to determine possible conservation and preservation methods, including the development of copper preservatives and the desalination of iron compounds. [ABSTRACT FROM AUTHOR]