Abstract:

Objective: In this study, the degradation degrees of archaeological wood samples of three typical compartments of the “Nanhai Ⅰ” shipwreck was tested and analyzed by multi-dimensional testing methods, aiming to scientifically evaluate their preservation condition and provide theoretical basis and technical support for the protection and restoration of the shipwreck. Method: The representative cabins 4, 7 and 11 of the “Nanhai Ⅰ” shipwreck were targeted, and the systematic monitoring and analysis was conducted in 2023 and 2024. A total of 41 archaeological wood samples were collected from 30 monitoring sites for 5 types of shipwreck components. Optical microscopy was used to identify tree species, and the anatomical features of wood degradation were systematically observed. The maximum water content (MWC) and basic density (BD) of the wood samples were measured. Attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR) was used to obtain the chemical structure information of archaeological wood samples, and principal component analysis (PCA) was applied to process the ATR–FTIR spectral data. Result: The materials for the selected components of the “Nanhai Ⅰ” shipwreck were mainly hardwood pines (Pinus sp.), accounting for 62%. The shipwreck timber from three cabins exhibited similar degradation conditions. The wood degradation progressed from the surface inward, yet exhibited various degradation characteristics across different cabins and monitoring points. Specifically, the wood preservation condition at monitoring points A3 and A6 in cabin 4 remained relatively stable, while point A12 showed a notable difference in the hemicellulose/lignin ratio (H/L) between 2023 and 2024, indicating pronounced degradation of polysaccharide components at this site. In cabin 7, monitoring points A23 and A33 exhibited new enhancement peaks in the wood, with a significant increase in H/L values. With the desalination cleaning of the ship, the wood was less affected by external pollutants, and its preservation condition improved compared with 2023. At point A30, after the removal of exogenous pollutants, the preservation condition remained stable. In cabin 11, points A52 and A58 maintained stable preservation conditions, whereas point A48 displayed reduced absorption peak intensities at 1 725 cm^-1 and 1 645 cm^-1, indicating degradation in the wood. Conclusion: The wood preservation condition of the “Nanhai Ⅰ” shipwreck is poor and is primarily in a moderate to severe state of degradation. There are differences in preservation condition of wood in different compartments or different monitoring sites in the same compartment. Monitoring sites with serious degradation, such as A12 and A48, need to strengthen protection measures, and other sites affected by exogenous substances, such as A23 and A33, need to carry out systematic cleaning and dynamic monitoring.

Key words: “Nanhai Ⅰ” shipwreck, degradation characteristics, anatomical feature, chemical structure, preservation condition