Radial depth profiling of microbial degradation in waterlogged archaeological wood using maximum water content, X-ray diffraction, infrared spectroscopy, and light microscopy

Abstract This study investigated depth-dependent microbial degradation in waterlogged archaeological wood using an integrated analytical approach combining maximum water content (MWC), X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and light microscopy. These methods were systematically applied to increment cores extracted from three hull logs (left bottom log 3-3, right bottom log 1-1, and right bottom log 2-1) recovered from the Mado shipwreck No. 2 (AD 1151–1224) in the Yellow Sea, Republic of Korea. Logs 3-3 and 1-1 were normal wood, whereas log 2-1 was identified as compression wood. Each core was sectioned at approximately 1 cm intervals from the surface inward, and all analyses were conducted on the same depth-resolved sections, enabling direct comparison among physical, chemical, and anatomical indicators. This approach successfully delineated degraded zones, revealing consistent relationships among elevated MWC values, reduced crystallinity, ATR-FTIR evidence of polysaccharide loss and lignin enrichment, and microscopic signs of microbial attack. Degradation depths varied markedly among logs (approximately 4–5 cm in log 3-3, 9–9.5 cm in log 1-1, and ∼1 cm in log 2-1), underscoring the need for log-specific evaluation, even within a single shipwreck, for accurate assessment of preservation states and effective conservation planning.