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Halophilic archaea are a unique group of microorganisms that thrive in high-salt environments, exhibiting remarkable adaptations to survive extreme conditions. Archaeological wood and El-Hamra Lake serve as a substrate for a diverse range of microorganisms, including archaea, although the exact role of archaea in archaeological wood biodeterioration remains unclear. The morphological and chemical characterizations of archaeological wood were evaluated using FTIR, SEM, and EDX. The degradation of polysaccharides was identified in Fourier transform infrared analysis (FTIR). The degradation of wood was observed through scanning electron microscopy (SEM). The energy dispersive X-ray spectroscopy (EDX) revealed the inclusion of minerals, such as calcium, silicon, iron, and sulfur, into archaeological wood structure during burial and subsequent interaction with the surrounding environment. Archaea may also be associated with detected silica in archaeological wood since several organosilicon compounds have been found in the crude extracts of archaeal cells. Archaeal species were isolated from water and sediment samples from various sites in El-Hamra Lake and identified as Natronococcus sp. strain WNHS2, Natrialba hulunbeirensisstrain WNHS14, Natrialba chahannaoensis strain WNHS9, and Natronococcus occultus strain WNHS5. Additionally, three archaeal isolates were obtained from archaeological wood samples and identified as Natrialba chahannaoensisstrain W15, Natrialba chahannaoensisstrain W22, and Natrialba chahannaoensisstrain W24. These archaeal isolates exhibited haloalkaliphilic characteristics since they could thrive in environments with high salinity and alkalinity. Crude extracts of archaeal cells were analyzed for the organic compounds using gas chromatography-mass spectrometry (GC-MS). A total of 59 compounds were identified, including free saturated and unsaturated fatty acids, saturated fatty acid esters, ethyl and methyl esters of unsaturated fatty acids, glycerides, phthalic acid esters, organosiloxane, terpene, alkane, alcohol, ketone, aldehyde, ester, ether, and aromatic compounds. Several organic compounds exhibited promising biological activities. FTIR spectroscopy revealed the presence of various functional groups, such as hydroxyl, carboxylate, siloxane, trimethylsilyl, and long acyl chains in the archaeal extracts. Furthermore, the archaeal extracts exhibited antioxidant effects. This study demonstrates the potential of archaeal extracts as a valuable source of bioactive compounds with pharmaceutical and biomedical applications.

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Archaeological wood can be preserved in waterlogged conditions. Due to their degradation in the ground, these archaeological remains are endangered after their discovery, since they decay irretrievably during drying. Conservation measures are used to preserve waterlogged archaeological objects, maintaining their shape and character as much as possible. However, different methods have been developed leading to varying results. This study compares their effectiveness in order to clarify their mode of action. The methods including alcohol-ether resin, lactitol/trehalose, melamine formaldehyde, polyethylene glycol impregnation prior to freeze-drying, saccharose and silicone oil were assessed by analysing mass changes and volume stability using structured-light 3D scanning. The state of the conserved wood samples including the spatial distribution of the conservation agent was examined using synchrotron micro-computed tomography. Raman spectroscopy was used to observe the agent´s spatial distribution within the cells. The findings demonstrated that melamine formaldehyde stabilises the degraded cell walls. The lumens are void, as in the case with alcohol-ether resin, while polyethylene glycol, silicone oil, saccharose and lactitol/trehalose also occupy the lumens. It is assumed that the drying method has an effect on the distribution of the solidifying agent. The knowledge gained affords insights into the mechanism of conservation methods, which in turn accounts for the varied outcomes. It also allows conclusions to be drawn about the condition and stability of conserved museum objects and serves as a starting point for the further development of conservation methods.

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Luoyang No.1 is a Qing Dynasty (1644-1902) inland river ancient wooden shipwreck discovered in September 2013. It adds significantly to the study of Grand Canal transport history and Luoyang's economic history. The wood characteristics of Luoyang No.1 were investigated in this study using chemical compositions, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nano-indentation (NI), and scanning electron microscopy (SEM). The results showed that the holocellulose content was only 32.84-37.69%, indicating that the cellulose and hemicellulose had been seriously degraded. Based on the XRD pattern, the degree of crystallinity of cellulose in wood ranged from 19.82 to 22.83%. The nano-indentation demonstrated that compared with the undegraded contemporary wood, the elastic modulus and hardness of the ancient ship wood decreased by 45.5% and 32.1%, respectively. Furthermore, the FTIR spectra revealed that the biological deterioration of ancient wood was indicated by a decrease in the peaks related to cellulose and hemicellulose, but the change in lignin was insignificant. The results could provide knowledge for appropriate dewatering, strengthening, restoration strategies and regulation of the museum environment.

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Huaguangjiao I refers to the ancient Chinese wooden shipwreck of the South Song Dynasty (1127-1279 AD) discovered in the South China Sea in 1996. From 2008 to 2017, the archaeological waterlogged wood was desalted using deionized water combined with ultrasonic treatment, and desalted using EDTA-2Na, EDTAHO, and NaH2PO4·2H2O solutions. In this paper, the degree of degradation of the modified waterlogged archaeological wood and the moisture and content of the main components were determined. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and scanning electron microscopy (SEM) were employed to investigate the state of wood degradation after desalination and desulfurization. The results showed that the water content of the wood was as high as 532~1149%, while the basic density was only 0.14~0.18 g/cm3, indicating that the wood had been seriously degraded. The holocellulose content was only 36-40%. Based on the XRD patterns, the degree of cellulose crystallinity in the modified wood was 14.08%. The elastic modulus and hardness of the ancient shipwreck wood after desalination and desulfurization were 1.28-4.31 and 0.10-0.28 GPa, respectively, according to nanoindentation. In addition, the FTIR spectra revealed that the biological deterioration of the modified wood caused cellulose and hemicellulose degradation, but no apparent lignin alteration occurred. The results could provide knowledge for appropriate dewatering, strengthening, and restoration strategies.

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Non-destructive preservation state estimation is an essential prerequisite for the preservation and conservation of waterlogged archaeological wooden artifacts. Herein, Near Infrared (NIR) spectroscopy coupled with orthogonal partial least squares discriminant analysis (OPLS-DA) were applied to assess sixty-four waterlogged archaeological woods collected from seven excavation sites in the period range of 2900 BCE-1912 CE, aiming at developing a non-destructive, accurate and rapid preservation state estimation methodology. The role of non-decayed recent wood of relevant species on preservation state estimation was studied in prior, showing the use of non-decayed recent wood could not improve the predictive ability. Besides, the high variability in terms of chemical structure between archaeological softwoods and archaeological hardwoods did affect the preservation state estimation. Thus, a simple OPLS-DA model of non-destructively distinguishing archaeological hardwoods from softwoods, R2Xcum of 0.659, R2Ycum of 0.836 and Q2cum of 0.763, was established to avoid and overcome destructive approach for wood identification. Then, the well-defined three grouped separations of slightly-decayed, moderately-decayed and severely-decayed waterlogged archaeological woods were revealed in OPLS-DA models, providing R2Xcum of 0.793, R2Ycum of 0.738, Q2cum of 0.680, and R2Xcum of 0.780, R2Ycum of 0.901, Q2cum of 0.870, for waterlogged archaeological hardwoods and waterlogged archaeological softwoods respectively. Potential predictive wood spectral bands were screened and tentatively identified as hydroxyls of crystalline cellulose, acetyl groups of hemicelluloses, C-H bands of lignin, which guaranteed the elimination of non-structural compounds, such as water and inorganic components interference. Furthermore, the developed NIR methodology was validated by an extensively used destructive method consisting of anatomical characteristics, maximum water content and basic density analyses. The results indicated that NIR coupled to chemometrics could non-destructively and accurately predict the preservation states of waterlogged archaeological wooden artifacts and avoid the interference of water and inorganic deposits.

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Some organosilicon compounds, including alkoxysilanes and siloxanes, proved effective in stabilizing the dimensions of waterlogged archaeological wood during drying, which is essential in the conservation process of ancient artifacts. However, it was difficult to determine a strong correlation between the wood stabilizing effect and the properties of organosilicon compounds, such as molecular weight and size, weight percent gain, and the presence of other potentially reactive groups. Therefore, to better understand the mechanism behind the stabilization effectiveness, the reactivity of organosilicons with wood polymers was studied using a 2D 1H-13C solution-state NMR technique. The results showed an extensive modification of lignin through its demethoxylation and decarbonylation and also the absence of the native cellulose anomeric peak in siloxane-treated wood. The most substantial reactivity between wood polymers and organosilicon was observed with the (3-mercaptopropyl)trimethoxysilane treatment, showing complete removal of lignin side chains, the lowest syringyl/guaiacyl ratio, depolymerization of cellulose and xylan, and reactivity with the C6 primary hydroxyls in cellulose. This may explain the outstanding stabilizing effectiveness of this silane and supports the conclusion that extensive chemical interactions are essential in this process. It also indicates the vital role of a mercapto group in wood stabilization by organosilicons. This 2D NMR technique sheds new light on the chemical mechanisms involved in organosilicon consolidation of wood and reveals what chemical characteristics are essential in developing future conservation treatments.

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Cultural heritage objects made of wood can be preserved under waterlogged conditions for many years, where decay is slowed down and the wood structure is more or less completely filled with water. Depending on the degree of degradation, finds may collapse and shrink when they are allowed to dry in an uncontrolled manner after excavation, leading to total loss of the object and its information. Conservation measures are taken to prevent damage of objects and dimensional stability is an important criterion. In this study, structured-light 3D scanning and micro-computed tomography were used to analyse the dimensional stability of wood after conservation, as well as its long-term stability. 83 samples from a reference collection established between 2008 and 2011 allowed this comparative study of the most common conservation methods at that time. The effects of conservation methods using alcohol-ether resin, melamine-formaldehyde (Kauramin 800®), lactitol/trehalose, saccharose, and silicone oil on dimensional stability were investigated. In addition, different polyethylene glycol (PEG) treatments with subsequent freeze-drying were also investigated: one-stage with PEG 2000, two-stage with PEG 400 and PEG 4000 and three-stage with PEG 400, PEG 1500 and PEG 4000. The data received from analyses of both volume and surface gave detailed information about the success of each conservation method. Attempts were made to quantify the damage patterns, specifically shrinkage, collapse, and cracks. While PEG and freeze-drying, alcohol-ether-resin, as well as the Kauramin 800® method gave the best results, analysis also highlighted the failures of each method.

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This project focuses on innovative biological methods of extraction for the preservation of waterlogged wood suffering from salt precipitation and acidification. The principal investigator and her team proposed to exploit biomineralization capacities of some bacteria for anticipating the extraction of iron and sulfur compounds when wood is still wet. A comprehensive assessment of the extraction performances achieved on wood objects from lake and marine environments will allow a versatile extraction method to be proposed to end-users.

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In this study, wood samples extracted from the Taicang ancient ship, dating back to the Yuan Dynasty, were investigated to study the characteristics of waterlogged archaeological wood. The macroscopic characteristics and microscopic structures were used to identify the wood species. To assess the degree of degradation of the waterlogged archaeological wood, X-ray diffraction (XRD), nanoindentation (NI), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to compare the new and ancient wood samples from the same species. The microscopic structures of the samples were identified as Pinus massoniana. The XRD and nanoindentation results revealed that the crystallinity index of the cellulose decreased from 41.07% to 33.85%, the elastic modulus was reduced by 20.90%, and hardness was reduced by 55.6% compared with the new wood. The FTIR spectra revealed that biological deterioration occurred in the cellulose and hemicellulose, but there was no noticeable change in the lignin content. These results provide helpful information for the conservation and restoration of ancient ships.

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Large amounts of archaeological wood are often excavated during groundworks in cities and towns. Part of the unearthed artefacts is usually saved, conserved and then presented in museums. However, if the finding contains several similar objects, some of them could potentially be further employed for some other practical purposes. The research aimed to determine the mechanical performance of the remains of wooden water mains excavated at Bóznicza street in Poznan, Poland and evaluate its potential usefulness for any practical purposes. First, wood density was determined along with its mechanical strength in compression. The density of archaeological wood identified as Scots pine was lower than contemporary pinewood (383 kg × m-3 vs. 572 kg × m-3); therefore, its mechanical properties in compression tests were also lower, as expected, making the wood unsuitable for any practical applications. However, the differences in modulus of elasticity and compressive strength were not justified by the differences in wood density. Further infrared spectroscopy and X-ray diffraction analyses revealed additional differences in chemical composition and cellulose crystallinity between archaeological and contemporary wood. The results indicated the decrease in carbohydrate content and cellulose crystallinity in degraded wood, which, in addition to wood density, apparently contribute to the deterioration in mechanical strength of archaeological wood. The case study of the excavated archaeological wooden pipes shows that they have historical value but are not useful for practical purposes. It also revealed that not only wood density but also its chemical composition and cellulose crystallinity level has a substantial impact on the wood mechanical properties, particularly in compression.

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Waterlogged wood treatment with methyltrimethoxysilane (MTMS) proved effective in stabilising wood dimensions upon drying (anti-shrink efficiency of 76-93%). Before the method can be proposed as a reliable conservation treatment, further research is required that includes the evaluation of the mechanical properties of treated wood. The aim of the study was to characterise the effect of the treatment on the viscoelastic behaviour of archaeological waterlogged elm and oak wood differing in the degree of degradation. Dynamic mechanical analysis in the temperature range from -150 to +150 °C was used for the study. To better understand the viscoelastic behaviour of the treated wood, pore structure and moisture properties were also investigated using Scanning Electron Microscopy, nitrogen sorption, and Dynamic Vapour Sorption. The results clearly show that methyltrimethoxysilane not only prevents collapse and distortions of the degraded cell walls and decreases wood hygroscopicity (by more than half for highly degraded wood), but also reinforces the mechanical strength by increasing stiffness and resistance to deformation for heavily degraded wood (with an increase in storage modulus). However, the MTMS also has a plasticising effect on treated wood, as observed in the increased value of loss modulus and introduction of a new tan δ peak). On the one hand, methyltrimethoxysilane reduces wood hygroscopicity that reflects in lower wood moisture content, thus limiting the plasticising effect of water on wood polymers, but on the other hand, as a polymer itself, it contributes to the viscous behaviour of the treated wood. Interestingly, the effect of silane differs with both the wood species and the degree of wood degradation.

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Waterlogged archaeological wood is exposed to a high risk of biological degradation during the post-excavation phases of storage and restoration. For this reason, often biocides must be used to preserve wooden remains. In the present work three essential oils (cinnamon, wild thyme, and common thyme) were tested as possible alternative biocides to use in the preservation of waterlogged archaeological wood. The oils were first tested in vitro to establish the minimum inhibitory concentration (MIC) and to evaluate the biocidal activity on selected fungal strains. Then, the established MIC was applied on waterlogged archaeological wood samples and during an actual restoration treatment. The effectiveness of the oils was evaluated through cultural analyses, ATP quantification, and next-generation sequencing. The results showed that the oils caused a significant decrease in the vitality of fungal mycelia grown in vitro and of the microbiota present in treated wood and storage water. Furthermore, an influence on the composition of the bacterial communities of treated wood samples was observed. Although further tests are needed to evaluate interferences with the materials used during restoration procedures, essential oils could be considered as a possible alternative to the currently used biocide.

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This paper describes dynamic mechanical analysis (DMA) experiments on archaeological and contemporary elm tested under air-dry conditions, to explore the suitability of this technique for increasing understanding of the viscoelastic behaviour of archaeological wood. A strong reduction of storage modulus of archaeological elm (AE) was seen in comparison with contemporary wood (CE), resulting from the high degree of wood degradation, notably the reduction in hemicelluloses and cellulose content of AE, as demonstrated by Attenuated Total Reflection-Fourier Transform Infra-Red spectroscopy (ATR-FTIR). The γ relaxation peak was observed in all samples. The γ peak in AE shifted to a higher temperature, and the activation energy for γ-peak motions was lower in AE (29 kJ/mol) than in CE (50 kJ/mol) indicating that motion is less restricted within the degraded AE cell wall, or possibly a difference in the monomer undergoing rotation. Detection of changes in storage modulus are well known, but the DMA temperature scan technique proved to be useful for probing the degree of wood degradation, relating to the changes in location and intensity of secondary relaxation peaks. The γ peak in loss factor can be used to confirm that cell wall degradation is at an advanced stage, and to improve understanding of the internal spatial structure of the degraded wood cell wall.

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High-resolution NMR images on three different present-day wood samples and an archaeological wood specimen were presented and discussed. Although the spatial resolution is still low to perform dendrology for the exact identification of the wooden species, the T2 -spin-density weighted images exhibit contrasts that are in excellent agreement with optical histological images. On the other hand, T2 * and T1 -weighted images provide physiological information that is not obtainable by the usual light microscopic investigations. Moreover, the diffusion-weighted images show the anisotropic behaviour of the water diffusion coefficient quantified along and perpendicularly to vascular bundles (vessels and tracheids), which can be related to the morphology and size of wooden microstructure. This work suggests that high-resolution multiparametric MRI may be a useful tool to increase the information obtainable from the waterlogged archaeological wood remains in a completely non-invasive and non-destructive approach. Therefore, it would be desirable to further develop the hardware and functional characteristics of MRI scanners to improve their potential application in the field of wooden cultural heritage.

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Structural and chemical deterioration and its impact on cell wall mechanics were investigated for visually intact cell walls (VICWs) in waterlogged archaeological wood (WAW). Cell wall mechanical properties were examined by nanoindentation without prior embedding. WAW showed more than 25% decrease of both hardness and elastic modulus. Changes of cell wall composition, cellulose crystallite structure and porosity were investigated by ATR-FTIR imaging, Raman imaging, wet chemistry, 13C-solid state NMR, pyrolysis-GC/MS, wide angle X-ray scattering, and N2 nitrogen adsorption. VICWs in WAW possessed a cleavage of carboxyl in side chains of xylan, a serious loss of polysaccharides, and a partial breakage of ß-O-4 interlinks in lignin. This was accompanied by a higher amount of mesopores in cell walls. Even VICWs in WAW were severely deteriorated at the nanoscale with impact on mechanics, which has strong implications for the conservation of archaeological shipwrecks.

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Wood has been extensively used as a material for different applications over the years, therefore the understanding of different degradation processes in various environments is of great importance. In this study, the infrared spectroscopy, X-ray diffraction and chemometric methods were used to evaluate and compare the structure of archaeological and artificially degraded oak wood. The results clearly show that modifications in the structure of archaeological wood are related to the position of the material in the log (sapwood and heartwood), thus the extent of wood degradation. To identify the possible factors influencing these effects, the control wood samples were exposed to artificial white rot biodegradation with Coriolus (Trametes) versicolor and to alkali treatment (with NaOH solution). Due to the structural similarities between biodegraded wood and control or archaeological samples, this type of decay is likely to occur during natural ageing along with degradation produced by other environmental factors. Further, no real similarity was identified between the alkali treated wood and archaeological samples, indicating that such degradation does not affect wood under natural conditions.

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A large number of archaeological wooden building poles have been excavated from the Hai Menkou site (Yunnan province, China). Lignin can be transformed and altered accompanied with significant loss of carbohydrates during this process. Elucidation of chemical and structural transformations of lignin is of primary importance for understanding both the nature of degradation processes and the structure of waterlogged archaeological wood, and crucial for developing proper consolidation technology and restoring artifacts of historical and cultural value. In this study, state-of-the-art analytical techniques, including SEM, FT-IR, XRD, CP-MAS 13C NMR, 2D-HSQC NMR, 31P-NMR, CRM, GPC and TG analysis, were all employed to elucidate the structural characteristics of lignin in waterlogged and reference Pinus wood. The results interpreted by NMR analysis demonstrated the depolymerization of lignin via cleavage of ß-O-4, ß-5, -OCH3 and some LCC linkages, leading to a higher amount of free phenol OH groups in the lignin from the ancient waterlogged wood as compared to that of the reference wood. Microscopically, it was found that extensive degradation of carbohydrates in cell walls was mainly occurred in secondary cell walls, while the lignin concentrations were relatively increased in CCML and S regions in the plant cell wall of the ancient wood.

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The content of selected elements: Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Ti, V and Zn was determined in archaeological waterlogged oak wood from the Lednica Lake by using the inductively coupled plasma optical emission spectrometry (ICP-OES) method. The concentration of metals (especially heavy metals) in wood is typically specified to characterise this material and evaluate the possibility to use it for industrial purposes. In case of waterlogged archaeological wood intended for further research on new methods of conservation, such an analysis is important for other reasons. As it has been confirmed by numerous conservators and researchers, the presence of metal compounds is a serious problem not only due to their destructive influence on wood tissue but also from a conservation/re-conservation perspective. Metal-containing chemicals may influence conservation treatments by reacting with substances used for wood conservation and causing irreversible damage to wooden objects. Therefore, while developing new solutions for wood conservation, a broad knowledge not only on the state of wood preservation and deterioration but also on interacting chemical factors is required. The results of the research clearly show that content of minerals in waterlogged wood excavated from the bottom of the Lednica Lake considerably exceeded the average percentage of these elements in contemporary wood, which is associated with the mineralisation process. Moreover, variability in metal content was observed between waterlogged and contemporary wood. In waterlogged wood, the highest concentrations of Ca, Fe, Mg and P were observed, while in contemporary oak wood the predominant concentrations of K, Ca, Mn and Si were determined. Statistical analysis showed the variability in content of elements between different archaeological wood zones and contemporary wood. On the basis of the results obtained, it could be concluded that the studied waterlogged wood acted as an adsorbent of elements from water and sediments. High content of metal ions can be an impediment in developing new formulations for conservation, while using this wood as an experimental material. Therefore, while planning to use new chemicals as conservation agents, the possible interactions between chemicals and metals must be taken into consideration.

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Wood artefacts undergo complex alteration and degradation during ageing, and gaining information on the chemical composition of wood in archaeological artefacts is fundamental to plan conservation strategies. In this work, an integrated analytical approach based on innovative NMR spectroscopy procedures, gel permeation chromatography and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC-MS) was applied for the first time on archaeological wood from the Oseberg collection (Norway), in order to evaluate the chemical state of preservation of the wood components, without separating them. We adopted ionic liquids (ILs) as non-derivatising solvents, thus obtaining an efficient dissolution of the wood, allowing us to overcome the difficulty of dissolving wood in its native form in conventional molecular solvents. Highly substituted lignocellulosic esters were therefore obtained under mild conditions by reacting the solubilised wood with either acetyl chloride or benzoyl chloride. A phosphytilation reaction was also performed using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholan. As a result, the functionalised wood developed an enhanced solubility in molecular solvents, thus enabling information about modifications of lignin, depolymerisation of cellulose and structure of lignin-carbohydrate complexes to be obtained by means of spectroscopic (2D-HSQC-NMR and 31P-NMR) and chromatographic (gel permeation chromatography) techniques. Py-GC-MS was used to investigate the degradation undergone by the lignocellulosic components on the basis of their pyrolysis products, without any pre-treatment of the samples. The application of all these combined techniques enabled a comprehensive characterisation of the whole cell wall of archaeological wood and the evaluation of its state of preservation. High depletion of carbohydrates and high extent of lignin oxidation were highlighted in the alum-treated objects, whereas a good preservation state was found for the untreated wood of the Oseberg ship. Graphical abstract ᅟ.

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