Archaeological wood degradation at the site of Biskupin (Poland): Wet chemical analysis and evaluation of specific Py-GC/MS profiles

Abstract

Eight samples of ca. 3000 year old oak wood from the Biskupin site and a piece of sound oak (Quercus sp.) wood were analysed. The degradation state of archaeological oak wood was investigated using two analytical approaches: classical wet chemical analysis and analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) with in situ silylation. The results were compared with those obtained for sound oak wood. Chemical analysis provided information on the amount of wood components. Their alteration at a molecular level was investigated by Py-GC/MS, highlighting how degradation can affect the formation of primary and secondary wood pyrolysis products. The results showed that the chemical changes in the wood material in the eight samples examined had different entities and extents with comparison to sound oak wood. Samples taken from the external parts of the fragments had undergone a significant loss in polysaccharide components, whereas the internal parts were in a relatively good state of preservation. Evaluation of the relative amounts of pyrolysis products deriving from holocellulose and lignin highlighted that specific categories of compounds, such as lignin monomers and anhydrosugars, can be taken as an index for good preservation of wood components. These results will be used to evaluate the effectiveness of the in situ conservation strategy by repeating the analyses on these samples after some years and comparing the results

New insights into the degradation processes and influence of the conservation treatment in alum-treated wood from the Oseberg collection

“…This was in agreement with the results obtained by FTIR as well as with pyrolysis results previously obtained for the extremely degraded woods from the 185 series [4]. As lignin is the major polymer remaining in the samples, lignin-derived pyrolysis products were examined in greater detail by sorting them into six categories [25]: monomers (intact lignin units of coniferyl and sinapyl alcohols), long chain (compounds with three carbons in the side chain, but modified compared to the monomers), short chain (compounds with side chains up to two carbon atoms), demethylated/demethyoxylated (compounds in which methyl or methoxyl groups are removed from the aromatic ring), carbonyl (compounds containing aldehyde and ketone functionalities), and acid (compounds containing carboxyl functionalities). The percentage abundances of each category with respect to total lignin content were calculated for the samples from the 229 fragments and the results shown in Figure 6.…”

Climatically Induced Degradation Processes in Conserved Archaeological Wood Studied by Time-lapse Photography

“…Py(HMDS) GC-MS was applied in the characterization of the wood samples before and after ageing, in order to measure the pyrolytic H/L (holocellulose/ lignin) ratio (Tamburini et al 2015;Braovac et al 2016;Mattonai et al 2016). The analysis was carried out on all samples in the present experiment, but no results on wood polymers were obtained for samples DK-LY-A2, DK-SM-A2, and DK-SM-A3.…”

Even Visually Intact Cell Walls in Waterlogged Archaeological Wood Are Chemically Deteriorated and Mechanically Fragile: A Case of a 170 Year-Old Shipwreck

“…It is known that the covalent link between the carboxyl group of glucuronic acid residue in hemicelluloses and α-hydroxyl group of the lignin represents one kind of covalent links in LCCs [26,27]. In addition, the weak Py-GC/MS signal 2 (2-butenal), weak signal 3 (2-furan methanol) and weak signal 5 (2-hydroxy-3-methyl-2-cyclopenten-1-one) in the pyrogram of the WAW back up these findings [17,[28][29][30][31] (Figure 3B & Table S3). Besides, a band at 1264 cm −1 , ascribed to aromatic C-O stretching vibrations of methoxyl and phenyl propane units in guaiacol rings of lignin, appeared in the FTIR spectrum of VICWs in WAW ( Figure 3I).…”