Correlation between bacterial decay and chemical changes in waterlogged archaeological wood analysed by light microscopy and Py-GC/MS

Holzforschung | Ahead of Print Correlation between bacterial decay and chemical changes in waterlogged archaeological wood analysed by light microscopy and Py-GC/MS Nanna Bjerregaard PedersenORCID iD: https://orcid.org/0000-0002-5744-939X , Jeannette Jacqueline ŁucejkoORCID iD: https://orcid.org/0000-0002-7717-4039 , Francesca ModugnoORCID iD: https://orcid.org/0000-0002-0446-668X and Charlotte Björdal DOI: https://doi.org/10.1515/hf-2020-0153 | Published online: 20 Nov 2020 PDF view on new site Abstract Full Text PDF References Recommendations Abstract Erosion bacteria are the main degraders of archaeological wood excavated from waterlogged environments. Light microscopy and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) were exploited to study waterlogged archaeological wood (Pinus sylvestris L.) at different stages of bacterial decay. The research explored the biochemical changes related to erosion bacteria degradation of the secondary cell wall in the wood cells and the chemical changes related to abiotic processes induced by the long-term waterlogged burial environment. Erosion bacteria were demonstrated by chemical analysis to cause significant holocellulose depletion. Detailed analysis of the holocellulose and lignin pyrolysis products revealed only minor chemical changes in the residual structure even after heavy erosion bacteria decay. Chemical changes in the lignin polymer is associated to enzymatic unlocking of the lignocellulose to gain access to the holocellulose fraction of the cell wall. Chemical changes in the holocellulose fraction are suggested to stem from depolymerisation and from alterations in the polymer matrix of the residual wood cell wall structure. Interestingly, a difference was observed between the sound reference wood and the waterlogged archaeological wood without erosion bacteria decay, indicating that long-term exposure in waterlogged environments results in partial decay of the holocellulose even in absence of bacterial activity

Bacterial and abiotic decay in waterlogged archaeological Picea abies (L.) Karst studied by confocal Raman imaging and ATR-FTIR spectroscopy

Waterlogged archaeological Norway spruce [Picea abies (L.) Karst] poles were studied by means of confocal Raman imaging (CRI) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis to determine lignin and polysaccharide composition and distribution in the cell wall. The waterlogged archaeological wood (WAW) was submerged under anoxic conditions for approximately 400 years and solely decayed by erosion bacteria (EB). CRI showed that decayed tracheids contain a residual material (RM) with heterogeneous lignin distribution; within the same tracheid RM often contained regions with intensities lower than sound S2 layers up to intensity values as high as the compound middle lamella (CML). CRI revealed strong depletion of carbohydrates in RM which indicated that EB are able to utilise the carbohydrate fraction of the cell wall effectively. Raman bands assigned to lignin did not show any difference between RM and sound S2. This is a hint that EB do not modify the lignin structure. Sound WAW free from EB decay showed evidence of loss of acetyl groups in glucomannan, loss of un-conjugated ester linkages in the lignin-carbohydrate complexes between xylan and lignin, and minor oxidation of the lignin polymer compared to recent reference material. This is evidence for abiotic decay in the course of waterlogging

Sampling for wood decay analyses of cable car trestles and houses at Svalbard. Field report

This report is a documentation of the field data collection and sampling at Svalbard in 2022 within the project ArcticAlpineDecay. The sampling methods are described and for each object sampling was performed documentation is provided, incl. location, Askeladden ID, map coordinate, photo documentation and illustration of sampling. Compilation of the results from the project will be published in peer review journals and in a final report from the project.Sampling for wood decay analyses of cable car trestles and houses at Svalbard. Field reportpublishedVersio