TY - JOUR

T1 - Bacterial and abiotic decay in waterlogged archaeological Picea abies (L.) Karst studied by confocal Raman imaging and ATR-FTIR spectroscopy

AU - Pedersen, Nanna Bjerregaard

AU - Gierlinger, Notburga

AU - Thygesen, Lisbeth Garbrecht

PY - 2015

Y1 - 2015

N2 - 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.

AB - 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.

U2 - 10.1515/hf-2014-0024

DO - 10.1515/hf-2014-0024

M3 - Journal article

VL - 69

SP - 103

EP - 112

JO - Holzforschung

JF - Holzforschung

SN - 0018-3830

IS - 1

ER -