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Research article2011Peer reviewed

Distribution of iron and sulfur and their speciation in relation to degradation processes in wood from the Swedish warship Vasa

Almkvist Per Gunnar, Persson Ingmar

Abstract

Wood samples from the Swedish warship Vasa were analysed by scanning electron microscopy and X-ray absorption spectroscopy with the focus on speciation and distribution of iron and sulfur compounds in the wood matrix. Both these elements were found at high concentration (10–100 mg/g) in the surface region as a result of former accumulation of iron sulfides, elemental sulfur and reduced organic sulfur species (ROSS). Below the surface region, iron was the dominating element (1–10 mg/g) present both as iron(II) and iron(III) compounds, which diffused into the wood matrix from corroding iron bolts and other iron items during the time in the sea (1628–1961). Electron microscopy results revealed that iron and sulfur are present in a variety of particles of different sizes and compositions in the surface region, in contrast to the interior where few particles were found. Here, the presence of iron compounds of nano-particle size inside the cell walls enables a close contact between the wood polymers and reactive oxygen species originating from reactions with iron compounds. The presence of ROSS seems to have played an important role as scavengers of reactive oxygen species. Samples with high iron : ROSS ratio displayed evident signs of degradation as indicated by depolymerisation of wood components accompanied by increased acidity due to low molecular organic acids. The observations strengthen the hypothesis of the pro-oxidative and antioxidant properties of iron and ROSS compounds, respectively, and that the chemical activities of these elements play crucial roles in the long term preservation of wooden maritime artefacts

Keywords

Swedish warship Vasa; iron and sulfur speciation; degradation processes; electron microscopy

Published in

New Journal of Chemistry
2011, Volume: 35, number: 7, pages: 1491-1502
Publisher: Royal Society of Chemistry

      SLU Authors

      • UKÄ Subject classification

      Other Chemistry Topics
      Wood Science

      Publication identifier

      DOI: https://doi.org/10.1039/c1nj20056a

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/34687