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Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea: the Ghost, the Crown and the Sword.

Fors Y, Grudd H, Rindby A, Jalilehvand F, Sandström M, Cato I, Bornmalm L - Sci Rep (2014)

Bottom Line: Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood.In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation.Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

View Article: PubMed Central - PubMed

Affiliation: Department of Conservation, University of Gothenburg, Sweden.

ABSTRACT
Sulfur and iron concentrations in wood from three 17(th) century shipwrecks in the Baltic Sea, the Ghost wreck, the Crown and the Sword, were obtained by X-ray fluorescence (XRF) scanning. In near anaerobic environments symbiotic microorganisms degrade waterlogged wood, reduce sulfate and promote accumulation of low-valent sulfur compounds, as previously found for the famous wrecks of the Vasa and Mary Rose. Sulfur K-edge X-ray absorption near-edge structure (XANES) analyses of Ghost wreck wood show that organic thiols and disulfides dominate, together with elemental sulfur probably generated by sulfur-oxidizing Beggiatoa bacteria. Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood. In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation. Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

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XRF-scans of the Ghost wreck samples 1a (A) & 2a (B).The wood was scanned from the outer surface (left) to the inner subsurface (right) along a line in the middle of each sample. Iron and sulfur show fairly interrelated profiles throughout the wood (note the different concentration scales), except at the inner surface of sample Ghost 1a (A) and 2a (B). A region of broader sulfur peaks appears close to the inner surface (right) of sample Ghost 1a, which should be compared to the much sharper sulfur peak in the outer surface (left in figure A) coated with Beggiatoaspp (also Fig. S1). (B) A repeating pattern of broad iron peaks occurs in Ghost 2a.
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f2: XRF-scans of the Ghost wreck samples 1a (A) & 2a (B).The wood was scanned from the outer surface (left) to the inner subsurface (right) along a line in the middle of each sample. Iron and sulfur show fairly interrelated profiles throughout the wood (note the different concentration scales), except at the inner surface of sample Ghost 1a (A) and 2a (B). A region of broader sulfur peaks appears close to the inner surface (right) of sample Ghost 1a, which should be compared to the much sharper sulfur peak in the outer surface (left in figure A) coated with Beggiatoaspp (also Fig. S1). (B) A repeating pattern of broad iron peaks occurs in Ghost 2a.

Mentions: The sulfur and iron accumulation profiles into the wood of all three shipwrecks are similar to the interconnected sulfur and iron profiles in earlier analyses of waterlogged wood from the Baltic Sea, such as the Vasa and the Riksnyckeln56. In general the highest concentrations are found in surfaces in one or both ends of the samples and in wood cracks (Figs. 2,3,4, Figs. S1–S4). The concentration of sulfur is higher than that of iron in all cases but one: the outer surface of sample Sword 1d (Fig. S3B). The iron concentration is generally quite low in the inner parts of the wood, usually below 0.2 mass% total Fe.


Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea: the Ghost, the Crown and the Sword.

Fors Y, Grudd H, Rindby A, Jalilehvand F, Sandström M, Cato I, Bornmalm L - Sci Rep (2014)

XRF-scans of the Ghost wreck samples 1a (A) & 2a (B).The wood was scanned from the outer surface (left) to the inner subsurface (right) along a line in the middle of each sample. Iron and sulfur show fairly interrelated profiles throughout the wood (note the different concentration scales), except at the inner surface of sample Ghost 1a (A) and 2a (B). A region of broader sulfur peaks appears close to the inner surface (right) of sample Ghost 1a, which should be compared to the much sharper sulfur peak in the outer surface (left in figure A) coated with Beggiatoaspp (also Fig. S1). (B) A repeating pattern of broad iron peaks occurs in Ghost 2a.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3936213&req=5

f2: XRF-scans of the Ghost wreck samples 1a (A) & 2a (B).The wood was scanned from the outer surface (left) to the inner subsurface (right) along a line in the middle of each sample. Iron and sulfur show fairly interrelated profiles throughout the wood (note the different concentration scales), except at the inner surface of sample Ghost 1a (A) and 2a (B). A region of broader sulfur peaks appears close to the inner surface (right) of sample Ghost 1a, which should be compared to the much sharper sulfur peak in the outer surface (left in figure A) coated with Beggiatoaspp (also Fig. S1). (B) A repeating pattern of broad iron peaks occurs in Ghost 2a.
Mentions: The sulfur and iron accumulation profiles into the wood of all three shipwrecks are similar to the interconnected sulfur and iron profiles in earlier analyses of waterlogged wood from the Baltic Sea, such as the Vasa and the Riksnyckeln56. In general the highest concentrations are found in surfaces in one or both ends of the samples and in wood cracks (Figs. 2,3,4, Figs. S1–S4). The concentration of sulfur is higher than that of iron in all cases but one: the outer surface of sample Sword 1d (Fig. S3B). The iron concentration is generally quite low in the inner parts of the wood, usually below 0.2 mass% total Fe.

Bottom Line: Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood.In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation.Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

View Article: PubMed Central - PubMed

Affiliation: Department of Conservation, University of Gothenburg, Sweden.

ABSTRACT
Sulfur and iron concentrations in wood from three 17(th) century shipwrecks in the Baltic Sea, the Ghost wreck, the Crown and the Sword, were obtained by X-ray fluorescence (XRF) scanning. In near anaerobic environments symbiotic microorganisms degrade waterlogged wood, reduce sulfate and promote accumulation of low-valent sulfur compounds, as previously found for the famous wrecks of the Vasa and Mary Rose. Sulfur K-edge X-ray absorption near-edge structure (XANES) analyses of Ghost wreck wood show that organic thiols and disulfides dominate, together with elemental sulfur probably generated by sulfur-oxidizing Beggiatoa bacteria. Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood. In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation. Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

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