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Sulfur-Related Conservation Concerns in Marine Archaeological Wood: The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Synchrotron-based sulfur spectroscopy reveals a common concern for marine archaeological wood from seawater: accumulation of reduced sulfur compounds in two pathways. The distribution of sulfur species in the oak wood cell structure was mapped by scanning x-ray spectro-microscopy (SXM). Organically bound sulfur was found within lignin-rich parts, identified mainly as thiols and disulfides by sulfur K-edge x-ray absorption near edge structure (XANES) spectroscopy. Particles of iron sulfides, which may form in the presence of corroding iron, appeared in wood cavities. Cores scanned by x-ray fluorescence (XRF) show that high sulfur accumulation is restricted to the surface layers for the Swedish shipwreck Vasa, while the distribution is rather uniform throughout the hull timbers of the Mary Rose, U.K. Laboratory experiments, exposing fresh pine to simulated seabed conditions, show that the organically bound sulfur develop in reactions between lignin, exposed by cellulose-degrading erosion bacteria, and hydrogen sulfide produced in situ by scavenging sulfate reducing bacteria. With bacteria inoculated from shipwreck samples also iron sulfides formed. The iron sulfides oxidise in high humidity, and are the probable main cause of the numerous outbreaks on the Vasa’s hull of acidic sulfate salts, which were identified by x-ray powder diffraction (XRD). The iron ions catalyse several wood-degrading oxidative processes. Multi-elemental analyses were performed by scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (ESCA). The present amounts of total S remaining in the Vasa and the Mary Rose are estimated to at least 2 tonnes. After the Vasa´s spray treatment with polyethylene glycol solutions ceased in 1979, the continuing oxidation processes are estimated to have produced 2 tonnes of sulfuric acid in the wood. Laboratory experiments to gently neutralize acidic Vasa wood by ammonia gas have been conducted with promising results.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi , 2008. , 105 p.
Keyword [en]
Sulfur accumulation, marine archaeological wood, Vasa, acidity, iron, ammonia, x-ray spectroscopy, cellulose
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
URN: urn:nbn:se:su:diva-7627ISBN: 978-91-7155-624-0 (print)OAI: oai:DiVA.org:su-7627DiVA: diva2:198721
Public defence
2008-06-03, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 09:30
Opponent
Supervisors
Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2011-01-11Bibliographically approved
List of papers
1. The sulfur threat to marine archaeological artefacts: acid and iron removal from the Vasa
Open this publication in new window or tab >>The sulfur threat to marine archaeological artefacts: acid and iron removal from the Vasa
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2003 (English)In: Conservation science 2002: papers from the conference held in Edinburgh, Scotland 22-24 May 2002, London: Archetype Publications , 2003, 79-87 p.Conference paper, Published paper (Other academic)
Abstract [en]

An outbreak of acidity and sulphate salts was observed on the hull of the 17th-century Swedish warship Vasa, following humidity variations in the Vasa Museum during the rainy summer in 2000. Analyses of total sulphur in oak cores sampled from 16 locations showed, in the outermost 2 cm., mean concentrations betwen 0.2 and 6 mass percent. Synchrotron-based sulphur K-edge X-ray absorption spectroscopy revealed that a large amount of elemental sulphur in the moist wood was being oxidised to sulphuric acid, possibly catalysed by iron compounds, with the overall rate estimated to be about 100 kg sulphuric acid annually. Associated acid catalysed hydrolysis of the cellulose threatens the future preservation of the vessel. Results of tests of proposed new treatments using chelating agents to extract iron compounds from waterlogged wood and simultaneously neutralise acid are presented.

Place, publisher, year, edition, pages
London: Archetype Publications, 2003
Identifiers
urn:nbn:se:su:diva-25008 (URN)1-873132-88-3 (ISBN)
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
2. The Vasa’s New Battle: Sulfur, Acid and Iron
Open this publication in new window or tab >>The Vasa’s New Battle: Sulfur, Acid and Iron
2003 (English)Book (Other academic)
Place, publisher, year, edition, pages
Stockholm: National Maritime Museums [Statens maritima museer], 2003. 80 p.
Series
Vasa studies, ISSN 0511-1900 ; 19
Identifiers
urn:nbn:se:su:diva-25009 (URN)91-85268-94-1 (ISBN)
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
3. Analyses of sulfur and iron in marine-archaeological wood
Open this publication in new window or tab >>Analyses of sulfur and iron in marine-archaeological wood
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2005 (English)In: Proceedings of the 9th ICOM Group on Wet Organic Archaeological Materials Conference: Copenhagen 2004 / [ed] Per Hoffmann, Bremerhaven: International Council of Museums, Committee for Conservation, Working Group on Wet Organic Archaeological Materials , 2005, 181-199 p.Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Bremerhaven: International Council of Museums, Committee for Conservation, Working Group on Wet Organic Archaeological Materials, 2005
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-24298 (URN)3-89757-308-3 (ISBN)
Available from: 2007-05-15 Created: 2007-05-04 Last updated: 2011-01-11Bibliographically approved
4. Sulfur Accumulation in the Timbers of King Henry VIII’s Warship Mary Rose: A Pathway in the Sulfur Cycle of Conservation Concern
Open this publication in new window or tab >>Sulfur Accumulation in the Timbers of King Henry VIII’s Warship Mary Rose: A Pathway in the Sulfur Cycle of Conservation Concern
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2005 (English)In: Proceedings of the National Academy of Sciences of the United States of America, PNAS, ISSN 0027-8424, Vol. 102, no 40, 14165-14170 p.Article in journal (Refereed) Published
Abstract [en]

In marine-archaeological oak timbers of the Mary Rose large amounts of reduced sulfur compounds abound in lignin-rich parts such as the middle lamella between the cell walls, mostly as thiols and disulfides, whereas iron sulfides and elemental sulfur occur in separate particles. Synchrotron-based x-ray microspectroscopy was used to reveal this environmentally significant accumulation of organosulfur compounds in waterlogged wood. The total concentration of sulfur in reduced forms is ≈1 mass % throughout the timbers, whereas iron fluctuates up to several mass %. Conservation methods are being developed aiming to control acid-forming oxidation processes by removing the reactive iron sulfides and stabilizing the organosulfur compounds.

Identifiers
urn:nbn:se:su:diva-25011 (URN)10.1073/pnas.0504490102 (DOI)
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
5. Sulfur and Iron in Shipwrecks Create Conservation Concerns
Open this publication in new window or tab >>Sulfur and Iron in Shipwrecks Create Conservation Concerns
2006 (English)In: Chemical Society Reviews, ISSN 0306-0012, Vol. 35, no 5, 399-415 p.Article in journal (Refereed) Published
Abstract [en]

Synchrotron-based sulfur X-ray absorption spectroscopy reveals considerable accumulation of organosulfur (e.g. thiols), pyrite and iron(II) sulfides in marine-archaeological wood preserved in seawater, e.g. for historical shipwrecks such as the Vasa and Mary Rose. In the museum, oxidation of the sulfur compounds in the presence of iron ions may cause severe acidity in the moist wood. This tutorial review discusses developments of conservation methods to remove acid and iron, and how to analyse and stabilise sulfur compounds in the wood.

Identifiers
urn:nbn:se:su:diva-25012 (URN)10.1039/b507010b (DOI)
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
6. Ammonia Treatment of Acidic Vasa Wood
Open this publication in new window or tab >>Ammonia Treatment of Acidic Vasa Wood
2009 (English)In: Proceedings 10th ICOM-CC WOAM Conference, Amsterdam 2007 / [ed] Per Hoffmann, Bremerhaven, 2009, 539-561 p.Conference paper, Published paper (Other academic)
Abstract [en]

Outbreaks of acidic sulfate salts have been reported in numerous areas on the wooden surfaces of the Swedish historical shipwreck Vasa (from 1628) in the Vasa Museum. Effects of ammonia vapour treatment to reduce the acidity in Vasa wood, similar to that previously applied to the Dutch East Indiaman Batavia (from 1629), have been investigated by means of solid state 13C-NMR and MALDI-TOF spectrometry. No major changes were found in the molecular weight distribution of the bulking agent polyethylene glycol (PEG) or in the crystallinity of pulp cellulose after mild exposure to ammonia vapour. Further studies on the long-term pH stability and the post-treatment properties of the wood using spectroscopic methods and mechanical testing are in progress.

Place, publisher, year, edition, pages
Bremerhaven: , 2009
Series
ICOM, Committee for Conservation, Working Group on Wet Organic Archaeological Materials, 10
National Category
Other Basic Medicine
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-25013 (URN)978 90 5799 139-4 (ISBN)
Conference
10th ICOM-CC WOAM Conference
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
7. Sulfur Accumulation in Pine Wood (Pinus sylvestris) Induced by Bacteria in Simulated Seabed Environment: Implications for Marine Archaeological Wood and Fossil Fuels
Open this publication in new window or tab >>Sulfur Accumulation in Pine Wood (Pinus sylvestris) Induced by Bacteria in Simulated Seabed Environment: Implications for Marine Archaeological Wood and Fossil Fuels
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2008 (English)In: International Biodeterioration & Biodegradation, ISSN 0964-8305, no 62, 336-347 p.Article in journal (Refereed) Published
Abstract [en]

Fresh pine wood blocks were submerged in sulfate and iron(II) containing media, inoculated with bacterial consortia isolated from seawater, aiming to simulate the seabed conditions of the Vasa shipwreck (1628). The consortia contained erosion (EB) and sulfate-reducing bacteria (SRB). Sulfur K-edge x-ray absorption near edge structure (XANES) spectroscopy and scanning x-ray spectromicroscopy images showed that organic sulfur, mainly thiols (R-SH), had accumulated in the lignin-rich middle lamella in EB-degraded parts of the wood. The sulfur content in the wood increased more than 10 times in two years. In another series with active inoculums from marine archaeological wood, the sulfur XANES spectra showed after four years anaerobic treatment considerable amounts also of inorganic iron sulfides, Fe1-xS, which oxidized at atmospheric exposure. A sediment sample from the Vasa’s seabed was also rich in iron sulfides, including pyrite FeS2. X-ray fluorescence mappings of sulfur and phosphorous distributions indicate that scavenging SRB penetration, producing hydrogen sulfide in situ, is restricted to EB-degraded parts of the wood structure. The sulfur isotope depletion of 34S from d34S = 21‰ in marine sulfate to d34S = 6‰ and 1.8‰ for fractions of reduced sulfur and sulfate separated from a Vasa wood sample, respectively, suggests bacterial transformation. A fuller understanding of the routes of sulfur accumulation, as reactive iron sulfides and as organic sulfur, has important implications for improving conservation methods of marine archaeological wood. Moreover, the biogenic accumulation of organically bound sulfur specifically in lignin-rich parts of waterlogged wood has wider geochemical significance for fossil fuels of marine origin, as lignin-rich humic matter is important for the diagenetic formation of kerogens from anoxic marine sediments.

Identifiers
urn:nbn:se:su:diva-25014 (URN)000261010500003 ()
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved

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