| 1. |
- Björdal, Charlotte, 1961, et al.
(författare)
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Correlation between sulfur accumulation and microbial wood degradation on shipwreck timbers
- 2019
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Ingår i: International Biodeterioration & Biodegradation. - : Elsevier BV. - 0964-8305. ; 140, s. 37-42
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Tidskriftsartikel (refereegranskat)abstract
- Archaeological shipwreck timber often contains elevated amounts of sulfur and iron rich compounds, accumulated during the long-term exposure in marine environments. This paper investigates if the accumulation of iron and sulfur is correlated and restricted to areas where microbial wood degradation takes place. Examination of microbial degradation in two pine and four oak samples from three historical shipwrecks situated in the Baltic Sea are carried out by light microscopy. Type, degree and amount of wood degradation by fungal and bacterial processes is compared to results on sulfur and iron accumulation studied by X-Ray Fluorescence (XRF) scanning. The highest accumulation of iron and sulfur is found in the surface layers (0–2cm), where microbial degradation is also most intense. A novel finding is that both decay by erosion bacteria- and soft rot fungi promotes accumulation. Our results also imply that accumulation of inorganic sulfur and iron in archaeological wood involves several different processes which might include solely chemical as well as biogeochemical processes. The processes are different in pine compared to oak and the wood species of the shipwreck timber might therefore have a more important role than previously assumed.
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| 2. |
- Fors, Yvonne, 1975, et al.
(författare)
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A study on correlation between microbial decay and accumulation of sulfur and iron in shipwreck timbers of oak.
- 2016
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Ingår i: Proceedings of the ICOM Group on Wet Organic Archaeological Materials Conference. - Lulu : Interntional Council of museums, Committee for conservation (ICOM-CC). - 9789290124368
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Konferensbidrag (refereegranskat)abstract
- Abstract The presence of sulfur and iron compounds in waterlogged archaeological shipwreck timbers excavated from the sea has been given scientific attention during the last 25 years. The contaminants have led to complications for both the wood conservation treatments and later on when displayed in a museum environment. The aim of this study was to further understand the process of accumulation of sulfur and iron in waterlogged archaeological wood. Results from previous laboratory experiment suggested that accumulation of reduced sulfur and iron compounds were associated to the wood decay process. Our hypothesis was that accumulation of sulfur and iron follows the wake of microbial degradation, and is therefore indirectly related to the decay process of wood in marine environment. In order to test the hypothesis and confirm the laboratory studies on modern wood, two samples from recently excavated shipwreck timbers were analysed. The distribution of sulfur and iron were mapped by non-destructive scanning X-ray Fluorescence (XRF), and observations on microbial degradation were carried out by light microscopy. The result confirms a correlation between microbial degradation of the wood and presence of sulfur and iron in the wood.
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| 3. |
- Fors, Yvonne, 1975-, et al.
(författare)
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Ammonia Treatment of Acidic Vasa Wood
- 2009
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Ingår i: Proceedings 10th ICOM-CC WOAM Conference, Amsterdam 2007. - Bremerhaven. - 978 90 5799 1394 ; , s. 539-561
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 4. |
- Fors, Yvonne, 1975
(författare)
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Biochemical fingerprints in marine-archaeological wood – an overview of a research project
- 2015
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Ingår i: Proceeding title: Condition 2015. Conservation and Digitalization. Editors: Katarzyna Piotrowska and Piotr Konieczny. Conference: Condition 2015. Conservation and Digitalization, National Maritime in Gdansk, 19-22 May 2015. - 9788364150104 ; , s. 79-82
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Konferensbidrag (refereegranskat)abstract
- Biochemical fingerprints in marine-archeological wood. Marine-archaeological wood is generally considered well-preserved compared to organic archaeological finds in terrestrial sites. The seabed environment may however inflict wood degradation and contamination with consequences for the long-term preservation. The major reasons for these preservation challenges and for the tremendous undertaking of conserving waterlogged wood can be traced to biochemical seabed activities. Biological degradation in form of fungi and bacteria are weakening the wood cells and is associated with accumulation of inorganic elements, such as sulfur and iron, which in turn may lead to the formation of different acids in the wood. This motivates studies of the accumulation profile of elements in wood from a number of archaeological shipwrecks. Scanning wood cores with X-ray Fluorescence (XRF) enables detailed mapping of the concentration and distribution of inorganic elements at narrow steps throughout the wood. This revealed a strong correlation between the sulfur and iron profiles, suggesting these elements to be accumulated simultaneously through the formation of iron sulfides. Variations in accumulation pattern of total sulfur and iron in wood from different shipwrecks can be explained by differences in the seabed environment. Submerged wood provides strongly environment-adaptive ecosystems of high microbial diversity and activity. Therefore the sulfur and iron profile may serve as a biochemical “fingerprint” of the seabed environment. However, to connect the variations to key biogeochemical mechanisms in the environment, deep knowledge about seabed interactions is essential. The state of preservation in terms of biological degradation and accumulation of wood could then be predicted from basic geochemical data.
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| 5. |
- Fors, Yvonne, 1975, et al.
(författare)
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Bridging by networking; Conservation science in practice
- 2016
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Ingår i: 13th ICOM-CC Wet Organic Archaeological Materials (WOAM) Working Group Conference. 16 - 21 May 2016, Florence, Italy.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Abstract Within the cross-disciplinary field of conservation science, experts from a range of disciplines, work side by side: conservators, archaeologists, chemists, biologists, physics, geologists and engineers. Trying to integrate these complex projects with their respective specific set up of theoretical framework, is both stimulating and challenging. New disciplinary perspectives should always be considered as being enriching. It brings alternative views to the interpretation of data and understanding of a material, however it also involves different definitions of terminology. To keep focus in any conservation scientific project it is essential to at an early stage formulate mutual research questions and make all participants both understand and appreciate that each discipline may have different strategies to achieve results. A scientific cross-disciplinary approach is inevitable in order to understand the preservation challenges for archaeological material, and to be able to address the long-term conservation while on display or in storage. The conservation challenges for material of archaeological objects should be understood and described in biological, chemical, mechanical and geological terms. It is not “science coming to the rescue”; on the contrary everybody involved have the opportunity to learn from each other. However, finding the keys to communication within any cross-disciplinary cooperation is required to obtain fruitful results and opens up for new areas of expertise. The Swedish National Heritage Board intends to strengthen the discipline concerned with “archaeological wood” through a project geared to the coordination and communication of knowledge in the field. The aim is to gather experience from previous research and conservation projects and to initiate additional complementary research and method development. The project Archaeological wood and chemistry has established a new network in the field. The endeavor is part of the mandate to collect, coordinate and make research results accessible, and is intended to act as a bridge between research and practical conservation. Since the start in 2013 several workshops and scientific seminaries on the theme conservation science in practice have been arranged, bringing together conservators and scientists within the field.
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| 6. |
- Fors, Yvonne, 1975, et al.
(författare)
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GCMS analyses of direct methylated lipids in binders used in 18th–19th century folk painted interiors in Hälsingland, Sweden
- 2019
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Ingår i: Journal of Archaeological Science: Reports. - : Elsevier BV. - 2352-409X .- 2352-4103. ; 23, s. 127-136
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Tidskriftsartikel (refereegranskat)abstract
- Paint fragments were collected from painted 18th and 19th century interiors from traditional buildings in Hälsingland, Sweden. The aim was to identify binders used by the artists by direct-methylation and GCMS analyses of the lipid fraction in the samples. The lipid content was categorized as mainly animal, plant-based or mixed. The study indicates that used colour tone and possibly also underlying foundation (wood, paper or textile) is essential for the artists´ choice of binder components. Animal-lipid based compounds were found to be used for a wide variety of colours, including mixed colour and several light colour tones. Animal and sometimes mixed lipids seem also to be characteristic for colour fragments from paper and textiles. Red, black and blue colours are quite common among the mixed-lipid category. However, half of blue, green and black colours were found in the vegetable lipid group. A tendency towards the plant-lipids was also indicated in colour samples painted on wood. Many different forms of terpenoids were found among the wood samples, suggesting that its origin can be traced mainly to wood composites, such as extractives. © 2018 Elsevier Ltd
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| 7. |
- Fors, Yvonne, 1975
(författare)
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Kemi i kulturarvets tjänst
- 2015
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Ingår i: Berzeliusdagarna, 23-24 januari, 2015. Arrangör: Svenska Kemistsamfundet.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Kulturarv är ett brett begrepp som omfattar traditioner, språk, konstnärliga verk, historiska lämningar, arkiv- och föremålssamlingar samt kulturmiljöer och kulturlandskap som överförs från generation till generation. Vad som betraktas som kulturarv förändras med tiden och är ett uttryck för samhällets skiftande värderingar. Varje tid bildar sig en egen uppfattning om vad som är kulturarv och vad det betyder. Överallt i vår omgivning finns spåren av det förflutna. Det kan gälla alltifrån enskilda objekt till stora landskapsavsnitt. Kemins och naturvetenskapens betydelse inom kulturvårdsarbete ökar hela tiden i takt med teknikens utveckling, men också genom ett ökat samarbete mellan olika forskningsområden. Naturvetenskapens bidrag gäller allt från dokumentationstekniker och analyser av ett föremåls kemiska sammansättning till DNA-tester av stenåldersindivider. Inom arkeologi och föremålskonservering finns en lång tradition av tvärvetenskapliga samarbeten och behoven av och teknik och efterfrågan på naturvetenskaplig kompetens är hetare än någonsin. För naturvetaren och inte minst kemisten bidrar samarbetet till utveckling och optimering av metoder och tekniker. Hur kemi kan användas i kulturarvets tjänst kommer i detta föredrag att illustreras genom två exempel; bevarandet av regalskeppet Vasa och analyser av Hälsingegårdarnas inredningsmåleri.
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| 8. |
- Fors, Yvonne, 1975, et al.
(författare)
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Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea. The Ghost, the Crown and the Sword.
- 2014
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur and iron concentrations in wood from three 17th 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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| 9. |
- Fors, Yvonne, 1975
(författare)
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Sulfur and iron analyses of the Göta wreck and the Kronan with some comments on the terms for preservation of waterlogged wood.
- 2016
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Ingår i: Proceedings of the 12th ICOM Group on Wet Organic Archaeological Materials Conference, Istanbul 13-17 May, 2013.. - : International Council of Museums, Committee for Conservation, Working Group on Wet Organic Archaeological Materials. - 9781365065194
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Konferensbidrag (refereegranskat)abstract
- Abstract Microbial degradation of waterlogged archaeological wood on the seabed is accompanied by accumulation of iron and sulfur contaminants. The sulfur and iron profiles in core samples from the Göta wreck on the Swedish west coast, and the warship Kronan in the Baltic Sea, were obtained by scanning x-ray fluorescence (XRF). The results generally resemble previous analyses for the Vasa, with high and correlated sulfur and iron concentrations close to the wood surfaces, pointing to initial formation of iron (II) sulfides. However, some earlier analysed core samples from the Göta wreck displayed irregular and high iron concentrations throughout the wood, indicating an additional accumulation mechanism. The sulfur speciation, previously investigated by sulfur K-edge x-ray absorption near edge structure (XANES) spectroscopy, showed that organosulfur species dominate in the interior, while oxidised sulfur species differ between PEG-treated and untreated wood. Using analytical information to connect different sulfur-iron accumulation patterns to the biogeochemical processes that control degradation of wood and organic material at various wreck site environments would be desirable both for improved in-situ preservation of marine archaeological shipwrecks world-wide, and also for designing conservation procedures for recovered shipwrecks. Finally, some suggestions are presented concerning experimental designs for studies on the environmental effects on waterlogged wood.
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| 10. |
- Fors, Yvonne, 1975-
(författare)
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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
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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