Sulphur and iron compounds common in old shipwrecks
A few years ago scientists reported large quantities of sulphur and iron compounds in the salvaged 17th century warship Vasa, resulting in the development of sulphuric acid and acidic salt precipitates on the surface of the hull and loose wooden objects.
Other vessels also affected
Similar sulphur compounds have now been discovered also in other shipwrecks both from the Baltic and off the west coast of Sweden, including fellow 17th century warships Kronan, Riksnyckeln and Stora Sofia, the 17th century merchant vessel in Gothenburg known as the Göta wreck, and the Viking ships excavated at Skuldelev in Denmark.
“This is a result of natural biological and chemical processes that occur in low-oxygen water and sediments,” explains Yvonne Fors from the University of Gothenburg's Department of Conservation, one of the scientists behind the study in collaboration with Stockholm University.
Preventive action possible
Besides the Vasa, similar problems have previously been reported for Henry VIII's flagship Mary Rose in the UK, which sank off Portsmouth in 1545, and the Dutch vessel Batavia in Australia, which was lost in 1629, the year after the Vasa.
“Our work on the Vasa and the Mary Rose has given us a good insight into these problems,” Yvonne Fors says. “With the right actions, such as new preservation procedures, we'll be better able to prevent these shipwrecks from developing such serious problems with sulphuric acid.”
Toxic hydrogen sulphide reacts with wood
Even in low-oxygen-water, bacteria can break down organic material including the wood cells in a vessel's hull. Sulphates that occur naturally in the water are transformed by bacteria into toxic hydrogen sulphide which reacts with the wood. In the presence of iron ions, sulphur and iron compounds form which readily oxidise into sulphuric acid and acid salt precipitates in a damp museum environment once the vessel has been recovered.
“For some of the wrecks, such as the Skuldelev Viking ships and the Göta wreck, the conservation treatment is already finished,” says Fors. “It's then a matter of keeping an eye on the chemical developments, which requires additional resources.”
Many of the chemical analyses in the study were performed at the advanced radiation facilities at SSRL in Stanford in the USA and at ESRF in France.
Media Contact
More Information:
http://www.gu.seAll latest news from the category: Earth Sciences
Earth Sciences (also referred to as Geosciences), which deals with basic issues surrounding our planet, plays a vital role in the area of energy and raw materials supply.
Earth Sciences comprises subjects such as geology, geography, geological informatics, paleontology, mineralogy, petrography, crystallography, geophysics, geodesy, glaciology, cartography, photogrammetry, meteorology and seismology, early-warning systems, earthquake research and polar research.
Newest articles
Lighting up the future
New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…
Researchers crack sugarcane’s complex genetic code
Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….
Evolution of the most powerful ocean current on Earth
The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….