Environmentally hazardous wrecks under investigation

Some 30 wrecks off the Swedish coast have been identified as potential environmental hazards. FOI has been taking part in a project to devise methods of measuring the current environmental impact of the wrecks and to assess the future environmental threat posed by the wrecks as they continue to rust away.

The work has been led by the Swedish Maritime Administration which has also been assisted by Chalmers Lindholmen, the Swedish Coast Guard, the National Maritime Museums and the Swedish Agency for Marine and Water Management, HaV.

It is the diesel oil in the ships’ tanks, and in some cases the cargo of oil, that poses the greatest danger to the environment. There are, however, also German vessels that were sunk at Måseskär, outside Orust, after the Second World War. They were loaded with mustard gas, often with the addition of arsenic.

This investigative work has included the creation of models to:

• see whether there is oil adjacent to the wreck and, if so, whether it has come from the wreck or from another source,
• see how the oil seepage is affecting life on the seabed,
• find methods for determining whether there is oil in the wreck’s tanks and, if so, whether it is feasible to empty them.

“The aim was to create a methodology involving checklists so that everyone knows what they are looking for, which experts should be called in, and so on,” says Anders Östin, a scientist at FOI.

FOI’s role has primarily been to supply the expertise in chemical analysis and to place its laboratories at the disposal of the project. FOI experts, together with ecotoxicologists from Chalmers, then created a model which shows how different concentrations of oil affect marine life and plant growth.

Even though these models are for oil, this method of working is applicable for all kinds of substances.

The Swedish Maritime Administration, with help from FOI, also carried out measurements on the wreck containing war gases at Måseskär. These measurements showed that arsenic is being spread in the local waters which are very rich in fish.

“We were convinced that fishing in the proximity of the wreck was prohibited but that proved not to be the case. A number of fishing vessels were trawling in the area, in fact one of them actually trawled up our measuring equipment,” adds Anders Östin.

So how great a danger to the environment does this pose?

“If you ask us who work in in defence what we think, the answer is that we do not see any appreciable risk to humans provided that one keeps clear of the area. But if you talk to our ecotoxicologist colleagues, they are looking at how the composition of the organisms, and their reproductive capabilities, are being affected,” says Anders Östin.

This work was reported at the international ‘wreck conference’ Wrecks of the World III held in Gothenburg in October. The methods developed are now being brought into everyday use.

At the conference the working group suggested that HaV should be the authority responsible for work in this area and for deciding on what action should be taken with regards to shipwrecks and their adjacent sea areas.