Kjemisk ammunisjon senket utenfor norskekysten etter andre verdenskrig - hva er senket og hvilke effekter har dette på marine organismer?

Large amounts of chemical munitions were dumped at sea at many locations worldwide just after the Second World War. Much of the German chemical munitions were, after pressure from the Allies, loaded on to condemned ships and sunk in the deepest part of the Skagerrak. Norwegian authorities gave permission to such dumping at 600-700 m depth, 25 nautical miles southeast of Arendal. Between 130 000 and 160 000 tons of chemical ammunition (gross weight) containing between 41 000 and 48 000 tons of chemical warfare agents might have been dumped in the Skagerrak. A strong public protest against such dumping caused that the last ships were dumped in 1948 at 1000 m depth in the Norwegian Sea. The exact positions of the dumped ships have since then been very uncertain. In 1989, the Norwegian Defence Research Establishment (FFI) carried out a search and localised 15 possible wrecks, of which several were found close to the edge of the search area. One of the wrecks was positively identified as Sesostris, a ship that according to earlier documentation was dumped 13 km away from where it was found. This indicates that the reported positions are in fact very uncertain. During a new investigation of four selected wrecks in 2002, FFI identified small amounts of chemical warfare agents and decomposition products in sediment samples collected close to the wrecks. During a preliminary search in 2009 using the autonomous underwater vehicle HUGIN and sensors with higher resolution, FFI localized 20 wrecks within a small part of the dumping area. In order to locate as many wrecks as possible in the Skagerrak, FFI is currently carrying out a new search with HUGIN in 2015-2016 on behalf of the Norwegian Coastal Administration. Several new wrecks have been discovered during the first part of this investigation, carried out in 2015. The search will end in 2016. It has been uncertain whether the ships sunk outside Lista, including the cruiser Leipzig, also had chemical munitions on board. According to the studied literature, it is not likely that these ships were sunk with chemical munitions on board. Ammunition sunk at sea will corrode over time and the content will be released to the environment. Many factors control the speed of corrosion and the corrosion process will therefore continue for a long time. Some of the agents, like mustard and arsenic compounds, are heavier than water, poorly soluble in water, and will stay on the sea floor many decades after they have been released from the munitions. Nerve agents are more toxic, but also more soluble in water. They will be diluted within hours to non-dangerous concentrations and decomposed to less toxic compounds. Chemical warfare agents are very toxic to aquatic organisms. Humans and animals have to be in direct contact with such agents to significantly risk any injuries. Organisms living on the sea floor close to the dumping sites have a higher health risk than organisms primarily living in the free water masses. The dumped organoarsenic compounds are considered most dangerous with respect to the environmental risk. Elemental arsenic from organoarsenic compounds could accumulate in aquatic organisms and potentially harm them. Investigations from the Baltic Sea has shown that consumption of fish from areas with dumped chemical munitions pose no significant risk.