Tons of Mercury Found in the Baltic Sea Europe's Underwater Chemical Dump

Some 3,500 barrels of mercury have been found in the Baltic Sea off the coast of Sweden. There may be thousands more to be discovered. Experts say the sea is full of industrial waste -- but nobody knows how much.

On August 14, it was 30 barrels. Then it was thousands. And by the end of last week, cartographers with the Geological Survey of Sweden came to the depressing conclusion that there could be as many as 23,000 barrels full of mercury on the floor of the Baltic Sea off the coast of Sweden. Close to ten tons of one of the environment's worst enemies.

The barrels were found by Ingemar Cato of the Geological Survey of Sweden during a routine mission aimed at creating detailed maps of the sea floor along the Swedish coast. After finding the first barrels -- found in 80-meter-deep water in the outer part of Sundsvall Bay about halfway up the east coast of Sweden -- Cato was asked by local county officials to continue looking. While Cato ultimately found 3,500 barrels, recently discovered documents from a local paper mill indicate that the factory may have dumped tens of thousands of barrels in the bay in the 1950s and 60s.

"We knew there were mercury barrels in the bay," Cato told SPIEGEL ONLINE. "In 1976, a fishing trawler pulled one up in its net. For me the surprise was the number."

Cato, though, is quick to admit that perhaps he shouldn't be all that surprised. In addition to his mapping duties, he is also responsible for determining just how much industrial detritus is lying around on the floor of the Baltic Sea. The answer is not terribly reassuring.

"Back in time, it was quite common that you dumped industrial waste into the sea in international waters" -- which used to be a lot closer than the 12 nautical miles standard today. "Fifty years ago, there were no international environmental conventions determining what could be dumped where."

"One of the most polluted seas in the world"

And it's not just industrial waste. Following World War II, virtually the entire chemical arsenal of Nazi Germany was dumped , with much of it -- at least 35,000 tons -- ending up on the floor of the Baltic Sea. Hundreds of thousands of tons of chemical weapons from the Soviet Union, Britain and the United States were also chucked overboard in the northern Atlantic, North Sea, and elsewhere, including the Baltic. The poisonous weapons -- including mustard gas, phosphorus, nerve gas, and other highly toxic chemicals -- were joined by hundreds of thousands of unused bombs, mines and grenades.

Even worse, according to Juhu-Markku Leppänen, a Baltic Sea habitat expert with the Baltic Marine Environment Protection Commission in Helsinki, no technical procedure has yet been developed to enable safe removal of the munitions. The barrels are often corroded and fragile and many of them are embedded in sea floor sediment. In addition to such munitions, numerous ship wrecks containing oil and other fuels litter the sea floor.

"The Baltic Sea is one of the most polluted seas in the world," Leppänen told SPIEGEL ONLINE. Fifty years ago, he says, dumping industrial waste into the sea "was really considered at the time to be good environmental practice." Leppänen also points out that, because the sea's connection with the ocean is so shallow, pollution that flows into the sea from the industrialized countries that surround it tends to stay for at least a quarter century.

As for the solid waste, though, the problem now is finding where exactly those underwater toxic waste dumps are located. Because there were no legal regulations guiding industrial dumping, no records document where waste was placed. The only hope, says Cato, is that information might be found in the archives of factories located along the shores of the sea or that interviews with now-retired factory managers might help. While Sweden and Finland have begun discussing how to begin such a project, no plan has yet been developed to try and locate undersea industrial garbage.

The search to locate more of the mercury barrels in Sundsvall Bay was called off last week after Cato mapped 12 square kilometers in the outer bay. It is now, he says, up to Sweden's environmental protection agency to determine how to move forward. The four barrels that were brought to the surface by Cato's team were corroded by rust and had some holes in them.

The environmental group WWF is calling for the Swedish government to begin recovering the barrels immediately. "These barrels are a ticking time bomb," said Jochen Lamp, a Baltic Sea expert with the WWF, in a press release last week. "When the mercury leaks out, it could have a devastating impact on the environment. Entire fish populations could be poisoned."

Not an acute risk

Once mercury gets into the food chain, it tends to stay and can cause serious nerve, heart and reproduction problems in humans. The most infamous case of mercury poisoning took place in Japan in 1956 when thousands of people got sick in a city called Minamata. As many as 1,400 eventually died of what was dubbed "Minamata Disease."

The mercury off the Swedish coast, though, is mixed with concrete, apparently as part of a strategy to make sure the barrels actually sank. While there is little danger that the mercury will flow out all at once, the chemical makeup of the Baltic Sea means the concrete is breaking down allowing mercury to leech into the water. They pose a risk, says Leppänen, "but not an acute one."

Sweden's mercury barrels are far from the first such find in the Baltic Sea. The Finns pulled up a number of containers full of dangerous PCBs a decade ago. The current pipeline project connecting Russia with Germany also presents dangers as it will stir up sea-bed sediment, says Leppänen. What's hiding under that sediment is anybody's guess.

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