Contamination Fears After Nord Stream Explosion – World War II Chemical Weapons Dump Site

There is great concern in the scientific community about possible serious contamination with chemicals after the explosion in the Nord Stream pipelines in the Baltic.

Researchers are scrambling to find out whether the explosions at the Nord Stream gas pipelines caused further environmental chaos by mixing pollutants from chemical weapons dumped at the site after World War II.

The September 26 pipeline explosions in the Baltic Sea occurred very close to the Danish island of Bornholm, an area where chemical weapons were dumped in 1947 as part of Germany’s postwar demilitarization.

About 32,000 tons of chemical weapons, containing about 11,000 tons of active chemical warfare agents, were dumped at the site, says Hans Sanderson, an environmental scientist at Aarhus University in Denmark. Over time, the metal casings of most of the discarded warheads have likely corroded, causing the contents to leach into the surrounding sediment. Sanderson is concerned that the violent release of methane from the ruptured pipeline may have significantly affected marine wildlife. Contaminants include the radioactive isotope cesium-137, toxic flame retardant chemicals called polybrominated diphenyl ethers and heavy metals including mercury, cadmium and lead.

“The Baltic Sea is basically one of the most heavily polluted seas on the planet. So this sediment here is full of garbage,” says Sanderson, who was involved in the environmental impact assessment when the Nord Stream pipelines were originally laid. “These explosions [επίσης] were made as close as possible to the dumping ground of these chemical weapons.’

Contaminated rocks directly affect water and marine life

When he saw images of released methane gushing over a wide area around the ruptured pipeline, “I realized there was a lot of sediment that’s going to go back into the water,” Sanderson says. “These sediments are very loose out there, so they’re fluffy and really mobile. Thus, many sediments can be resuspended.” His team is now using data from continuous monitoring in the area to model the extent of sediment dispersion caused by the eruptions. The team will then use toxicity thresholds for various marine species to investigate whether significant harm to marine life is likely to have occurred. The researchers also began taking seawater and sediment samples from the area to improve the accuracy of their models.

Any sediment that has been disturbed will remain suspended in seawater for a long time, Sanderson says. The Baltic Sea is relatively static, with no significant tides or currents. Furthermore, the temperature gradient in the water column means that the water is separated into layers that do not mix well. “This plume is not just going to settle down quickly again,” he says.

“I think there is cause for concern,” says Rodney Forster, a marine scientist at the University of Hull in the UK who has done a lot of work around the Baltic Sea. Given the size and scale of the methane leak, he says, “a lot of large amounts of sediment are going to be remobilized.”

Problem with fishing too

The Baltic Sea has been a key fishing spot for many years. Ferdinand Oberle, a geologist at the US Geological Survey’s Pacific Coastal and Marine Science Center in Santa Cruz, California, studied how bottom trawling has affected the sediment in this area. “Bottom trawling was often done in the area of ​​the World War II dump on Bornholm,” he says. Any sediment already suspended in the water by this activity could now be spread further by the eruptions, he adds.

The potential damage to wildlife may be mitigated by the timing of the eruption, says John Bothwell, a marine biochemist at Durham University, UK. “Marine life cycles usually start to close for the winter by mid-October,” he says. The blast site is in a cod spawning area, but spawning usually occurs in the spring. “But there’s still a lot that can be damaged: late algal blooms are not uncommon at this time of year and would have a negative impact if damaged,” adds Bothwell.

Forster says scientists based in countries bordering the region could provide useful data. “Germany, Sweden and Denmark all have good research ships in the area, surrounded by a fairly high concentration of scientific activity.” Any sediment carried up to the surface should be visible in satellite images, Forster says.

The results will take time to come, and Sanderson is eager to see what they show. “I’m concerned that this is very contaminated sediment,” he says, “and that this contaminated sediment will be bioavailable and therefore potentially cause problems.” “We just have to find out if that’s the case or not — and right now, I don’t really know.”

Nature

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