Scientists are sounding the alarm over unprecedented buildup of mercury in Pacific Ocean trenches

PICTURE: On board the German research vessel Sonne off the coast of Chile, ready to take samples at a depth of 8 kilometers within the view of the Atacama trench system After

Credit: Anni Glud, SDU

A scientific article recently published in Nature Publishing’s Scientific reports The newspaper found unprecedented amounts of highly toxic mercury being deposited in the deepest trenches in the Pacific Ocean.

The study, a multinational effort involving scientists from Denmark, Canada, Germany and Japan, reports the first-ever direct measurements of mercury deposition in one of the most logistically difficult environments to sample on Earth , and the deepest at 8 to 10 kilometers. under the sea.

Lead author Prof Hamed Sanei, director of the Lithospheric Organic Carbon (LOC) Laboratory at the Department of Geosciences at Aarhus University, said the amount of mercury found in this area exceeds any value ever recorded in the distant marine sediment, and is even higher than many areas directly contaminated by industrial discharges.

“The bad news is that these high levels of mercury may be representative of the collective increase in anthropogenic Hg emissions in our oceans,” he said. “But the good news is that ocean trenches act as a permanent dump, so we can expect the mercury in them to be buried for several million years. Plate tectonics will carry these sediments deep within. the upper mantle of the earth “.

“But even though mercury is being removed from the biosphere, the amount of mercury that has ended up in ocean trenches is still quite alarming. It can be an indicator of the overall health of our oceans.”

Co-author Dr Peter Outridge, Research Scientist at Natural Resources Canada and lead author of the United Nations Global Mercury Assessment, said: “The results of this research help fill a key knowledge gap in the cycle. mercury, that is to say the real rate. removal of mercury from the global environment in deep seabed sediments. He added: “We have shown that sediments in ocean trenches are ‘hot spots’ of mercury accumulation, with mercury accumulation rates several times higher than previously thought.”

Co-author Ronnie Glud, professor and director of the Hadal Center at the University of Southern Denmark, who was the chief scientist on this multinational ocean trench expedition, said: “This paper calls for an extensive additional sampling of large seabed, and in particular the hadal trenches to support this preliminary work, ultimately this will improve the accuracy of environmental mercury models and the management of global mercury pollution.

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