Scientists have made direct measurements of mercury deposition for the first time in the world's most difficult to access region.
The authors examined two deep-sea trenchesin different parts of the Pacific Ocean: Kermadec in the east and Atacama in the west, off the coast of Chile. They took samples from the deepest parts of the trench: it is from two to six kilometers deep.
The results revealed that the mercury concentrationat this depth was the greatest ever recorded in marine sediments - even higher than in many areas of industrial pollution.
The bad news is that suchhigh mercury levels may be representative of a general increase in anthropogenic mercury emissions to the ocean. But the good news is that ocean trenches act as permanent recycling sites. We can expect that the mercury that ends up there will be buried for many millions of years, with plate tectonics transporting it into the Earth's upper mantle.
Hameda Sanei, Director of the Laboratory of Lithospheric Organic Carbon, Faculty of Geosciences
But even though mercury is removed from the biosphere through troughs, scientists are concerned about how much toxic metal ended up there.
The authors believe that the results of their study will help fill a key knowledge gap about the mercury cycle on the Earth's surface.
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