Anni Glud, SDU
Scientists have discovered large amounts of very toxic metallic mercury, in the bottom sediments of the trenches of the Pacific Ocean floor.
Scientific Reports notes that this is the first time that scientists have been able to determine the content of mercury, which comes from human activity, in these sediments.
It is reported that in 2017, the Minamata Convention on Mercury entered into force. This agreement aims to protect the health of people and the surrounding environment from the influence of mercury and control the proportion of this toxic metal not only on land, but also in the oceans and seas, but until now all measurements and research have been conducted on land, especially in areas of direct industrial pollution.
Finally, researchers from Denmark, Canada, Germany and Japan on board the German scientific research vessel Sonne made direct measurements of the mercury content in the deposits at a depth of more than six kilometers. The researchers chose two deep trenches, the Kermadec in the east and the Atacama in the west, off the coast of Chile, with an average depth of 8-10 km. The researchers collected samples from the deepest points and from the surrounding areas, which are 2-6 kilometers deep.
And it became clear to the researchers, that the amount of mercury in the deep areas of the Pacific Ocean is much higher than what was previously recorded in marine sediments, and more than this, it is even higher than its content in many areas of industrial pollution.
Professor Hamid Sani, Director of the Organic Carbon Laboratory at the College of Earth Sciences, points out that these high levels of mercury may indicate high emissions of the metal from human activity in the ocean. On the other hand, deep ocean trenches seem to serve as a permanent burial of mercury. It can be said that the mercury present there will remain for millions of years, after which the tectonic plates will lift it to the upper mantle of the Earth.
The researchers believe that the results of this study will fill a major gap in the knowledge of the cycle of mercury on the Earth’s surface, because it shows how mercury is separated from the lithosphere.