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Toxic anthropogenic pollutants reach the deepest ocean on Earth
Summary
PCBs (toxic industrial chemicals) were found at extremely high concentrations in sediment from the deepest part of the Mariana Trench, far exceeding levels seen in shallower marine sediments. This confirms that persistent pollutants—and by implication microplastics—sink to and accumulate in the world's deepest ocean trenches.
Persistent organic pollutants (PCBs and PBDEs) were analysed in sediment core samples (0-2 cm) from the southern Mariana Trench at water depths of 7000-11000 m. PCBs concentrations ranged from 931 to 4195 pg/g, far higher than those recorded before in marine sediments from shallower depths. Toxic Equivalence (TEQ) of dl-PCBs ranged from 0.650 -14.9 pg/g, which is higher than most marine surficial sediments at <500-2500 m ocean depth, recovered from semi-industrial to industrial areas. However, 8 PBDEs values (averaging ~136 pg/g) were lower than those in surficial sediments from shelf areas recorded in past studies. Evidently, anthropogenic pollutants have reached the deepest realm on Earth, and the Mariana Trench acts as a repository for POPs amplification. The high concentration of PCBs is an eye-opener, which is directly affecting our deep sea ecosystems, considering their pervasiveness and persistence in trench sediments.
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