Wastes from human activities are poisoning the atmosphere, soil, rivers and seas. Are there any uncontaminated corners of the world? If anyone thinks that the bottomless depths, where even sunlight can’t reach, might still be free of filth, they’re wrong. A team of scientists has found PCBs (polychlorinated biphenyls) in the sediments of a distant ocean trench more than 8,000 meters deep.. is carcinogenic.
The study, recently published in Nature Communications, reveals that there are traces of these toxic organofloral compounds in plants. Atacama TrenchIt is the largest in the world, stretching for 5,900 kilometers off the coasts of Peru and Chile in the Pacific Ocean.
The researchers took samples at different depths and found traces of PCBs in all of them. 8,085 meters below sea level.
“The Atacama Trench is located in a region with relatively high plankton productivity in surface waters, which leads to the transport of organic material to sediment when plankton die,” explains Anna Sobek, lead author of the study.
“When plankton and other organic matter sink to the bottom, carry pollutants This tends to bind to lipids and organic carbon,” says Sobek.
Many pollutants have a very long life: takes a long time to decompose in the environment. This also means that they can be transported long distances and spread far from where they were used and dropped.
PCBs are one of these long-lasting contaminants. It has been used in large numbers since the 1930s and was banned worldwide by the mid-1970s.. Despite this, they still exist and roam the planet.
dead organic matter sink
“The setting in a deep-sea trench is unique. The trench is a dead organic matter sinkboth from the water column and from landslides on the seafloor,” say the study’s authors.
“In conclusion, a large amount of organic carbon accumulates In the deepest part of the sea trench, predominantly dead plankton and active microbial community decomposes organic material,” they elaborate.
“In our study, we found that sediment in the deepest parts of the Atacama Trench had a lower percentage of readily degradable organic carbon,” the scientists said.
“We also saw that it was there. higher concentrations of PCBs per gram of organic carbon in deeper sediments of the trench. This is because, the organic carbon in the residue degrades, but the longer-lived PCBs remain. and therefore it can accumulate,” says Sobek.
However, the authors acknowledge that: PCB concentration in samples from the Atacama Trench is not alarmingly high. According to Professor Ronnie N. Glud, director of the Danish Hadal Research Center at the University of Southern Denmark and one of the authors behind the study, “Much higher” concentrations have been found in places like the Baltic Sea, the North Sea or Tokyo Bay..
“These are places where there is a lot of human activity so the result was expected. Atacama samples do not show very high concentrations, but are relatively high considering they were extracted from the bottom of a deep water trench. No one would expect to find contaminants in a place like this.Glud says.
pollutants in deep-sea animals
There is not much data currently available on pollutants in deep sea trenches. Two previous studies had shown surprisingly high concentrations of PCBs and similar contaminants in marine sediment-dwelling animals..
“In future studies, we will also we will study absorption in animals bottom-dwelling to try to understand how pollutants spread. How can they affect the food web in the ocean trenches,” Sobek announces.
Another aim of this group of scientists, who will make new analyzes soon, is japan trenchto examine how microbial community in abyssal trenches It can contribute to the degradation of some pollutants.
In the Japan Trench, the researchers will measure environmental pollutants at a depth of 100 meters. up to 9,000 meterssomething that has never been done before.
Effects associated with exposure to high levels of polychlorinated biphenyls include: skin problems (acne and rashes) already in adultsNeurological and immunological changes in children. It is also known that causes different types of cancer in animals. Some studies on workers have been associated with exposure to PCBs. liver and biliary tract cancer.
Because they are fire resistant and highly insulating, PCBs are widely used as coolants and lubricants in transformers, capacitors and other electrical items, as well as sealants, inks, carbon paper and paint additives. They can easily circulate between air, water and soil.
Materials made before these contaminants expire, such as old fluorescent tubes, electrical equipment, or parts with capacitors, and old microscope oil and hydraulic oil may still contain PCBs. There are no known natural sources of PCBs..
Reference work: https://www.nature.com/articles/s41467-023-37718-
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