INSIDE grooves of Atacama, which It stretches for about 6,000 kilometers along the coast of South America, scientists discovered polychlorinated biphenyls (PCBs). This substance was produced in large quantities from the 1930s to the 1970s, especially in the northern hemisphere. It has been used in electrical equipment, paints, refrigerants, and many other products.

they are still here

In the 1960s PCBs were recognized as harmful to marine life, and by the mid-1970s their use almost led to a global ban. However, since PCBs take decades to break down, and they can travel long distances and spread. in places far from where they were first used. Pollutants continue to circulate by ocean currents, winds and rivers.

PCBs do not dissolve well in water and instead attach to the tissues of living or dead organisms, such as plankton, which are tiny organisms at the beginning of the food chain. When plankton dies, their cells sink to the bottom, carrying contaminants with them.

Because seafloor sediments contain many dead plant and animal remains, they serve as an important sink. At a maximum depth just below the Himalayas, Atacama acts as a kind of funnel, collecting dead plant and animal fragments (what scientists call “organic carbon”) that fall into the water. According to scientists, About 60% of PCBs discarded in the 20th century are stored in deep-sea ocean sediments.

Microbes break down organic carbon in seafloor mud. It was also found that organic carbon decomposes more strongly in the deepest parts of the Atacama Trench than in shallow waters. Higher PCB concentrations per gram of organic carbon in the residue were also observed at the greatest depths. Conservation of pollutants means ocean sediments can be used to look into the past. It is possible to detect when a sediment layer has accumulated on the seafloor, and by analyzing pollutants in different layers we can gain insight into their concentration over time.

The most interesting thing for scientists, PCB concentrations were highest in surface sediments, but the reverse must be true. If humanity banned the use of this pollutant In the 1970s, then sediments should have contained more in past stratifications and minimal in current stratifications, as observed today. lakes and seas. However, in Everything is different in the Atacama Basin.