Researchers from Sweden and Denmark analyzed sediments from different depths in the Atacama Trench -
Previous studies have shown that thesechemicals are found in high concentrations in the Baltic and North Seas and Tokyo Bay. But these areas are not very deep and are relatively close to industrial centers and large agglomerations in Europe and Japan. Although these substances are found in lower concentrations at the bottom of the Atacama Trench, the very fact that they are there is surprising, scientists say.
The environment of the deep sea basin is unique.It serves as a sink for dead organic material, both from the water column and from landslides on the seafloor. Researchers believe that a lot of organic carbon, consisting of dead plankton, accumulates in the deep-sea basin, and an active microbial community develops, decomposing organic material. At the same time, the eternal chemicals remain stable, and their concentration gradually increases.
The Atakama Trench is located in an area withrelatively high productivity of plankton in surface waters. When it dies, the organic material is carried into the sediment. As plankton and other organic materials sink to the bottom, they carry pollutants that bind to lipids and organic carbon.
Anna Sobek, Professor of Environmental Chemistry at Stockholm University and study co-author
Many pollutants arelong-lived: they are called "eternal chemicals" because they are extremely difficult to destroy. Under natural conditions, they are practically not destroyed. PCBs are one class of such substances. They were widely used in a wide variety of industries from the 1930s to the 1970s, including as heat transfer fluids, dielectrics, and coolants.
PCBs are classified as persistent organicpollutants dangerous to humans and the environment. Their production has been banned since the mid-1970s, but due to their long life cycle they are still present and circulating in the environment.
Researchers believe that the accumulation of suchsubstances in deep waters can have a devastating effect on local ecosystems. They plan to study the uptake of "timeless chemicals" by benthic animals to try to understand how these pollutants spread and affect food chains.
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On the cover: the device with which the samples were obtained. Photo: Anni Glud/SDU