Mercury of centuries ago threatens the Arctic Ocean

The ocean currents They are the transporter of the mercury up to the waters of the Arctic Ocean, where the pollutant threatens the health and survival of the apical predators and that of the indigenous communities that also feed on marine mammals.

A new research by two Danish universities explains why the reduction of global mercury emissions in the atmosphere, evident from the late 70s, it did not go hand in hand with a decrease in mercury in the arctic waters. The persistence times of mercury in the oceans have to do with it, and those used by currents to transport it to the north. The study was published on Nature Communications.

An important part of the mercury that contaminates the fish of the sea comes from the plants that use coal as fuel, especially (at least as regards Europe) from plants that burn coal to produce electricity, cement or metals. The combustion of wood, the paper mill and the incineration of waste also produce mercury emissions. In addition, the mercury has been and is still used, in a non -regulated and risky way, for the gold extraction in small scale mineral activities.

From the atmosphere, mercury is transported to soils and water, in particular in the muddy sediments of rivers and lakes where it is converted by bacteria and anaerobic microorganisms in Metilmercurio. This toxic compound accumulates in marine organisms and increases in concentration as it goes back to the subsequent levels of the food chain.

«We have monitoring mercury in Arctic animals for over forty years. Despite the decline in global emissions since the 70s, we have not observed a corresponding decrease in arctic concentrations, quite the contrary, “explains Rune Dietz, professor of the Department of Ecojacker and Research on Marine Animals of the University of Aarhus (Denmark). This is because the mercury, which released into the atmosphere remains available and transportable for about a year, once in the water 300 years can persist.

The global efforts to reduce mercury pollution culminating with the Minamata convention, an international treaty approved in 2013 and entered into force in 2017, led to a 70% reduction in the level of mercury in the atmosphere of the last 20 years. However, given the resistance of the toxic form of mercury in ocean waters, the Arctic environments are intended for remain contaminated so long for a long time.

The scientists of the universities of Aarhus and Copenhagen have analyzed about 700 environmental champions taken over the past 40 years in the Arctic environment, such as fabrics of polar bears and seals, parts of fish and peat pieces.

Have identified Six Municipalities of Mercury Isotopi (i.e. variants of the element with the same number of protons in the nucleus, but a different number of neutrons) and used them for trace to the origin of that inquiring and the way he had been transported to the Arctic.

For example, they realized that the mercury detected in western Greenland had reached the current of Irmerger, an oceanic current of the Atlantic that flows towards the west, bringing warmer waters along the northern coast of Iceland. While the transport of mercury in the other regions was entrusted to Arctic currents.

For Dietz “the transport of mercury from the main sources such as China to Greenland through ocean currents can require up to 150 years and this helps to explain the lack of decline in mercury levels in the Arctic”.

Mercury is one neurotoxin which has effects on the nervous system, on sensory perceptions, reproductive skills and the immune system of marine animals. In apical predators, such as polar bears and orche in the Arctic, it is now present In concentrations 20-30 times higher compared to the pre -industrial era. With effects both on their survival skills, and on those of human communities that depend on these animals for their livelihood.