Environment

Mercury atmospheric pollution back to the ground!

Thousands of tons of mercury are released into the atmosphere each year. Is this element so toxic to humans? It would be transformed into an oxidized form at the top of the atmosphere. After returning to the ground, transformed mercury can then integrate ecosystem water and accumulate along the food chain. In short, it is polluting our health.

Several thousand tonnes of mercury are released into the atmosphere each year. Incineration of waste is also involved in this phenomenon. © Swanksalot, Flickr, CC by-sa 2.0

Mercury is extremely toxic to human health and for all living organisms. This heavy metal causes, among other neurological diseases, renal disturbances or decreased fertility. Yet it is widely used in metallurgical industry and for the production of chlorine and electricity. Thousands of tons of mercury are freed into the atmosphere each year. Inhaled, it is just as toxic when ingested. So what happens to all that mercury?

Seth N. Lyman and Daniel A. Jaffe, from University of Washington Bothell, provide some answers in an article in Nature Geoscience. The researchers traveled the U.S. and European skies in an airplane from the National Center for Atmospheric Research to measure the various forms of mercury in the atmosphere: pure and oxide mercury . Data were collected in the troposphere, between 6,000 and 7,000 meters, with a measuring device developed for this occasion. The aircraft had a chance to move in air currents coming down from the stratosphere, collecting data on the area higher in the atmosphere.

Pure mercury is transformed into oxidized mercury at the top of the atmosphere. The top of the troposphere and the lower stratosphere would act as real chemical reactors promoting the transformation of pure mercury (Hg) in its oxidized form (Hg 2 + ). The measurements have shown a low stratosphere pure element. At present, the various stages of this transformation are not yet known.

The Arctic as a source of oxidized mercury

Mercury is a liquid metal highly toxic to humans and living organisms. It is present in the atmosphere as fine droplets that can be inhaled. © Valentino Tombesi, Flickr, CC by nc-nd 2.0

The sky in the Arctic is home to the largest concentration of oxidized mercury. Weather conditions in spring and summer would be the cause according to researchers at the Norwegian University of Science and Technology. Large amounts of oxidized mercury were also measured in the atmosphere above the Dead Sea. No explanation can be given at present to justify these results.

Rain or movement of air masses encourage a return of the oxidized mercury to the ground, especially to aquatic ecosystems. Once in the water, earlier studies have shown that this compound could undergo the action bacteria. It is then transformed into methylmercury, an organic molecule of the most toxic. Mercury can therefore enter the food chain and accumulate in organisms belonging to different trophic levels.

Thus, the mercury released into the atmosphere can be inhaled directly to contaminate us or end up in our food after going into the stratosphere. The system is very vicious because the return of mercury in aquatic ecosystems may take some time and take place thousands of miles from the pollution source.

Source for further read: EVISA published 20-Dec-2011

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