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Mercury is twice as pervasive in environment as previously thought


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(NaturalNews) There is more than twice as much mercury contaminating the environment as scientists had previously thought, according to a study conducted by researchers from Harvard University and the Argonne National Laboratory, and published in the journal Environmental Science & Technology on August 15.

According to the researchers, the study is the first time that anyone has quantified non-atmospheric forms of mercury pollution from sources such as mining or the manufacture and disposal of commercial products.

Mercury is a potent neurotoxin that has a tendency to accumulate in the oceans and, by extension, in aquatic food webs. Other than direct exposure via contaminated air or soil, one of the major sources of human mercury exposure is fish consumption.

Long-lasting contamination

Mercury has been mined and used by human beings since ancient times, but its use expanded dramatically with the Industrial Revolution. Studies have shown that background levels of mercury in the environment are now approximately five to 10 times higher than natural levels, and about three times higher than they were in pre-industrial times.

Without human interference, mercury tends to be found beneath the earth, and it is typically brought to the surface by natural geological processes or human mining. Once present on the surface, mercury is able to move relatively rapidly between the atmosphere, the soil and the surface of the ocean, on a timescale of years to decades. Once emitted into the atmosphere, mercury tends to remain there for about a year, allowing it to travel to any part of the planet before settling into soil or water. As a general rule, however, mercury tends to settle in the lowest point, typically the oceans.

This means that, over the short term, most mercury pollution end up in the oceans, contaminating fish. It takes hundreds of years for mercury to settle into deep ocean pools or long-lived soil reservoirs and therefore stop being available for uptake by living creatures. Once emitted into the surface environment, mercury will not return to its stable location beneath the surface for thousands of years.

This means that, even though commercial mercury use has been declining since the 1970s, the contamination produced prior to that will remain with us for the foreseeable future.

Most mercury not in landfills

Prior estimates of global mercury contamination have been based almost exclusively on atmospheric mercury emission as a byproduct of processes such as fossil fuel combustion, metals smelting, mining and chlor-alkali production. These estimates therefore ignored nearly all deliberate industrial and consumer uses of mercury.

Yet such mercury can enter the environment in many forms, including the deliberate dumping of mercury historically practiced by chemical companies (causing contamination of estuaries that endures today); the spraying of mercury-containing fungicides, herbicides and insecticides; the incineration or landfill disposal of mercury-containing batteries; and even the evaporation of fumes from mercury-containing paint.

In the new study, the researchers estimated the release of mercury from commercial sources between 1850 in 2010. They found that, in contrast to the 215 billion grams (Gg) of mercury that was expelled directly into the atmosphere in that time, an astonishing 616 Gg was mined for commercial uses.

Of this 616 Gg, the researchers estimated that nearly all of it (540 Gg) has already entered the environment as contamination: 20 percent of it into the air, 20 percent into landfills, 30 percent into soil and 30 percent into water. Because some of this pollution has been effectively trapped in landfills or has already been sequestered in the sediment at the bottom of lakes and seas, the amount of environmentally cycling mercury from these sources is actually 310 Gg.

That means that total global levels of mercury contamination are actually 525 Gg, more than twice the 215 Gg previously estimated.

Sources for this article include:


http://acmg.seas.harvard.edu [PDF]


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