arctic mercury and Inuits
schaffer at optonline.net
Mon Sep 3 08:41:20 MDT 2001
Mercury falling into food chain
Sun, sea and snow bring mercury down to Earth.
31 August 2001
Mercury rising: Inuits' levels are high.
Intense cold, sea spray and long dark winters are stripping toxic
mercury from the atmosphere and incorporating it in the fragile Arctic
food chain where it is accumulating, new research suggests.
The sudden burst of sunlight after long polar winters drives chemicals
in sea salt to react with normally inert mercury vapour in the air,
depositing it onto snow, Julia Lu and colleagues at the Meteorological
Service of Canada and Toronto report.
On melting, this snow injects a pulse of mercury into the Arctic
ecosystem at a time when it is most vulnerable to contamination - the
end of the winter, when most animals and plants are growing
fastest. "Just as the Arctic prepares for its two-month growing
season, the atmosphere throws down all this mercury," says Alexandra
Steffen, a member of the research team.
Fossil-fuel burning releases about 4,000 tonnes of mercury into the
atmosphere every year, mostly as vapour. Although toxic at high
concentrations, mercury vapour doesn't pass easily from the atmosphere
into the environment. Only oxidized mercury can enter ecosystems.
In the environment, oxidized mercury can be converted to methyl
mercury. This becomes concentrated as it passes through the food
chain. Levels are particularly high in Arctic fish and mammals and in
the Inuit people of North America who eat them. Large quantities of
mercury can cause dental problems, dementia and birth defects.
The springtime mercury pulse was first noticed a few years ago, but
the mechanism behind it was a mystery. "Nobody expected an atmospheric
chemical reaction like this," says Ralf Ebinghaus, an environmental
chemist at the Institute for Coastal Research in Geesthacht, Germany.
Lab studies are under way to establish the exact nature of the
mercury-deposition reaction. Other Canadian researchers are also
looking at whether the springtime mercury peak shows up in animal and
human populations. "We have no idea how long it takes for mercury to
accumulate to harmful levels in fish," says Ebinghaus.
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