Scientists warn of high levels of mercury found in Arctic ice

by Rich Bowden - Feb 26 2008, 02:06

Scientists have found that samples of ice crystals taken from the Alaskan Arctic contain high levels of mercury, even when the mercury is not present in the surrounding atmosphere.

While naturally-occurring, large amounts of the element are spewed into the atmosphere from such industrial effluent such as chimneys and power plants. While it remains relatively benign in the air, once it settles on the ground, it is rapidly converted by bacteria into the toxic substance methylmercury and from there tends to work its way up the food chain.

However this was not expected to be such a problem in the Arctic where it was thought sunlight would break down mercury particles trapped in surface ice.

The theory though was disproved by research by scientists from the University of Michigan, the Cold Regions Research & Engineering Laboratory and the University of Alaska, who found large concentrations of mercury in ice crystals.

"Previous measurements had shown that in polar springtime, the normally steady levels of mercury in the atmosphere drop to near zero, and scientists studying this atmospheric phenomenon had analysed a few snow samples and found very high levels of mercury," said Joel Blum, the John D. MacArthur Professor of Geological Sciences at the University of Michigan in a statement.

"We wanted to understand what's controlling this mercury deposition, where it's occurring and whether mercury concentrations are related to the type and formation of snow and ice crystals."

The team found that ice that had been formed from vapour clouds billowing up from cracks in sea ice help concentrate mercury from the atmosphere, and that certain types of crystals they examined are more efficient in this process than others.

With rain as a major form of transfer of pollutants such as mercury from the atmosphere to the earth, Thomas Douglas of the Cold Regions Research & Engineering Laboratory in Fort Wainwright, Alaska said the increase in the element in the samples was not a surprise.

"Alaska receives air masses originating in Asia, and with China adding a new coal-fired power plant almost every week, it's not surprising that we find significant amounts of mercury there," Douglas said. "The concentrations we measured in some snow are far greater than would be found right next to a waste incinerator or power plant in an industrialised location."

Exposure to methylmercury in wildlife causes reproduction, growth, development and behaviour problems and even death. In humans the chemical causes "...damage to the central nervous system, heart and immune system," said the University of Michigan statement. "The developing brains of young and unborn children are especially vulnerable."

 

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