July 25, 2011

Arctic Melt Releases Toxic Pollutants

Toxic chemicals that have been trapped in Arctic ice and snow are now being released due to global warming, according to a study published on Sunday.

Researchers warn that the amount of poisons in the polar region is unknown and the release of large amounts of such poisons could "undermine global efforts to reduce environmental and human exposure to them."

Those chemicals include the pesticides DDT, lindane and chlordane; and industrial chemicals PCBs and HCB. All of these are known as persistent organic pollutants (POPs) -- now known as the "Dirty Dozen" -- and have been banned under the 2004 Stockholm convention.

The "Dirty Dozen" were widely used as insecticides and pesticides prior to 2001. They are extremely tough molecules that take decades to decompose in nature. They are also known to bio-accumulate, meaning that as they pass up the food chain, concentrations rise, posing threats to fertility in higher up species. The "Dirty Dozen" can also cause cancers and birth defects.

Plus, they are insoluble in water and can swiftly transit from soil and water to the atmosphere in response to increased temperatures.

Over the past, the low temperatures in the Arctic trapped the volatile chemicals. But scientists working from Canada and Norway have discovered that global warming is freeing those chemicals again. The researchers examined measurements of the poisons in the air between 1993 and 2009 at the Zeppelin research station in Svalbard and Alert weather station in northern Canada.

The researchers concentrated their study on three chemicals -- DDT, HCH and cis-chlordane. They found a long-term downward trend in primary emissions after the Stockholm Convention banned production and trade of the "Dirty Dozen."

But the researchers uncovered a disturbing scenario when the same data was crunched through a simulation of the effect of global warming on POP concentrations.

Their study found a slight rise in secondary emissions, from chemicals that had been locked in the Arctic ice and snow but were now being gradually released due to warming.

"A wide range of POPs have been remobilized into the Arctic atmosphere over the past two decades as a result of climate change," said the study, led by Jianmin Ma of the agency Environment Canada in Toronto.

Arctic warming "could undermine global efforts to reduce environmental and human exposure to these toxic chemicals," the study warned.

Hayley Hung, at the air quality research division of Environment Canada and one of the team, told the Guardian that the work was provided the first evidence of remobilization of the chemicals in the Arctic.

"But this is the beginning of the story," she said. "The next step is to find out how much is in the Arctic, how much will leak out and how quickly."

Pollution specialist Jordi Dachs of the Institute of Environmental Assessment and Water Research in Barcelona, Spain, said this news was grim.

"It seems likely that persistent pollutants will affect the environment on even longer timescales than currently assumed," Dachs told the AFP news agency. "The remobilization of pollutants generated by our grandparents... are unwanted witnesses to our environmental past that now seem to be "Ëœcoming in from the cold.'"

The study is published in the scientific journal Nature Climate Change.


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