Public Release: 

'Mercury sunrise' phenomenon found in Antarctica

Pollution could enter food chain

American Chemical Society

In just five months during the spring each year, the northernmost coast of Alaska, a region that includes the Arctic National Wildlife Refuge, receives more than double the amount of mercury that falls on the northeastern United States in a year. New research now shows a similar phenomenon also occurs each year in the Antarctic -- the first time it's been reported in the South Polar Region.

Two studies in the March 15 issue of Environmental Science and Technology, a bi-monthly peer-reviewed journal of the American Chemical Society, the world's largest scientific society, present new information about the so-called "mercury sunrise" -- first reported in the Arctic in 1998.

When the sun rises and finally ends the long dark polar winter, it fires up a unique series of chemical reactions that dump mercury out of the atmosphere and into the pristine polar environments; hence the term, mercury sunrise. The mercury then accumulates in the snowpack and is released as the snow melts and the brief polar growing season begins.

The research indicates that atmospheric mercury rains down throughout the world's coastal polar regions and that when it does, it can enter polar food webs.

In one study, Ralf Ebinghaus, Ph.D., an environmental chemist at the Institute for Coastal Research in Geesthacht, Germany, reports the discovery of mercury sunrise at the German Neumayer research station in Antarctica based on measurements made between January 2000 and January 2001.

In the other study, Steve Lindberg, Ph.D., a research corporate fellow at the Oak Ridge National Laboratory in Tennessee presents the first evidence of how this phenomenon leads to elevated mercury accumulation in snow, as measured at the NOAA Climate Monitoring and Diagnostic Laboratory in Barrow, Alaska.

Canadian researchers working with Lindberg determined that some of the snowpack mercury is bioavailable and has the potential to be transformed by bacteria into a form that could enter the food web.

According to the Lindberg team, the new findings may help explain why mercury levels in Arctic seabirds, seals and beluga whales have increased over the last few decades, even though global atmospheric emissions of mercury have declined during the last 20 years.

The Alaska study also shows that some of the mercury has the potential to be transformed by bacteria, an indication that this mercury may enter polar food webs.

The mercury sunrise depends on ultraviolet light, open water and active sea ice, all of which have been increasing in Polar Regions over the last few decades. According to the Barrow data, the polar sunrise triggers a series of chemical reactions that convert the elemental mercury vapor into a highly soluble form of oxidized gaseous mercury that rapidly accumulates in the polar snowpack.

Fossil-fuel combustion releases about 6,500 tons of mercury into the atmosphere every year. This mercury vapor remains in the air, where it is carried to all parts of the globe, including the remote polar environments. Ebinghaus and Lindberg agree that mercury sunrises probably occur to some extent throughout polar coastal regions. They estimate that between 50 and 300 tons of mercury are being dumped from the atmosphere into these polar environments annually.

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The online versions of the research papers cited above were initially published February 13 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to newsroom@acs.org or calling the contact person for this release.

Steve E. Lindberg, Ph.D., is a Corporate Research Fellow in the Environmental Sciences Division at Oak Ridge National Laboratory in Tennessee

Ralf Ebinghaus, Ph.D., is an analytical and environmental chemist and head of the Department for Organic Trace Analysis at the Institute for Coastal Research in Geesthacht, Germany

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