Polar Ice Crystals Aid Mercury Deposition - Then What?

A research team headed by Prof. Joel Blum of the University of Michigan studied how ice crystals formed by rising sea vapors captured almost all of the airborne mercury each polar spring. How the crystals performed their collection and which crystal types were best at it formed the basis of some very interesting research. Aided in his study by others from the Cold Regions Research & Engineering Laboratory and the University of Alaska, Professor Blum hopes to take the study into the next phase where they study the snow melt and its effect on mercury accumulation in the tundra. Look for their full results in the cover article of the March 1, 2008 issue of Environmental Science & Technology, whose lead author is Thomas Douglas of the CRR&EL. A preview excerpt from an article on PhysOrg.com follows;

"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 analyzed a few snow samples and found very high levels of mercury," said Joel Blum, the John D. MacArthur Professor of Geological Sciences at U-M. "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."
[...]
"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 industrialized location."
[...]
Blum and co-workers discovered that certain types of ice crystals—frost flowers and rime ice—contained the highest concentrations of mercury. Because both types of crystal grow directly by water vapor accretion, the scientists reasoned that breaks in the sea ice, where water vapor rises in great clouds, contribute to Arctic mercury deposition.

"The vapor that rises through these openings in the ice brings with it bromine from the sea water. That gets into the atmosphere, where sunlight plus the bromine cause a catalytic reaction which converts mercury gas into a reactive form. If any ice crystals are present, the mercury sticks to them and comes out of the atmosphere," Blum said.

The greater the surface area of the crystals, the more mercury they grab, which explains why frost flowers and rime ice, both delicate formations with high surface areas, end up with so much mercury. The mercury-tainted crystals aren't, however, confined to the edges of breaks in the ice, the researchers determined. Bromine can travel great distances, resulting in mercury deposition in snow throughout the Arctic coastal region.
[...]
"Research like this will help to further the understanding of mercury deposition to a region that is generally considered pristine," he said. "In the next phase of our work, we are expanding our knowledge by tracking the mercury during and following snow melt and studying its accumulation on the tundra."

In addition to Blum and Douglas, the paper's authors are Matthew Sturm of the Cold Regions Research & Engineering Laboratory in Fort Wainwright, Alaska; William R. Simpson and Laura Alvarez-Aviles of the University of Alaska, Fairbanks; Gerald Keeler, director of the U-M Air Quality Laboratory; Donald Perovich of the Cold Regions Research & Engineering Laboratory in Hanover, N.H.; U-M post-doctoral fellow Abir Biswas and U-M graduate student Kelsey Johnson.

The full article which goes into some interesting detail of how hard it is to perform research and capture representative samples in the freezing temperatures can be found here. I look forward to seeing what they uncover in phase two.