Humans pump thousands of tons of vapor from the metallic element mercury into the atmosphere each year, and it can remain suspended for long periods before being changed into a form that is easily removed from the atmosphere.
New research shows that the upper troposphere and lower stratosphere work to transform elemental mercury into oxidized mercury, which can easily be deposited into aquatic ecosystems and ultimately enter the food chain.
"The upper atmosphere is acting as a chemical reactor to make the mercury more able to be deposited to ecosystems," said Seth Lyman, who did the work as a research assistant professor in science and technology at the University of Washington Bothell.
Lyman, now with Utah State University's Energy Dynamics Laboratory, is lead author of a paper documenting the research published online Dec. 19 by the journal Nature Geoscience. Daniel Jaffe, a science and technology professor at UW Bothell, is coauthor of the paper. The work was supported by a grant from the National Science Foundation.
The findings come from data gathered during research flights in October and November 2010 over North America and Europe by a National Center for Atmospheric Research aircraft.
The campaign used a device built at UW Bothell that can detect both elemental mercury and oxidized mercury in the same air sample, and the device recorded readings every 2.5 minutes. The flights typically are at altitudes of 19,000 to 23,000 feet, well below the confluence of the troposphere and the stratosphere, but several times during the 2010 flights particularly on a trip from Bangor, Maine, to Broomfield, Colo. the aircraft encountered streams of air that had descended from the stratosphere or from near it.
The result was the first time that the two mercury forms were measured together in a way that showed that elemental mercury is transformed into oxidized mercury, Lyman said, and evidence indicat
|Contact: Vince Stricherz|
University of Washington