LOGAN — New research that culled atmospheric air samples shows that metallic mercury is transformed into oxidized mercury, which then can be easily deposited into aquatic ecosytems and enter the food chain.
The findings are from data gathered during research flights in 2010 over North America and Europe done by a National Center for Atmospheric Research aircraft.
Seth Lyman, now with Utah State University's Energy Dynamics Laboratory, was the lead author of the paper and did the research while at the University of Washington, Bothell.
"The upper atmosphere is acting as a chemical reactor to make the mercury more able to be deposited to ecosystems," Lyman said. Another professor at the university, Daniel Jaffe, was co-author of the paper, which was supported by a grant from the National Science Foundation.
The research, published online Monday in the journal Nature Geoscience, was gathered with a device built at the Washington university that can detect both kinds of mercury. It took readings every 2.5 minutes and was onboard an aircraft that encountered streams of air from the stratosphere or from near it.
Lyman said the result was the first time two mercury forms were measured together in a way that shows that metallic mercury is transformed into oxidized mercury, and evidence indicated the process occurs in the upper atmosphere.
Researchers do not yet know with certainty how the how the oxidation takes place, but once it happens it is quickly removed from the atmosphere through precipitation or air moving to the surface of the earth.
After mercury reaches the surface, bacteria transforms oxidized mercury into methyl mercury, a form that can be taken into the food chain and result in mercury-contaminated fish.
Mercury can be deposited thousands of miles from where it was emitted, Lyman said.
"Mercury emitted on the other side of the globe could be deposited right at our back door, depending on where and how it is transported, chemically transformed and deposited."