The mercury puzzle

mercuryinsoilSometimes the more you learn, the more you realize you have to learn. That seems to be the case with those hardy folks doing research on mercury in the environment. It’s a bowl of challenges that just keeps getting refilled.

Early this year, the mercury research team at Oak Ridge National Laboratory came out with a big announcement (published in Science), identifying two genes in microorganisms that are responsible for the environmental process that converts some forms of mercury into the most toxic form — methylmercury. The breakthrough was important, at least partly clarifying something that had evaded scientists for years, and it seemed to shine a positive light, offering hope that the discovery would make the environmental cleanup easier.

More recently, the lab has issued a couple of press releases that seemed to underscore just how difficult the mercury problem is.

Last week, ORNL released results — also published in Environmental Science and Technology — that showed more there are even more methlymercury-generating bacteria out there than previously thought and in some unexpected environments.

Indeed, the lab said that researcher Dwanye Elias and his colleagues are “testing a bacterium from the human intestine that they predict will also methylate mercury.” That doesn’t exactly put a smile on your face.

Last month, in a study published in Nature Geoscience, researchers similarly reported that more forms of mercury can be converted to methylmercury than previously thought.

“Most mercury researchers have believed that microbes could not convert elemental mercury — which is volatile and relatively inert — into methylmercury,” the laboratory said in a release. “Instead of becoming more toxic, they reasoned that element mercury would bubble out of water and dissipate. That offered a solution for oxidized mercury, which dissolves in water. By converting oxidized mercury into elemental mercury, they hoped to eliminate the threat of methylmercury contamination in water systems.”

However, in studies by ORNL and Rutgers University, the results indicated that elemental mercury is also susceptible to being changed by bacteria in the environment.

“Communities of microorganisms can work together in environments that lack oxygen to convert elemental mercury to methylmercury,” researcher Baohua Gu said in a statement released by ORNL.

Photo caption: Soil sample taken from contaminated area at the Y-12 nuclear weapons plant contains globules of mercury leftover from the plant’s Cold War work on thermonuclear weapons. (ORNL photo)


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About Frank Munger

Senior Writer Frank Munger covers the Dept. of Energy's Oak Ridge facilities and many related topics — nuclear weapons, nuclear waste and other things nuclear, environmental cleanup and science of all sorts. Atomic City Underground is, first and foremost, a news blog, but there's room for analysis, opinion and random thoughts that have no place else to go.