Her research is supported by the National Institute of Environmental Health Science.
In the past, most of the scientific studies of effects of mercury in the environment have focused on freshwater, because the technology had not advanced to the point where scientists could accurately measure the smaller concentrations of mercury found in seawater. Though the concentrations may be smaller in seawater, mercury accumulates more readily in the tissues of organisms that consume it.
"Because sunlight does not break it down in seawater, the lifetime of methlymercury is much longer in the marine environment," Hsu-Kim said. "However, the Food and Drug Administration and the Environmental Protection Agency do not distinguish between freshwater and seawater."
Mercury enters the environment through many routes, but the primary sources are coal combustion, the refinement of gold and other non-ferrous metals, and volcanic eruptions. The air-borne mercury from these sources eventually lands on lakes or oceans and can remain in the water or sediments.
The key to the sun's ability to break down methylmercury is a class of chemicals known as reactive oxygen species. These forms of oxygen are the biochemical equivalent of the bull in the china shop because of the way they break chemical bonds. One way these reactive oxygens are formed is by sunlight acting on oxygen molecules in the water.
"These reactive forms of oxygen are much more efficient in breaking the bonds within the methylmercury molecule," Hsu-Kim said. "And if the methylmercury is bonded to organic matter instead of chloride, then the break down reaction is much faster."
|Contact: Richard Merritt|