Study probes airborne mercury’s effects

METAALICUS is a multi-million-dollar mercury manipulation study being planned for the Experimental Lakes Area in Northwest Ontario. The “Mercury Experiment to Assess Atmospheric Loading in Canada and the U.S.”—an international collaboration between the United States and Canada partly supported by DOE—is designed to answer a central question: Are atmospheric emissions of mercury largely responsible for the methylmercury contamination of fish in lakes located far from industrial sources of mercury?

The Experimental Lakes Area has hundreds of remote lakes that can be safely used for environmental experiments; in fact, it was the site of pioneering lake acidification studies in the 1980s.

“We will use aircraft and manual sprayers to spray a different stable mercury isotope on a forest, a nearby lake, and a nearby wetland,” Corporate Fellow Lindberg says. “Using inductively coupled plasma mass spectrometry, a University of Toronto lab will analyze the degree to which mercury in the fish comes from the air, the lake and runoff from the forest and wetland.”

Although mercury is well recognized as a neurotoxin that is particularly harmful to prenatal life and infants, much has yet to be determined about how the element behaves in and affects the environment. Researchers are not at all certain that a reduction in atmospheric mercury emissions will reduce mercury concentrations in fish.

For that reason METAALICUS’s findings are important because regulations to control mercury emissions by industries will cost billions of dollars annually if implemented, even though their effectiveness is as yet unknown.

The findings are important to the United States’ and Canada’s fisheries as well. Most states have advisories against fish consumption because of high mercury concentrations, and in Canada unacceptable mercury concentrations exist throughout the country, including remote and otherwise pristine lakes in the Northwest Territories.

Very small amounts of three different stable isotopes of inorganic mercury will be added to the ecosystem under study. The isotope will enable the researchers to distinguish between what’s been added and background mercury that has accumulated over time. Production of methylmercury, which is the most toxic form of mercury in the environment, will be studied in lake sediments.

One possible source of the mercury isotopes for the study is the stockpile of stable mercury at ORNL, and preliminary tests that began last year are being done with ORNL isotopes.

The results of the study will be reported at the October 2001 International Conference on Mercury, which will be co-chaired by Lindberg. It will be held in Minamata City, Japan.

Minamata City is itself the site of a well-known mercury disaster that elicited considerable concern in the 1970s over mercury-contaminated waterways. From 1953 through 1965, an acetaldehyde factory discharged methylmercury and inorganic mercury into Minamata Bay.

The pollution killed 52 people. More than 1,200 became ill from eating bay fish contaminated with methylmercury. The disaster helped motivate the passage of the Clean Water Act of 1970.

“Since that time, most major sources of direct mercury discharges to waterways have been curtailed,” says Lindberg. “However, mercury continues to accumulate in remote lakes as a result of long-range atmospheric transport and deposition, and it is critical to understand the behavior of this mercury.”

Participating in the study with ORNL are representatives from Canadian agencies, several universities in Canada and the United States, Maryland’s Academy of Natural Sciences, the U.S. Geological Survey and Tetra Tech, Inc. Funders include DOE, the Environmental Protection Agency, the USGS, the Wisconsin Department of Natural Resources, the Electric Power Research Institute, and Canada’s Department of Fisheries and Oceans and National Sciences Engineering and Research Council. —Reported by Carolyn Krause