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An international team of researchers from the United States, Canada, and Russia, has surprised the scientific community in overturning previous assumptions that high mercury levels in the North American and European Arctic meant those same levels would be found everywhere near the top of the world. The team discovered that mercury concentrations in fish are much lower than expected in much of the continental Arctic and that the economic decline of the former Soviet Union may be responsible.
“It turns out that the economic decline of the former Soviet Union, which collapsed in 1991, appears to have been good for that part of the Arctic environment in that part of the world,” Leandro Castello, assistant professor of fish and wildlife in the College of Natural Resources and Environment at Virginia Tech, said in a statement. He is lead author of a study published in the Dec. 20 issue of Environmental Science & Technology, a journal of the American Chemical Society.
Most atmospheric mercury comes from mining and ore processing, according to a United Nations Environmental Program study. Under certain water conditions, mercury is converted to a special form that can be absorbed by living organisms–like fish–through a process called methylation.
Since the Industrial Revolution, atmospheric mercury continued to increase in Europe and North America until the 1970s. It began to decline as a result of emissions controls, according to the researchers, with Asia now leading the world in atmospheric mercury levels.
The scientists compared mercury levels in burbot fish from 20 locations along the Pasvik River on the Norwegian-Russian border and along the Mackenzie River in Canada, where long-term studies have found dangerously high levels of mercury, making its fish unsafe for human consumption. Burbot fish, found throughout the Arctic, are cod-like, non-migratory, freshwater predators.
“The burbot fish was chosen because they are top predators that integrate many bio-geo-chemical processes in the river watersheds,” Castello said. “The fish were collected downstream of the watersheds, so that they would present everything that happened upstream.”
The team found that burbot fish in two Russian rivers, the Lena and the Mezen, were safe to eat. Mercury concentrations from fish in the Mezen were lower than in 10 other locations, but higher than eight in North America. But mercury levels in burbot from the Lena River were among the lowest of all. Castello calls this “good news,” because the Lena River is “one of the largest watersheds in the world.”
According to the researchers, metallurgic industries in the Murmansk region of Russia and smelting operations in the Pasvik watershed explain high levels of atmospheric mercury in the Pasvik River. On the other hand, the decline in economic activity leading up to and after the dissolution of the Soviet Union, along with the concomitant reduction of pollution sources near the watersheds of the Lena and Mezen, accounts for the low levels of mercury found there.
“More studies are needed in the Russian Arctic if we are to better understand how mercury moves through this type of environment,” Castello added.