December 21, 2013
Russian Arctic Rivers Appear To Have Low Or Declining Mercury
April Flowers for redOrbit.com - Your Universe Online
Researchers have assumed for years that high and increasing levels of mercury in the North American and European Arctic means the same is true of fish elsewhere in the Arctic. A team of researchers from the US, Russia, and Canada, however, has discovered that in much of the continental Arctic, that assumption is misguided.
According to a United Nations Environmental Program study, atmospheric mercury comes largely from mining and ore processing, such as smelting. Mercury is converted to a special form under certain water conditions that can be absorbed by living organisms, through a process called methylation. "Methylmercury is highly toxic," added Castello.
Despite this, the research team determined burbot fish in two Russian rivers, the Lena and the Mezen, are safe to eat.
Burbot fish from 20 locations along the Pasvik River on the Norwegian-Russian border and along the Mackenzie River in Canada – where decades of studies have found high levels of mercury that make the fish unsafe for consumption — were compared to burbot from the Lena and Mezen.
Found throughout the Arctic, burbot are cod-like fresh water fish that are long-lived, eat other fish, and are non-migratory.
"The burbot fish was chosen because they are top predators that integrate many bio-geo-chemical processes in the river watersheds," said Castello. "The fish were collected downstream of the watersheds, so that they would present everything that happened upstream."
Alexander V. Zhulidov of the South Russian Centre for Preparation and Implementation of International Projects sampled the fish using an ice-fishing method during November and December—peak burbot season.
"We developed and led an initiative of biological monitoring of the water quality of major rivers of Russia in 1980 and continued to do it until 2001, because we knew it could provide useful information one day. In 2002 the funding was cut and the program was closed. Unfortunately we have no funding to continue collecting such interesting data," said Zhulidov.
In the Mezen River, mercury concentrations were lower than 10 locations, but higher than eight others in North America. In the Lena River, however, mercury levels were among the lowest.
"Good news since the Lena River is one of the largest watersheds in the world," said Castello.
What makes the difference between rivers? The authors said, "There are no ancillary environmental data from the time period of the study in Russia," but they suggest the differences across the Arctic "may be explained by differences in water quality, geological bedrock formations, and proximity to polluting sources."
Atmospheric mercury was on the rise until the 1970s as a result of industry in Europe and in North America. It began to decline from those sources due to emission controls, the authors explain, with Asia coming on line as a source.
Metallurgic industries in the Murmansk region of Russia, along with smelter companies in the Pasvik watershed, explain high levels of atmospheric mercury in the Pasvik River. Polluting activities were lowered when the economic decline affected areas near the watersheds of the Lena and Mezen.
Robert Spencer, an associate scientist at the Woods Hole Research Center, said a confounding factor has been climate change. Mercury concentrations in fish tissue in the Canadian Arctic have increased despite declining atmospheric concentrations because rising temperatures appear to increase availability of mercury to fish populations.
"More studies are needed in the Russian Arctic if we are to better understand how mercury moves through this type of environment," Castello said.
Their findings were published in the journal Environmental Science & Technology.