June 18, 2009

More mercury found in Mackenzie River

Scientists say they've found a much higher level of mercury flowing from Canada's Mackenzie River into the Arctic Ocean than found by previous studies.

University of Alberta researcher Jennifer Graydon and her colleagues analyzed water in the Mackenzie River as it flowed north into the Beaufort Sea. She collected samples for three months and discovered the total amount of mercury exported from the river during that period was equal to an entire year's worth of mercury calculated in previous studies.

Graydon's research and previous studies measured export of all chemical forms of mercury in the water, including methyl mercury.

Methyl mercury is a neurotoxin and it's primarily passed on to humans through contaminated fish muscle, Graydon said. This leaves northern communities vulnerable, because a large part of their diet is Arctic fish species and Beluga whales.

Graydon's new estimates were confined to the three months while previous researchers used data to model mercury export during the course of an entire year.

Previous annual mercury delivery estimates are premature because of the understudied effects of spring ice-jamming and of 45,000 delta lakes, Graydon said. That influences water chemistry as the Mackenzie River passes through the delta.

Graydon's Mackenzie River research appeared earlier this year in the journal Science of the Total Environment.