Mercury in Mackenzie River delta dramatically higher than previously believed

Researcher Jennifer Graydon 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 three-month 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 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.” Gradyon says existing studies already show Beluga whales in the western Arctic have higher mercury levels in their flesh than Belugas in the eastern Arctic. The Mackenzie River empties in the Beaufort Sea at the western edge of the Northwest Territories.

Graydon's new estimates were confined to the three months the research team spent on the delta while previous research used data to model mercury export over 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,” said Graydon. “That influence water chemistry as the Mackenzie River passes through the delta.”

“There are very few point sources for mercury in the Arctic,” said Graydon. “Mercury is a metal that undergoes long range transport so the Arctic is getting mercury from a global pool.” Graydon says the biggest contributor of man-made mercury pollution is coal-fired power production.

This summer U of A researchers will return to the Mackenzie region after it floods to study mercury levels in the thousands of lakes in the delta when flooded by the river. Graydon's Mackenzie River research was published in the journal Science of the Total Environment earlier this year.