Arctic snowmelt collected in Resolute Bay, Nunavut bubbles under ultraviolet light in a refrigerated laboratory at Acadia University.

The snow is at the centre of a PhD research project by Erin Mann, a Memorial University student based at Acadia, on the effects of ultraviolet radiation on mercury movement in ecosystems. Mann’s primary supervisor is Acadia’s Dr. Nelson O’Driscoll, who holds a Canada Research Chair in Environmental Biogeochemistry. Also collaborating are Dr. Mark Mallory, who holds a Canada Research Chair in Coastal Wetland Ecosystems, and Dr. Susan Ziegler, who holds a Canada Research Chair in Environmental Science. 

Together, the team is studying how solar radiation changes the nature of mercury as Arctic snow melts.

Sensitive ecosystems

“Mercury is a neurotoxin,” says O’Driscoll, “which means it affects the brains of organisms. Mercury is everywhere in the world, but it is particularly problematic in sensitive ecosystems. Sensitive ecosystems tend to accumulate mercury like a sponge and change it into a form that gets into organisms easily.”

The Arctic is one of those sensitive ecosystems. Mercury tends to accumulate in cold regions such as the Earth’s poles, falling with snow in winter and becoming part of the snowpack. While it is in the snow, mercury moves between the snowpack and the atmosphere. If it is still in the snowpack when it melts, the mercury can move into lakes, rivers and the ocean. Once that happens, it can be converted into a form (methyl mercury) that accumulates in organisms, and biomagnifies – becomes more concentrated – as it moves up through the food web.

Arctic spring, when the sun first comes up over the Arctic horizon, is a dynamic time, O’Driscoll says. That’s when ultraviolet radiation begins to interact with the atmosphere and the snow.

In March 2012, Mallory and Mann were in Resolute Bay, working at the Polar Continental Shelf Research Station and sampling snow from different areas. In March 2013, O’Driscoll, Mallory, and Mann made the trip, collecting snow and conducting a 10-day experiment on site that provided comparison data for their lab work. Using sensitive equipment in the Arctic at -35ºC poses logistical challenges; few labs in the world do this kind of research.

Back in the lab

Using snow brought back to Acadia, Mann performs controlled experiments using a photoreactor, which simulates different wavelengths of solar radiation.

“The picture shows an experiment where we were irradiating a beaker filled with melted snow and measuring the elemental mercury formed,” Mann says.

“That purple glow is just the visible portion of radiation,” O’Driscoll adds. “The ultraviolet radiation is not visible, and that is what is really driving the reaction. We are discovering how quickly ultraviolet radiation changes the form of mercury in the snow. It produces a gaseous form of mercury, which can leave the snowpack or snowmelt before it can get into the food web. We can measure that gaseous form of mercury as it is created.”

Mann hopes to create a model that predicts, with temperature and radiation, how much mercury will stay in the snow. “Erin’s research has important implications for predicting Arctic mercury contamination as global warming advances,” O’Driscoll says, “and in response to rapid ultraviolet radiation increases that can occur with holes in the ozone layer.”

The research is funded by the federal government’s Northern Contaminants Program.

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