外流影片

Arctic snowmelt collected in , Nunavut bubbles under ultraviolet light in a refrigerated laboratory at 外流影片.

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鈥檚 primary supervisor is Acadia鈥檚 Dr. Nelson O鈥橠riscoll, who holds a Canada Research Chair in Environmental . Also collaborating are , who holds a Canada Research Chair in Coastal Wetland Ecosystems, and , 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

鈥淢ercury is a neurotoxin,鈥� says O鈥橠riscoll, 鈥渨hich 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.鈥�

The Arctic is one of those sensitive ecosystems. Mercury tends to accumulate in cold regions such as the Earth鈥檚 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 鈥� becomes more concentrated 鈥� 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鈥橠riscoll says. That鈥檚 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  and sampling snow from different areas. In March 2013, O鈥橠riscoll, 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 -35潞C 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.

鈥淭he picture shows an experiment where we were irradiating a beaker filled with melted snow and measuring the elemental mercury formed,鈥� Mann says.

鈥淭hat purple glow is just the visible portion of radiation,鈥� O鈥橠riscoll adds. 鈥淭he 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.鈥�

Mann hopes to create a model that predicts, with temperature and radiation, how much mercury will stay in the snow. 鈥淓rin鈥檚 research has important implications for predicting Arctic mercury contamination as global warming advances,鈥� O鈥橠riscoll says, 鈥渁nd in response to rapid ultraviolet radiation increases that can occur with holes in the ozone layer.鈥�

The research is funded by the federal government鈥檚 .

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