Mystery of Arctic mercury solved

The concentration of toxic mercury in humans and animals living in the polar regions is on the increase and the question of why has puzzled scientists since the 1990s. But now they think they understand why…

Polar bears and humans that eat marine mammals are particularly at risk from the bioaccumulation of mercury in the Arctic. Photo credit: Jenny Bytingsvik, NTNU

The Arctic is the most mercury-rich place on the planet thanks to a reaction between sea salt, sunlight and atmospheric mercury during the spring and summer say Norwegian researchers.

Under these conditions, non-toxic mercury transforms into a more reactive version of the element and is deposited on the ground - it is then converted to toxic methylmercury which can poison the entire food chain.

This was known to occur when the sun rises over the horizon in the spring after a long polar night, but now researchers from the Norwegian University of Science and Technology have discovered this also happens in the Arctic summer.

PhD student Anne Steen Orderdalen and Professor Torunn Berg studied the concentrations of mercury recorded at the air station in Ny-Ålesund at Svalbard and documented the types of mercury found over the Arctic. They tracked its fate and transport, and have revealed that far more mercury is deposited in the area than initially thought.

Although there still uncertainty surrounding the process and how it occurs, the scientists believe sunlight and the extended time period during which mercury can transform and be deposited are important factors.

Once deposited, the mercury can enter the food chain and bioaccumulate as it is stored in the body. This research may help to explain the high levels of mercury found in marine animals and polar bears, which threaten the health of people who live off these animals. Evidence suggests the contaminant can damage the nervous system, and studies of children in the Faeroe Islands show learning disabilities may be linked to high mercury concentrations.