Air currents carry mercury into the Arctic atmosphere primarily from Asia, and particularly China, where emissions appear to be increasing as a result of industrial expansion and small-scale coal burning. Microorganisms can uptake the mercury and convert it into methylmercury, which is toxic and fat-soluble and accumulates in animals as it passes up the food chain. As a result, some human populations, such as the Inuit of Greenland and northeastern Canada, which eat high levels of marine mammals and fish, are exposed to levels of methylmercury in excess of World Health Organization guidelines.
Nghiem is leading an Arctic field campaign this month for NASA's Bromine, Ozone, and Mercury Experiment (BROMEX), which it is hoped will provide further insights into bromine explosions and their consequences, including for tropospheric ozone levels and mercury deposition.
IMAGE: Icebergs, and small bits of floating ice from icebergs that have disintegrated, near the Kangilerngata Sermia glacier, Disko Bugt (Disko Bay), West Greenland. (Jenny E. Ross, Corbis)