Environment: Mercury sources in the Arctic tundra identified

The sources of mercury pollution in the Arctic tundra have been identified in a study published in Nature this week.

Anthropogenic activities have led to large-scale mercury pollution in the Arctic; however, a clear understanding of its source has been lacking. It has been suggested that sea-salt-induced chemical cycling of mercury and wet deposition of mercury via precipitation were the main sources of mercury to the Arctic in its oxidized form, but their relative importance has been questioned.

Daniel Obrist and colleagues collected field measurements including mercury deposition and stable isotope data in the Arctic tundra, over a two-year period, to determine the major sources of mercury in this ecosystem. The authors found that gaseous elemental mercury - a form subject to long-range atmospheric transport and global atmospheric distribution - was the dominant form of mercury found in the tundra ecosystem, accounting for 71 per cent of the total. Deposition of mercury occurred throughout the year, increasing during the summer months owing to its uptake by vegetation.

The authors’ findings suggest that the Arctic tundra serves as an important repository for atmospheric mercury, and that the high concentrations found in the tundra soil may also explain why Arctic rivers transport large amounts of mercury annually into the Arctic Ocean.