Anthropogenic emission of mercury to the atmosphere in the northeast United States

The severity and spatial extent of the health impact of anthropogenic mercu ry (Hg) emission to the atmosphere depend on the emission rate and chemical form of the emitted species. The few measurements of combustion flue gas g ive highly variable results about how the emission is divided between the e lemental (Hg degrees) and reactive forms and are difficult to extrapolate t o a regional scale. Here we combine measurement of total gaseous mercury (T GM) and carbon dioxide (CO2) concentrations at a background site in the win ter with carbon (C) emission inventory to show that at a regional (500 km) scale, the effective anthropogenic Hg-degrees flux is 41(+/-2) g km(-2) yr( -1) in the north-east United States. This regional-scale flux was higher un der clear skies than under cloudy skies, suggesting some removal of Hg degr ees by cloud water, but the physical mechanisms of the removal are yet to b e identified.