| Mercury (Hg) is a potentially dangerous contaminant. The public health impact may depend on the emission rate. Anthropogenic Hg emissions in the United States are poorly characterized. Natural Hg emissions are poorly understood worldwide, due to lack of data or measurement systems.; This study sought to enhance understanding of Hg emissions to the atmosphere, with emphasis on the northeastern U.S. The research focused on three areas: (1) anthropogenic Hg emission in the northeast, (2) gaseous Hg in soils, and (3) Hg emissions from forest fires.; In (1), measurements of Hg and carbon dioxide in Connecticut were combined to quantify regional Hg emission during 1999/2000--2003/2004. Emissions showed significant interannual variation. Trajectory analysis revealed a source region of Hg that showed little interannual variation, suggesting that annual changes in emission cannot be explained by climatology. Hg fluxes from the electric power sector were correlated with emissions derived from atmospheric measurements, illustrating the importance of regional power plant emissions. However, the power sector flux was lower than expected relative to the atmospheric measurement, suggesting that emissions from sources outside the power sector may be underestimated.; In (2), a flask sampling system for measuring gaseous Hg in soil was developed and deployed in background forest soil in Connecticut during 2003-2004. This was the first detailed study of soil gaseous Hg. Observed gradients in soil gaseous Hg strongly resembled gradients in bound Hg. Soil Hg flux was correlated with gaseous Hg at 2-cm depth. The upper organic layers may act as a source of gaseous Hg that is emitted to the atmosphere. Gradients in gaseous Hg over shallow layers underscore the importance of fine vertical resolution, and therefore the utility of flask sampling.; In (3), measurements of Hg within a smoke plume from forest fires in Canada were used to determine mean Hg flux density for boreal forest fires, annual Hg emissions from Canadian fires and global Hg emissions from boreal fires. Annual Hg emissions from fires typically equal 30-100% of Canadian anthropogenic emissions. Hg emission from biomass burning is dependent on biome/species, so extrapolation from a single fire to the globe is speculative. |
