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Atmospheric long-range transport and deposition of anthropogenic mercury have been implicated in observations of elevated mercury in aquatic systems of the most remote areas on Earth. Despite the fact that mercury has been targeted for global concern as a highly toxic contaminant, its sources and the factors controlling its migration in the environment are still poorly understood.

We are developing a new global simulation of atmospheric mercury with the GEOS-CHEM model, taking advantage of new information from field and laboratory observations to better constrain our knowledge of the factors controlling the global distribution of mercury. The proposed work will involve extensive comparison of the mercury model with observations, construction of regional and global mercury budgets, and sensitivity simulations.

The ocean represents about a third of the global emissions of mercury. Field measurements have shown that oceanic evasion of mercury is highly variable spatially and temporally, likely due to local reduction of mercury in the water mediated by photochemical and biological processes. A large fraction of oceanic emissions of mercury is likely to consist of re-emission of previously deposited anthropogenic mercury.

In collaboration with Noelle Eckley Selin, Daniel Jacob and Rokjin Park at Harvard, we are developing a new formulation for air-sea exchange of mercury in the GEOS-CHEM model. We couple the atmospheric mercury simulation with a slab ocean model simulation of dissolved mercury. The figure on the right shows preliminary results of the spatial and temporal distribution of total aqueous mercury simulated with our model. The resulting net oceanic flux of mercury to the atmosphere is shown on the figure below.

Concentrations of total aqueous mercury (pM) simulated with the GEOS-CHEM model during summer and winter. The colored circles show observed concentrations.