Multiscale modeling of the atmospheric fate and transport of mercury

Abstract

A numerical simulation of the atmospheric fate and transport of mercury (Hg) was conducted using a multiscale approach. Two different spatial scales were used to simulate (1) the global cycling of atmospheric Hg and (2) the atmospheric deposition of Hg in potentially sensitive areas. The global simulation was conducted using an updated version of our global Hg chemical transport model (CTM). The imbedded continental simulation was conducted using an updated version of the regional/continental CTM, TEAM. Simulations were conducted using 1998 meteorology and 1998/1999 emission inventories. Model simulation results show improved performance compared to earlier simulations. For example, the global simulation shows background concentrations of Hg species, interhemispheric gradients, and vertical gradients that are consistent with available measurements. The comparison of simulated Hg wet deposition fluxes with data from the Mercury Deposition Network in the United States shows a coefficient of determination ( r 2 ) of 0.75, little bias (−3%), and an average gross error of 21%. The major remaining sources of uncertainties, which include speciation of Hg emissions, Hg atmospheric chemistry, and dry and wet deposition processes for Hg species, are discussed.