Three-dimensional numerical modeling experiments were conducted using the BLFMAPS-a Mesoscale Boundary Layer forecast and Air pollution prediction system. The modeling system was utilized to simulate meteorology and the air concentration, dry deposition, wet deposition and air-water exchange of Hg species. Simulations were done for Hg particulates with three aerodynamic particle diameters of small (0.25ƒÝm), medium (4ƒÝm), and large (20ƒÝm). The numerical experiments exhibited the different characteristics of Hg concentration and deposition patterns of particulate Hg (Hg-p), gaseous elemental Hg (GEM) and reactive gaseous Hg (RGM).
For three out of four emission scenarios RGM is found to be the dominant contributor of the three species of Hg to the Lake Erie loading. Though particulate Hg contribution is relatively small to the net loading, particle size makes interesting deposition patterns. Coarser particles have a stronger deposition rate than finer particles. Fine particles have a longer lifetime in the atmosphere and transport over long distances. 28% of the coarse particle and 7% of fine particle emissions were deposited within 100 km of the power plant. Our experiments also suggest that a case with a larger GEM portion of emission (about 90% of total Hg emission) will have the least amount of total Hg loading to the Lake Erie.
Comparison of model results of surface air concentration and total loading of Hg to Lake Erie with the CAMNeT (The Canadian Atmospheric Mercury Network) and MDN (Mercury Deposition Network of US National Atmospheric Deposition Program) measured data suggest that the power plant has a potential impact of loading of less than 15% of the atmospheric deposition.