87th AMS Annual Meeting

Wednesday, 17 January 2007
An investigation of loadings to Lake Erie of speciated Hg emissions from a coal fired power plant through Numerical Simulation of air concentration and deposition of Hg species
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Sreerama M. Daggupaty, EC, Toronto, ON, Canada; and P. Blanchard, C. Banic, and P. Cheung
Atmospheric mercury loadings to Lake Erie were numerically simulated with the use of speciated Hg emissions from a coal fired power plant on the shore of Lake Erie in Ontario.

Three-dimensional modeling and simulation 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 fine (0.25m), medium (4m), and large (20m). The numerical experiments provide the different characteristics of air concentration deposition patterns of particulate Hg, total gaseous Hg (TGM) and reactive gaseous Hg (RGM). In winter and autumn of 2000 field experiments were conducted to investigate the physical and chemical evolution of the plumes from this coal-fired power plant in Ontario. During this period an instrumented research aircraft measured the chemical and physical properties of the Hg species in the plume. A synthesis of field experimental data with the model simulations was done for understanding the characteristics of particulate Hg, TGM and RGM and necessary improvements in modeling.

RGM is 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. 2-7% of fine particle emission was deposited within 100km of the power plant whereas about 50% in winter and 25% in fall of the coarse particle emission was deposited within the same area. Comparison of model results of surface air concentration and total loading of Hg to Lake Erie with the CAMNET (Canadian Atmospheric Mercury Measurement Network) measured data suggests that the model-simulated values are in reasonable agreement.

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