During wintertime, haze episodes occur in the Dallas-Ft. Worth (DFW) urban area. Such episodes are characterized by substantial light scattering by particles and relatively low absorption, leading to so-called "white haze." The objective of this work was to assess whether reductions in the emissions of SO_2 from a specific coal-fired power plant located over 100 km from DFW could lead to a discernible change in the DFW white haze. To that end, the transport, dispersion, deposition, and chemistry of the plume of a major power plant were simulated using a reactive plume model (ROME). The realism of the simulations was tested by comparing model calculations of plume concentrations with aircraft data. For plume impact assessment, three actual scenarios were simulated: Two with clear-sky conditions, and one with the presence of fog prior to the haze. The largest amount of sulfate formation was obtained for the fog episode. Therefore, a hypothetical scenario was constructed using the meteorological conditions of the fog episode with input data values adjusted to be more conductive to sulfate formation. The results of the simulations suggest that reductions in the power plant emission lead to less-than-proportional reductions in sulfate concentrations in DFW for the fog scenario. A maximum reduction in light extinction of 13 percent was calculated for a 44 percent reduction in the power plant SO_2 emissions.
展开▼
