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-Theoretical relationships have been derived and transformed into a computer model to describe plume visual impact at various observer vantage points resulting from power plant boiler operation. Plume visual impact results from a reduction in visual range (visibility) and plume cotoration. The model considers plume transport and diffusion, light scattering and absorption by aerosols and gases, and chemical transformation in the plume of nitric oxide to nitrogen dioxide, sulfur dioxide to sulfates, and nitrogen oxides to nitrates.The model is applied in a parametric study to explore the effect of emissions and environmental conditions on plume visual impact. The case selected is a hypothetical 1500 Mwe coal-fired power plant equipped with efficient particulate abatement equipment. The results establish that visual range is not significantly affected unless the observer is viewing along the plume axis or unless significant amounts of secondary particles are formed in the plume. Yellow-brown plume coloration is shown to result from the net production of nitrogen dioxide gas in the plume. The coloration is most apparent during stable and clear atmospheric conditions and effectively masked for elevated concentrations of background or plume aerosol.

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