Plume Blight 

Visual impairment of air quality that manifests itself as a coherent plume.  This results from specific sources, such as a power plant smoke stack, emitting pollutants into a stable atmosphere. The pollutants are then transported in some direction with little or no vertical mixing.

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An example of "plume blight." The thin, dark plume on Navajo Mountain results from a point source emitting particulate matter into a stable atmosphere.