Abstract A study is presented of the physics and chemistry relevant to the visual impact of the plume from an electric power generating plant located in the Mojave Desert. The amount of light absorption by particles in the plume did not differ significantly from that by particles in the ambient air. While sulfate and nitrate occasionally contributed substantially to the total particle mass in the plume, generally they contributed < 10% to that mass, with the contribution of sulfate substantially greater than that of nitrate. Mean rates of gas-to-particle conversion in the plume were ∼ 0.6% h −1 for sulfate and ∼ 0.08% h −1 for nitrate. Light scattering by the plume was more dependent on the total mass of particles in the sub-μm size range than on sulfate mass alone. At a wavelength of 550 nm, NO 2 absorption frequently contributed about equally with light scattering particles to the optical depth of the plume.