Contributions to light extinction during project MOHAVE

The contribution of aerosols to light extinction at Meadview, AZ, during summer 1992 was estimated using Mie theory and size-resolved aerosol chemical measurements. Sulfate particle size increased as a function of relative humidity. Twelve-hour average light scattering was estimated to within 15%. Sulfate was the most abundant chemical component in the fine aerosol fraction. On average, Rayleigh scattering, coarse particles, and fine sulfates contributed 39, 21, and 19% to total light extinction. Average estimated light scattering was largely insensitive to assumptions about mixing state, degree of sulfate neutralization and organic carbon water uptake properties. It was estimated that a reduction of Mohave Power Plant (MPP) SO2 emissions corresponding to a contribution of 19% to ambient sulfate would have resulted in a decrease in total light extinction of between 3.3 and 5.3%.