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AEROSOL CHARACTERISTICS AND VISIBILITY
Citation:
Waggoner, A. AND R. Charlson. AEROSOL CHARACTERISTICS AND VISIBILITY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-77/072.
Description:
This report summarizes progress in measuring the optical properties of aerosols and in relating aerosol characteristics to visibility reduction made in the author's laboratory during the period 1965-1971. An instrument, the integrating nephelometer, which measures the scattering component of extinction, b(sp), was developed and used in several field studies. Measured b(sp) and observer visibility have been shown to be highly correlated and to follow the Koschmieder relation. Measured b(sp) is highly correlated (0.95 in Los Angeles) with suspended particle volume in the 0.1 to 1.0 micrometer size range. A useful correlation (0.56 to 0.92 at various sites) has been found between b(sp) and particle mass as collected on a filter. Techniques have been developed to measure b(sp) as a function of relative humidity for ambient and model aerosols. Water, absorbed by hygroscopic aerosols, as H2SO4, and/or deliquescent aerosols, as (NH4)2SO4, make a substantial contribution to visibility reduction. Techniques were also developed to measure the absorption component of extinction, b(sp); to measure the forward/backward scattering ratio; and to determine b(sp) as a function of wavelength.