Research Projects

Project at a Glance

Project Status: complete

Report Published October 1983:

Title: Visibility reduction as related to aerosol constituents

Principal Investigator / Author(s): Appel, B. R.

Contractor: Air and Industrial Hygiene Laboratory, California Department of Health

Contract Number: a1-081-32

Research Program Area: Atmospheric Processes


A laboratory and field study was performed to assess the contribution to visibility reduction of both light-scattering and absorption by air pollutant particles and gases. Gaseous precursors to important visibility-reducing aerosol species were measured. Emphasis was placed on minimizing sampling artifacts for nitrate and sulfate since previous visibility studies were generally subject to substantial errors from these sources. Optical techniques for measuring the particle absorption coefficient and elemental carbon were evaluated. The aerosol species measured were fine and coarse particulate mass, sulfate, nitrate and elemental carbon, plus organic carbon and ammonium ion. The gases measured were nitric acid, NH3, SO2, NO2 and O3. Sampling was done at San Jose, Riverside and Downtown Los Angeles.

At all sites light scattering by sulfate, nitrate and elemental carbon particles contributed more than half of the light extinction. Light absorption by particles, due almost exclusively to elemental carbon, contributed 10 to 20% of the extinction. The light-scattering efficiency of fine particulate nitrate appeared to be higher than that of sulfate, in contrast to the findings of most prior studies.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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