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Published 1979 | public
Journal Article

On the relationship between sulfate air quality and visibility with examples in Los Angeles

Cass, Glen R.

Abstract

Routine air monitoring data are related to visibility in downtown Los Angeles over the decade 1965–1974. A non-linear regression model for light extinction is employed which uses particle chemical composition as a key to particle size and solubility. Sulfates and oxides of nitrogen (NO_2 and nitrates) plus particulates correlated with NO_2 are implicated as the major contributors to visibility reduction in downtown Los Angeles. It is shown that there is a pronounced increase in light scattering per unit sulfate solute mass on days of high relative humidity, as would be expected for a hygroscopic or deliquescent substance. Using the chemically resolved regression model, estimates are made of the long-run visibility impact of reducing sulfates to one half and to one quarter of their measured historic values on each past day of record. It is found that the effect of such a sulfate concentration reduction would have been manifested most clearly by a substantial reduction in the number of days per year with average visibility less than 3 miles (4.8 km).

Additional Information

© 1979 Pergamon Press Ltd. First received 10 October 1978 and in final form 19 January 1979. This work has been supported by the Ford Foundation (Grant No. 740-0469), a grant to the author from Rockwell International, gifts to the Environmental Quality Laboratory, and by the California Air Resources Board (Contract No. A5-061-87). Thanks are due to the staff of the Metropolitan Zone of the South Coast Air Quality Management District (formerly the Los Angeles Air Pollution Control District) for their cooperation and assistance in furnishing data for this analysis. A somewhat longer version of this study has been distributed under the title The Relationship Between Sulfate Air Quality and Visibility at Los Angeles, Caltech Environmental Quality Laboratory Memorandum 18, August 1976. It forms a portion of the regional sulfate air quality control strategy study referenced to Cass (1978).

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023