Oxidant and precursor trends in the metropolitan Los Angeles region

This paper describes recent historical trends in oxidant and precursors in the Los Angeles region. Control strategies and basinwide emission trends for nitrogen oxides and reactive hydrocarbons are documented year by year from 1965 to 1974. Trends in the geographic distribution of emissions are illustrated by computing net percentage emission changes over the decade for individual counties. The changes in emissions are compared with changes in ambient precursor concentrations and oxidant concentrations. We find that many of the changes in monitored air quality can be explained by trends in both total emissions and the spatial distribution of emissions.