A photochemical extent parameter to aid ozone air quality management

Interest in semiempirical approaches for relating precursor emissions (VOC and NOx to ozone air quality has been renewed recently. Of particular interest is a semi-empirical approach [called Smog Production Model (SPM) or SP Algorithm] initiated by Johnson and coworkers. SPM defines a photochemical extent parameter, which provides the directional guidance on the relative effectiveness of NOx and VOC controls in reducing ozone levels. In the present paper, a modified version of SPM is introduced, and the parameters involved in SPM are evaluated using urban airshed model (UAM) simulation results. UAM results are also used to examine relationships of extent parameters to ozone reductions resulting from VOC or NOx emission reductions. A modified version of SPM is applied to ambient air quality data. With improved quantified model parameter values and improved measurements of NOy, SPM may provide important information on the relative effectiveness of precursor controls. An attractive feature of SPM is that the required data are simultaneously measured NOx NOy and ozone.