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 parti cular interest is a semi-empirical approach [called Smog Production Mo del(SPM) or SP Algorithm] initiated by Johnson and coworkers. SPM defi nes a photochemical extent parameter, which provides the directional g uidance on the relative effectiveness of NOx and VOC controls in reduc ing ozone levels. In the present paper, a modified version of SPM is i ntroduced, and the parameters involved in SPM are evaluated using urba n airshed model (UAM) simulation results. UAM results are also used to examine relationships of extent parameters to ozone reductions result ing from VOC or NOx emission reductions. A modified version of SPM is applied to ambient air quality data. With improved quantified model pa rameter values and improved measurements of NOy, SPM may provide impor tant information on the relative effectiveness of precursor controls. An attractive feature of SPM is that the required data are simultaneou sly measured NO, NOy and ozone. (C) 1997 Elsevier Science Ltd.