ALTERNATIVE METRICS FOR ASSESSING THE RELATIVE EFFECTIVENESS OF NOX AND VOC EMISSION REDUCTIONS IN CONTROLLING GROUND-LEVEL OZONE

This study presents a new set of metrics quantifying the response of p hotochemical air pollution systems to changes in O-3 precursor levels. Extending the traditional approach of using domain-wide maximum ozone values as the metric for guiding the development of emission control strategies, the new metrics incorporate attributes of the spatial and temporal pervasiveness and the severity of the ozone episodes consider ed for strategy development, as well as the impact on potential exposu res to ozone. The usefulness of using various alternative criteria to better understand the directionality of the impact of emission control s is demonstrated via a set of 26 simulations of a three-day period of the severe July 1988 episode over the New Jersey-Philadelphia-Delawar e Valley area. These simulations model the effect of across-the-board reductions of VOC and NOx by 25, 50, 75, and 100% of the base case. Th e impact of these reductions is found to be dependent on the control o bjective (e.g., reduction of exposure vs. reduction of the maximum) as well as on the targeted level of the control objective (e.g., reducti on of exposures below 120 ppb vs. reduction of exposures below 80 ppb) .