The relative effectiveness of NOx and VOC strategies in reducing Northeast U.S. ozone concentrations

This investigation was conducted to compare the relative benefits of controlling emissions of VOC vs. NO_x for reducing tropospheric O₃ (smog) concentrations in the Northeast United States. Because of the nonlinear nature of O₃ photochemistry, controls on NO_x emissions could actually result in increases in O₃ depending on the relative amount of VOC present and meteorological conditions. The Regional Oxidant Model (ROM) was used as the tool for estimating the impacts of different VOC and NO₃ strategies. Scenarios simulated include a future baseline and separate strategies with controls on just NO, just VOC, and a combination of VOC and NO_x controls. The results indicate that in general, NO_x controls are more beneficial across the region than VOC controls. However, for several large urban areas, NO_x controls were predicted to result in higher O₃ than VOC controls. Also, the relative benefits of VOC and NO_x controls varied from day-to-day suggesting a dependency on meteorological conditions. Given the variable nature of the effects of NO_x controls, additional modeling using more spatially resolved models is warranted to identify specific strategies for attainment of the ozone NAAQS in individual areas.