Efficacy of nitrogen oxides and hydrocarbons emissions controls in ozone attainment strategies as predicted by the Urban Airshed Model

Abstract

The primary object of this paper is to provide a preliminary assessment of the effectiveness of NO x vs Volatile Organic Compounds (VOC) emissions control options in improving O3 air quality over the New York metropolitan area. To this end, we have applied the Urban Airshed Model (UAM) with the Carbon Bond IV (CB-IV) chemical mechanism utilizing the results of the Regional Oxidant Model (ROM) for the specification of initial/boundary concentrations and wind fields to the UAM. After examining the sensitivity of the predicted O3 concentrations to initial/boundary conditions and biogenic emissions, we have evaluated the impact of various hypothetical emissions reduction options on O3 air quality. Nested ROM/UAM simulations with an across-the-board reduction of 75% in the NO x and VOC emissions from sources located within the New York metropolitan area indicate that the option of VOC-only control is superior to the NO x -only control in reducing not only peak O3 levels over the entire modeling domain but also population exposure to unhealthy O3 levels. The model predicts that the combined 75% NO x and VOC control option also reduces the peak O3 concentration, but the improvement in O3 air quality is less than that predicted for the 75% VOC-only control strategy. Additional modeling analyses with different mix and levels of emissions control and meteorological conditions are needed to confirm these preliminary findings.