Analysis of Power Plant NOx Emission Changes and Their Impact on Ozone in the Eastern United States

Changes in NOx emissions from electric power generation plants due to the implementation of pollution controls are measured by Continuous Emission Monitoring Systems (CEMS) and compiled by the EPA. Eastern US power plant NOx emissions decreased between 1999 and 2004 by about 50 percent during the summer ozone season (May - September). CEMS data for the 1999 - 2004 period are analyzed to understand the extent of these emission changes and their temporal and spatial variability. CEMS data are used to construct a nationwide 2004 update to the power plant portion of the EPA's NEI 1999, the most recent final emission inventory available for air quality models. O3 concentrations during the 2004 ozone season are simulated by the Weather Research and Forecasting Chemistry (WRF-Chem) model, with a base emission scenario using the NEI 1999 and a perturbation scenario using the updated 2004 inventory. The impact of these NOx emission trends on O3 in the Eastern US is described.