OZONE ATTAINMENT DEMONSTRATION FOR THE BATON ROUGE, LOUISIANA URBAN AREA: USE OF PHOTOCHEMCIAL MODELING TO DEVELOP A REAL-WORLD OZONE ATTAINMENT STRATEGY

摘要

This paper summarizes the methods and results of an application of the variable-grid Urban Airshed Model (UAM-V) for the Baton Rouge ozone nonattainment area that was designed to obtain a quantitative assessment of the potential for compliance with the National Ambient Air Quality Standard (NAAQS) for (1-hour) ozone for a future year of 2005. The modeled attainment demonstration submitted as part of the 1995 SIP indicated that the changes in emissions that were expected to occur between 1990 and 1999 would result in attainment of the NAAQS by the 1999 attainment date. However the observation-based design value for this year was 126 ppb (just above the value of 124 required by the NAAQS). Under EPA's 1998 policy document" Extension of Attainment Dates for Downwind Areas," Baton Rouge was given additional time to demonstrate attainment of the 1 -hour ozone standard through modeling. Additional regional-scale modeling was conducted in support of the 1-hour ozone SIP extension. The additional modeling considered three recent, multi-day ozone episode periods (from September 1997, August 1997, and August 1999), and used state-of-the-science regional-scale meteorological and photochemical modeling tools and techniques to develop an attainment strategy for a future year of 2005. While the regiona'l-scale domain and emissions projections accounted for any reduced pollutant transport from Texas, the emphasis of the modeling analysis was to examine the effects of local emissions changes and to develop an attainment strategy based on local emissions reductions. The modeling databases for two of the simulation periods were adapted from the Gulf Coast Ozone Study (GCOS) modeling analysis while the third simulation period was selected to represent the attainment year. The UAM-V modeling domain is identical to that used for the GCOS modeling analysis and is presented in Figure 1. The modeling analysis included a comprehensive episode-selection analysis (to identify suitable periods for modeling), application of the MM5 prognostic meteorological model, application of the UAM-V photochemical modeling system for three multi-day simulation periods, evaluation of model performance, use of the modeling system to estimate ozone concentrations for a future-year of 2005, analysis of the effects of various emissions reduction scenarios on future-year ozone air quality, and evaluation of specific ozone attainment strategies to demonstrate future-year attainment.