Development and evaluation of emission control strategies for Georgia using the CMAQ air quality model

Recently, EPA designated multiple areas in Georgia as non-attainment for 8-hour ozone (Atlanta and Macon) and PM2.5 (Atlanta, Macon, Chattanooga, and Floyd County). In order to develop efficient emission control strategies and demonstrate future attainment with the National Ambient Air Quality Standards (NAAQS), the Georgia Environmental Protection Division (GA EPD) is using the CMAQ/MM5/SMOKE modeling system. The modeling used in these attainment demonstrations is based on the VISTAS regional haze modeling which includes annual simulations of 2002, 2009, and 2018 at 36 km (continental U.S.) and 12 km (Eastern U.S.) grid resolutions. In addition, GA EPD has developed a sub-12 km grid covering Alabama and Georgia (and adjacent states) for detailed PM2.5 modeling and a 4 km grid covering the entire state of Georgia for ozone modeling. Final attainment modeling to support Georgia's State Implementation Plan (SIP) for PM2.5 will involve annual simulations while the SIP modeling for ozone will simulate four months of the ozone season (05/20/02 – 09/20/02).

In order to most efficiently design emission control strategies to reduce PM2.5 and ozone, GA EPD is performing episodic emission sensitivities on a winter episode (11/19/02-12/19/02) and a summer episode (05/25/02-06/25/02). These episodes were selected based on a Classification and Regression Tree (CART) analysis to ensure that a variety of meteorological conditions important to PM2.5 and ozone formation were simulated. Regional sensitivities of ozone (ppb/tpd) and PM2.5 (mg/m3/tpd) include responsiveness to 10% emission reductions in NOx, VOCs, SO2, NH3, and primary carbon PM2.5 in Atlanta, Macon, Chattanooga, and Floyd County. Point source sensitivities simulate the installation of SCRs (NOx) and scrubbers (SO2) at a number of large coal-fired power plants.

These modeling results are combined with economic considerations and health impacts to determine the most effective approach to bringing Georgia into attainment with the NAAQS by 2009. Resulting emission control strategies are evaluated by running them through annual simulations for PM2.5 at 12 km grid resolution and through a shorter 4-month summer period for ozone at 4 km grid resolution. A number of different emission control strategies are being evaluated and will range from moderate controls to more extreme controls. Future year design values are calculated in accordance with EPA modeling guidance and compared to the NAAQS to see if each non-attainment area meets EPA's requirements in 2009. Also, additional controls beyond those required to meet the NAAQS are evaluated to allow for a concentration “safety buffer” in case the meteorological conditions are less favorable in the future.