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Study using monitoring & modeling to understand PM2.5 impact by PRGS. Compare local to regional data, analyze emissions, and provide recommendations for localized modeling.
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Using Measurements and Modeling to Understand Local and Regional Influences on PM2.5 in Vicinity of the PRGS
Background • Need to determine best way to quantify PM2.5 impacts near PRGS • Performed at VA DEQ’s request using VA DEQ-approved methodology • Utilize monitoring and modeling
Overview • PM2.5 = Particulate aerodynamic diameter < 2.5 microns • Multi-faceted data set from 2006 – 2007 • ENSR PM2.5, SO2, and meteorological data local to the Mirant Potomac River Generating Station (PRGS) • Regional FRM PM2.5 data (<130 km) obtained from the states of Virginia, Maryland, and The District Department of the Environment* (Washington, DC; <12km) • AERMOD dispersion modeling based on PM2.5 and SO2 emissions from PRGS *2007 DDOE data have not yet been fully validated and certified using the standard procedures to guarantee their quality and are subject to change.
Objectives • Analyze local versus regional PM2.5 for yearly, seasonal, localized-urban, and meteorological trends • Establish source-specific (PRGS) PM2.5 impact by: • Comparing near-field to regional PM2.5 measurements • Correlating near-field SO2 and PM2.5 measurements • Modeling PM2.5 emissions • Develop recommendations for localized PM2.5 modeling
Monitoring Methodology: Local Monitors & Regional PM2.5 Monitors Local Monitors Regional Monitors
Local Continuous PM2.5 (SE-TEOM): Meteorological Analysis PRGS Location
Conclusions: Regional vs. Local PM2.5 Monitoring • Local PM2.5 (PRGS) agrees with regional PM2.5 • Local PM2.5 measurements do not predict a “hot spot” • Met analyses of continuous PM2.5 (SE-TEOM) confirms regional PM2.5 phenomena Questions formulated for quantitative impact analysis and AERMOD dispersion modeling • How much PM2.5 does the PRGS contribute to local monitors? • How much PRGS contribution is from filterable or condensable particulates?
Quantitative PRGS PM2.5 Impact Using Monitor Data • Estimated PRGS SO2 impact = Marina Towers SO2 monitor conc minus average of all other PRGS SO2 monitors (4 total = background) • Ratio of PM2.5 emissions to SO2 emissions • PM2.5 lb/MMBtu rates from average of December 2006 stack tests • Filterable + condensable = 0.013 lb/MMBtu • Filterable only = 0.0008 lb/MMBtu • SO2 lb/MMBtu rates: actual operations data November 1, 2006 through October 31, 2007, 24-hour average lb/MMBtu • Estimated PRGS PM2.5 impact = Ratio of emissions x PRGS SO2 impact
Quantitative PRGS PM2.5 Impact Using AERMOD • Meteorological Data from Reagan International Airport for November 1, 2006 through October 31, 2007 • Equivalent Building Dimensions (EBDs) used to account for building downwash of stacks • PM2.5 from five stacks + fugitive ground level sources • AERMOD used to predict concentrations on roof of Marina Towers residential complex, where PRGS FRM PM2.5 monitor is located
Stack Parameters and PM2.5 Emissions Input to AERMOD • Stack parameters = actual operations data from Nov. 1, 2006 through Oct. 31, 2007 • Hourly PM2.5 emissions input to AERMOD (lb/hr) = Ratio of PM2.5 lb/MMBtu to actual hourly SO2 lb/MMBtu x actual hourly SO2 emissions (lb/hr) • Fugitive PM2.5 emissions data developed from U.S. EPA’s AP-42
PM2.5 Concentrations on High SO2 Marina Towers Measurement Days • Local PM2.5 is both > and < regional PM2.5 during high SO2 events • No indication of a relationship between high SO2 days and PM2.5 • On high SO2 days, local PM2.5 concentrations are reflective of regional conditions
AERMOD Marina Towers Modeling Results: High SO2 Impact Days (Cont.)
AERMOD Ground Level Modeling Results: High SO2 Impact Days (Cont.)
PM2.5 NAAQS Compliance Modeling • Typical Analysis • 98th percentile modeled impact (filterable + condensable stack PM2.5 + fugitives) • Add in background conc (98th percentile, EPA monitor) Example: 20 µg/m3 (modeled) + 32 µg/m3 (background) = 52 µg/m3 • ENSR Recommended Analysis • 98th percentile modeled impact (filterable stack PM2.5 + realistic fugitives) • Add in realistic background conc (on days with high plant impact) Example: 2 µg/m3 (modeled) + 20 µg/m3 (background) = 22 µg/m3
Conclusions: Qualitative Comparison, Quantitative Analysis, and AERMOD Modeling • PRGS contributes very little to local monitor; low impact • PRGS contribution is likely from filterable particulate • AERMOD PM2.5 over-prediction on MT likely due to: • Under-estimation of plume rise from merging multiple plumes • Inclusion of condensable particulate • AERMOD PM2.5 prediction at SE Fenceline in agreement with measured data: likely due to fugitives • PM2.5 NAAQS Compliance: • Accurate fugitive emission calculations imperative • Use realistic background concentrations on high plant impact days