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Sunil Kumar TAC, COG July 9, 2007

Understand the crucial PM2.5 precursors, such as NOx, SO2, and VOC, for SIP planning and conformity analysis in the Washington DC-MD-VA region. Learn about the two-stage process, EPA guidelines, modeling techniques, and recommendations for effective planning.

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Sunil Kumar TAC, COG July 9, 2007

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  1. Finding of Significant PM2.5 Precursors for SIP and Conformity AnalysisWashington DC-MD-VA PM2.5 NAA Sunil Kumar TAC, COG July 9, 2007

  2. Washington DC-MD-VA PM2.5 NAA

  3. Significant Precursors:Two-stage Process • Determine PM2.5 Precursors for SIP • Base Year inventory must include all precursors (PM10, PM2.5, NOx, SO2, NH3, VOC) in emissions inventory • SIP: Focus on significant precursors • NEXT, Determine PM2.5 Precursors for Mobile Budgets/Conformity

  4. Evidence for Finding of Significance for Plan

  5. PM2.5 Composition – STN DataMcMillan (Washington, DC) - 2004

  6. PM2.5 Composition – High Level DaysMcMillan (Washington, DC) - 2001-2003 Winter Spring Summer Fall

  7. PM2.5 Precursors for SIP Planning • PM2.5-Pri, SO2, NOx – Presumed significant by EPA • VOC & NH3 - Presumed insignificant by EPA

  8. PM2.5 Precursors for SIP Planning • VOC – • EPA presumes insignificant. Role of VOC varies by region and is not well understood yet. • NH3 – • Limited control options • Uncertainties in inventories • NH3 reduction increases precipitation acidity (ecological & health hazard) • After SO2 reduction, PM2.5 more responsive to NOx reduction than NH3.

  9. Detailed technical analyses needed to prove VOC & NH3 significant Need • Photochemical modeling – zero-out analysis; sensitivity analysis • Photochemical source apportionment tools (PSAT, DDM, TSSA, etc.) for estimating impact of all sources • Receptor modeling (e.g. PMF, CMB) Have • Analysis of ambient monitoring data, speciation data, and trends • Analysis of emissions inventories and trends

  10. Recommendation PM2.5 Precursors for SIP Planning • Limited timeline to submit Annual PM2.5 SIP • Limited time/resources for modeling • Follow EPA’s recommendation – Consider PM2.5, SO2 and NOx as significant in absence of modeling

  11. Significance Test for Conformity

  12. PM2.5 Precursors for Conformity Analysis • PM2.5-Pri and NOx - Mobile budgets needed (Conformity rule). • SO2 - Need to demonstrate significant contributionfrom mobile sources and also look at other criteria for setting up mobile budget. • VOC & NH3 – If found significant for PM2.5 SIP, then need to look at contributionfrom mobile sources and other criteria for setting up mobile budget.

  13. Checklist PM2.5 Precursors for Conformity Analysis

  14. Checklist PM2.5 Precursors for Conformity Analysis

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