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Implementing PM Source Apportionment (PSAT) in CAMx

Implementing PM Source Apportionment (PSAT) in CAMx . Greg Yarwood, Ralph Morris and Gary Wilson ENVIRON International Corporation Novato, CA (gyarwood@environcorp.com) National RPO Modeling Meeting Denver, Colorado May 24-25, 2004. Outline. Introduction Update on approach

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Implementing PM Source Apportionment (PSAT) in CAMx

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  1. Implementing PM Source Apportionment (PSAT) in CAMx Greg Yarwood, Ralph Morris and Gary Wilson ENVIRON International Corporation Novato, CA (gyarwood@environcorp.com) National RPO Modeling Meeting Denver, Colorado May 24-25, 2004 Presents:/slides/greg/PSAT_11-17-03.ppt

  2. Outline • Introduction • Update on approach • Initial results • Questions (mine and yours) Presents:/slides/greg/PSAT_11-17-03.ppt

  3. Implementing PSAT in CAMx4 • Conceptual design completed, but “living document” (needs update) • Similar to OSAT • OSAT has 4 tracer classes for ozone • PSAT has 36 tracer classes for ozone, sulfate, nitrate, ammonium, SOA, primary, mercury • Computational burden if all 36 tracer classes are required every time • PSAT design revised so that pollutant tracking can be selected at run time • e.g., just sulfate/nitrate/ammonium; just mercury, etc. Presents:/slides/greg/PSAT_11-17-03.ppt

  4. PSAT Tracer Classes • SULFATE - 2 classes • SO2 = SO2 (i.e., tracer SO2 tracks model species SO2) • SO4 = PSO4 (i.e., tracer SO4 tracks model species PSO4) • NITRATE - 7 classes for nitrate and ammonium • RGN = NO + NO2 + HONO + NO3 + N2O5 • TPN = PAN + PNA (SAPRC has several PANs) • NTR = NTR (RNO3 in SAPRC) • PN3 = PNO3 • HN3 = HNO3 • NH3 = NH3 • PN4 = PNH4 Presents:/slides/greg/PSAT_11-17-03.ppt

  5. PSAT Tracer Classes (continued) • SOA - 14 classes for secondary organics • ALK = PAR • ARO = TOL + XYL • CRE = CRES • TRP = OLE2 • CG1 = CG1 and PS1 = SOA1 • CG2 = CG2 and PS2 = SOA2 • CG3 = CG3 and PS3 = SOA3 • CG4 = CG4 and PS4 = SOA4 • CG5 = CG5 and PS5 = SOA5 • Required CAMx modification to split old CG3/SOA3 into CG3/SOA3 and CG5/SOA5 • Delete SOA yields from Alkenes because • Uncertain and insignificant Presents:/slides/greg/PSAT_11-17-03.ppt

  6. PSAT Tracer Classes (continued) • PRIMARY - 6 classes • PEC - PEC • POC - POA • PFC – FCRS • PFN - FPRM • PCC - CCRS • PCS - CPRM • MERCURY - 3 classes • HG0 - HG0 (elemental gaseous mercury) • HG2 - HG2 (reactive gaseous mercury) • HGP - HGP (primary particulate mercury) Presents:/slides/greg/PSAT_11-17-03.ppt

  7. Status of Implementation • Fully implemented in all CAMx modules for all tracer families (O3, SO4, NO3, SOA and primaries) • Successfully tested for all tracer families to assure mass conservation with host model • Currently in evaluation phase against “zero-out” modeling • Currently evaluating “how low you can go” with PSAT/OSAT • Results for SO4 follow Presents:/slides/greg/PSAT_11-17-03.ppt

  8. Source Regions and Point Sources for PSAT Versus Zero-Out Test Runs Four hypothetical point sources located in each of the four eastern US RPOs run with large and small Emissions Presents:/slides/greg/PSAT_11-17-03.ppt

  9. Hypothetical Point Source Parameters • Stack Height = 500 feet (152.2 m) • Stack Diameter = 17 feet (5.2 m) • Exit Velocity = 100 feet/sec (30.5 m/s) • Exit Temperature = 265 F (402 K) • Large Source • NOx = 164 TPD (~60,000 TPY) • SOx = 848 TPD (~310,000 TPY) • Small Source (= Large/1000) • NOx = 0.164 TPD (~60 TPY) • SOx = 0.848 TPD (~310 TPY) Presents:/slides/greg/PSAT_11-17-03.ppt

  10. SO4 -- PSAT versus “Zero-Out”MRPO Large Source -- Episode Average Presents:/slides/greg/PSAT_11-17-03.ppt

  11. SO4 -- PSAT versus “Zero-Out”MRPO Small Source -- Episode Average Presents:/slides/greg/PSAT_11-17-03.ppt

  12. SO4 -- PSAT versus “Zero-Out”MRPO Large Source – Max Hourly Presents:/slides/greg/PSAT_11-17-03.ppt

  13. SO4 -- PSAT versus “Zero-Out”MRPO Small Source – Max Hourly Presents:/slides/greg/PSAT_11-17-03.ppt

  14. SO4 -- PSAT versus “Zero-Out”MANE-VU Small Source – Max Hourly Presents:/slides/greg/PSAT_11-17-03.ppt

  15. Sulfate Comparisons for PSAT • Good agreement for extent and magnitude of sulfate impacts between PSAT and zero-out • Comparing the outer plume edge is a stringent test • Zero-out impacts tend to be smaller because oxidant limited sulfate formation distorts the zero-out measure of sulfate impacts • Zero-out impacts of Small Source noisy due to noisy ISORROPIA numerics • Saw same noisiness in VISTAS CMAQ mass conservation patch sensitivity test • Run times look very good • efficiency for sulfate >50 relative to zero-out Presents:/slides/greg/PSAT_11-17-03.ppt

  16. Oxidant Limiting Case for SulfatePSAT result is more reasonable than zero-out Presents:/slides/greg/PSAT_11-17-03.ppt

  17. How low can you go? • What is the smallest source that can be tracked using PSAT/OSAT and using the brute force method? • Compare Large and Small Source Impacts Presents:/slides/greg/PSAT_11-17-03.ppt

  18. So, how low can you go? • Conducted preliminary experiments reducing the magnitude of an SO2 source by 1000 • Differences between PSAT and zero out due to oxidant limitation seem more apparent for smaller source • Noise shows up in the zero out result • Finite precision limits resolution of small impacts • Numerical noise from model components comparable to some real impacts • Reasons to suspect ISORROPIA as a source of numerical noise. Likely due to the nature of the calculation rather than any specific limitation within ISORROPIA. Presents:/slides/greg/PSAT_11-17-03.ppt

  19. Equilibrium Question • Should HNO3/PNO3 tracers reach full equilibrium every time step? • Full equilibrium will mean that HNO3 and PNO3 have the same source apportionment • Unclear what happens in real world • Host model assumes equilibrium; brute force tests will behave as if full equilibrium exists. Therefore, initial PSAT implementation also assumes full equilibrium • Same question for NH3/NH4 and CG/SOA pairs • PSAT and TSSA differences? Presents:/slides/greg/PSAT_11-17-03.ppt

  20. Potential Uses for PSAT • Diagnostic Testing and Evaluation • Where does PM come from? • Role of biogenics, background, other sources • Other? • Source Culpability Assessment • State Contributions (e.g., CAIR/IAQR) • BART or other source Contributions • Control Strategy Design • Rank Source Contributions • DDM also useful Presents:/slides/greg/PSAT_11-17-03.ppt

  21. Modeling Options for Proposed BART Rule • Two roles for modeling in proposed BART rule • Does a potential BART-eligible source contribute to visibility impairment at a Class I area (max 24-hr) • What is degree of visibility improvement due to BART controls at a specific facility • Do BART controls result visibility improvements of > 0.5 dV averaged across 20% worst modeled days • Once a facility is BART-eligible, then all visibility precursor species must be considered (SOx, NOx, PM and VOC) • For most sources SO4 and NO3 will be primary pollutants of interest (SOx and NOx emissions) Presents:/slides/greg/PSAT_11-17-03.ppt

  22. Modeling Options for Proposed BART Rule • CALPUFF – Lagrangian non-steady-state Gaussian puff model with simplified parameterized chemistry • Advantages • Simple integrated modeling package w/ GUIs available • Computationally efficient for a few sources • EPA guideline model for > 50 km and PSD pollutants (SO2, NO2 and PM) • Mentioned in proposed BART rule • Disadvantages • Chemistry incorrect and out of date (1982) • SO4 and NO3 estimates likely not accurate and reliable Presents:/slides/greg/PSAT_11-17-03.ppt

  23. Modeling Options for Proposed BART Rule • SCICHEM – Second Order Closure Lagrangian non-steady-state model with full chemistry – requires 3-D fields of concentrations • Advantages • Treats full nonlinear chemistry • Less computationally demanding than a photochemical grid model (PGM) for a few sources • Disadvantages • Not easy to use and not widely used • Uncertainty in applicability, hasn’t been demonstrated for this type of application • Need 3-D fields without BART source(s) • More computationally demanding • than CALPFF Presents:/slides/greg/PSAT_11-17-03.ppt

  24. Modeling Options for Proposed BART Rule • CMAQ – One-atmosphere photochemical grid model • Advantages • Full chemistry • Will be set up for 36 km inter-RPO grid and several RPO 12 km grids • Disadvantages • Coarse grid resolution (36/12 km) and one-way grid nesting limit ability to resolve point sources and get correct chemistry (Plume-in-Grid may help) • How to get single source impacts: • Zero-out? • TSSA Source Apportionment? • Computationally demanding Presents:/slides/greg/PSAT_11-17-03.ppt

  25. Modeling Options for Proposed BART Rule • CAMx – One-atmosphere photochemical grid model • Advantages • Same as CMAQ • Two-way nesting and flexi-nesting can better resolve point source plumes • PSAT may be useful • Disadvantages • How to get single source impacts: • Zero-out? • TSSA Source Apportionment? • Computationally demanding Presents:/slides/greg/PSAT_11-17-03.ppt

  26. Modeling Options for Proposed BART Rule • One potential approach using CAMx/PSAT • Address each state one at a time • Center 12 km modeling grid over state to include all key nearby Class I area • Develop BCs from 36 km Inter-RPO grid 2002 run • Add 4 km flexi-nest over state of interest • Base Case run and zero-out all BART-eligible sources to identify most important visibility species (i.e., SO4 and NO3) • Apply PSAT with ~30 BART-eligible facilities as separate source groupings • Post-process to estimate each BART-eligible facility’s visibility impacts at Class I areas Presents:/slides/greg/PSAT_11-17-03.ppt

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