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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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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

Presents:/slides/greg/PSAT_11-17-03.ppt

outline
Outline
  • Introduction
  • Update on approach
  • Initial results
  • Questions (mine and yours)

Presents:/slides/greg/PSAT_11-17-03.ppt

implementing psat in camx4
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

psat tracer classes
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

psat tracer classes continued
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

psat tracer classes continued6
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

status of implementation
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

source regions and point sources for psat versus zero out test runs
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

slide9

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

so4 psat versus zero out mrpo large source episode average
SO4 -- PSAT versus “Zero-Out”MRPO Large Source -- Episode Average

Presents:/slides/greg/PSAT_11-17-03.ppt

so4 psat versus zero out mrpo small source episode average
SO4 -- PSAT versus “Zero-Out”MRPO Small Source -- Episode Average

Presents:/slides/greg/PSAT_11-17-03.ppt

so4 psat versus zero out mrpo large source max hourly
SO4 -- PSAT versus “Zero-Out”MRPO Large Source – Max Hourly

Presents:/slides/greg/PSAT_11-17-03.ppt

so4 psat versus zero out mrpo small source max hourly
SO4 -- PSAT versus “Zero-Out”MRPO Small Source – Max Hourly

Presents:/slides/greg/PSAT_11-17-03.ppt

so4 psat versus zero out mane vu small source max hourly
SO4 -- PSAT versus “Zero-Out”MANE-VU Small Source – Max Hourly

Presents:/slides/greg/PSAT_11-17-03.ppt

sulfate comparisons for psat
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

oxidant limiting case for sulfate psat result is more reasonable than zero out
Oxidant Limiting Case for SulfatePSAT result is more reasonable than zero-out

Presents:/slides/greg/PSAT_11-17-03.ppt

how low can you go
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

so how low can you go
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

equilibrium question
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

potential uses for psat
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

modeling options for proposed bart rule
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

modeling options for proposed bart rule22
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

slide23

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

slide24

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

slide25

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

modeling options for proposed bart rule26
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