CALPOST and POSTUTIL

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CALPOST and POSTUTIL

• CALPOST processes CALPUFF outputs
• Summarizes concentrations
• Computes visibility measures
• POSTUTIL also processes CALPUFF outputs
• Multiple simulations, deposition fluxes, etc.
• Chemistry of nitric acid/nitrate aerosols
  (ammonia limiting effects)

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Key Decisions

• Visibility calculation method
• Species to consider
• Speciation of PM-10
• Natural background light extinction
• Rayleigh scattering value
• Light extinction efficiencies
• Inclusion of sea salt
• Use of ammonia limiting method

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Visibility Calculation Method

• Screening (12 km)
• Method 6 w/EPA(2003) Class I-specific monthly RH
  values
• Refined (lt 4 km)
• Method 6 as above

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(No Transcript)
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Regional Haze
bext 3 f(RH) (NH4)2SO4 3 f(RH) NH4NO3
4OC 1Soil 0.6Coarse Mass
10EC bRay
Primary PM-2.5
Primary PM-10 PM-2.5
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Species Considered

• SO4, NO3, EC, SOA (condensible organics), soil,
  coarse PM

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Speciation of PM10
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Natural Background

• Use EPA(2003) background concentrations.
• Ammonium sulfate 0.23
• Ammonium nitrate 0.1
• Organics 1.4
• Elemental carbon 0.02
• Fine soil 0.5
• Coarse mass 3.0

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Light Extinction Efficiencies

• EPA(2003) values
• Ammonium sulfate 3
• Ammonium nitrate 3
• Organics 4
• Elemental carbon 10
• Fine soil 1
• Coarse mass 0.6

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Raleigh Scattering

• Screening Modeling
• 10 Mm-1 all Class I areas
• Refined Modeling
• 10 Mm-1 all Class I areas

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Sea Salt

• On the table for consideration

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Ammonia Limiting Method

• Screening Modeling No ALM
• Refined Modeling Use ALM

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Interpretation of Results

• Exemption Modeling
• Presumed visibility change lt 0.5 dv
• A state may use a lower value
• Based on 98 percentile value
• Maximum daily over whole Class I area?
• Receptor-specific?

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Interpretation of Results

• Control Strategy Modeling
• visibility improvement determination
• flexibility in setting absolute thresholds,
  target levels of improvement, or de minimis
  levels
• free to determine the weight and significance to
  be assigned to each factor
• one bright line may not be appropriate
• you may consider the frequency, magnitude, and
  duration components of impairment

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Suggestions in Guidance

• Comparison threshold
• No. of days or hours threshold exceeded
• Single threshold to determine significant impact
• Threshold representing an x percent change in
  improvement
• Compare 98th percent days for pre- and
  post-control runs.

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Questions

• Are there situations in which the Screening level
  approach could be used for the control strategy
  modeling?
• e.g. small sources located more than 100 km from
  any Class I area.