Modeling Natural Fine Particle Concentrations Using the CMAQ Model with Added Treatments of Reduced Sulfur Compounds

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Modeling Natural Fine Particle Concentrations
Using the CMAQ Model with Added Treatments of
Reduced Sulfur Compounds

• Stephen Mueller Jonathan Mallard
• Tennessee Valley Authority

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Research on Natural Particle Levels

• Identify natural emissions not routinely
  considered by US regulatory modeling.
• Develop expanded natural emissions data base.
• Identify model changes needed to accommodate
  expanded list of natural emissions.
• Quantify effects of revised emissions/model
  versus results from standard modeling approach.

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Motivation for Research

• US EPA lowered the 24-hr PM2.5 standard is
  considering a lower annual standard.
• US Regional Haze Rule explicitly requires
  consideration of natural haze components.
• Efforts to establish secondary standards (e.g.,
  SOx/NOx) should consider natural pollutants.

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Natural Emissions

• Current Technology
• Biogenic VOCs
• Biogenic NOx
• Fires
• Windblown dust
• Sea salt
• Animal ammonia
• Geogenic SO2
• Added
• Lightning NOx
• Reduced sulfur (marine, wetlands, soil, lakes
  geothermal )
• Ocean chlorinated gases
• Ocean ammonia

Not typically included in data inventories
although the system is designed to include it.
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Study Area Modeling Domain
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New Natural Emissions Species

• Dimethylsulfide (DMS) oceans, lakes, coastal
  wetlands.
• H2S oceans, lakes, coastal wetlands, geothermal
  features (hot springs, fumaroles, etc.)
• Nitryl chloride (ClNO2) HCl oceans these
  emissions are surrogates for complex interaction
  between air pollutants sea salt.

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Natural Anthropogenic Emissions in July 2002
Data Base
Orangeanthropogenic Greennatural
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CMAQ Model CB05 Updates

• Gas chemistry
• Added reactions involving DMS, H2S and
  derivatives.
• Added ClNO2, HCl and chlorine radical reactions
  to CB05.
• Cloud chemistry
• Added reactions involving chlorine, OH, DMS and
  its derivatives.

Version 4.6
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Grid-Averaged Time Series Sulfur
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Grid-Averaged Time Series Aerosols
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Maximum Simulated Natural 24-hr Aerosol
Concentrations for 2002
Organic Carbon
Sulfate
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Simulated Particles vs. Haze Guidance
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Distribution of Simulated Natural Background
PM2.5 at 50 Receptors
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Primary Conclusions

• CMAQ natural particle simulations useful tool for
  investigating contributions of natural systems to
  PM2.5/haze, ozone and deposition.
• EPA natural haze guidance is too simplistic.
• Modeling DMS H2S introduces competition for OH
  that reduces sulfate formation in natural
  systemseffects in combined emissions simulations?