1. Stephen Mueller & Jonathan Mallard Tennessee Valley Authority
Modeling Natural Fine Particle Concentrations Using the CMAQ Model with Added Treatments of Reduced Sulfur Compounds
Stephen Mueller & Jonathan Mallard
Tennessee Valley Authority

2. 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.

3. 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.

4. Natural Emissions Current Technology Added Biogenic VOCs Lightning NOx
Reduced sulfur (marine, wetlands, soil, lakes & geothermal )
Biogenic NOx
Fires
Windblown dust
Ocean chlorinated gases
Sea salt
Ocean ammonia
Animal ammonia
Geogenic SO2*
*Not typically included in data inventories although the system is designed to include it.

5. Study Area – Modeling Domain
Limit of optimal lightning detection

6. 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.

7. Natural & Anthropogenic Emissions in July 2002 Data Base
“Orange”=anthropogenic “Green”=natural

8. CMAQ* Model CB05 Updates Gas chemistry Cloud chemistry
Added reactions involving DMS, H2S and derivatives.
Added reactions involving chlorine, OH, & DMS and its derivatives.
Added ClNO2, HCl and chlorine radical reactions to CB05.
*Version 4.6

9. Grid-Averaged Time Series: Sulfur

10. Grid-Averaged Time Series: Aerosols

11. Maximum Simulated “Natural” 24-hr Aerosol Concentrations for 2002
Sulfate
Organic Carbon

12. Simulated Particles vs. Haze Guidance

13. Distribution of Simulated Natural + Background PM2.5 at 50 Receptors

14. 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 systems…effects in combined emissions simulations?