1. A comparison of PM 2.5 simulations over the Eastern United States using CB-IV and RADM2 chemical mechanisms Michael Ku, Kevin Civerolo, and Gopal Sistla New York State Department of Environmental Conservation Albany, NY

2. INTRODUCTION Assess CMAQ in simulating PM for two chemical mechanisms Comparison with hourly TEOM (PM 2.5) measurements Comparison with daily averaged PM2.5 and species data from SEARCH and IMPROVE (MANE-VU) Sensitivity of the chemical mechanism to emission reductions

3. MODEL SIMULATIONS CMAQ (version 4.1) with CB-IV and RADM2 at 36km and 16 vertical layers MM5 run at 108/36/12 km nesting grids and 25 vertical layers up to about 16 km 1995 EPA emission data for CB-IV and RADM2 chemistry Emission reduction simulation:. 50 % reduction in elevated SOx. 50 % reduction in elevated SOx and 50% in elevated NOx

4. MEASUREMENTS TEOM hourly PM 2.5 measurements – 15 sites in the modeling domain SEARCH network -- daily 24-hour PM 2.5, sulfate, nitrate IMPROVE (MANE-VU) network -- twice a week 24- hour PM 2.5, sulfate and nitrate

5. Modeling Domain and Monitor Sites

6. Daily averaged PM 2.5 concentrations on July 15, 1999 (A) CB-IV; (B) RADM2 (A) (B)

7. Daily averaged percentage of Sulfate to the total PM mass, (A) CB-IV; and (B) RADM2 (A) (B)

8. Daily averaged percentage of Nitrate to the total PM mass, (A) CB-IV; and (B) RADM2 (A) (B)

9. TEOM HOURLY DATA COMPARISON Scatter plots Diurnal plots Statistics

12. Averaged over 15 TEOM sites

13. CB - IVRADM2 Sample Size 1904 Mean Bias (ug/m 3 ) -1.41-24.89 STD (ug/m 3 ) 21.5423.55 Mean Normalized Bias (%) 98.05221.58 Mean Normalized Gross Error (%) 136.26226.96 R 0.190.56 Slope 0.190.91 Intercept 21.0626.90

14. Comparison with 24-hour data from SEARCH and IMPROVE (MANE-VU)

15. Comparisons with SEARCH data

16. Compariosn with IMPROVE (MANE-VU) data

17. EMISSION REDUCTION SIMULATUIN 50% reduction of elevated SOx emissions 50% reduction of elevated SOx emissions and 50% reduction of elevated NOx emissions

18. Percentage reduction of PM 2.5 Concentration at 50% reduction of elevated SOx emission, (A) CB-IV; and (B) RADM2 (A) (B)

19. Percentage reduction of PM 2.5 concentration at 50% reduction of elevated SOx emission and 50% reduction of elevated NOx emission, (A) CB-IV; and (B) RADM2 (A)(B)

20. SUMMARY Both CB-IV and RADM2 overpredicted hourly TEOM PM 2.5 measurements RADM2 chemistry predicted much higher PM 2.5 concentrations than CB-IV CB-IV based simulations showed relatively lower sulfate and higher nitrate compared to those of RADM2 RADM2 chemistry is more sensitive in response to emission reductions than CB-IV