1. Georgia Institute of Technology Estimation of NH 4 + /SO 4 2- Molar Ratios Using URM Modeling Outputs Jim Boylan, Talat Odman, Ted Russell April 10, 2001

2. Georgia Institute of Technology Outline SEAVS Data –IMPROVE –Harvard Methodology Model Results –July 11 - 19, 1995 –February 8 - 13, 1994

3. Georgia Institute of Technology Fine PM Ions from IMPROVE 19.2  g/m 3

4. Georgia Institute of Technology Fine PM Ions from HEADS 19.2  g/m 3

5. Georgia Institute of Technology NH 4 + /SO 4 2- Molar Ratios

6. Georgia Institute of Technology NH 4 + vs. SO 4 2- from IMPROVE 19.2  g/m 3 28.8  g/m 3

7. Georgia Institute of Technology NH 4 + vs. SO 4 2- from HEADS 17.3  g/m 3 24.0  g/m 3

8. Georgia Institute of Technology Aerosol Species Aerosol species that are possible in the ISORROPIA aerosol module: (NH 4 ) 2 SO 4 NaHSO 4 NH 4 NO 3 (NH 4 )HSO 4 Na 2 SO 4 NH 4 Cl (NH 4 ) 3 H(SO 4 ) 2 H 2 SO 4 NaCl NaNO 3 URM Model Output ( individual concentration): Sulfate (SO 4 2- ) - SUL1, SUL2, SUL3, SUL4 Nitrate (NO 3 - ) - NIT1, NIT2, NIT3, NIT4 Ammonium (NH 4 + ) - AMN1, AMN2, AMN3, AMN4 Chloride (Cl - ) - CHL1, CHL2, CHL3, CHL4 Sodium (Na + ) - SOD1, SOD2, SOD3, SOD4 Therefore, we can not directly determine the form of the sulfate aerosols by looking at the URM output.

9. Georgia Institute of Technology Derivation of Equation The aerosol concentrations are in  g/m 3. To get the moles of each species, we must sum the concentrations in all four size bins and divide by the Molecular Weights. We need to subtract out the NH 4 + and Na + associated with NO 3 - and Cl -, leaving only the NH 4 + and Na + associated with SO 4 2-. We cannot subtract out the Na + associated with the SO 4 2- because we do not now what form it is in (Na 2 SO 4 or NaHSO 4 ).

10. Georgia Institute of Technology Molar Ratio Equation If we assume or show that the moles of Na + are small compared to the moles of NH 4 +, we can estimate the molar ratio of NH 4 + to SO 4 2-. If the moles of Na + and NH 4 + are similar, we can assume that both are in the same sulfate form.

11. Georgia Institute of Technology Molar Ratios We can either look at the NH 4 + /SO 4 2- molar ratio on an hour by hour basis or a 24-hour averaged ratio.

12. Georgia Institute of Technology July 11, 1995

13. Georgia Institute of Technology July 11, 1995

14. Georgia Institute of Technology July 12, 1995

15. Georgia Institute of Technology July 13, 1995

16. Georgia Institute of Technology July 14, 1995

17. Georgia Institute of Technology July 15, 1995

18. Georgia Institute of Technology July 16, 1995

19. Georgia Institute of Technology July 17, 1995

20. Georgia Institute of Technology July 18, 1995

21. Georgia Institute of Technology July 19, 1995

22. Georgia Institute of Technology February 8, 1994

23. Georgia Institute of Technology February 8, 1994

24. Georgia Institute of Technology February 9, 1994

25. Georgia Institute of Technology February 10, 1994

26. Georgia Institute of Technology February 10, 1994

27. Georgia Institute of Technology February 11, 1994

28. Georgia Institute of Technology February 12, 1994

29. Georgia Institute of Technology February 13, 1994

30. Georgia Institute of Technology Summary Generally, the SEAVS Data show: –no H 2 SO 4 when [SO 4 2- ] < 20  g/m 3 –25% H 2 SO 4 when [SO 4 2- ] between 20  g/m 3 and 25  g/m 3 Generally, the URM Model Results show: –no H 2 SO 4 when [SO 4 2- ] < 20  g/m 3 –25% H 2 SO 4 when [SO 4 2- ] between 20  g/m 3 and 24  g/m 3 Presence of some H 2 SO 4 in West Virginia during the July 1995 Episode. No H 2 SO 4 in the February 1994 Episode.