1. 1-D modeling of Fairbanks pollution plume in winter using MISTRA 1 Patrick Joyce, 2 Roland von Glasow, 1 William Simpson 1 University of Alaska Fairbanks 2 University of East Anglia, Norwich, UK Fairbanks PM2.5 Modeling Symposium June 16, 2011

2. ‣ Questions raised here: ‣ Are we NH 3 limited? ‣ Why so little particle NO 3 - ? ‣ Does secondary sulfate formation occur in MISTRA in Fairbanks simulation? ‣ My primary questions: ‣ What is the fate of NO x ? ‣ What is the timescale for removal? ‣ Is there significant deposition downwind?

3. Nocturnal nitrogen processing

4. MISTRA: 1-D column model Plume tracking Vertical resolution: 10m Integration time: 10s Photo-chemical Microphysics Vertical mixing / turbulent exchange Dry deposition Sensitivity studies

5. MISTRA: 1-D column model t=0h i) Initialize meteorology ‣ Nov. 2009 avg temp, RH ‣ 300m mixing height (ARCTAS, 2008) ii) Initialize background “clean Arctic airmass” ‣ 40 ppb O 3 ‣ < 1 ug m -3 PM 2.5

6. MISTRA: 1-D column model t=0h t=2t=4 iii) Inject pollution ‣ NO to titrate O 3 (40 ppb NO x ) ‣ Std. urban trimodal aerosol distribution scaled to Nov. average ➡ SO 4 2- (+2H + ) aerosol to match sulfate Nov. average (DEC, 2008) ➡ NH 3 to bring molar NH 4 + /SO 4 2- = 2 at surface ‣ SO 2 to match Ft. W observations (Dick, 2004)

7. MISTRA: 1-D column model t=0h t=2t=4 t=50

8. NO x (ppb v ) NH 3 (ppb v ) SO 2 (ppb v )SO 4 2- (ug m -3 )

9. NO 3 - (ug m -3 )NH 4 + (ug m -3 ) N 2 O 5 (ppt v )HNO 3 (ppb v )

10. Aerosol reactivity is sensitive to NH 3 emission

11. Increased NH 3 emission creates increased NH 4 NO 3 downwind

12. NH 3 uptake is a matter of timescale 1/5x NH 3 1/2x NH 3 2x NH 3 5x NH 3 base

13. MISTRA does not produce secondary sulfur in winter Model time (h) Total column S (ug S m -2 ) MD S at surface (ug S m -3 ) Total S SO 2 SO 4 2- 87% SO 2 13% SO 4 2- T = -15C Nov. photolysis

14. MISTRA does produce secondary sulfur in summer Model time (h) Total column S (ug S m -2 ) MD S at surface (ug S m -3 ) Total S SO 2 SO 4 2- ~10% SO 2 converted in 48-h T = +15C June 21 photolysis

15. Conclusions ‣ NH 4 + /SO 4 2- measurements downtown show we are NH 3 neutral or excess ‣ Modeled HNO 3 formation peaks ~24h downwind ‣ MISTRA produces no secondary sulfate in winter simulation This project was funded by NSF under grant ATM-0926220