ROMANS Nitrogen Source Sensitivity Analysis

1. ROMANS Nitrogen Source Sensitivity Analysis Mike Barna1 Marco Rodriguez2 Kristi Gebhart1 Bill Malm1 Bret Schichtel1 Jenny Hand2 1 ARD-NPS, Fort Collins, CO 2 CIRA, Fort Collins, CO WRAP Workshop on Regional Emissions & Air Quality Modeling Denver, CO 29-30 July 2008 National Park Service U.S. Department of the Interior Cooperative Institute for Research in the Atmosphere

2. Nitrogen deposition at RMNP • N deposition increasing in the Rocky Mountains • Alpine ecosystems are susceptible to extra N • N acts as a fertilizer → ecosystem change • changes may be hard to reverse • most deposition occurs as wet dep (~2/3) • critical load: 1.5 kg/ha/yr

3. Rocky Mountains = magnificent views, fragile ecosystem, complex met • Complex (small scale) diurnal and seasonal mountain circulation patterns. • Vertical de-coupling due to inversions and stagnation in valleys. • Orographic precipitation & isolated convective storms • Lack of observations in remote mountainous areas. • We still want accurate modeled winds, moisture, temperature, precip for CAMx, trajectories.

4. ROMANS: Rocky Mountain Atmospheric Nitrogen & Sulfur Study • Two field campaigns conducted during spring (April) and summer (July – Aug) of 2006 • Measure concentration and wet dep of important N and S species: NH4, NO3, NH3, NOx, SO4

5. local v. regional v. distant? oxidized or reduced? Where is the nitrogen coming from? National Park Service U.S. Department of the Interior Cooperative Institute for Research in the Atmosphere

6. Modeling & data analysis ROMANS • Back trajectories • Airmass conditional probability • Dry deposition of ‘missing’ nitrogen • Tracer simulations -> EOF analysis (Bill Malm) • ‘Lagrangian process analysis’ • Base case simulation • Source apportionment of N and S with PSAT • ‘Hybrid modeling’ (Bret Schichtel) • ….at the end, need to reconcile results from these different analyses

7. Applying CAMx in ROMANS • 36/12/4 km domains • Met from obs-nudged MM5 • Emissions based on updated 2002 WRAP inventory Domain 1 36 Km 165 x 129 Domain 2 12 Km 103 x 115 Domain 3 4 Km 163 x 118 35 layers – 34 from WRAP, plus a 10-m layer

8. Distribution of NH3, NO3 • NH3: • Rapidly dry deposits • Emissions very uncertain • Strong spatial gradients • NO3: • Longer lifetime • Particle or gas phase

9. April 2006 ROMANS base case Beaver Meadows (RMNP) Grant, Nebraska NH4+ NO3 SO4= NH3 HNO3 SO2

10. ‘Lagrangian process analysis’ • What processes influence the concentration within an airmass during its trajectory to RMNP? • Wet and dry deposition • Emissions • Gas and aerosol chemistry NH3 NH4+

11. CAMx PSAT source apportionment • Sulfur species • SO2i Primary SO2 emissions • PS4i Particulate sulfate ion from primary emissions plus secondarily formed sulfate • Nitrogen species • RGNi Reactive gaseous nitrogen including primary NOx (NO + NO2) emissions plus nitrate radical (NO3), nitrous acid (HONO) and dinitrogen pentoxide (N2O5). • TPNi Gaseous peroxyl acetyl nitrate (PAN) plus peroxy nitric acid (PNA) • NTRi Organic nitrates (RNO3) • HN3i Gaseous nitric acid (HNO3) • PN3i Particulate nitrate ion from primary emissions plus secondarily formed nitrate • Ammonia/ammonium • NH3i Gaseous ammonia (NH3) • PN4i Particulate ammonium (NH4)

12. CAMx tracer simulations • ~100 source regions • Tracers for NH3, NOx, SO2 • Conserved, dry dep, wet dep, total dep • Use with EOF’s

13. ‘Missing nitrogen’ at RMNP • N dry deposition at RMNP based on CASTNet • Only three N species are typically ‘measured’ for dry deposition: NH4+, NO3- and HNO3 • What happens when we consider the dry deposition of total N at RMNP? • Oxidized N (the NOy budget): • NOx, HNO3, NO3-, PAN + other organic nitrates, HONO, nitrate radical + N2O5 • Reduced N: • NH3, NH4+ • Simulate this ‘missing N’ with CAMx

14. Annual average modeled nitrogen concentration from CAMx for 2002 CASTNet species: example ‘missing N’ species:

15. What happens to emitted NOx & NH3 • NH3: rapid deposition, NH3 NH4+, no gas-phase oxidation • NOx: complicated photochemistry, HNO3 NO3-, some species rapidly deposit (HNO3, NO.) NH3 NOx

16. CAMx total N vs CASTNet N at RMNP Total Reduced N (NH3 + NH4+): Total Oxidized N (NOy): Conc: Dry Dep:

17. Modeled dry deposition at RMNP

18. Modeled dry deposition at RMNP

19. CASTNet v. CAMx dry dep velocities 1Pryor et al., 2004 2Duyzer et al., 1992 3Finlayson-Pitts and Pitts, 1999 4Asman, 2004 5Seinfeld and Pandis, 2006 6Pryor et al., 2008

20. Yearly CAMx and CASTNet estimates of dry deposited N at RMNP for 2002

21. Summary • Nitrogen deposition is increasing at RMNP –> ROMANS • Numerous approaches applied to N source apportionment at RMNP • Receptor models • Deterministic models • EOF analysis • Hybrid approach • No single technique will provide the entire answer – need to reconcile

22. Summary (cont’d) • Can’t get enough simulated N to RMNP • Nitric acid estimates not bad • PM N (NH4 and NO3) underestimated • Not capturing the late spring upslope event, although tracer transport ok • Use ‘lagrangian process analysis’ to investigate this – chemistry, deposition or emissions?

23. Summary (cont’d) • Accounting for ‘missing’ nitrogen can almost double the estimated dry deposition at RMNP for 2002 (1.2 vs 2.2 kg/ha/yr).

25. CAMx bias relative to CASTNet: HNO3

26. CAMx bias relative to CASTNet: NH4+

27. CAMx bias relative to CASTNet: NO3+