AGU Fall Meeting 5 December 2012

1. An Investigation of Ammonia and Inorganic Particulate Matter in California during the CalNex Campaign AGU Fall Meeting 5 December 2012 Luke D. Schiferl, Colette L. Heald, John B. Nowak, John S. Holloway, J. Andy Neuman, RoyaBahreini, Ann M. Middlebrook, Christine Wiedinmyer, and Stuart A. McKeen Funding:

2. Gas-Particle Partitioning Transport NH3 H2SO4 HNO3 NH4+ SO42- NO3- Dry Wet SOX NH3 NOX NH3 Emissions Deposition

3. California: High Nitrogen Environment Human Population Increase from 2010 by 2020 2040 20 % 60 % 10 % 15 % [State of California, 2012] [EPA, 2011] PM2.5 SF 0 1 – 6,297 6,298 – 12,419 12,420 – 23,955 23,956 – 39,792 39,793 – 87,028 Urban + Rural N Sources LA [California Energy Commission, 2008]

4. CalNex Field Study May-June 2010 NOAA WP-3D aircraft 18 flights Altitude [km] Used in this analysis GEOS-Chem chemical transport model used to interpret observations • Driven by assimilated meteorology • 0.5° x 0.667° horizontal resolution over North America • NEI-2005 anthropogenic emissions May NH3 SOX NOX [Mg S/mo] [Mg N/mo] [Mg N/mo]

5. Comparing CalNex Observations with GEOS-Chem Simulation City Valley CalNexObs Model CalNexObs Model Valley N ≈ 800 City N ≈ 1600 Median Concentrations Shown

6. Gas-Particle Partitioning Transport NH3 H2SO4 HNO3 NH4+ SO42- NO3- Dry Wet SOx NH3 NOx NH3 Emissions Deposition

7. Simulating Gas-Particle Partitioning GEOS-Chem First… If remaining NH3… NHx SO42- TNO3 Na+ Cl- H2SO4 + NH3 ISORROPIA II NH3 NH4+ HNO3 NO3- CalNexObs Model CalNexObs Model NH4 +NO3- HNO3 + NH3 2 NH4+ SO42- f(T, RH, ions) T RH Fountoukis and Nenes [2007] GEOS-ChemT and RH v. CalNex Observations City Valley

8. Simulation is Insensitive to Temperature Uncertainty +/- 1 °C City Valley CalNexObs Model ISORROPIA +/- 1 °C CalNexObs Model ISORROPIA +/- 1°C

9. Uncertainty in RH Produces Small Differences in Ammonium Nitrate +/- 10 % RH City Valley CalNexObs Model ISORROPIA +/- 10 % RH CalNexObs Model ISORROPIA +/- 10 % RH

10. Nitrogen Deposition Dominated by Dry Removal Processes during CalNex Dry Deposition Wet Deposition Simulated N Deposition in GEOS-Chem May California June Wet Dry NH3 NH4+ HNO3 NO3- Total Deposition 11.7 [Gg N/mo] May/June Mean NHX [Mg N/mo] Virtually no summertime wet deposition confirmed by NADP measurements

11. Evaluating Dry Deposition GEOS-Chem v. CASTNET Simulated Dry Deposition Velocity CASTNET Sites CalNexObs Model Modified Model Dep 0.5x SO2Dry Deposition Velocity v. CalNex Observations City Valley City *NH3 deposition not measured by CASTNET CASTNET: May-June 2007-2009

12. Scaling Up Emissions Modified Anthropogenic Emissions All NEI-2005 Sources Livestock NH3 5x Livestock - Everywhere East LA Livestock to 12 Gg yr-1 May [Mg N/mo] Nowak et al. [2012] SO2 3x - North Valley 10x - South Valley May [Mg S/mo]

13. Increasing Emissions Reduces Model Bias in California City Valley CalNexObs Model Modified Model Emissions CalNexObs Model Modified Model Emissions

14. Improved Simulation of Near-Surface Concentrations City Valley Modified Modified Standard Standard CalNexObs CalNexObs Model Model Median, lowest 1 km

15. Implications in California Ammonia and Seasonality of PM Column Concentration Surface Concentration Export of Excess Ammonia City Valley NH3 June December Jun Dec Jun Dec Mean, lowest 1 km

16. Conclusions Emissions of ammonia and sulfur dioxide are underestimatedin California for May/June. Simulated June PM concentrations higher in LA than in the Valley;NH3 critical for this formation Reverse situation in December: LA becomes NH3 limited and Valley PM increases Excess NH3 from Valley is exported downwind in spring/summer and potential exists for additional PM formation should acid levels increase Summertime 2009 IASI Column Concentration Future Work Further exploration with NH3 satellite retrievals where observations limited Investigate impacts of simulating NH3bi-directional flux