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, Roya Bahreini, Ann M. Middlebrook, Christine Wiedinmyer, and Stuart A. McKeen Funding:

2. NH 3 SO X NO X Emissions Gas-Particle Partitioning NH 3 H 2 SO 4 HNO 3 NH 4 + SO 4 2- NO 3 - Deposition Dry Wet Transport NH 3

3. California: High Nitrogen Environment PM 2.5 Human Population Increase from 2010 by 2020 2040 20 % 10 % 60 % 15 % [State of California, 2012] 0 1 – 6,297 6,298 – 12,419 12,420 – 23,955 23,956 – 39,792 39,793 – 87,028 [California Energy Commission, 2008] [EPA, 2011] LA SF Urban + Rural N Sources

4. CalNex Field Study May-June 2010 NOAA WP-3D aircraft 18 flights SpeciesMeasurement TechniqueResolution NH 3 chemical ionization mass spectrometry 1 s SO 2 pulsed UV fluorescence HNO 3 chemical ionization mass spectrometry NH 4 + aerosol mass spectrometry 10 s SO 4 2- NO 3 - 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 SO X Altitude [km] NH 3 NO X [Mg N/mo] May [Mg S/mo] [Mg N/mo]

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

6. NH 3 SO x NO x Emissions Gas-Particle Partitioning NH 3 H 2 SO 4 HNO 3 NH 4 + SO 4 2- NO 3 - Deposition Dry Wet Transport NH 3

7. Simulating Gas-Particle Partitioning ISORROPIA II NH x SO 4 2- TNO 3 Na + Cl - T RH NH 3 NH 4 + HNO 3 NO 3 - GEOS-Chem H 2 SO 4 + NH 3 HNO 3 + NH 3 2 NH 4 + SO 4 2- NH 4 + NO 3 - If remaining NH 3 …First… f(T, RH, ions) GEOS-Chem T and RH v. CalNex Observations ValleyCity Fountoukis and Nenes [2007] CalNex Obs Model CalNex Obs Model

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

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

10. Simulated N Deposition in GEOS-Chem Nitrogen Deposition Dominated by Dry Removal Processes during CalNex Wet Deposition Dry Deposition May June California Wet Dry NH 3 NH 4 + HNO 3 NO 3 - Total Deposition 11.7 [Gg N/mo] Virtually no summertime wet deposition confirmed by NADP measurements NH X May/June Mean [Mg N/mo]

11. GEOS-Chem v. CASTNET Simulated Dry Deposition Velocity Evaluating Dry Deposition CASTNET: May-June 2007-2009 0.5x SO 2 Dry Deposition Velocity v. CalNex Observations City Valley City CalNex Obs Model Modified Model Dep CASTNET Sites *NH 3 deposition not measured by CASTNET

12. Scaling Up Emissions All NEI-2005 Sources Livestock 5x Livestock - Everywhere East LA Livestock to 12 Gg yr -1 3x - North Valley 10x - South Valley NH 3 SO 2 Modified Anthropogenic Emissions Nowak et al. [2012] [Mg N/mo] May [Mg S/mo] May

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

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

15. Implications in California Surface Concentration Column Concentration June December Jun Dec Mean, lowest 1 km CityValley Jun Dec Export of Excess Ammonia Ammonia and Seasonality of PM NH 3

16. Conclusions Further exploration with NH 3 satellite retrievals where observations limited Investigate impacts of simulating NH 3 bi-directional flux Emissions of ammonia and sulfur dioxide are underestimated in California for May/June. Simulated June PM concentrations higher in LA than in the Valley; NH 3 critical for this formation Reverse situation in December: LA becomes NH 3 limited and Valley PM increases Excess NH 3 from Valley is exported downwind in spring/summer and potential exists for additional PM formation should acid levels increase Future Work Summertime 2009 IASI Column Concentration