The Importance of Ammonia in Modeling Atmospheric Transport and Deposition of Air Pollution. Organization of Talk:

Transcription

1 The Importance of Ammonia in Modeling Atmospheric Transport and Deposition of Air Pollution Organization of Talk: What is modeled Importance of NH 3 emissions to deposition Status of NH 3 emissions (model-based) Seasonality Error relative to other emissions Bi-directional exchange (new) What more is needed 2

2 Importance of NH 3 Emissions to PM 2.5 and Deposition Initial and Boundary Conditions Meteorological Model Emissions Air Quality Model Transport Gas-phase Chemistry Droplet Chemistry Wet Deposition Dry Deposition PM Chemistry and Dynamics Concentrations of gases and PM Fluxes of wet and dry deposition 3

3 VOC CO Stationary Sources, Cars, Trucks, Power Plants N2O5 HO2 RO2 NO3 OH O3 H2O Heterogeneous O3 NO NO2 HNO3 NO3 OH PMfine hv O3 Agricultural Sources Power Plants NH3 Gas Phase Fine Particles SO2 OH H2SO4 SO4 PMfine H2O2 O3 Fe Fossil Fuel Combustion that Produces Nitrogen and Sulfur Oxides (NO X and SO X ) and Agricultural Production that Produces Ammonia are are the Main Sources of Inorganic PM 2.5 and Nitrogen Deposition 4

4 Stationary Sources, Cars, Trucks, Power Plants VOC CO N2O5 HO2 RO2 NO3 OH O3 H2O Heterogeneous O3 NO NO2 HNO3 NO3 OH PMfine hv O3 Agricultural Sources Power Plants The Partitioning Between Gases and NH3 Gas Phase Fine Particles SO2 OH H2SO4 SO4 PMfine H2O2 O3 Fe Particles, Which Is Determined by Ammonia Availability, Greatly Affects Dry Deposition Rates and Concentrations of ano 3- and aso 4 = 5

5 NO X, SO 2 and NH 3 National Emissions Trends NOx and SO2 and NH3 National Emissions Trends 30.0 Tons/Year (millions) Total NO X Total SO 2 Power Plant SO 2 Power Plant NO X Total NH Year Method Change 6

6 Effect of Decreased Precursor Emissions on PM Concentrations (mg/m 3 ) SO 2 NO x VOC Sulfate Nitrate Organics 7

7 Decreased SO X and NO X Emissions Affect NH 3 Deposition Base Equally Wet Deposited NO X & SO 2 Control Wet Deposition Decreases HNO 3 Air Concentrations NH X Air Concentrations Decrease NO 3 - HNO 3 NH 3 NO 3 - SO 4 = NH 4 + SO 4 = NH 3 NH 4 + Dry Deposition Dry Deposition Increases 8

8 Decreased SO X and NO X Emissions Affect ipm 2.5 Response to NH 3 Reductions 9

9 Importance of NH 3 Emissions to ox-n + red-n Deposition Reduced-N Deposition (kg-n/ha) Fraction of N Deposition From Ammonia 10

10 Status of NH 3 Emissions: Inverse Modeling Seasonality is Very Important Run model (CMAQ ) Extract [NH 4+ ] (model and NADP locations If ΔE 0, adjust emissions globally Apply Eqn Wet Deposition Posterior NH3 Adjustment Factor jan feb mar apr may jun jul aug sep oct nov dec Month 11

11 Status of NH 3 Emissions: Inverse Modeling Seasonality is Very Important 5 (a) CASTNET CMAQ (Base) 8 CASTNET CMAQ (Base) [NH 4 ] (μg/m 3 ) [NO 3 ] (μg/m 3 ) (a) (b) CASTNET CMAQ (Adjusted) 8 CASTNET CMAQ (Adjusted) [NH 4 ] (μg/m 3 ) [NO 3 ] (μg/m 3 ) Month Month 12

12 Status of NH 3 Emissions: Precipitation-Corrected Wet Deposition SO 4 : Has the least uncertainty; good Observed vs. Modeled Wet Deposition SO 4 Observed vs. Adjusted Modeled Wet Deposition SO 4 R 2 =0.88 Model = CMAQ 12km 2002af Model values adjusted with NADP precipitation. 13

13 Color coding used for scatter plots 182 NADP monitoring sites 14

14 Status of NH 3 Emissions: Precipitation-Corrected Wet Deposition NO 3 : Intermediate; decent Observed vs. Modeled Wet Deposition NO 3 Observed vs. Adjusted Modeled Wet Deposition NO 3 R 2 =0.84 Model values adjusted with NADP Precipitation. 15

15 Status of NH 3 Emissions: Precipitation-Corrected Wet Deposition NH 4 : Has the most uncertainty Observed vs. Modeled Wet Deposition NH 4 Observed vs. Adjusted Modeled Wet Deposition NH 4 R 2 =0.68 Model values adjusted with NADP Precipitation. 16

16 Status of NH 3 Emissions: Precipitation-Corrected Wet Deposition NH 4 : Mid-Atlantic Region Best Adjusted Model Observed Wet Deposition NH 4 (kg/ha) Relative Error in Model Adjusted Wet Deposition NH 4 (%) Model values adjusted with PRISM precipitation. 17

17 NH 3 Emissions in Eastern US Dominated by Animal Operations Fraction of Total NH 3 Emissions as Emissions from Animal Operations 18

18 NH 3 Air-Surface Exchange is Bi-Directional χ a R a χc Bi-directional Model R b R w R b χ s If ambient NH3 A χ s,g then NH 3 will be taken up by the plant stomata or deposited to the soil R ac R st If ambient NH3 A χ s,g R bg χ g soil plants Compensation Points: Internal Levels of NH 4+ /H + => Air-Plant/Soil Levels of NH 3 then NH 3 will be emitted by the plant stomata or emitted by the soil 19

19 Average ammonia flux over soybeans in Eastern NC Model Observed Hour (LT) 20

20 Range of Influence: Single NC Maximum Cell BaseVd NH 3 as SO 2 Vd NH 3 Bi-Dir The Range of Influence of NH 3 Emissions is Influenced by the Dry Deposition Formulation. It Increases With a Change from the Base CMAQ M3dry to the Bi-directional Flux Formulation for NH 3 21

21 PM 2.5 May Increase a Modest Amount with Bi-Directional NH 3 Flux Inorg-PM 2.5 (Bi-Di)/Inorg-PM 2.5 (Base M3dry) June

22 What Needs to be Done? Model Complete incorporation of bi-directional flux algorithms in CMAQ Flux studies above many different vegetation types to support new parameterization Examine regional, spatial differences/biases Reexamine model guidance vis a vis ammonia Data Develop routine NH 3 flux capability for flux ground truth Better ground truth w.r.t. ammonia (NH X ) and inorganics Surface observations with ALL inorganics on hourly basis (modernize CASTNet) Get satellite retrievals working for NH 3 Compare with models to suggest inventory improvements 23

23 Acknowledgements The collaboration with colleagues in AMAD: Rob Pinder Kristen Foley Jon Pleim Rohit Mathur 24