Airborne observations of ammonia emissions from agricultural sources and their implications for ammonium nitrate formation in California

Transcription

1 Airborne observations of ammonia emissions from agricultural sources and their implications for ammonium nitrate formation in California CalNex 2010 P-3 Observations South Coast Air Basin (SoCAB) Dairy Emissions NH 3 Central Valley NH 3 Distribution Central Valley Dairy NH 3 Flux J.B. Nowak 1,2*, J.A. Neuman 1,2, R. Bahreini 1,2, A. M. Middlebrook 2, C.A. Brock 2, G. J. Frost 1,2, J.S. Holloway 1,2, S.A. McKeen 1,2, J. Peischl 1,2, I.B. Pollack 1,2, J.M. Roberts 2, T.B. Ryerson 2, M. Trainer 2, and D.D. Parrish 1,2 1 CIRES, University of Colorado, Boulder, CO 2 NOAA-ESRL, Chemical Sciences Division, Boulder, CO *John.Nowak@noaa.gov

2 California NH 3 Emissions Visible From Space Nature Geoscience, July 2009 NH 3 from IASI/MetOp satellite Also satellite NH 3 observations from the TES instrument Agricultural NH 3 emissions are visible from space Clarisse et al., Nature Geoscience, 2009

3 California NH 3 Area Emissions EPA NEI 1999v3 (Frost et al., JGR 2006) All area sources Point sources excluded 4 km resolution Grid emissions < 0.05 tons/day not shown Central Valley Agriculture SoCAB Agriculture Cars

4 Importance of Ammonia in the Atmosphere NH 3 typically most abundant atmospheric gas-phase base Water soluble and readily absorbed to surfaces, i.e., vegetation and soil Often major component of tropospheric aerosol as NH 4 + NH 3 + HNO 3!NH 4 NO 3 Ammonium Nitrate 2NH 3 + H 2 SO 4 "(NH 4 ) 2 SO 4 Ammonium Sulfate NH 3 + HCl"NH 4 Cl Ammonium Chloride

5 Importance of Ammonia in the Atmosphere NH 3 typically most abundant atmospheric gas-phase base Water soluble and readily absorbed to surfaces, i.e., vegetation and soil Often major component of tropospheric aerosol as NH 4 + NH 3 + HNO 3!NH 4 NO 3 Ammonium Nitrate NH 4 NO 3 equilibrium dependent on NH 3 HNO 3 Temperature Aerosol phase and composition

6 CalNex 2010 (May and June) Research at the Nexus of Air Quality and Climate Change NH 3 - Chemical Ionization Mass Spectrometry (CIMS) Nitric acid (HNO 3 ) - CIMS Aerosol composition - Aerodyne Aerosol Mass Spectrometer (C-ToF-AMS) Carbon monoxide (CO) - Vacuum UV Resonance Fluorescence Methane (CH 4 ) Cavity Ring Down Spectroscopy (Picarro CO 2 /CH 4 ) 1 s time resolution measurements correspond to ~ 100 m spatial resolution

7 P-3 NH 3 CIMS Instrument Chemical Ionization Mass Spectrometry (CIMS) uses ion-molecule reactions to selectively react gas-phase species of interest to an easily detectable product ion. (Nowak et al., JGR, 2007, 2010) (C 3 H 6 O) 2 H + + NH 3 " (C 3 H 6 O) 2 H + NH 3 Sensitivity - 1± 0.5 Hz/pptv (for 1 MHz reagent ion) Background to 1 ppbv (varied flight-to-flight) Time Response - 1 s Uncertainty - ± (30% + (0.100 to 0.200) ppbv)

8 P-3 NH 3 Sampling Strategy Dairy locations from Salas et al., PIER Report, 2008 Flight tracks May 7 SJV May 14 LA 6 daytime flights in the Central Valley 7 daytime flights through the SoCAB

9 CalNex NH 3 Altitude Profile 100 pptv ~ 1 ppmv Highest near surface First in-situ profiles concurrent with satellite observations NEAQS 2004 BL mixing ratios up to 3 ppbv Biomass burning layers at altitude (Nowak et al., JGR 2007) TexAQS 2006 BL mixing ratios up to 8 ppbv BL plumes from industrial accident (Nowak et al., JGR 2010)

10 South Coast Air Basin Dairy Farm NH 3 May 14 Flight Track Wind Direction Estimate NH 3 dairy flux from crosswind transects

11 SoCAB Dairy Farm NH 3 Mass Flux Calculation flux m =v!cos(!) "n(z)dz " X m (y)dy Standard method, White et al., Science, 1976 Wind speed Aircraft track correction Atmospheric number density over the boundary layer height Integral of the observed plume Factor of 2 uncertainty Three crosswind transects May 14 (two transects) 112 ± 56 metric tons/day and 120 ± 60 metric tons/day May ± 14 metric tons/day

12 SoCAB NH 3 Emissions From Inventories May 14 Flight Track Wind Direction Compare estimated NH 3 flux to inventory emissions EPA National Emissions Inventory 2005 (NEI-05) CARB ARCTAS 2008 (CARB-ARCTAS 08)

13 Estimated SoCAB NH 3 Fluxes Compared to Emission Inventories Dairy Farm Flux (metric tons day -1 ) NEI-05 CARB-ARCTAS 08 CalNex to ± 14 to 120 ± 60 Large variation in limited observations. NH 3 emissions in both inventories are lower than observations. If air quality models do not simulate NH 3 correctly, then they likely will not simulate inorganic aerosol. NH 3 emissions from automobiles in SoCAB ~ 38 metric tons day -1. On going work Evaluate emissions inventories Evaluate air quality models

14 Consequence of NH 3 emissions - NH 4 NO 3 May 14 Flight Track Wind Direction

15 Consequence of NH 3 emissions - NH 4 NO 3 NH 3 and HNO 3 anti-correlated NO 3 - increased indicating NH 4 NO 3 formed ~10x more NO 3 - than in upwind transects

16 Different Look At SoCAB Dairy Farm NH 3 May 19 Flight Track Wind Direction

17 NH 3 at 200m nearly 1 ppmv NH 3 and HNO 3 anti-correlated over short distance scales High NH 3 depletes HNO 3

18 Of course, dairies emitted more than NH 3 CH 4 enhanced in dairy farm plume and correlated with NH 3

19 SoCAB CH 4 vs. NH 3 Correlation Plot

20 Central Valley NH 3 Observations Sacramento Valley May 7 Southern SJV May 11 Sacramento Valley May 12 Northern SJV NH 3 peaks at 963 ppbv San Joaquin Valley

21 Central Valley HNO 3 Observations Sacramento Valley May 7 Southern SJV May 11 Sacramento Valley May 12 Northern SJV HNO 3 peaks at 3 ppbv San Joaquin Valley

22 Central Valley NO 3 - Observations May 7 Southern SJV NO 3 - ~1 ppbv San Joaquin Valley Despite abundance of NH 3, NO 3 - loading relatively small due to lack of HNO 3

23 Central Valley NH 3 Dairy Farm Time Series

24 Central Valley NH 3 Dairy Farm Time Series Enhancements from individual farms seen in NH 3 data

25 Central Valley NH 3 Dairy Farm Time Series Enhancements from individual farms seen in NH 3 data NH 3 and CH 4 correlated

26 Central Valley Farm from P-3

27 SoCAB and Central Valley CH 4 vs. NH 3 Different CH 4 to NH 3 relationship in the SoCAB and Central Valley

28 May 12 th Northern San Joaquin Valley

29 NH 3 Vertical Distribution Snapshot May 12 th stacked cross valley transects

30 Integrated NH 3 Flux Estimates

31 Integrated NH 3 Flux Estimates

32 Integrated NH 3 Flux Estimates Compare to inventory emissions from box

33 Integrated NH 3 Fluxes Compared to Inventories Integrated flux through box from P-3 ~ 550 metric tons/day

34 Integrated NH 3 Fluxes Compared to Inventories Integrated flux through box from P-3 ~ 550 metric tons/day Both inventories much lower than estimates from observations

35 Summary NH 3 mixing ratios high frequently over 10 ppbv, plumes up to 963 ppbv Estimated SoCAB dairy farm flux 27 to 120 metric tons/ day Inventories appear to underestimate dairy NH 3 in the SoCAB Central Valley cross valley integrated dairy farm fluxes estimated up to 622 metric tons/day on May 12. Despite abundance of NH 3 in the Central Valley, observed NO 3 - levels are low due to the lack of HNO 3. The relationship between CH 4 and NH 3 appears to differ in the SoCAB and Central Valley.

36 The End