Measurement of Ammonia Concentrations and Fluxes: Recent Examples Using Denuder and Chemiluminescence Technologies

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1 Measurement of Ammonia Concentrations and Fluxes: Recent Examples Using Denuder and Chemiluminescence Technologies John Walker U.S. Environmental Protection Agency National Risk Management Research Laboratory Air Pollution Prevention and Control Division Research Triangle Park, NC NADP Annual Technical Committee Meeting and Ammonia Workshop, 2-22 October 23, Washington, D.C.

2 Research and Development at EPA 1,9 employees $7 million budget $1 million extramural research grant program 13 lab or research facilities across the U.S. Credible, relevant and timely research results and technical support that inform EPA policy decisions

3 Making decisions with sound science requires.. Relevant, high quality, cutting-edge research in human health, ecology, pollution control and prevention, economics and decision sciences Proper characterization of scientific findings Appropriate use of science in the decision process Research and development contribute uniquely to.. Health and ecological research, as well as research in pollution prevention and new technology In-house research and an external grants program Problem-driven and core research

4 High Priority Research Areas Human Health Particulate Matter Drinking Water Clean Water Global Change Endocrine Disruptors Ecological Risk Pollution Prevention Homeland Security

5 Ammonia Research within U.S.EPA/NRMRL/APPCD Development of Emission Factors for Animal Production Bruce Harris, Richard Shores, and Susan Thorneloe Swine, Poultry, Cattle OP-FTIR/TDL with computed tomography Natural emissions, atmospheric chemistry and deposition John Walker Spatio-temporal variability in NH 3 /NH x, air/surface exchange over crops, soil emissions NH 3 NH 4 +

6 Outline Annular Denuder Ambient monitoring in eastern North Carolina Chemiluminescence NH 3 Analyzer Air/surface exchange of NH 3 Passive Denuder Spatial gradients in the vicinity of a swine production facility NH 3 NH 4 +

7 Ambient Ammonia and Ammonium Aerosol across an Area of Variable Ammonia Emission Density Co-authors Wayne Robarge North Carolina State University, Department of Soil Science, Raleigh, NC 2769 Dave R. Whitall Center for Coastal Monitoring and Assessment, NOAA, Silver Spring, MD 291 Hans W. Paerl University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC 287 NH 3 NH 4 +

8 Background: Ammonia in North Carolina Eastern North Carolina contains some of the highest county-scale NH 3 emission rates in the U.S. (Sampson and Duplin Counties; Strader et al., 21). Livestock and fertilizer account for 9% (116, tons N) of statewide NH 3 emissions. NH 3 NH 4 +

9 Background Objective: Measurement of ambient NH 3, NH 4+, HCl, Cl -, HNO 3, NO 3-, SO 2, SO 4 2-, and HONO concentrations at sites in eastern NC. Period: 2 Sites County-Scale Emission Density (kg NH 3 km -2 ) Clinton 48 Kinston 228 Morehead City 32 NH 3 NH 4 +

10 2 County-Scale NH 3 Emissions (CMU V2.) * * * Emission Density (kg NH 3 km -2 ) < to 7 7 to 1 1 to 1 1 to 2 2 to 3 3 to > Morehead City Kinston Clinton N

11 Methods Teflon Filter Pack Contains Teflon and nylon Filters capture fine particulates containing ammonium and other species. AIR FLOW Denuder Tube Concentric cylinders of etched glass are coated with citric acid. NH 3 molecules are retained in this section. Denuder Tube Concentric cylinders of etched glass are coated with sodium carbonate (base). Acid molecules (HCl, HONO, HNO 3, SO 2 ) are retained in this section. Air Intake Cyclone Stops particulates >2. mm in size from entering annular denuder system. Schematic of assembled annular denuder system

12 Results: Annual Concentrations 6 \\\ Clinton xx Kinston // Morehead City 4 ug m NH 3 SO 2 HNO 3 HONO HCl NH 4 + NO 3 - SO 4 = Cl Gas Aerosol

13 Results: Ammonia/Ammonium Fractionation NH 3 /(NH 3 +NH 4 + ) W Sp Su F W Sp Su F W Sp Su F Clinton Kinston Morehead City Percent Percent Kinston Spring/Summer Wind Direction Kinston Fall/Winter Wind Direction

14 Results: Inorganic PM 2. ug m SO = 4 NO - 3 NH + 4 Cl W Sp Su F W Sp Su F W Sp Su F Clinton Kinston Morehead City

15 Results: Aerosol Formation + = Excess NH3 = NH + NH SO NO HNO Cl HCl 4 Excess NH 3 (nmol m -3 ) W Sp Su F W Sp Su F W Sp Su F Clinton Kinston Morehead City

16 Conclusions At the three sites investigated in this study, ambient levels of NH 3 and inorganic PM 2. exhibit a positive correlation with local NH 3 emission density. NH 4+ aerosol formation appears to be acid-gaslimited at the Clinton site during all seasons and during the spring and summer at the Kinston site. NH 4+ aerosol formation may, therefore, be more sensitive to changes in SO 2 and NO x emissions reductions in NH 3 enriched areas. NH 3 NH 4 +

17 Air Surface Exchange of NH 3 over Agricultural Crops Objective: Measurement of NH 3 exchange over soybean, corn and winter wheat using the modified Bowen ratio approach. Period: Site: Duplin County, NC Coastal Plain NH 3 NH 4 +

18 Theory Eddy Covariance F y = w y K-theory y = momentum (u), heat (θ), mass (c) F y = K y dy dz In this case, y = H 2 O v, CO 2, and θ Modified Bowen-ratio F NH = 3 K y dnh dz 3 NH 3 NH 4 +

19 Methods: Equipment NH 3 gradient Chemiluminescence CO 2 /H 2 O gradient LI6262 Temperature gradient Thermocouple Eddy Covariance CO2/H2O/Heat fluxes - LI7/Gill Windmaster Pro Inlet Heights 1 and 6m 1 min. switching time Heated sample lines Hourly gradients Hourly - RH PAR/Net radiation Rainfall Soil volumetric water Soil heat flux Weekly - LAI Leaf total N Soil extractable NH 4+ /NO 3 - NH 3 flux tower - Duplin Co., NC

20 Methods: Tower NH 3 Configuration Upper Inlet Heated Sample Line 8. Lpm Mobile Lab Solenoid Valve 6.2 m NH 3 Analyzer Lower Inlet N t Converter 11.4 m

21 Methods: Chemiluminescence NOx Inlet N t Converter N t NOx Converter PMT NO Rx Cell N t Converter Module NH 3 /NOx/NO Analyzer N t converter at 82 o C converts NHx + NOx to NO NOx converter at 32 o C converts NOx to NO Routine calibration with NO standard Converter efficiency test with NH 3 standard Converter efficiency typically 6 8% NH 3 NH 4 +

22 Methods: Gradient Detection Limit 6 Analyzer Precision %CV (1 Min. Ave.) 4 3 y = 8.84x R 2 = y = x -.98 R 2 = NH 3 (ppb) Converter 1 Converter 2 Power (Converter 1) Power (Converter 2) NH3 + NH H 1 3H 2 D. L.(% Diff.) =

23 Methods: Response Time Zero Air Off at Tower Inlet NH3 (ppb) Seconds NH3 (ppb) Zero Air On at Tower Inlet Seconds

24 Methods: Instrument Comparison Concentrations 2 2 Analyzer 1 Analyzer 2 NH3 (ppb) 1 1 Hour DOY

25 Methods: Instrument Comparison Gradients DOY 29 3 Analyzer 2 NH3 Gradient (ppb) :1-3 Analyzer 1 NH 3 Gradient (ppb)

26 Methods: NH 3 Gradients 22 Soybean Cumulative Percent % of gradients were > detection limit N = Ratio of Gradient to Detection Limit

27 Results: Hourly NH 3 Concentrations 22 Soybean 6 P e r c e n t NH 3 (ug m -3 )

28 Results: NH 3 Gradients and Fluxes 22 Soybean NH 3 gradient and flux - DOY NH3 Gradient (ug/m 3 ) NH3 flux (ug/m 2 /s) -3 Hour -.1 Net flux = -12 ng NH 3 -N/m 2 /s V d = -.3 cm/s NH3grad NH3 flux

29 Ammonia Concentrations Within the Vicinity of a Swine Production Facility Objectives: Measurement of horizontal NH 3 gradients around a swine production facility from the housing/lagoon complex to m. Estimation of NH 3 dry deposition using the resistance approach (Fowler et al., 1998) and Gaussian modeling. Development of a mass balance using measured emissions (Harris et al., 21). NH 3 NH 4 +

30 Site Layout N NH 3 Sampler Met. Station Lagoon Hog House m

31 Methods [NH 3 ] = Q/V Q = Mass of NH 3 adsorbed V = Volume of air sampled Sutton et al., 21 Q = (c e c b )v C e Measured NH 3 concentration C b Blank value V Extract volume (2. ml) V = D A t/l D Diffusion coefficient A Area of adsorbing surface t Duration of exposure (1 week) L Length of diffusion path (3 mm)

32 Methods Deposition F NH3 = [NH 3 ] V d V d = 1/(R a + R b + R c ) R c will be calculated using the relationship between R c and [NH 3 ] (Fowler et al., 1998) and Gaussian modeling. R b R b = (2/(ku * ))(Sc/Pr) 2/3 R a Ra = U/(u * ) 2 u * is determined using velocity profile (crops) and eddy covariance (forest) approaches

33 Methods Calibrate using NH 3 standard in flow-through chamber and by comparison with annular denuder. Results Measurements began April 23 Median C.V. = 6.4% (N = 236) Mean Blank = 2.7 µg NH 3 m -3 (N = 86) NH 3 NH 4 +

34 Results NH 3 (ug m -3 ) O O O O O OO O O O Extensions represent 9% C.I. for mean concentration. O O O O OO O O OO O O Distance from House/Lagoon (m)

35 Summary Annular Denuder Multiple analytes, selective, well documented Integrated sample, labor intensive, relatively expensive Chemiluminescence Good temporal resolution, easily calibrated, relatively inexpensive Aerosol interference Passive Denuder Inexpensive, allows greater spatial resolution, selective Single analyte, integrated sample, requires calibration NH 3 NH 4 +

36 Acknowledgements North Carolina Division of Air Quality, North Carolina Pork Council, National Pork Producers Council, and North Carolina Water Resources Research Institute. Wayne Fowler (U.S. EPA), Lynette Mathis (North Carolina State University), Mark Barnes (North Carolina State University), and Brad Hendrickson (UNC-CH IMS). NH 3 NH 4 +