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, October 2003, Washington, D.C.

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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 +

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 +

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 Dave R. Whitall Center for Coastal Monitoring and Assessment, NOAA, Silver Spring, MD Hans W. Paerl University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, NC NH 3 NH 4 +

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., 2001 ). Livestock and fertilizer account for 90% (116,000 tons N) of statewide NH 3 emissions. NH 3 NH 4 +

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: 2000 NH 3 NH 4 +

* * * Morehead City Kinston Clinton N

Teflon Filter Pack Contains Teflon and nylon Filters capture fine particulates containing ammonium and other species. 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. Cyclone Stops particulates >2.5  m in size from entering annular denuder system. AIR FLOW Air Intake Schematic of assembled annular denuder system Methods

Results: Annual Concentrations

Results: Ammonia/Ammonium Fractionation

Results: Inorganic PM 2.5

Results: Aerosol Formation

Conclusions At the three sites investigated in this study, ambient levels of NH 3 and inorganic PM 2.5 exhibit a positive correlation with local NH 3 emission density. NH 4 + aerosol formation appears to be acid-gas- limited 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 +

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: 2002 – 2003 Site: Duplin County, NC Coastal Plain NH 3 NH 4 +

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

Methods: Equipment NH 3 flux tower - Duplin Co., NC NH 3 gradient – Chemiluminescence CO 2 /H 2 O gradient – LI6262 Temperature gradient – Thermocouple Eddy Covariance CO2/H2O/Heat fluxes - LI7500/Gill Windmaster Pro Inlet Heights – 1 and 6m 15 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 -

Solenoid Valve Mobile Lab Lower Inlet Upper Inlet Heated Sample Line 8.5 Lpm N t Converter NH 3 Analyzer Methods: Tower NH 3 Configuration 6.2 m 11.4 m

Methods: Chemiluminescence Routine calibration with NO standard Converter efficiency test with NH 3 standard Converter efficiency typically 65 – 85% Inlet N t Converter Module NH 3 /NOx/NO Analyzer N t Converter NOx Converter Rx Cell PMT N t converter at 825 o C converts NHx + NOx to NO NOx converter at 325 o C converts NOx to NO NtNt NOx NO NH 3 NH 4 +

Methods: Gradient Detection Limit

Methods: Response Time

Hour DOY Methods: Instrument Comparison Concentrations

Methods: Instrument Comparison Gradients 1:1 DOY 209

Methods: NH 3 Gradients 2002 Soybean 85% of gradients were > detection limit N = 2771

Results: Hourly NH 3 Concentrations 2002 Soybean

Results: NH 3 Gradients and Fluxes 2002 Soybean Net flux = -12 ng NH 3 -N/m 2 /s V d = cm/s

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 500 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., 2001). NH 3 NH 4 +

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

Methods Q = (c e – c b )v C e – Measured NH 3 concentration C b – Blank value V – Extract volume (2.5 ml) [NH 3 ] = Q/V V = DAt/L D – Diffusion coefficient A – Area of adsorbing surface t – Duration of exposure (1 week) L – Length of diffusion path (35 mm) Q = Mass of NH 3 adsorbed V = Volume of air sampled Sutton et al., 2001

Methods Deposition F NH 3 = [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

Results Measurements began April 2003 Median C.V. = 6.4% (N = 236) Mean Blank = 2.7  g NH 3 m -3 (N = 86) NH 3 NH 4 + Methods Calibrate using NH 3 standard in flow-through chamber and by comparison with annular denuder.

Results Extensions represent 95% C.I. for mean concentration.

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 +

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 +