Measurement of Ammonia Fluxes at a Cattle Feedlot Using Relaxed Eddy Accumulation

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1 Measurement of Ammonia Fluxes at a Cattle Feedlot Using Relaxed Eddy Accumulation Patrick O Keeffe Shelley Pressley Eugene Allwine Brian Lamb Kris Johnson Jennifer Michal Sarah Spogen

2 NH 3 impacts: Motivation atmosphere - major contributor to secondary aerosol formation aquatic ecosystems - deposition can lead to eutrophication Atmospheric NH 3 Sources livestock operations, fertilizer/soils, wastewater treatment facilities, industrial sources, mobile sources

3 Ammonia in our air

4 Global budget for NH3 Source Amount Tg/yr Agricultural (livestock, fertilizers, crops) 37.4 (65%) Natural or biogenic (oceans, undisturbed soils, animals) 10.7 (19%) Biomass burning 6.4 (11%) Other (industrial, wastewater facilities, fossil fuel combustion, mobile sources) Total (5%)

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6 Why at a feedlot? Recent requirements under EPA mandate all CAFO s (>1000 hd) must report NH 3 and H 2 S emissions under the Emergency Planning and Community Right to Know Act (EPCRA) Because no officially adopted emission factors are currently available to use for this purpose, the final rule allows reports to reflect good faith estimates. - users are provided a worksheet

7 Simple emission estimates using a worksheet

8 The field campaign Mid-sized cattle feedlot (30,000 head) Mid-west feedlot containing growing and finishing steers Measurements conducted during two weeks in spring Cooler temperatures; periodic rainfall; dusty Techniques: relaxed eddy accumulation (REA), ultraviolet DOAS, horizontal profiling system and mobile van outfitted with various instruments

9 Measurement Site Instrumentation location Mobile Van route Manure Compost N Feed Storage Predominant Winds (either SW or SE)

10 DOAS Differential Optical Absorption Spectrometer NH 3 concentrations measured via Beer s law Short path (110m) line-averaged nm wavelength

11 TGAPS Trace Gas Analytical Profiling System N 2 O analyzed with GC-electron capture detector (ECD) technique Same path as DOAS, time-averaged N 2 O concentrations 7 inlets, runs continuously, 5 min avg. TGAPS Sampling lines DOAS Retro-reflectors

12 Mobile Van Mobile Van Stationary or mobile sampling for CO 2, CH 4, NH 3, NO, NO 2 Mobile transects (line-averaging) or fixed time series

13 REA Relaxed Eddy 3D Sonic Anemometer REA system Accumulation TGAPS inlets REA is a micrometeorological flux measurement technique, in this case used for NH 3 flux measurements

14 REA Method High frequency sampling of wind with time averaged NH 3 concentrations Up and down wind gusts are conditionally sampled through honeycomb denuders Denuders capture NH 3 over 1 hr period and air volume sampled is known Colorimetric analysis used to determine NH 3 conc. Fluxes calculated with mean up and down concentrations of NH 3 and standard deviation of wind speed F ( + ) = σ C C wβ

15 REA NH 3 system CO 2 /H 2 O Analyzer 3D sonic Anemometer Thermo Scientific Honeycomb Denuders

16 Results REA NH 3 Fluxes collected over 4 days Wind directions dictate which portion of the feedlot was sampled Footprint lengths important, primarily dependent on stability of the atmosphere Operational parameters also important still working to incorporate this data

17 Run 11: evening E-SE winds Light winds, evening time, temperatures ~20 C NH 3 flux = 105 µg/m 2 s

18 Run 13: mid-day, S-SW winds higher winds, mid-day, temperatures ~25 C NH 3 flux = 253 µg/m 2 s

19 Run 14: mid-day, S-SW winds Temperature (C) Meterological Conditions - April temperature 25 wind speed :00 3:00 6:00 9:00 12:00 15:00 18:00 21: Wind Speed (m/s) higher winds, mid-day, temperatures ~25 C Note not to scale NH 3 flux = 352 µg/m 2 s

20 Runs Run 11

21 Summary NH 3 fluxes during warm spring conditions averaged 142±87 µg/m 2 s Emissions were from an upwind fetch of ~100 m which typically encompassed 225 hd of 400 kg growing and finishing steers. Acknowledgements USDA for research funding Jay Ham, Colorado State, for help developing REA CAFO s for allowing us to make measurements

22 Future Work Further refine the REA results Look at turbulence/atmospheric stability parameters Calculate footprint size for each run Use WindTrax atmospheric dispersion model Determine NH3 fluxes using WindTrax and DOAS for comparison with REA results Integrate results with other datasets (i.e. feedlot operations, additional measurements)