Open-path eddy covariance measurements of ammonia fluxes from a beef cattle feedlot

Kang Sun, Lei Tao, David J. Miller, Mark Andrew Zondlo, Kira B. Shonkwiler, Christina Nash, Jay M. Ham

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Eddy covariance (EC) measurements of NH3 fluxes from a cattle feedlot were made with a high-precision, fast-response (20Hz) open-path laser-based sensor. The sensor employed a continuous wave, quantum cascade (QC) laser and targeted an isolated absorption feature of NH3 at 9.06μm. It was deployed on a 5-m tall flux tower beside a 22,000-animal cattle feedlot in Colorado, USA for two weeks. Sensible heat, latent heat, CO2, and CH4 EC fluxes were measured concurrently on the tower. The open-path NH3 sensor showed a comparable time response to well-established commercial open-path sensors for CO2 and H2O. The average high-frequency flux loss over the measurement period was 6.6%, mainly resulting from sample path averaging. The sensor showed significant improvement over NH3 EC fluxes measured by closed-path sensors. The measured NH3 EC fluxes were well-correlated with latent heat EC fluxes. During the measurement period, the average daily NH3 EC flux was 31.7kgha-1d-1. The flux-variance relationship was used to further validate the performance of the NH3 EC flux measurement. A 1σ detection limit of 1.3±0.5ngm-2s-1 for NH3 fluxes measured in 30-min intervals was achieved in this field test. This suite of measurements enabled the evaluation of livestock NH3 emissions at unprecedented temporal resolution and accuracy in the context of other important agricultural trace gases.

Original languageEnglish (US)
Pages (from-to)193-202
Number of pages10
JournalAgricultural and Forest Meteorology
StatePublished - Nov 1 2015

All Science Journal Classification (ASJC) codes

  • Forestry
  • Global and Planetary Change
  • Agronomy and Crop Science
  • Atmospheric Science


  • Cattle feedlot
  • NH<inf>3</inf> flux
  • Open-path eddy covariance
  • Quantum cascade laser


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