Adaptation of a speciation sampling cartridge for measuring ammonia flux from cattle feedlots using relaxed eddy accumulation |
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| Authors: | KA Baum JM Ham |
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| Institution: | 1. Department of Agronomy, Kansas State University, Manhattan, KS 66506, USA;2. Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, USA;1. Utah Water Research Laboratory, 8200 Old Main Hill, Utah State University, Logan, UT 84322-8200, USA;2. Department of Civil and Environmental Engineering, 4110 Old Main Hill, Utah State University, Logan, UT 84322-4110, USA;3. Department of Plants, Soils and Climate, 4820 Old Main Hill, Utah State University, Logan, UT 84322-4820, USA;1. Department of Animal Science, Aarhus University, PO Box 50, DK-8830 Tjele, Denmark;2. Department of Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria;1. Department of Animal Production, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium;2. Department of Production Animals Clinic, Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium;3. Production and Sectors Department, Walloon Agricultural Research Centre, B-5030 Gembloux, Belgium;1. Utah Water Research Laboratory, 8200 Old Main Hill, Utah State University, Logan, UT 84322-8200, USA;2. Department of Civil and Environmental Engineering, 4110 Old Main Hill, Utah State University, Logan, UT 84322-4110, USA;3. Department of Plants, Soils and Climate, 4820 Old Main Hill, Utah State University, Logan, UT 84322-4820, USA |
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| Abstract: | Improved measurements of ammonia losses from cattle feedlots are needed to quantify the national NH3 emissions inventory and evaluate management techniques for reducing emissions. Speciation cartridges composed of glass honeycomb denuders and filter packs were adapted to measure gaseous NH3 and aerosol NH4+ fluxes using relaxed eddy accumulation (REA). Laboratory testing showed that a cartridge equipped with four honeycomb denuders had a total capture capacity of 1800 μg of NH3. In the field, a pair of cartridges was deployed adjacent to a sonic anemometer and an open-path gas analyzer on a mobile tower. High-speed valves were attached to the inlets of the cartridges and controlled by a datalogger so that up- and down-moving eddies were independently sampled based on direction of the vertical wind speed and a user-defined deadband. Air flowed continuously through the cartridges even when not sampling by means of a recirculating air handling system. Eddy covariance measurement of CO2 and H2O, as measured by the sonic and open-path gas analyzer, were used to determine the relaxation factor needed to compute REA-based fluxes. The REA system was field tested at the Beef Research Unit at Kansas State University in the summer and fall of 2007. Daytime NH3 emissions ranged between 68 and 127 μg m?2 s?1; fluxes tended to follow a diurnal pattern correlated with latent heat flux. Daily fluxes of NH3 were between 2.5 and 4.7 g m?2 d?1 and on average represented 38% of fed nitrogen. Aerosol NH4+ fluxes were negligible compared with NH3 emissions. An REA system designed around the high-capacity speciation cartridges can be used to measure NH3 fluxes from cattle feedlots and other strong sources. The system could be adapted to measure fluxes of other gases and aerosols. |
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