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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #206499
Title: Challenges in using flux chambers to measure ammonia emissions from simulated open feedlot pen surfaces and retention ponds.

Author
item Cole, Noel
item Todd, Richard
item PARKER, DAVID - WEST TEXAS A&M UNIV.
item RHOADES, MARTY - WEST TEXAS A&M UNIV.

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2007
Publication Date: 9/16/2007
Citation: Cole, N.A., Todd, R.W., Parker, D.B., Rhoades, M.B. 2007. Challenges in using flux chambers to measure ammonia emissions from simulated open feedlot pen surfaces and retention ponds. In: Proceedings of the ASABE International Symposium on AIr Quality and Waste Management for Agriculture, September 16-19, 2007, Broomfield, Colorado. 2007 CD-ROM.

Interpretive Summary: Ammonia emissions from livestock feeding operations are a growing concern; however, limited data is available on these emissions. Several methods are available to estimate ammonia emissions, but few have been adequately validated for accuracy. Dynamic, flow-through flux chambers are sometimes used to measure ammonia losses from lagoons and pens. However, ammonia emissions from the surfaces are affected by atmospheric turbulence, atmospheric ammonia concentration, source strength, temperature, moisture, and media pH. Because several of these can be affected by the presence of the chamber, the chamber may alter the microenvironment and thus alter ammonia flux rates. We conducted two to compare measured ammonia nitrogen losses from an 'unaffected' source to the same source when the air exchange rate through the chamber ranged from 0 to 4 turnovers per minute. A liquid ammonium sulfate buffer solution was used to simulate a feedlot retention pond, and a feedlot surface was simulated by adding an ammonium sulfate buffer solution to purified cellulose. Ammonia nitrogen losses from both simulated surfaces increased with increased air flow. Losses at 4 turnovers per minute were approximately 50% of losses from open-unaffected containers. Air turnover rates of 10 to 15 per minute were required to obtain values similar to the unaffected chambers. Because the surface of feedlot pens is highly variable, the number of samples required to obtain accurate results is also large, ranging form 30 to 265. These studies demonstrate that ammonia flux values obtained using chambers must be evaluated carefully and that chambers should be validated before use in experiments.

Technical Abstract: Ammonia emissions from livestock feeding operations are a growing concern; however, limited data is available on these emissions. Several methodologies are available to estimate ammonia emissions, but few have been adequately validated for accuracy. Dynamic, flow-through flux chambers are sometimes used to measure ammonia losses from lagoons and pens. However, ammonia emissions from the surfaces are affected by atmospheric turbulence, atmospheric ammonia concentration, source strength, temperature, moisture, and media pH; several of which can be affected by the chamber. Studies have shown that ammonia emissions estimated using flow-through chambers are affected by air exchange rate; however, these chamber fluxes have not been directly compared to the flux from the same source when unaffected by a chamber. In two studies we compared measured ammonia losses from an 'unaffected' source to the same source when the air exchange rate ranged from 0 to 4 turnovers per minute. To simulate a feedlot retention pond, buffered ammonium sulfate solutions with pH values of 7.5, 8.5, or 9.5 were used as a surrogate ammonia source. To simulate a feedlot surface, the buffer solutions were added to a cellulose media. With both simulated retention pond and pen surfaces, ammonia losses increased with increased air flow. Losses at 4 turnovers per minute were approximately 50% of losses from open-unaffected containers. Losses at 0.5 turnovers per minute were 20% or less of losses from the unaffected sources. At low flow rates source strength differences were sometimes not accurately determined. The CV for ammonia emissions from a 156 m**2 experimental feedlot pen (Koziel et al., 2005; Rhoades et al., 2005) was 132%. Thus, the number of samples required to be 95% confident that the estimated mean is within 20% of the true mean (determined as CV**2/100: Klenbusch, 1986) was approximately 174, or one sample per m**2 of pen surface.