Submitted to: Popular Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2006
Publication Date: 5/6/2006
Citation: Baek, B., Todd, R.W., Cole, N.A., Koziel, J. 2006. Ammonia and hydrogen sulfide flux and dry deposition velocity estimates using vertical gradient method at a commercial beef cattle feedlot. International Journal Global Environmental Issues. 6(2-3):189-203. Interpretive Summary: Ammonia and hydrogen sulfide emissions from livestock feeding operations are a growing concern for producers, regulators and the general public. Measuring emissions from livestock operations such as beef cattle feedyards is difficult because fences, buildings, livestock and other items can disrupt air flow. In this experiment, ammonia and hydrogen sulfide flux and dry deposition velocity were estimated at a commercial 50,000 head beef cattle feedyard in Texas using a micrometeorological technique called the vertical flux gradient method. A tower was erected in a feed pen near the center of the feedyard. Wind speed and temperature were measured at 5 heights from 1.5 to 6 meters. Ammonia and hydrogen sulfide concentrations were measured at heights of 3 and 6 meters. During the summer, ammonia emission rate averaged approximately 3,795 kg per day and during the winter averaged 329 kg per day. Mean hydrogen sulfide emission rates were 22.5 kg per day during the summer. Ammonia emissions had a diurnal pattern and were highly correlated to ambient temperature. Ammonia emissions were similar to N volatilization losses estimated using changes in ration and manure N:P ratios. These results demonstrate that ammonia emissions from feedyards are highly correlated to temperature and that the flux gradient method can potentially be used to measure ammonia and hydrogen sulfide emission from feedyards.
Technical Abstract: Ammonia and hydrogen sulfide flux and dry deposition velocity were estimated using micrometeorological vertical gradient flux method at a commercial cattle feedyard of approximately 50,000 head of beef cattle and average 14.4 m2/head (150 ft2/head) stocking density. During summertime, NH3-N emission rate averaged approximately 3,795 kg NH3-N'd-1 and 329 kg NH3-N'd-1 during wintertime. Mean H2S-S emission rate was 22.5 kg H2S-S'd-1 during 2004 Summer. We found that there are exponential relationship between NH3-N flux and ambient temperature with R2 = 0.57 for NH3 (NH3–N flux = -1.46 + 7.96e0.077*Temperature) and R2 = 0.22 for H2S-S (H2S-S flux = -0.75 + 0.8e-0.013*Temperature). Ammonia-N and H2S-S loss had general diurnal patterns with the highest fluxes in daytime and lowest fluxes in nighttime that correlated to temperature changes and active evaporation process during daytime. The highest average deposition velocities also occurred during daytime with unstable atmospheric conditions and the lowest during nighttime with very stable conditions.