Measurement and analysis of ammonia and hydrogen sulfide emissions from a mechanically ventilated swine confinement building in North Carolina

摘要

Emissions of atmospheric ammonia-nitrogen (NH_3-N, where NH_3-N = (14/17)NH_3) and hydrogen sulfide (H_2S) were measured from a finishing swine confinement house at a commercial pig farm in eastern North Carolina. Continuous simultaneous NH_3-N and H_2S emissions were made for ~l-week period during four different seasons. The number of pigs contained in the house varied from ~850 to 900 with average weights ranging from ～38 to 88 kg. Average NH_3-N concentrations were highest during the winter and spring sampling periods, 8.91 ±4.61 and 8.44 ± 2.40 ppm, respectively, and lower during the summer and fall, 2.45±1.14 and 4.27 ± 0.71 ppm, respectively. Measured average H_2S concentrations were 673 ± 282, 429 ±223, 47±18, and 304 ± 88 ppb during winter, spring, summer, and fall, respectively. Generally, the H_2S concentrations were approximately an order of magnitude less than NH_3-N during winter, spring, and fall, and two orders of magnitude smaller during the summer season.The average ambient temperature ranged from 5.5 to 22.3 ℃ while the average barn temperature measured at the outlet fans ranged from 19.0 to 26.0 ℃ in the winter and summer, respectively. The average fan ventilation rates varied from 253 m~3 min~(-1) during the fall sampling period to 1024m~3 min~(-1) during summer. Calculated total emission rates for both NH_3-N and H_2S were highest during the spring, 4519 ± 1639 g N day~(-1) and 481 ± 142gday~(-1), respectively. Emissions were lowest during the fall season for NH_3-N (904 ± 568 gN day~(-1)) and the summer season for H_2S (82 ± 49 g day~(-1)). Normalized NH_3-N emission rates were highest in winter and spring (33.6 ± 21.9 and 30.6± 11.1 g N day~(-1) AU~(-1), where 1 AU (animal unit) = 500kg) and lowest during summer and fall (24.3 ± 12.4 and 11.8±7.4 g N day~(-1) AU~(-1)). Normalized H_2S emissions were highest during the winter and spring seasons (4.2 ± 2.1 and 3.3±1.0 g day~(-1)AU~(-1)) and were lowest in summer and fall (1.2 ± 0.7 and 1.7 ± 0.5 g day~(-1) AU~(-1)).