Atmospheric NH3 dynamics at a typical pig farm in China and their implications

This study investigated NH3 concentrations in and around a large–scale commercial pig farm with the so–called “gan qing fen” manure collection system near Beijing from April 2009 to August 2011. NH3 emissions from the fattening pig houses were calculated based on the heat balance method. Monthly concentrations of time–averaged NH3 in and near the pig house averaged 3 392 and 182 μg m−3 and ranged from 1 044 to 7 514 μg m−3 and 35.4 to 478 μg m−3, respectively. Daily NH3 concentrations varied from 767 to 2 389 μg m−3 in the pig house and 184 to 574 μg m−3 outside. Time–averaged NH3 concentrations varied from 21.6 to 558 μg m−3 within the farm while concentrations outside the farm ranged from 38.4 μg m−3 at a distance of 10 m to 14.0 μg m−3 at a distance of 650 m. Calculated average NH3 emission rates per pig were highest in summer and lowest in winter, 8.0 ± 5.5 (average±standard deviation) and 2.0 ± 0.4 g day−1 pig−1, respectively. Average NH3 emission rates (normalized to 500 kg live weight, expressed as AU) were highest during spring and summer (average 65.4 ± 25.0 and 53.7 ± 35.6 g day−1 AU−1) and lowest in autumn and winter (average 25.4 ± 9.3 and 13.7 ± 2.7 g day−1 AU−1). Average NH3 emission per area (m2) from house was almost three times higher in summer (average 3.5 ± 2.4 g day−1 m−2) than in winter (average 1.1 ± 0.3 g day−1 m−2).