Three-dimensional characterization of the ammonia plume from a beef cattle feedlot

In Canada approximately 45% of ammonia (NH 3) emissions are attributed to dairy and beef cattle industries. The present study focused on NH 3 emissions from a beef feedlot with a one-time capacity of 17,220 head. The aim was to improve the Canadian NH 3 emission inventories and air quality forecasting capabilities. A Cessna 207, equipped with a fast-response NH 3/NO y detector and a quadrupole aerosol mass spectrometer, was flown in a grid pattern covering an area of 8 × 8 km centered on a feedlot (800 × 800 m) at altitudes ranging from 30 to 300 m above ground. Stationary ground measurements of NH 3 concentration and turbulence parameters were made downwind of the feedlot. Three flights were conducted under varying meteorological conditions, ranging from very calm to windy with near-neutral stratification. NH 3 mixing ratios up to 100 ppbv were recorded on the calm day, up to 300 m above ground. An average feedlot NH 3 emission rate of 76 ± 4 μg m −2 s −1 (equivalent to 10.2 g head −1 h −1) was estimated. Characteristics of the measured NH 3 plume were compared to those predicted by a Lagrangian dispersion model. The spatially integrated pattern of NH 3 concentrations predicted and measured agreed but the measured was often more complex than the predicted spatial distribution. The study suggests that the export of NH 3 through advection accounted for about 90% of the emissions from the feedlot, chemical transformation was insignificant, and dry deposition accounted for the remaining 10%.