Ammonia deposition in the neighbourhood of an intensive cattle feedlot in Victoria, Australia

Abstract

Intensive cattle feedlots are large emission sources of ammonia (NH 3), but NH 3 deposition to the landscape downwind of feedlots is not well understood. We conducted the first study in Australia to measure NH 3 dry deposition within 1 km of a commercial beef cattle feedlot in Victoria. NH 3 concentrations and deposition fluxes decreased exponentially with distance away from the feedlot. The mean NH 3 concentrations decreased from 419 μg N m 3 at 50 m to 36 μg N m 3 at 1 km, while the mean NH 3 dry deposition fluxes decreased from 2.38 μg N m 2 s 1 at 50 m to 0.20 μg N m 2 s 1 at 1 km downwind from the feedlot. These results extrapolate to NH 3 deposition of 53.9 tonne N yr 1 in the area within 1 km from the feedlot, or 67.5 kg N ha 1 yr 1 as an area-weighted mean, accounting for 8.1% of the annual NH 3 -N emissions from the feedlot. Thus NH 3 deposition around feedlots is a significant nitrogen input for surrounding ecosystems. Researches need be conducted to evaluate the impacts of NH 3 deposition on the surrounding natural or semi-naturals ecosystems and to reduce N fertilizer application rate for the surrounding crops by considering nitrogen input from NH 3 deposition.