Ammonia emissions and dry deposition in the vicinity of dairy farms

Abstract

We conducted the first research in the Czech Republic to measure ventilation and ammonia (NH₃) emission rates in a naturally ventilated animal building (dairy farm) during a five-day measurement period in June, combined with a three-month (May-July) monitoring of NH₃ concentration and dry deposition at 12 locations along horizontal gradients from the dairy farm up to the distance of 400 m. Passive diffusion-tube samplers were used to measure monthly NH₃ concentrations. Moisture (H₂O) balance was used to determine ventilation rates of the dairy farm. Continuous measurements of gas concentrations (NH₃), temperature and relative humidity inside and outside the building were performed. The air exchange rate was 4.8 h^–1 and the emission rate was 43.2 NH₃ g cow^–1 d^–1 for building. The emission rate was 126% of what was obtained using emission factors from the Czech national inventory (34.2 g cow^–1 d^–1). NH₃ concentrations and dry deposition fluxes decreased exponentially with distance from the dairy farm. Between May and July, mean predicted dry deposition fluxes ranged from 0.28 to 0.03 µg NH₃ m^–2 s^–1 at a distance of 50 and 400 m from the source, respectively. Dry NH₃ deposition over the nearest 400 m from the source accounted for 11.5% of daily emissions. The results confirm the short-range dispersion of NH₃ emitted from a point source found in other studies, but it may not be the same in other situations, since dispersion of NH₃ is dependent on the surrounding land-cover and on the number of animals in a barn.