Validation Of Model Calculation Of Ammonia Deposition In The Neighbourhood Of A Poultry Farm Using Measured Nh_3 Concentrations And N Deposition

摘要

Substantial emission of ammonia (NH_3) from animal houses and the related high local deposition of NH_3-N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH_3 source. In Denmark, there are regulations limiting the level of NH_3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH_3 deposition. The models used for assessing NH_3 emission from livestock production, therefore, need to be precise, as the regulation will affect both the nature of the ecosystem and the economy of the farmer. Therefore a study was carried out with the objective of validating the Danish model used to monitor NH_3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH_3 emission with standard flux measuring methods, NH_3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using ~(15)N-enriched biomonitors and field plot studies. The dispersion and deposition of NH_3 were modelled using the Danish OML-DEP model. It was also shown that model calculations clearly reflect the measured NH_3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH_3 concentrations and showed that deposition was not significantly different from zero (P < 0.05) at distances greater than 150-200 m from these chicken houses. Calculations confirmed this, as calculated N deposition 320 m away from the chicken farm was only marginally affected by the NH_3 emission from the farm. There was agreement between calculated and measured deposition showing that the model gives true estimates of the deposition in the neighbourhood of a livestock house emitting NH_3.