@article {74,
	title = {A simple model for assessing ammonia emission from ammoniacal fertilisers as affected by pH and injection into soil},
	journal = {Atmospheric Environment},
	volume = {42},
	year = {2008},
	pages = {4656-4664},
	abstract = {Ammonia (NH3) volatilisation following the application of ammoniacal fertilisers and liquid manure to agricultural land is a significant source of atmospheric NH3, which not only poses a risk to the environment, but may also result in a loss of plant available nitrogen (N). This study examined the potential for reducing NH3 emission through acidifying an ammoniacal solution and by injecting the solution. The combination of the two technologies was studied and a model for predicting the most optimal treatment was developed. In the laboratory, ammonium (NH4 +) hydroxide (aqueous NH3) was dissolved in water (pH 11) and injected into a loamy sand soil. The NH3 emission was measured with a dynamic chamber technology. Injecting the solution to 10mm below the soil surface reduced NH3 emission by 10\% compared to surface application, and injection to 30mm reduced emission by 20\% compared to surface application. Acidifying the ammoniacal solution by adding sulphuric acid and reducing pH to 10 reduced the emission by 60\% at a 10mm injection depth and 90\% at 30mm compared with non-acidified and surface-spread ammoniacal solution. The results show that there is an important interaction of pH and injection depth and that there is a need for models predicting a combined effect. This type of model could contribute to reduce cost and energy (traction force) by providing the optimal combination of acidifying and injection depth that gives a specific reduction in NH3 emission, which in this study was reducing pH to 10 and inject the fertiliser to 30mm below surface. This study showed that relatively simple models can predict the NH3 emission from injected ammoniacal fertilisers, but that there is still a need for developing algorithms that predict the effect of pH, including the pH buffering capacity of the fertiliser and the soil.},
	keywords = {EPNB},
	author = {Nyord, T and Schelde, K. M and Sogaard, K. T and Jensen, L. S and Sommer, S. G}
}
@article {72,
	title = {Validation of model calculation of ammonia deposition in the neighbourhood of a poultry farm using measured NH3 concentrations and N deposition},
	journal = {Atmospheric Anvironment},
	volume = {43},
	year = {2008},
	abstract = {Substantial emission of ammonia (NH3) from animal houses and the related high local deposition of NH3- N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH3 source. In Denmark, there are regulations limiting the level of NH3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH3 deposition. The models used for assessing NH3 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 NH3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH3 emission with standard flux measuring methods, NH3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using 15N-enriched biomonitors and field plot studies. The dispersion and deposition of NH3 were modelled using the Danish OML-DEP
model. It was also shown that model calculations clearly reflect the measured NH3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH3 concentrations and showed that deposition was not significantly different from zero (P < 0.05) at distances greater
than 150{\textendash}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 NH3 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 NH3},
	keywords = {EPNB},
	author = {Sommer, S. G and Ostergard, H. S and Lofstrom, P and Andersen, H. V and Jensen, L. S}
}
