Atmospheric behaviour of ammonia and ammonium

1.4.1 Scope of this thesisA few models for ammonia and ammonium exist. Russell et al. (1983) made a multi-layer Lagrangian transport model describing the transport and formation of ammonium nitrate aerosol for California. They did not take reactions of ammonia and sulphuric acid into account, nor wet deposition. Their model was mainly used to compute diurnal variations of ammonium nitrate aerosol, ammonia and nitric acid concentrations, which were compared with measurements for one day.De Leeuw et al. (1986) developed a multi-layer Lagrangian transport model with detailed chemistry including the reaction with sulphuric acid containing aerosol and wet deposition. Their model was especially designed to describe episodes with high aerosol concentrations.More complicated models as discussed above have the advantage of giving more insight in detailed (chemical) mechanisms. But the results obtained with such models are often difficult to verify as components are involved which are not measured, or not at all levels the model gives results for. Moreover, more complicated models require relatively more computing time, which makes them less suitable to compute long-term average concentrations. At this moment no good information is available on seasonal variations in the ammonia emission. Moreover, much Information on the variation both in time and space of other processes is also lacking. This means that some processes involved can be described in detail, whereas others cannot. Such models suffer then from an imbalance in the treatment of different processes, and the results of the models will be no better than is dictated by the weakest link in the chain. It should be mentioned here that such models still can be very valuable to study mechanisms and possible interactions between different processes and components. But because of the lacking information on e.g. short-time variation in emission no realistic short-term concentrations can be obtained.Some information on the processes involved is available, but sometimes only on a yearly basis. It seems therefore most appropriate to integrate the existing knowledge by using a relatively simple model for the computation of yearly averaged concentrations. A first attempt to do this was made by Fisher (1984). He tried to compute deposition fields for ammonium in precipitation and the total deposition (sum of dry and wet deposition) of NHx (sum of ammonia and ammonium) for Europe. But he had to conclude that his approach would remain limited until the main rates of removal of nitrogen compounds were better known.The scope of this thesis is:a. To evaluate the existing knowledge of all processes involved.b. To acquire additional crucial information on some processes from own field measurements.c. To integrate this knowledge by applying a model for the computation of long-term average (ground level) concentrations, with emphasis on the European scale. This model has been developed especially for ammonia and ammonium.d. To show some new applications of models: computation of historical import/export balances and concentration patterns.1.4.2. On the presentationThis thesis consists mainly of separate articles (chapters 3 to 6) which were submitted to Atmospheric Environment. This has some consequences:a. Some information is presented in more than one article or part of this thesis.b. A list of references appears after each chapter.c. The articles have not been written at the same time. As a result some information was not yet known at the time of preparation of some articles, although this does not lead to any serious inconsequences.In the following a preview is given of the contents of the different chapters.Chapter 2In this chapter some information is presented on the geographical distribution of the yearly averaged ammonia emission in Europe, which is essential to understand the model results. Chapter 3In this chapter field measurements are described. These measurements were performed for the following purposes:a. To verify the estimated emission densityb. To get an indication on the vertical concentration profiles of ammonia, ammonium and related components In an area where emission occurs. This information is needed to model the horizontal transport.c. To get an indication of the overall conversion rate of ammonia to ammonium.Chapter 4In this chapter is described how correction factors can be computed which can be used in a simple Lagrangian long-range transport model to describe the effects of turbulent mixing on concentration and deposition patterns. By using these correction factors more realistic results can be obtained.Chapter 5This chapter forms the basic part of the thesis and describes the evaluation and integration of the present knowledge, the setup of the model, numerical aspects of the model and comparison of model results with measurements. Although the model in principle would allow to vary most parameters as a function of time and space (e.g. dry deposition velocity, reaction rate, mixing height etc.) this was not done in practice in view of all uncertainties in the parameter values. Therefore, also no processes like escape into the reservoir layer were taken into account.Chapter 6In this chapter it is shown that it is not only possible to use a model to describe the present situation, but also to give estimates of concentrations in the past. These estimates make it possible to know where trends in concentrations measured in the past can be expected.Chapter 7In this chapter the conclusions of this study are summarized and discussed

A Simplified Model of Nitrogen Flows from Manure Management

This report describes a model to simulate release processes of trace gases from manure into the atmosphere. This "manure handling model" (MHM) provides a mass-consistent scheme to follow nitrogen and carbon compounds along the typical stages of manure treatment in animal husbandry. In each of the model compartments, which reflect the respective stages, conversion between reactive and unreactive nitrogen or carbon species is possible, as well as the release of gaseous compounds from the reactive species. We use total ammoniacal nitrogen (TAN) as the reactive nitrogen species, and degradable volatile solid (VSd) as the reactive carbon species. Conversion parameters, either derived from specific information, e.g. national data, or as default values, allow assessing transformation rates. As a result, the model generates emission factors for the release of nitrogen components (gaseous NH3, N2O, NOx, N2 and NO3 -- in runoff and the associated N2O emission) and CH4 for use in IIASA's integrated assessment model GAINS. Results of MHM have been compared with the German emission model GAS-EM for dairy cattle on liquid manure to demonstrate that the simplified model is able to reflect complex national information. With identical input parameters, the simplified model reproduces results of the more complex models within 1% difference for the emission of all N components and emission of CH4. MHM was also used with default input (excretion rates, emission coefficients and removal factors) to generate emission factors for all possible combinations of animals and control strategies for all European countries. However, a comparison with current GAINS emission factors reveals substantial differences due to country-specific information that is available in GAINS

Integrated Nitrogen Management in China

Providing China's growing population with higher quality food and a larger share of meat in diets can only be accomplished through increased agricultural productivity, which is usually achieved through higher input of nitrogen to soils. This can lead to nitrate leaching which affects the quality of drinking water, causes emissions of ammonia to the atmosphere, a contributor to the formation of atmospheric particles that are harmful to human health, and to the release of nitrous oxide (N2O), an important global greenhouse gas. This report develops an integrated perspective on agricultural management measures that have multiple benefits on economic development, on the local environment and for global greenhouse gas emissions. The study estimates for the case of China that an integrated nitrogen management approach could increase agricultural production by up to 50 percent while keeping current levels of nitrogen discharge to soil, water and air at the local scale. Compared to the business as usual case, emissions of N2O greenhouse gas emissions would be 25 percent lower. Developed as an activity of IIASA's interdisciplinary Greenhouse Gas Initiative (GGI), the new integrated approach links population increase and demands on food quality with nitrogen fertilizer requiremnts in agriculture, and assesses undesired environmental effects of nitrogen at the local and global scales

Integrated assessment of air pollution and greenhouse gases mitigation in Europe

Paper discusses integrated assessment methodology of air pollution and greenhouse gases mitigation. RAINS/GAINS model developed at the International Institute for Applied Systems Analysis (IIASA) is described. Its use in policy-relevant analysis is discussed with particular focus on studies for the development of policies of the European Union and under the UN/ECE Convention on Long-Range Transboundary Air Pollution (CLRTAP). Importance of interactions and synergies between air pollution and greenhouse gases policies is stressed. Integrated assessment has proven to be an important tool for preparation of air pollution control legislation in Europe. Although most prominent applications of integrated assessment referred to international policies, recently these methods have been applied in several national studies for in-depth analyses at sub-national regional level. It is advisable to further disseminate applications of the methodology and software tools for regional assessment