Mapping Ammonia Emissions and Concentrations for Switzerland — Effects on Lichen Vegetation

Abstract

This summary presents new maps of ammonia emissions and concentrations produced for Switzerland, as well as selected results of a study investigating the effect of ammonia on the vegetation of lichens. The mapping of ammonia was initiated in the early 1990s with the aim to calculate the deposition of nitrogen and subsequently the exceedance of critical loads of acidity and nutrient nitrogen in Switzerland with high spatial resolution (i.e. 1 × 1 km). In the first approach, ammonia emissions were mapped using livestock statistics spatially related to the municipalities and land-use maps (FOEFL 1994, 1996). Ecosystem-dependent depositions were directly calculated from the amount of ammonia emitted within a radius of 10 km. In this ‘budget’ model, the overall ratio of emission to deposition was constrained to a fixed value (45%). As systematic measurements of ammonia concentrations did not exist at that time, the results were checked mainly with deposition measurements (e.g. BUWAL 1994) and EMEP results. Later, the ammonia emission inventory was improved by using livestock statistics spatially related to the locations of farms, and the atmospheric dispersion of ammonia was modelled by an empirical function of concentration vs. distance with a spatial resolution of 1 ha. A good correlation was obtained between modelled and measured concentration values for 17 sites (Rihm and Kurz 2001). In 1999, a continuous ammonia monitoring program was started with more than 30 sites. It allowed to refine the method by adjusting the function (in the case of the emitting cell) so that an optimum correlation was obtained (Thoni et al. 2004). Since then the emission inventory was further improved using detailed livestock statistics (SFSO 2003), stratified emission factors for agricultural emissions (Reidy et al. 2007) and modelled ammonia emissions from traffic. In addition, the ammonia emissions in neighbouring countries were included (adjacent EMEP-grids).