Regional scale modelling of the concentration and deposition of oxidised and reduced nitrogen in the UK

The Fine Resolution Atmospheric Multi-pollutant Exchange model (FRAME) was applied to model the spatial distribution of air concentration and deposition of nitrogen (N) compounds between 1990 and 2005. Modelled wet deposition of N was found to decrease more slowly than the emissions reductions rate. This is attributed to a number of factors including increases in NOx emissions from international shipping and changing rates of atmospheric oxidation. The modelled deposition of NOy and NHx to the United Kingdom (UK) was estimated to fall by 52 % and 25 % between 1970 and 2020. The percentage of the UK surface area for which critical loads for sensitive ecosystems are exceeded was estimated to fall from 73–49 % for nutrient N deposition. Comparison with model simulations at 1 km and 5 km resolution demonstrated that fine scale simulations are important in order to spatially separate agricultural source regions from sink areas (nature reserves) for ammonia dry deposition.