Atmospheric modelling data for Scottish nitrogen balance sheet

This short report aims to update the atmospheric nitrogen budgets for Scotland presented in Carnell et al. (2019). The atmospheric nitrogen (N) estimates presented in the 2019 report were based on FRAME source attribution model output for the emission year 2012 (Bealey and Dore 2017), which was the most recent dataset at the time of writing. Although more up to date estimates of N deposition existed in early 2019 (when the SEPA report was written), the source attribution dataset (for the emission year 2012) was the most up to date dataset providing estimates of N deposition by source type. As a result the source attribution output was scaled to more recent CBED model estimates (for the years 2013 – 2015, Smith et al. 2018) in the Carnell et al. (2019) report, to reflect any changes in emissions and subsequent N deposition. This new report for the Scottish Government compares source attribution model outputs for the years 2012 and 2018 respectively, rather than the scaled dataset used in Carnell et al 2019. Improved estimates of N deposition to/from Scotland now exist for the emission year 2018, which were developed under the Air Pollution Information System (APIS http://www.apis.ac.uk/) project and funded by the UK government agencies (SEPA, SNH, JNCC, EA, NE, NRW, NIEA). In addition to updated emission estimates used as model input, the model has also been updated substantially, with important developments including the differentiation of deposition from sources within the Republic of Ireland, which were previously included with European sources. More recent model input data (such as improved land cover estimates and meteorology) were also used in this work which better reflect the present.