2018 Estimates of nitrogen deposition in Northern Ireland and import/export of N deposition across the UK.

Atmospheric nitrogen (N) deposition represents a significant threat to sensitive habitats and species in the United Kingdom, with excessive N supply leading to declines in many important species of high conservation value, at the expense of fast-growing species that can exploit the additional nitrogen supply. Atmospheric N deposition originates from emissions of ammonia (NH3, mainly from agricultural sources) and nitrogen oxides (NOx, mainly from transport, industry, power generation and other combustion sources). This short report aims to update the import and export estimates of atmospheric nitrogen to/from Northern Ireland by Carnell et al. (2020). More up to date estimates of N deposition to/from Northern Ireland 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). This report aims to quantify and compare N deposition to land in NI from sources within NI and beyond (in the UK, Republic of Ireland, Shipping and mainland Europe) to the amount of N deposition produced from NI sources that is deposited to the rest of the UK. Estimating the likely source of N deposition received by NI will enable policy makers to assess how effective national N mitigation measures are likely to be.