This dataset is from the Northern Ireland (NI) DELTA® Gas and Aerosol Monitoring Network, and consists of monthly atmospheric concentrations of inorganic, water-soluble, reactive gases and aerosols measured with the UKCEH DELTA® method at 4 sites across NI for the years 2019 to 2020. • Gases: ammonia (NH3), nitric acid (HNO3), sulphur dioxide (SO2) • Aerosols: ammonium (NH4+), nitrate (NO3-), sulphate (SO42-), chloride (Cl-), sodium (Na+), calcium (Ca2+), Magnesium (Mg2+) The network is operated jointly by Agri-Food and Biosciences Institute (AFBI) and the UK Centre for Ecology & Hydrology (UKCEH), and funded by the Department of Agriculture, Environment and Rural Affairs (DAERA), Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/55ad7cf8-fc40-4b8a-9d35-ce970a915ff6

This dataset is from the Northern Ireland (NI) ALPHA® Ammonia Monitoring network, and consists of monthly concentrations of atmospheric ammonia (NH3) gas measured with the UKCEH ALPHA® method at 25 sites across NI for the years 2019 to 2020. NH3 data were also collected with a monthly measurement frequency with the UKCEH DELTA® method at a further 4 sites, as part of the NI DELTA® Gas and Aerosol Monitoring Network. At one site, ALPHA® and DELTA® methods were co-located to inter-compare NH3 concentrations. Monthly NH3 data (2019 – 2020) from the NI DELTA® network are reported separately in a companion submission. The network is operated jointly by Agri-Food and Biosciences Institute (AFBI) and the UK Centre for Ecology & Hydrology (UKCEH), and funded by the Department of Agriculture, Environment and Rural Affairs (DAERA), Northern Ireland. Full details about this dataset can be found at https://doi.org/10.5285/7d380209-9df4-4686-b7ad-de39cca19cce