Ground based in situ observations of CEH_denuder at Lough Navar (GB0006R). These measurements are gathered as a part of the following projects CAMP, EMEP and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: ammonia in air (mass_concentration_of_ammonia_expressed_as_nitrogen_in_air), ammonium in aerosol (mass_concentration_of_ammonium_expressed_as_nitrogen_in_dry_aerosol_particles_in _air), ammonium in aerosol (mass_concentration_of_ammonium_in_dry_aerosol_particles_in _air), nitrate in aerosol (mass_concentration_of_nitrate_expressed_as_nitrogen_in_dry_aerosol_particles_in _air), nitrate in aerosol (mass_concentration_of_nitrate_in_dry_aerosol_particles_in _air), nitric_acid in air (mass_concentration_of_nitric_acid_expressed_as_nitrogen_in_air), sum_ammonia_and_ammonium in air+aerosol, sum_nitric_acid_and_nitrate in air+aerosol