Ground based in situ observations of filter_3pack at Villum Research Station, Station Nord (DK0010G). These measurements are gathered as a part of the following projects AMAP, 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), cadmium in aerosol (mass_concentration_of_cadmium_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), sodium in aerosol (mass_concentration_of_sodium_in_dry_aerosol_particles_in _air), sulphate_total in aerosol (mass_concentration_of_total_sulphateexpressed_as_sulphur_in_dry_aerosol_particles_in_air), sulphate_total in aerosol (mass_concentration_of_total_sulphateexpressed_as_sulphur_in_dry_aerosol_particles_in_air), sulphur_dioxide in air (mass_concentration_of_sulphur_dioxide_expressed_as_sulphur_in_air)